Regeneration into protected and chronically denervated peripheral nerve stumps.
OBJECTIVE
Delayed repair of peripheral nerve injuries often results in poor motor functional recovery. This may be a result of the deterioration or loss of endoneurial pathways in the distal nerve stump before motor axons can regenerate into the stump.


METHODS
Using the rat femoral nerve, we protected distal endoneurial pathways of the saphenous nerve with either cross-suture of the quadriceps motor nerve (Group A) or resuture of the saphenous nerve (Group B) to compare later motor regeneration into the "protected" saphenous nerve pathway to chronic denervation and "unprotected" saphenous nerve (Group C). A total of 60 rats, 20 per group, were operated on. After this protection (or lack thereof) for 8 weeks, the motor branch of the femoral nerve was cut and sutured to the distal saphenous nerve to allow motor regeneration into protected and unprotected saphenous nerve stumps. The quantitative assessment of axonal regeneration was performed after 6 weeks by use of nerve sampling for axon counts and retrogradely labeled motor neuron counts.


RESULTS
Significantly more myelinated axons innervated the motor (A) than the sensory (B) and no-protection (C) groups. There were significantly more retrogradely labeled femoral motor neurons in Group A than in the unprotected group (C).


CONCLUSIONS
We conclude that even 2 months of denervation of the distal nerve pathway is deleterious to regeneration and that protection of the pathway improves subsequent reinnervation and regeneration. Moreover, if the desired regeneration is motor, protection of the distal nerve pathway by a motor nerve conditions is better than a sensory nerve.
Midha
Rajiv
R
Division of Neurosurgery, Department of Clinical Neurosciences, and Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada. rajmidha@ucalgary.ca
Munro
Catherine A
CA
Chan
Steven
S
Nitising
Akkapong
A
Xu
Qing-Gui
QG
Gordon
Tessa
T
D000818:Animals; D001369:Axons / Q000502:physiology; D003714:Denervation; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology*; D051381:Rats; D011917:Rats, Inbred Lew; D013997:Time Factors