Modulating experimental diabetes by treatment with cytosolic extract from the regenerating pancreas

PRDX6 Promotes the Differentiation of Human Mesenchymal Stem (Stromal) Cells to Insulin-Producing Cells

Mesenchymal stem cells (MSCs) can be differentiated in vitro to form insulin-producing cells (IPCs). However, the proportion of induced cells is modest. Extracts from injured pancreata of rodents promoted this differentiation, and three upregulated proteins were identified in these extracts. The aim of this study was to evaluate the potential benefits of adding these proteins to the differentiation medium alone or in combination. Our results indicate that the proportion of IPCs among the protein(s)-supplemented samples was significantly higher than that in the samples with no added proteins. The yield from samples supplemented with PRDX6 alone was 4-fold higher than that from samples without added protein. These findings were also supported by the results of fluorophotometry. Gene expression profiles revealed higher levels among protein-supplemented samples. Significantly higher levels of GGT, SST, Glut-2, and MafB expression were noted among PRDX6-treated samples. There was a stepwise increase in the release of insulin and c-peptide, as a function of increasing glucose concentrations, indicating that the differentiated cells were glucose sensitive and insulin responsive. PRDX6 exerts its beneficial effects as a result of its biological antioxidant properties. Considering its ease of use as a single protein, PRDX6 is now routinely used in our differentiation protocols.

Non-Coding RNA in Pancreas and β-Cell Development

In this review, we provide an overview of the current knowledge on the role of different classes of non-coding RNAs for islet and β-cell development, maturation and function. MicroRNAs (miRNAs), a prominent class of small RNAs, have been investigated for more than two decades and patterns of the roles of different miRNAs in pancreatic fetal development, islet and β-cell maturation and function are now emerging. Specific miRNAs are dynamically regulated throughout the period of pancreas development, during islet and β-cell differentiation as well as in the perinatal period, where a burst of β-cell replication takes place. The role of long non-coding RNAs (lncRNA) in islet and β-cells is less investigated than for miRNAs, but knowledge is increasing rapidly. The advent of ultra-deep RNA sequencing has enabled the identification of highly islet- or β-cell-selective lncRNA transcripts expressed at low levels. Their roles in islet cells are currently only characterized for a few of these lncRNAs, and these are often associated with β-cell super-enhancers and regulate neighboring gene activity. Moreover, ncRNAs present in imprinted regions are involved in pancreas development and β-cell function. Altogether, these observations support significant and important actions of ncRNAs in β-cell development and function.

Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells into Insulin-Producing Cells: Evidence for Further Maturation In Vivo

The aim of this study was to provide evidence for further in vivo maturation of insulin-producing cells (IPCs) derived from human bone marrow-derived mesenchymal stem cells (HBM-MSCs). HBM-MSCs were obtained from three insulin-dependent type 2 diabetic volunteers. Following expansion, cells were differentiated according to a trichostatin-A/GLP protocol. One million cells were transplanted under the renal capsule of 29 diabetic nude mice. Blood glucose, serum human insulin and c-peptide levels, and glucose tolerance curves were determined. Mice were euthanized 1, 2, 4, or 12 weeks after transplantation. IPC-bearing kidneys were immunolabeled, number of IPCs was counted, and expression of relevant genes was determined. At the end of in vitro differentiation, all pancreatic endocrine genes were expressed, albeit at very low values. The percentage of IPCs among transplanted cells was small (≤3%). Diabetic animals became euglycemic 8 ± 3 days after transplantation. Thereafter, the percentage of IPCs reached a mean of ~18% at 4 weeks. Relative gene expression of insulin, glucagon, and somatostatin showed a parallel increase. The ability of the transplanted cells to induce euglycemia was due to their further maturation in the favorable in vivo microenvironment. Elucidation of the exact mechanism(s) involved requires further investigation.

Secreted factors from dental pulp stem cells improve glucose intolerance in streptozotocin-induced diabetic mice by increasing pancreatic β-cell function

OBJECTIVE

Many studies have reported that stem cell transplantation promotes propagation and protection of pancreatic β-cells in streptozotocin (STZ)-induced diabetic mice without the differentiation of transplanted cells into pancreatic β-cells, suggesting that the improvement is due to a paracrine effect of the transplanted cells. We investigated the effects of factors secreted by dental pulp stem cells from human exfoliated deciduous teeth (SHED) on β-cell function and survival.

RESEARCH DESIGN AND METHODS

Conditioned medium from SHED (SHED-CM) was collected 48 h after culturing in serum-free Dulbecco's modified Eagle's medium (DMEM). The insulin levels in SHED-CM and serum-free conditioned media from human bone marrow-derived mesenchymal stem cells (BM-CM) were undetectable. STZ-induced diabetic male C57B/6J mice were injected with DMEM as a control, SHED-CM, exendin-4 (Ex-4), or BM-CM for 14 days. Mouse pancreatic β-cell line MIN6 cells were incubated with different concentrations of STZ with SHED-CM, DMEM, Ex-4, or BM-CM for 6 h.

RESULTS

Administration of 1 mL of SHED-CM twice a day improved glucose intolerance in STZ-induced diabetic mice and the effect continued for 20 days after the end of treatment. SHED-CM treatment increased pancreatic insulin content and β-cell mass through proliferation and an intraperitoneal glucose tolerance test revealed enhanced insulin secretion. Incubation of MIN6 cells (a mouse pancreatic β-cell line) with SHED-CM enhanced insulin secretion in a glucose concentration-dependent manner and reduced STZ-induced cell death, indicating that the amelioration of hyperglycemia was caused by the direct effects of SHED-CM on β-cell function and survival. These effects were more pronounced than with the use of Ex-4, a conventional incretin-based drug, and BM-CM, which is a medium derived from other stem cells.

CONCLUSIONS

These findings suggest that SHED-CM provides direct protection and encourages the propagation of β-cells, and has potential as a novel strategy for treatment of diabetes.

Characterization of Streptozotocin-induced Diabetic Rats and Pharmacodynamics of Insulin Formulations

Morphological and functional changes of rat pancreatic islets caused by administration of streptozotocin (STZ) and the bioavailability of insulin formulations administered to STZ-induced diabetic rats with fasting (12 h) or non-fasting were investigated. Islets isolated from normal rats maintained a good three-dimensional structure and the islet yield was 962.5+/-86.5 islet equivalent number (IEQ, islets converted to an average diameter of 150 microm). In the diabetic group (>500 mg/ml blood glucose), the islet yield was only 44.4+/-8.3 IEQ and the islet was severely damaged. The minimum reduction of blood glucose of each formulation, such as insulin solution, microcrystal, and insulin microcrystal capsule, was shown to be 11.3, 11.0, and 16.3 mg/dl, respectively, at 6 h in fasting with diabetic rats. These results indicated that the administration of insulin formulations to the fasting groups increased the severe hypoglycemic effect of insulin action more than in non-fasting diabetic rats. The diabetic rat with fasting has a regulatory disorder in maintaining the blood glucose level. Accordingly, the validity of pharmacological availability as an optimal modeling of insulin formulations is best in non-fasting STZ-induced diabetic rats.

Efficient and simple production of insulin-producing cells from embryonal carcinoma stem cells using mouse neonate pancreas extract, as a natural inducer

An attractive approach to replace the destroyed insulin-producing cells (IPCs) is the generation of functional β cells from stem cells. Embryonal carcinoma (EC) stem cells are pluripotent cells which can differentiate into all cell types. The present study was carried out to establish a simple nonselective inductive culture system for generation of IPCs from P19 EC cells by 1–2 weeks old mouse pancreas extract (MPE). Since, mouse pancreatic islets undergo further remodeling and maturation for 2–3 weeks after birth, we hypothesized that the mouse neonatal MPE contains essential factors to induce in vitro differentiation of pancreatic lineages. Pluripotency of P19 cells were first confirmed by expression analysis of stem cell markers, Oct3/4, Sox-2 and Nanog. In order to induce differentiation, the cells were cultured in a medium supplemented by different concentrations of MPE (50, 100, 200 and 300 µg/ml). The results showed that P19 cells could differentiate into IPCs and form dithizone-positive cell clusters. The generated P19-derived IPCs were immunoreactive to proinsulin, insulin and insulin receptor beta. The expression of pancreatic β cell genes including, PDX-1, INS1 and INS2 were also confirmed. The peak response at the 100 µg/ml MPE used for investigation of EP300 and CREB1 gene expression. When stimulated with glucose, these cells synthesized and secreted insulin. Network analysis of the key transcription factors (PDX-1, EP300, CREB1) during the generation of IPCs resulted in introduction of novel regulatory candidates such as MIR17, and VEZF1 transcription factors, as well as MORN1, DKFZp761P0212, and WAC proteins. Altogether, we demonstrated the possibility of generating IPCs from undifferentiated EC cells, with the characteristics of pancreatic β cells. The derivation of pancreatic cells from EC cells which are ES cell siblings would provide a valuable experimental tool in study of pancreatic development and function as well as rapid production of IPCs for transplantation.

Hyperactivity of ON-type retinal ganglion cells in streptozotocin-induced diabetic mice

Impairment of visual function has been detected in the early stage of diabetes but the underlying neural mechanisms involved are largely unknown. Morphological and functional alterations of retinal ganglion cells, the final output neurons of the vertebrate retina, are thought to be the major cause of visual defects in diabetes but direct evidence to support this notion is limited. In this study we investigated functional changes of retinal ganglion cells in a type 1-like diabetic mouse model. Our results demonstrated that the spontaneous spiking activity of ON-type retinal ganglion cells was increased in streptozotocin-diabetic mice after 3 to 4 months of diabetes. At this stage of diabetes, no apoptotic signals or cell loss were detected in the ganglion cell layer of the retina, suggesting that the functional alterations in ganglion cells occur prior to massive ganglion cell apoptosis. Furthermore, we found that the increased activity of ON-type ganglion cells was mainly a result of reduced inhibitory signaling to the cells in diabetes. This novel mechanism provides insight into how visual function is impaired in diabetic retinopathy.

Role of injured pancreatic extract promotes bone marrow-derived mesenchymal stem cells efficiently differentiate into insulin-producing cells

Mesenchymal stem cells (MSCs) can be successfully induced to differentiate into insulin-producing cells （IPCs) by a variety of small molecules and cytokines in vitro. However, problems remain, such as low transdifferentiation efficiency and poor maturity of trans-differentiated cells. The damaged pancreatic cells secreted a large amount of soluble proteins, which were able to promote pancreative islet regeneration and MSCs differentiation. In this study, we utilized the rat injured pancreatic tissue extract to modulate rat bone marrow-derived MSCs differentiation into IPCs by the traditional two-step induction. Our results showed that injured pancreatic tissue extract could effectively promote the trans-differentiation efficiency and maturity of IPCs by the traditional induction. Moreover, IPCs were able to release more insulin in a glucose-dependent manner and ameliorate better the diabetic conditions of streptozotocin (STZ)-treated rats. Our study provides a new strategy to induce an efficient and directional differentiation of MSCs into IPCs.

β-cell regeneration: the pancreatic intrinsic faculty

Type I diabetes (T1D) patients rely on cumbersome chronic injections of insulin, making the development of alternate durable treatments a priority. The ability of the pancreas to generate new β-cells has been described in experimental diabetes models and, importantly, in infants with T1D. Here we discuss recent advances in identifying the origin of new β-cells after pancreatic injury, with and without inflammation, revealing a surprising degree of cell plasticity in the mature pancreas. In particular, the inducible selective near-total destruction of β-cells in healthy adult mice uncovers the intrinsic capacity of differentiated pancreatic cells to spontaneously reprogram to produce insulin. This opens new therapeutic possibilities because it implies that β-cells can differentiate endogenously, in depleted adults, from heterologous origins.

Mesenchymal stem cells derived from bone marrow of diabetic patients portrait unique markers influenced by the diabetic microenvironment

Cellular microenvironment is known to play a critical role in the maintenance of human bone marrow-derived mesenchymal stem cells (BM-MSCs). It was uncertain whether BM-MSCs obtained from a 'diabetic milieu' (dBM-MSCs) offer the same regenerative potential as those obtained from healthy (non-diabetic) individuals (hBM-MSCs). To investigate the effect of diabetic microenvironment on human BM-MSCs, we isolated and characterized these cells from diabetic patients (dBM-MSCs). We found that dBM-MSCs expressed mesenchymal markers such as vimentin, smooth muscle actin, nestin, fibronectin, CD29, CD44, CD73, CD90, and CD105. These cells also exhibited multilineage differentiation potential, as evident from the generation of adipocytes, osteocytes, and chondrocytes when exposed to lineage specific differentiation media. Although the cells were similar to hBM-MSCs, 6% (3/54) of dBM-MSCs expressed proinsulin/C-peptide. Emanating from the diabetic microenvironmental milieu, we analyzed whether in vitro reprogramming could afford the maturation of the islet-like clusters (ICAs) derived from dBM-MSCs. Upon mimicking the diabetic hyperglycemic niche and the supplementation of fetal pancreatic extract, to differentiate dBM-MSCs into pancreatic lineage in vitro, we observed rapid differentiation and maturation of dBM-MSCs into islet-like cell aggregates. Thus, our study demonstrated that diabetic hyperglycemic microenvironmental milieu plays a major role in inducing the differentiation of human BM-MSCs in vivo and in vitro.

Differentiation of human umbilical cord blood-derived mononuclear cells to endocrine pancreatic lineage

Generation of insulin-producing cells remains a major limitation for cellular replacement therapy in treatment of diabetes. To understand the potential of human umbilical cord blood (hUCB)-derived mononuclear cells (MNCs) in cell replacement therapy for diabetes, we studied MNCs isolated from 270 human umbilical cord blood samples. We characterized these by immunostaining and real-time PCR and studied their ability to differentiate into insulin-producing cells. We observe that freshly isolated MNCs as well as mesenchymal-like cells grown out by in vitro culture of isolated MNCs express key pancreatic transcription factors: pdx1, ngn3, isl1, brn4 and pax6. However, after 32-fold expansion, MNCs show decreased abundance of pdx1 and ngn3, indicating that islet/pancreatic progenitors detected in freshly isolated MNCs die or are diluted out during in vitro expansion. We therefore transplanted freshly isolated MNCs in NOD/SCID (immuno-incompetent) or FVB/NJ (immuno-competent) mice to check their ability to differentiate into insulin-producing cells. We observe that after 9 weeks of transplantation, approximately 25% grafts exhibit human insulin-producing (16% immunopositive) cells. The number and abundance of pro-insulin transcript-containing cells increased when the animals underwent partial pancreatectomy, 15 days after transplantation. Our results indicate that such hUCB-derived MNC population contains a subset of "pancreas-committed" cells that have the potential to differentiate into insulin-producing cells in vivo. Further studies in understanding the differentiation potential of this subset of pancreas-committed hUCB-derived MNCs will provide us with an autologous source of "lineage-committed" progenitors for cell replacement therapy in 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.

Expression, purification, and refolding of mouse islet neogenesis associated protein-related protein for NMR studies

Islet neogenesis associated protein-related protein (INGAPrP) is thought to be involved in the differentiation of non-insulin-producing cells to insulin-secreting cells. INGAPrP is a mouse gene product that has a 72% identical amino acid sequence to a known islet-generating factor, hamster islet-neogenesis-associated protein (INGAP), which acts by differentiating pancreatic ductal cells into beta-cells. The three-dimensional structure of these proteins is unknown. The structure would provide information about the conformation of the active portion of INGAP, the so-called INGAP pentadecapeptide, leading to a well-defined target for rational drug design. An efficient procedure for the production of INGAPrP would facilitate the process of structure determination. We have successfully produced and isolated (15)N-labeled INGAPrP by expression in Escherichia coli Rosetta (DE3) cells in Spectra-9 media followed by a two-step purification and refolding protocol. The hexahistidine tag engineered at the N-terminus of the protein is used in the first step for standard immobilized-metal affinity chromatography purification under denaturing conditions. The secondary purification step utilizes a gel permeation chromatography column, producing homogeneous INGAPrP as well as refolding the protein. To verify that the protein was folded, we performed a (1)H-(15)N HSQC NMR experiment that showed excellent dispersion of signals, indicative of a folded protein. We also performed circular dichroism experiments, which demonstrated the presence of secondary structure. In summary, we report the first expression and isolation of INGAPrP, as well as demonstrate that our method produces a folded protein, which is necessary for structure determination.

Approaches towards endogenous pancreatic regeneration

The phenomenon of pancreatic regeneration in mammals has been well documented. It has been shown that pancreatic tissue is able to regenerate in several species of mammal after surgical insult. This tissue is also known to have the potential to maintain or increase its beta-cell mass in response to metabolic demands during pregnancy and obesity. Since deficiency in beta-cell mass is the hallmark of most forms of diabetes, it is worthwhile understanding pancreatic regeneration in the context of this disease. With this view in mind, this article aims to discuss the potential use in clinical strategies of knowledge that we obtained from studies carried out in animal models of diabetes. Approaches to achieve this goal involve the use of biomolecules, adult stem cells and gene therapy. Various molecules, such as glucagon-like peptide-1, beta-cellulin, nicotinamide, gastrin, epidermal growth factor-1 and thyroid hormone, play major roles in the initiation of endogenous islet regeneration in diabetes. The most accepted hypothesis is that these molecules stimulate islet precursor cells to undergo neogenesis or to induce replication of existing beta-cells, emphasizing the importance of pancreas-resident stem/progenitor cells in islet regeneration. Moreover, the potential of adult stem cell population from bone marrow, umbilical cord blood, liver, spleen, or amniotic membrane, is also discussed with regard to their potential to induce pancreatic regeneration.

In vitro trans-differentiation of rat mesenchymal cells into insulin-producing cells by rat pancreatic extract

Recent reports have suggested that mesenchymal cells derived from bone marrow may differentiate into not only mesenchymal lineage cells but also other lineage cells. There is possibility for insulin-producing cells (IPCs) to be differentiated from mesenchymal cells. We used self-functional repair stimuli of stem cells by partial injury. Rat pancreatic extract (RPE) from the regenerating pancreas (2 days after 60% pancreatectomy) was treated to rat mesenchymal cells. After the treatment of RPE, they made clusters like islet of Langerhans within a week and expressed four pancreatic endocrine hormones; insulin, glucagon, pancreatic polypeptide, and somatostatin. Moreover, IPCs released insulin in response to normal glucose challenge. Here we demonstrate that the treatment of RPE can differentiate rat mesenchymal cells into IPCs which can be a potential source for the therapy of diabetes.

Reversal of experimental diabetes by multiple bone marrow transplantation

Therapeutic utility of bone marrow transplantation in diabetic patients to overcome deficient beta-cell population is an attractive proposal. However, the status of bone marrow stem cells (BMSCs) under hyperglycemia is not known. In the present study, we investigated the status of BMSCs in experimental-diabetic mice and demonstrated the rescue of experimental diabetes by multiple diabetic bone marrow transplantation. Our flow-cytometry analysis for CD34+, CD45+, flk1+, c-kit+, and CD34+CD45+ revealed that BMSC reserve remains unaffected under sustained hyperglycemia. We found that single injection of diabetic bone marrow cells (approximately 10(6)) resulted in reduction and stabilization of moderate hyperglycemia. However, multiple injections at regular intervals led to restoration of stabilized normoglycemia during a 30 day follow-up. Reversal of diabetes was evidenced by disappearance of hyperglycemia, normal intra-peritoneal glucose tolerance test, and histology and morphometry of pancreas. The present study thus demonstrates that diabetic bone marrow retains its stemness and potential to induce pancreatic regeneration on transplantation.

Existence of islet regenerating factors within the pancreas

Reduction in the functional mass of beta-cells is a common denominator in most forms of diabetes. Since the replicative potential of beta-cells is limited, the search for factors that trigger islet neogenesis becomes imperative. Here we tested the hypothesis that regenerating factors for the pancreas are either secreted by or present within the pancreatic milieu itself. For this purpose, we intraperitoneally injected pancreatic cell culture supernatant (PCCS), from normal pancreas, into streptozotocin (STZ)-induced diabetic mice for 15 consecutive days. The PCCS-treated mice showed sustained reversal in 77.77% of experimental diabetic mice as evidenced by restoration of normoglycemia, increase in serum insulin levels and occurrence of neo islets in histopathological studies during a two month follow up, as opposed to the control diabetic mice which remained hyperglycemic throughout. In order to examine the potential of PCCS to bring about the regeneration of islets, we treated intra-islet precursor cells with PCCS in vitro, which led to the neogenesis of islets as evidenced by dithiozone and insulin immunostaining. These findings substantiate our hypothesis and make the search for regenerative factors converge towards the pancreas and its immediate surroundings. Such regenerative approaches, in combination with other therapeutic strategies to promote islet neogenesis may, in future, provide a cure and/or better means for the control and management of diabetes.

Enhancement of mouse pancreatic regeneration and HIT-T15 cell proliferation with rat pancreatic extract

In this study, the effects of rat pancreatic extract (RPE) on regeneration of impaired mouse pancreas and proliferation of beta-cell line (HIT-T15) were investigated. RPE from the regenerating pancreas (2 days after 60% pancreatectomy) was treated to cure streptozotocin (STZ) induced diabetes in BALB/c mice. RPE-treated BALB/c mice for 21 consecutive days became euglycemic by day 30 and remained normoglycemic during a 150 day follow-up. Saline treated mice remained hyperglycemic sustained uncontrolled hyperglycemia. Islet neogenesis was observed in RPE-treated mice and confirmed by use of immunocytochemistry. Morphometric analysis of pancreas in reverted RPE-treated mice showed a new population of small islets compared with saline controls and an increased islet number. When HIT-T15 cells were treated with RPE, HIT-T15 cell proliferation and insulin secretion increased with increases in the RPE concentration. These results imply that RPE have the regeneration factors and help in the cure of diabetes.

Models of pancreatic regeneration in diabetes

The number of functionally intact beta cells in the islet organ is of decisive importance for the development, course and outcome of diabetes mellitus. Generally speaking, the total beta-cell mass reflects the balance between the renewal and loss of these cells. Assuming that virtually all forms of diabetes mellitus are characterized by an insufficient extent of beta cell replication needed to compensate for the loss or dysfunction of beta cells occurring in diabetes, elucidation of the regenerating potential in experimentally induced diabetic animal would be of interest as alternative therapy for diabetes. Here we have attempted to take a stock of different models developed in the last few years, which permit investigation of regenerative process from various angles. The review focuses on factors responsible for induction of islet neogenesis in the diabetic pancreas, ultimately leading to pancreatic regeneration and possible reversal of diabetes. On the whole the study of these models will enhance our understanding of regenerative potential of diabetic pancreas and factors necessary to trigger stem cells' population within the pancreas so as to suggest an alternative therapeutic approach for the control and/or cure of diabetes.