DEVELOPMENT OF OVINE EMBRYOS COCULTURED ON OVIDUCTAL CELLS, EMBRYONICFIBROBLASTS, OR STO CELL MONOLAYERS

One- and two-cell ovine embryos were co-cultured on primary monolayer cultures of ovine oviductal cells (OM) and ovine embryonic fibroblasts (EF) or on monolayers of STO cells (STO), a permanent cell line, to d etermine whether a co-culture system could be developed for ovine embr yos utilizing a well-characterized cell line. More than 65% (n = 64) o f embryos co-cultured on OM and STO for 5 days cleaved beyond the ''in vitro'' block whereas only 26% (n = 35) of embryos co-cultured on EF cleaved to the same degree (p < 0.05). Mitotic inactivation of the mon olayer did not alter the response to each cell type. In a second exper iment, development of embryos was similar after co-culture on OM or ST O cells for both 3 and 6 days. Co-culture of zygotes on OM and STO cel ls produced 38 and 33% blastocysts after 6 days of co-culture. After e mbryo transfer, only recipients receiving at least one blastocyst beca me pregnant. About 33% of the transferred blastocysts produced fetuses . STO cell co-culture may provide the same stimulus to development as OM cell co-culture and may be advantageous for study of the requiremen ts for early ovine embryonic development. In addition, STO cells displ ayed contact inhibition and formed monolayers that did not overgrow em bryos as did primary cultures of ovine oviductal cells.