| Rationale:Recent studies have investigated the role of cardiac-resident progenitor cells (CPCs) as the specific regeneratives of the heart, which has opened a new approach for cardiac-repair treatments after myocardial infarction (MI). Stem cell antigen-positive cardiac progenitor cells (Sca-1+CPCs) represent one population of cardiac resident progenitor cells, and transplantation of this group of cells has been proven effective for treating myocardial infarction, mediating cardiac-function improvement and the formation of new cardiomyocytes and endothelial cells. However, this method has limitations resulting from the poor cell viability observed after cell transplantation. Overcoming this limitation is necessary if the potential of CPCs therapy is to be fulfilled. Integrin-linked kinase (ILK) is a59kDa Ser/Thr kinase that is highly expressed in the heart. ILK binds to the cytoplasmic domain of the β1integrin and transduces cell-matrix signals, transferring extra-cellular mechanical stress into intracellular biological signals. ILK has been shown to play a key role in cell growth, proliferation, differentiation and apoptosis. Our previous study found that ILK gene therapy improves cardiac function in rats after myocardial infarction. In this study, we hypothesized that over-expression of ILK in Sca-1+CPCs may improve the transplantation efficiency of Sca-1+CPCs in a mouse model of myocardial infarction. Methods:We isolated Sca-1+CPCs from C57/BL6mice heart. After genetically modified with adenovirus containing GFP/ILK or GFP only, we assessed cell viability, migration ability, DNA synthesis, proliferation rate and cell apoptosis level in vitro. We transplanted GFP-CPCs or ILK-CPCs into the peri-ischemic myocardium of MI mice and measured cardiac function, exercise ability, heart weigh/body weight ratio, infarct size, cardiac fibrosis, capillary density, cardiomyocyte apoptosis as well as ILK related proteins expression four weeks later. We also assessed the maintenance of transplanted cells three days and four weeks after cell transplantation.Results:Over-expression of ILK increased the viability (p<0.001), proliferation rate (p<0.001), DNA synthesis (p<0.001) and migration ability (p<0.001) of CPCs as well as reduced the caspase-3activity (p<0.001) in vitro. Furthermore, expression of phospho-Akt to Akt ratio and Cyclin-D1expression were increased (p<0.001). Transplantation of ILK-CPCs improved cardiac function indicated as higher%FS (p<0.05), lower LVESD (p<0.05) and lower LVEDD (p<0.05). Improved exercise ability (p<0.05) was observed in the ILK-CPCs group. More transplanted cells were found in ILK-CPCs group three days after cell transplantation (p<0.001), but there was no difference between the two groups four weeks later. ILK-CPCs group also showed increased angiogenesis (p<0.001), up-regulation of ILK (p<0.001), Cdc42(p<0.001) and Aurora B (p<0.05), reduced fibrosis (p<0.001) and cell apoptosis in the peri-infarct myocardium (p<0.05).Conclusion:Over expression of ILK increased the viability, proliferation, migration, DNA synthesis and survival of CPCs in vitro. Transplantation of ILK-CPCs after myocardial infarction lead to better cardiac function and exercise performance. This was mainly achieved through reduced interstitial fibrosis, apoptosis and increased angiogenesis. Myocardium regenerative therapy with ILK over-expressed Sca-1+CPCs showed improved therapeutic efficacy. Rationale:Although clinical outcome of acute myocardial infarction (AMI) in patients with type2diabetes mellitus (T2DM) is well established to be worse than for non-diabetic patients, the reasons for this remain unclear. We hypothesized that this may be related to impairment of bone marrow-derived endothelial progenitor cell (EPC) mobilization in such patients. The aim of this study was to investigate this, as well as the underlying mechanism of impaired EPC mobilization in response to cardiac ischemia in T2DM.Methods:We observed the dynamics of bone marrow EPC mobilization in62patients with AMI who did or did not have T2DM, and examined both cardiac function and clinical events at follow-up. In a streptozotocin rat model of diabetes and in corresponding control rats, following induction of AMI we similarly investigated bone marrow EPC mobilization, as well as effects on cardiac structure and function, and we also investigated changes in endothelial nitric oxide synthase (eNOS) signaling and in matrix metalloproteinase (MMP) expression which might underlie the changes in EPC mobilization.Findings:Following AMI, patients with T2DM exhibited both a delay (peak time day 7vs. day5in non-diabetic patients) and a decrease in EPC mobilization (peak level DM vs. NDM:285±56/106mononuclear cells (MNCs) vs.431±88/106mononuclear cells (MNCs), p<0.05), although plasma levels of the ischemia-dependent factors vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α as well as of high sensitivity C-reactive protein were higher in the patients with T2DM. Over a mean of2.25years follow-up, the patients with T2DM exhibited a more pronounced decrease in left ventricular ejection function as well as an increase in clinical events compared to non-diabetic patients. In the rat model of AMI, in those with diabetes we found decreased bone marrow EPC mobilization. We also identified decreased expression of phospho-Akt (p-Akt), phospho-eNOS (p-eNOS) and MMP-9as well as decreased MMP-9activity in the bone marrow of diabetic as compared to the non-diabetic rats, whilst VEGF expression elevated at first and decreased dramatically compared to non-diabetic rats. Four weeks post-AMI, diabetic rats exhibited greater impairment of cardiac function, increased remodeling of the left ventricle (larger area of fibrosis) and decreased angiogenesis compared to non-diabetic rats.Conclusions:Bone marrow EPC mobilization is delayed and reduced in diabetes, and this may relate to impaired p-Akt/p-eNOS/MMP-9signaling. This is likely to contribute to the deterioration in cardiac function and worsened clinical outcome seen in patients with T2DM. |
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