DNA repair in primordial follicle oocytes following cisplatin treatment

Purpose Genotoxic chemotherapy and radiotherapy can cause DNA double stranded breaks (DSBs) in primordial follicle (PMF) oocytes, which then undergo apoptosis. The development of effective new fertility preservation agents has been hampered, in part, by a limited understanding of DNA repair in PMF oocytes. This study investigated the induction of classical DSB repair pathways in the follicles of wild type (WT) and apoptosis-deficient Puma(-/-) mice in response to DSBs caused by the chemotherapy agent cisplatin. Methods Adult C57BL/6 WT and Puma(-/-) mice were injected i.p. with saline or cisplatin (5 mg/kg); ovaries were harvested at 8 or 24 h. Follicles were counted, and H2A histone family member (gamma H2AX) immunofluorescence used to demonstrate DSBs. DNA repair protein RAD51 homolog 1 (RAD51) and DNA-dependent protein kinase, catalytic subunit (DNA-PKcs) immunofluorescence were used to identify DNA repair pathways utilised. Results Puma(-/-) mice retained 100% of follicles 24 h after cisplatin treatment. Eight hours post-treatment, gamma H2AX immunofluorescence showed DSBs across follicular stages in Puma(-/-) mice; staining returned to control levels in PMFs within 5 days, suggesting repair of PMF oocytes in this window. RAD51 immunofluorescence eight hours post-cisplatin was positive in damaged cell types in both WT and Puma(-/-) mice, demonstrating induction of the homologous recombination pathway. In contrast, DNA-PKcs staining were rarely observed in PMFs, indicating non-homologous end joining plays an insignificant role. Conclusion PMF oocytes are able to conduct high-fidelity repair of DNA damage accumulated during chemotherapy. Therefore, apoptosis inhibition presents a viable strategy for fertility preservation in women undergoing treatment.

Automated summary

The research found that mice lacking the apoptosis gene Puma retained 100% of their follicles 24 hours after chemotherapy treatment and showed efficient repair of DNA damage 8 hours post-treatment. Investigation into DNA repair pathways revealed induction of the homologous recombination pathway in damaged cell types, while non-homologous end joining played an insignificant role in primordial follicle oocytes.