A new model for embryo implantation: coculture of blastocysts and Ishikawa cells.

Objective: To explore and develop a new in vitro implantation model that reflects the main process of embryo attachment and invasion. Study design: One of the limitations in human embryo implantation research is lack of an available in vitro model that faithfully replicates human embryo-uterine interactions. In the present study, we examined the attachment and invasiveness of blastocysts from mice in Ishikawa cell (IK), a human endometrial cell, to clarify whether this new model is suitable to study implantation of embryos. We used IK and placed it in contact with blastocysts to initiate coculture experiments using a specifically designed medium. The culture medium was composed of Ham F-12/Dulbecco's modified Eagle medium (1:1), 30% fetal calf serum, 63.5 nmol/L progesterone, 7.14 nmol/L estradiol-17β, 100 mg/ml of insulin, and 20 ng/ml epidermal growth factor. The culture for 24 h clearly demonstrated that embryos were capable of attachment to the IK and displayed partial invasion. Results: Our results showed that embryos attached to the IK and displayed partial invasion after coculture of blastocysts with IK for 48 h. Conclusions: The model is capable of demonstrating the procedure of attachment and invasion of embryo into the endometrial cells and has promises to be used in studies related to early embryo implantation in human endometrium. [ABSTRACT FROM AUTHOR]