Renal interstitial fibrosis (RIF) is the cardinal pathological hallmark of chronic kidney disease (CKD). Although the stem-cell factor (SCF)/c-kit axis has been implicated in kidney fibrogenesis, its cell-specific role and downstream mechanism in tubular epithelial cells (TECs) remain undefined. We investigated whether TEC-derived SCF/c-kit signaling propels RIF after unilateral ureteral obstruction (UUO) via Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells (NF-κB) activation. Using the Cre-loxP system, a renal tubular epithelial cell-specific c-kit gene knockout mouse model (Ggt1-Cre c-kit−/−) was established. Renal interstitial fibrosis was induced in both C57BL/6J (WT) and Ggt1-Cre c-kit−/− mice via UUO surgery. The extent of fibrosis was evaluated by assessing renal function indicators (serum creatinine and blood urea nitrogen), renal histopathology (PAS and Sirius red staining), and the expression of fibrosis markers (α-SMA, Vimentin, and Collagen I). Western blot and immunofluorescence techniques were employed to detect the expression of fibrosis markers, key proteins of the NF-κB pathway (p-p65, p65, p-IκBα, and IκBα), and inflammatory cytokines (Interleukin (IL)-6 and IL-1β). Primary renal tubular epithelial cells were isolated and cultured ex vivo, and treated with SCF and the NF-κB-specific inhibitor SC-75741 to evaluate the degree of cellular fibrosis and the activation status of the NF-κB pathway. Fourteen days after UUO, renal SCF and c-kit expression paralleled the rise in fibrotic markers. TEC‑specific deletion of c‑kit ameliorates the initial decline in renal function, attenuates tubular injury, reduces collagen deposition, and downregulates the expression of fibrotic proteins. Genetic deletion of c-kit significantly inhibits NF-κB phosphorylation and the expression of inflammatory cytokines IL-6 and IL-1β. In vitro, SCF provoked a fibrogenic phenotype in WT TECs that was abolished by either c-kit deletion or SC-75741. The SCF/c-kit signaling pathway in TECs promotes renal interstitial fibrosis in UUO mice via activation of the NF-κB pathway. Targeted inhibition of c-kit in TECs alleviates inflammatory responses and fibrosis, improves renal function, and may offer a novel therapeutic target for delaying the progression of CKD.
Xing et al. (Thu,) studied this question.