HucMSC-mediated stromal metabolic reprogramming in reactivating aged ovaries: a single-cell transcriptomic perspective.

BACKGROUND: Aging-induced decline in ovarian function and oocyte quality contributes to female infertility. However, the mechanisms underlying human umbilical cord-derived mesenchymal stem cell (HucMSC)-mediated rejuvenation of aged ovaries remain poorly understood. This study aimed to systematically investigate whether and how HucMSCs restore ovarian function and oocyte quality and elucidate the potential pathways involved.
METHODS: Aged mice received in situ ovarian injections of HucMSCs. Ovarian follicular development and fertility outcomes were assessed. Low-input RNA-seq and single-cell RNA sequencing (scRNA-seq) were applied to evaluate transcriptomic heterogeneity in oocytes and somatic cells separately. Additionally, the molecular change and function of HucMSC-primed stromal cells (SCs) in aged ovaries were assessed to validate SCs' functional roles in ovarian microenvironment improvement.
RESULTS: HucMSC treatment enhanced follicular development, increased antral follicle numbers, and partially restored fertility in aged mice. Oocyte transcriptomes in HucMSC-treated mice resembled those of young mice, with 75% of aging-dysregulated genes (notably mitochondrial respiratory chain complex assembly-related genes) reverting to youthful expression patterns. scRNA-seq revealed upregulated transcription and glycolysis in granulosa cells (GCs), alongside stromal cell fate redirection toward steroidogenesis and folliculogenesis instead of fibrosis. Transplantation of HucMSC-primed SCs replicated these restorative effects. Mechanistically, HucMSCs promoted pregnenolone synthesis in stromal cells, facilitating follicular development.
CONCLUSIONS: HucMSCs reactivate aged ovaries by inducing metabolic reprogramming in both oocytes and somatic cells, enhancing mitochondrial function in oocytes, and redirecting stromal cells toward steroidogenic and folliculogenic pathways. These findings underscore stromal cell functional modulation as a critical mechanism in counteracting ovarian aging and revealing the potential of stromal cells as therapeutic targets.