Optic Nerve Regeneration: the Future (Principles; Explanation, of How It Works and Areas of Research Including Electrical Stimulation) (PDF)

In mammals, axon regeneration after injury is the rule for the peripheral nervous system (PNS) but the exception when it comes to the central nervous system (CNS). The limited regenerative capacity of the CNS was thought to be cell intrinsic until experiments demonstrated that CNS axons readily grow into peripheral nerve grafts. 1These landmark studies demonstrated that extrinsic environmental factors can override intrinsic limitations to regeneration in the CNS.These early studies fueled investigations to identify growth-permissive molecules within the PNS and growth-inhibitory molecules within the CNS, with the hope that manipulating their relative levels would unlock the regenerative capacity of the CNS.