Reproduction Abstracts

In livestock ruminant species including sheep and cattle, high fertilisation rates shown around 80%, do not necessarily equate to successful pregnancy. Deficient uterine function is therefore a major contributory factor to pregnancy failure resulting in embryonic mortality. In humans undergoing IVF treatment for subfertility, approximately only 25% of embryo transfers will successfully implant. To gain a better understanding of the natural implantation environment, in vitro embryo-endometrium models have the potential to overcome studying inaccessible implantation sites in vivo, and investigate factors required for embryo attachment.

The aim of this study was to establish an ovine three-dimensional (3D) co-culture implantation model, to assess blastocyst attachment, and provide a functionally viable model for future study of specific aspects of implantation. In this preliminary study, both uteri and ovaries were collected from a local abattoir. Endometrial primary cell cultures were constructed from epithelial monolayers grown on collagen cell inserts, co-cultured with monolayers of stromal cells to maintain endometrial epithelial–stromal architecture. IVF was performed on aspirated oocytes, and embryos were cultured to blastocyst stage (days 6–8), simultaneous to the endometrial culture, steroid treated to induce uterine receptivity. Co-cultures were constructed using pooled blastocysts randomly allocated to microwells containing cell inserts of confluent epithelial/stromal constructs for 48 h.

High percentages (82%) of transferred embryos retained their original position and were confirmed attached at respective implantation sites, following agitation of microplates and some lateral outgrowth of trophoblast cells was observed. This model has the distinct advantage of using primary cells as opposed to cell lines, which maintain functional characteristics and are hormone responsive. Preliminary immunofluorescence data detected receptivity biomarkers, integrins and osteopontin on blastocysts and endometrial cells, indicating this model is potentially a future tool for the study of the molecular mechanisms of implantation/failure.