Examination of a new mouse model of mitral valve disease

项目摘要 瓣膜性心脏病（VHD），最常与二尖瓣脱垂（MVP）相关， 严重反流导致心脏骤停或心脏性猝死。二尖瓣内皮细胞 (ECs)是建立二尖瓣结构的关键参与者， 二尖瓣完整性和功能。然而，二尖瓣内皮细胞控制结构的机制， MVP进展期间二尖瓣的变化尚未得到充分表征。很长的- 本提案的长期目标是阐明调节EC功能的基本过程， 二尖瓣的功能，并了解这些机制的破坏如何导致MVP。 FOXC 1和FOXC 2是FOX转录因子家族的密切相关的成员，并且具有许多转录因子。 在心血管发育、健康和疾病中的重要作用。有证据表明人类FOXC 1 突变与二尖瓣异常（包括二尖瓣反流）相关。我们先前已经 显示在小鼠中，Foxc 1和/或Foxc 2的全纯合敲除突变与血管生成相关， 异常;然而，突变也会导致胚胎或围产期死亡，因此试图确定如何 这两个Foxc基因在成年动物中的功能通常是不确定的。为了克服这一局限性，我们 产生了携带他莫昔芬诱导的EC特异性化合物Foxc 1; Foxc 2突变（即，EC- Foxc-DKO小鼠），而母体奖旨在阐明Foxc 1/Foxc 2在血管修复和 直接调控CXCL 12和R-spondin 3旁分泌表达促进肠损伤后再生 肠内皮细胞中的因子。在执行建议的研究过程中，使用 Foxc-DKO小鼠，我们也获得了这些成年突变体的初步研究结果， 表明成年人Foxc 1/c2突变损害心脏二尖瓣的结构和完整性。 因此，我们的中心假设是，二尖瓣内皮细胞中Foxc 1/c2的转录活性有助于二尖瓣内皮细胞的增殖。 阀门的完整性和功能。我们将通过追求两个具体目标来检验我们的中心假设：（1） 确定二尖瓣EC中是否需要Foxc 1和Foxc 2来正常发育二尖瓣 （2）探讨EC表达Foxc 1和Foxc 2调控细胞膜完整性和细胞周期的机制， 二尖瓣的功能。总之，本提案中描述的实验将提供关键的 关于二尖瓣EC人群中Foxc 1/c2缺陷如何导致二尖瓣缺陷的信息， 作为MPV。此外，由于二尖瓣损伤导致各种心脏疾病，我们的研究结果 可能对其他与VHD相关的病理状况如心力衰竭具有重要意义。

Project Summary Valvular heart disease (VHD), which is most commonly associated with mitral valve prolapse (MVP), causes severe regurgitation leading to sudden cardiac arrest or sudden cardiac death. Mitral valve endothelial cells (ECs) are crucial participants in establishing mitral valve structures and are essential for the maintenance of mitral valve integrity and function. However, the mechanisms by which mitral valve ECs govern structural changes in the mitral valve during the progression of MVP have yet to be adequately characterized. The long- term goal of this proposal is to elucidate the fundamental processes that regulate EC function in the integrity and function of the mitral valve and to understand how the disruption of these mechanisms leads to MVP. FOXC1 and FOXC2 are closely related members of the FOX transcription factor family and have numerous essential roles in cardiovascular development, health, and disease. There is some evidence that human FOXC1 mutations are associated with mitral valve abnormalities, including mitral regurgitation. We have previously shown that in mice, global homozygous knockout mutations of Foxc1 and/or Foxc2 are associated with vascular anomalies; however, the mutations also lead to embryonic or perinatal lethality, so attempts to determine how the two Foxc genes function in adult animals have generally been inconclusive. To overcome this limitation, we generated a line of mice carrying tamoxifen-inducible, EC-specific, compound Foxc1;Foxc2 mutations (i.e., EC- Foxc-DKO mice), and the parent award is aimed at elucidating the role of Foxc1/Foxc2 in vascular repair and intestinal regeneration after injury by directly regulating the expression of CXCL12 and R-spondin 3 paracrine factors in intestinal ECs. During the course of performing the proposed studies for the parent award using the Foxc-DKO mice, we also obtained the results from preliminary investigations with these adult mutants, which indicate that the Foxc1/c2 mutations in the adult impair the structure and integrity of the mitral valve of the heart. Thus, our central hypothesis is that the transcriptional activity of Foxc1/c2 in mitral valve ECs contributes to mitral valve integrity and fucntion. We will test our central hypothesis by pursuing the two Specific Aims: (1) To determine whether Foxc1 and Foxc2 are required in mitral valve ECs for proper development of the mitral valve and (2) To determine the mechanisms by which EC expression of Foxc1 and Foxc2 regulates the integrity and function of the mitral valve. In summary, the experiments described in this proposal will provide crucial information about how Foxc1/c2 deficiency in mitral valve EC populations contributes to mitral valve defects such as MPV. Furthermore, since impairments in the mitral valve contribute to various cardiac disorders, our findings may have important implications for other pathologic conditions associated with VHD such as heart failure.