Cell cycle activation for cardiac repair

描述（由申请人提供）：尽管成年哺乳动物心肌表现出有限的再生生长能力，但内在更新率不足以逆转病理生理性心肌细胞损失。因此，在受损心脏中重建损失的心脏质量的能力可能具有相当大的治疗价值。实现这一点的一种方法需要在存活的心肌细胞中诱导细胞周期活性。初步数据表明，有针对性地表达细胞周期蛋白D2，一个关键成员的监管复合物，驱动过境通过G1/S细胞周期检查点，是足以诱导心肌细胞的细胞周期活动在成人心脏。此外，细胞周期蛋白D2诱导的细胞周期活性可以逆转心肌损伤后的结构损伤和恢复功能。本实验将进一步阐明细胞周期蛋白D介导的心肌细胞周期调控机制。具体目标1将测试的假设，翻译后修饰的D型细胞周期蛋白调节其能力，介导心肌损伤后的再生生长。这些实验将利用新产生的转基因小鼠，其表达携带相关磷酸模拟和不可磷酸化氨基酸残基取代的D型细胞周期蛋白。目标1中的其他研究将检验以下假设：特异性磷酸化事件介导D型细胞周期蛋白和p193/Cul 7 E3泛素连接酶的相互作用，阻断这种相互作用可增强受损心脏的细胞周期活性。具体目标2中提出的实验将进一步验证细胞周期蛋白D2介导的心肌细胞周期激活可用于促进成人心脏心肌修复的假设。最初的实验将利用条件转基因小鼠模型，以确定细胞周期蛋白D2是否可以诱导新生心肌细胞在成年心脏增殖。其他研究提出，以确定在何种程度上限制不利的损伤后重塑的药物干预能够长期受益，心肌细胞周期诱导的再生。总的来说，这些研究将有助于建立D型细胞周期蛋白调节心肌细胞周期进入的机制，以及细胞周期蛋白D2的靶向表达能够促进心肌再生的程度。总体目标是了解细胞周期调控途径如何被操纵以促进受损心脏的修复。这些分子靶点的鉴定可能最终导致药理学试剂的开发，以促进患病心脏的再生生长。

DESCRIPTION (provided by applicant): Although the adult mammalian myocardium exhibits a limited ability to undergo regenerative growth, the intrinsic renewal rate is insufficient to reverse pathophysiologic cardiomyocyte loss. The ability to reconstitute lost cardiac mass in injured hearts could thus be of considerable therapeutic value. One approach to accomplish this entails inducing cell cycle activity in the surviving cardiomyocytes. Preliminary data indicate that targeted expression of cyclin D2, a key member of the regulatory complex which drives transit through the G1/S cell cycle check-point, is sufficient to induce cardiomyocyte cell cycle activity in adult hearts. Moreover, cyclin D2-induced cell cycle activity can reverse structural damage and restore function following myocardial injury. The experiments proposed in this application will further elucidate the mechanism of cyclin D-mediated cardiomyocyte cell cycle regulation. Specific Aim 1 will test the hypothesis that post-translational modification of the D-type cyclins regulates their ability to mediate regenerative growth following myocardial injury. These experiments will utilize newly generated transgenic mice expressing D-type cyclins carrying the relevant phospho-mimetic and non-phosphorylatable amino acid residue substitutions. Other studies in Aim 1 will test the hypothesis that specific phosphorylation events mediate the interaction of D-type cyclins and the p193/Cul7 E3 ubiquitin ligase, and that blocking this interaction enhances cell cycle activity in injured hearts. Experiments proposed in Specific Aim 2 will further test the hypothesis that cyclin D2-mediated cardiomyocyte cell cycle activation can be used to promote myocardial repair in the adult heart. Initial experiments will utilize a conditional transgenic mouse model to determine if cyclin D2 can induce de novo cardiomyocyte proliferation in adult hearts. Other studies are proposed to determine the degree to which pharmacologic interventions which limit adverse post-injury remodeling are able to benefit long-term, cardiomyocyte cell cycle-induced regeneration. Collectively, these studies will help establish the mechanism by which D-type cyclins regulate cardiomyocyte cell cycle entry, and the degree to which targeted expression of cyclin D2 is able to promote myocardial regeneration. The overall goal is to gain an understanding of how cell cycle regulatory pathways can be manipulation to promote the repair of injured hearts. Identification of such molecular targets may ultimately lead to the development of pharmacologic agents to promote regenerative growth in diseased hearts.