| The number of patients suffer from diabetes continue to increase all over the world. And the age is getting younger. Diabetes in all its forms currently afflicts at least 220 million people all over the world. Both type 1 and type 2 diabetes result from an inadequate mass of functioningβcells. Now, the replacement therapies of diabetes include pancreas transplantation and islets transplantation. But shortage of donor and immunological rejection of acceptor are critical problems. Recently, substantial evidence has accumulated demonstrating that islets had the potential of regeneration. Endogenous pancreatic islet regeneration has been providing new therapeutic approaches for diabetes. Our previous study indicated that transplantation of bone marrow promotes islets repair in diabetic mice. The BMSC, with their attributes of high expansion potential and low immune response, may be the current preferred stem cell model for cellular therapeutic development. In the study, firstly, we compared effects of bone marrow mononuclear cells and mesenchymal cells transplantation on improving islets function of diabetic mice and the road of pancreatic islet regeneration. Secondly, we illustrate the distribution and differentiation of BMSC. At last, we investigate the paracrine mechanism of BMSC promoting pancreatic islets of diabetic mice.Objective:To investigate the effect of BMSC promotes pancreatic islets of diabetic mice.Methods:Diabetic mice model were created by multiply peritoneal injection of low-dose STZ and then divided into three groups:control group (n=15), bone marrow mononuclear cells group (n=16) and bone marrow mesenchymal cells group (n=16). Blood glucose was measured weekly after transplantation by glucometer. Histochemistry and immunofluorescent were performed to characterize pancreatic histology, morphology and markers expressed in receipt pancreas in lweek and 6 weeks after transplantation.Results:Compared with other group mice, blood glucose levels of transplanted mice were significantly reduced at one week after transplantation (20.0±7.6mmol/L vs. 26.1±3.1mmol/L/25.2±2.8mmol/L,p<0.01/p<0.05) and sustained to reduce at six weeks after transplantation (16.5±5.7mmol/L vs.27.5±1.1mmol/L, p<0.01; 16.5±5.7mmol/L vs 18.7±5.2mmol/L, p>0.05). One week after transplantation, the islets number of BMSC transplanted mice was larger than control mice (21.6±7.6 vs. 11.3±4.1, P<0.01) and BMMC transplanted mice (21.6±7.6 vs.12.8±5.0, P<0.01). Six weeks after transplantation, the islets number of BMSC transplanted mice was larger than control mice (26.0±9.4 vs.15.4±5.3, P<0.01), but was not larger than BMMC transplanted mice (26.0±9.4 vs.23.7±5.4, P>0.05). One weeks after transplantation, the beta cell number of BMSC transplanted mice was larger than control mice (320.6±67.6 vs.143.9±29.2, P<0.01) and BMMC (320.6±67.6 vs.155.3±98.9, P< 0.01). Six weeks after transplantation, the beta cell number of BMSC transplanted mice was larger than control mice (553.6±242.2 vs.82.1±33.0, P<0.01). Both in BMMC and BMSC transplanted mice, there are several BrdU (+) Insulin (+) cells, PDX-1(+) BrdU (+) Insulin (-), Ngn3 (+) and Insulin (+) Glucagon (+) cells in the islets. In control mice, we found some TUNEL (+) cells in the islets.Conclusions:The effect of BMSC transplantation to improve diabetic islet function is better than BMMC transplantation. BMSC transplantation can initiate pancreatic isletsβcells regeneration, both proliferation ofβcells and differentiation of pancreatic stem cells may contribute to the regeneration ofβcells. BMSC transplantation suppresses apoptosis of islet cells.Objective:To illustrate the distribution and differentiation of BMSC in diabetic mice.Methods:BMSC obtained from GFP transgenic mice were transplanted into diabetic mice. We double stained the sections for GFP and insulin, Nestin, Ngn3, Nkx2.2, Nkx6.1, Pax4, Pax6, NeuroD and PDX-1.Results:Six weeks after transplantation, many donors GFP+cells were detected in the pancreas of diabetic mice. The majority of GFP+cells were in and around islets and ductal regions. Few insulin+GFP+were detected. We double stained the GFP and Nestin, Ngn3, Nkx2.2, Nkx6.1, Pax4, Pax6, NeuroD, PDX-1. No double stained cells were detected.Conclusions:Donor BMSC can engraft into pancreas of diabetic mice. BMSC can't differentiate into pancreatic beta cells in diabetic mice. Objective:To investigate the paracrine mechanisms of BMSC promote pancreatic islets of diabetic mice.Methods:Paracrine experiment:1. Experiment in vivo:diabetic mice divided into three groups:STZ group; BMSC group; BMSC-CM group. Blood glucose was measured weekly after transplantation by glucometer. Histochemistry and immunofluorescent were performed to characterize pancreatic histology, morphology and markers expressed in receipt pancreas in 6 weeks after transplantation.2. Experiment in vitro:STZ injured islets were divided into two groups:STZ group and BMSC-CM group. And morphology of islets and BrdU Expressed in islets were inspected. Mechanism of signal pathway:Experiment in vivo:diabetic mice were divided into two groups:STZ group; BMSC group. Changing of pAkt and pErk expressed in islets were analysis. Experiment in vitro:firstly, STZ injured islets were divided into two groups:STZ group and BMSC group. Changing of pAkt and pErk expressed in islets were analysis. Secondly, changing of express of BrdU was analysis after two pathways were blocked. At last, changing of pAkt expressed in islets were analysis after Akt pathway was blocked.Results:Paracrine experiment:Blood glucose:blood glucose levels of BMSC transplanted mice were significantly reduced at one week after transplantation (20.0±7.6mmol/L vs.26.1±3.1mmol/L, p<0.05) and sustained to reduce at six weeks after transplantation (16.5±5.7mmol/L vs.27.5±1.1mmol/L,p<0.01). Blood glucose levels of BMSC-CM were significantly reduced at one week after transplantation (17.5±4.1 mmol/L vs.26.1±3.1mmol/L, p<0.05) and sustained to reduce at six weeks after transplantation (11.6±4.9mmol/L vs.27.5±1.1mmol/L,p<0.01). Six weeks after transplantation, the islets number of BMSC-CM transplanted mice was larger than control mice (32.3±6.2 vs.15.4±5.3, P<0.01), but was not larger than BMSC transplanted mice (32.3±6.2 vs.26.0±9.4, P>0.05). Six weeks after transplantation, the beta cell number of BMSC-CM transplanted mice was larger than control mice (621.0±106.1vs.82.1±33.0, P<0.01) but was not larger than BMSC transplanted mice (621.0±106.1 vs.553.6±242.2, P>0.05). Mechanism of signal pathway:pAkt and pErk expressed in islets of BMSC-CM were higher than STZ mice both in vivo and in vitro. We could detect BrdU+ cells in STZ, BMSC, PD98059 groups but couldn't detect the cells in LY294002 and LY294002+PD98059 groups. Insulin+BrdU+ cells could also be detected in islets of STZ, BMSC, PD98059 groups. Islets which were added BMSC-CM, the expressing of pAkt was higher. Once blocking Akt pathway by LY294002, the expressing of pAkt was disappear. The expressing of Notch1 was higher in islets which were added BMSC-CM.Conclusions:BMSC repair islets of diabetic mice by paracrine mechanism. BMSC promote islet regeneration through Akt pathway. BMSC may promote pancreatic stem cells differentiation by Notch pathway.Conclusions1. BMSC transplantation can initiate pancreatic isletsβcells regeneration and the effect is better than BMMC transplantation.2. BMSC repair islets of diabetic mice by paracrine mechanism.3. BMSC promote islet regeneration through Akt pathway.4. BMSC may promote pancreatic stem cells differentiation by Notch pathway.
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