Enhancement of cumulus expansion and nuclear maturation during bovine oocyte maturation in vitro by the addition of epidermal growth factor and insulin-like growth factor I

Abstract

This study was carried out to identify the possible effects of epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) on cumulus expansion and nuclear maturation in bovine oocytes matured in vitro in serum-free media. Bovine follicular oocytes were matured in vitro and were then classified as cumulus cell-enclosed oocytes or denuded oocytes. They were then cultured for 24 h in TCM-199 (tissue culture medium-199) with EGF (50 ng ml-1), IGF-I (100 ng ml-1) and EGF plus IGF-I (50 and 100 ng ml-1, respectively). At the end of the culture period, the morphology of oocytes was evaluated for cumulus expansion and nuclear stage of maturation. In Expt 1, percentages of oocytes reaching maximum cumulus expansion were: 12.5% (control), 46.5% (EGF), 15.2% (IGF-I) and 52.8% (EGF plus IGF-I). In Expt 2, the respective rates of nuclear maturation were: 35.6%, 52.1%, 45.5% and 61.4% for cumulus cell-enclosed oocytes, and 35.3%, 46.6%, 45.4% and 42.5% for denuded oocytes; the same growth factor treatments were used in both cases. There was no significant effect of IGF-I on cumulus expansion. Maximum rates of cumulus expansion and nuclear maturation were obtained in the presence of both growth factors. These results lead to the following conclusions: (i) EGF, either alone or together with IGF-I, stimulates cumulus expansion; and (ii) both growth factors, acting alone or together, enhance nuclear maturation in oocytes surrounded by compact cumulus cells.

9‐cis‐retinoic acid during in vitro maturation improves development of the bovine oocyte and increases midkine but not IGF‐I expression in cumulus‐granulosa cells

“…Chromatin was stained with 10 mg/ml propidium iodide for 5 min. After staining, oocytes were washed and mounted between a coverslip and a glass slide supported by silicone (Lorenzo et al, 1994) with antifade mounting medium (Vectashield; Vector Labs, Inc.), and the coverslip was sealed with nail polish. Samples were examined using laser-scanning confocal microscopy.…”

“…Transcripts for IGF-I receptor were noted in the bovine oocyte (Yoshida et al, 1998;Yaseen et al, 2001). Accordingly, the presence of ligand was beneficial to IVM both in cumulus enclosed (Harper and Brackett, 1992;Lorenzo et al, 1994;Pawshe et al, 1998;Sirotkin et al, 1998) and in denuded bovine oocytes (Pawshe et al, 1998;Sirotkin et al, 1998). This suggests that the effect of IGF-I is not necessarily mediated by secretions of surrounding cumulus cells, although IGF-I increases responsiveness of granulosa cells to FSH (Monget and Bondy, 2000).…”

Fertilization Capacity of Mouse Oocytes Matured <i>In Vitro</i>: Effect of PMSG, FSH and Epidermal Growth Factor (EGF) in Serum-Free Maturation Medium

“…However, there was a significant difference between the rate of cumulus-intact oocytes matured with PMSG (89.5%) and without PMSG (45.9%) as shown in Table 2. Finally, EGF, which can induce cumulus-expansion except gonadotrophins [20], had the same effects as gonadotrophins on fertilizability of oocytes (Fig. 3).…”

“…The addition of gonadotrophin or epidermal growth factor (EGF) into maturation medium can enhance the cumulus-expansion [16,20]. Therefore, we examined the effect of the addition of these cumulus-expansion induced substance into maturation medium on the fertilizability of the oocyte.…”

The effect of nutrition and metabolic status on the development of follicles, oocytes and embryos in ruminants

“…Both IGF-1R and IR are also present in the bovine oocytes and embryos (Nuttinck et al, 2004). Several studies have observed that COCs treated with IGF-I, alone or in combination with either epidermal growth factor or angiotensin II, showed increased cumulus expansion, improved rates of nuclear maturation and enhanced metabolism of pyruvate (Lorenzo et al, 1994;Stefanello et al, 2006). The intra-ovarian administration of IGF-I was able to improve the developmental capacity of oocytes from pre-pubertal cattle (Oropeza et al, 2004).…”