Embryonic neurons transplanted into the tibial nerve reinnervate muscle and reduce atrophy but NCAM expression persists.
OBJECTIVE
The aim of this study was to use the glycogen depletion technique to determine whether reinnervated muscle fibers could be distinguished from denervated muscle fibers by their size or by neural cell adhesion molecule (NCAM) expression.


METHODS
Medial gastrocnemius muscles of five adult Fischer rats were reinnervated from embryonic neurons transplanted into the distal stump of the tibial nerve. Ten weeks later, the transplants were stimulated repeatedly to deplete reinnervated muscle fibers of glycogen. Areas of reinnervated (glycogen-depleted) muscle fibers were measured and assessed for NCAM expression. The areas of muscle fibers from reinnervated, denervated (n=5) and unoperated control muscles (n=5) were compared.


RESULTS
Mean reinnervated muscle fiber area was significantly larger than the mean for denervated fibers (mean +/- SE: 40 +/- 6 and 10 +/- 1% of unoperated control fibers, respectively). NCAM was expressed in 55 +/- 7% of reinnervated fibers (mean +/- SE; range: 42-77%). The mean areas of reinnervated fibers that did or did not express NCAM were similar. NCAM was only expressed in some fibers in completely denervated muscles.


CONCLUSIONS
Our data show that NCAM expression does not differentiate muscle denervation or reinnervation. Quantifying the area of large fibers did distinguish reinnervated muscle fibers from denervated fibers and showed that reinnervation of muscle from neurons placed in peripheral nerve is a strategy to rescue muscle from atrophy.
Grumbles
Robert M
RM
The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, Lois Pope LIFE Center, 1095 NW 14th Terrace (R48), Miami, FL 33136, USA.
Almeida
Vania W
VW
Thomas
Christine K
CK
D000704:Analysis of Variance; D000818:Animals; D017690:Cell Transplantation / Q000379:methods*; D004576:Electromyography; D004622:Embryo, Mammalian; D005260:Female; D006003:Glycogen / Q000172:deficiency; D009121:Muscle Denervation / Q000379:methods; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D009133:Muscular Atrophy / Q000209:etiology / Q000378:metabolism / Q000601:surgery*; D009416:Nerve Regeneration / Q000502:physiology*; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D013116:Spinal Cord / Q000166:cytology / Q000196:embryology; D013979:Tibial Nerve / Q000502:physiology*
D019006:Neural Cell Adhesion Molecules; D006003:Glycogen