Figure 3.

Peripheral nerve regeneration. A) Natural regeneration in a hollow conduit undergoes 5 phases: 1) Fluid phase: fibrinogen and other blood proteins infiltrate the nerve gap and the area become rich in protein and neurotropic factors. 2) Fibrin cable phase: fibrinogen in the presence of thrombin forms fibrin, which creates a matrix bridging the distal and proximal stumps. 3) Cell migration phase: Pro-regenerative Schwann cells infiltrate the gap and secrete trophic factors and form bands of Büngner. 4) Axonal phase: Axons extend along fibrin cables. 5) Myelination phase: Schwann cells re-myelinate axons. B) The role of each extracellular matrix (ECM) component in regeneration. Following nerve transection injury, glycosaminoglycans form a hydrogel network to support cell migration, while Schwann cells attach to the ECM network. Next, fibronectin enhances Schwann cell migration into the nerve. Finally, laminin regulates bands of Büngner formation and Schwann cell maturation, which guides axonal regeneration.