Regulation of the ovarian inflammatory response at ovulation by nuclear progesterone receptor

Problem: The nuclear progesterone receptor (PGR) transcription factor is essential for ovulation; however, the exact mechanisms by which PGR controls ovulation are not known. The aim of this study was to determine whether PGR regulates inflammatory mediators in the ovary. Method of Study: Ovaries from mice lacking PGR (PRKO) and heterozygous PR+/-littermates were subjected to microarray analysis of a large panel of inflammatory genes. Immune cell subsets were detected by gene expression; and neutrophils by immunohistochemistry and chemotaxis assay. Results: PRKO ovaries exhibited dysregulated expression of vasodilator (Edn1), cytokine (II-6, Tgfb1), adhesion receptor (Cd34), apoptotic factor (Bax) and transcription factors (Nfkb2, Socs1, Stat3). Ptgs2 was also reduced in PRKO ovaries, but mRNA and protein were not different in granulosa cells. There were reduced neutrophils in ovaries of PRKO mice at ovulation; however, chemotaxis assays showed PRKO neutrophils migrate normally and that PRKO ovarian extracts exhibit chemotactic properties in vitro. Conclusion: Specific inflammatory mediators are altered in the ovaries of PRKO mice indicating that progesterone regulates features of inflammation at ovulation.