The intrafollicular inflammatory response during ovulation in women is most likely controlled by high concentrations of active cortisol being synthesized shortly before follicular rupture

Abstract Study question How is the anti-inflammatory response in human follicles controlled during the ovulatory process leading to the expulsion of the oocyte? Summary answer Intrafollicular concentrations of cortisol becomes high close to ovulation concomitant with an exceptionally high biological activity securing a timely and efficient termination of inflammatory processes. What is known already Ovulation has been described as a local controlled inflammatory process resulting in the degeneration of the follicle wall to facilitate oocyte extrusion. Ovulation also affects glucocorticoid metabolism of granulosa cells (GC) and although de novo synthesis of cortisol only occurs in the adrenal cortex the mid-cycle surge induces a change from high expression of HSD11b2, inactivating cortisol to cortisone, to high expression of HSD11b1 which reversibly catalyses cortisol production from cortisone. Furthermore, the high concentrations of progesterone and 17-OH-progesterone within follicles cause dislodging of cortisol from cortisol binding protein (CBP) thereby activating the biological activity of cortisol. Study design, size, duration This prospective study included 50 women undergoing fertility treatment according to a standard antagonist protocol at the fertility clinic at the university hospital of Koege, Denmark. Women donated one follicle for research purpose aspirated at one of four time points during the process of final maturation of follicles; T = 0h, T = 12h; T = 17h; T = 32h and then one additional follicle at OPU at T = 36h Participants/materials, setting, methods The concentration of cortisol and cortisone together with sex steroids were measured by LC-MS/MS in follicular fluid (FF) collected at the above five time points. Whole genome microarray data, validated by q-PCT analysis, was used to evaluate gene expression of CYP11b1, CYP21A2, HSD11b1, HSD11b2 and NR3C1 in GC at the five different time points. Main results and the role of chance The expression of HSD11b1 is strongly upregulated during the ovulatory process. From 0-12h expression is increased 690 times reaching more than 20.000 times higher than at T = 0 during the remaining period. In contrast, expression of HSD11b2 is quickly downregulated by 15-20 times through the ovulatory process. The concentration of cortisol is different from the gene expression but increases significantly from a few ng/ml at T = 0h to around 15 ng/ml at T = 12h—17h and peaks at 40-50 ng/ml at T = 32h—36h. In contrast, cortisone is almost constant from 0 to 17h at a concentration of 30-40 ng/ml being significantly reduced to 10-20 ng/ml at T = 32—36h. Concentrations of progesterone and 17-OH-progesterone increased during the ovulatory process to high levels which in essence displaces cortisol from its binding protein CPB, due to similar binding affinities. This will contribute to high levels of biologically active cortisol close to ovulation, which allows the inflammatory reaction to act on the follicle wall and secure extrusion of the oocyte to oviduct before becoming inhibited by cortisol. Furthermore, a significant decrease in 11-deoxycortisol expression was seen but CYP11B1 expression was below detection limit in GCs. This study provides new information on human ovulation. Limitations, reasons for caution Although 50 women were included more observations at each specific time point would have strengthened the conclusions. Wider implications of the findings For the first time, this study collectively evaluates the temporal effect of cortisol and cortisone concentrations in connection with gene expression profiles of enzymes involved in regulation the inflammatory response during human ovulation which now forms a physiological framework for understanding potential dysregulations in the involved processes. Trial registration number NA