Androgens Drive SOX9 Upregulation in Injured Proximal Tubular Cells

Sex influences susceptibility, recovery, and long-term outcomes after acute kidney injury (AKI) in humans. Rodent models have been invaluable for elucidating AKI mechanisms. However, most studies have focused on males, assuming direct applicability to females, an assumption that remains largely untested. In males, the transcription factor SOX9 regulates injury-associated proximal tubule cell states, promoting adaptive repair and survival in the early phase while contributing to fibrosis in later phases. Given the well-described role of SOX9 in sex determination during development and its emerging importance in AKI, we investigated whether it mediates sex-specific tubular responses in the adult kidney.

We first optimized differential ischemic and cisplatin conditions in males and females to generate injury-matched models. We then used these models to ask whether proximal tubular cell responses, particularly Sox9 upregulation, are sex dependent. Tubule-specific knockout models of Sox9, Sox4, Sox11, Vgf, Zfp24, and the androgen receptor (Ar), along with gonadectomy and hormone replacement studies, combined with gene and protein analyses, were used to define regulatory networks.

Under injury-matched conditions, biomarkers such as NGAL and KIM1 were equally induced in the kidneys of both sexes. However, Sox9 and its downstream target Vgf showed markedly blunted induction in females. Consistent with male-specific Sox9 induction, the upstream transcription factor Zfp24 was dephosphorylated and activated only in males. Deletion of Sox9, Zfp24, or Vgf worsened injury in males but not in females. In contrast, Sox4 and Sox11 were equally upregulated and protective in both sexes. Castration or proximal tubule-specific deletion of Ar in males abolished Sox9 induction, establishing a testosterone-dependent regulatory axis.

Our findings define a hormone-driven, male-specific tubular repair program and demonstrate that injury and recovery pathways differ fundamentally between sexes, underscoring the need for sex-inclusive therapeutic strategies for AKI.