Thromboxane and prostacyclin production by different compartments of the human placental villus

We separated the trophoblast and villous core of human placental villi to compare thromboxane (Tx) and prostacyclin production in these two compartments with eicosanoid production by intact villi. TxB₂ and 6-keto-prostaglandin F_1α (6-keto-PGF_1α), the stable metabolites of TxA₂ and prosta-cyclin, respectively, were measured in serum-free media from 48-h incubations of intact villi, villous core tissue denuded of its trophoblast layer, and trophoblast cells. In villi, the medium TxB2 concentrations increased rapidly to a peak level of 20 ± 9 (±se) (n = 11) pg/μg protein at 48 h; 6-keto-PGF_1α was first detected in medium at 20 h, and it increased to 19.6 ± 4.0 pg/μg protein (n = 11) by 48 h. Compared to villi, villous core tissue denuded of its surface trophoblast layer had a 7-fold greater TxB₂ level (136 ± 17 pg/μg protein; n = 11) by 48 h, but a comparable level of 6-keto-PGFin (22.5 ± 3.7 pg/μg protein). Trophoblast cultures produced predominantly TxB₂ (109 ± 18 pg/μg protein; n = 11) and had the lowest 6-keto-PGF_1α production among the three groups (11.4 ± 2.6 pg/μg protein). At 48 h, the mean TxB₂/6-keto-PGF_1α in ratio was 1.0 in medium from intact villi, 6.2 in medium from villous core tissue, and 13.3 in medium from trophoblast cells. Indomethacin inhibited production of both eicosanoids in all cultures. Our studies indicate that intact placental villi produce equal amounts of Tx and prosta-cyclin, the trophoblast compartment produces predominantly Tx, and the villous core compartment produces an increased amount of Tx when denuded of its trophoblast layer. These data also suggest that the trophoblast produces an inhibitor or provides a catabolic function that limits villous core Tx production.