Effects of Fetuin on Zona Pellucida Hardening and Fertilizability of Equine Oocytes Matured In Vitro1

Abstract

In vitro fertilization (IVF) has had poor success in the horse, a situation related to low rates of sperm penetration through the zona pellucida (ZP). Zona pellucida hardening (ZPH) is seen in mouse and rat oocytes cultured in serum-free medium. The hardened ZP is refractory to sperm penetration. Fetuin, a component of fetal calf serum, inhibits ZPH and allows normal fertilization rates in oocytes cultured in the absence of serum. We evaluated whether fetuin is present in horse serum and follicular fluid (FF) and whether fetuin could inhibit ZPH in equine oocytes matured in vitro, thus increasing sperm penetration during IVF. The presence of fetuin in equine serum and FF was confirmed by immunoblotting. Oocytes submitted to in vitro maturation (IVM) in medium containing fetuin were used for ZPH assay or IVF. Intracytoplasmic sperm injection (ICSI) was carried out as a control procedure. The presence of fetuin during IVM did not affect the rate of maturation to metaphase II. Maturation of oocytes in the presence of fetuin reduced ZPH in a dose-dependent manner. After both IVF and ICSI, there was no significant difference in oocyte fertilization between fetuin-treated and untreated oocytes. The fertilization rate was significantly higher after ICSI than after IVF, both in fetuin-treated and in untreated oocytes. In conclusion, fetuin reduced ZPH in equine oocytes but did not improve sperm penetration during IVF. This implies that, in the horse, "spontaneous" ZPH is unlikely to be the major factor responsible for inhibiting sperm penetration in vitro.

Influence of fetuin and hyaluronan on the post-thaw quality and fertilizing ability of Holstein bull semen

“…It is involved in important physiological functions such as the post-thaw motility, capacitation ability and antioxidant capacity of the sperm cell [19,26,31]. Fetuin is both a major glycoprotein component of foetal calf serum (FCS) and a protease inhibitor, and has been shown to inhibit zona pellucida hardening during the in vitro maturation of mouse [50] and equine oocytes [24]. Similar to bovine serum albumin (BSA), fetuin is a commercially available protein, which improves sperm motility.…”

Recovery of Functional Oocytes from Cultured Premeiotic Germ Cells After Kidney Capsule Transplantation

“…Oocytes subjected to IVF were derived from cumulus-oocyte complexes (COCs), since the zona pellucida hardening of cumulus-denuded oocytes (DOs) during IVM [57], prevented IVF and reduced the rate of blastocyst development [19,46,58].…”

Brown-Swiss Boğa Spermasının Dondurulmasında Çözündürme Sonrası Mikroskopik ve Oksidatif Stress Parametreleri Üzerine Farklı Antioksidanların Etkileri

“…Oxidative stress is the result of an extreme production of ROS and/or diminishes in the antioxidant defence system, and these oxidative stress targets lipids, proteins and DNA [9] . Fetuin, which is a micro heterogeneous protein, appears in fetal calf serum and a protease inhibitor, and has been shown to inhibit zona pellucida hardening during the in vitro maturation of equine oocytes [10] . In additionally, fetuin is a commercially available protein, which improves sperm motility [11] .…”