CELLULAR & MOLECULAR PHENOTYPE OF MYOCARDIUM STEM CELLS

这项提议的总体目标是更好地了解哺乳动物细胞的起源、身份和生物学特性，这些细胞在适当的刺激下能够再生成人和衰老心肌。这一目标是基于一个前提，即成人和衰老心肌含有一小群具有心脏干细胞（CSCs）特征和行为的细胞：它们具有克隆性、自我更新性和多能性。从衰老心肌中分离的单个CSC后代可分化为肌细胞、平滑肌细胞和内皮细胞。当在缺血后心肌中注射或激活时，这些细胞重建功能心室壁。它们数量和/或功能的减少可能是老年和衰老心脏性能改变的原因之一。关于csc的起源我们一无所知。来自动物和人类的数据显示，这些细胞在心肌和心肌外组织之间持续运输。骨髓中含有一群具有相似特征的细胞，并且有几种其他心脏外细胞类型已被证明能够分化为心肌细胞。我们将检验CSCs在发育后期出现的假设，通过循环到达心肌，并不断补充，以允许正常和病理心脏的持续周转。一旦我们确定了CSCs的起源并确定了它们的致心潜能，我们就开始对其分化的遗传调控因子进行解剖，首先确定“干细胞标记基因”在致心表型产生中的作用。我们将继续在很大程度上验证CSCs分化的假设

The general goal of this proposal is to gain a better understanding of the origin, identity, and biological properties of mammalian cells that when properly stimulated are capable of regenerating the adult and senescent myocardium. This objective is based on the premise that adult and senescent myocardium contains a small population of cells with the characteristics and behavior of cardiac stem cells (CSCs): they are clonogenic, self-renewing and multipotent. The progeny of a single CSC isolated from an aging myocardium can differentiate into myocytes, smooth muscle and endothelial cells. When injected or activated in a post-ischemic myocardium, these cells reconstitute a functional ventricular wall. A decrease in their number and/or function might be one of the causal factors in the altered performance of the old and senescent heart. Nothing is known about the origin of the CSCs. Data from animals and humans show a continuous trafficking of these cells between myocardium and extra-myocardial tissues. The bone marrow contains a population of cells with similar characteristics and a several other extra-cardiac cell types have been shown able to differentiate into cardiocytes. We will test the hypothesis that CSCs appear late in development, reach the myocardium through the circulation, and are constantly replenished to allow a continuous turnover of the normal and pathological heart. Once we have established the origin of the CSCs and determined their cardiogenic potential, we initiate the dissection of the genetic regulators of their differentiation, starting by identifying the role of "stem cell marker genes" in the production of the cardiogenic phenotype. We will continue by testing the hypothesis that differentiation of CSCs in large measure recapitulates early cardiac ontogeny and requires the down regulation of the canonical Wnt pathway as well as the upregulation of members of the TGFbeta family of regulators, namely certain bone morphogenetic protein (BMPs) genes. Three Specific Aims will be pursued: 1.- To ascertain the origin and relationship among the different adult cells capable of producing the cardiogenic lineages and to compare their myocardial regenerating potential in the post-ischemic heart. 2.- To elucidate the role of "stem cell marker genes" on the myocardial regenerating capability of the CSCs. 3.- To initiate the dissection of the signaling pathways responsible for the maintenance of the differentiated state of the CSCs and their differentiation under normal conditions, in aging and in response to ischemia. The information obtained from these experiments will be used to devise more effective ways of fostering myocardial regeneration through the coaching of the CSCs.