Objective
To study the expression of leukemia inhibitory factor (LIF), its receptors LIFR and gp130, and its inhibitor SOCS1 in endometria from fertile women and infertile women with unexplained infertility. Signaling through the LIF pathway is involved in maintenance of a receptive state of human endometrium. Impaired endometrial receptivity may be a cause of female infertility. Design: Prospective clinical study. Setting: Hospital-based IVF unit and university-affiliated reproductive research laboratories. Patient(s): Twenty-six healthy fertile women and 14 women with unexplained infertility. Intervention(s): Endometrial biopsy. Main outcome measure(s): Pinopode formation, expression of LIF, LIFR, gp130, and SOCS1 protein and mRNA in endometrial biopsies. Result(s): The expression of LIFR in the endometrium was negatively correlated to the expression of SOCS1 and positively correlated to the formation of pinopodes. In control fertile women, simultaneous intense apical staining of LIFR and gp130 together with faint SOCS1 staining was observed in epithelial cells, whereas the opposite was seen in most women with unexplained infertility.