Molecular Mechanisms of Zebrafish Heart Regeneration

描述（由申请人提供）：心脏病是美国和世界范围内导致残疾和死亡的主要原因之一。缺血损伤后，人的心脏不能通过瘢痕再生和愈合，逐渐导致心功能障碍。用新的心肌细胞和新生血管取代受损的心肌可以恢复心功能。与哺乳动物相比，斑马鱼的心脏具有显著的再生能力，可以在手术切除后完全再生失去的组织。目前对斑马鱼心脏再生的分子和细胞机制了解甚少。在此过程中，胚胎心外膜和周细胞/间充质标记物上调，表明心外膜被激活并经历上皮-间充质转化（EMT）形成新血管。我们发现血小板衍生生长因子（PDGFs）对心脏再生很重要。阻断PDGF信号导致斑马鱼心脏再生过程中新血管形成受损和心肌细胞DNA合成减少。我们假设PDGF信号是心外膜细胞增殖、心外膜EMT和心肌细胞增殖所必需的。我们拟在体内（目的1）和体外（目的2）研究PDGFR2信号在心外膜细胞增殖、EMT和新血管形成中的功能。我们进一步提出确定PDGFR1信号在斑马鱼心肌细胞和心脏祖细胞中的功能（Aim 3）。我们独特的斑马鱼心脏再生模型和平行的体外和体内方法将使我们能够确定斑马鱼心脏再生的分子和细胞机制。我们的长期目标是在未来为心脏病开发新的治疗方法。

DESCRIPTION (provided by applicant): Heart disease is among the leading causes of disability and mortality in United States and worldwide. After ischemic injury, human hearts cannot regenerate and heal by scarring, which gradually leads to cardiac dysfunction. Replacing the damaged myocardium with new cardiomyocytes and neovascularization may restore cardiac function. By contrast to mammals, zebrafish hearts have remarkable regenerative capacity, completely regenerating lost tissue after surgical resection. Very little is known about the molecular and cellular mechanisms of heart regeneration in zebrafish. During this process, embryonic epicardial and pericyte/mesenchymal markers are upregulated, suggesting that the epicardium is activated and undergoes an epithelial-to-mesenchymal transition (EMT) to form new blood vessels. We found platelet-derived growth factors (PDGFs) are important for heart regeneration. Blocking PDGF signaling caused impaired new blood vessel formation and decreased DNA synthesis in cardiomyocytes during zebrafish heart regeneration. We hypothesize that PDGF signaling is required for epicardial cell proliferation, epicardial EMT, and cardiomyocyte proliferation. We propose to characterize the functions of PDGFR2 signaling in epicardial cell proliferation, EMT, and new blood vessel formation in vivo (Aim 1) and in vitro (Aim 2). We further propose to determine the function of PDGFR1 signaling in zebrafish cardiomyocytes and cardiac progenitors (Aim 3). Our unique zebrafish heart regeneration model and parallel in vitro and in vivo approaches will allow us to determine the molecular and cellular mechanisms of zebrafish heart regeneration. Our long-term goal is the development of novel therapeutic approaches for heart diseases in the future. PUBLIC HEALTH RELEVANCE: Regenerative medicine holds a great deal of promise for treating congenital and degenerative diseases. The goal of this proposal is to determine the molecular and cellular mechanisms of heart regeneration in zebrafish, an organism with a natural regenerative ability. We expect the proposed research can lead to findings that may enhance regenerative capacity in diseased human hearts in the future.