New procedure repairs severed nerves in minutes, restoring limb use in days or weeks

February 3, 2012, Wiley

American scientists believe a new procedure to repair severed nerves could result in patients recovering in days or weeks, rather than months or years. The team used a cellular mechanism similar to that used by many invertebrates to repair damage to nerve axons. Their results are published today in the Journal of Neuroscience Research.

"We have developed a procedure which can repair severed nerves within minutes so that the behavior they control can be partially restored within days and often largely restored within two to four weeks," said Professor George Bittner from the University of Texas. "If further developed in this approach would be a great advance on current procedures that usually imperfectly restore lost function within months at best."

The team studied the mechanisms all use to repair damage to their membranes and focused on invertebrates, which have a superior ability to regenerate nerve axons compared to . An axon is a long extension arising from a nerve cell body that communicates with other or with muscles.

This research success arises from Bittner's discovery that nerve axons of invertebrates which have been severed from their cell body do not degenerate within days, as happens with mammals, but can survive for months, or even years.

The severed proximal nerve axon in can also reconnect with its surviving distal nerve axon to produce much quicker and much better restoration of behaviour than occurs in mammals.

"Severed invertebrate nerve axons can reconnect proximal and distal ends of severed nerve axons within seven days, allowing a rate of behavioural recovery that is far superior to mammals," said Bittner. "In mammals the severed distal axonal stump degenerates within three days and it can take nerve growths from proximal axonal stumps months or years to regenerate and restore use of muscles or sensory areas, often with less accuracy and with much less function being restored."

The team described their success in applying this process to rats in two research papers published today. The team were able to repair severed sciatic nerves in the upper thigh, with results showing the rats were able to use their limb within a week and had much function restored within 2 to 4 weeks, in some cases to almost full function.

"We used rats as an experimental model to demonstrate how severed nerve axons can be repaired. Without our procedure, the return of nearly full function rarely comes close to happening," said Bittner. "The sciatic nerve controls all muscle movement of the leg of all mammals and this new approach to repairing could almost-certainly be just as successful in humans."

To explore the long term implications and medical uses of this procedure, MD's and other scientist- collaborators at Harvard Medical School and Vanderbilt Medical School and Hospitals are conducting studies to obtain approval to begin clinical trials.

"We believe this procedure could produce a transformational change in the way injuries are repaired," concluded Bittner.

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5 / 5 (5) Feb 03, 2012
Something has been cut. The abstract explains the missing procedure:
"severed axonal ends are opened and resealing is prevented by hypotonic Ca free saline containing antioxidants (especially methylene blue) that inhibit plasmalemmal sealing in sciatic nerves. Second, a hypotonic solution of polyethylene glycol (PEG) is applied to open closely apposed (by microsutures, if cut) axonal ends to induce their membranes to ow rapidly into each other .."
Rapid, Effective, and Long-Lasting Behavioral Recovery Produced by Microsutures, Methylene Blue, and Polyethylene Glycol After Completely Cutting Rat Sciatic Nerves
G.D. Bittner, et al Journal of Neuroscience Research Early View publication
not rated yet Feb 03, 2012
Thanks, Squirrl, for the missing details.

Very promising intervention. I wonder if these procedures are applicable to severed spinal nerves?
not rated yet Feb 03, 2012
Sounds like a job for some sort of biochemical crimp on connector.
not rated yet Feb 03, 2012
Manually splicing individual axons one at a time isn't going to be a viable procedure for a good while, i'd've thought. For now, it may be a case of something's better than nothing, but isn't going to be practical for restoring full sensory and motor control in severe injuries like a re-attached limb or major nerve bundle... or am i being too cynical? Cool advance all the same, i've read before about how protein transport continues along severed axons causing jams and ultimately plaque development followed by necrosis. Re-attaching them is the only way to keep them viable - there's no artificial means to take over the cell's role in controlling the protein transport mechanism that might otherwise allow prosthetic neural integration - hence current alternatives must directly stimulate the muscles with electrodes. Being able to fix axons immediately is almost the silver bullet... if it can be implemented en masse anyway...
5 / 5 (1) Feb 03, 2012
but isn't going to be practical for restoring full sensory and motor control in severe injuries like a re-attached limb or major nerve bundle

That's already being done. Though the procedure is more akin to doing fine sutures and then letting the nerves regrow/reattach themselves (axons can grow at about a millimeter per month or so)

The drawback is that you will not get the same reattachment scheme as before - so you have to relearn the use of the limb and relearn to interpret the sensory data. With the conflicting (old) scheme represented in your brain up until the accident this usually leads to somewhat impaired performance.
not rated yet Feb 03, 2012
Ah i see, thanks. Wow so notwithstanding a degree of plasticity, this is quite a promising breakthrough then...
not rated yet Feb 03, 2012
Yes. Especially for spinal injuries this could be a real breakthrough. I hope they get this to Phase 1 trials soon.

Though what works in mice doesn't always work in humans. We'll just have to wait and see.
not rated yet Feb 04, 2012
Being able to fix axons immediately is almost the silver bullet... if it can be implemented en masse anyway...

A fibrous scaffolding (spider silk?) impregnated with each of the two chemicals at either end. Simply laid across the gap between the severed ends.

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