Exosomes from adipose stem cells accelerate wound healing by increasing the release of IL-33 from macrophages

Background: Mesenchymal stem cells (MSCs) have been widely used to repair skin injuries due to their remarkable properties, including anti-inflammatory, angiogenic and cell proliferative effects. However, MSCs also have notable drawbacks and limitations. Exosomes, the paracrine products of MSCs, have emerged as a promising alternative in tissue repair. Among these, adipose-derived mesenchymal stem cell exosomes (ADSC-Exos) offer distinct advantages such as easy accessibility, high stability and convenient storage. The role of ADSC-Exos in promoting wound healing has been increasingly recognised. However, the mechanisms by which ADSC-Exos facilitate the healing process by modulating inflammatory cells remain unclear. This study aims to investigate the mechanisms by which ADSC-Exos regulate macrophages to enhance wound healing.Methods: ADSC-Exos were isolated using ultracentrifugation, with subsequent quantification of protein concentration and exosome particle number. To investigate their role in wound healing, the effects of ADSC-Exos on inflammation, angiogenesis, collagen deposition, and macrophage polarization were evaluated through immunohistochemical staining, immunofluorescence, and Western blotting. Changes in gene expression associated with ADSC-Exos-induced macrophage polarization were analyzed using qPCR, and RNA sequencing was performed to identify differentially expressed genes. The critical role of IL-33 in the wound healing process was further confirmed using Il33-/- mice. Additionally, co-culture experiments were conducted to explore the effects of IL-33 on keratinocyte proliferation, collagen deposition, and epithelialization.Results: ADSC-Exos promoted wound healing by suppressing TNF-alpha and IL-6 expression, inducing M2 macrophage polarization and enhancing collagen deposition and angiogenesis. RNA sequencing identified IL-33 as a key mediator in this process. Studies in Il33-/- mice revealed impaired wound healing and macrophage polarisation, while co-culture experiments showed that IL-33 improved keratinocyte function through activation of Wnt/beta-catenin signalling. These findings suggest that ADSC-Exos are a promising therapeutic approach for wound healing through IL-33 regulation.Conclusions: ADSC-Exos promote wound healing by regulating macrophage polarization and enhancing IL-33 release, which drives keratinocyte proliferation, collagen deposition, and epithelialization via the Wnt/beta-catenin signaling pathway. These findings provide a mechanistic basis for the therapeutic potential of ADSC-Exos in tissue repair and regeneration.