Failure of transplanted bone marrow cells to adopt a pancreatic beta-cell fate

Bone-marrow derived cells do not contribute to new beta-cells in the inflamed pancreas

The contribution of bone-marrow derived cells (BMCs) to a newly formed beta-cell population in adults is controversial. Previous studies have only used models of bone marrow transplantation from sex-mismatched donors (or other models of genetic labeling) into recipient animals that had undergone irradiation. This approach suffers from the significant shortcoming of the off-target effects of irradiation. Partial pancreatic duct ligation (PDL) is a mouse model of acute pancreatitis with a modest increase in beta-cell number. However, the possibility that recruited BMCs in the inflamed pancreas may convert into beta-cells has not been examined. Here, we used an irradiation-free model to track the fate of the BMCs from the donor mice. A ROSA-mTmG red fluorescent mouse was surgically joined to an INS1^Cre knock-in mouse by parabiosis to establish a mixed circulation. PDL was then performed in the INS1^Cre mice 2 weeks after parabiosis, which was one week after establishment of the stable blood chimera. The contribution of red cells from ROSA-mTmG mice to beta-cells in INS1^Cre mouse was evaluated based on red fluorescence, while cell fusion was evaluated by the presence of green fluorescence in beta-cells. We did not detect any red or green insulin+ cells in the INS1^Cre mice, suggesting that there was no contribution of BMCs to the newly formed beta-cells, either by direct differentiation, or by cell fusion. Thus, the contribution of BMCs to beta-cells in the inflamed pancreas should be minimal, if any.

Type 1 diabetes and engineering enhanced islet transplantation

The development of new therapeutic approaches to treat type 1 diabetes mellitus (T1D) relies on the precise understanding and deciphering of insulin-secreting β-cell biology, as well as the mechanisms responsible for their autoimmune destruction. β-cell or islet transplantation is viewed as a potential long-term therapy for the millions of patients with diabetes. To advance the field of insulin-secreting cell transplantation, two main research areas are currently investigated by the scientific community: (1) the identification of the developmental pathways that drive the differentiation of stem cells into insulin-producing cells, providing an inexhaustible source of cells; and (2) transplantation strategies and engineered transplants to provide protection and enhance the functionality of transplanted cells. In this review, we discuss the biology of pancreatic β-cells, pathology of T1D and current state of β-cell differentiation. We give a comprehensive view and discuss the different possibilities to engineer enhanced insulin-secreting cell/islet transplantation from a translational perspective.

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.

Chorionic and amniotic placental membrane-derived stem cells, from gestational diabetic women, have distinct insulin secreting cell differentiation capacities

Women with gestational diabetes mellitus (GDM), and their offspring, are at high risk of developing type 2 diabetes. Chorionic (CMSCs) and amniotic mesenchymal stem cells (AMSCs) derived from placental membranes provide a source of autologous stem cells for potential diabetes therapy. We established an approach for the CMSC/AMSC-based generation of functional insulin-producing cells (IPCs). CMSCs/AMSCs displayed significantly elevated levels of NANOG and OCT4 versus bone marrow-derived MSCs, indicating a potentially broad differentiation capacity. Exposure of Healthy- and GDM-CMSCs/AMSCs to long-term high-glucose culture resulted in significant declines in viability accompanied by elevation, markedly so in GDM-CMSCs/AMSCs, of senescence/stress markers. Short-term high-glucose culture promoted pancreatic transcription factor expression when coupled to a 16-day step-wise differentiation protocol; activin A, retinoic acid, epidermal growth factor, glucagon-like peptide-1 and other chemical components, generated functional IPCs from both Healthy- and GDM-CMSCs. Healthy-/GDM-AMSCs displayed betacellulin-sensitive insulin expression, which was not secreted upon glucose challenge. The pathophysiological state accompanying GDM may cause irreversible impairment to endogenous AMSCs; however, GDM-CMSCs possess comparable therapeutic potential with Healthy-CMSCs and can be effectively reprogrammed into insulin-secreting cells.

(Re)generating Human Beta Cells: Status, Pitfalls, and Perspectives

Diabetes mellitus results from disturbed glucose homeostasis due to an absolute (type 1) or relative (type 2) deficiency of insulin, a peptide hormone almost exclusively produced by the beta cells of the endocrine pancreas in a tightly regulated manner. Current therapy only delays disease progression through insulin injection and/or oral medications that increase insulin secretion or sensitivity, decrease hepatic glucose production, or promote glucosuria. These drugs have turned diabetes into a chronic disease as they do not solve the underlying beta cell defects or entirely prevent the long-term complications of hyperglycemia. Beta cell replacement through islet transplantation is a more physiological therapeutic alternative but is severely hampered by donor shortage and immune rejection. A curative strategy should combine newer approaches to immunomodulation with beta cell replacement. Success of this approach depends on the development of practical methods for generating beta cells, either in vitro or in situ through beta cell replication or beta cell differentiation. This review provides an overview of human beta cell generation.

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.

Bone Marrow Chimeras to Study Neuroinflammation

Bone marrow transplantation is the standard of care for a host of diseases such as leukemia and multiple myeloma, as well as genetically inherited metabolic diseases affecting the central nervous system. In mouse models, bone marrow transplantation has proven a valuable tool for understanding the hematopoietic system and the homing of hematopoietic cells to their target organs. Many techniques have been developed to create chimeric mice, animals with a hematopoietic system derived from a genetic background that differs from the rest of the body. Current genetic tools allow for virtually limitless possibilities in the choice of donor mice. This protocol describes methods of bone marrow transplantation in mouse models for studies of the brain under basal and pathological conditions. Specific points to be addressed include the preparation of recipient mice by irradiation or chemotherapy; the choice, isolation, and injection of donor cells; and analytical methods such as fluorescence-activated cell sorting and immunostaining. © 2018 by John Wiley & Sons, Inc.

Mesenchymal Stem Cells as New Therapeutic Approach for Diabetes and Pancreatic Disorders

Diabetes is a worldwide disease which actually includes different disorders related to glucose metabolism. According to different epidemiological studies, patients affected by diabetes present a higher risk to develop both acute and chronic pancreatitis, clinical situations which, in turn, increase the risk to develop pancreatic cancer. Current therapies are able to adjust insulin levels according to blood glucose peak, but they only partly reach the goal to abrogate the consequent inflammatory milieu responsible for diabetes-related diseases. In recent years, many studies have investigated the possible use of adult mesenchymal stem cells (MSCs) as alternative therapeutic treatment for diabetes, with promising results due to the manifold properties of these cells. In this review we will critically analyze the many different uses of MSCs for both diabetes treatment and for the reduction of diabetes-related disease development, focusing on their putative molecular mechanisms.

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.

Therapeutic potential of Mesenchymal Stem Cells for the treatment of diabetic peripheral neuropathy

Type-1 Diabetes is generally treated with exogenous insulin administration. Despite treatment, a very common long term consequence of diabetes is the development of a disabling and painful peripheral neuropathy. The transplantation of pancreatic islets is an advanced alternative therapeutic approach, but its clinical application is still very limited, mainly because of the great number of islets required to complete the procedure and of their short-term survival. An intriguing method to improve the performance of pancreatic islets transplantation is the co-transplantation of Mesenchymal Stem Cells (MSCs), adult stem cells already known to support the survival of different cellular populations. In this proof-of-concept study, we demonstrated using an in vivo model of diabetes, the ability of allogenic MSCs to reduce the number of pancreatic islets necessary to achieve glycemic control in diabetic rats, and overall their positive effect on diabetic neuropathy, with the reduction of all the neuropathic signs showed after disease induction. The cutback of the pancreatic islet number required to control glycemia and the regression of the painful neuropathy make MSC co-transplantation a very promising tool to improve the clinical feasibility of pancreatic islet transplantation for diabetes treatment.

G-CSF prevents caspase 3 activation in Schwann cells after sciatic nerve transection, but does not improve nerve regeneration

Exogenous granulocyte-colony stimulating factor (G-CSF) has emerged as a drug candidate for improving the outcome after peripheral nerve injuries. We raised the question if exogenous G-CSF can improve nerve regeneration following a clinically relevant model - nerve transection and repair - in healthy and diabetic rats. In short-term experiments, distance of axonal regeneration and extent of injury-induced Schwann cell death was quantified by staining for neurofilaments and cleaved caspase 3, respectively, seven days after repair. There was no difference in axonal outgrowth between G-CSF-treated and non-treated rats, regardless if healthy Wistar or diabetic Goto-Kakizaki (GK) rats were examined. However, G-CSF treatment caused a significant 13% decrease of cleaved caspase 3-positive Schwann cells at the lesion site in healthy rats, but only a trend in diabetic rats. In the distal nerve segments of healthy rats a similar trend was observed. In long-term experiments of healthy rats, regeneration outcome was evaluated at 90days after repair by presence of neurofilaments, wet weight of gastrocnemius muscle, and perception of touch (von Frey monofilament testing weekly). The presence of neurofilaments distal to the suture line was similar in G-CSF-treated and non-treated rats. The weight ratio of ipsi-over contralateral gastrocnemius muscles, and perception of touch at any time point, were likewise not affected by G-CSF treatment. In addition, the inflammatory response in short- and long-term experiments was studied by analyzing ED1 stainable macrophages in healthy rats, but in neither case was any attenuation seen at the injury site or distal to it. G-CSF can prevent caspase 3 activation in Schwann cells in the short-term, but does not detectably affect the inflammatory response, nor improve early or late axonal outgrowth or functional recovery.

Human umbilical cord matrix-derived stem cells exert trophic effects on β-cell survival in diabetic rats and isolated islets

Human umbilical cord matrix-derived stem cells (uMSCs), owing to their cellular and procurement advantages compared with mesenchymal stem cells derived from other tissue sources, are in clinical trials to treat type 1 (T1D) and type 2 diabetes (T2D). However, the therapeutic basis remains to be fully understood. The immunomodulatory property of uMSCs could explain the use in treating T1D; however, the mere immune modulation might not be sufficient to support the use in T2D. We thus tested whether uMSCs could exert direct trophic effects on β-cells. Infusion of uMSCs into chemically induced diabetic rats prevented hyperglycemic progression with a parallel preservation of islet size and cellularity, demonstrating the protective effect of uMSCs on β-cells. Mechanistic analyses revealed that uMSCs engrafted long-term in the injured pancreas and the engraftment markedly activated the pancreatic PI3K pathway and its downstream anti-apoptotic machinery. The pro-survival pathway activation was associated with the expression and secretion of β-cell growth factors by uMSCs, among which insulin-like growth factor 1 (IGF1) was highly abundant. To establish the causal relationship between the uMSC-secreted factors and β-cell survival, isolated rat islets were co-cultured with uMSCs in the transwell system. Co-culturing improved the islet viability and insulin secretion. Furthermore, reduction of uMSC-secreted IGF1 via siRNA knockdown diminished the protective effects on islets in the co-culture. Thus, our data support a model whereby uMSCs exert trophic effects on islets by secreting β-cell growth factors such as IGF1. The study reveals a novel therapeutic role of uMSCs and suggests that multiple mechanisms are employed by uMSCs to treat diabetes.

Mesenchymal Stem Cells: Rising Concerns over Their Application in Treatment of Type One Diabetes Mellitus

Type 1 diabetes mellitus (T1DM) is an autoimmune disorder that leads to beta cell destruction and lowered insulin production. In recent years, stem cell therapies have opened up new horizons to treatment of diabetes mellitus. Among all kinds of stem cells, mesenchymal stem cells (MSCs) have been shown to be an interesting therapeutic option based on their immunomodulatory properties and differentiation potentials confirmed in various experimental and clinical trial studies. In this review, we discuss MSCs differential potentials in differentiation into insulin-producing cells (IPCs) from various sources and also have an overview on currently understood mechanisms through which MSCs exhibit their immunomodulatory effects. Other important issues that are provided in this review, due to their importance in the field of cell therapy, are genetic manipulations (as a new biotechnological method), routes of transplantation, combination of MSCs with other cell types, frequency of transplantation, and special considerations regarding diabetic patients' autologous MSCs transplantation. At the end, utilization of biomaterials either as encapsulation tools or as scaffolds to prevent immune rejection, preparation of tridimensional vascularized microenvironment, and completed or ongoing clinical trials using MSCs are discussed. Despite all unresolved concerns about clinical applications of MSCs, this group of stem cells still remains a promising therapeutic modality for treatment of diabetes.

Co-transplantation of mesenchymal stromal cells and cord blood cells in treatment of diabetes

BACKGROUND AIMS

Stem cells provide a promising source for treatment of type 1 diabetes, but the treatment strategy and mechanism remain unclear. The aims of this study were to investigate whether co-transplantation of umbilical cord-derived mesenchymal stromal cells (UC-MSCs) and cord blood mononuclear cells (CB-MNCs) could reverse hyperglycemia in type 1 diabetic mice and to determine the appropriate ratio for co-transplantation. The treatment mechanism was also studied.

METHODS

A simple and efficient isolation method was developed to generate qualified UC-MSCs. UC-MSCs and CB-MNCs were then transplanted into type 1 diabetic mice at different ratios (UC-MSCs to CB-MNCs = 1:1, 1:4, 1:10) to observe the change in blood glucose concentration. Histology, immunohistochemistry, and human Alu polymerase chain reaction assay were performed to evaluate for the presence of donor-derived cells and the repair of endogenous islets. We also induced UC-MSCs into islet-like cells under specific culture conditions to determine their differentiate potential in vitro.

RESULTS

Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 effectively reversed hyperglycemia in diabetic mice. The detection of human Alu sequence indicated that the engraftment of donor-derived cells had homed into the recipient's pancreas and kidney. Although neither human insulin nor human nuclei antigen was detected in the regenerated pancreas, UC-MSCs could differentiate into insulin-secreted cells in vitro.

CONCLUSIONS

Co-transplantation of UC-MSCs and CB-MNCs at a ratio of 1:4 could efficiently reverse hyperglycemia and repair pancreatic tissue.

Adult stem cells as a renewable source of insulin-producing cells

Diabetes mellitus is a metabolic disorder resulting from an inadequate mass of insulin-producing pancreatic beta cells. The replacement or restoration of damaged beta cells would be considered the optimal therapeutic options. Islet transplantation seems to be a promising approach for replacement therapy; however, the main obstacle is the shortage of organ donors. As mature beta cells have been shown to be difficult to expand in vitro, regeneration of beta cells from embryonic or adult stem cells or pancreatic progenitor cells is an attractive method to restore the islet cell mass. So far, multiple studies using various strategies have shown direct differentiation of stem and progenitor cells toward insulin-producing cells. The important issue to be solved is how to differentiate these cells into mature functional insulin-producing cells. Further research is required to understand how endogenous beta cells differentiate and to develop methods to regenerate enough functional beta cells for clinically applicable therapies for diabetes.

Transplantation of mesenchymal stem cells recruits trophic macrophages to induce pancreatic beta cell regeneration in diabetic mice

Alleviation of hyperglycemia in chemical-induced diabetic mice has been reported after bone marrow transplantation. Nevertheless, the underlying mechanism remains elusive. In the present study, we transplanted genetically labeled primary mouse mesenchymal stem cells into the pancreas of the streptozotocin-treated hyperglycemic isogeneic mice, resulting in a decrease in blood glucose due to a recovery in beta cell mass. Further analysis revealed that the increase in beta cell mass was predominantly attributable to beta cell replication. The grafted mesenchymal stem cells did not transdifferentiate into beta cells themselves but recruited and polarized macrophages in a Stromal cell-derived factor 1-dependent manner, which in turn promoted beta cell replication. Our finding thus suggests that transplantation of autogenic mesenchymal stem cells may increase functional beta cell mass by boosting beta cell replication in diabetes.

Mesenchymal stromal cells improve transplanted islet survival and islet function in a syngeneic mouse model

AIMS/HYPOTHESIS

Islet transplantation is used therapeutically in a minority of patients with type 1 diabetes. Successful outcomes are hampered by early islet beta cell loss. The adjuvant co-transplantation of mesenchymal stromal cells (MSCs) has the promise to improve islet transplant outcome.

METHODS

We used a syngeneic marginal islet mass transplantation model in a mouse model of diabetes. Mice received islets or islets plus 250,000 MSCs. Kidney subcapsule, intra-hepatic and intra-ocular islet transplantation sites were used. Apoptosis, vascularisation, beta cell proliferation, MSC differentiation and laminin levels were determined by immunohistochemical analysis and image quantification post-transplant.

RESULTS

Glucose homeostasis after the transplantation of syngeneic islets was improved by the co-transplantation of MSCs together with islets under the kidney capsule (p = 0.01) and by intravenous infusion of MSCs after intra-hepatic islet transplantation (p = 0.05). MSC co-transplantation resulted in reduced islet apoptosis, with reduced numbers of islet cells positive for cleaved caspase 3 being observed 14 days post-transplant. In kidney subcapsule, but not in intra-ocular islet transplant models, we observed increased re-vascularisation rates, but not increased blood vessel density in and around islets co-transplanted with MSCs compared with islets that were transplanted alone. Co-transplantation of MSCs did not increase beta cell proliferation, extracellular matrix protein laminin production or alpha cell numbers, and there was negligible MSC transdifferentiation into beta cells.

CONCLUSIONS/INTERPRETATION

Co-transplantation of MSCs may lead to improved islet function and survival in the early post-transplantation period in humans receiving islet transplantation.

Intraportal injection of insulin-producing cells generated from human bone marrow mesenchymal stem cells decreases blood glucose level in diabetic rats

We studied the process of trans-differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) into insulin-producing cells. Streptozotocin (STZ)-induced diabetic rat model was used to study the effect of portal vein transplantation of these insulin-producing cells on blood sugar levels. The BM-MSCs were differentiated into insulin-producing cells under defined conditions. Real-time PCR, immunocytochemistry and glucose challenge were used to evaluate in vitro differentiation. Flow cytometry showed that hBM-MSCs were strongly positive for CD44, CD105 and CD73 and negative for hematopoietic markers CD34, CD38 and CD45. Differentiated cells expressed C-peptide as well as β-cells specific genes and hormones. Glucose stimulation increased C-peptide secretion in these cells. The insulin-producing, differentiated cells were transplanted into the portal vein of STZ-induced diabetic rats using a Port-A catheter. The insulin-producing cells were localized in the liver of the recipient rat and expressed human C-peptide. Blood glucose levels were reduced in diabetic rats transplanted with insulin-producing cells. We concluded that hBM-MSCs could be trans-differentiated into insulin-producing cells in vitro. Portal vein transplantation of insulin-producing cells alleviated hyperglycemia in diabetic rats.

Two distinct mechanisms mediate the involvement of bone marrow cells in islet remodeling: neogenesis of insulin-producing cells and support of islet recovery

We have recently reported that small-sized bone marrow cells (BMCs) isolated by counterflow centrifugal elutriation and depleted of lineage markers (Fr25lin(-)) have the capacity to differentiate and contribute to regeneration of injured islets. In this study, we assess some of the characteristics of these cells compared to elutriated hematopoietic progenitors (R/O) and whole BMCs in a murine model of streptozotocin-induced chemical diabetes. The GFP(bright)CD45(+) progeny of whole BMCs and R/O progenitors progressively infiltrate the pancreas with evolution of donor chimerism; are found at islet perimeter, vascular, and ductal walls; and have a modest impact on islet recovery from injury. In contrast, Fr25lin(-) cells incorporate in the islets, convert to GFP(dim)CD45(-)PDX-1(+) phenotypes, produce proinsulin, and secrete insulin with significant contribution to stabilization of glucose homeostasis. The elutriated Fr25lin(-) cells express low levels of CD45 and are negative for SCA-1 and c-kit, as removal of cells expressing these markers did not impair conversion to produce insulin. BMCs mediate two synergistic mechanisms that contribute to islet recovery from injury: support of islet remodeling by hematopoietic cells and neogenesis of insulin-producing cells from stem cells.

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.

WITHDRAWN: Transplantation of mesenchymal stem cells recruits trophic macrophages to induce pancreatic beta cell regeneration in diabetic mice

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Amniotic fluid stem cells prevent β-cell injury

BACKGROUND AIMS

The contribution of amniotic fluid stem cells (AFSC) to tissue protection and regeneration in models of acute and chronic kidney injuries and lung failure has been shown in recent years. In the present study, we used a chemically induced mouse model of type 1 diabetes to determine whether AFSC could play a role in modulating β-cell injury and restoring β-cell function.

METHODS

Streptozotocin-induced diabetic mice were given intracardial injection of AFSC; morphological and physiological parameters and gene expression profile for the insulin pathway were evaluated after cell transplantation.

RESULTS

AFSC injection resulted in protection from β-cell damage and increased β-cell regeneration in a subset of mice as indicated by glucose and insulin levels, increased islet mass and preservation of islet structure. Moreover, β-cell preservation/regeneration correlated with activation of the insulin receptor/Pi3K/Akt signaling pathway and vascular endothelial growth factor-A expression involved in maintaining β-cell mass and function.

CONCLUSIONS

Our results suggest a therapeutic role for AFSC in preserving and promoting endogenous β-cell functionality and proliferation. The protective role of AFSC is evident when stem cell transplantation is performed before severe hyperglycemia occurs, which suggests the importance of early intervention. The present study demonstrates the possible benefits of the application of a non-genetically engineered stem cell population derived from amniotic fluid for the treatment of type 1 diabetes mellitus and gives new insight on the mechanism by which the beneficial effect is achieved.

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.

Mesenchymal stem cell therapy in diabetes mellitus: progress and challenges

Advanced type 2 diabetes mellitus is associated with significant morbidity and mortality due to cardiovascular, nervous, and renal complications. Attempts to cure diabetes mellitus using islet transplantation have been successful in providing a source for insulin secreting cells. However, limited donors, graft rejection, the need for continued immune suppression, and exhaustion of the donor cell pool prompted the search for a more sustained source of insulin secreting cells. Stem cell therapy is a promising alternative for islet transplantation in type 2 diabetic patients who fail to control hyperglycemia even with insulin injection. Autologous stem cell transplantation may provide the best outcome for those patients, since autologous cells are readily available and do not entail prolonged hospital stays or sustained immunotoxic therapy. Among autologous adult stem cells, mesenchymal stem cells (MSCs) therapy has been applied with varying degrees of success in both animal models and in clinical trials. This review will focus on the advantages of MSCs over other types of stem cells and the possible mechanisms by which MSCs transplant restores normoglycemia in type 2 diabetic patients. Sources of MSCs including autologous cells from diabetic patients and the use of various differentiation protocols in relation to best transplant outcome will be discussed.

VEGF induces neuroglial differentiation in bone marrow-derived stem cells and promotes microglia conversion following mobilization with GM-CSF

PURPOSE

Evaluation of potential tropic effects of vascular endothelial growth factor (VEGF) on the incorporation and differentiation of bone-marrow-derived stem cells (BMSCs) in a murine model of anterior ischemic optic neuropathy (AION).

METHODS

In the first approach, small-sized subset of BMCs were isolated from GFP donors mice by counterflow centrifugal elutriation and depleted of hematopoietic lineages (Fr25lin(-)). These cells were injected into a peripheral vein (1 × 10(6) in 0.2 ml) or inoculated intravitreally (2 × 10(5)) to syngeneic mice, with or without intravitreal injection of 5 μg/2μL VEGF, simultaneously with AION induction. In a second approach, hematopoietic cells were substituted by myelablative transplant of syngeseic GFP + bone marrow cells. After 3 months, progenitors were mobilized with granulocyte-macrophage colony-stimulating factor (GM-CSF) followed by VEGF inoculation into the vitreous body and AION induction . Engraftment and phenotype were examined by immunohistochemistry and FISH at 4 and 24 weeks post-transplantation, and VEGF receptors were determined by real time PCR.

RESULTS

VEGF had no quantitative effect on incorporation of elutriated cells in the injured retina, yet it induced early expression of neuroal markers in cells incorporated in the RGC layer and promoted durable gliosis, most prominent perivascular astrocytes. These effects were mediated by VEGF-R1/Flt-1, which is constitutively expresses in the elutriated fraction of stem cells. Mobilization with GM-CSF limited the differentiation of bone marrow progenitors to microglia, which was also fostered by VEGF.

CONCLUSIONS

VEGF signaling mediated by Flt-1 induces early neural and sustained astrocytic differentiation of stem cells elutriated from adult bone-marrow, with significant contribution to stabilization retinal architecture following ischemic injury.

Contribution of bone marrow derived cells to the pancreatic tumor microenvironment

Pancreatic cancer is a complex, aggressive, and heterogeneous malignancy driven by the multifaceted interactions within the tumor microenvironment. While it is known that the tumor microenvironment accommodates many cell types, each playing a key role in tumorigenesis, the major source of these stromal cells is not well-understood. This review examines the contribution of bone marrow-derived cells (BMDC) to pancreatic carcinogenesis, with respect to their role in constituting the tumor microenvironment. In particular, their role in supporting fibrosis, immunosuppression, and neovascularization will be discussed.

Concise review: mesenchymal stem cells for diabetes

Mesenchymal stem cells (MSCs) have already made their mark in the young field of regenerative medicine. Easily derived from many adult tissues, their therapeutic worth has already been validated for a number of conditions. Unlike embryonic stem cells, neither their procurement nor their use is deemed controversial. Here we review the potential use of MSCs for the treatment of type 1 diabetes mellitus, a devastating chronic disease in which the insulin-producing cells of the pancreas (the β-cells) are the target of an autoimmune process. It has been hypothesized that stem cell-derived β-cells may be used to replenish the islet mass in diabetic patients, making islet transplantation (a form of cell therapy that has already proven effective at clinically restoring normoglycemia) available to millions of prospective patients. Here we review the most current advances in the design and application of protocols for the differentiation of transplantable β-cells, with a special emphasis in analyzing MSC potency according to their tissue of origin. Although no single method appears to be ripe enough for clinical trials yet, recent progress in reprogramming (a biotechnological breakthrough that relativizes the thus far insurmountable barriers between embryonal germ layers) bodes well for the rise of MSCs as a potential weapon of choice to develop personalized therapies for type 1 diabetes.

Recruitment and activation of pancreatic stellate cells from the bone marrow in pancreatic cancer: a model of tumor-host interaction

Background and Aims

Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas.

Methods

Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation.

Results

GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3.

Conclusions

This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis.

Mesenchymal Stromal Cells as a Therapeutic Strategy to Support Islet Transplantation in Type 1 Diabetes Mellitus

Type 1 diabetes is an autoimmune disorder that leads to destruction of pancreatic β islet cells and is a growing global health issue. While insulin replacement remains the standard therapy for type 1 diabetes, exogenous insulin does not mimic the physiology of insulin secretion. Transplantation of pancreatic islets has the potential to cure this disease; however, there are several major limitations to widespread implementation of islet transplants. The use of mesenchymal stromal cells (MSCs) in the treatment of type 1 diabetes has been investigated as an adjunct therapy during islet graft administration to prevent initial islet loss and promote engraftment and revascularization of islets. In this review we will discuss the results of recent MSC studies in animal models of diabetes with a focus on islet transplantation and explore the potential for these findings to be extended to clinical use for the treatment of type 1 diabetes.

Nutritional programming of pancreatic β-cell plasticity

Nutritional insufficiency during pregnancy has been shown to alter the metabolism of the offspring and can increase the risk of type 2 diabetes. The phenotype in the offspring involves changes to the morphology and functional capacity of the endocrine pancreas, and in the supporting islet microvasculature. Pancreatic β-cells possess a plastic potential and can partially recover from catastrophic loss. This is partly due to the existence of progenitors within the islets and the ability to generate new islets by neogenesis from the pancreatic ducts. This regenerative capacity is induced by bone marrow-derived stem cells, including endothelial cell progenitors and is associated with increased angiogenesis within the islets. Nutritional insults in early life, such as feeding a low protein diet to the mother, impair the regenerative capacity of the β-cells. The mechanisms underlying this include a reduced ability of β-cells to differentiate from the progenitor population, changes in the inductive signals from the microvasculature and an altered presence of endothelial progenitors. Statin treatment within animal models was associated with angiogenesis in the islet microvasculature, improved vascular function and an increase in β-cell mass. This demonstrates that reversal of the impaired β-cell phenotype observed following nutritional insult in early life is potentially possible.

Spontaneous in vivo differentiation of embryonic stem cell-derived pancreatic endoderm-like cells corrects hyperglycemia in diabetic mice

BACKGROUND

Whole pancreas and islet transplantation are currently used for the treatment of type 1 diabetes. However, the major limitations of this potentially curative approach are an inadequate supply of cadaveric pancreata, lifelong immunosuppression, and chronic graft rejection. Therefore, there is an urgent need to develop new sources of insulin-producing cells (IPCs). Here, we investigated whether embryonic stem (ES) cells can be exploited for the derivation of IPCs, and whether their transplantation can correct hyperglycemia in diabetic mice.

METHODS

ES cells engineered to express pancreatic and duodenal homeobox 1 (Pdx1), a critical pancreatic transcription factor, were differentiated into pancreatic endoderm-like cells (PELCs) and evaluated for their potential to correct hyperglycemia after transplantation in diabetic mice.

RESULTS

After systemic injection, PELCs localized to the pancreas, liver, and kidney. They then spontaneously differentiated into IPCs that corrected hyperglycemia in diabetic mice. When transplanted under the kidney capsule, PELC-derived IPCs were equally efficient at correcting hyperglycemia. Real-time noninvasive in vivo bioluminescence imaging (BLI) of rat insulin promoter (RIP)-driven luciferase was used to monitor the fate of the transplanted PELCs. To confirm that the transplanted cells were responsible for the correction of hyperglycemia, kidneys containing the transplanted cells were nephrectomized, causing rapid hyperglycemia. Interestingly, none of the animals transplanted with PELCs developed tumors, a potential consequence of the differentiation and purification procedures.

CONCLUSIONS

Our data suggest that Pdx1-expressing PELCs are capable of spontaneously undergoing differentiation in vivo into IPCs and leading to a sustained correction of hyperglycemia in diabetic mice.

Differentiation of dental pulp stem cells into islet-like aggregates

The post-natal dental pulp tissue contains a population of multipotent mesenchymal progenitor cells known as dental pulp stromal/stem cells (DPSCs), with high proliferative potential for self-renewal. In this investigation, we explored the potential of DPSCs to differentiate into pancreatic cell lineage resembling islet-like cell aggregates (ICAs). We isolated, propagated, and characterized DPSCs and demonstrated that these could be differentiated into adipogenic, chondrogenic, and osteogenic lineage upon exposure to an appropriate cocktail of differentiating agents. Using a three-step protocol reported previously by our group, we succeeded in obtaining ICAs from DPSCs. The identity of ICAs was confirmed as islets by dithiozone-positive staining, as well as by expression of C-peptide, Pdx-1, Pax4, Pax6, Ngn3, and Isl-1. There were several-fold up-regulations of these transcription factors proportional to days of differentiation as compared with undifferentiated DPSCs. Day 10 ICAs released insulin and C-peptide in a glucose-dependent manner, exhibiting in vitro functionality. Our results demonstrated for the first time that DPSCs could be differentiated into pancreatic cell lineage and offer an unconventional and non-controversial source of human tissue that could be used for autologous stem cell therapy in diabetes.

Stem cell-based strategies for the treatment of type 1 diabetes mellitus

IMPORTANCE OF THE FIELD

β-Cell regeneration and β-cell preservation are two promising therapeutic approaches for the management of patients with type 1 diabetes (T1D). Stem cell-based strategies to address the problems of shortage in β cells, autoimmune and alloimmune responses have become an area of intense study.

AREAS COVERED IN THIS REVIEW

This review focuses on the progress that has been made in obtaining functional, insulin-producing cells from various types of stem/progenitor cells, including the current knowledge on the immunomodulatory roles of hematopoietic stem cell and multipotent stromal cell in the therapies for T1D.

WHAT THE READER WILL GAIN

A broad overview of recent advancements in this field is provided. The hurdles that remain in the path of using stem cell-based strategies for the treatment of T1D and possible approaches to overcome these challenges are discussed.

TAKE HOME MESSAGE

Stem cell-based strategies hold great promise for the treatment of T1D. In spite of the progress that has been made over the last decade, a number of obstacles and concerns need to be cleared before widespread clinical application is possible. In particular, the mechanism of ESC and iPSC-derived β-cell maturation in vivo is poorly understood.

Lineage tracing and resulting phenotype of haemopoietic-derived cells in the pancreas during beta cell regeneration

AIMS

Transplantation of bone marrow-derived haemopoietic stem cells following streptozotocin (STZ) treatment to induce pancreatic beta cell loss in mice causes the partial regeneration of beta cell mass, with many haemopoietic cells demonstrating endothelial cell markers. This study used genetically tagged haemopoietic lineage-derived cells to determine how endogenous cells are mobilised following beta cell loss and subsequent replacement.

METHODS

A double transgenic mouse model, Vav-iCre; R26R-enhanced yellow fluorescent protein (YFP), was used where only haemopoietic lineage cells expressed the Vav1 gene promoter allowing expression of the YFP reporter gene. Between postnatal days 2 and 4 mice were injected with STZ or vehicle (control) and body weight and glycaemia were monitored. Mice were killed between days 10 and 130, and the pancreases were examined by immunofluorescence microscopy.

RESULTS

YFP-expressing cells infiltrated the pancreas at all ages, being present around newly forming islets at the pancreatic ducts, and within larger islets. Small numbers of YFP-positive cells (<5%) co-stained for the macrophage markers F4/80 or Mac1, for cytokeratin 19, or for the transcription factor pancreatic and duodenal homeobox 1 (PDX-1), but no co-localisation was seen with insulin or other endocrine hormones. Within islets approximately 30% of YFP-positive cells co-stained for the endothelial cell marker CD31, and following STZ the number of haemopoietic-derived cells, and the proportion that were CD31-positive, both significantly increased after 21 and 40 days, coincident with a partial replacement of beta cells.

CONCLUSIONS

Our results suggest that following beta cell loss endogenous haemopoietic-lineage cells contribute to intra-islet angiogenesis, which supports a partial recovery of beta cell mass.

Induction of insulin-producing cells derived from endometrial mesenchymal stem-like cells

Studies have demonstrated that mesenchymal stem-like cells can be isolated from endometrium. However, the potential of endometrial-derived stem cells to differentiate into insulin-positive cells and functionally secrete insulin remains undetermined. We isolated endometrial mesenchymal stem-like cells (EMSCs) from human endometrial tissue from six donors. The insulin-secreting function of EMSCs was further analyzed in vitro and in transplanted grafts in vivo. We successfully isolated EMSCs from human endometrium, and our results showed that EMSCs expressed high levels of stemness genes (Nanog, Oct-4, Nestin). Under specific induction conditions for 2 weeks, EMSCs formed three-dimensional spheroid bodies (SBs) and secreted C-peptide. The high insulin content of SB-EMSCs was confirmed by enzyme-linked immunosorbent assay, and glucose responsiveness was demonstrated by measuring glucose-dependent insulin secretion. Using cDNA microarrays, we found that the expression profiles of SB-EMSCs are related to those of islet tissues. Insulin and C-peptide production in response to glucose was significantly higher in SB-EMSCs than in undifferentiated EMSC controls. Furthermore, upon differentiation, SB-EMSCs displayed increased mRNA expression levels of NKx2.2, Glut2, insulin, glucagon, and somatostatin. Our results also showed that SB-EMSCs were more resistant to oxidative damage and oxidative damage-induced apoptosis than fibroblasts from the same patient. It is noteworthy that SB-EMSCs xenotransplanted into immunocompromised mice with streptozotocin-induced diabetes restored blood insulin levels to control values and greatly prolonged the survival of graft cells. These data suggest that EMSCs not only play a novel role in the differentiation of pancreatic progenitors, but also can functionally enhance insulin production to restore the regulation of blood glucose levels in an in vivo transplantation model.

Lack of evidence for recipient precursor cells replenishing β-cells in transplanted islets

Bone marrow and tissue precursor cells have been postulated to replenish grafts of transplanted islets. Several investigators have reported that bone marrow cells can promote the regeneration of injured islets. In this study, we investigated the potential of recipient-derived precursor cells to form new pancreatic endocrine cells in islet grafts transplanted under the kidney capsule. Mouse insulin promoter (MIP)-green fluorescence protein (GFP) mice, which express GFP only in β-cells, or β-actin GFP mice, which express GFP ubiquitously, were used to determine if the recipient-derived cells differentiate into β-cells or other types of endocrine cells. We transplanted MIP-GFP islets into wild-type mice, wild-type islets into MIP-GFP mice, β-actin GFP islets into wild-type mice, and wild-type islets into β-actin GFP mice. β-Actin GFP bone marrow cells were then injected into wild-type mice to evaluate the potential role of bone marrow stem cells to provide new islet cells to the graft. No β-cells with green fluorescence were seen in the graft when wild-type islets were transplanted into MIP-GFP mice. When wild-type islets were transplanted into β-actin GFP mice, no β-cells with GFP staining could be identified in the grafts. Similarly, no endocrine cells with GFP staining could be identified in the grafts after injection of β-actin GFP bone marrow cells into wild-type islet-transplanted wild-type mice. This study provides further support for the concept that recipient precursor cells do not produce new β-cells in grafts of transplanted islets.

Effects of atorvastatin on the regeneration of pancreatic {beta}-cells after streptozotocin treatment in the neonatal rodent

To investigate the role of statins in beta-cell regeneration a model of streptozotocin (STZ)-induced beta-cell injury was used in the neonatal rat. We hypothesized that beta-cell growth and regeneration would increase following treatment with atorvastatin and that this would be associated with intraislet vasculogenesis. Pregnant Wistar rats were gavaged with 20 or 40 mg/kg atorvastatin for 21 days commencing on gestation day 15. Atorvastatin was detected in the circulation of the offspring. On postnatal day 4, the pups were given either a control or STZ (70 mg/kg ip) injection. beta-Cell mass had partially recovered by postnatal day 44 following STZ treatment, and atorvastatin (20 mg/kg) significantly increased beta-cell mass in both STZ-treated and control animals. An increase in the numbers of small islets at postnatal day 44 was seen in STZ-treated animals following atorvastatin, suggestive of neogenesis, and glucose tolerance was improved. Treatment with atorvastatin caused an increase in the numbers of intraislet endothelial cells at postnatal day 14 and the percentage of endothelial cells undergoing DNA synthesis, suggesting that angiogenesis had preceded the increase in beta-cell mass. The results indicate that functional beta-cell mass was expanded with atorvastatin in both control and STZ-treated neonatal rats and suggests a novel effect of a statin in promoting islet plasticity.

Bone marrow transplantation temporarily improves pancreatic function in streptozotocin-induced diabetes: potential involvement of very small embryonic-like cells

BACKGROUND

The role of bone marrow (BM)-derived cells in pancreatic beta-cell regeneration remains unresolved. We examined whether BM-derived cells are recruited to the site of moderate pancreatic injury and contribute to beta-cell regeneration.

METHODS

Low-dose streptozotocin (STZ) treatment was used to induce moderate pancreatic damage and hyperglycemia. Enhanced green fluorescent protein-positive (EGFP) BM chimeras were evaluated for beta-cell regeneration after STZ treatment.

RESULTS

To test the hypothesis that pancreatic tissue injury induces a stromal cell-derived factor (SDF)-1 gradient to chemoattract the stem cells, we evaluated the expression of mRNA for SDF-1 in damaged pancreatic tissue. SDF-1 was significantly increased in the pancreas after damage, peaking at day 10. The majority of BM cells expressing mRNA for pancreatic development markers were detected in the subpopulation of CD45/Sca-1/Lin very small embryonic-like (VSEL) cells. VSEL cells mobilized from BM to peripheral blood in response to pancreatic damage, peaking in peripheral blood at day 5, and were enriched in the pancreas 10 to 15 days after STZ treatment. To confirm a role for BM-derived cells in pancreatic beta-cell regeneration, we prepared EGFP-->B6 chimeras. In the EGFP chimeras, EGFP cells were detected around duct and islets and were positive for insulin after STZ treatment. However, STZ-induced hyperglycemia was reduced only transiently (49-77 days) after pancreatic injury.

CONCLUSIONS

These data suggest that VSEL cells are mobilized into injured pancreatic tissue and contribute to beta-cell regeneration. Transplantation of BM-derived cells improves the function of injured pancreas, although the response is not sufficient to restore sustained normoglycemia.

Expression of Pdx1 mediates differentiation from mesenchymal stem cells into insulin-producing cells

The transplantation of insulin-producing cells is a promising approach for the treatment of insulin-dependent diabetes mellitus; however, lack of pancreas donors limits its application. Pancreatic duodenal homeobox 1 (Pdx1) plays a key role in the differentiation of various non-β-cells into insulin-producing cells, but the potential mechanism remains to be clarified. The purpose of this study was to confirm that the expression of Pdx1 could mediate the differentiation of rat mesenchymal stem cells (MSCs) into insulin-producing cells and evaluate the potential molecular mechanisms in the process that Pdx1 activates transcription of insulin gene. In this study, glucose-stimulated insulin secretion was obviously detected in MSCs transfected with Pdx1 cDNA by insulin release assay and the islet-like structure formed in Pdx1-expressing MSCs was stained into black-red by dithizone, while the native MSCs were opposite. In addition, we uncovered the close relationships among the expression of Pdx1, insulin and Ngn3 genes, whose expression indicated parallel changes after high glucose challenge, and the fluctuation of Pdx1 and Ngn3 partly resulted in the unstable release of insulin. Taken together, these findings demonstrated that the effective role of Pdx1 gene in inducing insulin-producing cells, which may shuttle to the nucleoplasm of MSCs under high glucose, then initiate the expression of native transcription factors Ngn3 and recruit other proteins, resulting in transactivation of the relevant genes including insulin and generation of β cell phenotype. Accordingly, these results would provide new insights that may be applicable to improve β cell replacement strategies and enhance diabetes therapy in the future.

Role of VEGF-A in pancreatic beta cells

The islet contains a dense vascular structure of several features. The expression of vascular endothelial growth factor (VEGF)-A in beta cells is indispensable for the formation of this structure. Thus, the beta cell-specific VEGF-A-deficient mouse (RIP-Cre:Vegf(fl/fl)) is useful for studying the role of the islet vasculature on the function of islets and regulation of beta cell mass. Studies using RIP-Cre:Vegf(fl/fl) mice revealed that defects in the normal vascular structure are associated with abnormal insulin secretion and concluded that the islet vascular system is essential for normal insulin secretion into the blood stream. On the other hand, whereas the endothelial cells might be involved in regulation of islet mass and the mouse model of diabetes shows that the number of endothelial cells correlate with the islet mass, RIP-Cre:Vegf(fl/fl) mice show almost normal response of islet expansion in the presence of insulin resistance. However, whereas bone marrow transplantation induces islet expansion in control mice, it does not induce the proper expansion of beta cell mass in RIP-Cre:Vegf(fl/fl) mice. These data indicate that the roles of VEGF-A and islet vasculature in the regulation of beta cell mass depends on the stimulus for the islets.

Mesenchymal stroma cells improve hyperglycemia and insulin deficiency in the diabetic porcine pancreatic microenvironment

BACKGROUND

Stem cell differentiation is controlled by extracellular cues from the environment and by intrinsic genetic programs within the stem cell. The present study aimed to explore whether mesenchymal stromal cells (MSC) could improve hyperglycemia and insulin production in the diabetic microenvironment.

METHODS

We transplanted male porcine bone marrow-derived EGFP-expressing MSC directly into female diabetic porcine pancreas by multi-point injection. Enzyme-linked immunosorbent assay (ELISA) and fluorescent immunohistochemistry were used to analyze recipients' sera and pancreas tissues for assessment of the therapeutic effect.

RESULTS

Blood glucose levels decreased gradually in MSC-treated recipients from 15 days after the transplantation compared with untreated diabetic controls (15.94+/-0.31 mmol/L versus 16.66+/-0.11 mmol/L; P=0.01). Blood insulin increased and glucagons decreased notably in recipients from 2 weeks post-transplantation compared with untreated diabetic controls (0.049+/-0.004 microg/L versus 0.037+/-0.02 microg/L and 392.9+/-20.3 ng/L versus 433.1+/-27.6 ng/L). Hematoxylin and eosin (HE)-stained sections demonstrated that the number of islets from each section was markedly increased in recipients compared with that of diabetic controls (10.9+/-2.2 versus 4.6+/-1.4; P<0.05) and similar to that of normal controls (10.9+/-2.2 versus 12.6+/-2.6; P>0.05). The newly formed islets were smaller than normal islets (47.2+/-19.6 microm versus 119.6+/-27.7 microm; P<0.05). Analysis of pancreatic sections for EGFP in recipients indicated that the transplanted MSC survived within the pancreas. Insulin immunoreactivity of pancreatic islets showed that the newly formed islets expressed insulin.

DISCUSSION

MSC could improve diabetes upon pancreatic microenvironment without obvious immune rejections. This has theoretical and clinical applications.

Mesenchymal stem cells adopt beta-cell fate upon diabetic pancreatic microenvironment

OBJECTIVES

: This study observed whether mesenchymal stem cells (MSCs) adopt beta-cell fate upon diabetic microenvironment.

METHODS

: We transplanted male porcine MSCs to diabetic female pigs by directly injecting into pancreas. Recipients' sera and pancreatic tissue were analyzed to assess the therapeutic effect. Islets were collected from the sections using laser-capture microdissection. The RNAs from these specimens were extracted and analyzed for insulin and pancreas duodenum homeobox 1 messenger RNA (mRNA) expression. SRY gene was detected from the specimens.

RESULTS

: Compared with untreated diabetic controls, blood glucose level decreased greatly in recipients from 18 days (15.44 +/- 0.31 mmol/L vs 16.66 +/- 0.11 mmol/L) and insulin increased from 14 days (0.048 +/- 0.006 U/L vs 0.030 +/- 0.004 U/L). Hematoxylin and eosin-stained sections demonstrated increased islets in recipients and few lymphocytes present. The newly formed islets were smaller than normal islets (47.2 mum +/- 19.6 vs 119.6 +/- 27.7 mum). Reverse transcription-polymerase chain reaction showed that microdissected cells expressed insulin and pancreas duodenum homeobox 1 mRNA (79.3% +/- 16.2% of control, 65.2% +/- 14.8% of control, respectively). Immunoreactivity showed that the transplanted MSCs expressed insulin. SRY gene and insulin mRNA double-positive cells were found in microdissected cells by fluorescence in situ hybridization.

CONCLUSIONS

This study shows that MSCs could adopt beta-cell fate in diabetic pancreatic microenvironment without obvious immune rejections. Stem cell transplantation in orthotope is a promising therapy for diabetes.

The contribution of hematopoietic stem cells to beta-cell replacement

Hemopoietic stem cells (HSCs) are commonly used for curing malignant and nonmalignant hematopoiesis disorders. In recent years, HSC potential giving rise to multilineage progeny has been reported. This issue, together with their availability and number, has made them ideal candidates for beta-cell replacement in diabetic patients. HSC capacity to differentiate to insulin-producing cells has been at the center of debate for the past 5 years and it now seems that their role could more likely be that of helper cells able to facilitate survival or stimulate proliferation of endogenous beta cells. In addition, clinical studies are ongoing about the possible use of HSCs to stop autoimmune destruction at the onset of diabetes or to induce tolerance through microchimerism in pancreatic islet transplantation.

Human bone marrow mesenchymal stem cells differentiate into insulin-producing cells upon microenvironmental manipulation in vitro

It was recently reported that pluripotent mesenchymal stem cells (MSCs) in rodent bone marrow (BM) have the capacity to generate insulin-producing cells (IPCs) in vitro. However, little is known about this capacity in human BM-MSCs. We developed a nongenetic method to induce human BM-MSCs to transdifferentiate into IPCs both phenotypically and functionally. BM-MSCs from 12 human donors were sequentially cultured in specially defined conditions. Their differentiation extent toward beta-cell phenotype was evaluated systemically. Specifically, after induction human BM-MSCs formed spheroid islet-like clusters containing IPCs, which was further confirmed by dithizone (DTZ) staining and electron microscopy. These IPCs expressed multiple genes related to the development or function of pancreatic beta cells (including NKX6.1, ISL-1, Beta2/Neurod, Glut2, Pax6, nestin, PDX-1, ngn3, insulin and glucagon). The coexpression of insulin and c-peptide was observed in IPCs by immunofluorescence. Moreover, they were able to release insulin in a glucose-dependent manner and ameliorate the diabetic conditions of streptozotocin (STZ)-treated nude mice. These results indicate that human BM-MSCs might be an available candidate to overcome limitations of islet transplantation.