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

Abstract

Background Mesenchymal stem cell (MSC) -derived exosomes, especially adipose-derived mesenchymal stem cell exosomes (ADSC-Exos), have emerged as a promising alternative for skin damage repair with anti-inflammatory, angiogenic and cell proliferation effects while overcoming some of the limitations of MSC. However, the mechanism by which ADSC-Exos regulates inflammatory cells during wound healing remains unclear. This study investigated how ADSC-Exos regulate macrophages to promote wound healing. Methods ADSC-Exos were isolated using ultracentrifugation, with subsequent quantification of exosomes 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. RNA sequencing was performed to identify differentially expressed genes affected by ADSC-Exos. 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 inhibited the expression of TNF-α and IL-6, induced M2 macrophage polarization, promoted collagen deposition and angiogenesis, and accelerated wound healing. RNA sequencing identified IL-33 as a key mediator in this process. In Il33−/− mice, impaired wound healing and decreased M2 macrophage polarization were observed. The co-culture experiments showed that IL-33 enhanced keratinocyte function through activation of the Wnt/β-catenin signaling pathway. These findings highlight the therapeutic potential of ADSC-Exos in wound healing by modulating IL-33. 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/β-catenin

1. Introduction

As the body’s largest organ, the skin serves as a critical barrier against environmental aggressors. However, its constant exposure makes it highly susceptible to damage. Wound healing in the skin is a complex and dynamic biological process involving intricate interactions between various cell types, extracellular matrix (ECM) remodeling and angiogenesis [1]. Accelerating this process is vital to alleviating patient discomfort and reducing the associated medical and social burdens. Despite significant advances in treatment strategies, finding effective solutions to promote rapid and efficient wound healing remains a challenge [2].

Mesenchymal stem cells (MSCs) have great potential in regenerative medicine due to their ability to proliferate, differentiate and regulate immune responses [3–5]. Among MSCs, adipose-derived stem cells (ADSCs) are favoured due to their abundance, ease of derivation and ability to self-renew [6]. However, stem cell therapy is limited by low efficacy, immune rejection and the risk of tumour formation [7–9]. The therapeutic effects of MSCs are largely attributed to their paracrine activity, of which exosomes are a key component. These nano-sized vesicles contain proteins, lipids and nucleic acids that regulate cell behaviour and intercellular communication. Compared to MSCs, exosomes are more stable, less immunogenic and have a lower risk of tumourigenesis, making them a promising alternative. Exosomes have shown therapeutic potential in several models of skin injury [10–14]. For example, exosomes from nrf2-overexpressed ADSCs accelerate angiogenesis and wound healing in diabetic foot ulcers [15], while MSC-derived exosomes reduce inflammation in psoriasis by down-regulating IL-17 and C5b-9 [16]. In atopic dermatitis, ADSC-Exos inhibit inflammatory cytokines such as IL-4 and TNF-α, thereby improving symptoms [17, 18]. These findings highlight the advantages of exosome-based therapies over traditional MSC approaches in regenerative medicine.