Trpc6 inactivation confers protection in a model of severe nephrosis in rats.

UNLABELLED

Mutations in canonical transient receptor potential-6 (TRPC6) channels give rise to rare familial forms of focal and segmental glomerulosclerosis (FSGS). Here we examined a possible role for TRPC6 in the progression of chronic puromycin aminonucleoside (PAN) nephrosis in Sprague-Dawley rats, a classic model of acquired nephrotic syndromes. We used CRISPR/Cas9 technology to delete a 239-bp region within exon 2 of the Trpc6 gene (Trpc6 allele). Trpc6 rats expressed detectable Trpc6 transcripts missing exon 2, and TRPC6 proteins could be detected by immunoblot of renal cortex. However, the abundance of Trpc6 transcripts and TRPC6 protein in renal cortex was much lower than in Trpc6 littermates, and functional TRPC6 channels could not be detected in whole-cell recordings from glomerular cells cultured from Trpc6 animals, possibly because of disruption of ankyrin repeats 1 and 2. During the chronic phase of PAN nephrosis, Trpc6 rats had reduced urine albumin excretion, reduced serum cholesterol and triglycerides, and improved azotemia compared to wild-type Trpc6 littermates. Glomerulosclerosis was severe during chronic PAN nephrosis in Trpc6 rats but was markedly reduced in Trpc6 littermates. Trpc6 animals also had less severe tubulointerstitial fibrosis as assessed by several biochemical and histological analyses, as well as reduced foot process effacement and glomerular basement thickening compared to Trpc6 controls. None of the manipulations in this study affected the abundance of TRPC5 channels in renal cortex. TRPC3 was increased in PAN nephrosis and in Trpc6 rats. These data support a role for TRPC6 channels in driving an acquired form of secondary FSGS.

KEY MESSAGES

We examined aminonucleoside nephrosis in rats with wild type and inactivated TRPC6. TRPC6 channels were inactivated by CRISPR/Cas9 editing of the Trpc6 gene. TRPC6 inactivation reduced albuminuria in the chronic but not the acute phase. TRPC6 inactivation reduced glomerulosclerosis and ultrastructural changes. TRPC6 inactivation also reduced interstitial changes and renal fibrosis.