Ovarian premature aging: VIP as key regulator of fibro-inflammation and foamy macrophages generation

Ovarian aging is associated with fibro-inflammation, contributing to the decline in oocyte count and quality. Given the immunomodulatory properties of the vasoactive intestinal peptide (VIP) in the reproductive tract, we investigated its role in maintaining ovarian immune homeostasis and preventing premature aging. We evaluated young VIP knockout (KO) mice, comparing them to young wild type (WT) females, for signs of premature aging. Histological staining revealed aberrant ovarian morphology in VIP KO mice, characterized by increased atretic follicles and decreased ovarian reserve compared to WT controls. Moreover, VIP KO ovaries showed reduced vascularization, increased collagen deposition and elevated ROS and IL-1β levels. Foamy macrophages were significantly predominant, indicating premature aging in young VIP KO ovaries. To determine potential mechanisms behind these pathogenic changes, we conditioned peritoneal macrophages from young WT or VIP KO mice in vitro with ovarian-conditioned media from young WT or VIP KO mice to mimic the respective ovarian microenvironment. When WT or VIP KO peritoneal macrophages were conditioned with ovarian media from their respective genotypes, lipid droplet accumulation increased compared to control medium. In cross-genotype experiments, WT macrophages conditioned with media from VIP KO ovaries selectively accumulated higher levels of lipid droplets, whereas no differences were observed in VIP KO macrophages conditioned with WT ovarian media. This suggests that VIP KO macrophages are uniquely sensitized to the inflammatory environment of VIP KO ovaries, implicating both ovarian factors and macrophage status. These findings highlight the role of VIP in preventing fibro-inflammation, thereby preserving ovarian health and preventing premature aging.