Shear Stress, BMP and Aortic Valve Inflammation

描述（由申请人提供）：炎症和钙化是主动脉瓣（AV）疾病的常见特征，通常需要手术置换瓣膜。虽然病变瓣膜的大体病理改变和手术治疗已受到广泛关注，但AV炎症和钙化的分子机制尚不清楚，AV疾病优先发生在瓣叶的主动脉侧（纤维），该部位暴露于振荡剪切应力（OS）、应变和弯曲等不稳定的血流动力学条件下。相反，小叶的心室侧，暴露在相对稳定的流动条件下，是幸免的。定义潜在的分子机制是这个应用程序的目标。通过最近对暴露于稳定层流剪切（LS）下的猪AV内皮细胞（PAVEC）进行的微阵列研究，我们发现LS显著下调了BMP4的表达，并且纤维内皮细胞表达的BMP4蛋白量明显高于心室侧。有趣的是，我们还发现BMP4在主动脉EC （AEC）中是os诱导的促炎细胞因子。我们假设AVEC暴露于不稳定的血流条件（OS）会刺激BMP4的表达，从而诱导炎症反应。在持续不利的局部血流动力学环境下，募集的炎症细胞会导致瓣膜硬化和瓣膜衰竭。为了验证这些假设，将使用培养的AVEC和三种不同的载脂蛋白e缺陷小鼠系（ApoE和ApoE含有内皮靶向BMP4或BMP受体（alk3）敲除）。AIM 1将决定剪切应力对AVEC中BMP表达和炎症反应的影响。目的2将定义在AVEC中介导剪切非依赖性炎症的BMP信号通路。目的3将确定apoe缺失小鼠的AV炎症和钙化是否可以由BMP4诱导，并通过内皮靶向（包括敲除BMP4或BMP受体（Alk3））来预防。鉴定BMP4作为导致AV炎症和钙化的机械敏感的促炎细胞因子可能为治疗和预防AV疾病提供潜在的非手术治疗途径。

DESCRIPTION (provided by applicant): Inflammation and calcification are common features of the aortic valve (AV) diseases, which typically require surgical replacement of the valves. While gross pathological changes and surgical treatments of the diseased valves have received much attention, the molecular mechanisms underlying AV inflammation and calcification are not well understood AV diseases preferentially occur in the aortic side (fibrosa) of the valvular leaflets, which is exposed to unstable hemodynamic conditions including oscillating shear stress (OS ), strain and bending. In contrast, the ventricular side of the leaflets, is exposed to relatively stable flow conditions, is spared. Defining the underlying molecular mechanisms is the goal of this application. Through a recent micoarray study using porcine AV endothelial cells (PAVEC) exposed to stable laminar shear (LS), we found that BMP4 expression is significantly downregulated by LS, and the fibrosa eridothelium expresses significantly higher amount of BMP4 protein than the ventricular side. Interestingly, we have also shown that BMP4 is a OS-inducible, pro-inflammatory cytokine in aortic EC (AEC). We hypothesize that exposure of AVEC to the unstable flow conditions (OS) stimulates BMP4 expression, which in turn induces inflammatory responses. The recruited inflammatory cells in the face of continued unfavorable local hemodynamic environment would then lead to clacification and valve failure. To test these hypotheses, cultured AVEC and three different Apoliprotein E-deficient mice lines (ApoE and ApoE containing endothelium-targeted BMP4 or the BMP receptor (alk3) knockout) will be used. AIM 1 will determine the effects of shear stress on BMP expression and inflammatory responses in AVEC. Aim 2 will define the BMP signaling pathways mediating shear-independent inflammation in AVEC. Aim 3 will determine whether AV inflammation and calcification in ApoE-null mice can be induced by BMP4 and prevented by endothelium-targeting, include knockout of BMP4 or the BMP receptor (Alk3). Identification of BMP4 as the mechanosensitive, pro-inflammatory cytokine leading to AV inflammation and calcification may provide a potential non-surgical therapeutic avenue to treat and prevent AV diseases.