Mitochondrial Quality Control is Essential for Cardiac Progenitor Cell Function

描述(由申请人提供)：心脏前体细胞的激活和参与再生是病理损伤后有效修复的关键。我们发现CPC的激活和谱系承诺涉及到能量需求的增加和线粒体生物发生的激活。虽然线粒体的主要功能是通过氧化磷酸化为细胞提供ATP，但线粒体可以迅速成为促进死亡的细胞器。不足为奇的是，细胞已经形成了一种防御机制，以抵御可能损害细胞的异常线粒体。E3泛素连接酶Parkin标志着功能失调的线粒体通过自噬小体-溶酶体途径降解。不幸的是，衰老与自噬减少有关，自噬导致功能障碍的线粒体去除不足。CPC中线粒体自噬的调节以及线粒体功能与CPC老化之间的相关性基本上是未知的。在这个方案中，我们将探索这样的假设，即CPC中的线粒体质量控制随着年龄的增长而减少，从而导致缺陷线粒体的积累和功能受损。这一假设将通过两个目标进行检验。在目标1中，我们将确定线粒体DNA(MtDNA)突变和衰老对CPC功能的影响。利用携带有校对缺陷线粒体DNA聚合酶γ(POLGm/m)的小鼠模型，我们将研究mtDNA突变积累对线粒体功能以及CPC存活、增殖和分化的影响。我们还将比较WT和POLGm/m细胞在体外和体内的活性和功能，并评估损伤后心功能修复和改善的程度和效率。在目标2中，我们将研究Parkin介导的有丝分裂吞噬在不同年龄的WT和POLGm/m CPC中的功能作用。我们还将在体外和体内探索Parkin缺陷在CPC中的功能后果。这些研究将为通过自噬在CPC中清除线粒体的重要性提供新的见解。我们还将对CPC的基本功能和生存有重要的新理解，最终可用于增强其在受伤心脏中的再生能力。

DESCRIPTION (provided by applicant): Activation and participation of cardiac progenitor cells (CPCs) in regeneration are critical for effective repair in the wake of pathologic injury. We have found that CPC activation and lineage commitment involve increased energy demand and activation of mitochondrial biogenesis. Although the primary function of mitochondria is to provide the cell with ATP through oxidative phosphorylation, mitochondria can quickly become death- promoting organelles. Not surprisingly, cells have developed a defense mechanism against aberrant mitochondria that can harm the cell. The E3 ubiquitin ligase Parkin marks dysfunctional mitochondria for degradation by the autophagosome-lysosomal pathway. Unfortunately, aging is associated with reduced autophagy, which leads to inadequate removal of dysfunctional mitochondria. The regulation of mitochondrial autophagy in CPCs and the correlation between mitochondrial function and CPC aging are essentially unknown. In this proposal, we will explore the hypothesis that mitochondrial quality control in CPCs is reduced with age, which leads to accumulation of defective mitochondria and impaired function. This hypothesis will be tested with two aims. In Aim 1, we will determine the effect of mitochondrial DNA (mtDNA) mutations and aging on CPC function. Using a mouse model carrying a proofreading defective mtDNA polymerase gamma (POLGm/m), we will investigate the effect of accumulating mtDNA mutations on mitochondrial function, as well as survival, proliferation, and differentiation of CPCs. We will also compare viability and function of WT and POLGm/m CPCs in vitro and in vivo, and evaluate the extent and efficiency of repair and improvement in cardiac function after injury. In Aim 2, we will investigate the functional role of Parkin-mediated mitophagy in WT and POLGm/m CPCs at different ages. We will also explore the functional consequences of Parkin-deficiency in CPCs in vitro and in vivo. These studies will provide novel insights into the importance of mitochondrial clearance via autophagy in CPCs. We will also gain important new understanding of basic CPC function and survival, which can ultimately be used to enhance their regenerative capacity in the injured heart.