MODEL SYSTEM FOR THE STUDY OF UTERINE TROPHOBLAST INTERACTIONS IN THEMARE

A culture system designed to examine events associated with maternal r ecognition of pregnancy in the mare was developed using trophoblastic vesicles and monolayers of uterine epithelial cells. Equine uterine ep ithelial cells were harvested from endometrial biopsy tissue obtained from pregnant and nonpregnant mares and a homogenous population of lum inal and glandular epithelial cells was isolated by mechanical/enzymat ic dissociation. To create polarized monolayers of uterine epithelial cells, isolated cells were plated on extracellular matrix-coated cultu re inserts. Polarity of the confluent monolayer two weeks after platin g was demonstrated by ultrastructural analysis showing apical microvil li, tight junctions and desmosomes in the apico-lateral membranes of t he cultured cells. Trophoblastic vesicles were generated for use in co -culture with the uterine cells and for the development of monolayers of trophectodermal cells. Functional studies using a fluorescence (car boxyfluorescein) recovery after photobleaching assay (gap FRAP) evalua ted the degree of gap junction-mediated intercellular communication be tween monolayers of uterine cells. Endometrial cells isolated from mar es either during pregnancy or diestrus were capable of cell-cell commu nication. Gap-junction mediated intercellular communication was also d etected between trophectodermal cells in culture. The determination of the extent of cell-cell communication as well as the identification o f specific signal pathways within endometrial cells can be monitored u sing the model in an effort to identify signalling events important to equine embryo recognition. The model may also have valuable potential as a research tool for the study of prostaglandin synthesis and prote in synthesis during early pregnancy in the mare.