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 clinical trials 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 animal cells use to repair damage to
their membranes and focused on invertebrates, which have a superior
ability to regenerate nerve axons compared to mammals. An axon is a long
extension arising from a nerve cell body that communicates with other
nerve cells 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 invertebrates 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 nerve axons 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 nerve injuries are repaired," concluded Bittner.
Cellular mechanisms of plasmalemmal sealing and axonal repair by polyethylene glycol and methylene blueWiley-Blackwell
