The Role of Bone Morphogenetic Protein 6 in Accumulation and Regulation of Neutrophils in the Human Ovary

Bone morphogenetic protein (BMP) cytokine is known to regulate ovulation, as BMP-6 null mice exhibit a decrease in the number of ovulatory follicles without effect on either the morphology or the dynamics of follicular development. In the present study, the role of BMP-6 in ovulatory process was investigated using human granulosa-lutein cells (GCs). Granulosa-lutein cells, obtained from in vitro fertilization patients, were cultured with BMP-6 followed by RNA extraction. The neutrophil–chemotactic activity of the supernatant of cultured GC was investigated. Bone morphogenetic protein 6 significantly increased growth-regulated oncogene α (GRO-α) messenger RNA (mRNA) and protein expression in GC. In the neutrophil–chemotaxis assay, the GC supernatant cultured with BMP-6 attracted more neutrophils than control samples, which was negated with anti-GRO-α neutralizing antibody. Bone morphogenetic protein 6 also suppressed the relative expression of the protease inhibitors, secretory leukocyte peptidase inhibitor, and whey acid protein 14 mRNA in GC. Bone morphogenetic protein 6 might play a role in ovulation by increasing the accumulation of neutrophils in the ovulatory follicle and suppressing the effect of protease inhibitors.