The peripheral nervous system--central nervous system regeneration dichotomy: a role for glial cell transplantation.

The events that follow axonal interruption (axotomy) reveal an important and fundamental difference between the peripheral and central components of the adult mammalian nervous system. Following transection of peripheral nerve axons, the proximal axonal portion is able to regenerate through the distal part of the nerve and may, under appropriate conditions, re-innervate the original target (sensory or effector organ), thereby restoring pre-lesion anatomy and function (Guth, 1956). Within the central nervous system (CNS), however, the regenerative response of interrupted axons is, with few exceptions, abortive, and the restoration of original synaptic contact does not occur (Cajal, 1928). This difference in the response to injury has clinical implications, CNS trauma carrying a much poorer prognosis than injury to peripheral nerves. This commentary will briefly review the possible reasons for the failure of effective axon regeneration in the CNS, and discusses the potential of glial transplantation to shed light on this complex problem.