Androgens Drive SOX9 Upregulation in Injured Proximal Tubular Cells
IntroductionSex 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, supporting survival during injury but also contributing to maladaptive repair. 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. MethodsWe 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. ResultsIn both ischemic and nephrotoxic AKI, SOX9 expression was markedly blunted in females, with levels more than fivefold lower than in males. While injury biomarkers such as NGAL and KIM1 were equally induced in both sexes, Sox9 and its downstream target Vgf showed markedly reduced induction in females, whereas the upstream regulator Zfp24 was functionally relevant 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. ConclusionsThese 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. Translational StatementSex influences susceptibility and outcomes after AKI, but the molecular basis remains unclear. SOX9, a transcription factor recently identified as one of the most highly upregulated genes in proximal tubular cells during AKI in both mice and humans, has been presumed to mediate a universal protective program. Using injury-matched murine models of AKI, we now demonstrate that this response is restricted to males, driven by testosterone and androgen receptor signaling, while SOX9 induction is markedly blunted and functionally dispensable in females. These findings reveal that tubular protective pathways differ fundamentally between sexes despite equivalent injury severity. Because SOX9 activation confers epithelial protection in males, therapeutic targeting of this pathway may have clinical relevance primarily in male patients. These data underscore the importance of incorporating biological sex into mechanistic, translational, and clinical studies of kidney injury and recovery.