| Background:With the increase of the incidence of diabetic cardiomyopathy, more and more researchers concerned its mechanism. Excessive proliferation and the phenotypic transformation of the cardiac fibroblasts (CFs), plus the balanceless secretion of ECM (extracellular matrix) are the three major pathological processes which constitute the pathological basis of myocardial interstitial fibrosis induced by high glucose. The phenotypic transformation of the CFs is the central link in the pathophysiological process of myocardial interstitial fibrosis. The expression of a-smooth muscle actin (a-SMA) in the CFs will be activated induced by extracellular stimuli, we put this type of fibroblast cells called myofibroblasts (MFB). MFB is the direct effector cells which can synthetic and secrete the ECM. The ECM is comprised of a variety kinds of collagen and other factors, the changes of the expression of Collage type Ⅰ can can influence myocardial compliance directly. TGF-β super family provides the main signal transduction pathways for the pathophysiological process. As one of transmembrane protein which is an important part of the the receptor type I in the TGF-β super family, ALK7can regulate the gene expression within the cell nucleus precisely through combined with different ligands, and then regulate the phenotypic transformation of the CFS and the expression of ECM. High extracellular glucose levels is an well known inducing factors which can stimulate fibroblast phenotype transformation effectively and the synthesis of ECM. High glucose also can raise the expression of ALK7and its activated ligand in several other organs and cells. The expression of ALK7in cardiac fibroblasts as well as the role in the myocardial interstitial fibrosis induced by high glucose has not yet been studied.Objective:In this study, we investigate the expression characteristics of ALK7and Collage type Ⅰ and the CFs phenotype changes induced by high glucose. Secondly, we suppressed the ALK7by siRNA, and then investigate the role of ALK7in the transformation of cardiac fibroblasts and the production of collagen type I by cardiac fibroblasts induced by high glucose.Methods Neonatal rat cardiac fibroblasts were cultured in vitro with different concentrations of glucose. The mRNA expressions of collagen type I and ALK7were measured by real time-PCR; the protein level of collagen type I was determined by enzyme-linked immunosorbent assay; the protein level of ALK7was measured by western-blotting analysis; the transformation of cardiac fibroblasts was determined by immunofluorescence staining. Thereafter, we investigated the theraputic effects of ALK7siRNA on the above changes induced by high glucose.Results:1. Cultured cells in high glucose medium, cardiac fibroblasts begin to express a-SMA. The transformation of cardiac fibroblasts was increased by high glucose;2. Both mRNA and protein expressions of collagen type1were increased after high glucose stimulation (P<0.05);3. mRNA and protein expressions of ALK7were increased (P<0.05);4. Design the siRNA upon ALK7, and then transfect cells with liposomes. The increased mRNA and protein levels of collagen type I and the transformation of cardiac fibroblasts induced by high glucose were reversed by treatment with ALK.7siRNA (P<0.05), the transformation of cardiac fibroblasts was also reversed.Conclusion:The transformation of CFs to MFB and the synthesis of collagen type1could induced by high glucose definitely.2. ALK.7could be expressed by CFs, and the expression would be upregulated induced by high glucose.3. ALK7involved the transformation of CFs and the synthesis of collagen type I induced by high glucose. It is one of important departments in the signal transduction pathway which regulated the myocardial interstitial fibrosis... |
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