Control of proteolytic mechanisms during the ovulatory folliculo-luteal transformation

The connective tissue matrix of the ovarian follicle wall is degraded and remodeled during ovulatory rupture and formation of the corpus luteum. The objectives of these studies were to determine the role of tumor necrosis factor-α (TNFα) in ovulatory processes and the role of matrix metalloproteinase-2 (MMP-2) in folliculoluteal transformation, where connective tissue remodeling is critical. The final objective was to determine the ability of TNFα, tumor suppressor protein p53 and discoidin domain receptors (DDR) to modulate MMP activity.; Proestrous ewes were treated with prostaglandin F_2α, to synchronize luteal regression and 36 h later with an agonistic analog of GnRH to evoke a preovulatory surge of gonadotropins. Dominant follicles ovulate approximately 24 h after injection of GnRH.; In antral fluid of ovine preovulatory follicles, TNFα increased after GnRH treatment. Secretion of TNFα by oocyte-cumulus cell complexes was highest at 12 h. Follicular collagenolytic activity increased after incubation with TNFα (6 h) and was negated by the transcriptional inhibitor actinomycin D (AD) and TNFα antiserum. Follicular MMP-2 activity increased throughout the periovulatory period with levels greatest post-ovulation (40 h post-GnRH). Matrix metalloproteinase-2 was localized to connective tissue septa that penetrate the wall of ruptured follicles. Tumor necrosis factor-α increased MMP-2 production; this response was blunted by in vitro AD. Ovulation was blocked by intrafollicular injection of TNFα or MMP-2 antisera. Unruptured follicles luteinized, but were deficient in collagenous/vascularized trabeculae, and produced less progesterone than their control luteal counterparts. Pyknotic cells and cellular fragments were observed along the avascular rim of luteinized unruptured follicles, indicative of cell death. Incubation of follicle explants with antisense p53 decreased MMP-2 activity in the presence of TNFα, indicating that p53 is an intermediate in TNFα modulation of MMP-2 activity. Discoidin domain receptor-2 was localized to surface epithelial cells and vascular compartments of recently ruptured follicles (40 h post-GnRH) and Day 8 CL, indicative of its association in reorientating recently disrupted cells with the extracellular matrix. It appears that TNFα and p53 can modulate MMP activity and DDR participates in reorientation of cells, all contributing to the reorganization of an ovulatory follicle into a fully-competent corpus luteum.