Role of the cytoskeleton in cardiac regeneration

描述（由申请人提供）：由于心脏祖细胞和分化的心肌细胞无法有效地重新填充受损心肌，因此认为哺乳动物心脏的损伤是不可逆的。据信，分化的心肌细胞的肌原纤维和细胞骨架组织阻碍了它们进行细胞分裂的能力。这是 最近证明，由神经调节蛋白-1诱导的分化的大鼠心肌细胞在核分裂和胞质分裂期间在中间区分解它们的肌节。类似的过程也发生在成年斑马鱼截肢后的心脏再生过程中。损伤心脏中肌节蛋白和细胞骨架的改变表明成年心肌细胞的去分化需要细胞骨架的短暂重组。然而，在出生后心肌细胞中负责细胞骨架重塑的分子机制仍然知之甚少。在这个探索性的R21应用中，我们将通过诱导小鼠心脏中的细胞骨架调节蛋白--连环蛋白的缺失来直接研究这种机制。我们提供的证据表明，成年心肌细胞重新进入细胞周期，并进行胞质分裂的情况下，<$-连环蛋白。我们假设，连环蛋白的损失导致细胞骨架的变化，允许细胞周期折返和分化的心肌细胞的胞质分裂，从而代表了心脏再生的新机制。提出了以下相互关联的目标：（1）在心脏特异性连环蛋白双敲除（DKO）模型中确定促进心肌细胞再生的信号通路。在体内和体外的方法将被用来检查特定的信号转导途径对心肌细胞增殖的情况下，？-连环蛋白的影响。(2)评估<$-连环蛋白DKO心脏中成体心肌细胞的去分化。将进行细胞谱系追踪以确定在β-连环蛋白DKO心脏中增加的心肌细胞的细胞来源。(3)确定<$-连环蛋白DKO小鼠对心肌梗死的反应。我们将研究与同窝对照相比，在<$-连环蛋白DKO中心肌梗死后发生的细胞、分子和功能后果。我们假设缺失连环蛋白将促进心肌细胞增殖，从而增强受损组织的修复，从而改善损伤后的心脏功能。这项探索性R21提案的长期目标是确定干扰细胞骨架蛋白--连环蛋白是否是一种潜在的治疗方法。 以增强心力衰竭患者的心脏修复。 公共卫生相关性：心血管疾病仍然是西方世界的头号杀手。越来越多的证据表明，激活驻留的心脏祖细胞或局部诱导现有的成年心肌细胞去分化可以改善衰竭的心脏功能。然而，调节心肌细胞存活和增殖的机制仍然知之甚少。我们建议使用一种新的动物模型来研究细胞骨架重构对心肌细胞增殖的影响。

DESCRIPTION (provided by applicant): Damage to the mammalian heart is considered irreversible due to the inability of cardiac progenitor cells and differentiated cardiomyocytes to effectively repopulate the injured myocardium. It is believed that myofibril and cytoskeleton organization of differentiated cardiomyocytes hinder their ability to undergo cell division. It was recently demonstrated that differentiated rat cardiomyocytes induced by neuregulin-1 disassemble their sarcomeres in the midzone during karyokinesis and cytokinesis. A similar process has been shown to occur in adult zebrafish during heart regeneration after amputation. Alterations in sarcomeric proteins and cytoskeleton in injured heart suggest dedifferentiation of adult cardiomyocytes requires a transient reorganization of the cytoskeleton. However, the molecular mechanism(s) responsible for cytoskeleton remodeling in postnatal cardiomyocytes remain poorly understood. In this exploratory R21 application, we will directly investigate this mechanism by inducing deletion of the cytoskeletal regulator proteins, ¿-catenins in the mouse heart. We provide evidence that adult cardiomyocytes reenter the cell cycle and undergo cytokinesis in the absence of ¿-catenins. We hypothesize that loss of ¿-catenins leads to cytoskeletal changes permissive for cell cycle reentry and cytokinesis of differentiated cardiomyocytes, thus representing a novel mechanism for cardiac regeneration. The following interrelated aims are proposed: (1) To define signal pathways that promote cardiomyocyte regeneration in a cardiac specific ¿-catenin double knockout (DKO) model. In vivo and in vitro approaches will be used to examine the effects of specific signaling pathways on cardiomyocyte proliferation in the absence of ¿-catenins. (2) To assess the de-differentiation of adult cardiomyocytes in the ¿-catenin DKO heart. Cell lineage tracing will be performed to determine the cellular source of the increased cardiomyocytes in the ¿-catenin DKO heart. (3) To determine the response of ¿-catenin DKO mice to myocardial infarction. We will examine the cellular, molecular, and functional consequences that occur after myocardial infarction in the ¿-catenin DKO compared with their littermate controls. We hypothesize that deletion of ¿-catenins will promote cardiomyocyte proliferation leading to enhanced repair of damaged tissue, thus improving cardiac function after injury. The long term goal of this exploratory R21 proposal is to determine if interfering with the cytoskeletal proteins, ¿-catenins, represents a potential therapy to enhance cardiac repair in heart failure patients. PUBLIC HEALTH RELEVANCE: Cardiovascular disease remains the number one killer in the Western world. Accumulating evidence suggests that activation of the resident cardiac progenitor cells or local induced de-differentiation of existing adult cardiomyocytes can improve function of a failing heart. However, the mechanisms that regulate cardiomyocyte survival and proliferation remain poorly understood. We propose to investigate the effects of cytoskeleton remodeling on cardiomyocyte proliferation using a novel animal model.