Oocyte Vitrification Reduces its Capability to Repair Sperm DNA Fragmentation and Impairs Embryonic Development

Oocytes play a crucial role in repairing sperm DNA damage, which can affect the next generation; however, certain factors can impair this ability. This study examined whether oocyte vitrification, a widely used method for fertility preservation, negatively affects repair ability. Male DBA/2 mice ( n = 28) were injected with 101.60 µmol/100 g body weight of tert-Butyl hydroperoxide (tBHP) for 14 days to induce sperm DNA damage. Histological changes, sperm functions, and DNA fragmentation were assessed using the TUNEL assay. Cumulus-oocyte-complexes (COCs) of superovulated female DBA/2 mice ( n = 28) were vitrified using the Cryotop method. Fresh and vitrified oocytes were then fertilized by tBHP-treated and untreated sperms, and subsequent embryonic development was monitored. Additionally, the expression of Mre11a , Rad51 , Brca1 , and Xrcc4 was assessed in resulting zygotes and blastocysts using real-time PCR. The sperm tBHP treatment reduced differentiated spermatogenic cells in the testicular tissue, sperm concentration, and motility, while increasing DNA fragmentation ( P < 0.05). The fertilization rate was decreased in the tBHP-treated sperm–vitrified oocyte group ( P < 0.05), and the two-cell rate diminished in tBHP-treated sperm–fresh and vitrified oocyte groups ( P < 0.05). The four-cell to blastocyst rate decreased in the untreated sperm–vitrified oocyte and the tBHP-treated sperm–fresh and vitrified oocyte groups ( P < 0.05), and the tBHP-treated sperm–vitrified oocyte groups had the lowest blastocyst rate. In zygotes, Brca1 was upregulated in the tBHP-treated sperm–vitrified oocyte group ( P < 0.05). Also, in blastocysts, Rad51 , Brca1 , and Xrcc4 were significantly upregulated in the untreated sperm–vitrified oocytes group ( P < 0.05). Damages to the oocyte due to vitrification can disrupt the repair of sperm DNA fragmentation and consequently impair the embryo development.