Abstract
BACKGROUND: Exosomes derived from adipose-derived stem cells (ADSC-Exos) have emerged as promising therapeutic agents for promoting wound healing through paracrine mechanisms. While adult ADSC-Exos have been extensively studied, those derived from infant ADSCs have received limited attention, despite their potentially superior regenerative capacity. In addition, hypoxia preconditioning has been shown to enhance the therapeutic efficacy of stem cells and their secretome; however, its influence on exosome function across different donor ages remains unclear. This study aimed to evaluate and compare the wound healing effects of ADSC-Exos from adult and infant sources expanded under hypoxic and normoxic conditions in a diabetic mouse model. METHODS: ADSC-Exos were isolated from adult and infant donors cultured under normoxic and hypoxic conditions. Exosomes were characterized by morphology, transmission electron microscopy (TEM) imaging, nanoparticle tracking analysis (NTA), and Western blotting. RNA sequencing was performed to profile miRNAs encapsulated in the exosomes. In vitro assays assessed the effects of exosomes on proliferation, migration, and wound healing in human dermal fibroblasts (HDFs) under high-glucose conditions. In vivo efficacy was evaluated using full-thickness wounds in db/db diabetic mice to assess the therapeutic effects of the exosomes. RESULTS: Normoxic infant ADSC-Exos exhibited a broader size distribution and a larger mean particle size. Several wound-healing-related miRNAs were upregulated in hypoxic ADSC-Exos from both adult and infant sources. Normoxic infant ADSC-Exos significantly enhanced HDF proliferation and migration, whereas hypoxic adult ADSC-Exos exhibited superior early wound closure. In vivo, normoxic adult ADSC-Exos achieved the fastest wound closure at day 7, and normoxic infant ADSC-Exos showed significantly greater wound closure by day 10. All ADSC-Exos promoted dermal regeneration, with hypoxic adult ADSC-Exos showing the most pronounced effects. CONCLUSION: Infant ADSC-Exos demonstrated inherent advantages under normoxic conditions, including enhanced effects on cell proliferation, migration and wound regeneration. While hypoxic preconditioning enhanced the efficacy of adult ADSC-Exos, it provided limited additional benefit to infant-derived exosomes, highlighting their intrinsic suitability for regenerative therapies.