This study shows that irrespective of how long an axon has been without myelin, it can "take" myelin growth... now if we can only figure out a way to get the myelin to grow in the first place...

"An important question relevant to developing remyelination therapies is whether axons that remain without myelin sheaths after an episode of demyelination retain myelination competence...

...The extent of myelination achieved following transplantation of OPCs is the same in young adult recipients (2 months old) as that which occurs in old adult recipients (12-18 months old), indicating that there are no changes in axons remaining unmyelinated for many months that would prevent effective remyelination. This finding suggests that chronically demyelinated regions of axons such as those in seen in multiple sclerosis are likely to remain competent to be remyelinated."

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Full Article Text

CNS axons retain their competence for myelination throughout life.

Setzu A, Ffrench-Constant C, Franklin RJ.

Cambridge Centre for Brain Repair and Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.

An important question relevant to developing remyelination therapies is whether axons that remain without myelin sheaths after an episode of demyelination retain myelination competence. To resolve this, we have developed a model of transplantation into the nerve fibre layer of the adult rat retina, where the axons are unmyelinated. In the adult, these axons can be myelinated by transplantation of both the oligodendrocyte progenitor cells (OPCs) and an OPC line (CG4). The extent of myelination achieved following transplantation of OPCs is the same in young adult recipients (2 months old) as that which occurs in old adult recipients (12-18 months old), indicating that there are no changes in axons remaining unmyelinated for many months that would prevent effective remyelination. This finding suggests that chronically demyelinated regions of axons such as those in seen in multiple sclerosis are likely to remain competent to be remyelinated. Copyright 2003 Wiley-Liss, Inc.

PMID: 14730704 [PubMed - in process]