Analysis of the variation in low-level laser energy density on the crushed sciatic nerves of rats: a morphological, quantitative, and morphometric study (original) (raw)
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Lasers in Medical Science, 2010
Peripheral nerves are structures that, when damaged, can result in significant motor and sensory disabilities. Several studies have used therapeutic resources with the aim of promoting early nerve regeneration, such as the use of low-power laser. However, this laser therapy does not represent a consensus regarding the methodology, thus yielding controversial conclusions. The objective of our study was to investigate, by functional evaluation, the comparative effects of low-power laser (660 nm and 830 nm) on sciatic nerve regeneration following crushing injuries. Twenty-seven Wistar rats subjected to sciatic nerve injury were divided into three groups: group sham, consisting of rats undergoing simulated irradiation; a group consisting of rats subjected to gallium–aluminum–arsenide (GaAlAs) laser at 660 nm (10 J/cm2, 30 mW and 0.06 cm2 beam), and another one consisting of rats subjected to GaAlAs laser at 830 nm (10 J/cm2, 30 mW and 0.116 cm2). Laser was applied to the lesion for 21 days. A sciatic functional index (SFI) was used for functional evaluation prior to surgery and on days 7, 14, and 21 after surgery. Differences in SFI were found between group 660 nm and the other ones at the 14th day. One can observe that laser application at 660 nm with the parameters and methods utilised was effective in promoting early functional recovery, as indicated by the SFI, over the period evaluated.
The in-vivo-nerve response to direct Low-Energy-Laser Irradiation
Acta Neurochirurgica, 1988
To study the iu-vivo effects of direct Low-Energy Laser Irradiation (LELI) on the Peripheral Nervous System, the sciatic nerve in rats was surgically exposed, crushed and then subjected to the direct irradiation of either of two continuous-wave HeNe lasers--0.3mW or 17mW. We found that the 0.3roW laser significantly boosts the electrical activity in both the injured and non-injured nerves. The temperature changes of the nerve were measured during irradiation, and no thermal effect was detected. These findings could have direct therapeutic applications in various surgical situations.
Previous studies have shown that low-level laser therapy (LLLT) promotes posttraumatic nerve regeneration. The objective of the present study was to assess the efficacy of 685-nm LLLT at the dosage of 3 J/cm 2 in the functional recovery of the sciatic nerve in rats following crushing injury. The left sciatic nerves of 20 male Wistar rats were subjected to controlled crush injury by a hemostatic tweezers, and the rats were randomly allocated into two experimental groups as follows: control group and laser group. Laser irradiation (685 nm wavelength; 15 mW, CW, 3 J/cm 2 , spot of 0.028 cm 2 ) was started on the postsurgical first day, above the site of injury, and was continued for 21 consecutive days. Functional recovery was evaluated at 3 weeks postoperatively by measuring the sciatic functional index (SFI) and sciatic static index (SSI) at weekly intervals. The treated rats showed improvement in motion pattern. The SFI and SSI results were significant when comparing two groups on the 14th and 21st postoperative days (p<0.05). There were intra-group differences detected in laser group in different periods (p<0.05). Low-level laser irradiation, with the parameters used in the present study, accelerated and improved sciatic nerve function in rats after crushing injury.
Lasers in Surgery and Medicine, 2010
Background and Objective: Post-traumatic nerve repair is still a challenge for rehabilitation. It is particularly important to develop clinical protocols to enhance nerve regeneration. The present study investigated the effects of 660 and 780 nm low-level laser therapy (LLLT) using different energy densities (10, 60, and 120 J/cm 2 ) on neuromuscular and functional recovery as well as on matrix metalloproteinase (MMP) activity after crush injury in rat sciatic nerve. Materials and Methods: Rats received transcutaneous LLLT irradiation at the lesion site for 10 consecutive days post-injury and were sacrificed 28 days after injury. Both the sciatic nerve and tibialis anterior muscles were analyzed. Nerve analyses consisted of histology (light microscopy) and measurements of myelin, axon, and nerve fiber cross-sectional area (CSA). S-100 labeling was used to identify myelin sheath and Schwann cells. Muscle fiber CSA and zymography were carried out to assess the degree of muscle atrophy and MMP activity, respectively. Statistical significance was set at 5% (P 0.05). Results: Six hundred sixty nanometer LLLT either using 10 or 60 J/cm 2 restored muscle fiber, myelin and nerve fiber CSA compared to the normal group (N). Furthermore, it increased MMP-2 activity in nerve and decreased MMP-2 activity in muscle and MMP-9 activity in nerve. In contrast, 780 nm LLLT using 10 J/cm 2 decreased MMP-9 activity in nerve compared to the crush group (CR) and N; it also restored normal levels of myelin and nerve fiber CSA. Both 60 and 120 J/cm 2 decreased MMP-2 activity in muscle compared to CR and N. 780 nm did not prevent muscle fiber atrophy. Functional recovery in the irradiated groups did not differ from the nonirradiated CR. Conclusion: Data suggest that 660 nm LLLT with low (10 J/cm 2 ) or moderate (60 J/cm 2 ) energy densities is able to accelerate neuromuscular recovery after nerve crush injury in rats. Lasers Surg. Med. 42:673-682, 2010.
PLoS ONE, 2014
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/cm 2 and a sciatic nerve crush injury group with or without 808-nm LLLT at 3, 8 or 15 J/cm 2 . 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/cm 2 had significantly improved SFI but that a significant improvement of ROM was only found in rats with LLLT at 8 J/cm 2 . 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/cm 2 . Taken together, these results suggest that 808-nm LLLT at a low energy density (3 J/cm 2 and 8 J/cm 2 ) is capable of enhancing sciatic nerve regeneration following a crush injury.
MNJ (Malang Neurology Journal)
Background: The physical therapy resources, as Low-Level Laser Therapy (LLLT) and neural mobilization are usually used with regenerative purpose and for the relief of symptoms for peripheral nerve injury. However, there is a lack of consensus on its effects as well as its association. Objective: Evaluate the influence of low-level laser therapy (LLLT) associated with neural mobilization (NM) on nerve regeneration of female Wistar rats subjected to sciatic compression. Methods: Twenty four Wistar rats were divided into: G1 (Placebo), G2 (NM), G3 (LLLT) and G4 (NM+LLLT), all animals were subject to compression of the right sciatic nerve. The treatment occurred on the 3 rd , 5 th , 7 th , 10 th , 12 th and 14 th postoperative day (PO). On the 17 th PO the animals were euthanized. Histological and morphometric analysis of the right (compression) and the left (control) sciatic nerve were performed. Results: In the morphometric analysis no significant differences between groups, but differences among sides were found. Histological analysis revealed the presence of inflammatory infiltrate and disruption of nerve fibers in the right sciatic nerves. Conclusion: Both techniques used (LLLT and neural mobilization), isolated and associated, on the parameters proposed, were not effective to accelerate the process of nerve regeneration.
Journal of Hand and Microsurgery, 2013
Peripheral nerve lesions caused sensory and motor deficits along the distribution of the injured nerve. Numerous researches have been carried out to enhance and/or accelerate the recovery of such lesions. The objective of this study was to assess the functional recovery of sciatic nerve in rats subjected to different fluences of low-level laser therapy (LLLT). Thirty-six animals were randomly divided into four groups: one consisting of sham rats and three others irradiated with progressive fluencies of 10 J/cm 2 , 40 J/cm 2 and 80 J/cm 2 of laser AsGaAl (830 nm) for 21 consecutive days. They were evaluated by the Sciatic Functional Index (SFI) method. The crush injury was performed by using a portable device with dead weight of 5,000 g whose load was applied for 10 min. A digital camera was used to record the footprints left on the acrylic track, before surgery and after, on the 7th, 14th, and 21st days. The results also showed that on the 7th day, there was a difference between the groups irradiated with 40 J/cm 2 , when compared with the sham group (p<0.05). On the 14th day the groups irradiated with 40 J/cm 2 and 80 J/cm 2 also presented better results when compared with sham, however, on the 21st day, no inter-group difference was found (p>0.05). It was possible to observe that the LLLT at fluency of 40 J/cm 2 and 80 J/cm 2 had a positive influence on the acceleration of the functional nerve recovery.
DOAJ (DOAJ: Directory of Open Access Journals), 2013
Objective: To investigate the influence of low intensity laser irradiation on the regeneration of the fibular nerve of rats after crush injury. Methods: Twenty-five rats were used, divided into three groups: 1) intact nerve, no treatment; 2) crushed nerve, no treatment; 3) crush injury, laser irradiation applied on the medullary region corresponding to the roots of the sciatic nerve and subsequently on the course of the damaged nerve. Laser irradiation was carried out for 14 consecutive days. Results: Animals were evaluated by functional gait analysis with the peroneal functional index and by histomorphometric analysis using the total number of myelinated nerve fibers and their density, total number of Schwann cells, total number of blood vessels and the occupied area, minimum diameter of the fiber diameter and G-quotient. Conclusion: According to the statistical analysis there was no significant difference among groups and the authors conclude that low intensity laser irradiation has little or no influence on nerve regeneration and functional recovery. Laboratory investigation.
Lasers in medical science, 2012
This study evaluated the functional and quantitative differences between the early and delayed use of phototherapy in crushed median nerves. After a crush injury, low-level laser therapy (GaAs) was applied transcutaneously at the injury site, 3 min daily, with a frequency of five treatments per week for 2 weeks. In the early group, the first laser treatment started immediately after surgery, and in the delayed group, after 7 days. The grasping test was used for functional evaluation of the median nerve, before, 10, and 21 days after surgery, when the rats were killed. Three segments of the median nerve were analyzed histomorphometrically by light microscopy and computer analysis. The following features were observed: myelinated fiber and axon diameters, myelin sheath area, g-ratio, density and number of myelinated fibers, and area and number of capillaries. In the proximal segment (site of crush), the nerves of animals submitted to early and delayed treatment showed myelinated fiber diameter and myelin sheath area significantly larger compared to the untreated group. In the distal segment, the myelin sheath area was significantly smaller in the untreated animals compared to the delayed group. The untreated, early, and delayed groups presented a 50, 57, and 81% degree of functional recovery, respectively, at 21 days after injury, with a significant difference between the untreated and delayed groups. The results suggest that the nerves irradiated with low-power laser exhibit myelinated fibers of greater diameter and a better recovery of function.