发育心肌和心肌干细胞分化后心肌特异蛋白表达的比较研究

Comparison in Expression of Specific Myocardiac Proteins in Developing Myocardium and Differentiated Cardiac Stem Cells

为探讨MCSC移植修复缺血性心肌的可能性,观察了大鼠发育心肌和MCSC分化为心肌细胞的cTnT和Cx-43表达特点。结果表明从胚胎发育至成年,心肌cTnT mRNA表达逐渐上调;用BMP-2诱导1周的MCSC可检测到cTnT mRNA表达,3～4周表达显著升高,诱导2周能观察到cTnT蛋白,3～4周可见cTnT呈现横纹样结构。胚胎第11 d心肌可检测到Cx-43 mRNA表达,生后7 d达高峰,以后逐渐降低,17 d趋于稳定。胚胎期Cx-43蛋白多分布于肌膜下,生后10 d位于细胞连接处。诱导的MCSC中Cx-43 mRNA表达特征与cTnT mRNA相似,2周可观察到Cx-43蛋白,3～4周可见Cx-43位于相邻细胞连接处。本研究结果提示,在BMP-2诱导下MCSC可分化为心肌细胞,表现为成熟心肌细胞的结构特征。MCSC有望成为治疗缺血性心脏病的理想种子细胞。

To explore the possibility of transplantation of marrow-derived cardiac stem cells （MCSCs） for repairing the ischemic myocardium, expression features of cardiac troponin T （cTnT） and connexin-43 （Cx-43） in the developing rat myocardium and the cardiomyocytes differentiated from marrow-derived cardiac stem cells （MCSCs） induced by bone morphogenesis protein-2 （BMP-2） were investigated. Expression of cTnT mRNA in the myocardium increased gradually from embryonic rats to adult rats. After induction with BMP-2 for one week, cTnT mRNA of the cells was detected. In week 3 and week 4 after induction, expression of cTnT mRNA of the cells increased significantly. In immunostaining, the cells induced for two weeks expressed cTnT. In week 3 and week 4 after induction, the cells appeared transverse striation-like structures. Cx-43 mRNA was detected in E11 rats. On day 7 after birth, expression of Cx-43 mRNA reached the peak. Then, Cx-43 mRNA expression decreased gradually. In day 17, it trended stable. Cx-43 protein expressed mostly beneath the cell membrane in embryonic period and at cell junctions from day 10 after birth. Changes in expression Cx-43 mRNA were similar with that ofcTnTmRNA expres- sion in the cells induced with BMP-2. Expression of Cx-43 protein was observed in week 2 after induction, Cx-43 protein expressed at cell junctions from week 3 to week 4 after induction. These results demonstrate that MCSCs may differentiate into cardiomyocytes under induction with BMP-2. The structural characteristics of differentiated cells are similar with that of mature cardiomyocytes. Therefore, MCSCs are desirable cells for cell transplantation therapy of ischemic heart diseases.