In-vitro studies of the effects of interferons on endometrial metabolism in sheep

Primary cultures of ovine epithelial and stromal cells have been used to examine paracrine interactions between the endometrium and the preimplantation sheep blastocyst, and in particular the actions of the blastocyst alpha-interferon, ovine trophoblast protein-1 (oTP-1), on endometrial cell metabolism. The synthesis and secretion of several 'pregnancy-related' acidic proteins with molecular weights in the range 70,000-120,000 can be induced by addition of oTP-1 or human recombinant interferon (IFN) to cultured enriched epithelial endometrial cells. Consistent with the antiluteolytic role of oTP-1, dose-dependent attenuation of both PGE and PGF-2 alpha release has been demonstrated. Arachidonic acid added to the cells increased overall PG release but the inhibitory effects of interferons were still apparent. Immunocytochemical analysis of PG synthase demonstrated marked cyclic variation of its localization within the endometrium, but no differences in distribution or intensity of staining were apparent in endometrium of early pregnancy (Day 15) compared with that of the cycle (Day 15). It appears that conceptus-induced changes in PG release do not occur via changes in concentration or localization of PG synthase but rather by modifying its activity. Highly purified epithelial cells cultured on matrigel-coated millicell inserts retain important morphological features seen in vivo. Under such conditions, PGF-2 alpha and PGE release into the basal compartment was greater than that into the apical compartment. Stromal fibroblasts cultured under similar conditions secreted less PGF-2 alpha but more PGE than epithelial cells. Whilst the limitations of in-vitro studies are acknowledged, these findings are compatible with and markedly extend what is known of the action of embryonic interferons in vivo in the establishment of pregnancy in sheep.