Effects of extracellular environments on development and differenciation of cardiac ion channels

本研究旨在探讨心脏前体细胞在胚胎早期的终末分化及出生后离子电流的发育与外源性影响的关系。我们已经建立了小鼠原肠胚中胚层和新生大鼠心室肌细胞的培养体系，我们对早期心脏发生的研究表明，在胚胎发育后7.5天，原肠胚形成完成时，中胚层心脏祖细胞致力于自主分化为收缩性心肌细胞，而胚胎发育后7.25天的中胚层需要额外的终末分化信号。用胰岛素、胰岛素样生长因子和血小板源性生长因子诱导心肌细胞自发搏动，对培养5-15天的乳鼠心室肌细胞进行离子电流分析，发现心肌细胞的离子电流，特别是I_2的发展<to>呈现出不同的模式，并与培养状态有关。低氧培养条件下，I_2发育迟缓或去分化<to>。碱性成纤维细胞生长因子促进I_2的发育<to>。胰岛素样生长因子增加表达I_的细胞百分比<Kur>。为了探讨培养条件引起心肌细胞离子电流发育性变化的分子机制，我们将外源性mRNA注射到培养的心肌细胞中，通过改变培养条件，如缺氧和培养基的改变，调节心肌细胞离子通道的表达。我们的研究结果表明，环境因素在离子通道的发育以及早期心脏发生中起着重要作用。

This study was aimed to investigate terminal differentiaiotn of cardiac progenitor cells in the early embryogenesis, and ionic currents development after birth in relation to exogenous influence. We heve already established culture systems of the mouse gastrula mesoderm and rat neonatal ventricular myocytes.Our study in early cardiogenesis indicates that at 7.5 days post coitum, when gastrulation is completed, mesodermal cardiac progenitor cells commit to autonomous differentiation into contractile cardiomyocytes, while 7.25 day post coitum mesoderm requires additional signaling for terminal differentiation. Insulin, insulin-like growth factor and platelet derived growth factor induced cardiomyocytes with spontaneous beating.In ionic current analysis of neonatal rat ventricular myocytes cultured for 5-15 days, development of ionic currents, especially of I_<to>, showed various patterns, which were dependent on culture states. Hypoxic culture condition retarded or dedifferentiated I_<to> development. Basic fibroblast growth factor enhanced development of I_<to>. Insulin-like growth factor increased the percentage of cells expressing I_<Kur>. In order to explore the molecular mechanism of developmental changes in ionic currents induced by culture condition, we are engaged in microinjection of the exogenous mRNA into cultured cardiomyocytes.The changes of culture condition, such as hypoxia and modification of culture medium, regulated the ion channels expression. Our findings suggest that environmental factors play important role in ionic channels development as well as in the early cardiogenesis.