Mechanisms of Notch1 in Aortic Valve Calcification

描述（由申请人提供）： 主动脉瓣钙化/狭窄是成人心脏病的第三大原因，也是发达国家获得性瓣膜病的最常见形式。与钙化性主动脉瓣狭窄最密切相关的风险因素是存在二叶主动脉瓣、年龄增加、男性、吸烟、高血压和脂蛋白升高。对人类钙化主动脉瓣组织的检查表明，涉及到几种病理途径。然而，涉及瓣膜钙化的分子机制尚未阐明。最近，Srivastava实验室报道了两个人类家族，其中NOTCH 1突变与主动脉瓣和二叶式主动脉瓣的早期钙化有关。Notchl是参与许多细胞事件（包括细胞命运决定和细胞分化）的高度保守的信号传导途径的一部分。这项研究表明，Hrt 2，一个转录抑制因子，介导的Notchl信号，可以调节Runx 2的活性，成骨细胞的命运决定在体外的中央调节器。我们的初步数据显示，Notchl杂合子小鼠与野生型年龄匹配的同窝出生小鼠相比，主动脉瓣钙化增加。我假设Notchl信号传导抑制主动脉瓣间充质中的促成骨途径，并且Notchl破坏可能使瓣膜对促进钙化的已知风险因素敏感。具体目的1：确定破坏Notchl信号传导是否通过激活小鼠中的成骨途径导致主动脉瓣钙化。Notchl信号传导将在出生前或出生后在主动脉瓣组织瓣膜中被有条件地破坏。将检查主动脉瓣的功能性狭窄、钙化和骨形成相关基因的表达。此外，Notchl缺陷小鼠将与高脂血症小鼠模型杂交，以检查该风险因素对Notchl介导的主动脉瓣钙化的贡献。具体目标2：阐明Notchl在间充质和内皮细胞中介导的钙化途径。在各种条件下，Notchl表达将在培养的间充质和内皮细胞中被破坏或增强。将检查间充质细胞的成骨细胞特异性基因表达的激活或抑制，以及在某些情况下的钙沉积。将检查Notchl信号传导与先前在心血管钙化中涉及的三种分子途径（即Runx 2、Bmp 2和Wnt）之间的相互作用。 (End摘要）

DESCRIPTION (provided by applicant): Aortic valve calcification/stenosis is the third leading cause of adult heart disease and the most common form of acquired valvular disease in developed countries. The risk factors most closely linked to calcific aortic stenosis are the presence of a bicuspid aortic valve, increased age, male gender, smoking, hypertension, and elevated lipoproteins. Examination of human calcified aortic valve tissue has shown that several pathologic pathways are involved. However, the molecular mechanisms involved in valvular calcification have not been elucidated. Recently, the Srivastava lab reported two human families in which mutations in NOTCH1 were associated with early calcification of the aortic valve and bicuspid aortic valves. Notchl is a part of a highly conserved signaling pathway involved in many cellular events, including cell fate decisions and cell differentiation. This study demonstrated that Hrt2, a transcriptional represser that mediates the Notchl signal, could regulate the activity of Runx2, a central regulator of osteoblast cell fate determination in vitro. Our preliminary data show that Notchl heterozygous mice develop increased aortic valve calcification as compared to wild-type age matched littermates. I hypothesize that Notchl signaling represses pro-osteogenic pathways in aortic valve mesenchyme and that Notchl disruption may sensitize the valve to known risk factors that promote calcification. Specific Aim 1: To determine if disrupting Notchl signaling causes calcification of the aortic valve by activation of osteogenic pathways in mice. Notchl signaling will be conditionally disrupted in aortic valve tissue valves prenatally or postnatally. The aortic valves will be examined for functional stenosis, calcification, and expression of genes involved in bone formation. In addition, Notchl-deficient mice will be crossed with a mouse model of hyperlipidemia to examine the contribution of this risk factor to Notchl-mediated aortic valve calcification. Specific Aim 2: To elucidate the calcific pathways mediated by Notchl in mesenchymal and endocardial cells. Notchl expression will be disrupted or enhanced in cultured mesenchymal and endocardial cells under various conditions. Mesenchymal cells will be examined for activation or repression of osteoblast-specific gene expression and in some cases deposition of calcium. The interactions between Notchl signaling and three molecular pathways previously implicated in cardiovascular calcification, namely Runx2, Bmp2, and Wnt, will be examined. (End of Abstract)