Adult Cardiac Myogenesis--Heart-derived Progenitor Cells

根据成体祖细胞的特性，在成人体内产生新的心肌细胞，既是心脏修复的内在机制，也是通过激活内源性骨髓来源的祖细胞进行治疗干预的机会。在PPG支持的前一个周期中，我们对心脏发育的诱导信号的研究使我们发现了一种新的成年心脏来源的祖细胞，具有以下特性：(1)不表达心脏结构基因。(2)许多心源性转录因子(GATA-4、TEF-1、Tbx5、低水平的MEF2C)表达，但不表达NKX2.5。(3)骨形态发生蛋白I型受体(BMPR1A)ALK3不表达。(4)静脉给药后归巢至梗死心肌，然后原位分化。(5)差异化包括融合独立组件和融合相关组件，并通过CRE/IOX进行了验证 捐赠者/受赠者制度。(6)在5‘-氮杂胞苷诱导BMPR1a的同时，细胞在培养中分化。(7)Cre介导的BMPR1A的切除可阻止MEF2C的上调和αMHC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前体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、荧光和磁分类检索的亚群研究以及克隆分离，更彻底地建立成人心脏前体细胞的表型。2.确定负责的信令 使用显性抑制物、对表达的干扰和候选效应因子Smads和TAK1的条件等位基因，研究依赖于BMPR1A的成人心脏前体细胞分化的途径。3.研究BMPR1A非依赖于成人心脏前体细胞的分化，重点研究NKX2.5诱导的信号和转录机制。4.通过获得和丧失功能的研究，验证成人心脏祖细胞易于转变为心脏表型的假设，这是即使在基线表达的转录因子的结果。

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.