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已被描述为在心肌梗死（Ml）区域干细胞募集中发挥关键作用。缺血组织中CXCL12表达的增加作为一种细胞信号，通过防止细胞凋亡、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，所有这些都导致整体心功能的保存。然而，干细胞分化成新的心肌细胞以提供益处的主要假设在很大程度上尚未得到证实。这导致了对识别心肌干细胞旁分泌机制的兴趣增加。研究表明，CXCL12在各种类型干细胞中的过表达不仅通过血管生成和抗凋亡机制，还通过抑制心肌重塑来增强心肌梗死后的心脏功能。因此，本研究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。本研究拟建立苯肾上腺素（PE）诱导的病理性肥大模型。因此，我们的假设认为CXCL12通过有益的抗重塑机制来预防pe诱导的心肌细胞病理性肥大。1)我们将通过评估蛋白合成、ANF mRNA表达、肌丝组织和细胞大小来确定CXCL12/CXCR4轴是否在体外心肌细胞pe诱导的肥厚反应中起分子决定作用。接下来，我们还将测量CXCL12对舒张期钙积累的影响。2)我们将研究CXCL12调控pe诱导心肌细胞肥厚的机制，重点关注肥厚信号的三个主要调控节点：Calcineurin/NFAT、MAP激酶和GSK3B。3)我们将在体内明确心肌CXCR4的过表达和消融对pe诱导的肥大的生理影响。以腺相关病毒-9 （AAV9）为载体进行CXCR4过表达心肌基因转移。心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：该提案的结果将为心肌重构中CXCR4的新调节机制提供见解。对成人心肌细胞中CXCR4信号传导的进一步研究可能有助于产生和完善基于干细胞的心脏病治疗新方法。

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.