Defective sperm head decondensation undermines the success of ICSI in the bovine

Abstract

The efficiency of intracytoplasmic sperm injection (ICSI) in the bovine is low compared to other species. It is unknown whether defective oocyte activation and/or sperm head decondensation limit the success of this technique in this species. To elucidate where the main obstacle lies, we used homologous and heterologous ICSI and parthenogenetic activation procedures. We also evaluated whether maturation negatively impacted the early stages of activation after ICSI. Here we showed that injected bovine sperm are resistant to nuclear decondensation by bovine oocytes and this is only partly overcome by exogenous activation. Remarkably, when we used heterologous ICSI,-matured mouse eggs were capable of mounting calcium oscillations and displaying normal PN formation following injection of bovine sperm, although -matured mouse oocytes were unable to do so. Together, our data demonstrate that bovine sperm are especially resistant to nuclear decondensation by-matured oocytes and this deficiency cannot be simply overcome by exogenous activation protocols, even by inducing physiological calcium oscillations. Therefore, the inability of a suboptimal ooplasmic environment to induce sperm head decondensation limits the success of ICSI in the bovine. Studies aimed to improve the cytoplasmic milieu of -matured oocytes and to replicate the molecular changes associated with capacitation and acrosome reaction will deepen our understanding of the mechanism of fertilization and improve the success of ICSI in this species.

Transient Sperm Starvation Improves the Outcome of Assisted Reproductive Technologies

“…In contrast, embryo development after ICSI is compromised in bovines, and successful development requires additional treatments with reagents that induce egg activation (Catt and Rhodes, 1995; Malcuit et al, 2006; Salamone et al, 2017). ICSI has also been achieved by pre-treating bovine sperm or eggs with diverse reagents (Rho et al, 1998; Aguila et al, 2017; Canel et al, 2017). At present, it is not clear why bovine sperm do not induce egg activation, but our data suggest that SER treatment of bovine sperm stimulates their ability to activate oocytes.…”

Disruption of O‐GlcNAc homeostasis during mammalian oocyte meiotic maturation impacts fertilization

“…Thus, it is possible that meiotic maturation in the presence of TMG affects glutathione levels in the oocyte, which may have downstream consequences in the zygote on sperm head decondensation. Interestingly, it is well known in the bovine model that a suboptimal ooplasmic environment fails to induce sperm head decondensation following intracytoplasmic sperm injection (Aguila et al, ). Thus, the failure of sperm head decondensation that we observed underscores the poor cytoplasmic environment associated with high O ‐GlcNAc levels.…”

Dysregulated gene expression of imprinted and X-linked genes: a link to poor development of bovine haploid androgenetic embryos

“…The hAE, ICSI and parthenogenetic-derived embryos showed similar rates of anomalies, suggesting that micromanipulation procedures (ICSI/enucleation and chemical oocyte activation) are related to the early development defects. In agreement with these results, numerous studies have associated bovine ICSI with several developmental anomalies such as insufficient sperm head decondensation (Rho et al, 1998; Malcuit et al, 2006), delayed pronuclear formation (Aguila et al, 2017), and altered gene expression (Arias et al, 2015). However, although such ICSI harmful effects certainly can contribute to the early developmental failure of androgenotes, they do not explain the development arrest the occurs beyond ZGA.…”