Multicellular origins of ovarian inflammaging
Age-dependent reproductive decline has become a significant global health concern as the average maternal age at first birth increases. Fertility loss associated with reproductive aging is driven in part by alterations to ovarian composition and function, dysregulation of folliculogenesis and increased inflammatory signaling. Our understanding of the molecular changes underlying ovarian aging has been expanded by single cell and spatial transcriptomic studies, which identified infiltration of immune cells as a feature of ovarian aging. However, the function of these age-associated immune cells and their potential contributions to the inflammaging phenotype remains unclear. In this study we integrate single cell and spatial transcriptomics to define changes in the composition and intercellular signaling in the aging mouse ovary. We identify specific macrophage and T cell subpopulations that increase with age and are key sources of pro-inflammatory signaling in old ovaries. Further, we predict bidirectional signaling between these pro-inflammatory cells and granulosa cell populations that may impair follicular growth and development while promoting immune cell recruitment. These findings provide new insights into the mechanisms that drive ovarian inflammaging. Overall design: RNA-sequencing conducted on single-cell suspensions of whole ovaries  from 2 month old  and ~14 month old C57BL6/J female mice.