肾小管上皮细胞SOCE相关信号STIM1与Orai1活化在草酸钙结石形成机制中的作用

Randall’s Plaque (RP) theory, one of the classical theories explaining the pathogenesis of nephrolithiasis, suggests that the renal interstitial ectopic calcification may serve as the initial nidi for renal stones. Our previous research found that the transdifferentiation of tubular epithelial cells to osteoblast-like cells which was probably mediated by the TGF-β induced EMT and abnormal intracellular Ca2+ signaling pathway activation which was involved in the formation and of RP. We have found that SOCE related proteins STIM1 and Orai1 was highly expressed in the renal tissue of genetic hypercalciuria stone-forming rats which are susceptible to nephrolithiasis. Moreover, the expression of active STIM1 and Orai1 were critical stimulus in intracellular Ca2+ regulations. And base on the above we can make this speculation reasonably: the dysfunction of SOCE which can be caused by many different reasons results in abnormal STIM1 and orai1 activation and tubular cells transdifferentiation, and subsequently leads to the RP and stones formation. This research program tries to clarify the roles of SOCE related STIM1 and Orai1 proteins in tubular cells transdifferentiation, RP and renal stone formation and their mechanisms by investigating the gene posttranslational modification of STIM1 and Orai1, the effect of MGP on tubular cells biological functions related to stone formation, the regulation of BMP2 by MGP, and whether calcification and nephrolithiasis can be prevented by regulating the function of STIM1 and Orai1 in three aspects including cell, animal and human. We hope this research could provide new theoretical and experimental basis for the prevention and control of nephrolithiasis.

Randall钙斑理论是阐释肾结石形成的经典理论之一，该理论认为肾间质异位钙化斑是肾结石形成的起始病变。前期研究发现，TGF-β1诱导的EMT过程与Ca2+可协同促进肾小管上皮细胞向成（软）骨样细胞转分化，该过程参与钙斑形成。近来研究提示，与SOCE通路关系密切的基质细胞内STIM1和Orai1参与细胞内Ca2+调控以及相关Ca2+信号通路。我们在具有成石倾向的遗传性高钙尿大鼠肾小管上皮发现STIM1和Orai1表达升高，而STIM1和Orai1是目前发现参与细胞外Ca2内流及内质网Ca2+释放调控细胞内Ca2+重要信号分子，我们推测：STIM1及Orai1异常激活与TGF-β1诱导的EMT病理过程可共同促进肾小管上皮细胞表型转化为成骨软骨细胞分化，最终导致钙斑和结石形成。课题拟在细胞、动物和人体层面，对SOCE相关蛋白STIM1和Orai1的调控对钙斑和结石的预防等方面，探究肾结石成因。

Randall钙斑是肾间质的异位钙化，钙斑学说认为其为肾结石形成的起始病变。近来研究提示，与SOCE通路关系密切的基质细胞内STIM1和Orai1参与细胞内Ca2+调控以及相关Ca2+信号通路，而肾乳头的高钙微环境被人们认为是肾结石的起始因素，随后我们在具有成石倾向的遗传性高钙尿大鼠肾小管上皮细胞发现STIM1和Orai1异常表达，因此我们在研究中探究了STIM1和Orai1在结石形成中的作用。.我们在实验探究中发现高钙模拟成石环境下，肾小管上皮细胞发生表型转化，同时细胞表面钙盐粘附增多，结合钙斑学说，表型的转化标示着结石形成的起源，同时我们在实验中发现STIM1基因的表达显著降低。随后我们上调/下调了STIM1基因的表达，发现肾小管上皮细胞也随之发生了表型转化；当STIM1基因下调时，肾小管上皮细胞成（软）骨表型标志物OPN表达显著增加，上皮表型标志物E-cadherin表达显著减少；当上调时表型标志物变化刚好相反。我们的实验验证了STIM1基因在细胞表型转化及结石起源中起到信号转导的作用。