Fig 1.

Distal nerve segment post-nerve injury. A motor neuron (left) innervates muscle tissue (right) via an axon myelinated by Schwann cells (center). After sustaining an injury, the distal nerve segment will degenerate into amorphous debris. Hematogenous macrophages (green) are recruited from circulation and enter the distal stump. Macrophages make the microenvironment more permissive for axonal regeneration by clearing cellular debris and releasing cytokines and neurotrophic factors. Axons regenerate with the guidance of Schwann cells and the aid of macrophages that release neurotrophic factors and eliminate debris that poses a physical barrier and releases inhibitory signaling to the regenerating axon