Motor neurons, which have processes that reside in both the central nervous system (CNS) and the peripheral nervous system (PNS), have a unique ability to regenerate following injury. Unlike most other CNS neurons, motor neurons are capable of regenerating their axons, even in the absence of intervention.
Regeneration in the PNS vs. CNS
The PNS is generally more permissive to axon regeneration compared to the CNS. Peripheral nerve injuries often result in successful axon regrowth and functional recovery, while CNS neurons typically fail to regenerate their axons after injury. This difference is due to a variety of extrinsic and intrinsic factors that inhibit regeneration in the CNS environment.
Motor Neuron Regeneration
Motor neurons, which have cell bodies in the CNS but project their axons into the PNS, are one of the few exceptions to the general lack of regeneration in the CNS. Following axotomy (severing of the axon), motor neurons have been observed to upregulate a set of “regeneration-associated genes” (RAGs) that promote axon regrowth. This intrinsic regenerative capacity of motor neurons allows them to regenerate their axons, even in the absence of external intervention.
However, the regenerative ability of motor neurons is not unlimited. While they can regrow their axons to some degree, the treatment was found to reduce the number of regenerated axons to approximately one-third compared to untreated controls.