Objective： The aim of this study was to test the protective effect of mesenchymal stem cells （MSCs） on cardiomyocytes in vitro and to investigate the anti-apoptotic signaling pathway. Methods： MSCs from Sprague-Dawley （SD） rats were separated and cultured. MSC medium was collected from MSCs （DMEM） under hypoxia. Cultured cardiomyocytes from neonatal cultured in serum-free Dulbecco＇s modified eagle medium SD rats were exposed to hypoxia/reoxygenation （H/R） and treated with MSC medium. The apoptotic cardiomyocytes were stained with Annexin-V-fluorescein isothiocyanate （FITC）, Hoechst 33342 and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling （TUNEL）. The mitochondrial transmembrane potential of cardiomyocytes was assessed using a fluorescence microscope. The expression of Bcl-2, Bax, cyto- chrome C, apoptosis-induced factor （AIF）, and caspase-3 was tested by Western blot analysis. Results： Our data demonstrated that MSC medium reduced H/R-induced cardiomyocyte apoptosis, increased the Bcl-2/Bax ratio, and reduced the release of cyto- chrome C and AIF from mitochondria into the cytosol. Conclusion： MSCs protected the cardiomyocytes from H/R-induced apoptosis through a mitochondrial pathway in a paracrine manner.
Background Mesenchymal stem cells are a promising cell type for cell transplantation in myocardial infarction. Type I neuregulins-1, also known as heregulin, can promote the survival of cardiomyocytes and stimulate angiogenesis. The purpose of this study was to investigate the expression of heregulin and ErbB receptors in mesenchymal stem cells, then further detect the secretion of heregulin and the changes in expression of heregulin and ErbB receptors under conditions of serum deprivation and hvooxia. Methods Mesenchymal stem cells isolated from bone marrow of 180 g male Sprague-Dawley rats were cultured. Passage 3 cells were detected experimentally by regular reverse transcriptase-polymerase chain reaction （RT-PCR）, quantitative real time PCR and Western blotting.Results Heregulin and ErbB receptors were expressed in mesenchymal stem cells, and all three ErbB receptors mRNA expressions were significantly down-regulated by serum deprivation and hypoxia, but serum deprivation and hypoxia significantly increased the protein expression of heregulin. Serum deprivation and hypoxia more than 12 hours could induce the secretion of heregulin.Conclusions Mesenchymal stem cells can express all three ErbB receptors and heregulin. Serum deprivation and hypoxia decrease the mRNA expression of ErbB receptors, increase the expression of heregulin, and activate the secretion of heregulin.
GUI Chun WANG Jian-an HE Ai-na CHEN Tie-long LIU Xian-bao LUO Rong-hua JIANG Jun
