Role of Inflammatory Mediators in Human Endometrium during Progesterone Withdrawal and Early Pregnancy1

The role of progesterone (P4) in the regulation of inflammatory mediators interleukin-8 (IL-8), monocyte chemoattractant protein-1, and cyclooxygenase-2 (COX-2) and in the recruitment of leukocyte subpopulations in the endometrium has been examined, by employing a model of P4 withdrawal and maintenance in vivo. Messenger RNA and protein expression have been investigated in endometrial biopsies: 1) during the midsecretory phase (LH+8 to 10); during the maintained luteal phase (P4 administered vaginally for 4 days from LH+8) and biopsies collected 2) 24 h and 3) 48 h post withdrawal of P4; and 4) during pseudo pregnancy (lifespan of corpus luteum extended by 7 days with CG; (decidua collected from women with 5) an ectopic gestation and 6) from women undergoing first-trimester termination of pregnancy). CD56+ large granular lymphocytes remain the major leukocyte subtype, both 24 and 48 h after P4 withdrawal, and in decidua (CG supported or ectopic). Higher numbers (P < 0.05) of macrophages (CD68+) were present in endometrium 48 h post P4 withdrawal and in pseudo pregnant endometrium, compared with normal decidua. Significantly more macrophages (P < 0.01) were present in decidua from an ectopic pregnancy. A significant elevation of IL-8 (P < 0.01) and COX-2 (P < 0.05) messenger RNA was detected 48 h post P4 withdrawal. Evidence is provided for up-regulation of IL-8 and COX-2 in response to P4 withdrawal.