Oncostatin-M: A Novel Leukocyte-Derived Factor Facilitating the Ovulatory Process in the Human Ovary

Leukocytes, known as key effectors for ovulation, were found to specifically express oncostatin-M (OSM), while its receptors (OSMR and IL6ST) were abundant in granulosa cells, as shown in single-cell transcriptomics of follicular aspirates. OSM levels in the follicular fluid ranged 20.99 to 429.81 pg/ml. Increases in OSM-positive cells and OSMR and IL6ST expression were detected in ovulatory follicles post-hCG administration. Treating recombinant human OSM protein (rhOSM) to hCG-primed human granulosa/lutein cells activated signaling mediators, e.g., STATs. This treatment enabled hGLC cultures to mimic the in vivo ovulatory steroidogenesis dynamic, characterized by increased progesterone and reduced estradiol, unlike hCG alone. Additionally, rhOSM modulated gene expression associated with various ovulatory changes. This evidence suggests that leukocyte-derived OSM is a groundbreaking factor in human ovulation. Overall design: Cultured human granulosa-lutein cells treated with hCG and hCG+rhOSM were used to perform RNA-seq analysis.