Regulation of amphiregulin, EGFR-like factor expression by hCG in cultured human granulosa cells

It has long been suspected that the epidermal growth factor (EGF) receptor and some of its putative ligands may play an important role in ovarian function. Amphiregulin (AR) is the growth factor with an EGF-like motif, but its potential role in signalling in the ovary is still obscure. AR gene expression and its functional effect were evaluated in human granulosa cells from immature follicles.

Granulosa cells from immature follicles with early menstrual phase were cultured with or without 200 mIU/ml of FSH stimulation, following with or without 1 IU/ml of hCG. mRNA levels of AR and luteinising hormone replacement (LHR) were semi-quantified using RT-PCR. Progesterone (P) concentration in the medium was assayed.

LHR mRNA was expressed 48 h after FSH stimulation without AR mRNA expression. AR mRNA was expressed 1 h after hCG stimulation, and increased the intensity in 6 h. P biosynthesis was increased by AR in a dose-dependent manner. AR mRNA was elevated by forskolin stimulation without FSH and hCG stimulation before LHR mRNA expression. When cultured with FSH for 15 h, followed by increasing doses of hCG stimulation for 6 h, the AR mRNA levels increased according to hCG concentration up to 1,000 mIU/ml.

Occurrence of LHR gene expression following FSH stimulation was necessary for the AR gene expression in vivo, and the AR gene was induced by forskolin without LHR gene expression in vitro. P biosynthesis was stimulated, to some extent, by AR. This result suggests the differentiation effect of AR on granulosa cells. AR might be a mediator of LH signals before ovulation.