Effects of 940 nm light-emitting diode (led) on sciatic nerve regeneration in rats

Preventive effects of transcranial photobiomodulation on epileptogenesis in a kainic acid-induced rat epilepsy model

OBJECTIVE

Temporal lobe epilepsy affects nearly 50 million people worldwide and is a major burden to families and society. A significant portion of patients are living in developing countries with limited access to therapeutic resources. This highlights the urgent need to develop more readily available, noninvasive treatments for seizure control. This research explored the effectiveness of transcranial photobiomodulation (tPBM), a non-invasive method utilizing photon-tissue interactions, for preventing epileptogenesis and controlling seizures.

METHODS

In a kainic acid (KA)-induced rat model of epilepsy, two different wavelengths of tPBM, 808 nm and 940 nm, were applied separately in two groups of animals (KA+808 and KA+940). The ability of tPBM for seizure control was evaluated by comparing the occurrence rate of interictal epileptiform discharges (IED) and behavioral seizures among three groups: KA, KA+808, KA+940. Prevention of epileptogenesis was assessed by comparing the occurrence rate of high frequency oscillations (HFOs), especially fast ripple (FR) rate, among the three groups. Nissl staining and immunostaining for the apoptosis marker caspase-3 were used as indications of neuroprotection.

RESULTS

The KA+808 group and the KA+940 group showed significantly lower FR and IED rates compared to the KA group. Weekly FR rates started to drop during the first week of tPBM treatment. The KA+808 and KA+940 groups also displayed milder seizure behaviors and less neuronal loss in hippocampal areas compared to KA rats without tPBM treatment. Similarly, lower caspase-3 levels in the KA+808 and KA+940 compared with the KA group suggested effectiveness of tPBM in reducing cell death.

SIGNIFICANCE

tPBM of 808 nm/940 nm showed effectiveness in suppressing epileptogenesis and ictogenesis in the KA-induced rat epilepsy model. This effectiveness of tPBM can be linked to the neuroprotection benefits of photon-tissue interactions. Further studies are warranted to elucidate the fundamental mechanism of tPBM protection, determine optimal treatment parameters and validate its effectiveness in other epilepsy models.

Enhancing nerve regeneration in infraorbital nerve injury rat model: effects of vitamin B complex and photobiomodulation

Orofacial nerve injuries may result in temporary or long-term loss of sensory function and decreased quality of life in patients. B vitamins are required for DNA synthesis and the repair and maintenance of phospholipids. In particular, vitamins B1, B6, and B12 are essential for neuronal function. Deficiency in vitamin B complex (VBC) has been linked to increased oxidative stress, inflammation and demyelination. Photobiomodulation (PBM) has antioxidant activity and is neuroprotective. In addition, a growing literature attests to the positive effects of PBM on nerve repair. To assess the effect of PBM and VBC on regenerative process we evaluated the expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), myelin basic protein (MBP), laminin and neurofilaments (NFs) using Western blotting to identify regenerative pattern after chronic constriction injury of the infraorbital nerve (CCI IoN) treated by PBM, VBC or its combination. After CCI IoN, the rats were divided into six groups naive, sham, injured (CCI IoN), treated with photobiomodulation (904 nm, 6.23 J/cm2, CCI IoN + PBM), treated with VBC (containing B1, B6 and B12) 5 times, CCI IoN + VBC) and treated with PBM and VBC (CCI IoN + VBC + PBM). The treatments could revert low expression of BDNF, MBP and laminin. Also reverted the higher expression of neurofilaments and enhanced expression of NGF. PBM and VBC could accelerate injured infraorbital nerve repair in rats through reducing the expression of neurofilaments, increasing the expression of BDNF, laminin and MBP and overexpressing NGF. These data support the notion that the use of PBM and VBC may help in the treatment of nerve injuries. This finding has potential clinical applications.

Effects of systemic vascular photobiomodulation using LED or laser on sensory–motor recovery following a peripheral nerve injury in Wistar rats

Peripheral nerve injury (PNI) is associated with considerable functional impairment. Photobiomodulation (PBM) has demonstrated positive effects regarding neuromuscular repair after PNI when applied locally to the nerve or injured muscle. However, the effects of systemic PBM with transcutaneous application over an important artery, which is also denominated vascular PBM (VPBM), remain unclear. The aim of the study was to compare the effects of VPBM with low-level laser (LLL) and light-emitting diode (LED) on gait, sensitivity and muscle morphology following a PNI. PNI was induced on Wistar rats using the sciatic nerve crushing technique. VPBM was performed over the rat's artery tail region with LED (850 nm, 40 mW, 3.2 J) and LLL (780 nm, 40 mW, 3.2 J). Gait functionality, mechanical (nociceptive) sensitivity, and morphology of the tibialis anterior muscle were evaluated at 7, 14, and 21 days after injury. An improvement in functional gait was shown in the VPBM-LLL group in all periods. Motor sensitivity was found after 14 days in the VPBM-LLL group. The left/right (L/R) muscle mass ratio revealed a reduction in muscle atrophy in the VPBM-LLL group at 7 days. Muscle fiber diameter increased in the VPBM-LED group at 14 days and increases in the cross-section area were found in the VPBM-LED and VPBM-LLL groups at 7 days. VPBM with both light sources (LED and LLL) positively modulated functioning and neuromuscular recovery following sciatic nerve injury in rats, with more pronounced results when using LLL.

Effects of photobiomodulation therapy on functional recovery, angiogenesis and redox status in denervated muscle of rats

Objective:

To evaluate the effects of photobiomodulation therapy in redox status, angiogenesis marker – vascular endothelial growth factor – and in the functional recovery in denervated muscle.

Methods:

A total of 32 female Wistar rats underwent a crush injury and were randomly divided into four groups: Light Emitting Diode Group 2 and Control Group 2 (muscle collected 2 days after injury), and Light Emitting Diode Group 21 and Control Group 21 (muscle collected 21 days afterinjury). Light Emitting Diode Group 2 and Light Emitting Diode Group 21 received two and ten light emitting diode applications (630±20nm, 9J/cm², 300mW), respectively, and the Control Group 2 and Control Group 21 did not receive any treatment. The function was evaluated by grasping test at four moments (pre-injury, 2, 10 and 21 post-injury days). The flexor digitorum muscle was collected for analysis of immunolocalization of vascular endothelial growth factor and redox parameters.

Results:

Functional improvement was observed at the second and tenth post-injury day in treated groups compared to control (p<0.005). The muscle tissue of treated groups presented higher immunohistochemical expression of vascular endothelial growth factor. Photobiomodulation therapy decreased the oxidative damage to lipid in Light Emitting Diode Group 2 compared to Control Group 2 (p=0.023) in the denervated muscle.

Conclusion:

Photobiomodulation therapy accelerated the functional recovery, increased angiogenesis and reduced lipid peroxidation in the denervated muscle at 2 days after injury.

Effects of Photobiomodulation Therapy (LED 630 nm) on Muscle and Nerve Histomorphometry after Axonotmesis

Peripheral injuries constitute a substantial clinical problem with unsatisfactory treatment. The study's objective was to analyze the effects of photobiomodulation therapy (PBMT) on median nerve regeneration and muscle recovery after axonotmesis. Twenty-four rats were randomized into three groups: control (CG), injury (IG), and LED therapy (LEDG). A 630 ± 20 nm (300-mW) LED was placed in contact with the skin. One point over the injury site was irradiated for 30 s, delivering 9 J (9 J cm-2 ). PBMT irradiation was performed once daily for 5 days followed by two-day interval and then more five consecutive days of treatment. Proximal and distal segments of the nerve and flexors muscles were removed for histomorphometric analysis using H&E staining for muscles and osmium tetroxide for nerves. The myelinated fiber and axon diameter and the myelin sheath thickness were greater in the proximal and distal nerve segments in the LEDG compared to the IG (P ≤ 0.05). The number of myelinated fibers was greater in the distal segment of the LEDG (P ≤ 0.05). The area, circumference, and diameter of the muscle fibers were larger in the LEDG than in the IG (P ≤ 0.05). The PBMT protocol used favored axonal regeneration and muscle recovery.

Photobiomodulation in Sciatic Nerve Crush Injuries in Rodents: A Systematic Review of the Literature and Perspectives for Clinical Treatment

Objective : The aim of the study was to perform a literature review to analyze the effect of photobiomodulation in experimental studies on peripheral nerve regeneration after sciatic nerve crush injury in rodents. Methods: A bibliographic search was performed in the electronic databases, including MEDLINE (PubMed), SCOPUS, and SciELO, from 2008 to 2018. Results: A total of 1912 articles were identified in the search, and only 19 fulfilled all the inclusion criteria. Along with the parameters most found in the manuscripts, the most used wavelengths were 660 nm and 830 nm, power of 30 and 40 mW, and energy density of 4 and 10 J/cm² . For total energy throughout the intervention period, the lowest energy found with positive effects was 0.70 J, and the highest 1.141 J. Seventeen studies reported positive effects on nerve regeneration. The variables selected to analyze the effect were: Sciatic Functional Index (SFI), Static Sciatic Index (SSI), morphometric, morphological, histological, zymographic, electrophysiological, resistance mechanics and range of motion (ROM). The variety of parameters used in the studies demonstrated that there is yet no pre-determined protocol for treating peripheral nerve regeneration. Only two studies by different authors used the same power, energy density, beam area, and power density. Conclusion: It was concluded that the therapeutic window of the photobiomodulation presents a high variability of parameters with the wavelength (632.8 to 940 nm), power (5 to 170 mW) and energy density (3 to 280 J /cm² ), promoting nerve regeneration through the expression of cytokines and growth factors that aid in modulating the inflammatory process, improving morphological aspects, restoring the functionality to the animals in a brief period.

Dose-dependent effect of the pulsed Nd:YAG laser in the treatment of crushed sciatic nerve in Wister rats: an experimental model

The objective of the study was to investigate the efficacy of three energy densities 4, 10, and 50 J/cm² of pulsed Nd:YAG laser for the treatment of crushed sciatic nerve in Wister rats by evaluating changes in the sciatic functional index and the electrophysiology.A total of 180 Wistar rats were involved in the study. Rats were randomly assigned to five groups. Rats were subjected to the sciatic nerve crushing. Control negative (CONT-ve), which received no crushing; control positive (CONT+ve), which received crushing with no laser; and HILT-4, HILT-10, and HILT-50 groups, which received pulsed Nd:YAG laser (10 Hz, 360 mJ/cm²) with energy densities 4, 10, and 50 J/cm², respectively. The SFI, the amilitude of compound motor action potential (CMAP) and sciatic motor nerve conduction velocity (MNCV) were measured before and after seven, 14, and 21 days after crushing. For the SFI and electrophysiological analysis, repeated measures ANOVA is used, followed by Bonferroni's repeated-measures test. Statistical significance was set at p < 0.05. After one week, there was no significant difference in SFI, CMAP, and MNCV among the three laser groups with significant changes between them and CONT-ve and CONT+ve groups. There was a significant increase in either CMAP amplitude or MNCV after 14 days with significant decrease in the SFI after 21 days among all treatment groups. The pulsed Nd:YAG laser applied with energy densities 4, 10, and 50 J/cm² significantly decreased the SFI and increased the CMAP and MNCV of the crushed sciatic nerve in Wister rats. Among laser doses, the difference in the rate of recovery in the electrophysiology was found after two weeks while in the SFI after three weeks. The improvement after the nerve injury was time and dose dependent.

Engineered nanomedicine for neuroregeneration: light emitting diode-mediated superparamagnetic iron oxide-gold core-shell nanoparticles functionalized by nerve growth factor

This paper reports nerve growth factor functionalized superparamagnetic iron oxide-gold core-shell nanoparticles (NGF-SPIO-Au NPs), an engineered nanomedicine for non-invasive neuron regeneration when irradiated by a low-intensity light-emitting diode (LED). NGF-SPIO-Au NPs of 20 μg/ml, were tested on PC-12 neuron-like cells, irradiated by LEDs (525 nm, 1.09, 1.44, and 1.90 mW/cm²). A remarkable Ca²⁺ influx was detected in differentiated PC-12 cells treated with NPs, irradiated by LED of 1.90 and 1.44 mW/cm² with great cell viability (>84%) and proliferations. The strong heat generated through their plasmonic surface upon LED irradiation on NGF-SPIO-Au NPs was observed. For cells treated with LED (1.90 mW/cm²) and NGF-SPIO-Au NPs, a dramatic enhancement of neuronal differentiation (83%) and neurite outgrowth (51%) was found, and the upregulation of both the neural differentiation specific marker (β3-tubulin) and the cell adhesive molecule (integrin β1) was observed by the reverse transcription-polymerase chain reaction and western blot analysis.

Cold water immersion or LED therapy after training sessions: effects on exercise-induced muscle damage and performance in rats

Cryotherapy and phototherapy have been suggested as recovery methods due to their anti-inflammatory effects. They may also induce mitochondrial biogenesis, thus favoring endurance training adaptation. The aim of this study was to evaluate the anti-inflammatory and ergogenic effects of phototherapy or cold water immersion (CWI) applied daily after exercise in rats. Thirty-five rats were divided into five groups: control (CO), non-exercised (CE), passive recovery (PR), cold water immersion (CWI), and LED therapy (LED). The CO and CE groups were not submitted to training; however, the CE were submitted to an exhaustion test after the training period. Low-intensity swimming training (21 sessions, 45 min) was performed followed by passive recovery (PR), CWI (10 °C, 5 min), or infrared irradiation (940 nm, 4 J/cm²). Forty-eight hours after the final training session, the CE, PR, CWI, and LED animals were submitted to an exhaustion test. The animals were euthanized 24 h later and submitted to hematological, creatine kinase (CK), and C-reactive protein (PCR) analysis. Gastrocnemius and soleus muscles were submitted to histological analysis. No differences in blood cell counts, CK, and PCR were detected between groups. The CE group presented an increased number of areas with necrosis in the gastrocnemius and soleus muscles. The PR group presented the highest frequency of areas with edema and inflammation followed by CWI and LED groups. None of the recovery methods improved the performance in the exhaustion test. Successive applications of recovery methods do not improve exercise performance, but downmodulate the inflammation and prevent muscle necrosis.

LED session prior incremental step test enhance VO2max in running

This study aimed to investigate the effect of prior LED sessions on the responses of cardiorespiratory parameters during the running incremental step test. Twenty-six healthy, physically active, young men, aged between 20 and 30 years, took part in this study. Participants performed two incremental load tests after placebo (PLA) and light-emitting diode application (LED), and had their gas exchange, heart rate (HR), blood lactate, and rating of perceived exertion (RPE) monitored during all tests. The PLA and LED conditions were compared using the dependent Student t test with significance set at 5%. The T test showed higher maximum oxygen uptake (VO_2max) (PLA = 47.2 ± 5.7; LED = 48.0 ± 5.4 ml kg^-1 min^-1, trivial effect size), peak velocity (V_peak) (PLA = 13.4 ± 1.2; LED = 13.6 ± 1.2 km h^-1, trivial effect size), and lower maximum HR (PLA = 195.3 ± 3.4; LED = 193.3 ± 3.9 b min^-1, moderate effect size) for LED compared to PLA conditions. Furthermore, submaximal values of HR and RPE were lower, and submaximal VO₂ values were higher when LED sessions prior to the incremental step test were applied. A positive response of the previous LED application in the blood lactate disappearance was also demonstrated, especially 13 and 15 min after the test. It is concluded that LED sessions prior to exercise modify cardiorespiratory response by affecting running tolerance during the incremental step test, metabolite clearance, and RPE. Therefore, LED could be used as a prior exercise strategy to modulate oxidative response acutely in targeted muscle and enhance exercise tolerance.

Effects of near-infrared LED therapy on experimental tooth replantation in rats

BACKGROUND/AIM

Dental avulsion damages periodontal tissues and may induce dentoalveolar ankylosis and root resorption after replantation. The aim of this work was to evaluate the effects of light-emitting diode (LED) therapy after tooth replantation.

MATERIAL AND METHODS

The upper right incisors of 36 male Wistar rats were extracted and replanted after 15 min. The control group (Co, n = 18) was submitted to replantation and the LED group (n = 18) was submitted to replantation and LED therapy (940 nm, 4 J cm^-2 ) for three consecutive days (0, 24, and 48 h). Six animals from each group were euthanized at 7, 14, and 21 days for histological analysis. The upper left incisors were used as a negative control. Data were compared using the Fisher exact test, considering P < 0.05.

RESULTS

After 7 days, the Co (73.3%) and LED (72.2%) groups presented areas of periodontal ligament necrosis. However, periodontal ligament necrosis was more frequent in the LED group at 14 (70%, P < 0.05) and 21 days (43.2%, P < 0.05) in relation to the Co group (33 and 21.6%). Inflammatory cell infiltration was more frequent in the Co group at 7 days (100%) than the LED group (24.4%, P < 0.05), but increased in the LED group after 21 days (83.3%, P < 0.05). Bone necrosis was more frequent in the LED group after 14 (79%, P < 0.05) and 21 days (60%, P < 0.005) than in the Co group (45% and 20%). Bone repair was evident in the Co group at 14 days. All of the replanted teeth had pulp necrosis.

CONCLUSION

The results suggest that the application of LED therapy up to 48 h after tooth replantation may delay periodontal ligament repair.

A comparative study of red and blue light-emitting diodes and low-level laser in regeneration of the transected sciatic nerve after an end to end neurorrhaphy in rabbits

This study aimed at evaluating the effects of red and blue light-emitting diodes (LED) and low-level laser (LLL) on the regeneration of the transected sciatic nerve after an end-to-end neurorrhaphy in rabbits. Forty healthy mature male New Zealand rabbits were randomly assigned into four experimental groups: control, LLL (680 nm), red LED (650 nm), and blue LED (450 nm). All animals underwent the right sciatic nerve neurotmesis injury under general anesthesia and end-to-end anastomosis. The phototherapy was initiated on the first postoperative day and lasted for 14 consecutive days at the same time of the day. On the 30th day post-surgery, the animals whose sciatic nerves were harvested for histopathological analysis were euthanized. The nerves were analyzed and quantified the following findings: Schwann cells, large myelinic axons, and neurons. In the LLL group, as compared to other groups, an increase in the number of all analyzed aspects was observed with significance level (P < 0.05). This finding suggests that postoperative LLL irradiation was able to accelerate and potentialize the peripheral nerve regeneration process in rabbits within 14 days of irradiation.

Promotion of neural sprouting using low-level green light-emitting diode phototherapy

We irradiated neuroblastoma SH-SY5Y cell line with low-level light-emitting diode (LED) illumination at a visible wavelength of 520 nm (green) and intensity of 100 mW∕cm2. We captured and analyzed the cell morphology before LED treatment, immediately after, and 12 and 24 h after treatment. Our study demonstrated that LED illumination increases the amount of sprouting dendrites in comparison to the control untreated cells. This treatment also resulted in more elongated cells after treatment in comparison to the control cells and higher levels of expression of a differentiation related gene. This result is a good indication that the proposed method could serve in phototherapy treatment for increasing sprouting and enhancing neural network formation.

Effects of light-emitting diode (LED) therapy on skeletal muscle ischemia reperfusion in rats

Low-level laser therapy has been shown to decrease ischemia-reperfusion injuries in the skeletal muscle by induction of synthesis of antioxidants and other cytoprotective proteins. Recently, the light-emitting diode (LED) has been used instead of laser for the treatment of various diseases because of its low operational cost compared to the use of a laser. The objective of this work was to analyze the effects of LED therapy at 904 nm on skeletal muscle ischemia-reperfusion injury in rats. Thirty healthy male Wistar rats were allocated into three groups of ten rats each as follows: normal (N), ischemia-reperfusion (IR), and ischemia-reperfusion + LED (IR + LED) therapy. Ischemia was induced by right femoral artery clipping for 2 h followed by 2 h of reperfusion. The IR + LED group received LED irradiation on the right gastrocnemius muscle (4 J/cm(2)) immediately and 1 h following blood supply occlusion for 10 min. At the end of trial, the animals were euthanized and the right gastrocnemius muscles were submitted to histological and histochemical analysis. The extent of muscle damage in the IR + LED group was significantly lower than that in the IR group (P < 0.05). In comparison with other groups, tissue malondialdehyde (MDA) levels in the IR group were significantly increased (P < 0.05). The muscle tissue glutathione (GSH), superoxide dismutases (SOD), and catalase (CAT) levels in the IR group were significantly lower than those in the subjects in other groups. From the histological and histochemical perspective, the LED therapy has alleviated the metabolic injuries in the skeletal muscle ischemia reperfusion in this experimental model.

In vitro and in vivo optimization of infrared laser treatment for injured peripheral nerves

BACKGROUND AND OBJECTIVE

Repair of peripheral nerve injuries remains a major challenge in restorative medicine. Effective therapies that can be used in conjunction with surgical nerve repair to improve nerve regeneration and functional recovery are being actively investigated. It has been demonstrated by a number of peer reviewed publications that photobiomodulation (PBM) supports nerve regeneration, reinnervation of the denervated muscle, and functional recovery after peripheral nerve injury. However, a key issue in the use of PBM as a treatment for peripheral nerve injury is the lack of parameter optimization for any given wavelength. The objective of this study was to demonstrate that for a selected wavelength effective in vitro dosing parameters could be translated to effective in vivo parameters.

MATERIALS AND METHODS

Comparison of infra-red (810 and 980 nm wavelengths) laser treatment parameters for injured peripheral nerves was done beginning with a series of in vitro experiments using primary human fibroblasts and primary rat cortical neurons. The primary rat cortical neurons were used for further optimization of energy density for 980 nm wavelength light using measurement of total neurite length as the bioassay. For these experiments, the parameters included a 1 W output power, power density of 10 mW/cm(2) , and energy densities of 0.01, 0.1, 0.5, 2, 10, 50, 200, 1,000, and 5,000 mJ/cm(2) . For translation of the in vitro data for use in vivo it was necessary to determine the transcutaneous penetration of 980 nm wavelength light to the level of the peroneal nerve. Two anesthetized, male White New Zealand rabbits were used for these experiments. The output power of the laser was set at 1.0 or 4.0 W. Power density measurements were taken at the surface of the skin, sub-dermally, and at the level of the nerve. Laser parameters used in the in vivo studies were calculated based on data from the in vitro studies and the light penetration measurements. For the in vivo experiments, a total of 22 White New Zealand rabbits (2.34-2.89 kg) were used. Translated dosing parameters were refined in a pilot study using a transection model of the peroneal nerve in rabbits. Output powers of 2 and 4 W were tested. For the final set of in vivo experiments, the same transection nerve injury model was used. An energy density of 10 mW/cm(2) at the level of the peroneal nerve was selected and the laser parameters were further refined. The dosing parameters used were: 1.5 W output power, 43 seconds exposure, 8 cm(2) area and a total energy of 65 J.

RESULTS

In vitro, 980 nm wavelength light at 10 mW/cm(2) significantly improved neurite elongation at energy densities between 2 and 200 mJ/cm(2) . In vivo penetration of the infrared light measured in anesthetized rabbits showed that on average, 2.45% of the light applied to the skin reached the depth of the peroneal nerve. The in vivo pilot study data revealed that the 4 W parameters inhibited nerve regeneration while the 2 W parameters significantly improved axonal regrowth. For the final set of experiments, the irradiated group performed significantly better in the toe spread reflex test compared to the control group from week 7 post-injury, and the average length of motor endplates returned to uninjured levels.

CONCLUSION

The results of this study demonstrate that treatment parameters can be determined initially using in vitro models and then translated to in vivo research and clinical practice. Furthermore, this study establishes that infrared light with optimized parameters promotes accelerated nerve regeneration and improved functional recovery in a surgically repaired peripheral nerve.

Effects of early and delayed laser application on nerve regeneration

The aim of this study is to analyze the differences between early and delayed use of low-level laser therapy (LLLT) in functional and morphological recovery of the peripheral nerve. Thirty male Wistar rats were divided into three groups after the sciatic nerve was crushed: (1) control group without laser treatment, (2) early group with laser treatment started immediately after surgery and lasted 14 days, and (3) delayed group with laser treatment starting on the postoperative day 7 and lasted until day 21. A 650-nm diode laser (model: DH650-24-3(5), Huanic, China) with an output power of 25 mW exposed transcutaneously at three equidistant points on the surgical mark corresponding to the crushed nerve. The length of the laser application was calculated as 57 s to satisfy approximately 10 J/cm(2). A Sciatic Functional Index (SFI) was used to evaluate functional improvement in groups at pre- and post-surgery (on days 7, 14, and 21). Compound action potential (CAP) was measured after the sacrifice and histological examination was performed for all groups. SFI results showed that there was no significant difference between groups at different days (p > 0.05). On the other hand, the latency of CAP decreased significantly (p < 0.05) in the delayed group. Histological examination confirmed that the number of mononuclear cells was lower (p < 0.05) in both early and delayed groups. In conclusion, results supported the hypothesis that LLLT could accelerate the rate of recovery of injured peripheral nerves in this animal model. Though both laser groups had positive outcomes, delayed group showed better recovery.

The brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3, and induced nitric oxide synthase expressions after low-level laser therapy in an axonotmesis experimental model

BACKGROUND DATA

A robust body of evidence has shown that low-level laser therapy (LLLT) improves peripheral nerve regeneration. However, the biochemical background triggered in this process is not yet fully understood.

OBJECTIVE

The purpose of this study was to evaluate the mRNA expression of neurotrophic factors (brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF], and neurotrophin-3, [NT-3]) and also an inflammatory marker (induced nitric oxide synthase [iNOS]) in an axonotmesis experimental model after low-level laser therapy.

METHODS

Thirty-six adult male Wistar rats (250-350 g) were subjected to right sciatic nerve crush injury, and 24 h later, the animals in the three different experimental groups (n=18) were irradiated on a daily basis with helium-neon laser (collimated HeNe laser, continuous emission, wavelength: 632.8 nm, power density: 0.5 mW/cm(2), irradiation time: 20 sec, energy density: 10 J/cm(2)) during 7, 14, and 21 consecutive days, respectively. The control group (n=18) underwent the same procedures, but with the equipment turned off. At the end of the experiments, animals were killed with an overdose of anesthesia to remove samples from the sciatic nerve lesion epicenter to determine the mRNA expression of BDNF, NGF, NT-3 and iNOS enzyme.

RESULTS

Comparisons between groups showed that HeNe laser increased the mRNA expression of both BDNF and NGF factors after 14 days of LLLT, with peak expression at the 21st day. Increase in NT-3 mRNA expression was not observed. In addition, HeNe laser produced iNOS expression reduction, which played an important role in the inflammatory process.

CONCLUSIONS

The reported data could have a relevant practical value because LLLT is a noninvasive procedure, and have revealed significant increase in neurotrophic factor expressions and inflammatory process reduction, opening the possibility of using LLLT as an important aid to nerve regeneration process.

Effects of light emitting diode (LED) therapy and cold water immersion therapy on exercise-induced muscle damage in rats

The aim of this work is to analyze the effects of LED therapy at 940 nm or cold water immersion therapy (CWI) after an acute bout of exercise on markers of muscle damage and inflammation. Thirty-two male Wistar rats were allocated into four groups: animals kept at rest (control), exercised animals (E), exercised + CWI (CWI), and exercised + LED therapy (LED). The animals swam for 100 min, after which blood samples were collected for lactate analysis. Animals in the E group were returned to their cages without treatment, the CWI group was placed in cold water (10°C) for 10 min and the LED group received LED irradiation on both gastrocnemius muscles (4 J/cm(2) each). After 24 h, the animals were killed and the soleus muscles were submitted to histological analysis. Blood samples were used for hematological and CK analyses. The results demonstrated that the LED group presented fewer areas of muscle damage and inflammatory cell infiltration and lower levels of CK activity than the E group. Fewer areas of damaged muscle fiber were observed in the LED group than in CWI. CWI and LED did not reduce edema areas. Hematological analysis showed no significant effect of either treatment on leukocyte counts. The results suggest that LED therapy is more efficient than CWI in preventing muscle damage and local inflammation after exercise.