Chlorpyrifos exposure remodels the spermatogenic niche and alters testicular epigenetic dynamics in the absence of overt reproductive toxicity.

Chronic exposure to the widely used organophosphate pesticide chlorpyrifos has been associated with reproductive dysfunction; however, the early subclinical events preceding overt reproductive dysfunction remain poorly understood due to cell-specific and non-monotonic responses to the toxicant. The present study investigated the effect of chronic CPF exposure on the spermatogenic niche and sperm epigenome in a mouse model. Despite the absence of detectable oxidative stress or reproductive toxicity, chronic CPF exposure induced significant changes in the testicular microenvironment. Testicular proteomic analysis revealed dysregulated expression of proteins involved in extracellular matrix remodeling in CPF-exposed mice. These changes were associated with increased expression of Ctnnb1 and Axin1 indicating modulation of β-catenin-associated signaling in the testis. Furthermore, CPF exposure was associated with dysregulation of Sertoli cell function characterized by a significant reduction in Kitlg expression, increased c-kit levels, and reduced expression of the gap junction protein Connexin 43. CPF exposure also led to a significant dose-dependent increase in the expression of Tet1 suggesting altered epigenetic regulation in the testis. Interestingly, there was a trend toward increased sperm DNA methylation in CPF-exposed mice. Overall, these findings reveal that chronic CPF exposure induces early remodeling of the spermatogenic niche and alters testicular epigenetic regulation prior to overt reproductive dysfunction, identifying the Sertoli cell-extracellular matrix axis as a potential early target underlying CPF-induced testicular toxicity.