Intrafollicular oocyte transfer in the horse: effect of autologous vs. allogeneic transfer and time of administration of ovulatory stimulus before transfer

Abstract

Purpose To assess meiotic and developmental competence after transfer of immature cumulus-oocyte complexes (COCs) to the preovulatory follicles of mares (intrafollicular oocyte transfer (IFOT)). Methods In Experiment 1, mares received an ovulatory stimulus at IFOT. Thirty hours later, COCs were recovered from the follicle, and mature oocytes underwent ICSI and embryo culture. In Experiments 2 and 3, autologous vs. allogeneic COCs were used. The mares were inseminated and embryos were recovered. In Experiment 3, the ovulatory stimulus was administered 9 h (autologous) and 15 h (allogeneic) before IFOT. In Experiment 4, only allogeneic COCs were used; the ovulatory stimulus was administered 9 or 15 h before IFOT. Excess embryos (autologous) and parentage-verified embryos (allogeneic) were considered IFOT-derived. Results In Experiment 1, 36/54 IFOT oocytes (67%) were recovered, of which 56% were mature, vs. 49% of in vitro matured oocytes (P > 0.1). After ICSI, blastocyst rates were 25% and 18%, respectively (P > 0.1). In Experiment 2, 0/6 autologous and 2/6 allogeneic IFOT yielded IFOT-derived embryos. In Experiment 3, 0/7 autologous and 2/5 allogeneic IFOT yielded IFOT-derived embryos. The proportion of mares yielding IFOT-derived embryos was lower after autologous vs. allogeneic IFOT (0/13 vs. 4/11; P < 0.05). In Experiment 4, 1/8 9-h and 1/7 15-h IFOT yielded IFOT-derived embryos. Conclusions Transferred oocytes mature within the follicle and can maintain developmental competence. Allogeneic IFOT was more efficient than was autologous IFOT. The time of ovulatory stimulation did not affect embryo yield. The IFOT procedure is still not repeatable enough to be recommended for clinical use.

Allogenic Follicular Fosterage Technology: Problems, Progress and Potential

“…Therefore, 28 G was considered to be the most suitable needle diameter for maintaining the integrity of sheep COCs and preventing reflux [12]. In the study of Martinez and colleagues on AFF in horses, after using a smaller gauge needle (20 G) for injection compared with using a larger gauge needle, although the incidence of hemorrhagic anovulatory follicles (HAFs) formation did not decrease significantly [11] (11.5% [11] vs. 15.8% [10] vs. 20% [9]), and the proportion of mares providing AFF embryos was not significantly higher, using a smaller gauge needle may help to reduce damage to the follicles, thereby increasing the recovery rate and maturation rate of AFF oocytes and promoting the production of AFF embryos.…”

“…In 13 cases of autologous transfer, no additional embryos were produced, while in 11 cases of AFF, 4 out of 11 cases produced additional embryos that were verified by kinship testing. There was no significant difference in the diameter of autologous and AFF embryos [ 11 ]. Therefore, AFF may be the first choice for future clinical applications.…”

“…Andino and colleagues reported that there was no significant difference in the maturation rate of horse oocytes between AFF technology and in vitro culture systems, with 56% and 49%, respectively. After ICSI, the blastocyst rates were 25% and 18%, respectively [ 11 ].…”

“…When donor female animals have reproductive pathologies and cannot provide embryos, AFF can also provide a new avenue. It is noteworthy that in a study investigating the application of AFF in horses, the ovulation rate and the yield of additional embryos achieved through AFF were significantly greater than those achieved through autologous transfer [ 11 ]. Therefore, AFF may be the first choice for future clinical applications.…”

“…In recent years, AFF technology has successfully demonstrated blastocyst procurement and viable offspring production across multiple animal models [ 11 , 12 , 13 , 14 , 15 ]. Its potential implementation in clinical settings promises to significantly enhance and expand the scope of JIVET technology.…”