Abstract
Functional recovery is usually poor following peripheral nerve injury when reinnervation is delayed. Early innervation by sensory nerve has been indicated to prevent atrophy of the denervated muscle. It is hypothesized that early protection with sensory axons is adequate to improve functional recovery of skeletal muscle following prolonged denervation of mixed nerve injury. In this study, four groups of rats received surgical denervation of the tibial nerve. The proximal and distal stumps of the tibial nerve were ligated in all animals except for those in the immediate repair group. The experimental groups underwent denervation with nerve protection of peroneal nerve (mixed protection) or sural nerve (sensory protection). The experimental and unprotected groups had a stage II surgery in which the trimmed proximal and distal tibial nerve stumps were sutured together. After 3 months of recovery, electrophysiological, histological and morphometric parameters were assessed. It was detected that the significant muscle atrophy and a good preserved structure of the muscle were observed in the unprotected and protective experimental groups, respectively. Significantly fewer numbers of regenerated myelinated axons were observed in the sensory-protected group. Enhanced recovery in the mixed protection group was indicated by the results of the muscle contraction force tests, regenerated myelinated fiber, and the results of the histological analysis. Our results suggest that early axons protection by mixed nerve may complement sensory axons which are required for promoting functional recovery of the denervated muscle natively innervated by mixed nerve.
Highlights
Peripheral nerve injury usually results in poor functional recovery, especially when nerve repair is delayed or injury is at proximal point[1].The suboptimal outcome can be attributed to degeneration of the distal nerve stump and atrophy of chronically denervated muscle [2,3]
The goal of this study was to investigate whether sensory nerve protection is sufficient to improve functional recovery of target muscles following delayed denervation of mixed nerve injury
The locomotor function of the operated limb was restored gradually, recovery was greater for rats which had undergone nerve protection
Summary
Peripheral nerve injury usually results in poor functional recovery, especially when nerve repair is delayed or injury is at proximal point[1].The suboptimal outcome can be attributed to degeneration of the distal nerve stump and atrophy of chronically denervated muscle [2,3]. When repair surgery is delayed, recovery is often incomplete, along with weakness and wasting [4].The capacity of motoneurons to regenerate axons into the distal segments is compromised due to prolonged denervation [5]. Even if the regenerating axons reach the neuromuscular junction, the function cannot be restored because of the inability of these targets to accept reinnervation [7]. Many regenerated axons fail to reach the denervated targets for months and even years in spite of immediate repair [8]
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