Critical role of transcription factor SOX4 in tubular epithelial cell dedifferentiation and fibroblast activation during kidney fibrosis.

Chronic kidney disease (CKD) is a widely prevalent health issue globally. A striking pathological feature of CKD is kidney fibrosis characterized by excessive production and deposition of extracellular matrix (ECM). Tubular epithelial cell (TEC) dedifferentiation and fibroblast activation contribute to the pathogenesis of kidney fibrosis. However, the molecular mechanisms underlying TEC dedifferentiation and fibroblast activation are not fully understood. Here, we investigated the role of SRY-box transcription factor 4 (SOX4) in regulating TEC dedifferentiation and fibroblast activation during the development of CKD. We generated global, TEC-specific, and fibroblast-specific SOX4 knockout mice. These mice were subjected to three preclinical models of kidney fibrosis induced by unilateral ureteral obstruction, ischemia-reperfusion injury, or high-dose folic acid to examine the role of SOX4 in TEC dedifferentiation and fibroblast activation during the development of kidney fibrosis. Cultured TECs and fibroblasts were employed to determine the role and molecular mechanisms of SOX4 in regulating TEC dedifferentiation and fibroblast activation in vitro. SOX4 was induced in the injured kidneys but its deficiency inhibits TEC dedifferentiation, fibroblast activation and further impeded the development of kidney fibrosis in mice. In vitro, knockdown of SOX4 preserved the epithelial phenotype and inhibited fibroblast activation induced by transforming growth factor-β1 (TGF-β1). Mechanistically, SOX4 facilitated the TGF-β1-Smad3 signaling pathway to promote TEC dedifferentiation and fibroblast activation. Our findings identify SOX4 as a critical factor in TEC dedifferentiation and fibroblast activation suggesting SOX4 may serve as a potential therapeutic target for the treatment of CKD.