An Adipose-Derived Stem Cell Exosome Sheet Promotes Oral Mucosal Wound Healing

<b>Objective:</b> Oral mucosal wound healing is not completely understood, and effective therapies are lacking. This study explores the potential of an adipose-derived stem cell (ADSC) exosome sheet in enhancing intraoral wound healing in rats. <b>Approach:</b> An ADSC exosome sheet derived from Tisseel and rat adipose tissue (ADSC-exo) was applied to 16 rats with 6 mm full-thickness mucosal hard palate wounds. Eight wounds received ADSC-exo with a superficial occlusive dressing (ADSC-exo group), and eight received only an occlusive dressing (control group). Wound closure was monitored on days 0, 2, 4, 7, and 10, with dressings changed every 2 days. On day 10, rats were sacrificed, and wounds (<i>n</i> = 8 per group) were collected for immunohistochemical analysis. <i>In vitro</i>, four ADSC-exosome concentrations (0, 4.5 × 10¹¹, 9 × 10¹¹, and 18 × 10¹¹ exosomes/mL; <i>n</i> = 4 per group) were applied to rat oral mucosal fibroblasts to assess migration speed. <b>Results:</b> ADSC-exo accelerated wound closure (18% ± 5% vs. 35% ± 9% of initial wound area; <i>p</i> = 0.002) and fibroblast migration (for 18 × 10¹¹ exosomes/mL at 24 h: 29.7% ± 3% vs. 62.2% ± 4% of initial gap area; <i>p</i> < 0.0001) compared with the control. ADSC-exo promoted reepithelialization (87% ± 14% vs. 21% ± 6%; <i>p</i> < 0.0001), proliferation (34 ± 12 vs. 18 ± 7 Ki67+/high-power field [HPF]; <i>p</i> = 0.004), and neovascularization (28 ± 9 vs. 11 ± 5 CD31+/HPF; <i>p</i> = 0.0002) while reducing inflammation (4 ± 1 vs. 13 ± 9 CD68+/HPF; <i>p</i> < 0.0001) and increasing M2 macrophages (9.2 ± 2 vs. 4.2 ± 3 CD163+/HPF; <i>p</i> = 0.0008). ADSC-exo increased Transforming Growth Factor beta 1 (TGF-β1) (1.3 ± 0.3 vs. 0.9 ± 0.2; <i>p</i> = 0.006), Smad3 (0.9 ± 0.02 vs. 0.7 ± 0.1; <i>p</i> = 0.006), and collagen I (1.5 ± 0.9 vs. 0.5 ± 0.3; <i>p</i> = 0.005) while downregulating caspase-3 (0.7 ± 0.3 vs. 1.1 ± 0.2; <i>p</i> = 0.003) and Bax (0.9 ± 0.2 vs. 1.4 ± 0.1; <i>p</i> < 0.0001). <b>Innovation:</b> This is the first study to demonstrate the pro-wound healing effects of an ADSC exosome sheet on intraoral wounds. This paves the way for future research and clinical applications of ADSC exosomes in mucosal wound healing. <b>Conclusions:</b> Application of an ADSC-exo to rat mucosal wounds significantly improved wound healing. Mechanistically, these effects may be linked to upregulated activity of the TGF-β/Smad pathway.