M. Kawabuchi et al., The effect of aging on the morphological nerve changes during muscle reinnervation after nerve crush, REST NEUROL, 13(3-4), 1998, pp. 117-127
The extent of the muscle endplate reinnervation that followed crush injury
of the sciatic nerve was compared between young adult (4 and 5 months old)
and aged (24 months old) animals. The time course of regeneration in the mu
scular nerve bundle, its ramification, and the nerve terminal was immunohis
tochemically estimated using an antibody against the neuron specific enolas
e (NSE), a neuronal marker. During early phases of regeneration (7, 21 and
28 days post-crush) in the young adult animal, there were tortuosity, vacuo
lation and/or unfasciculation in the nerve bundle and its ramification, alo
ng with immature nerve terminals and multiple innervation. Following a subs
equent advancement in reinnervation to the denervated motor endplates, the
adult type of single motor innervation was common on the day 56,
The old muscles basically followed the course of reversible axotomy alike t
he young adult ones. The age difference accounted for as follows: a reduced
rate of reinnervation as indicated by a greater frequency of abnormal nerv
e bundles and immature nerve terminals at 28 days and 56 days post-crush, a
s well as unusual pathways or striking tortuosity represented by the NSE-la
beled processes between day 7 and 56; late in the reinnervation period, abn
ormal regeneration characterized by damage of the nerve bundle, and poorly
developed terminal architectures. These results suggest that despite the ca
pability of the nerve from the old animals to extend its process, re-establ
ishment of normal single motor innervation is reduced due to some age-relat
ed deficits, which may be related to the impaired Schwann cell-axon interac
tions.