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

Cytokines inducing bone marrow SCA+ cells migration into pancreatic islet and conversion into insulin-positive cells in vivo

We hypothesize that specific bone marrow lineages and cytokine treatment may facilitate bone marrow migration into islets, leading to a conversion into insulin producing cells in vivo. In this study we focused on identifying which bone marrow subpopulations and cytokine treatments play a role in bone marrow supporting islet function in vivo by evaluating whether bone marrow is capable of migrating into islets as well as converting into insulin positive cells. We approached this aim by utilizing several bone marrow lineages and cytokine-treated bone marrow from green fluorescent protein (GFP) positive bone marrow donors. Sorted lineages of Mac-1⁺, Mac-1⁻, Sca⁺, Sca⁻, Sca⁻/Mac-1⁺ and Sca⁺/Mac-1⁻ from GFP positive mice were transplanted to irradiated C57BL6 GFP negative mice. Bone marrow from transgenic human ubiquitin C promoter GFP (uGFP, with strong signal) C57BL6 mice was transplanted into GFP negative C57BL6 recipients. After eight weeks, migration of GFP positive donor' bone marrow to the recipient's pancreatic islets was evaluated as the percentage of positive GFP islets/total islets. The results show that the most effective migration comes from the Sca⁺/Mac⁻ lineage and these cells, treated with cytokines for 48 hours, were found to have converted into insulin positive cells in pancreatic islets in vivo. This study suggests that bone marrow lineage positive cells and cytokine treatments are critical factors in determining whether bone marrow is able to migrate and form insulin producing cells in vivo. The mechanisms causing this facilitation as well as bone marrow converting to pancreatic beta cells still need to be investigated.

Impact of whole body irradiation and vascular endothelial growth factor-A on increased beta cell mass after bone marrow transplantation in a mouse model of diabetes induced by streptozotocin

AIMS/HYPOTHESIS

Recent studies have shown that bone marrow transplantation reduces hyperglycaemia in a mouse model of diabetes induced by streptozotocin. However, the essential factors for the improvement of hyperglycaemia by bone marrow transplantation have not been fully elucidated. The aim of this study was to search for such factors.

METHODS

We investigated the effect of irradiation to whole body, to abdomen alone or to whole body excluding abdomen, followed by infusion or no infusion of bone marrow cells. We also investigated the effect of bone marrow transplantation on beta cell-specific vascular endothelial growth factor-A gene (Vegfa) knockout mice.

RESULTS

Bone marrow transplantation improved streptozotocin-induced hyperglycaemia and partially restored islet mass. This change was associated with increased islet vascularisation. Among the other methods investigated, low-dose irradiation of the whole body without infusion of bone marrow cells also improved blood glucose level. In streptozotocin-treated beta cell-specific Vegfa knockout mice, which exhibit impaired islet vascularisation, bone marrow transplantation neither improved hyperglycaemia, relative beta cell mass nor islet vascularisation.

CONCLUSION/INTERPRETATION

Our results indicate that whole body irradiation is essential and sufficient for restoration of beta cell mass after streptozotocin treatment independent of infusion of bone marrow cells. Vascular endothelial growth factor-A produced in beta cells is also essential for this phenomenon.

Bone marrow or foetal liver cells fail to induce islet regeneration in diabetic Akita mice

BACKGROUND

In this study, we carried out bone marrow and foetal liver cell transplantation to determine if these cells could differentiate into pancreatic beta-cells or promote regeneration.

METHODS

To exclude an artificial or immunological influence for induction of diabetes to recipients, Akita mice, which develop diabetes spontaneously,were used. In addition, we used mice harbouring the transgenic green fluorescent protein (GFP) reporter for insulin 1 gene as donors to mark donor-derived beta-cells.

RESULTS

All transplanted Akita mice after intravenous injection showed full donor chimerism in peripheral blood analysis. Their diabetic state represented by blood glucose levels did not change after transplantation. In spite of examination of more than 200 islets in each group, we could not find GFP-positive cells in any of the recipients.

CONCLUSIONS

Bone marrow cells or foetal liver cells do not differentiate to new pancreatic beta-cells or promote regeneration in Akita mice, a non-chemical or non-immune model of diabetes.

IGF-I mediates regeneration of endocrine pancreas by increasing beta cell replication through cell cycle protein modulation in mice

AIMS/HYPOTHESIS

Recovery from diabetes requires restoration of beta cell mass. Igf1 expression in beta cells of transgenic mice regenerates the endocrine pancreas during type 1 diabetes. However, the IGF-I-mediated mechanism(s) restoring beta cell mass are not fully understood. Here, we examined the contribution of pre-existing beta cell proliferation and transdifferentiation of progenitor cells from bone marrow in IGF-I-induced islet regeneration.

METHODS

Streptozotocin (STZ)-treated Igf1-expressing transgenic mice transplanted with green fluorescent protein (GFP)-expressing bone marrow cells were used. Bone marrow cell transdifferentiation and beta cell replication were measured by GFP/insulin and by the antigen identified by monoclonal antibody Ki67/insulin immunostaining of pancreatic sections respectively. Key cell cycle proteins were measured by western blot, quantitative RT-PCR and immunohistochemistry.

RESULTS

Despite elevated IGF-I production, recruitment and differentiation of bone marrow cells to beta cells was not increased either in healthy or STZ-treated transgenic mice. In contrast, after STZ treatment, IGF-I overproduction decreased beta cell apoptosis and increased beta cell replication by modulating key cell cycle proteins. Decreased nuclear levels of cyclin-dependent kinase inhibitor 1B (p27) and increased nuclear localisation of cyclin-dependent kinase (CDK)-4 were consistent with increased beta cell proliferation. However, islet expression of cyclin D1 increased only after STZ treatment. In contrast, higher levels of cyclin-dependent kinase inhibitor 1A (p21) were detected in islets from non-STZ-treated transgenic mice.

CONCLUSIONS/INTERPRETATION

These findings indicate that IGF-I modulates cell cycle proteins and increases replication of pre-existing beta cells after damage. Therefore, our study suggests that local production of IGF-I may be a safe approach to regenerate endocrine pancreas to reverse diabetes.

In vitro differentiation of human adipose tissue-derived stem cells into cells with pancreatic phenotype by regenerating pancreas extract

Pancreas extract from regenerating pancreas after partial pancreatectomy is known to contain factors that induce islet neogenesis in animals with streptozotocin (STZ)-induced diabetes [A.A. Hardikar, R.R. Bhonde, Modulating experimental diabetes by treatment with cytosolic extract from the regenerating pancreas, Diabetes Res. Clin. Pract. 46 (1999) 203-211]. In this study, we evaluate the effects of regenerating pancreas extract (RPE) from 90% partially pancreatectomized rats on induction of pancreatic differentiation of human adipose tissue-derived stem cells (hASCs). We found that undifferentiated hASCs expressed OCT-3/4, Nanog, and REX-1, markers of embryonic stem cells (ESCs). Genes involved in early pancreas development showed increased expression in RPE-treated culture. Sox17 and IPF-1 were expressed only in RPE-treated culture. Immunocytochemical analysis showed C-peptide-positive cells in RPE-treated culture but not in undifferentiated hASCs. In conclusion, hASCs have the characteristics of ESCs and the potential to differentiate into pancreas cell lineages phenotypically in response to RPE.

Diabetes mellitus: an opportunity for therapy with stem cells?

In both Type 1 and 2 diabetes, insufficient numbers of insulin-producing beta-cells are a major cause of defective control of blood glucose and its complications. Restoration of damaged beta-cells by endocrine pancreas regeneration would be an ideal therapeutic option. The possibility of generating insulin-secreting cells with adult pancreatic stem or progenitor cells has been investigated extensively. The conversion of differentiated cells such as hepatocytes into beta-cells is being attempted using molecular insights into the transcriptional make-up of beta-cells. Additionally, the enhanced proliferation of beta-cells in vivo or in vitro is being pursued as a strategy for regenerative medicine for diabetes. Advances have also been made in directing the differentiation of embryonic stem cells into beta-cells. Although progress is encouraging, major gaps in our understanding of developmental biology of the pancreas and adult beta-cell dynamics remain to be bridged before a therapeutic application is made possible.

Amelioration of streptozotocin-induced diabetes in mice with cells derived from human marrow stromal cells

Background

Pluri-potent bone marrow stromal cells (MSCs) provide an attractive opportunity to generate unlimited glucose-responsive insulin-producing cells for the treatment of diabetes. We explored the potential for human MSCs (hMSCs) to be differentiated into glucose-responsive cells through a non-viral genetic reprogramming approach.

Methods and Findings

Two hMSC lines were transfected with three genes: PDX-1, NeuroD1 and Ngn3 without subsequent selection, followed by differentiation induction in vitro and transplantation into diabetic mice. Human MSCs expressed mRNAs of the archetypal stem cell markers: Sox2, Oct4, Nanog and CD34, and the endocrine cell markers: PDX-1, NeuroD1, Ngn3, and Nkx6.1. Following gene transfection and differentiation induction, hMSCs expressed insulin in vitro, but were not glucose regulated. After transplantation, hMSCs differentiated further and ∼12.5% of the grafted cells expressed insulin. The graft bearing kidneys contained mRNA of insulin and other key genes required for the functions of beta cells. Mice transplanted with manipulated hMSCs showed reduced blood glucose levels (from 18.9+/−0.75 to 7.63+/−1.63 mM). 13 of the 16 mice became normoglycaemic (6.9+/−0.64 mM), despite the failure to detect the expression of SUR1, a K⁺-ATP channel component required for regulation of insulin secretion.

Conclusions

Our data confirm that hMSCs can be induced to express insulin sufficient to reduce blood glucose in a diabetic mouse model. Our triple gene approach has created cells that seem less glucose responsive in vitro but which become more efficient after transplantation. The maturation process requires further study, particularly the in vivo factors influencing the differentiation, in order to scale up for clinical purposes.

Weighing up beta-cell mass in mice and humans: self-renewal, progenitors or stem cells?

Understanding how beta-cells maintain themselves in the adult pancreas is important for prioritizing strategies aimed at ameliorating or ideally curing different forms of diabetes. There has been much debate over whether beta-cell proliferation, as a means of self-renewal, predominates over the existence and differentiation of a pancreatic stem cell or progenitor cell population. This article describes the two opposing positions based largely on research in laboratory rodents and its extrapolation to humans.

Mesenchymal stem cells: biology and clinical potential in type 1 diabetes therapy

Mesenchymal stem cells (MSCs) can be derived from adult bone marrow, fat and several foetal tissues. In vitro, MSCs have the capacity to differentiate into multiple mesodermal and non-mesodermal cell lineages. Besides, MSCs possess immunosuppressive effects by modulating the immune function of the major cell populations involved in alloantigen recognition and elimination. The intriguing biology of MSCs makes them strong candidates for cell-based therapy against various human diseases. Type 1 diabetes is caused by a cell-mediated autoimmune destruction of pancreatic β-cells. While insulin replacement remains the cornerstone treatment for type 1 diabetes, the transplantation of pancreatic islets of Langerhans provides a cure for this disorder. And yet, islet transplantation is limited by the lack of donor pancreas. Generation of insulin-producing cells (IPCs) from MSCs represents an attractive alternative. On the one hand, MSCs from pancreas, bone marrow, adipose tissue, umbilical cord blood and cord tissue have the potential to differentiate into IPCs by genetic modification and/or defined culture conditions In vitro. On the other hand, MSCs are able to serve as a cellular vehicle for the expression of human insulin gene. Moreover, protein transduction technology could offer a novel approach for generating IPCs from stem cells including MSCs. In this review, we first summarize the current knowledge on the biological characterization of MSCs. Next, we consider MSCs as surrogate β-cell source for islet transplantation, and present some basic requirements for these replacement cells. Finally, MSCs-mediated therapeutic neovascularization in type 1 diabetes is discussed.

Mesenchymal stem cells contribute to insulin-producing cells upon microenvironmental manipulation in vitro

BACKGROUND

Extracellular microenvironment and intrinsic genetic programs determine the fate of stem cells. We observed whether mesenchymal stem cells (MSCs) contributed to insulin-producing cells in a manipulated microenvironment.

METHODS

We delivered pancreatic pieces into Niobium-Coated Dynamatrix to construct a simulated pancreatic microenvironment, upon which soluble cytokine exchange and direct cell-cell contact between MSCs and pancreatic cells could occur. Bone marrow-derived MSCs were cultured upon the microenvironment. Differentiated isletlike cells were observed under an inverted microscope. Insulin in supernates was measurement by enzyme-linked immunosorbent assay. Insulin and c-peptide expression were verified by fluorescent immunocytochemistry and fluorescence in situ hybridization. Apoptosis of isletlike masses in high-glucose DMEM was detected by FACS.

RESULTS

After 3 to 4 weeks in culture, typical isletlike masses were observed. Insulin secreted by differentiated cells (414.47+/-30.30 mIU/L) was much greater than that of undifferentiated cells (4.89+/-1.01 mIU/L; P<.05). Insulin and c-peptide expression were positive both in protein and mRNA levels. The transdifferentiated isletlike mass did not undergo apoptosis after another 3 weeks of culture in high-glucose DMEM.

CONCLUSION

This simulated injury microenvironment without induction guided MSCs to functional isletlike cells hopefully to replace beta cells.

Blood into beta-cells: can adult stem cells be used as a therapy for Type 1 diabetes?

In the past 10 years there have been substantial developments in adult stem cell research, and the transplantation of these cells now holds great promise for regenerative medicine, such as in the treatment of Type 1 diabetes. A large proportion of studies have focused on stem cells sourced from hematopoietic tissues: bone marrow, umbilical cord blood and peripheral blood. Attempts to transdifferentiate these cells into insulin-producing cells, both in vivo and in vitro, have produced conflicting results. Although insulin production and normalization of blood glucose levels have been described in some studies, the true mechanism of stem cell plasticity remains in question - are the functional changes seen due to true transdifferentiation or do they result from cell fusion or other factors? There is evidence that stem cell plasticity is a true phenomenon, but whether it will ever be of therapeutic benefit for Type 1 diabetes remains uncertain.

Beta-cell replacement for insulin-dependent diabetes mellitus

Beta-cell replacement is considered the optimal treatment for type 1 diabetes, however, it is hindered by a shortage of human organ donors. Given the difficulty of expanding adult beta cells in vitro, stem/progenitor cells, which can be expanded in tissue culture and induced to differentiate into multiple cell types, represent an attractive source for generation of cells with beta-cell properties. In the absence of well-characterized human pancreas progenitor cells, investigators are exploring the use of embryonic stem cells and stem/progenitor cells from other tissues. Once abundant surrogate beta cells are available, the challenge will be to protect them from recurring autoimmunity.

Stem cells as a treatment for chronic liver disease and diabetes

Advances in stem cell biology and the discovery of pluripotent stem cells have made the prospect of cell therapy and tissue regeneration a clinical reality. Cell therapies hold great promise to repair, restore, replace or regenerate affected organs and may perform better than any pharmacological or mechanical device. There is an accumulating body of evidence supporting the contribution of adult stem cells, in particular those of bone marrow origin, to liver and pancreatic islet cell regeneration. In this review, we will focus on the cell therapy for the diseased liver and pancreas by adult haematopoietic stem cells, as well as their possible contribution and application to tissue regeneration. Furthermore, recent progress in the generation, culture and targeted differentiation of human haematopoietic stem cells to hepatic and pancreatic lineages will be discussed. We will also explore the possibility that stem cell technology may lead to the development of clinical modalities for human liver disease and diabetes.

Generation of insulin-producing cells from human bone marrow mesenchymal stem cells by genetic manipulation

Beta cell replacement is a promising approach for treatment of type 1 diabetes; however, it is limited by a shortage of pancreas donors. The pluripotent MSC in adult bone marrow (BM) offer an attractive source of stem cells for generation of surrogate beta cells. BM-MSC can be obtained with relative ease from each patient, allowing potential circumvention of allograft rejection. Here, we report a procedure for expansion of BM-MSC in vitro and their differentiation into insulin-producing cells. The pancreatic duodenal homeobox 1 (Pdx1) gene was expressed in BM-MSC from 14 human donors, and the extent of differentiation of these cells toward the beta-cell phenotype was evaluated. RNA and protein analyses documented the activation of expression of all four islet hormones. However, the cells lacked expression of NEUROD1, a key transcription factor in differentiated beta cells. A significant insulin content, as well as glucose-stimulated insulin release, were demonstrated in vitro. Cell transplantation into streptozotocin-diabetic immunodeficient mice resulted in further differentiation, including induction of NEUROD1, and reduction of hyperglycemia. These findings were reproducible in BM-MSC from 9 of 14 donors of both sexes, ages 19-62. These results suggest a therapeutic potential for PDX1-expressing BM-MSC in beta-cell replacement in patients with type 1 diabetes.

Hematopoietic stem cells derived from adult donors are not a source of pancreatic beta-cells in adult nondiabetic humans

OBJECTIVE

Type 1 and type 2 diabetes are characterized by an approximately 98 and approximately 65% loss of pancreatic beta-cells, respectively. Efforts to reverse either form of diabetes increasingly focus on the possibility of promoting beta-cell replacement and/or regeneration. Islet transplantation has been explored, but it does not provide long-term insulin independence. One possible source of beta-cell regeneration is hematopoietic stem cells. In mice, there are conflicting data as to whether hematopoietic stem cells contribute to pancreatic beta-cells. We sought to establish whether hematopoietic stem cells (derived from adult donors) transdifferentiate into pancreatic beta-cells in adult humans.

RESEARCH DESIGN AND METHODS

We addressed this in 31 human pancreata obtained at autopsy from hematopoietic stem cell transplant recipients who had received their transplant from a donor of the opposite sex.

RESULTS

Whereas some donor-derived cells were observed in the nonendocrine pancreata, no pancreatic beta-cells were identified that were derived from donor hematopoietic stem cells, including two cases with type 2 diabetes.

CONCLUSIONS

We conclude that hematopoietic stem cells derived from adult donors contribute minimally to pancreatic beta-cells in nondiabetic adult humans. These data do not rule out the possibility that hematopoietic stem cells contribute to pancreatic beta-cells in childhood or in individuals with type 1 diabetes.

Bone marrow (BM) transplantation promotes beta-cell regeneration after acute injury through BM cell mobilization

There is controversy regarding the roles of bone marrow (BM)-derived cells in pancreatic beta-cell regeneration. To examine these roles in vivo, mice were treated with streptozotocin (STZ), followed by bone marrow transplantation (BMT; lethal irradiation and subsequent BM cell infusion) from green fluorescence protein transgenic mice. BMT improved STZ-induced hyperglycemia, nearly normalizing glucose levels, with partially restored pancreatic islet number and size, whereas simple BM cell infusion without preirradiation had no effects. In post-BMT mice, most islets were located near pancreatic ducts and substantial numbers of bromodeoxyuridine-positive cells were detected in islets and ducts. Importantly, green fluorescence protein-positive, i.e. BM-derived, cells were detected around islets and were CD45 positive but not insulin positive. Then to examine whether BM-derived cell mobilization contributes to this process, we used Nos3(-/-) mice as a model of impaired BM-derived cell mobilization. In streptozotocin-treated Nos3(-/-) mice, the effects of BMT on blood glucose, islet number, bromodeoxyuridine-positive cells in islets, and CD45-positive cells around islets were much smaller than those in streptozotocin-treated Nos3(+/+) controls. A series of BMT experiments using Nos3(+/+) and Nos3(-/-) mice showed hyperglycemia-improving effects of BMT to correlate inversely with the severity of myelosuppression and delay of peripheral white blood cell recovery. Thus, mobilization of BM-derived cells is critical for BMT-induced beta-cell regeneration after injury. The present results suggest that homing of donor BM-derived cells in BM and subsequent mobilization into the injured periphery are required for BMT-induced regeneration of recipient pancreatic beta-cells.

Placenta-derived multipotent stem cells induced to differentiate into insulin-positive cells

In the present study, we successfully isolated PDMSCs from human placental tissues. The RT-PCR results show that PDMSCs preserved the genetic characteristics of the primitive embryonic stage--Oct-4 and Nanog. By using serum-free medium supplemented essential growth factors and induction medium culture for 4 weeks, a monolayer of spindle-like PDMSCs gradually formed 3D spheroid bodies (SB-PDMSCs). By using real-time RT-PCR, early mRNA expressions of Pdx1, as well as the Sox17 and Foxa2 genes, were observed to be significantly activated in SB-PDMSCs, followed by the expression of mature pancreas-related genes (insulin, glucagon, and somatostatin). The high insulin content of SB-PDMSCs was further confirmed by ELISA assay, and the glucose dependency was demonstrated by the corresponding insulin secretion level. In a transplantation study of streptozotocin-pretreated nude mice, the restoration of normoglycemia in the SB-PDMSC treated group was further observed. In conclusion, these results indicate that PDMSCs are an excellent source for the induced differentiation of well-functioning insulin-positive cells. The potential of these insulin producing cells derived from PDMSCs was also demonstrated functionally by the demonstration of secreted insulin in vitro and effective control of blood glucose levels in vivo.

Towards stem-cell therapy in the endocrine pancreas

Many approaches of stem-cell therapy for the treatment of diabetes have been described. One is the application of stem cells for replacement of nonfunctional islet cells in the native endogenous pancreas; another one is the use of stem cells as an inexhaustible source for islet-cell transplantation. During recent years three types of stem cells have been investigated: embryonic stem cells, bone-marrow-derived stem cells and organ-bound stem cells. We discuss the advantages and limitations of these different cell types. The applicability for the treatment of dysfunction of beta cells in the pancreas has been demonstrated for all three cell types, but more-detailed understanding of the sequence of events during differentiation is required to produce fully functional insulin-producing cells.

Cellular pathways to beta-cell replacement

In the twenty-first century, diabetic patients are likely to be one of the major beneficiaries from the advancement of regenerative medicine through cellular therapies. Though the existence of a specific self-renewing stem cell within the pancreas is still far from clear, a surprising variety of cells within the pancreas can differentiate towards a beta-cell phenotype: ductular cells, periductular mesenchymal cells and beta-cells themselves can all give rise to new beta-cells. Extra-pancreatic adult somatic stem cells, in particular, those originating from bone marrow may also be capable of differentiating to beta-cells, though equally well the beneficial effects of bone marrow cells may reside in their contribution to the damaged islet vasculature. Forced expression of the beta-cell-specific transcription factor Pdx1 in hepatocytes also holds promise as a therapeutic strategy to increase insulin levels in diabetic individuals. Embryonic stem (ES) cells are clearly another possible source for generating beta-cells, but ES cells are beyond the scope of this review, which focuses on adult stem and progenitor cells capable of producing beta-cells. Despite considerable endeavour, we still have much to learn in the field of pancreatic regeneration prior to any clinically applicable therapy based upon adult stem cells.

Turning blood into beta cells - it's time for down-to-earth research

PURPOSE OF REVIEW

The recent findings in the field of blood or bone-marrow transdifferentiation into insulin-producing beta cells are summarized. Possible future goals in this exciting area of research are described.

RECENT FINDINGS

A number of recent studies examined the differentiation potential of bone marrow, peripheral blood, spleen or cord blood towards pancreatic beta cells, both in vivo and in vitro.

SUMMARY

The available in-vivo studies do not prove a physiological role of blood or bone marrow in the normal turnover, regeneration or repair of pancreatic islets. They rather argue against that notion. The in-vitro derivation of beta-like cells from blood or bone marrow has been reported by several groups. Nevertheless, there is still room for scepticism as robust and readily reproducible differentiation protocols are lacking and exhaustive analyses of bone marrow-derived beta-like cells have yet to be completed.

Cytokine mobilization of bone marrow cells and pancreatic lesion do not improve streptozotocin-induced diabetes in mice by transdifferentiation of bone marrow cells into insulin-producing cells

OBJECTIVE

Transdifferentiation of bone marrow cells (BMC) into insulin-producing cells might provide a new cellular therapy for type I diabetes, but its existence is controversial. Our aim was to determine if those cells could transdifferentiate, even at low frequency, into insulin-producing cells, in testing optimized experimental conditions.

METHODS

We grafted mice with total BMC, genetically labeled either ubiquitarily, or with a marker conditionally expressed under the control of the insulin beta-cell specific promoter. We treated some of the recipients with an agent toxic to beta-cells (streptozotocin) and with cytokines stem cell factor (SCF) and granulocyte-colony stimulating factor (G-CSF).

RESULTS

The contribution of grafted cells could be detected neither for natural turnover (n=6), nor for beta-cell regeneration after pancreatic lesion (n=7), 90 days post-transplantation. Cytokine mobilization of BMC in the blood stream, reported to favor their transdifferentiation into cardiac and neural cells, had never been tested before for beta-cell generation. Here, we showed that injection of SCF and G-CSF did not lead to a detectable level of transdifferentiation (n=7).

CONCLUSIONS

We conclude that BMC cannot spontaneously transdifferentiate into insulin-producing cells in vivo, even after beta-cell lesion and mobilization induced by cytokines. Interestingly, however, treatment by cytokines may have beneficial indirect effects on STZ-induced hyperglycaemia.

Extrapancreatic proinsulin/insulin-expressing cells in diabetes mellitus: is history repeating itself?

Insulin is a key regulator of life. Until 25 years ago, the pancreatic beta-cell was thought to be the only organ that produces insulin in the body. Insulin deficiency, whether absolute (in type 1) or relative (in type 2 diabetes), underlies the metabolic derangements in diabetes mellitus, and investigations on insulin have concentrated on pancreatic insulin production, its regulation and the metabolic consequences of insulin deficiency. The thymus was the next organ that was found to also produce insulin, a process that may tolerize the body to the molecule, protecting the host from developing autoimmune beta-cell destruction and (type 1) diabetes. However, now and then there were descriptions of promiscuous insulin production outside the pancreas. During our investigations on diabetes gene therapy in rodents, we serendipitously came across the presence of mysterious cells marked by proinsulin production in unexpected organs, some of which cells may underlie certain chronic diabetic complications. Starting with a historical perspective on insulin expression in brain and thymus, this review focuses mainly on unraveling the mystery of extrapancreatic extrathymic proinsulin/insulin expression in diabetes mellitus.

Multipotent stromal cells from human marrow home to and promote repair of pancreatic islets and renal glomeruli in diabetic NOD/scid mice

We tested the hypothesis that multipotent stromal cells from human bone marrow (hMSCs) can provide a potential therapy for human diabetes mellitus. Severe but nonlethal hyperglycemia was produced in NOD/scid mice with daily low doses of streptozotocin on days 1-4, and hMSCs were delivered via intracardiac infusion on days 10 and 17. The hMSCs lowered blood glucose levels in the diabetic mice on day 32 relative to untreated controls (18.34 mM +/- 1.12 SE vs. 27.78 mM +/- 2.45 SE, P = 0.0019). ELISAs demonstrated that blood levels of mouse insulin were higher in the hMSC-treated as compared with untreated diabetic mice, but human insulin was not detected. PCR assays detected human Alu sequences in DNA in pancreas and kidney on day 17 or 32 but not in other tissues, except heart, into which the cells were infused. In the hMSC-treated diabetic mice, there was an increase in pancreatic islets and beta cells producing mouse insulin. Rare islets contained human cells that colabeled for human insulin or PDX-1. Most of the beta cells in the islets were mouse cells that expressed mouse insulin. In kidneys of hMSC-treated diabetic mice, human cells were found in the glomeruli. There was a decrease in mesangial thickening and a decrease in macrophage infiltration. A few of the human cells appeared to differentiate into glomerular endothelial cells. Therefore, the results raised the possibility that hMSCs may be useful in enhancing insulin secretion and perhaps improving the renal lesions that develop in patients with diabetes mellitus.

Stem cells and diabetes treatment

Diabetes mellitus types 1 and 2 are characterized by absolute versus relative lack of insulin-producing beta cells, respectively. Reconstitution of a functional beta-cell mass by cell therapy--using organ donor islets of Langerhans--has been demonstrated to restore euglycaemia in the absence of insulin treatment. This remarkable achievement has stimulated the search for appropriate stem cell sources from which adequate expansion and maturation of therapeutic beta cells can be achieved. This recent activity is reviewed and presented with particular focus on directed differentiation from pluripotent embryonic stem cells (versus other stem/progenitor cell sources) based on knowledge from pancreatic beta-cell development and the parallel approach to controlling endogenous beta-cell neogenesis.