Cellular Interaction Regulates Interleukin-8 Secretion by Granulosa-Lutein Cells and Monocytes/Macrophages

Peri-ovulatory migration of leukocytes towards the follicle plays an important role during corpus luteum formation. In this study, we examined the secretion of the neutrophil chemoattractant interleukin (IL)-8 by ovarian GL cells and the role of monocytes in IL-8 secretion. Granulosa-lutein cells were isolated from the pre-ovulatory follicle. After depletion of contaminating leukocytes, GL cells were co-cultured with the myelo-monocytic cell line THP-1. Intracellular IL-8 accumulation, IL-8 secretion, and chemotactic activity of cell culture media were examined. Intracellular IL-8 was predominantly localized in the endoplasmatic reticulum-Golgi both in GL cells and in THP-1 cells. In co-cultured cells, intracellular IL-8-specific immunofluorescence and IL-8 secretion were increased compared with either GL cells or THP-1 cells that were cultured alone. Conditioned cell culture media from GL cells and THP-1 cells induced directed cell migration by neutrophils. Human GL cells constitutively synthesize IL-8. An increased IL-8 secretion by co-cultured GL cells and THP-1 cells suggest that GL cells and monocytes mutually induce chemokine secretion. An initial interaction between GL cells and ovarian leukocytes may therefore contribute to an increased chemokine release and leukocyte recruitment to the forming corpus luteum.