P–699 Multi-scale study of the architecture, topography and mechanics of the human ovary from prepuberty to menopause: a blueprint for next-generation bioengineering and diagnosis

Study question Does the ovarian ECM have a precise and unique biophysical phenotype, specific to each age, from prepuberty to menopause? Summary answer Differences between healthy prepubertal, reproductive-age, and menopausal ovarian tissue, unravel and elucidate a unique biophysical phenotype of reproductive-age tissue, bridging biophysics and female fertility. What is known already Ovarian engineering has recently emerged to respond to patient needs and offer reliable models for basic research. It has relied on synthetic and natural biomaterials and microfluidics. However, these techniques were designed based on knowledge acquired from 2D cell culture and animal models. Our lack of information on the human ovary hampers our ability to mimic the main features of this organ, for clinical applications. The complex composition and hierarchical structure of its ECM complicates the design of truly biomimetic constructs, notably: fiber morphology, interstitial and perifollicular fiber orientation, porosity, topography, and viscoelasticity, which all play a role in mechanotransduction. Study design, size, duration Ovarian biopsies were taken from prepubertal (mean age [±SD]=7±3 years, n = 21), reproductive age (mean age [±SD]=27±5, n = 26 ) and menopausal (mean age [±SD]=61±6 years, n = 29) patients after obtaining their informed consent. All participating adult subjects were undergoing laparoscopic surgery for benign gynecological diseases not affecting the ovaries. Prepubertal tissue was derived from young cancer patients scheduled for ovarian cortex cryopreservation as a fertility preservation strategy, before being subjected to acute gonadotoxic cancer treatments. Participants/materials, setting, methods All samples were cryopreserved by slow freezing and kept frozen until the day of their analysis. Tissues provided from the same patients (n = 5 per age group) were investigated by scanning electron microscopy (SEM) (fiber, pore and topography analyses) and atomic force microscopy (AFM). A larger number of paraffin-fixed biopsies (prepubertal, n = 16, reproductive-age, n = 21, and menopausal, n = 24) obtained from the biobank of St-Luc’s Hospital were used to conduct computed fiber orientation analysis. Main results and the role of chance Our results revealed a unique ECM architecture at reproductive age, where fibers of intermediate diameter are assembled into thickest bundles compared to prepubertal and menopausal tissues(p < 0.0001). Indeed, during prepuberty the bundles assemble into a tight network with high number of small pores while reproductive-age ovary gain more porosity(p < 0.0001). However, at menopause tissue pore number and area change significantly(p < 0.001). These pore geometry and distribution changes contribute to diffusion and access of key molecules to/from cells, which can be translated into changes in permeability and molecule selectivity with age. Fiber directionality around follicle borders at preantral stages revealed that before and after puberty, secondary follicles appear to modify their microenvironment arrangement locally compared to follicles at earlier stages of development (p < 0.01), by reorienting the majority of collagen fibers below 50°.This could indicate that follicles at this stage require higher fiber contact and adhesion signaling to complete their development and maturation towards ovulation. AFM evidenced a relatively rigid ovarian tissue at prepuberty, softening significantly at reproductive age, then stiffening considerably upon menopause. These differences(p < 0.01) are not only structure-dependent, but also related to biochemical differences in ECM composition, as previously demonstrated in our follow-up of variations in elastic matrisome components from prepuberty to menopause. Limitations, reasons for caution The samples represent single time points from each age group which could present limitations, since following ovary dynamics from prepuberty to menopause in the same patient is not feasible. Wider implications of the findings: Our study provides the first conclusive proof of a link between ECM biophysics and fertility by comparing different stages of ovarian transformation related to a woman’s reproductive life, which will oriente new strategies for infertility prognoses based on ECM biophysics and may become a blueprint for designing functional engineered ovaries. Trial registration number Not applicable