Exosome-enriched extracellular vesicles versus serum in corneal epithelial wound healing: An exploratory preclinical study.

This study compared short-term epithelial and stromal responses associated with human umbilical cord mesenchymal stem cell (hucMSC)-derived exosome-enriched extracellular vesicle treatment and serum therapy in a rabbit corneal epithelial defect model. Three groups were evaluated: exosome-enriched extracellular vesicles, 20% pooled human serum, and preservative-free artificial tears as a supportive-care control. Exosome-enriched extracellular vesicle characterization included nanoparticle tracking analysis and CD9-based flow cytometry, while parental hucMSCs were characterized by phase-contrast morphology and flow cytometric expression of CD90, CD44, CD73, and CD105. Fifteen animals were analysed (exosome-enriched extracellular vesicle group n = 6, serum group n = 5, artificial tear control group n = 4). Mean epithelial closure time was 3.50 ± 0.54 days in the exosome-enriched extracellular vesicle group, 4.00 ± 0.70 days in the serum group, and 4.75 ± 0.96 days in the artificial tear control group; however, this difference did not reach statistical significance (p = 0.081). Post-hoc power for the primary endpoint was low, approximately 22%, indicating that the study was underpowered for efficacy or superiority conclusions. Stromal thickness was higher in the exosome-enriched extracellular vesicle group (p = 0.001), but this finding was not accompanied by significant differences in stromal oedema, fibrosis, or cellularity scores. Therefore, the increased stromal thickness remains mechanistically unexplained within the limits of the present dataset. These findings should be interpreted as exploratory observations from a small preclinical study. Larger, adequately powered studies incorporating expanded extracellular vesicle characterization, longer follow-up, and mechanistic endpoints are required before therapeutic efficacy can be inferred.