Real-time qRT-PCR analysis of EGF receptor in cumulus-oocyte complexes recovered by laparoscopy in hormonally treated goats

Abstract

Ovarian stimulation with exogenous follicle stimulating hormone (FSH) has been used to increase the number of viable oocytes for laparoscopic oocyte recovery (LOR) in goats. The aim of this study was to evaluate the effect of two FSH protocols for ovarian stimulation in goats on the expression pattern of epidermal growth factor (EGF) receptor (EGFR) in cumulus-oocyte complexes (COCs) recovered by LOR. After real-time qRT-PCR analysis, expression profiles of morphologically graded COCs were compared prior to and after in vitro maturation (IVM) on a FSH protocol basis. The use of a protocol with higher number of FSH injections at a shorter interval resulted in GI/GII COCs with a higher level of EGFR expression in cumulus cells, but not in the oocyte, which was correlated with an elevated meiotic competence following IVM. Based on the maturation profile and EGFR expression patterns observed between groups, the morphological selection of COCs prior to IVM was not a good predictor of oocyte meiotic competence. Therefore, EGFR may be a good candidate marker for indirect prediction of goat oocyte quality. The IVM process of goat COCs increased the EGFR expression in oocytes and cumulus cells, which seemed to be strongly associated with the resumption of meiosis. In summary, differential EGFR expression in goat cumulus cells was associated with the in vivo prematuration process, and in turn, the upregulation in the entire COC was associated with IVM. Cause-and-effect relationships between such increased expression levels, particularly in the oocyte, and oocyte competence itself still need to be further investigated.

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

“…2011). We also reported increased EGFR expression in goat COCs after IVM, which appeared to be strongly associated with the resumption of meiosis (Almeida et al. 2011).…”

“…Thus, cumulus cells have higher EGFR mRNA levels in the standard protocol‐derived COCs than in one‐shot‐derived COCs. Previously, our group used a protocol with more FSH injections and a shorter interval, which resulted in COCs with a higher level of EGFR expression in the cumulus cells (Almeida et al. 2011).…”

“…Cumulus ‐oocyte complexes from each ovarian stimulation protocol were selected under a stereomicroscope and graded from GI to GIV based on cumulus cells and homogeneous cytoplasm, as described by Almeida et al. (2011).…”

“…Samples of pooled, immature GI, GII and GIII COCs (Pre‐IVM) and MII and NPB oocytes (Post‐IVM) were collected separately for further RT‐qPCR analyses, according to Almeida et al. (2011).…”

“…Recently, our group reported oocyte production in goats raised in Northeast Brazil using two follicle‐stimulating hormone (FSH) protocols for ovarian stimulation (five vs three injections). The use of the protocol with the higher number of FSH injections resulted in COCs with greater oocyte meiotic competence and higher levels of EGFR expression in the cumulus cells when compared with the treatment with fewer doses (Almeida et al. 2011).…”