Effects of the duration of exposure to hormone supplements on cytoplasmic maturation of pig oocytes in vitro

Abstract

The effect of hormone supplements on cytoplasmic maturation in vitro was examined by incubating oocyte-cumulus complexes, in a medium with PMSG (10 iu ml-1), hCG (10 iu ml-1) and oestradiol (1 microgram ml-1) for various periods and then transferring them to medium without added hormones for the remainder of the maturation period. Exposure of oocyte-cumulus complexes to hormone supplements for 2 h improved only germinal vesicle breakdown and maturation rates compared with complexes not exposed to added hormones. The removal of hormone supplements at 20 h after the start of culture enhanced the ability of oocytes to form male pronuclei 10 to 12 h after insemination. Further, the effects of transfer of intact and oocytectomized oocyte-cumulus complexes to hormone-free medium at 20 h on cumulus expansion were examined. The diameter and morphology of the intact oocyte-cumulus complexes were improved after the removal of oocyte-cumulus cell complexes from hormonal exposure. The responses of oocytectomized oocyte-cumulus complexes to hormone were similar to those of intact oocyte-cumulus complexes with the exception of corona radiata expansion. The results suggest that the removal of hormone supplements from maturation media at 20 h after culture enhanced cytoplasmic maturation and cumulus expansion. Further, cumulus expansion does not appear to depend on intercellular communication between cumulus cells and oocytes. Oocytectomy did influence expansion of the corona radiata during culture.

Reversible meiotic arrest in feline oocytes

“…In cattle and mice nearly all oocytes will resume meiosis and the majority (60 to 80%) of those oocytes will progress to MII whether gonadotrophins are present in the medium or not (Sirard and First 1988;Downs et al 2002;Thomas et al 2002;Ali and Sirard 2002). In contrast, reports for porcine oocytes suggest that ,75% of oocytes will undergo GVBD (Laforest et al 2005) but only about half (54%) will achieve metaphase II (Funahashi and Day 1993) in the absence of exogenous gonadotrophins. In our study, only 42% of oocytes cultured in the absence of eCGþEGF reached MII within 24 h of culture, which is similar to the results of Wood et al (1995).…”

Progesterone improves porcine in vitro fertilisation system

“…The addition of a suitable hormone supplement to maturation media enhances nuclear maturation and cumulus expansion (Minato and Toyoda, 1982). However, subsequent studies demonstrated that the removal of hormones improved cytoplasm maturation (Funahashi and Day, 1993). Dode and Graves (2002) have indicated that no sexual steroids need to be added to the maturation medium of pig oocytes because COCs secrete steroids during maturation.…”

“…However, Kim et al (2011) observed a positive effect of oestrogens on oocyte maturation and early embryo culture during the first half of the IVM period. Funahashi and Day (1993) demonstrated that 20 h of maturation with no hormone supplementation would be necessary to improve cytoplasmic maturation. Based on the regulated sequence of hormonal changes during in vivo maturation, some reports established a two-step IVM system consisting of 22-h incubation with hCG and eCG followed by 22-h incubation with hormone-free media (Marques et al, 2007;Gil et al, 2010).…”

“…Oestradiol, progesterone and testosterone are the main steroid hormones that play an essential role during the follicular and luteal phases of the menstrual cycle (Wen et al, 2008). Many researchers have attempted to increase in vitro penetration percentages of porcine oocytes by adding PMSG (Funahashi and Day, 1993), hCG hormone (Raziel et al, 2006) or both (Funahashi et al, 1994;Wang and Niwa, 1995;Faerge et al, 2006;Silvestre et al, 2007). However, no studies have been conducted on the effects of progesterone on in vitro fertilisation (IVF) of porcine oocytes yet.…”

Association Between Embryonic Loss and Damage to the Zona Pellucida by Invasive Micromanipulation During Oviductal Transfer of Early-Stage Embryos in Pigs

“…COCs containing at least three layers of compacted cumulus cells were selected and cultured in NCSU23 medium [13] supplemented with 0.6 mM cysteine, 10 ng/ml epidermal growth factor (EGF), 10% (v/v) porcine follicular fluid, 75 µg/ml potassium penicillin G, 50 µg/ml streptomycin sulfate, 10 IU/ml eCG (ASKA Pharmaceutical, Tokyo, Japan) and 10 IU/ml hCG (ASKA Pharmaceutical) [14,15]. The COCs were cultured for 22 h with eCG and hCG in a humidified atmosphere of 5% CO2 and 95% air at 38.5 C; This was followed by culture for 22 h without eCG and hCG in an atmosphere of 5% CO 2 , 5% O 2 and 90% N 2 [16].…”