Klotho protects against mouse renal fibrosis by inhibiting Wnt signaling

Augmented Wnt signaling has been implicated in many fibrotic diseases including obstructive nephropathy. Soluble form Klotho has been reported to function as a secreted Wnt antagonist. In this study, we tested whether Klotho protein could reduce renal fibrosis by inhibition of Wnt signaling. Transgenic mice that overexpressed Klotho, wild-type mice, and Klotho hetero mutant mice underwent unilateral ureteral obstruction (UUO). In some Klotho hetero mutant mice, Klothoencoding plasmid was transferred into the skeletal muscle by electroporation. UUO induced activation of Wnt signaling in wild-type but less in Klotho transgenic mice. Enhanced tubulointerstitial fibrosis in wild-type mice was also attenuated in Klotho transgenic mice. In contrast, Wnt signaling and concomitant tubulointerstitial fibrosis were further augmented in Klotho hetero mutant mice after UUO compared with wild-type mice. In Klotho-encoding plasmid-transfected Klotho hetero mutant mice, however, Wnt signaling was markedly reduced accompanied by a decrease in extracellular matrix deposition after UUO. In vitro studies showed that stimulation of Wnt3a induced prolonged cell cycle arrest at G₂/M phase, with a resultant increase in production of fibrogenic cytokines. Cotreatment with Klotho bypassed the G₂/M arrest and reduced fibrogenic cytokine production. In conclusion, Klotho is a critical negative regulator of Wnt signaling and a suppressor of renal fibrosis in the obstructed kidney model.