Calcification and Vascular Cell Differentiation

描述（由申请人提供）：血管钙化，俗称“动脉硬化”，是普通人群以及高危糖尿病和慢性肾脏疾病患者心血管死亡的主要危险因素和独立预测因子。血管钙化与动脉粥样硬化斑块负荷高度相关，钙化程度预示着不良临床事件和死亡风险的增加。此外，血管钙化与高血压、心脏瓣膜疾病、人工心脏瓣膜钙化和其他形式的动脉硬化有关。它会导致心脏瓣膜狭窄、脉压升高、高血压，并可能导致斑块破裂，所有这些都可能导致心力衰竭。重要的是，目前还没有治疗血管钙化的药物，而通常用于治疗心血管疾病的药物，如他汀类药物，对血管钙化无效。因此，有必要更好地了解参与血管钙化的细胞的起源，以及调节这些细胞的机制，以便制定适当的预防和治疗策略来治疗这种使人衰弱的病理。在过去的资助期内，我们确定了血管平滑肌细胞（SMC）谱系重编程为骨软骨生成前体在血管钙化中的关键作用。在动脉内膜（LDLR-/-和ApoE-/-小鼠）和内侧钙化（MGP-/-小鼠）小鼠模型中使用遗传命运定位策略，发现SMCs是钙化血管中骨软骨生成前体和软骨细胞的主要来源。在内膜和内侧钙化模型中，SMCs向骨软骨形成的谱系重编程之前，都是Runx2（也称为Cbfa1）的重新表达，Runx2是正常骨和软骨发育所需的转录因子。此外，Erk1/2信号是体外SMC骨软骨细胞表型改变所必需的。基于这些数据，我们的总体假设是，SMCs通过激活Erk1/2聚合一种常见的下游介质Runx2（图1），以响应疾病特异性的原钙化信号，进行谱系重编程。Runx2被Erk1/2磷酸化导致骨软骨形成基因表达的开启，而平滑肌基因表达的关闭，从而使平滑肌细胞重编程，走向骨软骨形成的命运。在本研究中，我们将通过确定Runx2/Cbfa1在不同疾病条件下是否为血管钙化所必需，并通过进一步描述Runx2相关SMC谱系重编程和钙化中Erk信号的需求和机制来明确验证这一假设。

DESCRIPTION (provided by applicant): Vascular calcification, commonly known as "hardening of the arteries", is a major risk factor and independent predictor of cardiovascular mortality in the general population as well as high-risk diabetic and chronic kidney disease patients. Vascular calcification is highly correlated with atherosclerotic plaque burden, and the degree of calcification predicts increased risk of adverse clinical events and death. In addition, vascular calcification is associated with hypertension, cardiac valve disease, artificial heart valve calcification, and other forms of arteriosclerosis. It leads to cardiac valve stenosis, increased pulse pressure, hypertension and may contribute to plaque rupture, all of which can lead to heart failure. Importantly, there are currently no drugs to treat vascular calcification, and drugs that are commonly used to treat cardiovascular disease, such as statins, are not effective against vascular calcification. Thus, there is a great need for a better understanding of the origins of cells that participate in vascular calcification, as well as the mechanisms that regulate these cells such that appropriate preventative and therapeutic strategies can be developed to treat this debilitating pathology. In the past funding period, we identified a critical role for vascular smooth muscle cell (SMC) lineage reprogramming to osteochondrogenic precursors in vascular calcification. Using genetic fate mapping strategies in mouse models of arterial intimal (LDLR-/- and ApoE-/- mice) and medial calcification (MGP-/- mice), SMCs were found to be a major source of osteochondrogenic precursors and chondrocytes in the calcified vasculature. In both intimal and medial calcification models, the lineage reprogramming of SMCs towards an osteochondrogenic was preceded by de novo expression of Runx2 (also known as Cbfa1), a transcription factor required for normal bone and cartilage development. Furthermore, Erk1/2 signaling was required for SMC osteochondrocytic phenotype change in vitro. Based on these data, our overall hypothesis is that SMCs undergo lineage reprogramming in response to disease-specific, procalcific cues that convergeon a common downstream mediator, Runx2 (Figure 1) via the activation of Erk1/2. Runx2 phosphorylation by Erk1/2 leads to turn on of osteochondrogenic gene expression, and turn off of smooth muscle gene expression thereby reprogramming the smooth muscle cell towards an osteochondrogenic fate. In this proposal, we will definitively test this hypothesis by determining whether Runx2/Cbfa1 is required for vascular calcification under different disease settings and by further delineating the requirement and mechanisms of Erk signaling in Runx2- associated SMC lineage reprogramming and calcification.