Mutation of Klotho rs3752472 protect the kidney from the renal epithelial cell injury caused by CaOx crystals through the Wnt/β-catenin signaling pathway.

Abstract

Calcium oxalate (CaOx) is a major contributor to urolithiasis, one of the most common urological diseases. Our previous study has shown that Klotho rs3752472 polymorphism correlates with an increased risk of CaOx-related urolithiasis in human cohorts. This study aims to identify the effect of Klotho rs3752472 polymorphism on the renal epithelium injury caused by CaOx. A rat urolithiasis model was established and validated. Renal function was assessed, and histological examination was performed. The distribution and expression of Klotho in the rat model were detected by immunohistochemical staining and western blotting analysis. A renal epithelial cell line (HK2) was used and intervened by COM crystals with several concentrations and time points. Expression of Klotho and key mediators in Wnt/β-catenin pathway were assessed by Western blotting analysis. Wide-type and mutated plasmids of Klotho rs3752472 were added in the cell culture, and the activation of Wnt/β-catenin signaling was tested. Finally, Wide-type and mutated plasmids of Klotho rs3752472 were adoptively transferred to the rat model, and the expression of Klotho was verified. In the rat model, Klotho was mainly distributed in the renal tubular area, which significantly declined in the urolithiasis group. In vitro, COM crystals significantly inhibited the expression of Klotho and induced remarkable renal epithelial cell injury. The mutation of Klotho rs3752472 can notably enhance the expression of Klotho, as well as the protection from renal epithelial cell injury and the inhibition of Wnt/β-catenin signaling pathway. After adoptively transferred to the rat urolithiasis model, similar results were observed for the mutation of Klotho rs3752472. Klotho was significantly correlated with the renal epithelial cell injury induced by CaOx crystals. Furthermore, the mutation of Klotho rs3752472 can remarkably enhance the expression of Klotho in renal tissues and cells, and subsequently protect the renal epithelial cell from the formation of CaOx crystals through the inhibition of Wnt/β-catenin signaling pathway.