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变化和外科治疗受到了广泛关注，但AV炎症和钙化的分子机制尚未得到很好的理解，AV疾病优先发生在瓣叶的主动脉侧（纤维瘤），其暴露于不稳定的血流动力学条件，包括振荡剪切应力（OS），应变和弯曲。相比之下，暴露于相对稳定的流动条件的瓣叶的心室侧被保留。定义潜在的分子机制是本申请的目标。通过最近的微阵列研究，使用猪AV内皮细胞（PAVEC）暴露于稳定的层流剪切（LS），我们发现，BMP 4的表达显着下调LS，和纤维eridotherapy表达量显着高于心室侧的BMP 4蛋白。有趣的是，我们还发现BMP 4是主动脉EC（AEC）中OS诱导的促炎细胞因子。我们假设AVEC暴露于不稳定流动条件（OS）刺激BMP 4表达，进而诱导炎症反应。在持续不利的局部血流动力学环境下，炎症细胞的募集将导致瓣膜失活和瓣膜衰竭。为了检验这些假设，将使用培养的AVEC和三种不同的载脂蛋白E缺陷小鼠系（ApoE和含有内皮靶向BMP 4或BMP受体（alk3）敲除的ApoE）。目的1：探讨切应力对AVEC中BMP表达和炎症反应的影响.目的二是明确AVEC中BMP信号通路介导的剪切非依赖性炎症反应。目的3将确定ApoE基因敲除小鼠的AV炎症和钙化是否可以由BMP 4诱导并通过内皮靶向（包括敲除BMP 4或BMP受体（Alk3））来预防。将BMP 4鉴定为导致AV炎症和钙化的机械敏感性促炎细胞因子，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.