{"id":3451,"date":"2020-10-12T20:20:16","date_gmt":"2020-10-12T20:20:16","guid":{"rendered":"http:\/\/dreambody.clinic\/?page_id=3451"},"modified":"2020-10-12T20:22:00","modified_gmt":"2020-10-12T20:22:00","slug":"stem-cells-in-the-treatment-of-diabetes-mellitus-focus-on-mesenchymal-stem-cells","status":"publish","type":"page","link":"https:\/\/dreambody.clinic\/demo\/stem-cells-in-the-treatment-of-diabetes-mellitus-focus-on-mesenchymal-stem-cells\/","title":{"rendered":"Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem cells"},"content":{"rendered":"\n<p><strong>Stem cells in the treatment of diabetes mellitus \u2013 focus on<br>mesenchymal stem cells<\/strong><\/p>\n\n\n\n<p><div class=\"wp-block-pdfemb-pdf-embedder-viewer\"><a href=\"https:\/\/dreambody.clinic\/wp-content\/uploads\/2020\/10\/Stem-cells-in-the-treatment-of-diabetes-mellitus.pdf\" class=\"pdfemb-viewer\" style=\"\" data-width=\"max\" data-height=\"max\" data-toolbar=\"bottom\" data-toolbar-fixed=\"off\">Stem cells in the treatment of diabetes mellitus<\/a><\/div><br><strong>Stem cells in the treatment of diabetes mellitus \u2013 focus on<br>mesenchymal stem cells<\/strong> &#8211; G\u00fcnter P\u00e4th, Nikolaos Perakakis, Christos S. Mantzoros, Jochen<br>Seufert<br>PII: S0026-0495(18)30215-4<br>DOI: doi:10.1016\/j.metabol.2018.10.005<br>Reference: YMETA 53824<br>To appear in: Metabolism<br>Received date: 10 August 2018<br>Accepted date: 14 October 2018<br>Please cite this article as: G\u00fcnter P\u00e4th, Nikolaos Perakakis, Christos S. Mantzoros, Jochen<br>Seufert , Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem<br>cells. Ymeta (2018), doi:10.1016\/j.metabol.2018.10.005<br>This is a PDF file of an unedited manuscript that has been accepted for publication. As<br>a service to our customers we are providing this early version of the manuscript. The<br>manuscript will undergo copyediting, typesetting, and review of the resulting proof before<br>it is published in its final form. Please note that during the production process errors may<br>be discovered which could affect the content, and all legal disclaimers that apply to the<br>journal pertain.<br>ACCEPTED MANUSCRIPT<br>1<br>Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem cells<br>G\u00fcnter P\u00e4th1*, Nikolaos Perakakis2, Christos S. Mantzoros2, Jochen Seufert1<br>1 Division of Endocrinology and Diabetology, Department of Medicine II, Medical Center \u2013<br>University of Freiburg, Faculty of Medicine, University of Freiburg, Germany<br>2 Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine,<br>Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>Corresponding author<br>G\u00fcnter P\u00e4th, PhD<br>Division of Endocrinology and Diabetology<br>Department of Medicine II<br>Medical Center \u2013 University of Freiburg<br>Faculty of Medicine, University of Freiburg<br>Hugstetter Str. 55<br>79106 Freiburg<br>GERMANY<br>Tel.: +49 761 270 73270<br>Fax: +49 761 270 33720<br>E-mail: guenter.paeth@uniklinik-freiburg.de<br>Keywords<br>Stem cells, diabetes mellitus, transplantation, embryonic stem cells, induced pluripotent stem<br>cells, mesenchymal stromal cells<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>2<br>Abbreviations<br>ADA, American Diabetes Association; AE, adverse event; \u03b1-SMA, alpha smooth muscle<br>actin; ANXA1, annexin-1; AUC, area under the curve; BAD, Bcl-2 antagonist of cell death;<br>Bcl-2b, B-cell lymphoma 2; bFGF, basic fibroblast growth factor; BM, bone marrow; BMI,<br>body mass index; CAR cell, CXCL12-abundant reticular cell; CCL5\/RANTES, CCchemokine<br>ligand 5; CD, cluster of differentiation; CFU-F, colony forming unit-fibroblast;<br>CXCL12, CXC chemokine ligand 12; DC, dendritic cell; Ebf, early B-cell factor; ECM,<br>extracellular matrix; EMT, epithelial to mesenchymal transition; ERK, extracellular signalregulated<br>kinases; ESC, embryonic stem cells; FDA, Food and Drug Administration; FGFR1,<br>fibroblast growth factor receptor 1; GAD, glutamic acid decarboxylase; GCV, ganciclovir;<br>GM-CSF, granulocyte-macrophage colony-stimulating factor; GSIS, glucose-stimulated<br>insulin secretion; GVHD, graft-versus-host disease; HbA1c, glycated hemoglobin A1c; HGF,<br>hepatocyte growth factor; HLA, human leukocyte antigen; HNF1A, hepatocyte nuclear factor<br>1\u03b1; HOMA, homeostasis model assessment; HSC, hematopoietic stem cells; HSV-Tk, herpes<br>simplex virus thymidine kinase; ICAM1, intercellular adhesion molecule 1; ICOS, inducible<br>costimulator; IDDM, insulin-dependent diabetes mellitus; IDO, indoleamine 2,3-dioxygnase;<br>IGF, insulin-like growth factor; IL, interleukin; IL-1RA, interleukin-1 receptor antagonist;<br>IPF-1, insulin promoter factor 1 (official name, PDX1); IR, insulin resistance; iPSC, induced<br>pluripotent stem cells; ISC, insulin screting cell; ISL-1, insulin gene enhancer protein 1; IU,<br>international unit; IV, intravenous; MET, mesenchymal to epithelial transition; MHC, major<br>histocompatibility complex; MMP, matrix metalloproteases; MMTT, mixed-meal tolerance<br>test; MNC, mononuclear cells; MODY3, maturity-onset diabetes of the young type 3; MPC,<br>mesenchymal precursor cells; MSC, mesenchymal stem cells; NG2, neural\/glial antigen 2;<br>NGF, nerve growth factor; NGN3 neurogenin 3; NKX6.1, NK6 homeobox 1; NO, nitric<br>oxide; NOD, non-obese diabetic; NSG, NOD scid gamma; PAX, paired box protein; PDGF,<br>platelet-derived growth factor; PD-L1, programmed cell death ligand 1; PDX1, pancreatic and<br>duodenal homeobox 1; PEDF, pigment epithelium-derived factor; PGE2, Prostaglandin E2;<br>SC, stem cells; SCF, stem cell factor; SCID, severe combined immunodeficiency; STZ,<br>streptozotocin; T1DM, type 1 diabetes mellitus; T2DM, type 2 diabetes mellitus; TGF,<br>transforming growth factor; Th, T helper; TNF, tumour necrosis factor; TRAIL, TNF-related<br>apoptosis inducing ligand; Treg, regulatory T cell; TSG-6, tumour necrosis factor-stimulated<br>gene 6; TUNEL, terminal deoxynucleotidyl transferase mediated dUTP nick end labeling;<br>UC, umbilical cord; VCAM1, vascular cell adhesion molecule 1; VEGF, vascular endothelial<br>growth factor; WHO, world health organisation; WJ, Wharton&#8217;s Jelly.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>3<br>Abstract<br>Diabetes mellitus type 1 and type 2 have become a global epidemic with dramatically<br>increasing incidences. Poorly controlled diabetes is associated with severe life-threatening<br>complications. Beside traditional treatment with insulin and oral anti-diabetic drugs, clinicians<br>try to improve patient&#8217;s care by cell therapies using embryonic stem cells (ESC), induced<br>pluripotent stem cells (iPSC) and adult mesenchymal stem cells (MSC). ESC display a<br>virtually unlimited plasticity, including the differentiation into insulin producing \u03b2-cells, but<br>they raise ethical concerns and bear, like iPSC, the risk of tumours. IPSC may further inherit<br>somatic mutations and remaining somatic transcriptional memory upon incomplete reprogramming,<br>but allow the generation of patient\/disease-specific cell lines. MSC avoid such<br>issues but have not been successfully differentiated into \u03b2-cells. Instead, MSC and their<br>pericyte phenotypes outside the bone marrow have been recognized to secrete numerous<br>immunomodulatory and tissue regenerative factors. On this account, the term &#8216;medicinal<br>signaling cells&#8217; has been proposed to define the new conception of a &#8216;drug store&#8217; for injured<br>tissues and to stay with the MSC nomenclature. This review presents the biological<br>background and the resulting clinical potential and limitations of ESC, iPSC and MSC, and<br>summarizes the current status quo of cell therapeutic concepts and trials.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>4<br>Introduction<br>Human organs and tissues possess a limited capacity to completely recover their structure and<br>function in a number of pathologic conditions and degenerative diseases. This fact initiated<br>the multidisciplinary field of regenerative medicine which investigates the potential of stem<br>cells (SC) for tissue repair and restoration of organ function. Based on their nature and origin,<br>SC exhibit features of interest for cell therapies; e.g. targeting functional degeneration and<br>loss of insulin producing pancreatic \u03b2-cells in diabetes mellitus (DM). The diverse potential of<br>embryonic SC (ESC), induced pluripotent SC (iPSC) and adult mesenchymal SC (MSC) has<br>been exploited to restore or maintain insulin secretion as well as to investigate patient-specific<br>disease aspects. MSC are currently the most investigated cells in DM-related trials while<br>clinical testing of ESC has just started. This review summarizes the biological aspects and the<br>application strategies for the treatment of DM by stem cell therapy.<br>\u03b2-cell replacement<br>Patients with autoimmune DM type 1 (T1DM) experience a loss of insulin producing<br>pancreatic \u03b2-cells and rely on daily insulin injections. Despite modern insulin therapies,<br>exogenous application of insulin can never be as accurate and dynamic like insulin secretion<br>from endogenous \u03b2-cells and therefore can only partially reduce the risk for the development<br>of micro- (i.e. nephropathy, retinopathy) or macrovascular (i.e. coronary artery disease,<br>peripheral artery disease, cerebrovascular disease) complications. Additionally, efforts to<br>develop effective immunosuppressive treatments to prevent \u03b2-cell loss before disease onset<br>had limited success so far [1]. Consequently, restoration of endogenous insulin secretion<br>represents an important aim to prevent hyper- and hypoglycemia as well as to reduce or avoid<br>diabetic complications and the patient&#8217;s requirement for self-management of glycemic control<br>by exogenous insulin administration.<br>Clinical islet transplantation aims to re-establish endogenous insulin secretion and has been<br>steadily refined since its beginning in the 1980s [2]. An important step was the &#8216;Edmonton<br>Protocol&#8217; from 1999 which avoids \u03b2-cell toxic glucocorticoids by using sirolimus, tacrolimus<br>and daclizumab for immunosuppression [3]. Ongoing clinical research improved isolation,<br>culture and transplant techniques, and evaluated advanced anti-inflammatory and<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>5<br>immunomodulatory interventions [4-6]. As a result, a multicenter analysis with 18 diabetic<br>patients receiving 34 islet transplantations showed a graft survival (defined by C-peptide<br>concentrations of \u2265 0.3 ng\/ml) of about 72.2%, 44.4% and 22.2% after 1, 2 and 5 years,<br>respectively [7]. Subsequently, a multicenter phase 3 trial, which enrolled 48 participants<br>receiving 75 islet transplantations, successfully improved glycemic control to a median<br>glycated hemoglobin A1c (HbA1c) level of 5.6% after 1 and 2 years [8]. Compared to<br>standard insulin therapy, islet transplantation more efficiently improved glycemic control and<br>progression of retinopathy, and resolved hypoglycemia even in patients with only partially<br>remaining graft function [9, 10].<br>Transplantation of whole pancreases is an established alternative to islets and both procedures<br>display advantages and limitations [11]. The standard procedure of islet infusion into the liver<br>is much safer with less complications than pancreas transplantation which is considered a<br>major surgery with accordingly enhanced risks for the patient. Thus, pancreas transplantation<br>is rarely performed alone and is most commonly combined with a kidney transplantation in<br>patients with T1DM and end-stage renal disease. The major obstacle of the less risky islet<br>transplantation is the limited graft survival. Insulin independence after islet transplantation<br>initially reached barely 10% at 1 year but has been improved by the Edmonton protocol to 10-<br>15% at 5 years [12] and by later developments, such as T cell-depleting agents and blockade<br>of tumour necrosis factor (TNF), to 50% at 5 years [4]. Thereby, at least experienced islet<br>transplantation centers have substantially improved long-term graft function towards the<br>reported 5 year outcomes in pancreas transplantation; 55% for pancreas alone and after<br>kidney, and 72% for pancreas together with kidney [2, 13].<br>As with other organ transplantation, there is a great scarcity of human donor material which<br>evoked intensive research on the generation of insulin producing \u03b2-cells from SC. Whole<br>pancreas transplantation strictly depends on high quality organs while generation of insulin<br>producing \u03b2-cells from SC has the potential to solve the problem of limited availability of<br>donor material for islet transplantation. However, the need for immunosuppression reserves<br>both pancreas and islet transplantation as a therapeutic choice to a limited patient population<br>such as brittle diabetics with life-threatening hypoglycemic events or subjects who anyway<br>receive immunosuppression; e.g. because of kidney transplantations for renal failure due to<br>diabetic nephropathy.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>6<br>I. ESC<br>ESC represent the inner cell mass of the blastocyst and possess a pluripotent differentiation<br>capacity. This makes them capable to form all three germ layers (ectoderm, endoderm and<br>mesoderm) which subsequently give rise to all cell types of the body. On this account, these<br>cells are considered the superior tool for tissue generation but they evoke ethical concerns<br>regarding their origin from human embryos. Moreover, they bear a clinical risk since their<br>pluripotent nature makes undifferentiated ESC capable to form teratomas and malignant<br>teratocarcinomas in vivo. The development of clinically safe differentiation protocols and<br>testing routines for tumorigenicity in rodents represents an important challenge in the field<br>[14, 15].<br>The differentiation of human ESC into functional \u03b2-cells is not trivial since transforming<br>processes have to mimic complex embryonal organogenesis in vitro. Differentiation protocols<br>therefore established a number of factors and inhibitors that modulate molecular pathways in<br>an exact sequential timing to resemble the natural development of pancreatic \u03b2-cells.<br>Generally, human ESC were firstly differentiated into definitive endoderm cells and then<br>sequentially into primitive gut tube and posterior foregut, pancreatic endoderm and finally \u03b2-<br>cells using multiple specified media and supplementation in each step [16, 17]. The earlier<br>attempts proved the concept but did not achieve high yields; e.g. a typical early study resulted<br>in an average percentage of insulin+ cells in differentiated human ESC cultures of 7.3% [16].<br>Meanwhile, the exact media compositions have been further improved and current protocols<br>reached the level of scalable production of \u03b2-cell phenotypes with functional insulin secretion<br>[17-20]. However, the complexity of protocols and differences in employed ESC and iPSC<br>lines raise difficulties in reproducibility outside experienced laboratories since stem cell<br>differentiation is despite all progress not a routine procedure.<br>A major step in differentiation of human ESC towards \u03b2-cells is the expression of the<br>transcription factors pancreatic and duodenal homeobox 1 (PDX1) and NK6 homeobox 1<br>(NKX6.1) which are markers of pancreatic endoderm and endocrine precursor cells. It has<br>been shown that comparable human embryonic pancreas tissue from fetal weeks 6-9, which<br>contained very few \u03b2-cells at that stage, is capable to mature into functional \u03b2-cells after<br>transplantation into non-obese diabetic mice with severe combined immunodeficiency<br>(NOD\/SCID mice) [21]. Based on these findings, in vivo maturation of PDX1+\/NKX6.1+<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>7<br>progenitors into \u03b2-cells has been recognized to be more efficient than mimicking this monthslong<br>process in vitro [22]. Furthermore, scalable in vitro differentiation of ESC into endocrine<br>pancreatic precursor cells is to date more robust and less complicated [23, 24] than generation<br>of fully functional \u03b2-cell phenotypes by advanced protocols [17, 19] and therefore the<br>favoured strategy of the company ViaCyte [25].<br>The resulting improvements in differentiation of ESC towards PDX1+\/NKX6.1+ pancreatic<br>progenitors during the last decade have also reduced the risk of tumour formation in vivo<br>which occurred in a typically early study of the company NovoCell (name changed to<br>ViaCyte in 2010) with a rate of 7 out of 46 transplanted mice [22]. Since then, ViaCyte has<br>steadily optimized the approach to efficient large-scale production and embedded their<br>pancreatic endoderm and endocrine progenitor cells into a macroencapsulation device to<br>generate immune isolated VC-01 implants [18, 25, 26].<br>Macroencapsulation improved graft survival and clinical safety. Although ESC-derived<br>progenitors are hypoimmunogenic, transplanted cells are challenged by adaptive immune<br>responses such as local inflammation and rejection. In addition, once maturated into insulin<br>producing \u03b2-cells, graft cells will be attacked by persistent autoreactive T cells in patients<br>with T1DM. Several studies have demonstrated that macroencapsulation protects embedded<br>cells by isolation from immune responses and thereby avoids rejection and the need for<br>immunosuppression [27, 28]. Furthermore, macroencapsulation prevents escape of embedded<br>cells into the body. This is an important safety issue since any ESC transplanted in an<br>undifferentiated state bears the potential of malignant transformation. In this view,<br>subcutaneously transplanted devices could be retrieved and removed easily. Using this<br>concept, Viacyte has achieved a milestone by initiating the first-in-man clinical trial to test<br>safety and efficacy of their pancreatic endoderm implant VC-01 in patients with T1DM and<br>hypoglycemic unawareness (ClinicalTrials.gov: NCT02239354, currently enrolling patients,<br>estimated completion in January 2021).<br>This trial will answer the question whether the established in vivo maturation of human ESCderived<br>PDX1+\/NKX6.1+ progenitors in rodents can be comparably recapitulated in human<br>subjects. In addition, two of three further trials initiated by Viacyte aim to test a modified<br>implantation device with reduced immuno isolation that allows vascularisation of the<br>macroencapsulated cells. Provided that outcome of all these trials will prove safety, efficacy<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>8<br>and significant long-term graft function, this approach holds the potential to pave the way<br>towards clinical \u03b2-cell replacement without immunosuppression and independent of the<br>limited availability of donor islets.<br>II. iPSC<br>The ethical criticism related to the use of human pre-implantation embryos for extraction of<br>ESC inspired researchers to refine the work of John B. Gurdon. His key study demonstrated<br>that enucleated Xenopus laevis eggs that were transplanted with nuclei from differentiated<br>intestinal epithelium could, at least in small numbers, develop into living tadpoles [29]. This<br>demonstrated for the first time that somatic cell nuclei have the potential to revert into a<br>pluripotent state. Decades passed by before this finding gained broad acceptance in the<br>scientific community and the progression of this idea culminated in the birth of the first<br>mammal, clone sheep Dolly, on July 5, 1996 [30].<br>Gurdons basic concept of reprogrammable somatic cells was further developed and one<br>decade after Dolly&#8217;s birth, Takahashi and Yamanaka induced embryonic-like pluripotency in<br>somatic mouse fibroblasts by viral overexpression of the four transcription factors Sox2,<br>Oct4, Klf4 and c-Myc [31]. For their groundbreaking discoveries Gurdon and Yamanaka were<br>honored by the Noble Prize in 2012 (www.nobelprize.org).<br>As a major achievement, iPSC overcome the ethic obstacle of using embryos for harvest of<br>ESC. During ongoing research, the original Yamanaka protocol has been diversely modified<br>and viral integration was effectively replaced by treatment with recombinant proteins, small<br>molecules and microRNAs [32, 33]. Following the principle route of pancreatic development<br>as used for ESC, researchers have successfully differentiated iPSC into functional \u03b2-cell<br>phenotypes [34, 35] and also established scalable production of both endocrine pancreatic<br>progenitors and \u03b2-cells [20, 36].<br>Nevertheless, further refinement of procedures is still an issue and new tools were created for<br>the identification of compounds and conditions which enhance yield and functionality of<br>generated \u03b2-cells. For example, human iPSC expressing the fluorescent reporters Venus and<br>mCherry markers under the control of intrinsic neurogenin 3 and insulin promoters have been<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>9<br>generated for screening of differentiation efficiency [37]. These cells have served to identify<br>an inhibitor of fibroblast growth factor receptor 1 (FGFR1) that, while blocking the early<br>development of pancreatic progenitors, promoted the terminal differentiation of pancreatic<br>endocrine progenitors into endocrine cells including \u03b2-cells.<br>However, due to their origin from adult somatic cells, iPSC can inherit somatic mutations and<br>incomplete reprogramming can maintain somatic transcriptional memory including cancer<br>associated gene activity [38, 39]. These dangers currently do not define them as the first<br>choice for clinical use but, more importantly, iPSC enable the successful generation of<br>patient-specific cell phenotypes that allow to recapitulate disease processes in vitro and can<br>serve as platforms for drug development and testing [40-42]. For example, researchers<br>successfully generated an iPSC line from a patient carrying a hepatocyte nuclear factor 1\u03b1<br>(HNF1A) mutation resulting in maturity-onset diabetes of the young type 3 (MODY3). In the<br>near future, patient-specific cell lines will help to develop disease-related models that<br>overcome the obstacle of species differences between human subjects and animal models.<br>III. MSC<br>For an excellent graphical overview on MSC biology discussed in section III we recommend<br>the poster by Somoza et al. [43].<br>MSC within the bone marrow (BM)<br>The discovery of MSC has been generally attributed to A. J. Friedenstein who observed that<br>BM explants form plastic adherent fibroblast-like clonogenic cells with a high replicative<br>capacity in vitro and named them colony forming unit-fibroblasts (CFU-F) [44]. Friedenstein<br>et al. further figured out that culture expanded CFU-F are capable to differentiate into<br>osteoblasts, chondrocytes and adipocytes, and to reconstitute a hematopoietic<br>microenvironment after transplantation in irradiated mice [45, 46]. These findings supported<br>the pioneering study of Tavassoli and Crosby who demonstrated that autologous BM<br>fragments transplanted into extramedullary sites can reconstitute hematopoietic and<br>adventitial structures in rats [47]. The observed process started from a developing network of<br>proliferating reticular cells and was successively followed by the occurrence of osteoblasts,<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>10<br>osteoid tissue, endothelial layers of sinusoidal structure and finally hematopoietic repopulation.<br>These findings pointed out that CFU-F include a group of cells with the capacity of<br>multipotent differentiation into mesenchymal lineages. Based on these features, multipotent<br>CFU-F were renamed &#8216;mesenchymal stem cells&#8217; by A. I. Caplan in 1991 [48]. Caplan later<br>commented that the term &#8216;stem cell&#8217; was provocative at that time but justified by ongoing<br>research displaying that CFU-F could generate bone, cartilage, fat, muscle and other<br>mesodermal phenotypes in vitro [49]. Postnatally, the contribution of BM-MSC to bone<br>formation is associated with declining numbers of MSC after birth as indicated by the 10fold<br>drop of CFU-F colony numbers in BM obtained from newborn and skeletally developed<br>teenaged donors and a steady further decline with aging [50].<br>Thus, bone formation was considered a core function of BM-MSC in vivo and their<br>osteogenic potential has been investigated in further detail by using scaffolds. As an example,<br>porous calcium phosphate ceramic cubes of 3 mm in size were loaded with BM-MSC<br>expressing the genetic marker lacZ and then subcutaneously transplanted into<br>immunodeficient mice [51]. The MSC monolayers formed osteoblasts, then the scaffold<br>became vascularized by host vessels and mineralized osteocytes developed. Importantly,<br>lacZ+ osteoblasts and osteocytes confirmed that new bone was formed by donor MSC.<br>Testings of this approach in animals and clinical settings showed that transplanted porous<br>scaffolds loaded with BM-MSC significantly contributed to bone repair in rodents and in<br>patients with large bone defects [52, 53].<br>The cube experiments further demonstrated that lacZ+ cells also occur around blood vessels<br>[51]. In support, cultured CFU-F express the same markers [e.g. cluster of differentiation<br>(CD) 146] as adventitial reticular cells of sinusoids in the intact BM in vivo [54].<br>Consequently, BM-MSC which do not undergo osteogenic differentiation reside at the<br>abluminal surface of endothelial cells. After subcutaneous transplantation, cells sorted for<br>CD146 were capable to organize a hematopoietic microenvironment outside the BM. This<br>confirmed that skeletal progenitors are a functional part of the hematopoietic stem cell (HSC)<br>niche and form a specialized microenvironment as conceptually already conceived by R.<br>Schofield in 1978 [55]. The use of culture expanded BM-MSC to improve outcomes of BM<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>11<br>transplantation in cancer patients after chemo-therapy was tested first-in-man in 1995 and was<br>clinically successful and safe [56].<br>Lineage tracing, using nestin (Nes)- or leptin receptor (LepR) promoter driven expression of<br>the fluorescence reporters GFP or tdTomato, was employed to further investigate MSCrelated<br>cell fates in the BM [57, 58]. One should keep in mind that characterization of BM<br>lineages is complicated since marker expression like that of Nes-GFP is in part variable<br>during cellular development and overlapping between distinct phenotypes. Besides Nes and<br>LepR gene activation, the in situ localization of MSC in the BM has been mainly defined by<br>the differential expression of CD146, CD271, neural\/glial antigen 2 (NG2) and alpha smooth<br>muscle actin (\u03b1-SMA). Resulting findings indicated the existence of three different MSC<br>populations within the endosteal niche and the perivascular niches at arterioles and sinusoids.<br>These investigations disclosed that Nes+ MSC of the endosteal niche secrete factors or<br>express cell surface molecules that regulate quiescence in nearby HSC [59, 60]. Nes+ MSC in<br>the perivascular niches express the key niche factors CXC chemokine ligand 12 (CXCL12),<br>therefore also called CXCL12-abundant reticular (CAR) cells, and stem cell factor (SCF)<br>which both control retention and maintenance of HSC [57]. The perivascular MSC could be<br>divided in rare periarteriolar NG2+ cells with high nestin expression (Nesbright\/NG2+) and<br>abundant perisinusoidal LepR+ cells with low nestin expression (Nesdim\/Lepr+). Deletion of<br>Cxcl12 and Scf in Nes+ MSC results in the mobilization of HSC to extramedullary organs and<br>a marked reduction of HSCs in the BM [57, 61, 62]. Notably, the secretion of CXCL12 is in<br>part regulated by direct innervation of the sympathetic nervous system and modulated by<br>circadian rhythms [63].<br>The very low numbers of CFU-F in BM of adult human donors points out that BM-MSC are a<br>minor population [50]. In line with this, it was found that among BM-MSC &#8216;abundant&#8217;<br>CAR\/LepR+ cells account for only 0.3% of mouse BM cells [64]. This small population is the<br>major source of adipocytes and osteoblasts in adult mouse BM but most of these cells<br>remained undifferentiated to maintain the hematopoietic niche. The underlying molecular<br>regulation was unclear until recently Seike et al. found that CAR\/LepR+ cells preferentially<br>express early B-cell factor (Ebf) 3 and analyzed its function [65]. Deletion of Ebf3 in<br>CAR\/LepR+ cells severly impaired HSC niche function and BM became osteosclerotic with<br>increased bone in aged mice. Additional deletion of Ebf1 further increased niche dysfunction<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>12<br>leading to depletion of HSC already in infant marrow. This demonstrated that CAR\/LepR+<br>MSC-derived Ebf3 and Ebf1 are required to maintain the HSC niche by inhibition of<br>osteogenesis.<br>Pericyte-MSC outside the BM<br>The early view on MSC as BM stroma cells has nowadays completely changed and the<br>occasionally used term &#8216;mesenchymal stromal cell&#8217; became misleading. Instead, it became<br>obvious that MSC within the BM are not part of the connective tissue stroma but are forming<br>the endosteal and perivascular niches. Most BM-MSC are of perivascular origin [54]. In a<br>landmark study, Crisan et al. clearly documented that MSC phenotypes exist outside the BM<br>in multiple organs as perivascular pericytes expressing typical BM-MSC markers like CD146,<br>NG2 and \u03b1-SMA, and being multipotent for osteogenic, chondrogenic, adipogenic and<br>myogenic lineages in vitro [66]. Further functional characterization tested whether such<br>pericyte-MSC possess the ability of BM-MSC to restore a hematopoietic niche in irradiated<br>mice [67]. The study revealed that sorted CD146+ perivascular cells, isolated from human<br>adipose tissue, are capable to support the long-term persistence of transplanted human HSC<br>while CD146- perivascular cells did not. This observation clearly demonstrated that BM-MSC<br>and pericytes expressing the same markers are equivalent in function.<br>Various studies have meanwhile demonstrated that MSC phenotypes could be isolated from<br>virtually all tissues of the body including fat, muscle, cord blood, Wharton&#8217;s jelly, placenta<br>and others [68]. This initiates the notion that possibly a unique MSC may exists but it became<br>obvious that all these MSC, beside core markers, display differential gene expression profiles<br>in a time and tissue-related manner and thereby affect stemness [69]. For example, muscle<br>pericytes are not spontaneously osteochondrogenic while cord blood-derived MSC<br>phenotypes display the unique capacity to form cartilage spontaneously in vivo. Furthermore,<br>there is evidence that also the intrinsic mechanical properties of the extracellular matrix<br>influences cell fate decisions in MSC, as softer matrices that mimic muscle are myogenic<br>while rigid matrices that mimic collagenous bone are osteogenic [70]. Collectively, this raises<br>the notion that mesenchymal stemness of MSC is adapted to or imprinted by tissue<br>microenvironment and that MSC from placenta, Wharton&#8217;s jelly, umbilical cord blood etc.<br>may display the most embryonal-like phenotype [68, 69].<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>13<br>Regarding the notion of developmental and tissue-related differences, Chen et al. recently<br>proposed the concept of multiple &#8216;paralogous&#8217; stem-cell niches which are progressively and<br>functionally transformed within an individual organism throughout its life span [58]. In their<br>view, delineation of distinct cell phenotypes results from complex multiple interchangeable<br>events of epithelial to mesenchymal transition (EMT) and reverse mesenchymal to epithelial<br>transition (MET). These dynamic processes make it difficult to discern cell identities and to<br>define reliable markers. Therefore, the question whether all pericytes give rise to MSC, or in<br>the alternative view, pericyte-MSC differ from BM-MSC but may derive from a common<br>progenitor, is not finally answered to date [49, 71, 72]. Surely, the answer will be complex<br>and limited by the accuracy and composition of available marker sets; &#8216;true&#8217; pericyte-MSC<br>may likely represent a subpopulation among all pericytes.<br>In vivo function of pericyte-MSC<br>Pericytes have been discovered in the early 1870s by C.J. Ebert and C.M.B. Rouget [73] and<br>were named by K.W. Zimmermann describing their contractile nature in 1923 [74]. Later<br>characterization specified that pericytes communicate with endothelial cells by both physical<br>contact and secreted factors to regulate growth, stability, architecture and blood flow of<br>microvessels as well as they are important for the integrity of the blood brain barrier and<br>provide clearance and phagocytosis in the brain [75].<br>Pericytes attach to the epithelium by their tips and their contractile apparatus consisting of<br>microfilaments containing actin, myosin and tropomyosin enables them to regulate the<br>capillary diameter or to move along the microvessels [76]. This indicated that perivascular<br>pericyte-MSC and their BM counterparts are not static but dynamic and their close proximity<br>to the vasculature enables them to readily mobilize and travel in the bloodstream to sites of<br>injury. Consistent with this view, pericytes respond to a series of pro-inflammatory stimuli<br>and are able to sense different types of tissue trauma signals by their expressed functional<br>pattern-recognition receptors and contribute to the onset of innate immune responses by cellcell<br>contact and paracrine effectors [73]. Similarly, transplanted BM-MSC home to various<br>sites of injury, e.g. stroke [77], pancreatic islet inflammation and diabetic kidney [78, 79] and<br>cancer [80]. Once on site, BM-MSC secrete a variety of immunomodulatory, antiinflammatory,<br>angiogenic, anti-apoptotic and tissue-regenerative trophic factors [81], and<br>fend off invading microbes by secretion of anti-microbial peptide LL36 that kills bacteria<br>upon contact [82, 83].<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>14<br>Altogether the ability of migration and humoral tissue restoration is a common feature of<br>MSC independent of their BM or pericyte origin. A.I. Caplan, who once coined the term<br>MSC, has meanwhile suggested to rename these cells &#8216;medicinal signalling cells&#8217; to more<br>accurately reflect the new conceptional view on MSC as a &#8216;drug store&#8217; for injured tissues in<br>vivo and to preserve the MSC nomenclature [84].<br>MSC in cancer<br>Besides MSC and HSC, the perivascular niche also accommodates tumour SC and its<br>microenvironment has been shown to regulate tumour dormancy and growth [85-87].<br>Tumours recruit pericytes by e.g. platelet-derived growth factor (PDGF) to maintain their<br>tumour vessels [88] and consequently, inhibition of PDGF receptor signalling causes pericyte<br>detachment and vessel regression, and diminishes tumour growth in several cancer models<br>[89-91]. Tumour cells further interact with the surrounding stroma leading to a chronically<br>increased release of inflammatory cytokines and growth factors [92] that has been described<br>as a &#8216;wound that never heals&#8217; [93]. The chronic inflammatory state drives the recruitment of<br>responsive cell types including MSC [94, 95] which account for 0.01\u20131.1% of total cells in<br>prostatectomies from human prostate tumours [96].<br>It is now understood that MSC interact with tumour cells at various stages of progression but<br>it is not finally clear whether their role is tumour promoting or suppressive. Several cancer<br>models implicated that MSC promote tumour progression and invasiveness as well as having<br>a role in the creation of a metastatic niche at the secondary site [97-100]. In contrast, MSC<br>suppressed tumour growth in several cancer models including breast cancer, Kaposi\u2019s<br>sarcoma, hepatoma and melanoma [101-104]. Reasons for conflicting findings may result<br>from the heterogeneity of tested MSC populations, differences in experimental design and<br>varying responses dependent on the stimuli [105].<br>However, it seems unlikely that transplanted MSC have a significant role in inducing or<br>promoting tumours in human subjects, as their clinical use has been considered safe since<br>1995 [56] and clinicians did not notice a tumour risk. In support of this notion, a metaanalysis<br>has studied 1012 participants who received MSC for treatment of ischemic stroke,<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>15<br>Crohn\u2019s disease, cardiomyopathy, myocardial infarction, graft versus host disease or served as<br>healthy volunteers but did not find any indication of malignancy [106].<br>Meanwhile, research has employed the recruitment of MSC to tumours in order to target<br>malignant diseases with genetically modified MSC that, for example, overexpress pigment<br>epithelium-derived factor (PEDF) to reduce angiogenesis or overexpress TNF-related<br>apoptosis inducing ligand (TRAIL) to induce apoptosis [107]. Despite using MSC from<br>different sources, different transfection methods and a wide array of expressed proteins, the<br>data consistently showed a reduction in tumor growth and prolonged survival in rodents.<br>These promising pre-clinical outcomes initiated the first-in-man trial TREAT-ME-1 which<br>aimed to target advanced gastrointestinal cancer (ClinicalTrials.gov: NCT02008539).<br>The trial used ganciclovir (GCV) in combination with autologous BM-MSC overexpressing<br>herpes simplex virus thymidine kinase (HSV-Tk) under the control of the CC-chemokine<br>ligand 5 (CCL5\/RANTES) promoter. Mechanistically, engineered MSC migrate to tumours<br>where they become activated to express CCL5 [98]. Subsequently induced HSV-Tk<br>phosphorylates GCV which then inhibits DNA polymerases and thereby induces apoptosis in<br>transfected cells and, due to a bystander effect, also in nearby tumour and stromal cells [108].<br>The primary study aim was to evaluate safety and tolerability, and both features were found<br>generally favorable with stable disease in four patients, and progressive disease in 2 patients<br>after one year follow-up [109]. Slowed tumour progression and enhanced survival are of great<br>importance in the field and engineered MSC may contribute in the future to prolong the life of<br>cancer patients. Side note: the HSV-Tk\/GCV suicide gene technique has also been tested as<br>an &#8217;emergency switch&#8217; that would allow to eliminate transplanted iPSC in case of malfunction<br>[110].<br>Transdifferentiation of MSC into insulin producing pancreatic \u03b2-cells<br>There was initially great optimism that MSC could be easily transdifferentiated across the<br>germ layer border into insulin producing pancreatic \u03b2-cells and thereby avoid the ethical and<br>tumorigenic obstacles of ESC and iPSC. Generation of insulin producing cells from MSC<br>employed genetic engineering including overexpression of PDX1, neurogenin 3 (NGN3) and<br>paired box 4 (PAX4) [111-113] and\/or complex in vitro protocols using various conditions<br>and factors to resemble pancreatic development [114-118]. Depletion of \u03b2-cells in rodents by<br>a high dosage of the \u03b2-cell toxic compound streptozotocin (STZ) has frequently been used to<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>16<br>test the functional capacity of transplanted insulin producing cells. As a variant related to<br>aspects of T2DM [119], multiple low-dose STZ-treatment causes islet inflammation for<br>testing of MSC-mediated recovery of \u03b2-cell dysfunction and partial loss. Aspects related to<br>the immunology of T1DM have been investigated in female NOD mice with spontaneously<br>occurring autoimmune insulitis [120].<br>Several studies reported that transplanted MSC-derived insulin producing cells can improve<br>glycemia in STZ-diabetic rodents [111, 114, 118, 121]. Nevertheless, stem cell specialists<br>remained sceptic concerning in vitro transdifferentiation of MSC beyond mesodermal<br>lineages. In this regard, the efficiency of MSC transdifferentiation was generally very low and<br>resulting insulin producing phenotypes frequently possessed an acurate secretory capacity but<br>were not further expandable or vice versa. To date, transdifferentiation of MSC has not<br>reached clinically significant large scale production of pancreatic progenitors or \u03b2-cells as it<br>has been established for ESC and iPSC.<br>The study of Ianus et al. initiated the notion that injected BM cells contain a subpopulation of<br>cells that engraft into islets and are capable to transdifferentiate into insulin producing<br>phenotypes in vivo [122]. It was observed that injection of BM cells with insulin gene 2<br>promoter driven GFP expression into sublethally irradiated mice gave rise to a small<br>proportion of 1.7-3% glucose-responsive GFP+\/insulin+ cells within islets which, after<br>isolation and sorting, show a functional insulin secretion comparable to control \u03b2-cells.<br>Insulin+ phenotypes could be reproduced in a subsequent study. Hess et al. transplanted BM<br>cells from GFP mice in NOD\/SCID mice with multiple low-dose STZ-induced islet<br>inflammation and noted partial recovery of diabetic blood glucose levels [78]. GFP-BM-cells<br>significantly migrate to the inflamed endocrine pancreas and their occurrence within islets<br>was associated with enhanced local proliferation and 2.5% GFP+\/insulin+ cells. Since the<br>insulin+\/GFP+ cells did not express PDX1, a major marker of a mature and functional \u03b2-cell,<br>the authors concluded that amelioration of hyperglycemia was not caused by incompletely<br>differentiated GFP+\/insulin+ cells but by the proliferative increase in \u03b2-cell mass.<br>In further testing, using injection of GFP-BM cells into single-dose STZ-treated mice, only 2<br>GFP+\/insulin+ cells out of more than 100,000 screened \u03b2-cells could be retrieved [123].<br>These very rare events were considered to rather result from cell fusion than<br>transdifferentiation [124, 125]. Importantly, an elaborated lineage tracing study from Douglas<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>17<br>Melton\u2019s group strongly suggested that new \u03b2-cells and islets only derive from pre-existing \u03b2-<br>cells and not from adult pancreatic stem cells or progenitors [126]. In this regard, a later study<br>reported that up to 3% of injected human BM-MSC engrafted into inflamed pancreatic islets<br>of multiple low-dose STZ-diabetic NOD\/SCID and improved hyperglycemia by reduction of<br>\u03b2-cell loss and partly maintained mouse insulin blood levels in the absence of detectable<br>human insulin [79]. In addition, up to 11% of injected human BM-MSC engrafted into the<br>STZ-injured kidneys and improved glomerular morphology as well as decreased mesangial<br>thickening and macrophage infiltration.<br>Collectively, these studies exclude significant transdifferentiation of MSC into insulin<br>producing cells in vivo and pave the way for the new understanding that MSC migrate to and<br>engraft at site of injury to support tissue repair by secretion of numerous tissue regenerative<br>factors [81].<br>Humoral potential of MSC<br>After isolation, pancreatic islets suffer from hypoxic culture stress due to loss of blood supply<br>and consequently impeded transport of oxygen to the inner cell layers of the threedimensional<br>islet structure [127, 128]. After transplantation, islets were further challenged by<br>local inflammation and rejection processes [129]. Fast dynamics of revascularisation and<br>downregulation of immune responses have been considered important for long-term graft<br>function and generated interest on the angiogenic and immunomodulatory potential of MSC<br>in the context of islet transplantation.<br>Kinnaird et al. displayed that human MSC express a wide array of arteriogenic cytokine genes<br>and that MSC conditioned media promoted smooth muscle cell proliferation and migration in<br>a dose-dependent manner in vitro [130]. In vivo, using a murine hindlimb ischemia model,<br>murine MSC conditioned media enhanced collateral flow recovery and remodeling, improved<br>limb function, reduced the incidence of autoamputation, and attenuated muscle atrophy<br>compared with control media. In this regard, Figliuzzi et al. tested the angiogenic effects of<br>BM-MSC on co-transplanted islets in STZ-diabetic rats and noted that improved graft<br>survival and function in association with increased numbers of new capillaries and expression<br>of vascular endothelial growth factor (VEGF) [131]. Upcoming studies confirmed the<br>angiogenic capacity of MSC and its association with VEGF [132-135]. In this regard, it was<br>shown in vitro that VEGF inhibition partially blocked the enhanced formation of<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>18<br>anastomosing tubule networks by co-cultured endothelial cells [134]. Therefore, VEGF<br>appears to be an important player which is supported by other MSC-derived factors such as<br>nerve growth factor (NGF) [136] and factors inducing angiopoietin receptor Tie-2 expression<br>in islets [135]. In sum, these studies established that MSC-mediated revascularisation<br>contributes to islet graft survival by shortening the post-transplantation ischemia period.<br>Improved revascularization and functional outcome of co-transplanted islet grafts have been<br>further associated with reduced numbers of terminal deoxynucleotidyl transferase mediated<br>dUTP nick end labeling (TUNEL)+ and caspase-3+ apoptotic cells [137, 138]. Angiogenic<br>VEGF and several other MSC-released trophic factors including hepatocyte growth factor<br>(HGF), insulin-like growth factor (IGF)-1, transforming growth factor (TGF)-\u03b2, basic<br>fibroblast growth factor (bFGF) and granulocyte-macrophage colony-stimulating factor (GMCSF)<br>display anti-apoptotic properties [81, 139]. The potential of MSC to mediate survival<br>was tested by direct interactions with \u03b2-cells in vitro in the absence of third party cells from<br>surrounding tissues.<br>In line with the variety of released growth factors, we and others displayed that MSCconditioned<br>medium or co-cultured MSC preserve Akt signaling in cultured islets undergoing<br>hypoxic culture stress and additional treatment with alloxan and STZ [135, 140]. Akt<br>signaling promotes survival and reduces intrinsic apoptosis by its influence on B-cell<br>lymphoma 2 (Bcl-2) family proteins such as phosphorylation of Bcl-2 antagonist of cell death<br>(BAD) and caspase-9 [141]. MSC-released factors also activate mitogenic extracellular<br>signal\u2013regulated kinases (ERK)1\/2 signaling which, similar to Akt, promotes survival by<br>inhibition of intrinsic apoptosis [142, 143]. Interestingly, MSC induced ERK1\/2 signaling<br>only in highly proliferative endothelial cells and INS-1E insulinoma cells but not in primary<br>mouse islets with a low proliferation rate [135, 140, 144]. These observations indicate an<br>important role for the Akt pathway in MSC-mediated survival of pancreatic islets.<br>MSC-released factors have been further reported to improve insulin secretion and glucoseresponse<br>(see Table 1 in [145]). Experiments may indicate a beneficial effect of cell-cell<br>contacts since humoral improvement of glucose-stimulated insulin secretion (GSIS) in<br>indirect co-cultures with cells separated by membranes [135] was not well reproducible by<br>other studies unless cells were cultured in direct contact [146, 147]. In this respect, MSC<br>enhance GSIS in vitro by release of annexin-1 (ANXA1) while MSC from Anxa1-\/- mice had<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>19<br>no functional capacity [148]. Hence, heterogeneous effects of MSC on GSIS may partly result<br>from different expression levels of ANXA1. Likely, the very close proximity of MSC and<br>islets in direct co-cultures enhanced local effector levels and involves the extracellular matrix<br>(ECM) since MSC co-cultured with HSC maintain the vascular niche by upregulated<br>expression of intercellular adhesion molecule 1 (ICAM1) and vascular cell adhesion molecule<br>1 (VCAM1) [149]. Such supportive processes are an important topic in tissue engineering and<br>it has been recognized that islets, which lost ECM during enzymatic isolation, show improved<br>survival and function after treatment with ECM molecules [150].<br>Moreover, numerous MSC-released factors exhibit potent immunomodulatory characteristics;<br>e.g. transforming growth factor-\u03b21 (TGF-\u03b21), indoleamine 2,3-dioxygnase (IDO), nitric oxide<br>(NO), human leukocyte antigen-G (HLA-G), Prostaglandin E2 (PGE2), interleukin-1 receptor<br>antagonist (IL-1RA) and tumour necrosis factor-stimulated gene 6 (TSG-6) [81, 139, 151]. As<br>a result, MSC have been described to induce regulatory T cells and anti-inflammatory M2<br>macrophages, and to inhibit T cells, natural killer cells and T helper (Th)17 cell differentiation<br>as well as maturation of dendritic cells (DC).<br>Consequently, MSC substantially reduced co-transplanted islet graft inflammation and<br>rejection in BALB\/c mice [138, 152], humanized NOD scid gamma (NSG) mice [153] and a<br>cynomolgus monkey model [154]. All these studies showed MSC-improved engraftment in<br>association with reduced infiltration of T cells and neutrophils, and increased numbers of<br>circulating regulatory T cells. Inhibitors established that MSC-mediated prevention of T cell<br>proliferation and islet graft rejection was not related to IDO and heme oxignase-1, partially<br>related to NO and profoundly mediated by matrix metalloproteases (MMP)-2 and MMP-9 via<br>reduction of IL-2 receptors on T cells [152]. MSC further suppress the proliferation and<br>activation of T cells by interaction with IL-10-producing CD14+ monocytes [153].<br>Remarkably, systemically injected MSC in female NOD mice reduced the incidence of<br>spontaneous T1DM [155] or reversed recent-onset hyperglycemia via release of programmed<br>cell death ligand 1 (PD-L1) and inhibition of myeloid\/inflammatory DC through an IL-6-<br>dependent mechanism [156]. Moreover, treatment of NOD mice with CD4+CD62L+<br>regulatory T cells (Treg), which have been cocultured with cord blood-derived MSC before,<br>resulted in a marked reduction of spontaneous autoimmune insulitis, restored Th1\/Th2<br>cytokine balance in blood and induced apoptosis of infiltrated leukocytes in pancreatic islets<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>20<br>[157]. This concept has been translated into clinic as &#8216;Stem Cell Educator&#8217; therapy (see below)<br>[158, 159].<br>In addition, MSC have been further tested for their ability to ameliorate wound healing which<br>is a frequent diabetic complication. Endogenous MSC, present in the skin as dermal sheath<br>cells surrounding hair follicle units [160] and as perivascular pericytes [161]. Skin injury<br>induces MSC to recruit and activate epithelial cells, fibroblasts and keratinocytes to<br>revascularize and re-populate the wounded area during the proliferative healing phase [162].<br>Wounds treated with MSC show acceleration of angiogenesis and re-epithelialisation [163]<br>which, according to the notion of paracrine factors, could also be achieved by treatment with<br>MSC-conditioned medium [164-166]. Wound healing is impaired in DM patients which show<br>degraded micro- and macrovessels in association with early occurring detachment and loss of<br>vascular pericytes at capillaries [167, 168]. Importantly, MSC-treatment successfully<br>improved wound healing under diabetic conditions such as in diabetic db\/db mice with<br>mutated leptin receptor [169] and a rat model of diabetic foot ulceration [170].<br>MSC in clinical trials<br>The complex and wide-ranged humoral potential of MSC attracted much attention among<br>researchers and clinicians. MSC can be isolated from various tissues, frequently from BM and<br>adipose tissue, by minimal invasive puncture and they also allow noninvasive retrieval from<br>often discarded &#8216;medical waste&#8217; such as placenta, cord blood and umbilical cord [68, 171]. It is<br>further known from early CFU-F studies and numerous studies since then that MSC could be<br>easily expanded in vitro without significant loss of their mesenchymal differentiation capacity<br>or their humoral secretion. Moreover, MSC are immune-privileged because they express very<br>low levels of major histocompatibility complex (MHC) class I and no MHC class II which<br>normally prevents or strongly reduces immune responses [172, 173]. In clinical use since<br>1995 [56], MSC are considered clinically safe [106] and both administration of autologous<br>and also allogenic MHC-mismatched MSC is generally well tolerated and clinically effective<br>[174-176].<br>To date, CinicalTrials.gov listed over 850 therapeutic approaches using MSC to target a broad<br>array of diseases including hematological disease, graft-versus-host disease (GVHD), organ<br>transplantation, cardiovascular and neurological diseases, bone and cartilage repair as well as<br>inflammatory and autoimmune diseases [177]. Among these, more than 60 trials address<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>21<br>T1DM and T2DM, and from these we have summarized all trials with reported outcome in<br>Table 1. In these trials, the various humoral features of MSC address different disease aspects<br>(Fig. 1). In many patients with T1DM a minor portion of insulin producing \u03b2-cells survive but<br>can not recover unless thereby induced autoimmune responses are blocked [178]. MSC<br>mediate immune tolerance that aims to enable partial recovery of remaining \u03b2-cell mass [158,<br>159] or to reduce and delay the \u03b2-cell destruction during new-onset of T1DM [179, 180]. In<br>T2DM, the anti-inflammatory features of MSC were used to ameliorate chronic low-grade<br>inflammation which has been recognized as an important cause of insulin resistance and \u03b2-<br>cell dysfunction [119]. These features in combination with secretion of pro-angiogenic factors<br>should improve engraftment and survival of transplanted islets [181].<br>Interestingly, there is only one completed trial investigating the effect of MSC cotransplantation<br>on islet graft survival and function. Potentially, there are concerns on the<br>additional expense needed for generation, testing and application of clinical-grade MSC since<br>established immunosuppression regimes should prevent graft rejection. In this regard, Wang<br>et al. tested combined autotransplantation of BM-MSC and islets in chronic pancreatitis<br>patients undergoing pancreatectomy without immunosuppression [181]. Patients showed<br>reduced insulin requirement in the peritransplantation period, reduced decline of C-peptide<br>levels after 6 month and lowered fasting blood glucose levels after 12 month. This suggests<br>that co-transplanted MSC reduced loss of islet graft function. Additional studies and longterm<br>observations are needed to verify these very limited results from 3 patients.<br>The other studies addressed T1DM (7 trials) as well as severe T2DM (8 trials) in patients who<br>required insulin and\/or oral anti-diabetic drugs to control glycemia. Currently the total number<br>of investigated patients is relatively small. In total, 276 patients were investigated in small<br>groups of 6-22 subjects and 3 studies [159, 174, 182] analyzed groups of 31-45 subjects. The<br>enrolled patients show diversity regarding age, BMI and other aspects as well as duration and<br>severeness of the disease. In this view, also applied MSC came from different sources<br>including BM, adipose tissue and umbilical cord, have been differentially processed and<br>applied in different dosages. Though MSC did not cure the disease and despite much<br>heterogeneity regarding applied MSC, it is quite astonishing that studies reported varying<br>positive aspects of partially improved glycemia. Only two T2DM trials reported on diabetic<br>complications. Jiang et al. noted without further details that renal and cardiac functions<br>showed varying degrees of improvement [183] and Hu et al. found no rise of diabetic<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>22<br>complications in MSC-treated patients while placebo-treated patients displayed higher<br>incidences of diabetic retinopathy, neuropathy and nephropathy during 36 months follow-up<br>[182]. In general, MSC were well tolerated and it could be noted as the quintessence of<br>outcome that all trials except one [179] reported reduced requirement for exogenous insulin<br>and\/or anti-diabetic drugs.<br>Two studies addressed the question whether MSC treatment could delay development of<br>newly-onset T1DM. Hu et al. reported that both the HbA1c and C-peptide were improved<br>compared to the pre-therapy values and to control patients during 2 years follow-up [180].<br>Consequently, MSC-patients required smaller insulin dosages. This outcome indicated a<br>reduced loss of insulin producing \u03b2-cells but was not fully reproduced by Carlsson et al. who<br>observed improved C-peptide levels in response to a mixed-meal tolerance test but no changes<br>in HbA1c, fasting C-peptide and daily insulin dosages after 1 year [179]. More trials with<br>prolonged observation periods are needed to clarify the potential of MSC to delay the<br>development of T1DM.<br>An interesting aspect is the so-called &#8216;Stem Cell Educator&#8217; [158, 159]. While studies normally<br>apply MSC by intravenous injection, the &#8216;Stem Cell Educator&#8217; approach routed the patient&#8217;s<br>blood through a closed-loop system that separates lymphocytes from the whole blood and<br>briefly co-cultures them with adherent cord blood-derived MSC before returning them into<br>the patient\u2019s circulation. Though MSC are not delivered into the body, their temporary contact<br>to patient&#8217;s lymphocytes was sufficient to induce immune tolerance which ameliorates the<br>disturbed Th1\/Th2\/Th3 cytokine balance with increased Treg numbers in type 1 diabetic<br>patients and decreased CD86+\/CD14+ monocytes and reduced markers of inflammation in<br>type 2 diabetic patients. As a result, all patients displayed a generally reduced requirement for<br>insulin and metformin and improved HbA1c values after 10-12 months follow-up. In addition,<br>homeostasis model assessment of insulin resistance (HOMA-IR) demonstrated that insulin<br>sensitivity was improved post-treatment in type 2 diabetics. The potential of the &#8216;Stem Cell<br>Educator&#8217; is currently further investigated by 2 further trials (ClinicalTrials.com:<br>NCT02624804 and NCT03390231).<br>Collectively, the trials show that even heterogeneous MSC populations could be clinically<br>effective. The question, however, remains whether clinical outcome could be improved by<br>optimized MSC batches since actually no standardized method exists for isolation,<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>23<br>characterization, expansion, potency testing or pathogen screening [184-186]. A basic issue is<br>the donor heterogeneity which has the potential to dramatically influence therapeutical<br>properties of MSC. This includes the question whether autologous MSC are a good choice for<br>cell therapy of DM since, for eample, hyperglycemia induces pericyte dysfunction via<br>activation of p75 neurotrophin receptor\/NF-kB-mediated release of microparticles carrying<br>miR-503 from neighbouring endothelial cells [187]. Also subclinical inflammation present in<br>subjects with metabolic syndrome and T2DM [119] impairs the vascular stem cell niche and<br>leads to MSC dysfunction [188]. MSC batches could be further influenced by isolation and<br>expansion since several studies suggested that outgrowth from donor tissue generates less<br>heterogeneous cell populations with increased proliferation rates and cell viability than<br>isolation by enzymatic tissue digestion [189-191]. Moreover, MSC may lose their functions<br>due to increased cellular senescence during longer expansion and passaging since a direct<br>positive link between early passages of MSC and clinical outcomes in GVHD has been<br>demonstrated [192]. One should finally keep in mind that only a small proportion of<br>systemically injected MSC engraft at site of injury while most rapidly embolise in the lungs<br>and disappear with a half-life of about 24 h to an unclear fate [193, 194].<br>The International Society for Cell Therapy (ISCT) defined clinically useful MSC by<br>mesenchymal differentiation (into bone, cartilage and fat), plastic-adherent growth in vitro<br>and expression of CD73, CD90 and CD105 in the absence of hematopoietic surface markers<br>[195]. Notably, expansion of plastic-adherent BM cells favours the expansion of nonclonal<br>stromal cell-enriched populations, often misinterpreted as pure SC fractions, which contain<br>varying percentages of true MSC, e.g. depending on donor age [50], and thereby plausibly<br>exhibit different clinical effectiveness [196, 197]. This demands a reliable assay, such as the<br>CFU-F assay, and careful evaluation of each MSC batch may allow the identification of the<br>percentage of stem cells and their multilineage potential in each batch of nonclonal MSC.<br>Potentially, efficacy of MSC populations could be further enhanced by selection via<br>additional markers such as stromal (STRO)-1, CD146, alkaline phosphatase, CD49a, CD271<br>and VCAM1 [197]. Against this background, the US Food and Drug Administration (FDA)<br>demands registering of tissue processing facilities which should report on (i) prevention of<br>transmitting communicable disease via contaminated tissue, (ii) proper handling and<br>processing of tissue and (iii) demonstration of clinical safety and effectiveness of cells,<br>especially after extensive manipulation.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>24<br>Conclusion on the current state of stem cell therapy of diabets mellitus<br>Stem cell therapy has to deal with a wide array of limitations which are still the subject of<br>current research. See Table 2 for summary and comparison of SC in cell therapy of DM.<br>Differentiation of ESC and iPSC has meanwhile reached clinical large-scale production and<br>current developments of macroencapsulation may provide clinical safe usage of these cells<br>that demonstrate otherwise potentials for tumor development. Macroencapsulation prevents<br>the escape of embedded cells into the body and subcutaneously transplanted devices could be<br>retrieved and removed easily. The outcome of Viacyte&#8217;s first-in-man trial of their pancreatic<br>endoderm implant VC-01 will clarify whether the use of ESC and iPSC is an option in DM<br>therapy in the near future.<br>MSC are clinically safe and several trials exist though they are limited in number and<br>investigated patients. Currently, MSC-based therapy is no cure but shows a potential to<br>ameliorate DM since most studies report decreased requirement of exogenous insulin and\/or<br>anti-diabetic drugs. In this regard, MSC may be best used with diabetic patients that have<br>severe problems in controlling glycemia by conventional therapies; e.g. patients with brittle<br>DM. 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T1DM<br>Reference,<br>Trial number,<br>Country,<br>Patient number,<br>Duration<br>Disease<br>Objective<br>Patient characteristics Treatment Main outcomes<br>Wang et al. 2018<br>NCT02384018<br>United States<br>n = 3<br>12 months<br>Testing safety and effects of<br>BM-MSC and islet<br>autotransplantation in<br>patients with chronic<br>pancreatitis undergoing total<br>pancreatectomy<br>Aged 26, 29 and 42<br>years with chronic<br>pancreatitis<br>Infusion of 20 \u00b1 2.6 x 106<br>BM-MSC together with<br>5,107 \u00b1 1,920 islet<br>equivalents\/kg via the<br>portal vein<br>101 patients with<br>pancreatectomy due to<br>chronic pancreatitis who<br>received islets alone<br>served as historical<br>controls<br>No AE directly related to MSC<br>Insulin requirement lowered in the peritransplantation<br>period<br>Fasting blood glucose lowered<br>Fasting C-peptide with smaller declines<br>during months 1-6 (mean C-peptide levels<br>comparable to control values at 6 months)<br>HbA1c not different<br>Improved life quality<br>Cai et al. 2016<br>NCT01374854<br>China<br>n = 21<br>12 months<br>Testing safety and effects of<br>combined UC-MSC plus<br>autologous BM-MNC without<br>immunotherapy on C-peptide<br>Aged 18-40 years with<br>established T1DM for<br>2-16 years<br>HbA1c 7.5-10.5%<br>Fasting serum C-peptide<br>&lt; 0.1 pmol\/ml<br>Daily insulin requirement<br>&lt; 100 IU<br>Infusion of UC-MSC (1.1 x<br>106\/kg) and BM-MNC<br>(106.8 x 106\/kg) through<br>supraselective<br>pancreatic artery<br>cannulation<br>Controls received<br>standard care (n = 21)<br>MSC-treatment was well tolerated<br>1 patient with puncture site bleeding<br>1 patient with abdominal pain<br>Serum C-Peptide AUC 105.7% increase,<br>controls 7.7% decrease<br>Serum insulin AUC 49.3% increase, controls<br>5.7% decrease<br>HbA1c decreased 12.6%, controls increased<br>by 1.2%<br>Reduced insulin requirement (-29.2%) with<br>no change in controls<br>Carlsson et al. 2015 Testing safety and effects of Aged 18-40 years IV infusion of 2.1\u20133.6 x No side effects of MSC treatment<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>41<br>NCT01068951<br>Sweden<br>n = 9<br>12 months<br>autologous BM-MSC in<br>treatment of patients with<br>recently diagnosed T1DM<br>T1DM newly diagnosed<br>&lt; 3 weeks before<br>enrollment<br>MMTT-stimulated serum<br>C-peptide \u02c3 0.1 nmol\/l<br>106 autologous BMMSC\/<br>kg<br>Sham controls (n = 9)<br>HbA1c, fasting C-peptide and insulin<br>requirements not different compared to<br>controls<br>MMTT-induced C-peptide AUC and peak<br>values were preserved\/increased by MSC<br>Dave et al. 2015<br>India<br>n = 10<br>36 months<br>Testing co-infusion of ISC (in<br>vitro differentiated from<br>adipose tissue-derived MSC)<br>together with BM-HSC<br>Aged 8-45 years<br>IDDM for at least 6<br>months<br>C-peptide levels &lt; 0.5<br>ng\/ml<br>Infusion into portal<br>circulation, thymus and<br>subcutaneous tissue<br>ISC: mean of 3.34 ml cell<br>inoculums with 5.25 x<br>104 cells\/\u03bcl; ISC<br>expressed ISL1, PAX6<br>and IPF1 with mean Cpeptide<br>and insulinsecretion<br>of 1.03 ng\/ml<br>and 17.48 l IU\/l after 2 h<br>in glucose medium<br>HSC: mean of 103.5 mL<br>with 2.66 x 106\/\u03bcL<br>No untoward effect of stem cell infusion<br>Improved serum C-peptide, Hb1Ac, blood<br>sugar levels<br>Reduced exogenous insulin requirement<br>Patients returned to normal lifestyle and<br>unrestricted diet<br>Thakkar et al. 2015<br>India<br>n = 20<br>24 months<br>Testing co-infusion of ISC (in<br>vitro differentiated from<br>adipose tissue-derived MSC)<br>together with BM HSC<br>Comparison of autologous vs.<br>allogenic stem cells<br>Aged 8-45 years<br>Group 1: mean age 20.2<br>years, mean disease<br>duration 8.1 years<br>Group 2: mean age 19.7<br>years, mean disease<br>duration 7.9 years<br>Infusion into portal<br>circulation, thymus and<br>subcutaneous tissue<br>Group 1 received 2.65 \u00b1<br>0.8 x 104 autologous<br>ISC\/kg (n = 10); ISC<br>expressed ISL1, PAX6<br>and IPF1<br>Group 2 received 2.07 \u00b1<br>0.67 x 104 allogenic<br>ISC\/kg (n = 10)<br>HSC not reported<br>No untoward effect, morbidity (pulmonary<br>embolism, sepsis) or mortality caused by<br>therapy<br>Reduced insulin requirement<br>Sustained improvement in serum C-peptide<br>and HbA1c<br>Hu et al. 2013<br>China<br>Testing the long-term effects of<br>WJ-MSC for newly-onset<br>T1DM<br>Aged 17.6 \u00b1 8.7 years<br>T1DM according to ADA<br>criteria for less than 6<br>2 IV infusions with a mean<br>of 1.5-3.2 \u00d7 107 WJMSC<br>with an interval of<br>No acute or chronic side effects compared to<br>control group<br>Fasting plasma glucose levels not different<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>42<br>n = 15<br>24 months<br>months<br>Fasting C-peptide \u2265 0.3<br>ng\/ml<br>1 month<br>Control group received<br>saline (n = 14)<br>from controls<br>Improved HbA1c, fasting C-peptide and<br>postprandial blood glucose levels<br>Reduced insulin requirement<br>Zhao et al. 2012<br>NCT01350219<br>China, Spain<br>n = 12<br>10 months<br>Testing safety and efficacy of<br>Stem Cell Educator therapy<br>Aged 15 to 41 years<br>with a diabetic history<br>of 1 to 21 years<br>Group A: with some<br>residual pancreatic \u03b2-<br>cell function (n = 6)<br>Group B: without (n = 6)<br>Stem Cell Educator<br>therapy: patient\u2019s blood<br>circulated through a<br>closed-loop system that<br>separates lymphocytes<br>from the whole blood<br>and briefly co-cultures<br>them with adherent CBMSC<br>before returning<br>them to the patient\u2019s<br>circulation<br>No AE, minimal pain from two venipunctures<br>Reduced insulin requirement (24 weeks)<br>Improved fasting C-peptide levels and<br>reduced HbA1C (12 weeks) in groups A<br>and B<br>Increased in basal and glucose-stimulated Cpeptide<br>levels (40 weeks, group B)<br>Increased expression of co-stimulating<br>molecules CD28 and ICOS, increased<br>numbers of Tregs and restored<br>Th1\/Th2\/Th3 cytokine balance (4 weeks,<br>groups A and B)<br>Sham controls (n = 3) without significant<br>changes<br>Vanikar et al. 2010<br>India<br>n = 11<br>12 months<br>Testing co-infusion of allogenic<br>ISC (in vitro differentiated<br>from adipose tissue-derived<br>MSC) together with BM HSC<br>Aged 5-45 years<br>IDDM for 1-24-years<br>Low serum C-peptide<br>levels &lt; 0.5 ng\/ml<br>Intraportal infusion<br>ISC: mean of 1.5 ml with<br>2.1 x 103\/\u03bcL; ISC<br>expressed ISL1, PAX6<br>and IPF1<br>HSC: mean of 96.3 ml<br>with 28.1 \u00d7 103\/\u03bcL<br>No adverse side effect related to stem cell<br>infusion or therapy<br>Reduced insulin requirement<br>HbA1c decreased<br>Serum C-peptide levels increased<br>Patients became free of diabetic ketoacidosis<br>events<br>Section B. T2DM<br>Reference,<br>Trial number,<br>Country,<br>Patient number,<br>Duration<br>Disease<br>Objective<br>Patient characteristics Treatment Main outcomes<br>Bhansali et al. 2017 Comparison of safety and Aged 30-60 years with Infusion of 106 BM-MSC 1 patient with local extravasation of blood<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>43<br>NCT01759823<br>India<br>n = 10<br>12 months<br>effects of autologous BMMSC<br>and BM-MNC in<br>reducing on insulin<br>requirement<br>T2DM \u2265 5 years and<br>failure to achieve HbA1c<br>\u2264 7.5% while receiving<br>triple oral anti-diabetic<br>drugs in optimal doses<br>along with insulin for the<br>last 6 months<br>(group I, n = 10) or 109<br>BM-MNC (group II, n =<br>10) via transfemoral<br>route into the celiac<br>trunk<br>Sham controls were<br>infused into the femoral<br>artery (group III, n = 10)<br>following infusion<br>Reduced insulin requirement in BM-MSC and<br>BM-MNC groups (6 of 10 patients in both<br>BM-MSC and BM-MNC groups, but none in<br>the control group achieved the primary end<br>point of \u2265 50% reduced insulin requirement)<br>Increased 2nd-phase C-peptide response in<br>BM-MNC group<br>Improvement in insulin sensitivity index with<br>increased insulin receptor substrate-1 gene<br>expression in ABM-MSC group<br>Hu et al. 2016<br>China<br>n = 31<br>36 months<br>Testing safety and long-term<br>effects of WJ-MSC on<br>T2DM<br>Aged 18-60 years with<br>T2DM according to ADA<br>criteria<br>2 infusions of 106 WJ-MS<br>with an interval of 1<br>month (group I) through<br>veins in the back of the<br>hand<br>Controls (group II)<br>received normal saline<br>(n = 30)<br>No serious AE<br>No chronic side effects or lingering effects<br>Fasting plasma glucose almost unchanged<br>Reduced insulin requirement<br>Fasting C-peptide improved<br>HbA1c and postprandial plasma glucose<br>improved by trend after 36 months<br>HOMA of \u03b2-cell secretory function improved<br>HOMA-IR unchanged<br>Incidence of diabetic retinopathy, neuropathy<br>and nephropathy only increased in controls<br>Skyler et al. 2015<br>NCT01576328<br>United States<br>n = 45<br>3 months<br>Testing safety, tolerability,<br>and feasibility of allogeneic<br>BM-derived STRO-3-<br>selected subset of BMderived<br>MPC<br>(Rexlemestrocel-L,<br>Mesoblast Inc.; product<br>expressed MSC markers<br>STRO-1 and CD146) in<br>T2DM inadequately<br>controlled with metformin or<br>one additional oral anti-<br>Aged &lt; 80 years with<br>T2DM for 10.1 \u00b1 6 years<br>HbA1c 7.0-10.5%<br>Metformin either alone or<br>in combination with one<br>other oral antidiabetic<br>medication (except a<br>thiazolidinedione) for at<br>least 3 months<br>IV infusion of 0.3, 1 or 2 x<br>106 BM-derived MPC (n<br>= 15 each)<br>Sham controls (n = 15)<br>No serious acute AE due to infusion<br>No serious hypoglycemia events or<br>discontinuations due to AE, comparable AE<br>in MSC and placebo groups, 1 subject with<br>severe abdominal pain in MSC group<br>No immunologic responses to MSC<br>HbA1c reduced by trend, more pronounced<br>in patients with baseline HbA1c \u2265 8%<br>Insulin requirement reduced by trend<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>44<br>diabetic drug<br>Guan et al. 2015<br>China<br>n = 6<br>24-43 months<br>Testing safety and effects of<br>allogenic UC-MSC<br>Aged 27-51 years<br>Time from hyperglycemia<br>to first infusion was 4-<br>157 weeks<br>Patients treated with<br>insulin and poorly<br>controlled blood glucose<br>levels and HbA1c<br>2 IV infusions of 106 UCMSC\/<br>kg through the<br>cubital vein with an<br>interval of 14-17 days<br>No safety issues during infusion and the<br>long-term monitoring period<br>Reduced insulin requirement (significant<br>during months 1-6), 3 patients became<br>insulin-free for 25 to 43 months<br>Insulin-free patients displayed reduced<br>HbA1c and increased fasting C-peptide<br>during months 1-24<br>Relative stable fasting plasma glucose and 2<br>h postprandial blood glucose levels<br>Liu et al. 2014<br>Chinese Clinical Trial<br>Register ChiCTRONC-<br>10000985<br>China<br>n = 22<br>12 months<br>Testing safety and effects of<br>treatment with allogenic<br>WJ-MSC<br>Aged 18\u201370 years<br>T2DM according to ADA<br>criteria<br>Poor glycemic control with<br>recent antidiabetic<br>therapies, including<br>drugs and\/or insulin<br>injection for at least 3<br>months<br>GAD antibody negative<br>Fasting blood glucose<br>level \u2265 7.0 mmol\/L<br>HbA1c \u2265 7%<br>2 infusions of 106\/kg WJMSC<br>1st infusion via peripheral<br>vein on day 5<br>2nd infusion directly<br>delivered to the<br>pancreas via the splenic<br>artery using<br>endovascular catheters<br>on day 10<br>3 patients with fever after operative day<br>1 patient with subcutaneous hematoma<br>1 patient with nausea, vomiting and<br>headache<br>Improved HbA1c, fasting C-peptide levels,<br>HOMA of \u03b2-cell secretory function,<br>postprandial blood glucose levels<br>Reduced insulin requirement and oral<br>hypoglycemic drugs<br>Reduced serum levels of IL-1\u03b2 and IL-6, and<br>reduced numbers of CD3+ and CD4+ T<br>lymphocyte numbers at 6 months<br>Kong et al. 2014<br>NCT01413035<br>China<br>n = 18<br>6 months<br>Testing safety and effects of<br>allogenic UC-MSC<br>Aged 23-65 years<br>T2DM according to WHO<br>criteria<br>Patients received insulin<br>and oral anti-diabetic<br>drugs to control<br>3 IV infusions of 1-3 x 106<br>UC-MSC\/kg with an<br>interval of 1 week<br>4 patients with slight transient fever<br>8 patients respond to treatment (efficacy<br>group); these show: reduced fasting and<br>postprandial blood glucose levels, and by<br>trend increased plasma C-peptide levels<br>and Treg numbers<br>All patients had a feeling of well-being and<br>are more active<br>Zhao et al. 2013<br>NCT01415726<br>United States<br>Testing safety and efficacy of<br>Stem Cell Educator<br>therapy<br>Aged 29-68 years with<br>long-standing T2DM<br>Group A: oral medications<br>Stem Cell Educator<br>therapy: patient\u2019s blood<br>circulated through a<br>No AE, mild discomfort during venipunctures<br>Improved metabolic control and reduced<br>inflammation<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>45<br>n = 36<br>12 months<br>(n = 18)<br>Group B: oral medications<\/li><li>insulin injections (n =<br>11)<br>Group C: impaired \u03b2-cell<br>function with oral<br>medications + insulin<br>injections (n = 7)<br>closed-loop system that<br>separates lymphocytes<br>from the whole blood<br>and briefly co-cultures<br>them with adherent CBMSC<br>before returning<br>them to the patient\u2019s<br>circulation<br>Reduced HbA1C in groups A and B<br>Improved insulin sensitivity (HOMA-IR, 4<br>weeks)<br>Recovery of fasting C-peptide levels in Group<br>C (56 weeks) and HOMA of \u03b2-cell secretory<br>function\/C-peptide (12 weeks)<br>Improved serum TGF-\u03b2, reduced<br>CD86+CD14+ monocytes, no effect on<br>Treg numbers and restored Th1\/Th2\/Th3<br>cytokine balance (4 weeks)<br>Jiang et al. 2011<br>China<br>n = 10<br>6 months<br>Testing safety and effects of<br>placenta-derived MSC in<br>patients with longer<br>duration of disease<br>Aged 30-85 years<br>Duration of DM \u2265 3 years<br>Insulin requirement for<br>optimal glycemic control<br>of \u2265 0.7 IU\/kg\/day at<br>least for 1 year<br>3 IV infusions of 1.22-1.51<br>x 106\/kg placentaderived<br>MSC with an<br>interval of 1 month<br>No fever, chills, liver damage and other side<br>effects<br>Insulin and C-peptide levels increased<br>HbA1c decreased<br>Insulin requirement decreased, 4 of 10<br>patients achieved reduction of \u02c3 50%<br>Improved renal and cardiac function (no<br>details)<br>Abbreviations. ADA, American Diabetes Association; AE, adverse event; AUC, area under the curve; BM, bone marrow; BMI, body<br>mass index; CD, cluster of differentiation; DM, diabetes mellitus; GAD, glutamic acid decarboxylase; HbA1c, glycated hemoglobin A1c;<br>HOMA, homeostasis model assessment; HSC, hematopoietic stem cells; IDDM, insulin-dependent diabetes mellitus; IL, interleukin;<br>ICOS, inducible costimulator; ISL-1, insulin gene enhancer protein 1; IPF1, insulin promoter factor 1 (official name, PDX1, pancreatic<br>and duodenal homeobox 1); IR, insulin resistance; ISC, insulin secreting cell; IU, international unit; IV, intravenous; MNC, mononuclear<br>cells; MMTT, mixed-meal tolerance test; MPC, mesenchymal precursor cells; MSC, mesenchymal stem cells; PAX6, paired box<br>protein 6; T1DM, type 1 diabetes mellitus; T2DM, type 2 diabetes mellitus; TGF, transforming growth factor; Th, T helper cell; Treg,<br>regulatory T cell; UC, umbilical cord; WHO, world health organisation; WJ, Wharton&#8217;s Jelly.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>46<br>Table 2. Summary and comparison of SC in cell therapy of DM.<br>ESC iPSC MSC<br>Cell type and origin Embryonic SC<br>Inner cell mass of the blastocyst<br>Adult somatic cells<br>Reprogramming in vitro<br>Adult SC<br>Endosteal (BM) and perivascular niches (all<br>tissues)<br>Characteristics Pluripotent<br>Generates all germ layers:<br>ectoderm, endoderm and<br>mesoderm<br>Pluripotent<br>Generates all germ layers:<br>ectoderm, endoderm and<br>mesoderm<br>Multipotent<br>Generates mesenchymal lineages: bone,<br>cartilage, fat and muscle<br>Maintain HSC niche and hematopoiesis<br>Ethical concerns Use of embryos No No<br>Differentiation into<br>pancreatic \u03b2 cells<br>Yes<br>Yes<br>Insulin+ cells with limited secretory or<br>proliferative capacity (experimental)<br>Cell therapeutic options \u03b2-cell replacement \u03b2-cell replacement<br>Patient-specific cell lines<br>Secreted factors with immunomodulatory,<br>angiogenic and tissue regenerative properties<br>Advantages Large-scale production of<br>pancreatic endoderm, endocrine<br>progenitors and fully functional \u03b2-<br>cells<br>Large-scale production of<br>pancreatic endoderm, endocrine<br>progenitors and fully functional \u03b2-<br>cells<br>Easy isolation and in vitro expansion<br>Low immunogenicity allows allogenic<br>transplantation without immunosuppression<br>Minimal-invasive application<br>Clinical safe and well tolerated<br>Limitations Tumorigenic if incompletely<br>differentiated<br>Tumorigenic if incompletely<br>differentiated<br>Somatic mutations<br>Incomplete reprogramming<br>maintains somatic transcriptional<br>memory<br>ISCT minimal criteria for clinical MSC favor<br>expansion of nonclonal stromal cell-enriched<br>populations with varying proportions of true SC<br>Current clinical protocols are not standardized<br>and exhibit potential for improvements<br>Only a small proportion of systemically injected<br>cells engrafts in injured target tissues<br>Status First-in-man trial currently<br>investigates clinical safety and<br>efficacy of macroencapsulated<br>ESC-derived pancreatic<br>endoderm<br>Macroencapsulation avoids<br>Currently not safe enough for<br>clinical usage<br>Patient-specific cell lines allow<br>investigation of disease<br>processes in vitro and represent a<br>platform for drug testing<br>Completed clinical trials collectively report on<br>reduced requirement for exogenous insulin<br>Greatest benefit for patients with problems in<br>controlling glycemia by conventional therapy<br>More clinical trials in progress<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>47<br>tumorigenicity by preventing the<br>escape of embedded cells into the<br>body and allows easy graft<br>removal if necessary<br>Abbreviations. BM, bone marrow; DM, diabetes mellitus; HSC, hematopoietic stem cell; ISCT, International Society for Cell Therapy;<br>SC, stem cells.<br>ACCEPTED MANUSCRIPT<br>ACCEPTED MANUSCRIPT<br>48<br>Highlights<br>Large-scale production of pancreatic endoderm and \u03b2-cells from embryonic stem cells<br>First-in-man trial investigates macroencapsulated embryonic stem cell-derived \u03b2-cells<br>Induced pluripotent stem cells allow patient\/disease-specific cell lines<br>Mesenchymal stem cells secrete immunomodulatory and tissue regenerative factors<br>Transplanted mesenchymal stem cells ameliorate human type 1 and type 2 diabetes<\/li><\/ul>\n\n\n\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone size-full wp-image-3458\" src=\"http:\/\/dreambody.clinic\/wp-content\/uploads\/2020\/10\/Stem-cells-in-the-treatment-of-diabetes-mellitus-\u2013-focus-on-mesenchymal-stem-cells-1.jpg\" alt=\"Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem cells\" width=\"940\" height=\"788\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Stem cells in the treatment of diabetes mellitus \u2013 focus onmesenchymal stem cells Stem cells in the treatment of diabetes mellitus \u2013 focus onmesenchymal stem cells &#8211; G\u00fcnter P\u00e4th, Nikolaos Perakakis, Christos S. Mantzoros, JochenSeufertPII: S0026-0495(18)30215-4DOI: doi:10.1016\/j.metabol.2018.10.005Reference: YMETA 53824To appear in: MetabolismReceived date: 10 August 2018Accepted date: 14 October 2018Please cite this article as: G\u00fcnter&hellip;<\/p>\n","protected":false},"author":1,"featured_media":3455,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"rs_blank_template":"","rs_page_bg_color":"#ffffff","slide_template_v7":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-3451","page","type-page","status-publish","has-post-thumbnail","hentry","description-off"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.2 (Yoast SEO v27.6) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem cells - Dream Body Clinic Stem Cell Therapy Puerto Vallarta Mexico 2026 &amp; HGH<\/title>\n<meta name=\"description\" content=\"Stem cells in the treatment of diabetes mellitus \u2013 focus on mesenchymal stem cells. 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