A secretory function of human insulin-producing cells in vivo

BACKGROUND: Mesenchymal stem cells derived from human umbilical cord blood (UCB-MSCs) have good research and application prospects in the treatment of diabetes. We once induced UCB-MSCs to differentiate into insulin-producing cells (IPCs) in vitro, but we did not know the functions of these cells in vivo. The aim of this study was to assess the functional effects of IPCs on insulin secretion and their role in the treatment of diabetes in vivo. METHODS: UCB-MSCs were induced to IPCs by an inducing protocol with extracellular matrix gel. BALB/C nude mice were made hyperglycemic by intraperitoneal injection of streptozotocin. The diabetic mice were transplanted with 1x10(7) IPCs under the renal capsule or with phosphate-buffered saline as a control. After transplantation, the grafts were analyzed by immunocytochemistry for the expression of human insulin; the serum human insulin levels were measured; and blood glucose and body weight status were monitored. RESULTS: Immunofluorescence showed that numerous IPCs under the kidney capsule were insulin-positive. On day 14 after transplantation, the serum human insulin level of the treatment group (n=9) averaged 0.44 +/- 0.12 mU/L, which was higher than that of the control group (n=9) that did not express insulin (t=10.842, P<0.05). The diabetic mice remained hyperglycemic and kept losing body weight after IPC transplantation, and there was no significant difference in the control group. CONCLUSION: IPCs differentiated from UCB-MSCs generate human insulin in diabetic mice, but more research is needed to make further use of them to regulate hyperglycemia and body weight in vivo. (Hepatobiliary Pancreat Dis Int 2009; 8: 255-260)

In vitro-derived insulin-producing cells modulate Th1 immune responses and induce IL-10 in streptozotocin-induced mouse model of pancreatic insulitis

Background: Insulitis is defined by the presence of immune cells infiltrating in the pancreatic islets that might progress into the complete β-cell loss. The immunomodulatory properties of bone marrow-derived mesenchymal stem cells(BM-MSCs) have attracted much attention. This study aimed to evaluate the possible immunomodulatory effects of rat BM-MSCs and MSCs-derived insulin-producing cells(IPCs) in a mouse model of pancreatic insulitis. Methods: Insulitis was induced in BALB/c mice using five consecuti ve doses of streptozotocin. MSCs or IPCs were directly injected into the pancreas of mice and their effects on the expression of Th subsetsrelated genes were evaluated. Results: Both BM-MSCs and IPCs significantly reduced the expression of pancreatic Th1-related IFN-γ( P < 0.001 and P < 0.05, respectively) and T-bet genes(both P < 0.001). Moreover, the expression of IL-10 gene was significantly increased in IPC-treated compared to BM-MSC-or PBS-treated mice( P < 0.001 both comparisons). Conclusions: BM-MSCs and IPCs could successfully suppress pathologic Th1 immune responses in the mouse model of insulitis. However, the marked increase in IL-10 gene expression by IPCs compared to BM-MSCs suggests that their simultaneous use at the initial phase of autoimmune diabetes might be a better option to reduce inflammation but these results need to be verified by further experiments.

Role of miR-128/216a Regulating Isl1 Expression during Differentiation of Human Umbilical Cord Mesenchymal Stem Cells into Insulin-Producing Cells

Islet-1(Isl1),a LIM homeodomain protein,is expressed in the embryonic pancreatic epithelium.As a key transcription factor,Isl1 can not only regulate insulin gene expression in normal glucose condition but also maintainβ-cell function and impact pancreaticβ-cell target genes.Some experiments have suggested that Micro RNA(miRNA)can play a critical role during the induction of insulinproducing cells(IPCs).However,it is unclear whether miRNA may regulate Isl1 expression during differentiation of human umbilical cord mesenchymal stem cells(HUMSCs)into IPCs.In this investigation,we induced HUMSCs into IPCs with a modified two-step protocol,activin A,retinoic acid(step1)and conophylline,nicotinamide(step2).To find the miRNA regulating Isl1 expression,we respectively used Target Scan,miRDB and RNAhybrid to predict and got the result,miR-128 and miR-216a.The miRNAs can inhibit Isl1 expression by dual luciferase assay.The results of real-time Polymerase Chain Reaction(PCR)showed that Isl1 expression level was almost reciprocal to that of miR-128 and miR-216a during differentiation of HUMSCs into IPCs.Furthermore,over-expression of miR-128 or miR-216a downregulated expression levels of Isl1 and Maf A.Therefore,miR-128 or miR-216a may regulate expression of islet-specific transcription factors to control differentiation of HUMSCs into IPCs.

Human umbilical cord mesenchymal stem cells derived from Wharton＇s jelly differentiate into insulin-producing cells in vitro

Background Islet transplantation is an effective way of reversing type Ⅰ diabetes. However, islet transplantation is hampered by issues such as immune rejection and shortage of donor islets. Mesenchymal stem cells can differentiate into insulin-producing cells. However, the potential of human umbilical cord mesenchymal stem cells （huMSCs） to become insulin-producing cells remains undetermined.Methods We isolated and induced cultured huMSCs under islet cell culture conditions. The response of huMSCs were monitored under an inverted phase contrast microscope. Immunocytochemical and immunofluorescence staining methods were used to measure insulin and glucagon protein levels. Reverse transcription-polymerase chain reaction （RT-PCR） was performed to detect gene expression of human insulin and PDX-1. Dithizone-staining was employed to determine the zinc contents in huMSCs. Insulin secretion was also evaluated through radioimmunoassay.Results HuMSCs induced by nicotinamide and β-mercaptoethanol or by neurogenic differentiation 1 gene （NeuroD1）transfection gradually changed morphology from typically elongated fibroblast-shaped cells to round cells. They had a tendency to form clusters. Immunocytochemical studies showed positive expression of human insulin and glucagon in these cells in response to induction. RT-PCR experiments found that huMSCs expressed insulin and PDX-1 genes following induction and dithizone stained the cytoplasm of huMSCs a brownish red color after induction. Insulin secretion in induced huMSCs was significantly elevated compared with the control group （t=6.183, P〈0.05）.Conclusions HuMSCs are able to differentiate into insulin-producing cells in vitro. The potential use of huMSCs in βcell replacement therapy of diabetes needs to be studied further

Conophylline Promotes the Proliferation of Immortalized Mesenchymal Stem Cells Derived from Fetal Porcine Pancreas (iPMSCs)

Conophylline, is a bis （indole） alkaloid consisting of two pentacyclic aspidosperma skeletons, isolated from Tabernaemontana divaricata, which has been found to induce β-cell differentiation in rat pancreatic acinar carcinoma cells and in cultured rat pancreatic tissue. However, the precise role of conophylline in the growth and survival of immortalized pancreatic mesenchymal stem cells （iPMSCs） derived from fetal porcine pancreas were not understood at present. To determine whether this molecule is involved in controlling the proliferation of iPMSCs, we examined the effects of conophylline on iPMSCs. We found that conophylline can robustly stimulate iPMSCs proliferation, even promote their potential differentiation into islet-like clusters analyzed by cell counting, morphology, RT-PCR and real-time PCR, Western blotting, glucose-stimulated insulin release and insulin content analysis. The effects of conophylline were inhibited by LY294002, which is the inhibitor of the PI3K pathway. These results suggest that conophylline plays a key role in the regulation of cell mass proliferation, maintenance of the undifferentiated state of iPMSCs and also promotes iPMSCs differentiated into insulin-producing cells.

Comparison between the therapeutic effects of differentiated and undifferentiated Wharton’s jelly mesenchymal stem cells in rats with streptozotocin-induced diabetes

BACKGROUND Despite the availability of current therapies,including oral antidiabetic drugs and insulin,for controlling the symptoms caused by high blood glucose,it is difficult to cure diabetes mellitus,especially type 1 diabetes mellitus.AIM Cell therapies using mesenchymal stem cells(MSCs)may be a promising option.However,the therapeutic mechanisms by which MSCs exert their effects,such as whether they can differentiate into insulin-producing cells (IPCs) beforetransplantation, are uncertain.METHODSIn this study, we used three types of differentiation media over 10 d to generateIPCs from human Wharton’s jelly MSCs (hWJ-MSCs). We further transplantedthe undifferentiated hWJ-MSCs and differentiated IPCs derived from them intothe portal vein of rats with streptozotocin-induced diabetes, and recorded thephysiological and pathological changes.RESULTSUsing fluorescent staining and C-peptide enzyme-linked immunoassay, we wereable to successfully induce the differentiation of hWJ-MSCs into IPCs.Transplantation of both IPCs derived from hWJ-MSCs and undifferentiated hWJMSCshad the therapeutic effect of ameliorating blood glucose levels andimproving intraperitoneal glucose tolerance tests. The transplanted IPCs homedto the pancreas and functionally survived for at least 8 wk after transplantation,whereas the undifferentiated hWJ-MSCs were able to improve the insulitis andameliorate the serum inflammatory cytokine in streptozotocin-induced diabeticrats.CONCLUSIONDifferentiated IPCs can significantly improve blood glucose levels in diabetic ratsdue to the continuous secretion of insulin by transplanted cells that survive in theislets of diabetic rats. Transplantation of undifferentiated hWJ-MSCs cansignificantly improve insulitis and re-balance the inflammatory condition indiabetic rats with only a slight improvement in blood glucose levels.

Anti-diabetic Activity of Zhenqing Recipe and Ligustri Lucidi Fructus in Type 2 Diabetic Rats

Objective To investigate the influence of Zhenqing Recipe(ZQR)and Ligustri Lucidi Fructus(LLF)on diabetic rats and its possible mechanism.Methods The model of type 2 diabetic rats was established by feeding a high-sucrose-high-fat diet and injecting a low dose of Streptozotocin in Wistar rats.The model rats were randomly divided into three groups:diabetic model,ZQR-treated,and LLF-treated groups for 8-weeks treatment.The normal Wistar rats were as a normal control group.Results The level of fasting blood glucose in ZQR and LLF groups was decreased compared with model group(P<0.01,0.05,respectively).Both ZQR and LLF markedly reduced serum triglycerides(P<0.01,0.05,respectively),and increased the insulin sensitivity index(P<0.05).Histopathology revealed that ZQR and LLF reduced pancreatic damage.Immunohistochemistry evaluation showed that the percentage of insulin positive cells in pancreatic island was higher than model group(P<0.01,0.05,respectively).The mRNA and protein expression of SREBP-1c in pancreas were significantly decreased in ZQR and FLL group(P<0.01).Conclusion ZQR has therapeutic effect on type 2 diabetes,it ameliorates the histopathological changes of pancreas,protectsβcells,improves insulin resistance,and attenuates the expression of SREBP-1c.This study also provides the anti-diabetic evidence of FLL even its effects are weaker than ZQR.