Mammalian reproductive potential declines with age. Several studies show a significant association of advancing maternal-age with stillbirth, reduced fecundity, and elevated risks for pregnancy complications. This loss in reproductive potential in humans is primarily attributed to ovarian aging owing to the postmenopausal decline in ovarian follicular reserve. However, multiple lines of evidence from donor oocyte programs and assisted reproduction programs involving gestational surrogacy suggest that irrespective of the ovarian functional status, uterine age-related changes are, at least partly, responsible for the loss of reproductive potential. How aging influences endometrial homeostasis, and reproductive potential is currently unclear.
Here, we studied extensively the age-related changes in human endometrium both at the cellular and extracellular level, using a wide array of human endometrial samples, patient-derived xenografts, and co-culture organoid models. We used MALDI-MSI, Micromatrix arrays, and Second Harmonic Generation imaging to define the proteomic profile and decipher the extracellular matrix (ECM) dynamics of aged endometrium. Finally, we functionally validated our findings using transgenic mouse models and our novel recellularization model and deciphered molecular signaling pathways that disrupt endometrial homeostasis during aging.
Our results show that aging induces pathological changes in the endometrial stroma that phenocopy tumour microenvironment. These changes are characterized by loss in stromal Hand2 expression, enhanced secretion of growth-promoting factors, and differentiation of stromal fibroblasts into myofibroblasts which alter the ECM dynamics resulting in hyperactive Wnt signaling and endometrial hyperplasia, a precursor for endometrial cancer development. When we ablated Efemp1 genetically and inhibited lysyl oxidase pharmacologically, two of the most upregulated ECM proteins in aged matrisome, from aged murine endometrium, both these interventions independently rescued some of these age-induced changes and restored the endometrial homeostasis. These data provide an integrated view of how aged microenvironment, irrespective of ovarian functional status, disrupts endometrial homeostasis and predisposes postmenopausal women to endometrial cancer development.