This review highlights recent studies investigating the role of prostaglandin (PG)D2 in reproduction. PGD2 induces sleep, allergic responses, inhibition of platelet aggregation, and relaxation of vascular and non-vascular smooth muscle, and has some roles in reproduction.
Two types of PGD2 synthase are known. Lipocalin-type PGD synthase is present in cerebrospinal fluid, seminal plasma and may play an important role in male reproduction. Another PGD synthase, hematopoietic PGD synthase is present in the spleen, fallopian tube, endometrial gland cells, extravillous trophoblasts and villous trophoblasts, and perhaps plays an important role in female reproduction. Recent studies demonstrate that PGD2 is probably involved in multiple aspects of inflammation through its dual receptor systems, DP and CRTH2. CRTH2 but not DP is a chemo-attractant receptor for PGD2. Interestingly, CRTH2 is a most reliable marker for the detection of human T helper type 2 (Th2) and T cytotoxic type 2 (Tc2) cells, and the percentages of CRTH expressing CD4+-T cells and CD8+-T cells were significantly higher in the decidua especially at the implantation site, suggesting that Th2 and Tc2 cells recruit into the materno–fetal interface, in a PGD2-mediated manner. PGD2 has a very unique effect to inhibit antigen presentation by inhibition of dendritic cell (DC) migration through DP but not CRTH2. PGD2 might appear to contribute to the maintenance of pregnancy by controlling the Th1/Th2 balance and antigen presentation by DCs through its dual receptor systems, CRTH2 and DP.