Endocrine Abstracts

Background: Ovarian ageing involves progressive extracellular matrix remodelling, resulting in increased stiffness, fibrosis and disrupted ovarian function. Biomechanical studies using nano-indentation and atomic force microscopy (AFM) have demonstrated stiffness changes between young and aged ovaries; however, the evolution of these mechanical properties across reproductive transitions remains unknown. Understanding these shifts is crucial to delineate how the ovarian microenvironment adapts to hormonal and structural changes throughout life.

Aim: To investigate changes in ovarian stiffness across reproductive transitions using AFM and to elucidate the contributions of distinct ovarian structures to these biomechanical properties.

Methods: Mouse ovaries were collected at six distinct ages representing pre-puberty (14, 21 days), reproductive maturity (3, 6 months), and ageing (12, 18 months). AFM-based indentation was used to quantify stiffness as Young’s Modulus. Analyses assessed: (1) intra-organ stiffness variation, (2) reproducibility across biological replicates, and (3) differences between age groups. Concurrent optical mapping enabled spatial correlation between stiffness and ovarian substructures. n = 4 biological replicates per group.

Results and discussion: Assessment of ovarian stiffness across reproductive transitions indicated that Young’s Modulus was highest in pre-pubertal and aged ovaries with median values of 271.1 Pa and 148.0 Pa, respectively. While stiffness increases prior to gonadotrophin exposure and again as oestrous cyclicity is disrupted/arrested, ovaries at reproductive peak displayed the lowest stiffness (median of 90.4 Pa), suggesting a softer microenvironment during this stage. Within individual ovaries, spatial heterogeneity in stiffness was observed at all ageing timepoints. Importantly, this variation could not be explained solely by cortex–medulla differences, indicating that heterogeneity may be driven by variations in follicle subtype and the surrounding stromal microenvironment. Together, these results reveal dynamic changes in ovarian stiffness across reproductive transitions and underscore the importance of future studies to map the structural, mechanical, and extracellular matrix determinants underlying these alterations.