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

Abstract

Assisted reproduction techniques (ARTs) have become widespread in the equine breeding industry. In particular, the combination of oocyte recovery from live mares followed by IVM and intracytoplasmic sperm injection (ICSI) has increased markedly among the ARTs used with valuable or low-fertility animals. There is currently no consensus among research groups regarding the optimal oocyte maturation period to produce high-quality embryos. In this study, we report the maturation dynamics of equine oocytes at different time points, from 20 to 40h (Experiment 1). In addition, in Experiment 2, equine ICSI blastocysts were produced from oocytes that exhibited early (up to 24h) or late (28–30h) extrusion of the first polar body (PB). Blastocyst rates and diameter were recorded and embryo quality was assessed by analysing the number of apoptotic cells and Yes-associated protein 1 (YAP1) expression. By 20h of IVM, 42% of oocytes were mature, and the remaining oocytes matured within the next 17h of IVM. Although no differences were found in cell apoptosis or the number of YAP1-positive cells between groups exhibiting early and late PB extrusion, embryos from the early group (Group I) exhibited an improved total cell number and blastocyst rate compared to embryos from the late group (Group II) (18.60% vs 10.17% respectively).

Creating Ex Situ Protected Bioreservoirs as a Powerful Strategy for the Reproductive Biotechnology-Mediated Rescue of Threatened Polish Livestock Breeds

“…Furthermore, epigenomic reprogrammability of oocyte-and spermatozoon-inherited chromosomes brings about the pre-and postimplantation developmental competences of IVFor ICSI-derived embryos [111][112][113]. Finally, transcriptomic and proteomic crosstalk between nuclear and mitochondrial DNA fractions [114,115] and the initialization of necrotic, apoptotic or autophagic processes [116][117][118] are undoubtedly significant for successfully promoting the ex vivo-and in vivo-developmental capabilities of IVF-and ICSI-generated embryos in a wide variety of farm animal species and breeds.…”