Time of first polar body extrusion affects the developmental competence of equine oocytes after intracytoplasmic sperm injection

Effect of sperm treatment with lysolecithin on in vitro outcomes of equine intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) in horses is currently employed for clinical and commercial uses, but the protocol could be optimized to improve its efficiency. We have hypothesized that destabilization of plasma and acrosomal membranes prior to injection would positively impact the developmental potential of equine zygotes generated by ICSI. This study evaluated effects of the sperm treatment with lysolecithin on plasma and acrosomal membranes and on oocyte activation ability, initially following heterologous ICSI on bovine oocytes and subsequently employing equine oocytes. The effects of the lysolecithin -treatment on the efficiency of conventional and piezo-assisted equine ICSI were evaluated. To do this, the equine sperm were treated with different concentrations of lysolecithin and the sperm plasma membrane, acrosome and DNA integrity were evaluated by flow cytometry. The results showed that a lysolecithin concentration of 0.08 % destabilized the membranes of all sperm and affected DNA integrity within the range described for the species (8-30 %). In addition, the heterologous ICSI assay showed that lysolecithin treatment was detrimental to the sperm's ability to activate the oocyte, therefore, chemical oocyte activation was used after equine ICSI after injection with lysolecithin -treated sperm. This group showed similar developmental rate to the control group with and without exogenous activation. In conclusion, lysolecithin pre-treatment is not necessary when using ICSI to produce equine embryos in vitro. The results from the current study provide additional insight regarding the factors impacting ICSI in horses.

Past, present and future of ICSI in livestock species

During the past 2 decades, intracytoplasmic sperm injection (ICSI) has become a routine technique for clinical applications in humans. The widespread use among domestic species, however, has been limited to horses. In horses, ICSI is used to reproduce elite individuals and, as well as in humans, to mitigate or even circumvent reproductive barriers. Failures in superovulation and conventional in vitro fertilization (IVF) have been the main reason for the use of this technology in horses. In pigs, ICSI has been successfully used to produce transgenic animals. A series of factors have resulted in implementation of ICSI in pigs: need to use zygotes for numerous technologies, complexity of collecting zygotes surgically, and problems of polyspermy when there is utilization of IVF procedures. Nevertheless, there have been very few additional reports confirming positive results with the use of ICSI in pigs. The ICSI procedure could be important for use in cattle of high genetic value by maximizing semen utilization, as well as for utilization of spermatozoa from prepubertal bulls, by providing the opportunity to shorten the generation interval. When attempting to utilize ICSI in ruminants, there are some biological limitations that need to be overcome if this procedure is going to be efficacious for making genetic improvements in livestock in the future. In this review article, there is an overview and projection of the methodologies and applications that are envisioned for ICSI utilization in these species in the future.

Culture protocols for horse embryos after ICSI: Effect of myo-inositol and time of media change

In vitro production of horse embryos via intracytoplasmic sperm injection (ICSI) is a useful clinical and research technique. Current rates of blastocyst production are typically sub-optimal, and few methods to increase the rate of equine blastocyst development have been reported. Factors that might improve blastocyst production in a horse embryo culture system were explored. Myo-inositol is found in the horse oviduct and improves blastocyst development in other species, thus Experiment 1 was conducted to assess the effect of 10 mM myo-inositol added to Day 0-5 embryo culture medium, using horse oocytes recovered by transvaginal aspiration. Experiment 2 was conducted to investigate effects of exclusion of a standard post-ICSI holding step (culture for 30-60 min in M199-based medium). Experiment 3 was conducted using oocytes recovered from abattoir-derived ovaries, to evaluate effects of earlier transition (Day 4 vs. Day 5) to the second-step medium and of media refreshment at different time points (Day 3 and/or Day 7) during embryo culture. In Experiments 1 and 2, there were no differences (P > 0.05) between groups in blastocyst development (Exp. 1, 36.7 % and 39.2 %; Exp. 2, 41.5 % and 44.6 %). In Experiment 3, blastocyst development was not different (P > 0.05) for embryos refreshed at both Day 3 and 7 (10.8 %) or only at Day 7 (26.6 %), or those transferred to second-step medium on Day 4 or Day 5 (20.6 % and 18.5 %). Knowledge of culture procedures compatible with blastocyst formation in vitro is valuable to laboratories starting to develop procedures for ICSI in horses.