Fig. 3.

PGE2 in the fertilization process. PGE2 disassembles the cumulus ECM for sperm penetration and inhibits the phagocytic activity of PMNs against sperm. a Cumulus ECM assembly: In cumulus cells, LH and IL-1β respectively induce the expression of the chemokines CCL7 and CCL2. CCL7 and CCL2 bind the chemokine receptor CCR to induce cumulus cell-ECM assembly. b Cumulus cell-ECM disassembly: Upon ovulation, there is an increased level of PGE2 secreted by oviduct epithelial cells and the cumulus oophorus. PGE2 inhibits IL-1β and increases intracellular cAMP concentrations, respectively resulting in decreased expression levels of CCL2 and CCL7; these actions subsequently result in the disassembly of the cumulus ECM. The disassembly of the cumulus ECM leaves a free space for sperm penetration into the oocyte for fertilization. c In the oviduct, sperm binding to epithelial cells, as well as LH stimulation, induce PGE2 secretion. The released PGE2 inhibits neutrophil binding to the sperm and NET formation. Sperm in the presence of PGE2 have increased mobility, survival and binding capacity to the oocyte