Male Pronuclear Formation and Embryo Development Following Intracytoplasmic Injection of Ovine Pretreated Sperm

Background Failure of Male Pronucleus (MPN) formation is a major concern in the success of Intracytoplasmic Sperm Injection (ICSI) in some species. Despite the conducted unsuccessful efforts to improve ICSI efficiency in ovine, the present study was aimed to improve MPN formation and embryo development in ovine ICSI procedure through accompaniment of sperm pretreatment with co-injection of some compounds. Methods In experiment 1, sperm were treated with either 2-mercaptoethanol (2ME), glutathione (GSH), or DTT (dithiothreitol) in combination with Heparin (Hep). Following DNA integrity and fragmentation assessments, the best sperm pretreatment approach in induction of sperm head decondensation was applied for the second and third experiments. In experiment 2, in vitro matured oocytes were subjected to ICSI using pretreated sperm with or without GSH and Sperm Extract (SE) co-injection. In experiment 3, the procedure was followed as experiment 2 with acrosome reacted sperm. Results The highest percentages of oocyte activation were observed in Hep+GSH and Hep+2ME groups. The greatest MPN formations were also observed in the same groups when ICSI procedure was accompanied with GSH co-injection. Despite the higher percentage of MPN formation and oocyte activation in Hep+GSH and Hep+2ME groups, none of the employed strategies could increase the cleavage and blastocyst rates compared to the control. Conclusion In our study condition, despite the lack of significant increase in embryo development in treated groups, the significant increase in MPN formation in Hep+ GSH+co.GSH and Hep+2ME+co.GSH groups indicates the lower chance of parthenote formation that means a higher chance of normal fertilization compared with control.