Transplanted human bone marrow progenitor subtypes stimulate endogenous islet regeneration and revascularization

Stem cells therapy for diabetes: from past to future

Diabetes mellitus is a chronic disease of carbohydrate metabolism characterized by uncontrolled hyperglycemia due to the body's impaired ability to produce or respond to insulin. Oral or injectable exogenous insulin and its analogs cannot mimic endogenous insulin secreted by healthy individuals, and pancreatic and islet transplants face a severe shortage of sources and transplant complications, all of which limit the widespread use of traditional strategies in diabetes treatment. We are now in the era of stem cells and their potential in ameliorating human disease. At the same time, the rapid development of gene editing and cell-encapsulation technologies has added to the wings of stem cell therapy. However, there are still many unanswered questions before stem cell therapy can be applied clinically to patients with diabetes. In this review, we discuss the progress of strategies to obtain insulin-producing cells from different types of stem cells, the application of gene editing in stem cell therapy for diabetes, as well as summarize the current advanced cell encapsulation technologies in diabetes therapy and look forward to the future development of stem cell therapy in diabetes.

A Supportive Role of Mesenchymal Stem Cells on Insulin-Producing Langerhans Islets with a Specific Emphasis on The Secretome

Type 1 Diabetes (T1D) is a chronic autoimmune disease characterized by a gradual destruction of insulin-producing β-cells in the endocrine pancreas due to innate and specific immune responses, leading to impaired glucose homeostasis. T1D patients usually require regular insulin injections after meals to maintain normal serum glucose levels. In severe cases, pancreas or Langerhans islet transplantation can assist in reaching a sufficient β-mass to normalize glucose homeostasis. The latter procedure is limited because of low donor availability, high islet loss, and immune rejection. There is still a need to develop new technologies to improve islet survival and implantation and to keep the islets functional. Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells with high plasticity that can support human pancreatic islet function both in vitro and in vivo and islet co-transplantation with MSCs is more effective than islet transplantation alone in attenuating diabetes progression. The beneficial effect of MSCs on islet function is due to a combined effect on angiogenesis, suppression of immune responses, and secretion of growth factors essential for islet survival and function. In this review, various aspects of MSCs related to islet function and diabetes are described.

Efficiency of Bone Marrow-Derived Mesenchymal Stem Cells and Hesperetin in the Treatment of Streptozotocin-Induced Type 1 Diabetes in Wistar Rats

Type 1 diabetes mellitus (T1DM) was established to be ameliorated by islet transplantation, but the shortage of the transplanted human islet tissue and the use of immunosuppressive drugs to inhibit the rejection of allogeneic grafts make this type of therapy is limited. Nowadays, therapy with stem cells is one of the most promising future treatments. This kind of therapy could have a profound impact on both replacement, as well as regenerative therapies, to improve or even cure various disorders, including diabetes mellitus. Flavonoids have also been shown to possess anti-diabetic effects. Thus, this study aims to evaluate the effectiveness of the bone marrow-derived mesenchymal stem cells (BM-MSCs) and hesperetin in the treatment of a T1DM rat model. T1DM was induced in male Wistar rats that had been starved for 16 h via intraperitoneal injection of STZ at a dose of 40 mg/kg body weight (b.wt.). After 10 days of STZ injection, the diabetic rats were allocated into four groups. The first diabetic animal group was considered a diabetic control, while the other three diabetic animal groups were treated for six weeks, respectively, with hesperetin (given orally at a dose of 20 mg/kg b.wt.), BM-MSCs (injected intravenously at a dose of 1 × 10⁶ cells/rat/week), and their combination (hesperetin and BM-MSCs). The use of hesperetin and BM-MSCs in the treatment of STZ-induced diabetic animals significantly improved the glycemic state, serum fructosamine, insulin and C-peptide levels, liver glycogen content, glycogen phosphorylase, glucose-6-phosphatase activities, hepatic oxidative stress, and mRNA expressions of NF-κB, IL-1β, IL-10, P53, and Bcl-2 in pancreatic tissue. The study suggested the therapy with both hesperetin and BM-MSCs produced marked antihyperglycemic effects, which may be mediated via their potencies to ameliorate pancreatic islet architecture and insulin secretory response, as well as to decrease hepatic glucose output in diabetic animals. The improvement effects of hesperetin and BM-MSCs on the pancreatic islets of diabetic rats may be mediated via their antioxidant, anti-inflammatory, and antiapoptotic actions.

All the PNS is a Stage: Transplanted Bone Marrow Cells Play an Immunomodulatory Role in Peripheral Nerve Regeneration

SUMMARY STATEMENT

Bone marrow cell transplant has proven to be an effective therapeutic approach to treat peripheral nervous system injuries as it not only promoted regeneration and remyelination of the injured nerve but also had a potent effect on neuropathic pain.

The Therapeutic Potential of Mesenchymal Stem Cells in the Treatment of Diabetes Mellitus

Mesenchymal stem cells (MSCs) exist in many tissues and can differentiate into cells of multiple lineages, such as adipocytes, osteoblasts, or chondrocytes. MSC administration has demonstrated therapeutic potential in various degenerative and inflammatory diseases (e.g., graft-vs.-host disease, multiple sclerosis, Crohn's disease, organ fibrosis, and diabetes mellitus [DM]). The mechanisms involved in the therapeutic effects of MSCs are multifaceted. Generally, implanted MSCs can migrate to sites of injury, where they establish an anti-inflammatory and regenerative microenvironment in damaged tissues. In addition, MSCs can modulate innate and adaptive immune responses through immunosuppressive mechanisms that involve immune cells, inflammatory cytokines, chemokines, and immunomodulatory factors. DM has a high prevalence worldwide; it also contributes to a high rate of mortality worldwide. MSCs offer a promising therapeutic agent to prevent or repair damage from DM and diabetic complications through properties such as multilineage differentiation, homing, promotion of angiogenesis, and immunomodulation (e.g., prevention of oxidative stress, fibrosis, and cell death). In this study, we review current findings regarding the immunomodulatory and regenerative mechanisms of MSCs, as well as their therapeutic applications in DM and DM-related complications.

Regeneration of β-cells of the islet apparatus of the pancreas. Literature review

Diabetes of both type 1 and type 2 is characterized by a progressive loss of β-cell mass, which contributes to the disruption of glucose homeostasis. The optimal antidiabetic therapy would be simple replacement of lost cells, but at present, many researchers have shown that the pancreas (PZ) of adults has a limited regenerative potential. In this regard, significant efforts of researchers are directed to methods of inducing the proliferation of β-cells, stimulating the formation of β-cells from alternative endogenous sources and/or the generation of β-cells from pluripotent stem cells. Factors that regulate β-cell regeneration under physiological or pathological conditions, such as mediators, transcription factors, signaling pathways and potential pharmaceuticals, are also being intensively studied. In this review, we consider recent scientific studies carried out in the field of studying the development and regeneration of insulin-producing cells obtained from exogenous and endogenous sources and their use in the treatment of diabetes. The literature search while writing this review was carried out using the databases of the RSIC, CyberLeninka, Scopus, Web of Science, MedLine, PubMed for the period from 2005 to 2021. using the following keywords: diabetes mellitus, pancreas, regeneration, β-cells, stem cells, diabetes therapy.

Embryonic protein NODAL regulates the breast tumor microenvironment by reprogramming cancer-derived secretomes

The tumor microenvironment (TME) is an important mediator of breast cancer progression. Cancer-associated fibroblasts constitute a major component of the TME and may originate from tissue-associated fibroblasts or infiltrating mesenchymal stromal cells (MSCs). The mechanisms by which cancer cells activate fibroblasts and recruit MSCs to the TME are largely unknown, but likely include deposition of a pro-tumorigenic secretome. The secreted embryonic protein NODAL is clinically associated with breast cancer stage and promotes tumor growth, metastasis, and vascularization. Herein, we show that NODAL expression correlates with the presence of activated fibroblasts in human triple-negative breast cancers and that it directly induces Cancer-associated fibroblasts phenotypes. We further show that NODAL reprograms cancer cell secretomes by simultaneously altering levels of chemokines (e.g., CXCL1), cytokines (e.g., IL-6) and growth factors (e.g., PDGFRA), leading to alterations in MSC chemotaxis. We therefore demonstrate a hitherto unappreciated mechanism underlying the dynamic regulation of the TME.

Islet Regeneration: Endogenous and Exogenous Approaches

Both type 1 and type 2 diabetes are characterized by a progressive loss of beta cell mass that contributes to impaired glucose homeostasis. Although an optimal treatment option would be to simply replace the lost cells, it is now well established that unlike many other organs, the adult pancreas has limited regenerative potential. For this reason, significant research efforts are focusing on methods to induce beta cell proliferation (replication of existing beta cells), promote beta cell formation from alternative endogenous cell sources (neogenesis), and/or generate beta cells from pluripotent stem cells. In this article, we will review (i) endogenous mechanisms of beta cell regeneration during steady state, stress and disease; (ii) efforts to stimulate endogenous regeneration and transdifferentiation; and (iii) exogenous methods of beta cell generation and transplantation.

Ultrafiltration and Injection of Islet Regenerative Stimuli Secreted by Pancreatic Mesenchymal Stromal Cells

The secretome of mesenchymal stromal cells (MSCs) is enriched for biotherapeutic effectors contained within and independent of extracellular vesicles (EVs) that may support tissue regeneration as an injectable agent. We have demonstrated that the intrapancreatic injection of concentrated conditioned media (CM) produced by bone marrow MSC supports islet regeneration and restored glycemic control in hyperglycemic mice, ultimately providing a platform to elucidate components of the MSC secretome. Herein, we extend these findings using human pancreas-derived MSC (Panc-MSC) as "biofactories" to enrich for tissue regenerative stimuli housed within distinct compartments of the secretome. Specifically, we utilized 100 kDa ultrafiltration as a simple method to debulk protein mass and to enrich for EVs while concentrating the MSC secretome into an injectable volume for preclinical assessments in murine models of blood vessel and islet regeneration. EV enrichment (EV+) was validated using nanoscale flow cytometry and atomic force microscopy, in addition to the detection of classical EV markers CD9, CD81, and CD63 using label-free mass spectrometry. EV+ CM was predominately enriched with mediators of wound healing and epithelial-to-mesenchymal transition that supported functional regeneration in mesenchymal and nonmesenchymal tissues. For example, EV+ CM supported human microvascular endothelial cell tubule formation in vitro and enhanced the recovery of blood perfusion following intramuscular injection in nonobese diabetic/severe combined immunodeficiency mice with unilateral hind limb ischemia. Furthermore, EV+ CM increased islet number and β cell mass, elevated circulating insulin, and improved glycemic control following intrapancreatic injection in streptozotocin-treated mice. Collectively, this study provides foundational evidence that Panc-MSC, readily propagated from the subculture of human islets, may be utilized for regenerative medicine applications.

Quantitative Proteomics Evaluation of Human Multipotent Stromal Cell for β Cell Regeneration

Human multipotent stromal cells (hMSCs) are one of the most versatile cell types used in regenerative medicine due to their ability to respond to injury. In the context of diabetes, it has been previously shown that the regenerative capacity of hMSCs is donor specific after transplantation into streptozotocin (STZ)-treated immunodeficient mice. However, in vivo transplantation models to determine regenerative potency of hMSCs are lengthy, costly, and low throughput. Therefore, a high-throughput quantitative proteomics assay was developed to screen β cell regenerative potency of donor-derived hMSC lines. Using proteomics, we identified 16 proteins within hMSC conditioned media that effectively identify β cell regenerative hMSCs. This protein signature was validated using human islet culture assay, ELISA, and the potency was confirmed by recovery of hyperglycemia in STZ-treated mice. Herein, we demonstrated that quantitative proteomics can determine sample-specific protein signatures that can be used to classify previously uncharacterized hMSC lines for β cell regenerative clinical applications.

Mesenchymal stem cells to treat type 1 diabetes

What is clear is we are in the era of the stem cell and its potential in ameliorating human disease. Our perspective is generated from an in vivo model in a large animal that offers significant advantages (complete transplantation tolerance, large size and long life span). This review is an effort to meld our preclinical observations with others for the reader and to outline potential avenues to improve the present outlook for patients with diabetes. This effort exams the history or background of stem cell research in the laboratory and the clinic, types of stem cells, pluripotency or lack thereof based on a variety of pre-clinical investigations attempting endocrine pancreas recovery using stem cell transplantation. The focus is on the use of hematopoietic and mesenchymal stem cells. This review will also examine recent clinical experience following stem cell transplantation in patients with type 1 diabetes.

Peptide-modified methacrylated glycol chitosan hydrogels as a cell-viability supporting pro-angiogenic cell delivery platform for human adipose-derived stem/stromal cells

Cell-based therapies involving the injection of adipose-derived stem/stromal cells (ASCs) within rationally designed biomaterials are a promising approach for stimulating angiogenesis. With this focus, the current work explored the effects of incorporating integrin-binding RGD or IKVAV peptides within in situ-gelling N-methacrylate glycol chitosan (MGC) hydrogels on the response of encapsulated human ASCs. Initial studies focused on hydrogel characterization to validate that the MGC, MGC-RGD, and MGC-IKVAV hydrogels had similar biomechanical properties. ASC viability following encapsulation and culture under 2% O2 was significantly impaired in the MGC-IKVAV group relative to the MGC and MGC-RGD groups. In contrast, sustained viability, along with enhanced cell spreading and metabolic activity were observed in the MGC-RGD group. Investigation of angiogenic transcription suggested that the incorporation of the peptide groups did not substantially alter the pro-angiogenic gene expression profile of the encapsulated ASCs after 7 days of culture under 2% O2. Consistent with the in vitro findings, preliminary in vivo characterization following subcutaneous implantation into NOD/SCID mice showed that ASC retention was enhanced in the MGC-RGD hydrogels relative to the MGC-IKVAV group at 14 days. Further, the encapsulated ASCs in the MGC and MGC-RGD groups promoted murine CD31⁺ endothelial cell recruitment to the peri-implant region. Overall, the results indicate that the MGC-RGD and MGC hydrogels are promising platforms for ASC delivery, and suggest that strategies that support long-term ASC viability can augment in vivo angiogenesis through paracrine mechanisms. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 571-585, 2019.

Current Status of Stem Cell Treatment for Type I Diabetes Mellitus

BACKGROUND

Diabetes mellitus is a major health concern in current scenario which has been found to affect people of almost all ages. The disease has huge impact on global health; therefore, alternate methods apart from insulin injection are being explored to cure diabetes. Therefore, this review mainly focuses on the current status and therapeutic potential of stem cells mainly mesenchymal stem cells (MSCs) for Type 1 diabetes mellitus in preclinical animal models as well as humans.

METHODS

Current treatment for Type 1 diabetes mellitus mainly includes use of insulin which has its own limitations and also the underlying mechanism of diseases is still not explored. Therefore, alternate methods to cure diabetes are being explored. Stem cells are being investigated as an alternative therapy for treatment of various diseases including diabetes. Few preclinical studies have also been conducted using undifferentiated MSCs as well as in vitro MSCs differentiated into β islet cells.

RESULTS

These stem cell transplant studies have highlighted the benefits of MSCs, which have shown promising results. Few human trials using stem cells have also affirmed the potential of these cells in alleviating the symptoms.

CONCLUSION

Stem cell transplantation may prove to be a safe and effective treatment for patients with Type 1 diabetes mellitus.

Addressing Stem Cell Therapeutic Approaches in Pathobiology of Diabetes and Its Complications

High morbidity and mortality of diabetes mellitus (DM) throughout the human population is a serious threat which needs to be addressed cautiously. Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are most prevalent forms. Disruption in insulin regulation and resistance leads to increased formation and accumulation of advanced end products (AGEs), which further enhance oxidative and nitrosative stress leading to microvascular (retinopathy, neuropathy, and nephropathy) and macrovascular complications. These complications affect the normal function of organ and tissues and may cause life-threatening disorders, if hyperglycemia persists and improperly controlled. Current and traditional treatment procedures are only focused on to regulate the insulin level and do not cure the diabetic complications. Pancreatic transplantation seemed a viable alternative; however, it is limited due to lack of donors. Cell-based therapy such as stem cells is considered as a promising therapeutic agent against DM and diabetic complications owing to their multilineage differentiation and regeneration potential. Previous studies have demonstrated the various impacts of both pluripotent and multipotent stem cells on DM and its micro- and macrovascular complications. Therefore, this review summarizes the potential of stem cells to treat DM and its related complications.

Proteomic characterisation reveals active Wnt-signalling by human multipotent stromal cells as a key regulator of beta cell survival and proliferation

AIMS/HYPOTHESIS

Novel strategies to stimulate the expansion of beta cell mass in situ are warranted for diabetes therapy. The aim of this study was to elucidate the secretome of human bone marrow (BM)-derived multipotent stromal cells (MSCs) with documented islet regenerative paracrine function. We hypothesised that regenerative MSCs will secrete a unique combination of protein factors that augment islet regeneration.

METHODS

Human BM-derived MSCs were examined for glucose-lowering capacity after transplantation into streptozotocin-treated NOD/severe combined immunodeficiency (SCID) mice and segregated into samples with regenerative (MSC^R) vs nonregenerative (MSC^NR) capacity. Secreted proteins associated with islet regenerative function were identified using stable isotope labelling with amino acids in cell culture (SILAC)-based quantitative proteomics. To functionally validate the importance of active Wnt signalling, we stimulated the Wnt-signalling pathway in MSC^NR samples during ex vivo expansion using glycogen synthase kinase 3 (GSK3) inhibition (CHIR99201), and the conditioned culture media (CM) generated was tested for the capacity to support cultured human islet cell survival and proliferation in vitro.

RESULTS

MSC^R showed increased secretion of proteins associated with cell growth, matrix remodelling, immunosuppressive and proangiogenic properties. In contrast, MSC^NR uniquely secreted proteins known to promote inflammation and negatively regulate angiogenesis. Most notably, MSC^R maintained Wnt signalling via Wnt5A/B (~2.5-fold increase) autocrine activity during ex vivo culture, while MSC^NR repressed Wnt signalling via Dickkopf-related protein (DKK)1 (~2.5-fold increase) and DKK3 secretion. Inhibition of GSK3 activity in MSC^NR samples increased the accumulation of nuclear β-catenin and generated CM that augmented beta cell survival (13% increases) and proliferation when exposed to cultured human islets.

CONCLUSIONS/INTERPRETATION

Maintenance of active Wnt signalling within human MSCs promotes the secretion of matricellular and proangiogenic proteins that formulate a niche for islet regeneration.

Stromal Vascular Fraction Loaded Silk Fibroin Mats Effectively Support the Survival of Diabetic Mice after Pancreatic Islet Transplantation

The aim of this study is to assess whether stromal vascular fraction (SVF)-soaked silk fibroin nonwoven mats (silk-SVF) can preserve the functionality of encapsulated pancreatic endocrine cells (alginate-PECs) after transplantation in the subcutaneous tissue of diabetic mice. Silk scaffolds are selected to create an effective 3D microenvironment for SVF delivery in the subcutaneous tissue before diabetes induction: silk-SVF is subcutaneously implanted in the dorsal area of five healthy animals; after 15 d, mice are treated with streptozotocin to induce diabetes and then alginate-PECs are implanted on the silk-SVF. All animals appear in good health, increasing weight during time, and among them, one presents euglycemia until the end of experiments. On the contrary, when PECs are simultaneously implanted with SVF after diabetes induction, mice are euthanized due to suffering. This work clearly demonstrates that silk-SVF creates a functional niche in subcutaneous tissue and preserves endocrine cell survival and engraftment.

Mesenchymal stromal cells ameliorate oxidative stress-induced islet endothelium apoptosis and functional impairment via Wnt4-β-catenin signaling

Background

Islet dysfunction and destruction are the common cause for both type 1 and type 2 diabetes mellitus (T2DM). The islets of Langerhans are highly vascularized miniorgans, and preserving the structural integrity and full function of the microvascular endothelium is vital for protecting the islets from the infiltration of immune cells and secondary inflammatory attack. Mesenchymal stromal cell (MSC)-based therapies have been proven to promote angiogenesis of the islets; however, the underlying mechanism for the protective role of MSCs in the islet endothelium is still vague.

Methods

In this study, we used MS-1, a murine islet microvascular endothelium cell line, and an MSC-MS1 transwell culturing system to investigate the protective mechanism of rat bone marrow-derived MSCs under oxidative stress in vitro. Cell apoptosis was detected by TUNEL staining, annexin V/PI flow cytometry analysis, and cleaved caspase 3 western blotting analysis. Endothelial cell activation was determined by expression of intercellular cell adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), as well as eNOS phosphorylation/activation. The changes of VCAM-1, eNOS, and the β-catenin expression were also tested in the isolated islets of T2DM rats infused with MSCs.

Results

We observed that treating MS-1 cells with H₂O₂ triggered significant apoptosis, induction of VCAM expression, and reduction of eNOS phosphorylation. Importantly, coculturing MS-1 cells with MSCs prevented oxidative stress-induced apoptosis, eNOS inhibition, and VCAM elevation in MS-1 cells. Similar changes in VCAM-1 and eNOS phosphorylation could also be observed in the islets isolated from T2DM rats infused with MSCs. Moreover, MSCs cocultured with MS-1 in vitro or their administration in vivo could both result in an increase of β-catenin, which suggested activation of the β-catenin-dependent Wnt signaling pathway. In MS-1 cells, activation of the β-catenin-dependent Wnt signaling pathway partially mediated the protective effects of MSCs against H₂O₂-induced apoptosis and eNOS inhibition. Furthermore, MSCs produced a significant amount of Wnt4 and Wnt5a. Although both Wnt4 and Wnt5a participated in the interaction between MSCs and MS-1 cells, Wnt4 exhibited a protective role while Wnt5a seemed to show a destructive role in MS-1 cells.

Conclusions

Our observations provide evidence that the orchestration of the MSC-secreted Wnts could promote the survival and improve the endothelial function of the injured islet endothelium via activating the β-catenin-dependent Wnt signaling in target endothelial cells. This finding might inspire further in-vivo studies.

Stem cells to restore insulin production and cure diabetes

BACKGROUND

The advancement of knowledge in the field of regenerative medicine is increasing the therapeutic expectations of patients and clinicians on cell therapy approaches. Within these, stem cell therapies are often evoked as a possible therapeutic option for diabetes, already ongoing or possible in the near future.

AIM

The purpose of this document is to make a point of the situation on existing knowledge and therapies with stem cells to treat patients with diabetes by focusing on some of the aspects that most frequently raise curiosity and discussion in clinical practice and in the interaction with the patient. In fact, at present there are no clinically approved treatments based on the use of stem cells for the treatment of diabetes, but several therapeutic approaches have already been evaluated or are being evaluated in clinical trials.

DATA SYNTHESIS

It is possible to identify three large potential application fields: 1) the reconstruction of the β cell mass; 2) the immunomodulation in type 1 diabetes (T1D); 3) the treatment of complications. In this study we will limit the discussion to approaches that have the potential for clinical translation, deliberately omitting aspects of basic biology and preclinical data. Also, we intentionally omit the treatment of the complications that will be the subject of a future document. Finally, an overview of the Italian situation regarding the storage of cord blood cells for the therapy of diabetes will be given.

Intravenous Infusion of Human Adipose Tissue-Derived Mesenchymal Stem Cells to Treat Type 1 Diabetic Mellitus in Mice: An Evaluation of Grafted Cell Doses

Mesenchymal stem cell (MSC) transplantation is a novel treatment for diabetes mellitus, especially type 1 diabetes. Many recent publications have demonstrated the efficacy of MSC transplantation on reducing blood glucose and increasing insulin production in both preclinical and clinical trials. However, the investigation of grafted cell doses has been lacking. Therefore, this study aimed to evaluate the different doses of MSCs on treatment of type 1 diabetes in mouse models. MSCs were isolated and expanded from human adipose tissue. Streptozotocin (STZ)-induced diabetic mice were divided into two groups that were intravenously transfused with two different doses of human MSCs: 10⁶ or 2.10⁶ cells/mouse. After transplantation, both grafted and placebo mice were monitored weekly for their blood glucose levels, glucose and insulin tolerance, pancreatic structural changes, and insulin production for 56 days after transplantation. The results showed that the higher dose of MSCs (2.10⁶ cells/mouse) remarkably reduced death rate. The death rates were 50%, 66%, and 0% in placebo group, low-dose (1.10⁶ MSCs) group, and high-dose (2.10⁶ MSCs) group, respectively, after 56 days of treatment. Moreover, blood glucose levels were lower for the high-dose group compared to other groups. Glucose and insulin tolerance, as well as insulin production, were significantly improved in mice transplanted with 2.10⁶ cells. The histochemical analyses also support these results. Thus, a higher (e.g., 2.10⁶) dose of MSCs may be an effective dose for treatment of type 1 diabetes mellitus.

Adipose-derived mesenchymal stem cells ameliorate hyperglycemia through regulating hepatic glucose metabolism in type 2 diabetic rats

Infusion of mesenchymal stem cells (MSCs) has been identified in the rapid alleviation in hyperglycemia of diabetic individuals, but the mechanism involved has not been adequately explained by these cells' potential role in modulating system insulin sensitivity and islet regeneration. In this study, we demonstrated adipose-derived mesenchymal stem cells (ASCs) produced significantly lower blood glucose via promoting hepatic glycogen synthesis and inhibiting hepatic glucose production within 24 h after infusion in T2DM rats. In vitro, HepG2 cells treated with palmitate (PA) were used as a model of hepatic glucose metabolism disorder to confirm that ASCs stimulates the phosphorylation of hepatic AMP-activated protein kinase (AMPK) to restores hepatic glucose metabolism in type 2 diabetes. In summary, this study indicated that ASCs improve hyperglycemia via regulating hepatic glucose metabolism. Additionally, the effect of ASCs on hepatic glucose metabolism depended on the AMPK signaling pathway. Thus, this is the new research of the molecular mechanisms of MSCs administration to improve glucose metabolism, and it may indicate a new treatment target of MSCs in T2DM.

Intravenous vs intraperitoneal transplantation of umbilical cord mesenchymal stem cells from Wharton's jelly in the treatment of streptozotocin-induced diabetic rats

AIM

To evaluate the efficiency of mesenchymal stem cells isolated from Wharton's jelly (WJ-MSCs) through either the intravenous or intraperitoneal transplantations into streptozotocin (STZ)-induced diabetic rats as a therapy for type 1 diabetes mellitus (T1DM).

METHODOLOGY

A rat model with STZ induction was established and the rats were divided into 3 groups: a tail vein injection group, an intraperitoneal injection group and a STZ control group. Following transplantation, blood glucose levels were monitored weekly then the pancreatic tissues were collected to examine the pancreatic islets by histopathology and morphometric studies.

RESULTS

Intravenous transplantation of WJ-MSCs ameliorated hyperglycemia at day 7 after transplantation, with sustained decreased fasting blood glucose (FBG) levels until day 56. Further, these cells ameliorated at least partially the damage induced by STZ in the pancreas and produced a similar morphology to normal islets. On the contrary, intraperitoneal transplantation of WJ-MSCs failed to maintain normoglycemia or ameliorate the damaged pancreas in STZ-injected rats.

CONCLUSION

These findings conclude that the intravenous administration method was effective in transplanting WJ-MSCs for the treatment of T1DM, whereas the intraperitoneal transplantation showed no therapeutic effect in our animal experiments.

Role of stem cells during diabetic liver injury

Diabetes mellitus is one of the most severe endocrine metabolic disorders in the world that has serious medical consequences with substantial impacts on the quality of life. Type 2 diabetes is one of the main causes of diabetic liver diseases with the most common being non-alcoholic fatty liver disease. Several factors that may explain the mechanisms related to pathological and functional changes of diabetic liver injury include: insulin resistance, oxidative stress and endoplasmic reticulum stress. The realization that these factors are important in hepatocyte damage and lack of donor livers has led to studies concentrating on the role of stem cells (SCs) in the prevention and treatment of liver injury. Possible avenues that the application of SCs may improve liver injury include but are not limited to: the ability to differentiate into pancreatic β-cells (insulin producing cells), the contribution for hepatocyte regeneration, regulation of lipogenesis, glucogenesis and anti-inflammatory actions. Once further studies are performed to explore the underlying protective mechanisms of SCs and the advantages and disadvantages of its application, there will be a greater understand of the mechanism and therapeutic potential. In this review, we summarize the findings regarding the role of SCs in diabetic liver diseases.

Effect and mechanisms of human Wharton's jelly-derived mesenchymal stem cells on type 1 diabetes in NOD model

Type 1 diabetes is an autoimmune disease that results from an inflammatory destruction of β-cells in islets. Mesenchymal stem cells derived from Wharton's jelly (WJ-MSCs) own a peculiar immunomodulatory feature and might reverse the inflammatory destruction and repair the function of β-cells. Sixty NOD mice were divided into four groups, including normal control group, WJ-MSCs prevention group (before onset), WJ-MSCs treatment group (after onset), and diabetic control group. After homologous therapy, onset time of diabetes, levels of fasting plasma glucose (FPG), fed blood glucose and C-peptide, regulation of cytokines, and islet cells were examined and evaluated. After WJ-MSCs infusion, FPG and fed blood glucose in WJ-MSCs treatment group decreased to normal level in 6-8 days and maintained for 6 weeks. Level of fasting C-peptide of these mice was higher compared to diabetic control mice (P=0.027). In WJ-MSCs prevention group, WJ-MSCs played a protective role for 8-week delayed onset of diabetes, and fasting C-peptide in this group was higher compared to the other two diabetic groups (P=0.013, 0.035). Compared with diabetic control group, frequencies of CD4+CD25+Foxp3+ Tregs in WJ-MSCs prevention group and treatment group were higher, while levels of IL-2, IFN-γ, and TNF-α were lower (P<0.001); the degree of insulitis was also depressed, especially for WJ-MSCs prevention group (P<0.05). Infusion of WJ-MSCs could aid in T1DM through regulation of the autoimmunity and recovery of islet β-cells no matter before or after onset of T1DM. WJ-MSCs might be an effective method for T1DM.

Clinical-scale in vitro expansion preserves biological characteristics of cardiac atrial appendage stem cells

OBJECTIVES

Cardiac atrial appendage stem cells (CASCs) have recently emerged as an attractive candidate for cardiac regeneration after myocardial infarction. As with other cardiac stem cells, CASCs have to be expanded ex vivo to obtain clinically relevant cell numbers. However, foetal calf serum (FCS), which is routinely used for cell culturing, is unsuitable for clinical purposes, and influence of long-term in vitro culture on CASC behaviour is unknown.

MATERIALS AND METHODS

We examined effects on CASC biology of prolonged expansion, and evaluated a culture protocol suitable for human use.

RESULTS

In FCS-supplemented medium, CASCs could be kept in culture for 55.75 ± 3.63 days, before reaching senescence. Despite a small reduction in numbers of proliferating CASCs (1.37 ± 0.52% per passage) and signs of progressive telomere shortening (0.04 ± 0.02 kb per passage), their immunophenotype and myocardial differentiation potential remained unaffected during the entire culture period. The cells were successfully expanded in human platelet plasma supernatant, while maintaining their biological properties.

CONCLUSIONS

We successfully developed a protocol for long-term culture, to obtain clinically relevant CASC numbers, while retaining their cardiogenic potential. These insights in CASC biology and optimization of a humanized platelet-based culture method are an important step towards clinical application of CASCs for cardiac regenerative medicine.

Endothelial cells mediate islet-specific maturation of human embryonic stem cell-derived pancreatic progenitor cells

It is well recognized that in vitro differentiation of embryonic stem cells (ESC) can be best achieved by closely recapitulating the in vivo developmental niche. Thus, implementation of directed differentiation strategies has yielded encouraging results in the area of pancreatic islet differentiation. These strategies have concentrated on direct addition of chemical signals, however, other aspect of the developmental niche are yet to be explored. During development, pancreatic progenitor (PP) cells grow as an epithelial sheet, which aggregates with endothelial cells (ECs) during the final stages of maturation. Several findings suggest that the interactions with EC play a role in pancreatic development. In this study, we recapitulated this phenomenon in an in vitro environment by maturing the human ESC (hESC)-derived PP cells in close contact with ECs. We find that co-culture with different ECs (but not fibroblast) alone results in pancreatic islet-specific differentiation of hESC-derived PP cells even in the absence of additional chemical induction. The differentiated cells responded to exogenous glucose levels by enhanced C-peptide synthesis. The co-culture system aligned well with endocrine development as determined by comprehensive analysis of involved signaling pathways. By recapitulating cell-cell interaction aspects of the developmental niche we achieved a differentiation model that aligns closely with islet organogenesis.

Mesenchymal stem cell therapy ameliorates diabetic hepatocyte damage in mice by inhibiting infiltration of bone marrow-derived cells

Although mesenchymal stem cells (MSCs) have been implicated in hepatic injury, the mechanism through which they contribute to diabetic liver disease has not been clarified. In this study, we investigated the effects of MSC therapy on diabetic liver damage with a focus on the role of bone-marrow-derived cells (BMDCs), which infiltrate the liver, and elucidated the mechanism mediating this process. Rat bone-marrow (BM)-derived MSCs were administered to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. MSC-conditioned medium (MSC-CM) was also administered to examine the trophic effects of MSCs on liver damage. Therapeutic effects of MSCs were analyzed by assessing serum liver enzyme levels and histological findings. Kinetic and molecular profiles of BMDCs in the liver were evaluated using BM-chimeric mice. Curative effects of MSC and MSC-CM therapies were similar because both ameliorated the aggravation of aspartate aminotransferase and alanine aminotransferase at 8 weeks of treatment, despite persistent hyperlipidemia and hyperinsulinemia in HFD-diabetic mice and persistent hyperglycemia in STZ-diabetic mice. Furthermore, both therapies suppressed the abnormal infiltration of BMDCs into the liver, reversed excessive expression of proinflammatory cytokines in parenchymal cells, and regulated proliferation and survival signaling in the liver in both HFD- and STZ-diabetic mice. In addition to inducing hepatocyte regeneration in STZ-diabetic mice, both therapies also prevented excessive lipid accumulation and apoptosis of hepatocytes and reversed insulin resistance (IR) in HFD-diabetic mice.

CONCLUSION

MSC therapy is a powerful tool for repairing diabetic hepatocyte damage by inhibiting inflammatory reactions induced by BMDCs and IR. These effects are likely the result of humoral factors derived from MSCs.

Survival of free and encapsulated human and rat islet xenografts transplanted into the mouse bone marrow

Bone marrow was recently proposed as an alternative and potentially immune-privileged site for pancreatic islet transplantation. The aim of the present study was to assess the survival and rejection mechanisms of free and encapsulated xenogeneic islets transplanted into the medullary cavity of the femur, or under the kidney capsule of streptozotocin-induced diabetic C57BL/6 mice. The median survival of free rat islets transplanted into the bone marrow or under the kidney capsule was 9 and 14 days, respectively, whereas that of free human islets was shorter, 7 days (bone marrow) and 10 days (kidney capsule). Infiltrating CD8⁺ T cells and redistributed CD4⁺ T cells, and macrophages were detected around the transplanted islets in bone sections. Recipient mouse splenocytes proliferated in response to donor rat stimulator cells. One month after transplantation under both kidney capsule or into bone marrow, encapsulated rat islets had induced a similar degree of fibrotic reaction and still contained insulin positive cells. In conclusion, we successfully established a small animal model for xenogeneic islet transplantation into the bone marrow. The rejection of xenogeneic islets was associated with local and systemic T cell responses and macrophage recruitment. Although there was no evidence for immune-privilege, the bone marrow may represent a feasible site for encapsulated xenogeneic islet transplantation.

Transplantation of human menstrual blood progenitor cells improves hyperglycemia by promoting endogenous progenitor differentiation in type 1 diabetic mice

Recently, a unique population of progenitor cells was isolated from human menstrual blood. The human menstrual blood progenitor cells (MBPCs) possess many advantages, such as the noninvasive acquisition procedure, broad multipotency, a higher proliferative rate, and low immunogenicity, and have attracted extensive attention in regenerative medicine. Preclinical studies to test the safety and efficacy of MBPCs have been underway in several animal models. However, relevant studies in type 1 diabetes mellitus (T1DM) have not yet been proceeded. Herein, we studied the therapeutic effect of MBPCs and the mechanism of β-cell regeneration after MBPC transplantation in the T1DM model. Intravenous injection of MBPCs can reverse hyperglycemia and weight loss, prolong lifespan, and increase insulin production in diabetic mice. Histological and immunohistochemistry analyses indicated that T1DM mice with MBPC transplantation recovered islet structures and increased the β-cell number. We further analyzed in vivo distribution of MBPCs and discovered that a majority of MBPCs migrated into damaged pancreas and located at the islet, duct, and exocrine tissue. MBPCs did not differentiate into insulin-producing cells, but enhanced neurogenin3 (ngn3) expression, which represented endocrine progenitors that were activated. Ngn3(+) cells were not only in the ductal epithelium, but also in the islet and exocrine tissue. We analyzed a series of genes associated with the embryonic mode of β-cell development by real-time polymerase chain reaction and the results showed that the levels of those gene expressions all increased after cell transplantation. According to the results, we concluded that MBPCs stimulated β-cell regeneration through promoting differentiation of endogenous progenitor cells.

Effect of combined therapy of human Wharton's jelly-derived mesenchymal stem cells from umbilical cord with sitagliptin in type 2 diabetic rats

Type 2 diabetes mellitus is the most common endocrine disease all over the world, while existing therapies can only ameliorate hyperglycemia or temporarily improve the response to insulin in target tissues, they cannot retard or improve the progressive β-cell dysfunction persistently. Combined therapy of stem cells and sitagliptin might resolve this problem, we verified this hypothesis in a diabetic rat model. Except ten Wistar rats in normal control group, diabetic rats were divided into diabetic control group, WJ-MSCs group, sitagliptin group and WJ-MSCs + sitagliptin group and received homologous therapy. Ten weeks after therapy, diabetic symptoms, FPG and GHbA1c in WJ-MSCs group, sitagliptin group and WJ-MSCs + sitagliptin group were significantly less than those in diabetic control group (P < 0.05), while fasting C-peptide and number of β cells in WJ-MSCs group and WJ-MSCs + sitagliptin group was significantly higher than those in diabetic control and sitagliptin group (P < 0.01). Glucagon and number of α cells in sitagliptin group and WJ-MSCs + sitagliptin group were significantly lower than those in WJ-MSCs group and diabetic control group (P < 0.01). No symptoms of rejection and toxic effect were observed. Combined therapy of WJ-MSCs and sitagliptin can effectively ameliorate hyperglycemia, promote regeneration of islet β cells and suppress generation of islet α cells in diabetic rats, presenting a new therapy for type 2 diabetes although the exact mechanisms are unclear.

Making surrogate β-cells from mesenchymal stromal cells: perspectives and future endeavors

Generation of surrogate β-cells is the need of the day to compensate the short supply of islets for transplantation to diabetic patients requiring daily shots of insulin. Over the years several sources of stem cells have been claimed to cater to the need of insulin producing cells. These include human embryonic stem cells, induced pluripotent stem cells, human perinatal tissues such as amnion, placenta, umbilical cord and postnatal tissues involving adipose tissue, bone marrow, blood monocytes, cord blood, dental pulp, endometrium, liver, labia minora dermis-derived fibroblasts and pancreas. Despite the availability of such heterogonous sources, there is no substantial breakthrough in selecting and implementing an ideal source for generating large number of stable insulin producing cells. Although the progress in derivation of β-cell like cells from embryonic stem cells has taken a greater leap, their application is limited due to controversy surrounding the destruction of human embryo and immune rejection. Since multipotent mesenchymal stromal cells are free of ethical and immunological complications, they could provide unprecedented opportunity as starting material to derive insulin secreting cells. The main focus of this review is to discuss the merits and demerits of MSCs obtained from human peri- and post-natal tissue sources to yield abundant glucose responsive insulin producing cells as ideal candidates for prospective stem cell therapy to treat diabetes.

The use of stem cells for pancreatic regeneration in diabetes mellitus

The endocrine pancreas represents an interesting arena for regenerative medicine and cell therapeutics. One of the major pancreatic diseases, diabetes mellitus is a metabolic disorder caused by having an insufficient number of insulin-producing β cells. Replenishment of β cells by cell transplantation can restore normal metabolic control. The shortage in donor pancreata has meant that the demand for transplantable β cells has outstripped the supply, which could be met by using alternative sources of stem cells. This situation has opened up new areas of research, such as cellular reprogramming and in vivo β-cell regeneration. Pluripotent stem cells seem to be the best option for clinical applications of β-cell regeneration in the near future, as these cells have been demonstrated to represent an unlimited source of functional β cells. Although compelling evidence shows that the adult pancreas retains regenerative capacity, it remains unclear whether this organ contains stem cells. Alternatively, specialized cell types within or outside the pancreas retain plasticity in proliferation and differentiation. Cellular reprogramming or transdifferentiation of exocrine cells or other types of endocrine cells in the pancreas could provide a long-term solution.

Electrofusion of mesenchymal stem cells and islet cells for diabetes therapy: a rat model

Islet transplantation is a minimally invasive treatment for severe diabetes. However, it often requires multiple donors to accomplish insulin-independence and the long-term results are not yet satisfying. Therefore, novel ways to overcome these problems have been explored. Isolated islets are fragile and susceptible to pro-apoptotic factors and poorly proliferative. In contrast, mesenchymal stem cells (MSCs) are highly proliferative, anti-apoptotic and pluripotent to differentiate toward various cell types, promote angiogenesis and modulate inflammation, thereby studied as an enhancer of islet function and engraftment. Electrofusion is an efficient method of cell fusion and nuclear reprogramming occurs in hybrid cells between different cell types. Therefore, we hypothesized that electrofusion between MSC and islet cells may yield robust islet cells for diabetes therapy. We establish a method of electrofusion between dispersed islet cells and MSCs in rats. The fusion cells maintained glucose-responsive insulin release for 20 days in vitro. Renal subcapsular transplantation of fusion cells prepared from suboptimal islet mass (1,000 islets) that did not correct hyperglycemia even if co-transplanted with MSCs, caused slow but consistent lowering of blood glucose with significant weight gain within the observation period in streptozotocin-induced diabetic rats. In the fusion cells between rat islet cells and mouse MSCs, RT-PCR showed new expression of both rat MSC-related genes and mouse β-cell-related genes, indicating bidirectional reprogramming of both β-cell and MSCs nuclei. Moreover, decreased caspase3 expression and new expression of Ki-67 in the islet cell nuclei suggested alleviated apoptosis and gain of proliferative capability, respectively. These results show that electrofusion between MSCs and islet cells yield special cells with β-cell function and robustness of MSCs and seems feasible for novel therapeutic strategy for diabetes mellitus.

Stem cell therapy to cure type 1 diabetes: from hype to hope

Type 1 diabetes mellitus (T1D) is a chronic, multifactorial autoimmune disease that involves the progressive destruction of pancreatic β-cells, ultimately resulting in the loss of insulin production and secretion. The goal of clinical intervention is to prevent or arrest the onset and progression of autoimmunity, reverse β-cell destruction, and restore glycometabolic and immune homeostasis. Despite promising outcomes observed with islet transplantation and advancements in immunomodulatory therapies, the need for an effective cell replacement strategy for curing T1D still persists. Stem cell therapy offers a solution to the cited challenges of islet transplantation. While the regenerative potential of stem cells can be harnessed to make available a self-replenishing supply of glucose-responsive insulin-producing cells, their immunomodulatory properties may potentially be used to prevent, arrest, or reverse autoimmunity, ameliorate innate/alloimmune graft rejection, and prevent recurrence of the disease. Herein, we discuss the therapeutic potential of stem cells derived from a variety of sources for the cure of T1D, for example, embryonic stem cells, induced pluripotent stem cells, bone marrow-derived hematopoietic stem cells, and multipotent mesenchymal stromal cells derived from bone marrow, umbilical cord blood, and adipose tissue. The benefits of combinatorial approaches designed to ensure the successful clinical translation of stem cell therapeutic strategies, such as approaches combining effective stem cell strategies with islet transplantation, immunomodulatory drug regimens, and/or novel bioengineering techniques, are also discussed. To conclude, the application of stem cell therapy in the cure for T1D appears extremely promising.

Characterization of cardiac-resident progenitor cells expressing high aldehyde dehydrogenase activity

High aldehyde dehydrogenase (ALDH) activity has been associated with stem and progenitor cells in various tissues. Human cord blood and bone marrow ALDH-bright (ALDH(br)) cells have displayed angiogenic activity in preclinical studies and have been shown to be safe in clinical trials in patients with ischemic cardiovascular disease. The presence of ALDH(br) cells in the heart has not been evaluated so far. We have characterized ALDH(br) cells isolated from mouse hearts. One percent of nonmyocytic cells from neonatal and adult hearts were ALDH(br). ALDH(very-br) cells were more frequent in neonatal hearts than adult. ALDH(br) cells were more frequent in atria than ventricles. Expression of ALDH1A1 isozyme transcripts was highest in ALDH(very-br) cells, intermediate in ALDH(br) cells, and lowest in ALDH(dim) cells. ALDH1A2 expression was highest in ALDH(very-br) cells, intermediate in ALDH(dim) cells, and lowest in ALDH(br) cells. ALDH1A3 and ALDH2 expression was detectable in ALDH(very-br) and ALDH(br) cells, unlike ALDH(dim) cells, albeit at lower levels compared with ALDH1A1 and ALDH1A2. Freshly isolated ALDH(br) cells were enriched for cells expressing stem cell antigen-1, CD34, CD90, CD44, and CD106. ALDH(br) cells, unlike ALDH(dim) cells, could be grown in culture for more than 40 passages. They expressed sarcomeric α -actinin and could be differentiated along multiple mesenchymal lineages. However, the proportion of ALDH(br) cells declined with cell passage. In conclusion, the cardiac-derived ALDH(br) population is enriched for progenitor cells that exhibit mesenchymal progenitor-like characteristics and can be expanded in culture. The regenerative potential of cardiac-derived ALDH(br) cells remains to be evaluated.

Long term effects of the implantation of Wharton's jelly-derived mesenchymal stem cells from the umbilical cord for newly-onset type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is an autoimmune disorder resulted from T cell-mediated destruction of pancreatic β-cells, how to regenerate β-cells and prevent the autoimmune destruction of remnant and neogenetic β-cells is a tough problem. Immunomodulatory propertity of mesenchymal stem cell make it illuminated to overcome it. We assessed the long-term effects of the implantation of Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) from the umbilical cord for Newly-onset T1DM. Twenty-nine patients with newly onset T1DM were randomly divided into two groups, patients in group I were treated with WJ-MSCs and patients in group II were treated with normal saline based on insulin intensive therapy. Patients were followed-up after the operation at monthly intervals for the first 3 months and thereafter every 3 months for the next 21 months, the occurrence of any side effects and results of laboratory examinations were evaluated. There were no reported acute or chronic side effects in group I compared with group II, both the HbA1c and C peptide in group I patients were significantly better than either pretherapy values or group II patients during the follow-up period. These data suggested that the implantation of WJ-MSCs for the treatment of newly-onset T1DM is safe and effective. This therapy can restore the function of islet β cells in a longer time, although precise mechanisms are unknown, the implantation of WJ-MSCs is expected to be an effective strategy for treatment of type1 diabetes.

Harnessing the immunomodulatory and tissue repair properties of mesenchymal stem cells to restore β cell function

Islet cell transplantation has therapeutic potential to cure type 1 diabetes (T1D), which is characterized by autoimmune-mediated destruction of insulin-producing β cells. However, current success rates are limited by long-term decline in islet graft function resulting partially from poor revascularization and immune destruction. Mesenchymal stem cells (MSCs) have the potential to enhance islet transplantation and prevent disease progression by a multifaceted approach. MSCs have been shown to be effective at inhibiting inflammatory-mediated immune responses and at promoting tissue regeneration. The immunomodulatory and tissue repairing properties of MSCs may benefit β cell regeneration in the context of T1D. This review will elucidate how MSCs can minimize β cell damage by providing survival signals and simultaneously modulate the immune response by inhibiting activation, and proliferation of several immune cell types. In addition, MSCs can enhance islet graft revascularization, maintaining long-term β cell viability and function.

Intrapancreatic delivery of human umbilical cord blood aldehyde dehydrogenase-producing cells promotes islet regeneration

AIMS/HYPOTHESIS

We sought to investigate the stimulation of islet regeneration by transplanted human umbilical cord blood (UCB) cells purified according to high aldehyde dehydrogenase (ALDH) activity (ALDH(hi)), a conserved characteristic of multiple progenitor lineages. We hypothesised that direct intrapancreatic (iPan) delivery of ALDH(hi) progenitors would augment islet regeneration via timely and localised exposure to islet-regenerative stimuli.

METHODS

Cells were purified from UCB based on flow cytometry for low ALDH activity (ALDH(lo)) vs ALDH(hi). UCB ALDH(lo) or ALDH(hi) cells were compared for surface marker expression, as well as haematopoietic, endothelial and multipotent stromal progenitor content in vitro. UCB ALDH(lo) or ALDH(hi) cells were i.v. or iPan injected into streptozotocin-treated non-obese diabetic/severe combined immune-deficient mice temporally monitored for blood glucose, serum insulin and glucose tolerance. Human cell recruitment and survival in the pancreas, insulin content, islet-associated cell proliferation and islet vascularisation were documented in situ.

RESULTS

UCB-derived ALDH(hi) cells were highly enriched for haematopoietic and endothelial progenitor frequency, and showed increased expression of progenitor and myeloid cell surface markers. Although i.v. transplantation of ALDH(hi) cells demonstrated low pancreas engraftment and only transient blood glucose lowering capacity, iPan injected ALDH(hi) cells reversed established hyperglycaemia, increased serum insulin and improved the response to a glucose challenge. iPan injected ALDH(hi) cells surrounded damaged islets at early time points and increased islet-associated cell proliferation, resulting in the recovery of beta cell mass.

CONCLUSIONS/INTERPRETATION

iPan delivery of UCB ALDH(hi) cells potentiated islet-associated cell proliferation, insulin production and islet revascularisation, resulting in the recovery of host islet function. Elucidation of the progenitor-specific pathways stimulated during islet regeneration may provide new approaches to promote islet expansion during diabetes.

Infusion of mesenchymal stem cells ameliorates hyperglycemia in type 2 diabetic rats: identification of a novel role in improving insulin sensitivity

Infusion of mesenchymal stem cells (MSCs) has been shown to effectively lower blood glucose in diabetic individuals, but the mechanism involved could not be adequately explained by their potential role in promoting islet regeneration. We therefore hypothesized that infused MSCs might also contribute to amelioration of the insulin resistance of peripheral insulin target tissues. To test the hypothesis, we induced a diabetic rat model by high-fat diet/streptozotocin (STZ) administration, performed MSC infusion during the early phase (7 days) or late phase (21 days) after STZ injection, and then evaluated the therapeutic effects of MSC infusion and explored the possible mechanisms involved. MSC infusion ameliorated hyperglycemia in rats with type 2 diabetes (T2D). Infusion of MSCs during the early phase not only promoted β-cell function but also ameliorated insulin resistance, whereas infusion in the late phase merely ameliorated insulin resistance. Infusion of MSCs resulted in an increase of GLUT4 expression and an elevation of phosphorylated insulin receptor substrate 1 (IRS-1) and Akt (protein kinase B) in insulin target tissues. This is the first report of MSC treatment improving insulin sensitivity in T2D. These data indicate that multiple roles and mechanisms are involved in the efficacy of MSCs in ameliorating hyperglycemia in T2D.

Concise review: pancreas regeneration: recent advances and perspectives

The replacement of functional pancreatic β-cells is seen as an attractive potential therapy for diabetes, because diabetes results from an inadequate β-cell mass. Inducing replication of the remaining β-cells and new islet formation from progenitors within the pancreas (neogenesis) are the most direct ways to increase the β-cell mass. Stimulation of both replication and neogenesis have been reported in rodents, but their clinical significance must still be shown. Because human islet transplantation is limited by the scarcity of donors and graft failure within a few years, efforts have recently concentrated on the use of stem cells to replace the deficient β-cells. Currently, embryonic stem cells and induced pluripotent stem cells achieve high levels of β-cell differentiation, but their clinical use is still hampered by ethical issues and/or the risk of developing tumors after transplantation. Pancreatic epithelial cells (duct, acinar, or α-cells) represent an appealing alternative to stem cells because they demonstrate β-cell differentiation capacities. Yet translation of such capacity to human cells after significant in vitro expansion has yet to be achieved. Besides providing new β-cells, cell therapy also has to address the question on how to protect the transplanted cells from destruction by the immune system via either allo- or autoimmunity. Encouraging developments have been made in encapsulation and immunomodulation techniques, but many challenges still remain. Herein, we discuss recent advances in the search for β-cell replacement therapies, current strategies for circumventing the immune system, and mandatory steps for new techniques to be translated from bench to clinics.