Sfrp2 and Cardiac Progenitor Cells in Regenerative Response to Ischemic Injury

描述(申请人提供)：一些研究表明，分泌型FrizzledRelated Protein 2(SFRP2)是一种Wnt途径抑制剂，是心肌创伤修复的关键介质，已被证明可抑制心肌细胞凋亡、诱导血管生成和抑制纤维化。在几个模型系统中，SFRP2是一种分化调节因子，但目前还没有直接研究SFPR2在心肌细胞更新中的意义的研究，以及SFPR2在心肌祖细胞(CPC)激活、增殖和分化中的作用尚不清楚。CPC扩增和分化的调控是心血管生物学和再生医学的一个基本但尚不清楚的方面。我们在体外和体内的初步研究表明，CPC对Wnt/SFRP2信号有反应。我们的数据表明，SFRP2抑制了典型的WNT3a信号转导，并促进了成体c-Kit+/Sca1+CPC的分化。因此，SFRP2在通过潜在的SFPR2/Wnt相互作用调节成人心肌细胞更新中的作用提出了一个有趣的问题。为了解决这一问题，我们假设SFRP2通过调节Wnt规范途径，是心脏祖细胞增殖和谱系指定的关键调节因子。为了验证这一假说，我们将利用培养的CPC，在体外研究SFPR2和WNT3a在CPC增殖和分化中的重要性，并阐明Wnt/b-catenin经典信号通路的作用。在体内，我们将通过检测SFRP2对内源性CPC命运的影响来评估SFRP2在心肌细胞更新中的作用，从而扩展这些研究。我们将使用遗传命运图研究和谱系追踪方法来检测内源性心脏干细胞的增殖和激活，这些细胞向心肌细胞的分化，并确定SFRP2在这些过程中的作用，我们将探讨Wnt/b-catenin规范信号通路在体内介导SFRP2对CPC影响的重要性。在这项研究提案的结论中，我们将表征SFRP2信号在成人心脏干细胞中的作用，为调控这些细胞的途径提供新的见解，并为它们的体外或体内调节治疗目的开辟新的机会。 与公共卫生相关：心力衰竭是世界范围内死亡的主要原因。患者接受对症治疗，未来的生物靶向治疗将取决于发现启动、促进或潜在逆转心肌衰竭发作的新途径。在这项赠款申请中，我们建议描述SFRP2，一种Wnt信号的抑制剂，正如我们的初步结果所表明的那样，它参与了心脏前体细胞的激活和分化。这些研究将为更好地了解心力衰竭的机制开辟新的途径，并可能导致潜在的治疗心肌损伤、肥厚和心力衰竭的药物的开发。

DESCRIPTION (provided by applicant): Several studies have suggested that Secreted Frizzled-related protein 2 (Sfrp2), a Wnt pathway inhibitor, is a key mediator of myocardial wound repair and has been shown to inhibit myocyte apoptosis, induce angiogenesis and inhibit fibrosis. In several model systems, Sfrp2 is a regulator of differentiation yet no studies have been performed that directly address the significance of Sfpr2 in cardiomyocyte renewal and the role of Sfpr2 in cardiac progenitor cell (CPC) activation, proliferation and differentiation remains to be elucidated. The regulation of CPC expansion and differentiation is a fundamental but yet unclear aspect of cardiovascular biology and regenerative medicine. Our preliminary studies, both in vitro and in vivo, suggest CPCs are responsive to Wnt/Sfrp2 signaling. Our data suggest that Sfrp2 inhibits canonical Wnt3a signaling and enhances differentiation in adult c-Kit+/Sca1+ CPCs. Thus, the role of the Sfrp2 in modulation of adult cardiomyocyte renewal by a potential Sfpr2/Wnt interaction poses an intriguing question. To address this, we hypothesize that Sfrp2, by modulating Wnt canonical pathway, is a key regulator of cardiac progenitor proliferation and lineage specification. To test this hypothesis, using cultured CPCs, we will investigate in vitro the importance of Sfpr2 and Wnt3a on CPC proliferation and differentiation, and elucidate the role of the Wnt/b-catenin canonical signaling pathway. In vivo, we will extend these studies by evaluating the role of Sfrp2 on cardiomyocyte renewal by examining its effects on endogenous CPC fate. We will use a genetic fate-mapping study and lineage tracing protocols to examine the proliferation and activation of endogenous cardiac stem cells, the differentiation of these cells to cardiac mocytes and determine the role of Sfrp2 on these processes and we will enquire about the importance of the Wnt/b-catenin canonical signaling pathway in mediating the Sfrp2 effects on CPCs in vivo. At the conclusion of this research proposal we will have characterized the role of Sfrp2 signaling in adult cardiac stem cells providing novel insights about the pathways that regulate these cells and opening new opportunities about their modulation ex vivo or in vivo for therapeutic purposes. PUBLIC HEALTH RELEVANCE: Heart failure is a leading cause of mortality worldwide. Patients receive symptomatic treatment, and future biologically targeted therapy will depend on the discovery of new pathways that initiate, promote or potentially reverse the onset of heart muscle failure. In this grant application we propose to characterize Sfrp2 an inhibitor of Wnt signaling which, as our preliminary results indicate, is involved in activation and differentiation of cardiac progenitor cells. These studies should open new avenues for the better understanding of the mechanisms of heart failure and may lead to the potential development of novel therapeutic drugs for myocardial injury, hypertrophy and heart failure.