Subcutaneous White Adipose Tissue Derived from Female Mice Achieves Better Graft Outcomes Through the Involvement of...

Fat grafting is one of the most commonly applied procedure for soft-tissue repair. Being heterogenous in nature, sex may influence fat graft retention and quality, potentially affecting clinical outcomes. However, this aspect remains largely unexplored. The present study aimed to determine fates of fat grafting of subcutaneous white adipose tissue (sWAT) from immunocompetent and nude mice of both sexes, along with the contributing mechanisms. In this study, immunocompetent and nude mice of both sexes served as both donors and recipients. sWAT derived from immunocompetent female mice exhibited the optimal wet weight and histological score compared to that from immunocompetent male mice and nude female mice, indicating that tissue-resident T cells in addition to sex hormone, play an indispensable role in determining fat graft outcomes. We then assessed the proportion of the subtypes of tissue-resident T cells within sWAT using flow cytometry and found that CD4⁺Foxp3⁺ T regulatory (Treg) cells were significantly more abundant in female mice compared to male mice, while other T cell subtypes showed no significant differences. Further, Tregs sorted from peripheral blood mononuclear cells (PBMCs) were mixed with sWAT at ratios of 0.1, 0.2, 0.5, 1.0 million Tregs/0.1 mL. CD4⁺CD25^- T effective cells (Teffs) were used as controls. Since Treg-derived exosomes exhibit similar functions to Tregs themselves and reduce immunogenicity, we fabricated the exosomes by ultracentrifugation. These exosomes were then mixed with sWAT at concentrations of 10, 30, 100 and 300μg/0.1 mL, with the same volume PBS used as a control. Improved graft quality (as determined by histological score) was observed when 0.5million Tregs or 300 μg Treg-derived exosomes per 0.1 mL sWAT were transplanted. These results suggest that sWAT from immunocompetent female mice yielded superior fat graft outcomes, partially due to the higher presence of Tregs. Adoptive transfer of Tregs and Tregs-derived exosomes may represent a potential strategy to promote fat graft outcomes. Our findings highlight a possible role of Tregs and their exosomes in fat grafting and emphasize the importance of considering sex-related factors in adipose tissue transplantation. No Level Assigned This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .