α-Klotho released from HK-2 cells inhibits osteogenic differentiation of renal interstitial fibroblasts by inactivating the Wnt-β-catenin pathway
α-Klotho released from HK-2 cells inhibits osteogenic differentiation of renal interstitial fibroblasts by inactivating the Wnt-β-catenin pathway
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DOI：
10.1007/s00018-021-03972-x
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发表时间：
2021-11-01
影响因子：
8
通讯作者：
Chen，Hequn
中科院分区：
文献类型：
--
作者：
Zhu，Zewu;Ruan，Shuhao;Chen，Hequn
Randall斑块（RP）是特发性草酸钙（CaOx）结石的前体病变，在RP形成中突出了由成骨样细胞驱动的生物矿化过程，但其机制知之甚少。考虑到α-Klotho（KL）（一种在肾脏中高表达的衰老抑制蛋白）在异位钙化中的抑制作用以及KL基因多态性与尿石症易感性之间的密切关系，我们确定了KL在RP形成中的潜在作用。这项研究发现，可溶性KL（s-KL）和跨膜KL（m-KL）下调，和s-KL，而不是m-KL与RP组织中成骨标志物的上调呈负相关。此外，s-KL表达在人肾间质成纤维细胞（hRIF）中被显著抑制，在成骨诱导后在HK-2细胞中被轻微抑制，有趣的是，这与hRIF比HK-2细胞更大的成骨能力相呼应。进一步的研究表明，s-KL在体外和体内对hRIF成骨分化具有抑制作用。此外，与重组人KL（r-KL）或HK-2细胞共培养抑制hRIF的成骨分化，并且与KL沉默的HK-2细胞或β-catenin激动剂SKL 2001共培养消除这种作用。在机制上，s-KL通过直接结合Wnt 2和上调SFRP 1来灭活Wnt-β-连环蛋白途径。进一步的研究确定了RP组织中Wnt-β-catenin通路的激活和SFRP 1和DKK 1的下调。总之，本研究确定s-KL缺乏是RP的病理特征，并揭示HK-2细胞释放的s-KL通过灭活Wnt-β-catenin通路抑制hRIF的成骨分化，不仅深入了解了s-KL在肾间质生物矿化中的作用，还为肾小管上皮细胞与间质细胞的相互作用提供了新的线索，以阐明RP的形成。
Randall’s plaques (RP) are well established as precursor lesions of idiopathic calcium oxalate (CaOx) stones, and the process of biomineralization driven by osteogenic-like cells has been highlighted in RP formation, but the mechanism is poorly understood. Given the inhibitory role of α-Klotho (KL), an aging suppressor protein with high expression in kidneys, in ectopic calcification and the close association betweenKLgene polymorphisms and urolithiasis susceptibility, we determined the potential role of KL in RP formation. This study found that both soluble KL (s-KL) and transmembrane KL (m-KL) were downregulated, and that s-KL but not m-KL was inversely correlated with upregulation of osteogenic markers in RP tissues. Additionally, s-KL expression was markedly suppressed in human renal interstitial fibroblasts (hRIFs) and slightly suppressed in HK-2 cells after osteogenic induction, intriguingly, which was echoed to the greater osteogenic capability of hRIFs than HK-2 cells. Further investigations showed the inhibitory effect of s-KL on hRIF osteogenic differentiation in vitro and in vivo. Moreover, coculture with recombinant human KL (r-KL) or HK-2 cells suppressed osteogenic differentiation of hRIFs, and this effect was abolished by coculture withKL-silenced HK-2 cells or the β-catenin agonist SKL2001. Mechanistically, s-KL inactivated the Wnt–β-catenin pathway by directly binding to Wnt2 and upregulating SFRP1. Further investigations identified activation of the Wnt–β-catenin pathway and downregulation of SFRP1 and DKK1 in RP tissues. In summary, this study identified s-KL deficiency as a pathological feature of RP and revealed that s-KL released from HK-2 cells inhibited osteogenic differentiation of hRIFs by inactivating the Wnt–β-catenin pathway, not only providing in-depth insight into the role of s-KL in renal interstitial biomineralization but also shedding new light on the interaction of renal tubular epithelial cells with interstitial cells to clarify RP formation.