Sperm capacitation pretreatment positively impacts bovine intracytoplasmic sperm injection

The efficiency of intracytoplasmic sperm injection (ICSI) in bovines is low compared to other species due in part to inadequate egg activation and sperm nucleus decondensation after injection. We hypothesized that this low efficiency is due to the lack of complete sperm capacitation, so we evaluated the effects of isobutylmethylxanthine (IBMX) and methyl-beta-cyclodextrin (M beta CD) on bovine sperm capacitation and on the preimplantation developmental potential of bovine embryos generated by ICSI. Treatment with IBMX and M beta CD decreased sperm viability (between 13-30%); nevertheless, 0.4 mM IBMX and 1 mM M beta CD increased (p < 0.05) capacitation metrics-that is, acrosome exocytosis, intracellular calcium level, plasma membrane fluidity, and tyrosine phosphorylation-compared to the control. After ICSI, embryos injected with IBMX- and M beta CD-treated sperm showed similar cleavage to the untreated group (range 82-88%). Pronucleus formation rate was higher with M beta CD-pretreatment (54%) compared to the control group (25%), and blastocyst rate was significantly improved with M beta CD-pretreatment (24%) compared to the IBMX (18%) and control (17%) groups. Importantly, embryo quality-as assessed by the total number of cells, cell allocation, and apoptotic cell index-was not affected by the sperm treatments. In conclusion, M beta CD pretreatment of sperm improved the efficiency of blastocyst production in bovine ICSI.