Adipose tissue-derived stem cell exosomes enhance skin barrier function and show exploratory associations with the skin mycobiome in aging skin.

Skin aging increases transepidermal water loss (TEWL), reduces elasticity, and perturbs the skin microbiome. Adipose tissue-derived stem cell exosomes (ASCE) show regenerative potential; however, their clinical effects on skin physiology and microbiome remain unclear. We conducted a split-face, randomized controlled trial in 16 adults aged ≥ 40 years with visible facial aging. One facial side received ultrasound-assisted transdermal delivery of a human ASCE-containing solution (HACS), whereas the other side received normal saline, at two-week intervals for three sessions. Biophysical outcomes (TEWL, stratum corneum hydration, and elasticity parameters R2/R5/R7) were assessed at baseline and week 2, 4, and 8. Wrinkles, pigmentation, and sebum levels were quantified using Mark-Vu imaging, and the Physician's Global Aesthetic Improvement Scale (PGAIS) and patient satisfaction assessment scores were recorded. Skin swabs from ten participants were subjected to 16S rRNA and ITS1 sequencing. HACS treatment significantly reduced TEWL (p = 0.006 at week 2; p = 0.009 at week 8) and increased hydration (p < 0.001 at all time points) with a significant increase in elasticity (R2/R5/R7 values, p < 0.001). Both the PGAIS and patient satisfaction scores were significantly higher on the experimental side. Bacterial α/β-diversity remained largely unchanged, and no bacterial taxa remained significantly associated with skin parameters after FDR correction. In contrast, several fungal taxa showed significant positive associations with skin parameters after FDR correction, detectable only on the HACS-treated side. No significant adverse events were observed. HACS improved barrier function, elasticity, and aesthetic outcomes, whereas microbiome analyses suggested a modest fungal response associated with treatment-related skin changes in aging skin.