Journal of Neuroscience, Vol 7, 2145-2152, Copyright © 1987 by Society for Neuroscience
Transient and chronic neonatal denervation of murine muscle: a procedure to modify the phenotypic expression of muscular dystrophy
MC Moschella and M Ontell
The extensor digitorum longus muscles of 14-d-old normal (129 ReJ ++) and
dystrophic (129 ReJ dy/dy) mice were denervated by cutting the sciatic
nerve. One denervation protocol was designed to inhibit reinnervation of
the shank muscles, the other to promote reinnervation. Chronically
denervated muscles (muscles that remained denervated for 100 d after nerve
section) exhibited marked atrophy, but the number of myofibers in these
muscles (1066 +/- 46 and 931 +/- 62 for the denervated normal and
dystrophic muscles, respectively) was similar to the number of myofibers
found in age-matched, unoperated normal muscles [922 +/- 28 (Ontell et al.,
1984)] and was significantly greater than the number of myofibers found in
age-matched dystrophic muscles [547 +/- 45 (Ontell et al., 1984)]. Similar
effects on myofiber number were obtained when denervated muscles were
allowed to reinnervate. Reinnervation of both normal and dystrophic muscles
mitigated the marked atrophy that characterized chronically denervated
muscles. The dystrophic reinnervated muscles appeared "healthier" than
age-matched, unoperated dystrophic muscles, having 70% more myofibers, less
myofiber diameter variability, substantially less connective tissue
infiltration, and a greater amount of contractile tissue at their widest
girths. The present study demonstrated that it is possible to alter the
phenotypic expression of the histopathological changes associated with
murine dystrophy, in dystrophic myofibers that are formed during fetal
development, by subjecting the muscle to neonatal denervation.