Paracrine regulation of the production of embryotrophic oviductal complement componenet-3 and the expression of embryonic complement receptor-3 in a human oviductal cells-mouse embryo coculture system

Abstract

The oviduct secretes embryotrophic proteins. Human oviductalepithelial cells express complement component-3 (C3) protein and its derivatives (Lee et al., 2004). Among the C3 and derivatives,iC3b was most potent in stimulating mouse embryo development in vitro. The production of oviductal iC3b is higher in pregnantthan pseudopregnant mice (Lee et al., 2009). To further unveilthe embryotrophic action of iC3b, the regulation of oviductalC3 production and the expression of potential iC3b receptor, complement receptor-3 (CR3), in mouse embryos were studied. Mouse embryos at 2-cell and 3-4 cell stages were cocultured with primary human oviductal epithelial cells (OE) for 48 hours. The expression of C3 in the OE cells, and the components ofCR3: CD18 and CD11b, in the mouse embryos were studied. Co-culturing with mouse embryos stimulated the production of C3 mRNA in OE cells. Embryos at 3-4 cell stage were more potent than those at 2-cell stage in imposing the stimulatory effect. Immunocytochemicalstaining demonstrated stronger CD18 than CD11b signals in mouseembryos after coculturing with OE cells. The cocultured mouseembryos expressed higher levels of CD18 than CD11b transcriptswhen compared to embryos cultured in medium alone. The oviductalcells and the preimplantation embryos interact to regulate the production of oviductal C3 and embryonic iC3b receptor.