SRF2015 ORAL COMMUNICATIONS SRF Post Doctoral Prize Session (3 abstracts)
1University of Manchester, Manchester, UK; 2Central Manchester NHS Foundation Trust, Manchester, UK.
A significant proportion of IVF treatments are unsuccessful due to defects in implantation. The first stage of implantation is an attachment interaction between the trophectoderm (TE) of the blastocyst-stage embryo and the uterine luminal epithelium (LE). Endocrine signalling from the corpus luteum and paracrine signalling from uterine glands, uterine stroma and the embryo promotes LE receptivity. To investigate the LETE interaction we have developed an in vitro model using the human endometrial adenocarcinoma Ishikawa cell line with human and mouse blastocysts. From a cohort of >100, we observed stable attachment of hatched day 6 human blastocysts to Ishikawa cells within 18 h. Immunostaining of attached human blastocysts at 48 h revealed distinct stages of implantation; apoptosis subjacent to blastocysts at the early stages of breaching the LE, TE syncytialisation at points of attachment to LE, and extensive TE syncytialisation at multiple sites of the outgrowing blastocyst after breaching the LE. Hatched mouse blastocysts were competent for stable attachment on day 6 and detailed kinetic analysis demonstrated initial attachments progressed to breaching the LE and TE outgrowth within 24 h. 12/46 attached mouse blastocysts achieved this in ≤12 h. Immunostaining weakly and stably attached mouse blastocysts revealed changes in TE and LE morphology, LE apoptosis and the apical localisation of candidate TE-LE attachment proteins such as integrin αvβ3, CD44, and osteopontin. Together these data evidence mechanisms of blastocyst attachment to and progression beyond the LE, and validate this in vitro model as a tool to develop treatments for implantation failure.