Oocyte quality determines bovine embryo development after fertilisation with hydrogen peroxide-stressed spermatozoa

摘要

Exposure of gametes to specific stressors at sublethal levels can enhance the gametes' subsequent performance in processes such as cryopreservation. In the present study, bull spermatozoa were subjected to H2O2 for 4h at 100-, 200- and 500-μM levels; computer-assisted sperm analysis (CASA) and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay were used for evaluation of subsequent sperm motility and DNA integrity, respectively. Exposure of spermatozoa to H 2O 2 did not affect sperm motility but DNA integrity was negatively affected by 500μM H 2O 2 compared with mock-exposed spermatozoa, whereas both motility and DNA integrity were affected compared with untreated spermatozoa. Nevertheless, insemination of oocytes with spermatozoa exposed to 200μM H 2O 2 increased fertilisation, cleavage and blastocyst rates (P0.05). Furthermore, the higher blastocyst yield after fertilisation of oocytes with spermatozoa exposed to 200μM H 2O 2 was related to oocyte diameter, with largemedium oocytes yielding higher blastocyst rates, while small-diameter oocytes consistently failed to develop into blastocysts. In conclusion, the results indicate that exposure of spermatozoa to 200μM H 2O 2 before spermoocyte interaction may enhance in vitro embryo production in cattle. However, this increased embryo production is largely dependent on the intrinsic quality of the oocytes.