Exosomes as a Promising Therapeutic Strategy for Peripheral Nerve Injury

Peripheral nerve injury has a high incidence and often leads to severe losses of sensory and motor functions in the afflicted limb. Autologous nerve grafts are widely accepted as the gold standard for peripheral nerve repair, but the presence of inherent drawbacks dramatically reduces their usability. Numerous tissue engineering nerve grafts are developed as alternatives to autologous nerve grafts, and a variety of cells and neurotrophic factors are introduced into these grafts for improvement. However, they are still difficult to obtain satisfactory clinical results. Peripheral nerve regeneration following injury remains a significant challenge for researchers and clinicians. Exosomes are extracellular membranous nanovesicles that are secreted by most cells. As the key players of intercellular communication, exosomes play a fundamental role in the physiological and pathological processes of the nervous system. Accumulating evidence has suggested that exosomes can exert neurotherapeutic effects via mediating axonal regrowth, Schwann cell activation, vascular regeneration, and inflammatory regulation. Exosomes are emerging as a promising approach for treating peripheral nerve injury. Furthermore, they also provide possibilities for enhancing the repairing capacity of various nerve grafts. This review primarily highlights the regenerative effects of exosomes on peripheral nerve injury. The exosomes from distinct sources reported so far in the literature are summarized to understand their roles in the process of nerve repair. Moreover, the challenges that must be addressed in their clinical transformation are outlined as well. This review also provides further insight into the potential application of exosomes for peripheral nerve repair.