Adult Cardiac Myogenesis--Heart-derived Progenitor Cells

通过成体祖细胞的特化在成人中产生新的心肌细胞被报道为心脏修复的内在机制和通过内源性骨髓源性祖细胞的活化作为治疗干预的机会。在PPG支持的前一个周期中，我们对心脏发育诱导信号的研究使我们发现了一种新的成人心脏源性祖细胞，具有以下特性：（1）不表达心脏结构基因。(2)表达许多心源性转录因子（加塔-4、TEF-1、Tbx 5、低水平MEF 2C），但不表达Nkx 2.5。(3)不表达ALK 3，骨形态发生蛋白（Bmpr 1a）的IA型受体。(4)静脉注射时归巢至梗死心肌，随后原位分化。(5)差异化包括融合独立和融合相关组件，已通过Cre/Iox验证 捐助者/接受者系统。(6)细胞在5 '-氮杂胞苷后在培养物中分化，同时诱导Bmpr 1a。(7)Cre介导的Bmpr 1a切除阻止了MEF 2c的上调和α MHC的诱导。基于这些发现，我们建议通过这种新的心脏来源的心脏祖细胞群来研究成人心肌发生的基本机制：1。通过候选基因方法、表达谱分析、荧光和磁性分选获得的亚群研究以及克隆分离，更彻底地建立成体心脏祖细胞的表型。2.识别负责的信号 成人心脏祖细胞的Bmpr 1a依赖性分化途径，使用显性抑制剂，干扰表达，以及Smads和TAK 1的条件等位基因，候选效应子。3.研究Bmpr 1a非依赖性的成体心脏祖细胞分化，重点是Nkx2.5诱导的信号传导和转录机制。4.通过功能获得和功能丧失研究，验证成年心脏祖细胞倾向于转化为心脏表型的假设，这是由于即使在基线时也表达转录因子。

The creation of new cardiac myocytes in adults, by the specification of adult progenitor cells, is reported both as an intrinsic mechanism of cardiac repair and as an opportunity for therapeutic intervention, by the activation of endogenous marrow-derived progenitor cells. During the previous cycle of PPG support, our investigations of inductive signals for cardiac development led us to discover a novel, adult, heart-derived progenitor cell with the following properties: (1) No cardiac structural genes are expressed. (2) Many cardiogenic transcription factors are expressed (GATA-4, TEF-1, Tbx5, low levels of MEF2C), although not Nkx2.5. (3) No expression of ALK3, the type IA receptor for bone morphogenetic proteins (Bmpr1a). (4) Homing to infarcted myocardium when given intravenously, followed by differentiation in situ. (5) Differentiation includes both fusion-independent and fusion-associated components, proven with a Cre/Iox donor/recipient system. (6) The cells differentiate in culture after 5'-azacytidine, concurrent with induction of Bmpr1a. (7) Cre-mediated excision of Bmpr1a prevents up-regulation of MEF2c and the induction of alphaMHC. Based on these findings, we propose to study fundamental mechanisms for adult cardiac myogenesis by this novel, heart-derived cardiac progenitor cell population: 1. To establish, more thoroughly, the phenotype of adult cardiac progenitor cells, by a candidate gene approach, expression profiling, studies of sub-populations retrieved by fluorescence and magnetic sorting, and clonal isolation. 2. To identify the responsible signaling pathway for Bmpr1a-dependent differentiation of adult cardiac progenitor cells, using dominant-inhibitors, interference with expression, and conditional alleles for Smads and TAK1, the candidate effectors. 3. To investigate the Bmpr1a-independent differentiation of adult cardiac progenitor cells, with emphasis on the signaling and transcriptional mechanisms for induction of Nkx2.5. 4. To test the hypothesis that adult cardiac progenitor cells are predisposed to convert to the cardiac phenotype, as a consequence of the transcription factors expressed even at baseline, by gain- and loss-of-function studies.