Anti-Remodeling Effects of the CXCL12/CXCR4 Axis in the Cardiac Myocyte

描述(由申请人提供)：趋化因子CXCL12(也称为基质细胞衍生因子-1，SDF-1)及其主要受体CXCR4已被描述为在干细胞向心肌梗死区域(Ml)募集方面发挥关键作用。CXCL12在缺血组织中的表达增加，作为一种细胞信号，通过阻止细胞凋亡、诱导血管生成和抑制纤维化，吸引潜在有益的干细胞修复并可能再生受损的心肌，所有这些都导致了整体心功能的保护。然而，干细胞分化为新的心肌细胞以提供益处的主要假设在很大程度上是未经证实的。这导致了人们对识别心肌干细胞旁分泌机制的兴趣增加。研究表明，在不同类型的干细胞中过表达CXCL12不仅通过血管生成和抗凋亡机制，而且通过抑制心肌重构来增强Mi后的心功能。因此，这项建议的直接目标是研究干细胞分泌因子CXCL12在心肌细胞重塑机制中的作用。这项建议将重点放在苯肾上腺素(PE)诱导的病理性肥大模型上。因此，我们的假设需要CXCL12通过一种有益的、抗重构的机制来预防PE诱导的心肌细胞病理性肥大。1)我们将通过检测蛋白质合成、ANF mRNA表达、肌丝组织和细胞大小来确定CXCL12/CXCR4轴是否是调控PE诱导的体外心肌细胞肥大反应的分子决定因素。接下来，我们还将测量CXCL12对舒张期钙蓄积的影响。2)研究CXCL12调节PE诱导的心肌细胞肥大的机制，重点研究肥大信号的三个主要调控节点：钙调神经磷酸酶/NFAT、MAP激酶和GSK3B。3)我们将在体内确定心脏CXCR4的过度表达和消融在PE诱导的肥厚中的生理后果。腺相关病毒-9(AAV9)将作为载体进行CXCR4过表达的心肌基因转移。心脏功能和结构将通过体内血流动力学、ANF/BNP表达、心脏重量/体重比和组织学来评估。公共卫生相关性：这项提议的结果将为CXCR4对心肌重塑的新的调节机制提供见解。对成人心肌细胞中CXCR4信号的进一步研究可能有助于形成和完善以干细胞为基础的心脏病治疗的新方法。

DESCRIPTION (provided by applicant): The chemokine, CXCL12 (also known as Stromal Cell Derived Factor-1, SDF-1) and its major receptor, CXCR4, have been described to play a critical role in recruitment of stem cells to areas of myocardial infarction (Ml). The increased expression of CXCL12 in ischemic tissue acts as a cellular signal to attract potentially beneficial stem cells to repair, and possibly regenerate, damaged myocardium by preventing apoptosis, inducing angiogenesis and inhibiting fibrosis, all leading to a preservation of global cardiac function. However, the main hypothesis of stem cells differentiating into new cardiac myocytes to provide benefit has been largely unproven. This has led to an increased interest in identifying paracrine mechanisms of stem cells in the myocardium. Studies have demonstrated overexpression of CXCL12 in various types of stem cells enhances cardiac performance post-Mi by not only angiogenic and anti-apoptotic mechanisms, but also through inhibition of myocardial remodeling. Therefore, the immediate goal of this proposal is to investigate the role of the stem cell secretory factor, CXCL12, on remodeling mechanisms in the cardiac myocyte. This proposal will focus on a phenylephrine (PE)-induced pathological hypertrophy model. Hence, our hypothesis entails CXCL12 preventing PE-induced pathological hypertrophy in the cardiac myocyte by a beneficial, anti-remodeling mechanism. 1) We will determine whether the CXCL12/CXCR4 axis is a molecular determinant in modulating PE-induced hypertrophic responses in the cardiac myocyte in vitro by assessing protein synthesis, ANF mRNA expression, myofilament organization and cell size. Next, the effect of CXCL12 on diastolic calcium accumulation will also be measured. 2) We will investigate the mechanism by which CXCL12 regulates PE-induced cardiac myocytehypertrophy, focusing on three major regulatory nodes of hypertrophy signaling: Calcineurin/NFAT, MAP Kinases, and GSK3B. 3) We will define the physiological consequences of the over-expression and ablation of cardiac CXCR4 on PE-induced hypertrophy in vivo. Adeno-associated virus-9 (AAV9) will be used as a vector to perform over-expression myocardial gene transfer of CXCR4. Cardiac function and structure will be assessed by in vivo hemodynamics, ANF/BNP expression, heart weight:body weight ratio, and histology. PUBLIC HEALTH RELEVANCE: The results from this proposal will provide insights into a new modulatory mechanism of CXCR4 upon myocardial remodeling. The further investigation of CXCR4 signaling in the adult cardiac myocyte may help in the generation and refinement of new approaches to stem cell based therapies for cardiac disease.