In adult mammals, peripheral nervous system (PNS) neurons regenerate relatively efficiently, whereas central nervous system (CNS) neurons cannot regenerate. The difference in regenerative capacity between CNS and PNS neurons has been attributed to extrinsic signals, and to intrinsic growth ability and the inhibitory glial environment. PNS neurons possess the fundamental and conserved ability to regenerate their axons following injury, in a process mainly controlled by the PNS glial cells surrounding neurons and Schwann cells (SCs). Several studies have reported the regenerative ability of SCs. After axotomy, SCs undergo a rapid reprogramming process that includes macrophage activation and morphological transformation from de-differentiating into non-myelinating repair cells that provide the signals and cues necessary for recovery of injured neurons, axon regeneration, and reinnervation. Although these complex intrinsic and extrinsic processes can restore damaged neurons, the SC repair system is efficacious only for injuries less than 3 cm in size. To achieve functional recovery, patient age and delays in repair after axotomy must be fully considered. Recent studies have confirmed that SCs are a remarkable cell regeneration resource; however, little is known regarding the molecular mechanism underlying spontaneous axon regeneration. More advanced strategies are required before SCs can be applied for complete restoration of damaged neurons.
Immunotherapy | Open Access