Telomere dysfunction in renal epithelial cells leads to kidney fibrosis

Renal tubular epithelial cells (TECs) are critical mediators of renal fibrogenesis. Telomere dysfunction has been associated with renal injury and fibrosis. However, the role of telomere dysfunction specifically in TECs in the onset and progression of renal fibrosis remains poorly understood. To investigate the impact of telomere dysfunction on renal injury and fibrosis, we generated mice depleted for the shelterin component TRF1 specifically in TECs. Genetic ablation of Trf1 caused decline in renal function, tubular injury and tubulointerstitial fibrosis eight weeks after TRF1 depletion, concomitant with excessive accumulation of extracellular matrix (ECM), cell cycle arrest at G2/M phase, and telomeric damage. Trf1Δ/Δ mice activated regenerative repair mechanism, increasing the risk of of chronic kidney disease (CKD) progression following acute kidney injury (AKI), supporting proliferation-mediated telomere shortening in tubular cells. Mechanistically, Trf1 deletion upregulated Ras–Raf–Mek–Erk, PI3k/Akt/mTOR and p38 pathways. At humane endpoint, Trf1Δ/Δ mice displayed elevated urinary albumin-to-creatinine ratio (uACR), associated with augmented interstitial fibrosis and tubular atrophy eventually leading to CKD. In folic acid (FA)-induced nephropathy, depletion of Trf1 in TECs mitigated the fibrogenic phenotype of CKD. Collectively, our study underlies the important role of TECs in the development and progression of renal fibrosis and CKD associated to dysfunctional telomeres. Tamoxifen (TMX) (Sigma Aldrich, T-5648-1G) was intraperitoneally (i.p.) injected to six-to eight-week-old male and female Trf1+/+ KFP+/t Cre+/t and Trf1lox/lox KFP+/t Cre+/t mice for three times a week for 8 weeks until the sacrifice.