[Insulin-like growth factor II and its receptor gene expression in the endometrium of women with unexplained infertility].

Objective: To investigate the expression of insulin-like growth factor II (IGF-II) and its type I receptor (IGF-IR) and type II receptor (IGF-IIR) in the endometrium of women with unexplained infertility and their relation to steroid levels.

Methods: In situ hybridization method was utilized to detect the location of IGF-II, IGF-IR and IGF-IIR mRNA. Reverse transcription-polymerase chain reaction (RT-PCR) method was employed to detect quantitatively IGF-II, IGF-IR, and IGF-IIR mRNA expression levels in the endometrium during mid-luteal phase. Serum concentrations of estradiol and progesterone were measured by radioimmunoassay. Thirty-eight patients with unexplained infertility were included as study group, and 20 patients with men factor infertility or normal volunteer women were selected as control group.

Results: IGF-II and IGF-IIR mRNA were diffusely distributed in the cytoplasm of stromal cells and IGF-IR mRNA was observed in the cytoplasm of epithelial cells. Endometrial IGF-II, IGF-IR and IGF-IIR mRNA expression during mid-luteal phase in study group were significantly lower than those in the control group respectively (0.71 +/- 0.34 vs 0.96 +/- 0.34, P < 0.05; 0.62 +/- 0.28 vs 0.93 +/- 0.51, P < 0.05; 0.49 +/- 0.27 vs 0.73 +/- 0.36, P < 0.05). The serum progesterone level of study group was significantly lower than that of control group, (34 +/- 15) nmol/L vs (53 +/- 17) nmol/L (P < 0.05). The levels of IGF-II mRNA were positively correlated with IGF-IR mRNA and IGF-IIR mRNA in both groups. There were significant positive correlations between serum progesterone level and IGF-II, IGF-IR and IGF-IIR mRNA.

Conclusions: IGF-II and its receptors mRNA play important roles in the process of implantation. Their decreased expression in relation with lower progesterone level may be one of the major causes of unexplained infertility.