Calcification and Vascular Cell Differentiation

描述(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素。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的风险增加。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，通常用于治疗心血管疾病的药物，如他汀类药物，对血管钙化没有效果。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，以便开发适当的预防和治疗策略来治疗这种衰弱的病理。在过去的资金支持期间，我们确认了血管平滑肌细胞(SMC)向成骨软骨前体细胞重新编程在血管钙化中的关键作用。在小鼠动脉内膜(LDLR-/-和ApoE-/-鼠)和中膜钙化(MGP-/-鼠)模型中使用遗传命运定位策略，发现SMC是钙化血管中骨软骨前体和软骨细胞的主要来源。在内膜和中层钙化模型中，SMC向骨软骨化的谱系重新编程之前是Runx2(也称为Cbfa1)的从头表达，Runx2是正常骨和软骨发育所需的转录因子。此外，ERK1/2信号通路参与了SMC体外骨软骨细胞表型的改变。基于这些数据，我们的总体假设是，SMC经历谱系重编程，以响应疾病特异性的促钙信号，通过激活ERK1/2汇聚常见的下游介质Runx2(图1)。ERK1/2的Runx2磷酸化导致骨软骨基因表达的开启，并关闭平滑肌基因的表达，从而对平滑肌细胞进行重新编程，走向骨软骨的命运。在这个提案中，我们将通过确定在不同疾病背景下血管钙化是否需要Runx2/Cbfa1，以及通过进一步描述Runx2相关的SMC谱系重新编程和钙化中ERK信号的需求和机制来最终检验这一假说。 公共卫生相关性：血管钙化在糖尿病、瓣膜疾病、慢性肾脏疾病患者和老年人中普遍存在，是心血管发病率和死亡率的主要独立预测因子。目前，还没有治疗血管钙化的药物疗法。我们研究的长期目标是了解参与血管钙化的细胞的起源和调节其矿化功能的机制，以便制定适当的预防和治疗策略。

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. PUBLIC HEALTH RELEVANCE: Vascular calcification is prevalent in patients with diabetes, valve disease, chronic kidney disease and in the aged, and is a major independent predictor of cardiovascular morbidity and mortality. Currently, there are no drug therapies for vascular calcification. The longterm goal of our studies is to understand the origins of cells that participate in vascular calcification and the mechanisms regulating their mineralizing functions, such that appropriate preventative and therapeutic strategies can be developed.