"Bad regenerators" die after spinal cord injury: insights from lampreys.

Abstract

In mammalian species, including humans, spinal cord injury (SCI) leads to permanent disability. A major cause of disability after SCI is the failure of axotomized descending axons to regenerate across the trauma zone and to reconnect to they appropriate targets distal to the site of injury. Currently, major research efforts are devoted to find new ways of promoting the regrowth of damaged descending axons. However, activation of axonal regrowth will depend on the survival of the axotomized descending brain neurons. This will be especially important in chronically injured patients. Neuronal degeneration can be a slow and delayed process, so descending neurons of long-term injured patients would have more time to degenerate after the injury making it more difficult to activate regenerative processes. If descending neurons of the brain die after the damage to the axon in the spinal cord, regenerative therapies in long-term injured patients will fail. There is then a need to prevent the retrograde degeneration of axotomized brain neurons after SCI if we want to promote axonal regeneration. It may be necessary to protect from retrograde degeneration very early after the injury if we then want to enhance axonal regeneration later on.