Abstract
The peripheral nervous system may play an important role in normal bone maintenance and remodeling. Substance P (SP) is a neuropeptide associated with bone loss and formation that may mediate the effects of the nervous system. The purpose of this study is to determine if treadmill running combined with electro-acupuncture at Jiaji acupoints (Jiaji-EA) affects tibial bone mass and SP expression in rabbits with sciatic nerve injury. Twenty-four juvenile male New Zealand white rabbits were randomly assigned to one of 4 groups: sham injury control (sham), sciatic never crush control (SNCr), treadmill running (treadmill), and Jiaji-EA combined with treadmill running (ET group). The SNCr, treadmill, and ET groups all had an induced sciatic never crush injury of approximately 2mm. Control groups received no intervention; the treadmill and ET groups were trained by treadmill; the ET group also received Jiaji-EA. After the 4 weeks of treatment, toe-spreading index (TSI), BMD, bone strength, and SP expression in the tibia were significantly lower in the nerve injury groups (SNCr, treadmill, and ET) compared to the sham groups (p<0.05). Treatment (treadmill and ET groups) increased all measures compared to the SNCr group (p<0.05). Further, TSI, BMD, bone strength, and SP expression in the ET group were higher than the treadmill group (p<0.05). Our results indicate that treadmill therapy combined with electro-acupuncture at Jiaji acupoints prevents bone loss in rabbit tibias after sciatic nerve injury. This may occur in two ways: indirectly in association with axon regeneration and directly via loading on the bone mediated through increased SP expression. This study provides important evidence for the clinical treatment of bone loss after peripheral nerve injury.
Highlights
Injuries to peripheral nerves differ from injuries to most other tissue types because further neuron and target organ degeneration often follows [1]
We found that toe-spreading index (TSI), Bone Mineral Density (BMD), bone strength, and Substance P (SP) expression in the tibia are reduced after sciatic nerves injury
BMD and bone strength of tibia in the treadmill group were significantly higher compared to the sciatic never crush control (SNCr) group but still significantly lower than the sham control, indicating decreases in load baring play a part but are not solely responsible for bone loss
Summary
Injuries to peripheral nerves differ from injuries to most other tissue types because further neuron and target organ degeneration often follows [1]. The peripheral nervous system (PNS) has an innate capacity to regrow to their targets, including muscle, bone, and skin. The peripheral nervous system may play an important role in bone healing following fracture or other trauma [4,5,6]. Bone fractures accompanied by peripheral nerve injuries heal slower [7] and sensory denervation negatively affects long-term prognosis[8]. Studies suggest that the absence of SP reduces bone formation rate associated with fracture healing [10,11]
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