Integrated single cell and spatial transcriptomics reveals the cellular and molecular mechanisms underlying UCMSCs treatment of ovarian aging in tree shrews.

<h4>Background</h4>Ovarian aging reduces fertility and leads to endocrine disorders, umbilical cord mesenchymal stem cells (UCMSCs) therapy has clinical potential, but a deeper understanding of their cellular and molecular regulatory mechanisms is still required.<h4>Methods</h4>The old female tree shrews were received UCMSCs treatment via tail vein injection, at 1 × 10⁷ cells/kg once daily for 3 days. Ovaries and peripheral blood were collected after UCMSCs therapy 3 months, HE staining was performed to observe the number of follicles, ELISA was used to detect the secretion of sex hormones, immunohistochemical and immunofluorescence staining was used to detect the expression of ovarian aging relative markers, and scRNA-seq and spatial transcriptomics were performed on ovaries to map the cellular spatial atlas, analyze aging-related scores, and reveal their cellular and molecular regulatory mechanisms.<h4>Results</h4>UCMSCs increased the number of follicles, boosted the secretion of sex hormones, inhibited the expression of p16, and enhanced proliferation and autophagy(definition) in ovarian aging model of tree shrews, but did not fully recover to the level of the young group. Following UCMSCs therapy, the relative abundances of oocytes, theca cells, granulosa cells, perivascular cells, and epithelial cells increased, whereas those of stromal cells decreased, and intercellular communication between oocytes and granulosa, endothelial, and epithelial cells amplified. Within the follicle microenvironment, oocytes reduce genAge scores, and enhance DNA repair capacity. Granulosa cells reduce celluar senescence(definition) scores, downregulate CDKN1A, and increase proliferation. Theca cells exhibit enhance DNA repair. Stromal cells exhibit an expanded progenitor pool at the trajectory origin and significantly reduced geneAge and SASP scores. Mechanistically, ubiquitin B (UBB) is involved in positively regulating p53 family protein signaling and is positively correlated with SASP and genAge signatures, UCMSCs therapy significantly downregulated both UBB and p53 expression.<h4>Conclusion</h4>UCMSCs therapy improves the structure and function of the aged ovary, regulates ovarian microenvironment, with UBB emerging as a potential therapeutic target.