Skin Rejuvenation in Aged Mice by Fecal Transplantation Microbiota from Young Mice Feces

Skin aging is an increasingly prominent topic in the context of healthy aging. During the aging process, the skin’s barrier function diminishes, its water content decreases, wrinkles begin to form, and changes occur in the gut microbiota composition. However, the relationship between gut microbiota and skin aging remains unclear. In this study, we explored skin rejuvenation in aged mice through fecal microbiota transplantation (FMT) using feces from young mice. The results demonstrated enhanced water retention, thickened stratum corneum, increased collagen content, and improved epithelial cell differentiation in aged mice following FMT. Notably, FMT particularly increased the abundance of Lactobacillus and Lactococcus in aged mice, which were nearly undetectable in untreated aged mice. Non-targeted and targeted metabolomics analyses indicated that FMT significantly elevated levels of tryptophan (Trp) and its microbiota metabolites (e.g., indole-3-lactic acid (ILA)) in the feces and serum of aged mice. Both Trp and ILA appeared to rejuvenate aged skin by activating the aryl hydrocarbon receptor (AhR) to promote epidermal cell differentiation. In conclusion, FMT from young mice rejuvenated aged skin via Trp-metabolizing bacteria (Lactobacillus and Lactococcus) and Trp-derived metabolites, suggesting that interventions targeting Trp metabolites may effectively improve skin aging.