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 F1 alpha (6-keto-PGF1 alpha), the stable metabolites of TxA2 and prostacyclin, 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/microgram protein at 48 h; 6-keto-PGF1 alpha was first detected in medium at 20 h, and it increased to 19.6 +/- 4.0 pg/micrograms 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/micrograms protein; n = 11) by 48 h, but a comparable level of 6-keto-PGF1 alpha (22.5 +/- 3.7 pg/micrograms protein). Trophoblast cultures produced predominantly TxB2 (109 +/- 18 pg/micrograms protein; n = 11) and had the lowest 6-keto-PGF1 alpha production among the three groups (11.4 +/- 2.6 pg/micrograms protein). At 48 h, the mean TxB2/6-keto-PGF1 alpha 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 prostacyclin, 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.