Lack of expression of endometrial prolactin in early implantation failure : a pilot study

BACKGROUND: Animal models and experimental studies suggest a role for paracrine prolactin (PRL) signalling in decidualization and embryo implantation. We investigated the expression of endometrial prolactin (e-PRL) and prolactin receptor (PRL-R) in the endometrium of women affected by unexplained infertility (UI) and repeated miscarriages (RM). METHODS: Patients (n 5 24) were divided into three groups: RM, n 5 5; UI, n 5 11; controls, n 5 8. Endometrial samples were collected at the time of hysteroscopy in the late luteal phase. The presence of transcripts of e-PRL and PRL-R was investigated by qualitative RT–PCR. Pattern and site of expression of e-PRL were studied by immunohistochemistry. RESULTS: PRL-R mRNA was detected in all endometrial samples of the three groups. PRL gene expression was detected in all control samples, only in three of five samples of the RM group and in four of 11 samples of the UI group. RT–PCR results were largely confirmed by immunohistochemistry, study groups showing a defect of expression of e-PRL. CONCLUSIONS: In this pilot study we report a lack of expression of endometrial prolactin during the ‘implantation window’ in some patients affected by unexplained infertility and repeated miscarriages. These data, in association with those obtained in experimental animals, suggest that the lack of endometrial PRL expression is involved in reproduction failure.