Embryo-luteal cells co-culture: an in vitro model to evaluate steroidogenic and prostanoid bovine early embryo-maternal interactions.

The role of progesterone (P(4)) and prostaglandins (PGs) in bovine early embryonic development and embryo-maternal crosstalk is almost unknown. Here, the in vitro steroidogenic (P(4)) and prostanoid (PGE(2) and PGF(2α)) interactions between bovine embryos and luteal cells (LC) were evaluated. In two experiments, embryos (n = 1.900) were either co-cultured with LC or cultured alone, from days 2 to 7 (day 0 = in vitro insemination). LC were also cultured alone, and medium was used as a control, all groups being cultured either with or without oil overlay of culture medium. Oil overlay of culture medium significantly decreased the amount of P(4), but not of PGE(2) and PGF(2α) measured in culture medium. Embryos and LC had transcripts of genes coding for enzymes of the PGs (PTGS2, PGES, and PGFS) and P(4) (StAR, P450scc, and 3β-HSD) synthesis pathways, and produced P(4), PGF(2α), and PGE(2) into culture medium. Co-culture with LC exerted an embryotrophic effect, significantly increasing blastocyst yield and quality. This indicates a possible direct effect of LC in early embryo development. Embryos did not exert a luteotrophic effect upon LC. This may indicate that early embryos (until day 7) probably do not exert influence in LC main function. It is suggested that production of P(4), PGE(2), and PGF(2α) by early embryos may be associated to autocrine signaling leading to events in development and to paracrine signaling in the endometrium leading to local uterine receptivity.