Adipose-derived stem cell exosomes rescue senescence-induced impairment of migration in epidermal keratinocytes and dermal fibroblasts

Wound healing is a process which occurs in response to skin injury, in four tightly regulated but overlapping phases: haemostasis, inflammation, proliferation and remodeling. During the proliferative phase, keratinocytes and fibroblasts migrate into the wound bed to repair and close the wound. However, the wound healing process can be disrupted by various events such as prolonged inflammation, impaired proliferation, as well as senescence, leading to the formation of a chronic wound. Using hydrogen peroxide and the NMNPT inhibitor FK866 to induce senescence in vitro, we show that senescent cells have impaired migratory capabilities. Furthermore, senescent fibroblasts express elevated levels of the gap junction protein Connexin 43, which is known to accumulate at the wound edge of non-healing ulcers. Using chronic wound tissue samples from patients, we show that wound tissues contain a higher number of senescent cells, with elevated levels of Cx43. We rescued the senescence-induced impairment of migration using exosomes derived from adipose derived stem cells. Using mass-spectrometry proteomics and gene ontology enrichment analysis, we show that exosomal proteins are largely associated with cell adhesion molecule binding functions, and that senescent keratinocytes express elevated levels of Integrins and Cadherins. We demonstrate the potential of exosomes as a wound healing therapeutic by using an in-house model of perturbed wound healing in Sprague Dawley rats. Our results show that senescent cells have impaired migratory capabilities with elevated levels of gap junction and adhesion proteins. The impairment of migration is attenuated by exosomes, and demonstrate the potential of exosomes as a wound healing therapeutic.