Induction of chemokines and prostaglandin synthesis pathways in luteinized human granulosa cells: potential role of luteotropin withdrawal and prostaglandin F2α in regression of the human corpus luteum

Our objective was to determine the effects of prostaglandin F2α (PGF2α) and withdrawal of luteotropic stimulants (forskolin or hCG) on expression of chemokines and prostaglandin-endoperoxide synthase 2 (PTGS2) in luteinized human granulosa cells. Human granulosa cells were collected from 12 women undergoing oocyte retrieval and were luteinized in vitro with forskolin or hCG. In first experiment, granulosa-lutein cells were treated with PGF2α, the primary luteolytic hormone in most species. In second experiment, granulosa cells that had been luteinized for 8 d had luteotropins withdrawn for 1, 2, or 3 d. Treatment with PGF2α induced mRNA for chemokine (c-x-c motif) ligand 2 (CXCL2) and CXC ligand 8 (CXCL8; also known as interleukin-8) in granulosa cells luteinized for 8 d but not in cells that were only luteinized for 2 d. Similarly, luteinization of human granulosa cells for 8 d with forskolin or hCG followed by withdrawal of luteotropic stimulants, not only decreased P4 production, but also increased mRNA concentrations for CXCL8, CXCL-2 (after forskolin withdrawal), and PTGS2. These results provide evidence for two key steps in differentiation of luteolytic capability in human granulosa cells. During 8 d of luteinization, granulosa cells acquire the ability to respond to luteolytic factors, such as PGF2α, with induction of genes involved in immune function and PG synthesis. Finally, a decline in luteotropic stimuli triggers similar pathways leading to induction of PTGS2 and possibly intraluteal PGF2α production, chemokine expression, leukocyte infiltration and activation, and ultimately luteal regression.