Goat oocyte production by standard or one-shot FSH treatments and quantitative analysis of transcripts for EGF ligands and its receptor after in vitro maturation

Abstract

Hormonal ovarian stimulation may affect the success of embryo production by regulating transcripts in recovered cumulus-oocyte complexes (COCs). Here, in parallel to morphological classification and in vitro maturation (IVM) rate analysis, we investigated the expression of epidermal growth factor (EGF) and its receptor (EGFR) in oocytes and cumulus cells from goat COCs recovered by laparoscopy after standard [multi-dose follicle-stimulating hormone (FSH)] or one-shot (single dose FSH plus eCG) treatments. No differences were observed among the number of recovered and morphologically graded COCs or the IVM rates for both gonadotropic treatments. However, the standard protocol produced COCs with higher EGFR expression in the cumulus cells than the one-shot treatment. Additionally, EGF mRNA levels were less than EGFR mRNA levels, and they did not differ among COCs from both treatments. However, during maturation, the EGF transcripts increased in oocytes derived only from the standard protocol. Interestingly, IVM strikingly increased EGFR expression in oocytes and cumulus cells but not in oocytes that fail in first polar body extrusion, irrespective of hormonal treatment. These results appear to be related to the resumption of meiosis and suggest that EGF may act through the cumulus cells or directly on the oocyte receptor.