Downregulation of human endometrial IL-18 by exogenous ovarian steroids

Problem To evaluate the influence of ovarian steroids on IL-18, IL-15 and angiopoietin-2 mRNA expression in the endometrium in the mid luteal phase. Method of study We quantified IL-18/GAPDH, IL-18 BP/GAPDH, IL-15/GAPDH and angiopoietin-2/GAPDH in the endometrium by quantitative polymerase chain reaction on day 21 of the cycle. We first compared cytokines expression over two natural cycles (n = 15) then between natural and oestrogen-progestin replacement treatment (n = 18). Results Endometrial IL-18, IL-18 BP, IL-15 and angiopoietin-2 mRNA expression did not change over two natural cycles. Addition of exogenous hormones significantly decreased IL-18 and IL-18 BP mRNA expression but not influence IL-15 or angiopoietin-2 ratios. This was also observed with immunohistochemistry. Conclusion Exogenous oestro-progestative hormones influence endometrial IL-18 system expression involved in angiogenesis and in the uterine natural killer (uNK) cell activation pathway during the implantation process.