Intrinsic differences in mTOR activity mediates lineage-specific responses to cyclophosphamide in mouse and human granulosa cells.

Background: Cyclophosphamide (CTX) often induces oocyte and granulosa cell injury, leading to fertility loss in young female cancer survivors. Deciphering the mechanisms underlying follicular cell injury could offer novel insights into fertility preservation. Granulosa cells represent the most abundant cell type within the follicles and can be generally categorized as cumulus granulosa cells (CGCs) and mural granulosa cells (MGCs). Despite the essential roles of granulosa cells in supporting ovarian function in physiological conditions, their distinct lineage-specific responses to CTX remains elusive.

Results: Here, we performed a genome-wide transcriptome analysis of murine mural and cumulus granulosa cells before and after CTX administration. Compared with MGCs, CGCs exhibited higher basal mammalian target of rapamycin (mTOR) activity and an increased DNA damage response post-injury. Pharmacological mTOR suppression or RNA interference-mediated gene silencing of Raptor, a key component of the mTORC1 complex, significantly reduced DNA damage in granulosa cells induced by 4-HC, an activated form of CTX. Notably, by examining human granulosa cells in response to 4-HC, our results uncovered a conserved role of mTOR inhibition in ovarian protection.

Conclusions: Taken together, our findings reveal that intrinsic variations in mTOR activity in CGC and MGC lineages determine their differential responses to CTX. Targeting this signaling pathway may prove beneficial in mitigating CTX-induced granulosa cell apoptosis and protecting against ovarian injury.