The role of exosomes in peripheral nerve regeneration

Abstract

Peripheral nerve injuries remain problematic to treat, with poor functional recovery commonly observed. Injuries resulting in a nerve gap create specific difficulties for axonal regeneration. Approaches to address these difficulties include autologous nerve grafts (which are currently the gold standard treatment) and synthetic conduits, with the latter option being able to be impregnated with Schwann cells or stem cells which provide an appropriate micro-environment for neuronal regeneration to occur. Transplanting stem cells, however, infers additional risk of malignant transformation as well as manufacturing difficulties and ethical concerns, and the use of autologous nerve grafts and Schwann cells requires the sacrifice of a functioning nerve. A new approach utilizing exosomes, secreted extracellular vesicles, could avoid these complications. In this review, we summarize the current literature on exosomes, and suggest how they could help to improve axonal regeneration following peripheral nerve injury.

Keywords: Schwann cell; axonal regeneration; exosome; extracellular vesicle; microRNA; microvesicle; nerve gap; neurite outgrowth; peripheral nerve injury; stem cell.

Figure 1

The pathway to exosome biogenesis (adapted from Raposo and Stoorvogel, 2013). Exosomes originate from multi-vesicular bodies (MVBs). The MVBs can either fuse with the lysosome for degradation or with the plasma membrane, thereby releasing exosomes into the extracellular space where they mediate cell-to-cell communication.