High expression of CFTR in cumulus cells from mature oocytes is associated with high-quality of oocyte and subsequent embryonic development

Abstract

Objective: The purpose of this study was to explore the association of expression of cystic fibrosis transmembrane conductance regulator (CFTR) in cumulus cells (CCs) from mature oocytes with oocyte quality and embryonic development.

Methods: A total of 338 infertile women who underwent ovarian stimulation cycle of oocyte retrieval in Zhejiang University School of Medicine were retrospectively enrolled in this study. The relative mRNA expression levels of CFTR, bone morphogenetic protein 15 (BMP15), and growth differentiation factor 9 (GDF9) in CCs were detected by qPCR technology. ROC curve was applied for the diagnosis of oocyte maturation. The serum levels of anti-Müllerian hormone (AMH), E₂, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and androstenedione were measured. Oocyte maturation rate, fertilization rate, cleavage rate, high-quality embryo formation rate, and implantation rate after embryo transfer were also determined.

Results: The mRNA expression levels of CFTR in CCs were significantly increased in metaphase II (MII) oocytes compared to that in metaphase I (MI) or germinal vesicle (GV) oocytes. The ROC curve analysis illustrated that CFTR mRNA expression could efficiently discriminate MII oocytes from MI or GV oocytes (AUC = 0.954), and revealed that 0.695 RQU is the optimal cut-off value for diagnosis. So the cut-off value of 2^-ΔΔCT = 0.70 was used to divide the patients into two groups: low- (n = 114) and high-CFTR group (n = 224). The mRNA expression of CFTR in CCs was positively correlated with the antral follicular count (AFC), number of oocytes retrieved, number of MII oocytes, serum E₂ level on hCG day, and BMP15 and GDF9 expression in CCs. Under continuous stimulation with the same dose of recombinant follicle-stimulating hormone (rFSH), the number of follicles, average recovered oocytes, recovered oocytes, MII oocytes, as well as the oocyte recovery rate, fertilization rate, oocyte cleavage rate, high-quality embryo formation rate, and implantation rate were decreased in patients with lower CFTR.

Conclusions: This study suggests that CFTR expression in CCs is associated with the developmental potential of human oocytes.

Keywords: CFTR; Cumulus cell; Embryo; In vitro fertilization; Infertility; Oocytes.

Fig. 1

CFTR expression level in CCs from oocytes at GV, MI, and MII stage, respectively. Each dot represents CFTR expression values (2^−ΔΔCT) from CCs in one cumulus corona oocyte complexes. The CFTR expression in CCs from MII (0.99 ± 0.29) oocytes was significantly higher in comparison with the CCs from GV (0.31 ± 0.12) or MI (0.55 ± 0.17) oocytes. Data are presented as means ± SD, n = 36/group, double asterisks (**) indicate P < 0.01, triple asterisks (***) indicate P < 0.001, by one-way ANOVA

Fig. 2

ROC curve analysis for CFTR mRNA expression in CCs for oocyte maturation. Receiver operating characteristic (ROC) analysis showed that CFTR mRNA expression in CCs was useful to identify MII oocytes from GV and MI oocytes under the curve (AUC) of 0.954, and the diagnostic sensitivity or specificity was 84.5% and 94.4%, respectively

Fig. 3

Correlation between the CFTR expression in CCs and the number of antral follicular count (AFC), number of oocytes retrieved, number of MII oocytes, serum E₂ level on hCG day, and the expressions of BMP15 and GDF9 in CCs. The mRNA levels of CFTR, BMP15, and GDF9 in the CCs were examined by qRT-PCR. The serum E₂ levels on hCG day were examined by electrochemiluminescence immunoassay (n = 338). Pearson’s correlation analysis was performed to examine the correlation between CFTR levels in CCs and A antral follicle count (AFC), B number of oocytes retrieved, C number of MII oocytes, D serum E₂ levels on hCG administration day, E BMP15 and F GDF9 mRNA levels in CCs