Expression of oestrogen receptor-α splicing variants and oestrogen receptor-β in endometrium of infertile patients

Endometrium is one of the main target tissues of oestrogens. Although homozygous inactivation of oestrogen receptor-alpha leads to infertility in transgenic mice, oestrogen receptor-alpha is detected in endometrium of patients with unexplained infertility. Oestrogen receptor-alpha splicing variants and oestrogen receptor-beta have been studied in oestrogen target tissues, but their expression in endometrium throughout the menstrual cycle and in unexplained infertility is unknown. Using reverse transcription-polymerase chain reaction (RT-PCR), we studied the expression of oestrogen receptor-alpha splicing variants and oestrogen receptor-beta in uterine biopsies from 12 patients with endometriosis and 15 patients with unexplained infertility. A control group included 19 women who had had a previous pregnancy. Our study gave evidence of exon 2, 3, 4 or 7 deleted oestrogen receptor-alpha variants co-existing with the wild-type receptor. We did not find any exon 5 or 6-deleted variants. Exon 4 or 7-deleted variants were detected in all samples. Exon 2 or 3-deleted variants were detected at a similar frequency in fertile women (58 and 68% respectively), endometriotic patients (67 and 83% respectively) and infertile patients (73 and 80% respectively). During the follicular phase, there was a non-significant trend towards a lower frequency of exon-2 deleted variants in the fertile group when compared with the hypofertile group. Oestrogen receptor-beta was detected in all samples. Our preliminary study showed that altered expression of oestrogen receptor-alpha variants and oestrogen receptor-beta may not explain the hypofertility state.