Ovarian Extracellular Matrix Mechanics Regulate Oocyte-Follicle Interactions During Female Reproductive Aging

Female reproductive aging is associated with ovarian functional decline, leading to infertility. During aging, biochemical and biophysical changes in the ovarian extracellular matrix (ECM) occur, yet how these properties affect follicle growth and oocyte quality remains poorly understood. Here we describe spatiotemporal changes in the ovarian ECM with age using mass spectrometry, immunohistochemistry, and nanoindentation. While follicle stiffness remains unchanged, stromal matrix remodeling is associated with a ~2.5-fold increase in stiffness. To understand how this increase in stromal stiffness affects age-related follicular dysfunction, isolated young follicles were cultured in soft and stiff hydrogels mimicking young and aged ovarian stromal stiffness, respectively. Higher stiffness lead to a decrease in granulosa cell (GC) proliferation, oocyte quality, and GC-oocyte interactions mediated via transzonal projections (TZPs). RNA-seq revealed TGF-β signaling as a major pathway affected by stiffness, and activation of TGF-β signaling through Smad7 silencing rescued TZP formation and oocyte quality in stiff matrix. These findings provide mechanistic insight into how changes in ECM mechanics contribute to ovarian aging functional decline and reveal potential therapeutic targets to counter fertility loss associated with tissue aging and fibrosis.