Rejuvenation of aged oocyte through exposure to young follicular microenvironment

Reproductive aging is a major cause of fertility decline, attributed to decreased oocyte quantity and competence. Follicular somatic cells play crucial roles in the growth and development of the oocyte by providing nutrients and regulatory factors. Here we investigated how oocyte quality is affected by its somatic cell environment by creating chimeric follicles, whereby an oocyte from one follicle was transplanted into and cultured within another follicle whose native oocyte was removed. Somatic cells within the chimeric follicle re-establish connections with the oocyte and support oocyte growth and maturation in a three-dimensional (3D) culture system. We show that young oocytes transplanted into aged follicles exhibited reduced meiotic maturation and developmental potential, whereas the young follicular environment significantly improved the rates of maturation, blastocyst formation and live birth of aged oocytes. Aged oocytes cultured within young follicles exhibited enhanced interaction with somatic cells, more youth-like transcriptome, remodelled metabolome, improved mitochondrial function, and enhanced fidelity of meiotic chromosome segregation. These findings provide the basis for a future follicular somatic cell-based therapy to treat age-associated female infertility. To investigate how oocyte quality is affected by its somatic cell environment by creating chimeric follicles, whereby an oocyte from one follicle was transplanted into and cultured within another follicle whose native oocyte was removed. We then perform RNA-sequencing analysis on individual oocytes isolated from reconstituted chimeric follicles (RCFs), which include young oocytes with young somatic cells (RCF-YY), aged oocytes with aged somatic cells (RCF-AA), and aged oocytes with young somatic cells (RCF-AY). Additionally, we perform RNA-sequencing analysis on oocytes from young mice, with and without in vitro culture, serving as controls.