Reproduction Abstracts

Introduction: Implantation is a highly coordinated event in which the receptive endometrium is primed to receive adhesion-competent blastocysts. Implantation relies on the bridging of integrins on the endometrium and the blastocyst by extracellular matrix proteins, such as fibronectin. Factors produced in the female reproductive tract are thought to support development of the blastocyst to an adhesion competent state and to ensure coordination of blastocyst implantation ability with uterine receptivity.

Materials and methods: Murine blastocysts were cultured on Ishikawa cells, a human endometrial cell line, in the presence or absence of IGF1 and assessed for attachment 48 h later. Western-blotting, immunofluorescence, and flow cytometry were used to determine levels of expression of fibronectin, integrins, and focal adhesion kinase (FAK) in Ishikawa cells and blastocysts.

Results and discussion: Attachment of blastocysts to Ishikawa cells in vitro was increased in the presence of IGF1. Treatment of blastocysts with IGF1 increased apical expression of fibronectin. Apical expression of integrin αvβ3, β3, and β1 in Ishikawa cells was unaltered by IGF1 treatment. However, IGF1 treatment increased phosphorylation of FAK and total FAK expression in Ishikawa cells. FAK signalling is known to be linked to integrin activation and this may affect the integrins’ ability to bind and recognise ECM proteins such as fibronectin. This study shows the importance of IGF1 in implantation. Failure of the embryo to implant successfully is the major cause of IVF failure. Understanding how the embryo implants successfully and how this is influenced by growth factors is essential to improve IVF treatment.