Molecular mechanism of vascular calcification in chronic kidney disease

背景：血管钙化在糖尿病和慢性肾病患者中很普遍。晚期糖基化终产物受体（RAGE）及其多种配体与动脉粥样硬化加速的发病机制有关。方法与结果：用表达RAGE的腺病毒转染培养的大鼠和人主动脉平滑肌细胞（HASMC）。心肌素和smc标记基因的表达在这些细胞中被显著抑制。有趣的是，RAGE激活诱导了HASMC中碱性磷酸酶（ALP）的表达、钙沉积和Msx2的表达，Msx2是成骨分化的关键转录因子。内源性RAGE可显著抑制RAGE诱导的成骨分化。rage诱导的ALP和Msx2表达被Notch信号通路抑制剂DAPT完全消除。骨形态发生蛋白2 （bone morphogenetic protein 2, BMP2）和RAGE信号同时刺激可协同诱导HASMC中Msx2和ALP的表达。免疫组化结果显示，人动脉粥样硬化钙化斑块表达RAGE、Notch组分和Msx2。人血清诱导rage -过表达的HASMCs的ALP活性与血清肌酐水平呈正相关，而与磷酸和血红蛋白A1c水平无关。结论-这些结果表明，RAGE的激活不仅抑制了心肌素依赖性SMC基因的表达，而且通过Notch/Msx2诱导血管SMC的成骨分化。这些结果为RAGE轴在血管钙化中的作用提供了新的见解。

Background-Vascular calcification is prevalent in patients with diabetes and chronic kidney disease. Receptor for advanced glycation end products (RAGE) and its multiple ligands have been implicated in the pathogenesis of accelerated atherosclerosis.Methods and Results-Cultured rat and human aortic smooth muscle cells (HASMC) were transduced with adenovirus expressing RAGE. Expression of myocardin and the SMC-marker genes was significantly repressed in these cells. Interestingly, RAGE activation induced alkaline phosphatase (ALP) expression, calcium deposition, and Msx2 expression, a crucial transcription factor for osteogenic differentiation, in HASMC. RAGE-induced osteogenic differentiation was significantly inhibited by endogenous secretory RAGE. RAGE-induced ALP and Msx2 expression was completely abrogated by DAPT, an inhibitor for Notch signaling pathway. Simultaneous stimulation with bone morphogenetic protein 2 (BMP2) and RAGE signaling synergistically induced expression of Msx2 and ALP in HASMC. Immunohistochemistry revealed that the human calcifying atherosclerotic plaque expressed RAGE, Notch components and Msx2. The ALP activity induced in RAGE-overexpressing HASMCs by human serum was positively correlated with serum creatinine level, but not with phosphate and hemoglobin A1c levels.Conclusions-These results indicate that activation of RAGE not only inhibits myocardin-dependent SMC gene expression, but also induces osteogenic differentiation of vascular SMC through Notch/Msx2 induction. These results provide the novel insight into a role of RAGE axis in vascular calcification.