Extracellular vesicles from human hepatic progenitor cells accelerate deep frostbite wound healing by promoting fibroblasts proliferation and inhibiting apoptosis

Frostbites are cold tissue damages frequently observed at high altitudes and under extremely cold conditions. Though their incidence rate is low, the resulting impact in affected patients can be very serious, often leading to amputations. Clinical management and the prediction of outcome can be of utmost importance to frostbite patients. A possible use of stem cell-derived extracellular vesicles (EVs) has been suggested for cutaneous wound healing and we, therefore, tested their use for the treatment of deep frostbite wound. To this end, the impacts of hHPC-derived EVs were evaluated in an in vivo animal model comprising of Kunming female mice as well as studied in vitro for the mechanism. We first characterized the EVs and these hHPC-derived EVs, when applied to treat frostbite wounds, accelerated wound healing in the in vivo animal model, as assessed by wound closure, re-epithelization thickness, collagen density and the expression of Collagen I and α-SMA. The proliferation and migration of human skin fibroblasts was also found to be increased by EVs in the in vitro experiments. The H2O2-induced apoptosis cell model, established to simulate the post-frostbite injury, was inhibited by EVs, with concomitant increase in the expression of Bcl-2 and decreased expression of Bax, further confirming the findings. Our novel results indicate that the application of EVs might be a promising strategy for deep frostbite wound healing.