Abstract
The development of noninvasive approaches to facilitate the regeneration of post-traumatic nerve injury is important for clinical rehabilitation. In this study, we investigated the effective dose of noninvasive 808-nm low-level laser therapy (LLLT) on sciatic nerve crush rat injury model. Thirty-six male Sprague Dawley rats were divided into 6 experimental groups: a normal group with or without 808-nm LLLT at 8 J/cm2 and a sciatic nerve crush injury group with or without 808-nm LLLT at 3, 8 or 15 J/cm2. Rats were given consecutive transcutaneous LLLT at the crush site and sacrificed 20 days after the crush injury. Functional assessments of nerve regeneration were analyzed using the sciatic functional index (SFI) and hindlimb range of motion (ROM). Nerve regeneration was investigated by measuring the myelin sheath thickness of the sciatic nerve using transmission electron microscopy (TEM) and by analyzing the expression of growth-associated protein 43 (GAP43) in sciatic nerve using western blot and immunofluorescence staining. We found that sciatic-injured rats that were irradiated with LLLT at both 3 and 8 J/cm2 had significantly improved SFI but that a significant improvement of ROM was only found in rats with LLLT at 8 J/cm2. Furthermore, the myelin sheath thickness and GAP43 expression levels were significantly enhanced in sciatic nerve-crushed rats receiving 808-nm LLLT at 3 and 8 J/cm2. Taken together, these results suggest that 808-nm LLLT at a low energy density (3 J/cm2 and 8 J/cm2) is capable of enhancing sciatic nerve regeneration following a crush injury.
Highlights
Peripheral nerve injury results from various etiologies, such as traction, crushing, ischemic change, cutting injury and long bone fracture, that lead to axonotmesis, in which axons and the covering myelin sheaths are damaged but the connective tissue is preserved, or more severely, neurotmesis, which involves disruption of the entire nerve fiber [1,2]
These results demonstrated effective sciatic nerve injury leading to declined locomotion
After 20 days, we found significant improvement of the sciatic functional index (SFI) in the groups receiving 3 and 8 J/cm2 level laser therapy (LLLT) compared with the crush group without irradiation
Summary
Peripheral nerve injury results from various etiologies, such as traction, crushing, ischemic change, cutting injury and long bone fracture, that lead to axonotmesis, in which axons and the covering myelin sheaths are damaged but the connective tissue is preserved, or more severely, neurotmesis, which involves disruption of the entire nerve fiber [1,2]. Injury to the peripheral nerve results in secondary muscle atrophy, causing various levels of disabilities. Regeneration occurs, albeit slowly, after peripheral nerve injury. Non-surgical approaches have been developed to facilitate nerve regeneration either for the primary management of axonotmesis or as an adjunctive therapy after surgical repair. The foremost treatment of nerve injury should be rehabilitation programs to maintain adequate joint range of motion and muscle tone to avoid secondary muscle atrophy. Physical therapies such as low frequency electrical stimulation [6,7,8] and magnetic stimulation [9] were proposed to have positive effects on nerve regeneration and functional recovery. The high medical expense and invasiveness of these procedures prevents their use in routine clinical practice
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