Effect of early pregnancy on the expression of prostaglandin synthases in the ovine thymus.

Thymus is a primary lymphoid organ, must adapt to the presence of fetal alloantigens. Prostaglandins (PGs) have diverse effects to activate or inhibit the immune response, but effects of early pregnancy on the expression of PG synthases in ovine maternal thymus are unclear. In this study, ovine thymic samples were obtained at day 16 of the estrous cycle, and days 13, 16 and 25 of pregnancy. The expression of PG synthases, including cyclooxygenase 1 (COX-1), COX-2, PGE2 synthase (PTGES), and a prostaglandin F2α synthase (Aldo-keto reductase family 1, member B1, AKR1B1), was evaluated using quantitative real-time PCR, Western blot and immunohistochemistry analysis. In addition, the thymus/body ratio was also calculated. Our results showed that the expression of COX-2 mRNA and protein, AKR1B1 mRNA and dimer were up-regulated on day 25 of pregnancy (P < 0.05), and expression of COX-1, PTGES mRNA and protein, AKR1B1 monomer and thymus/body ratio were similar at different stages of pregnancy and the estrous cycle. The immunohistochemistry results showed that the COX-2 and AKR1B1 proteins were located in the stromal cells, capillaries and thymic corpuscles. This is the first study to report that expression of COX-2 and AKR1B1 dimer is up-regulated in the maternal thymus during early pregnancy, suggesting that early pregnancy exerts its effects on maternal thymus, which is involved in immunomodulation during early pregnancy in sheep.