Endometrial LGR7 expression and implantation failure

Implantation failure is considered as a major cause of infertility in women with recurrent pregnancy loss (RPL) and in otherwise healthy women with unexplained infertility. Preliminary data in primates suggested that relaxin (RLX) is involved in endometrial preparation for implantation. In a prospective observational study, the endometrial RLX receptor (LGR7) expression was assessed in three groups of patients with regular ovulatory cycle and normal uterine cavity: 23 with RPL (Group A), 23 with unexplained infertility undergone at least three cycles of failed in vitro fertilization (IVF) reporting good oocyte and embryo quality (Group B), 23 with proven fertility (Group C). Assessment of LGR7 expression was performed with both polymerase chain reaction (PCR) analysis and immunohistochemistry on endometrial samples obtained with hysteroscopic biopsy performed in the secretory phase of the menstrual cycle. Endometrial LGR7 was less expressed in group A and B versus C, both by PCR analysis (p = 0.024) and immunohistochemistry. The decreased expression of the endometrial RLX receptor in women with implantation failures, both in vitro fertilization failure and recurrent pregnancy loss, suggests that RLX may play a crucial role in the structural and functional changes of the endometrium during the window of implantation.