Quote Originally Posted by paolocipolla View Post
One aspect that could be very important is what signals from the injured axon (injury site) get to the cell body. It seems that in the PNS you have different signals than in the CNS traveling to the cell body that cause a cascade of events that result in regneration of the axon. It is probably more complex than this, but that seems a possible part of the problem..
Quote Originally Posted by Nowhere Man View Post
I agree. I also think those signals would be vital to guiding a regenerated axon, because they have no idea where to go. It just goes to show how highly complex a problem like SCI truly is, and how far away an effective treatment really is. People need to stop looking at the finish line and start looking at the starting gate.
You bring up a good point Paolo. Even that I would consider an environmental factor...if a signal can travel down an un-interrupted CNS axon to a lower motor neuron, then that neuron is told to fire over and over and over again - if the injury to the peripheral nerve isn't too severe, then astrocytes keep detecting an electrical charge sent out from the neuron, myelin is produced, the axon regenerates, and function is restored.
If, however, there is a disruption to the CNS (lack of myelin secondary to an SCI, for instance), then a signal might never travel far enough to get astrocytes that survived the injury to signal for more myelin production, therefore not creating a path for axons that are capable of regenerating.

Nowhere Man, while we haven't been presented with a scenario yet where we can test if the correct signals can guide regenerating axons, we do know that incomplete some incomplete SCIs can vastly improve their gross motor abilities (walking speed and skill) without any change in ASIA scores. The CNS is capable of robust re-organization after an injury - hopefully the same principles that have been documented so far will still apply to successful regenerative techniques once they are discovered.