Pericytes, mesenchymal stem cells and vascular calcification in chronic kidney disease (CKD). Is hedgehog signaling the missing link between endothelial injury and vascular sclerosis?

心血管疾病占慢性肾脏疾病（CKD）患者死亡总数的一半以上。血管钙化是导致心血管疾病死亡的重要因素。最近的研究表明，细胞周间充质干细胞（MSC）在血管钙化过程中起着重要的作用。目前的研究是基于这样的假设，在CKD中内皮功能障碍/损伤的情况下，改变的内皮-间充质刺猬（Hh）信号导致从血管中激活和募集MSC作为干细胞生态位，通过其旁分泌和生物合成活性来支持再生过程。作为对代谢和炎症应激的反应，它们（通常）分化成成骨细胞。利用遗传学和药理学工具，我们提出了三个具体目标，以确定在血管钙化过程中Hh信号和周包膜间充质干细胞在血管壁中的功能作用：1)我们计划在细胞分辨率上表征在CKD小鼠血管钙化过程中Hh通路配体，Ihh和Shh， Hh受体Ptc-1和Smo以及转录效应物Gli -1 -3的血管表达模式。2)我们将验证细胞周间充质干细胞对损伤诱导的内皮细胞Hh信号的反应，通过分泌旁分泌因子、增殖和向合成前成骨表型分化，导致细胞外基质致密化、硬化和最终钙化。我们将使用遗传谱系追踪和原代周细胞/MSC培养来解决这些问题。3)最后，我们将尝试在体内确定Hh通路的激活或抑制是否会导致CKD小鼠血管硬化和钙化的增加或减少。

Cardiovascular disease accounts for more than half of all deaths in patients with chronic kidney disease (CKD). Vascular calcification is an important contributor to this cardiovascular mortality. Recent studies suggest that pericytal mesenchymal stem cells (MSC) are major players in the vascular calcification process. The current study is based on the hypothesis that, in the case of endothelial dysfunction/damage as in CKD, altered endothelial-mesenchymal hedgehog (Hh) signaling leads to activation and recruitment of MSC from the vascular tube as the stem cell niche to support the regenerative processes by their paracrine and biosynthetic activity. In response to metabolic and inflammatory stress, they (mal)differentiate into osteoblasts. Using genetic and pharmacologic tools, we propose three specific aims to identify the functional roles of Hh signaling and pericytal MSC in the vessel wall during the process of vascular calcification: 1) We plan to characterize at cellular resolution the vascular expression patterns of the Hh pathway ligands, Ihh and Shh, Hh receptors Ptc-1 and Smo and the transcriptional effectors Gli 1-3 during vascular calcification in a mouse model of CKD. 2) We will test the hypothesis that pericytal MSC respond to injury-induced endothelial Hh signals by secreting paracrine factors, proliferation and differentiation towards a prosynthetic osteogenic phenotype leading to extracellular matrix densification, sclerosis and finally calcification. We will use genetic lineage tracing and primary pericyte/MSC culture to address these questions. 3) Finally, we will try to determine in vivo whether Hh pathway activation or inhibition leads to increased or reduced vascular sclerosis and calcification in CKD mice.