Exosomes carrying adipose mesenchymal stem cells function alleviate scleroderma skin fibrosis by inhibiting the TGF-β1/Smad3 axis

Systemic sclerosis (SSc) is a connective tissue disease characterized by progressive fibrosis of the skin and visceral organs, to date, skin fibrosis remains a clinical therapeutic challenge. Adipose-derived mesenchymal stem cells (AMSCs) have been considered extremely promising for the treatment of SSc, and the biological effects of MSCs are partly attributed to the secretion of exosomes (exos). Our aim was to determine whether exosomes derived from AMSCs have parental biological effects to AMSCs in the therapy of SSc skin fibrosis. In vitro cellular experiments, AMSCs and SSc skin fibroblasts were cocultured in direct contact and transwell indirect contact at a ratio of 1:5 and 1:10, respectively, then exosomes were extracted from the cell culture supernatant of AMSCs and identified, and the exosomes were cocultured with fibroblasts to investigate the effects of AMSCs and exosomes on fibroblast collagen synthesis. Repeated subcutaneous injections of bleomycin (BLM) to construct a model of SSc skin fibrosis in vivo experiments, then AMSCs and exosomes were injected subcutaneously to investigate their effects on skin fibrosis in the BLM mice. The results revealed that exosomes had similar biological functions to AMSCs, by inhibiting the TGF-β1/Smad3 axis, which alleviated collagen synthesis in skin fibroblasts from SSc patients and skin fibrosis in BLM models. In conclusion, AMSCs-derived exosomes may be "rising star candidates" for the treatment of SSc skin fibrosis.