Zymographic and ultrastructural evaluations after low-level laser irradiation on masseter muscle of HRS/J strain mice

Low-level laser therapy (LLLT) has been widely used in the treatment of the stomatognathic system dysfunction; however, its biological effect remains poorly understood. This study evaluated the effect of LLLT (GaAlAs, 780 nm, 20 J/cm², 40 mW) on masseter muscle of HRS/J mice after different numbers of laser irradiations (three, six, and ten) for 20 s in alternate days. Three experimental groups were defined according to the number of laser irradiations and three control groups (n?=?5) were used. On the third day after the last irradiation, all animals were killed and the masseter muscle was removed and processed for the following analysis: (a) transmission electron microscopy, (b) zymography, (c) immunohistochemistry for vascular endothelial growth factor (VEGF) and VEGFR-2. The results showed: (a) with six laser applications, a dilation of T tubules, and sarcoplasmic reticulum cistern, increased pinocytosed vesicles in the endothelium; with ten laser applications, few pinocytic vesicles in the endothelium and condensed mitochondria. (b) Under the conditions of this study, the synthesis of other matrix metalloproteinases was not observed, only the MMP-2 and -9. (c) After ten laser irradiations, immunostaining was observed only for VEGFR-2. We conclude that after six laser applications, ultrastructural changes may facilitate the Ca⁺² transfer to cytosol and increase the fluid transport from one surface to another. The ultrastructural changes and no immunostaining for VEGF with ten applications may decrease the metabolic activity as well as damage the angiogenic process, suggesting that an effective number of laser applications may be less than ten, associating to this therapy a better cost–benefit.     

The influence of low-level laser therapy on parameters of oxidative stress and DNA damage on muscle and plasma in rats with heart failure

In heart failure (HF), there is an imbalance between the production of reactive oxygen species and the synthesis of antioxidant enzymes, causing damage to the cardiovascular function and increased susceptibility to DNA damage. The aim of this study was to evaluate the influence of low-level laser therapy (LLLT) on parameters of oxidative stress and DNA damage in skeletal muscle and plasma of rats with HF. Wistar rats were allocated into six groups: “placebo” HF rats (P-HF, n?=?9), “placebo” Sham rats (P-sham, n?=?8), HF rats at a dose 3 J/cm² of LLLT (3 J/cm²-HF, n?=?8), sham rats at a dose 3 J/cm² of LLLT (3 J/cm²-sham, n?=?8), HF rats at a dose 21 J/cm² of LLLT (21 J/cm²-HF, n?=?8) and sham rats at a dose 21 J/cm² of LLLT (21 J/cm²-sham, n?=?8). Animals were submitted to a LLLT protocol for 10 days at the right gastrocnemius muscle. Comparison between groups showed a significant reduction in superoxide dismutase (SOD) activity in the 3 J/cm²-HF group (p?=?0.03) and the 21 J/cm²-HF group (p?=?0.01) compared to the P-HF group. 2′,7′-Dihydrodichlorofluorescein (DCFH) oxidation levels showed a decrease when comparing 3 J/cm²-sham to P-sham (p?=?0.02). The DNA damage index had a significant increase either in 21 J/cm²-HF or 21 J/cm²-sham in comparison to P-HF (p?=?0.004) and P-sham (p?=?0.001) and to 3 J/cm²-HF (p?=?0.007) and 3 J/cm²-sham (p?=?0.037), respectively. Based on this, laser therapy appears to reduce SOD activity and DCFH oxidation levels, changing the oxidative balance in the skeletal muscle of HF rats. Otherwise, high doses of LLLT seem to increase DNA damage.     

Effect of low-level laser therapy on angiogenesis and matrix metalloproteinase-2 immunoexpression in wound repair

Low-level laser therapy (LLLT) induces anti-inflammatory and angiogenic activities in wound healing. However, the mechanism of action and optimal parameters require further clarification. In this study, we investigated the effects of LLLT on wound healing matrix metalloproteinase (MMP)-2 immunoexpression and angiogenic processes. Twenty female Wistar rats were randomly divided into four groups (n?=?5) according to the treatments as follows. CG7 and CG14 were control groups at days 7 and 14, respectively, which received physiological saline (0.9 % NaCl daily). LG7 and LG14 were laser therapy groups at days 7 and 14, respectively, which received two (LG7) or four (LG14) LLLT applications (40 mW; 660 nm; 4 J/cm²). A dorsal skin sample in the wound area (measuring 2 cm²) was removed after the experimental period, and then the animals were euthanized. The specimens were processed for qualitative and quantitative histological analyses and measurement of MMP-2 expression in the dermis and epidermis. A persistent crust and moderate number of inflammatory cells were found in CG7 and CG14 groups. In the LG14 group, wounds demonstrated complete re-epithelization at the remodeling phase. Angiogenesis and MMP-2 expression were higher in LLLT-treated groups, particularly the LG14 group, which correlated according to the Spearman correlation test. LLLT improves wound healing by enhancing neocollagenesis, increasing the amount of new vessels formed in the tissue (neoangiogenesis), and modulating MMP-2 expression. Epidermal overexpression of MMP-2 was correlated to angiogenic processes.     

Effects of low-level laser therapy on mitochondrial respiration and nitrosyl complex content

Among the photochemical reactions responsible for therapeutic effects of low-power laser radiation, the photolysis of nitrosyl iron complexes of iron-containing proteins is of primary importance. The purpose of the present study was to compare the effects of blue laser radiation on the respiration rate and photolysis of nitrosyl complexes of iron-sulfur clusters (NO-FeS) in mitochondria, subjected to NO as well as the possibility of NO transfer from NO-FeS to hemoglobin. It was shown that mitochondrial respiration in State 3 (V₃) and State 4 (V₄), according to Chance, dramatically decreased in the presence of 3 mM NO, but laser radiation (λ?=?442 nm, 30 J/cm²) restored the respiration rates virtually to the initial level. At the same time, electron paramagnetic resonance (EPR) spectra showed that laser irradiation decomposed nitrosyl complexes produced by the addition of NO to mitochondria. EPR signal of nitrosyl complexes of FeS-clusters, formed in the presence of 3 mM NO, was maximal in hypoxic mitochondria, and disappeared in a dose-dependent manner, almost completely at the irradiation dose 120 J/cm². EPR measurements showed that the addition of lysed erythrocytes to mitochondria decreased the amount of nitrosyl complexes in iron-sulfur clusters and produced the accumulation of NO-hemoglobin. On the other hand, the addition of lysed erythrocytes to mitochondria, preincubated with nitric oxide, restored mitochondrial respiration rates V₃ and V₄ to initial levels. We may conclude that there are two possible ways to destroy FeS nitrosyl complexes in mitochondria and recover mitochondrial respiration inhibited by NO: laser irradiation and ample supply of the compounds with high affinity to nitric oxide, including hemoglobin.     

Inhibitory effects of low-level laser therapy on skin-flap survival in a rat model

BACKGROUND:Although several studies have demonstrated the effects of low-level laser therapy (LLLT) on skin flap viability, the role of higher doses has been poorly investigated.OBJECTIVE:To investigate the inhibitory effect of the LLLT (λ=670 nm) on the viability of random skin flaps in a rat model using an irradiation energy of 2.79 J at each point.METHODS:Sixteen Wistar rats were randomly assigned into two groups: sham laser irradiation (n=8); and active laser irradiation (n=8). Animals in the active laser irradiation group were irradiated with a 670 nm diode laser with an energy of 2.79 J/point, a power output 30 mW, a beam area of 0.028 cm², an energy density of 100 J/cm², an irradiance of 1.07 W/cm² for 93 s/point. Irradiation was performed in 12 points in the cranial skin flap portion. The total energy irradiated on the tissue was 33.48 J. The necrotic area was evaluated on postoperative day 7.RESULTS:The sham laser irradiation group presented a mean (± SD) necrotic area of 47.96±3.81%, whereas the active laser irradiation group presented 62.24±7.28%. There was a significant difference in skin-flap necrosis areas between groups (P=0.0002).CONCLUSION:LLLT (λ=670 nm) increased the necrotic area of random skin flaps in rats when irradiated with an energy of 2.79 J (100 J/cm²).     

Effects of low-level laser therapy on bone formed after distraction osteogenesis

This study evaluated the effect of low-level laser therapy (LLLT) on the chemical composition, crystallinity and crystalline structure of bone at the site of distraction osteogenesis. Five rabbits were subjected to distraction osteogenesis (latency = 3 days; rate and frequency = 0.7 mm/day for 7 days; consolidation = 10 days), and three were given LLLT with arsenide–gallium–aluminum (AsGaAl; 830 nm, 40 mW): 10 J/cm² dose per spot, applied directly to the distraction osteogenesis site during the consolidation stage at 48 h intervals. Samples were harvested at the end of the consolidation stage. X-ray fluorescence and X-ray diffraction were used to analyze chemical composition, crystallinity and crystalline structure of bone at the distraction osteogenesis site. The analysis of chemical composition and calcium (Ca) and phosphorus (P) ratios revealed greater mineralization in the LLLT group. Diffractograms showed that the crystalline structure of the samples was similar to that of hydroxyapatites. Crystallinity percentages were greater in rabbits that were given LLLT. Crystallinity (41.14% to 54.57%) and the chemical composition of the bone at the distraction osteogenesis site were similar to the that of the control group (42.37% to 49.29%). The results showed that LLLT had a positive effect on the biomodulation of newly formed bone.     

Time-dependent effects of low-level laser therapy on the morphology and oxidative response in the skin wound healing in rats

This study aims to investigate the effect of different energy densities provided by low-level laser therapy (LLLT) on the morphology of scar tissue and the oxidative response in the healing of secondary intention skin wounds in rats. Twenty-four male adult Wistar rats were used. Skin wounds were made on the backs of the animals, which were randomized into three groups of eight animals each as follows, 0.9% saline (control); laser GaAsAl 30 J/cm² (L30); laser GaAsAl 90 J/cm² (L90). The experiment lasted 21 days. Every 7 days, the wound contraction index (WCI) was calculated and tissue from different wounds was removed to assess the proportion of cells and blood vessels, collagen maturation index (CMI), thiobarbituric acid reactive substance (TBARS) levels and catalase activity (CAT). On the 7th and 14th days, the WCI and the proportion of cells were significantly higher in groups L30 and L90 compared to the control (p?<?0.05). At all the time points analyzed, there was a greater proportion of blood vessels and a higher CMI in group L90 compared to the other groups (p?<?0.05). On the 7th and 14th days, lower TBARS levels and increased CAT activity were found in the L90 group compared to the control (p?<?0.05). On the 7th day, a moderately negative correlation was found between TBARS levels and WCI, CMI and CAT in all the groups. LLLT may modulate the oxidative status of wounded tissue, constituting a possible mechanism through which the LLLT exerts its effects in the initial phases of tissue repair.     

Cytokine mRNA expression is decreased in the subplantar muscle of rat paw subjected to carrageenan-induced inflammation after low-level laser therapy

OBJECTIVE: The objective of this work was to investigate the anti-inflammatory effects of low-level laser therapy, applied at different wavelengths (660 and 684 nm), on cytokine mRNA expression after carrageenan-induced acute inflammation in rat paw. BACKGROUND DATA: Low-level laser therapy (LLLT) has been observed to reduce pain in inflammatory disorders. However, little is known about the mechanisms behind this effect or whether it is wavelength-specific. MATERIALS AND METHODS: The test sample consisted of 32 rats divided into four groups: A(1) (control-saline), A(2) (carrageenan-only), A(3) (carrageenan + 660 nm laser therapy), and A(4) (carrageenan + 684 nm laser therapy). The animals from groups A(3) and A(4) were irradiated 1 h after induction of inflammation by carrageenan injection. Continuous-wave red lasers with wavelengths of 660 and 684 nm and dose of 7.5 J/cm(2) were used. RESULTS: Both the 660 nm and 684 nm laser groups had 30%-40% lower mRNA expression for cytokines TNF-alpha, IL-1beta, and IL-6 in the paw muscle tissue than the carrageenan-only control group. Cytokine measurements were made 3 h after laser irradiation of the paw muscle, and all cytokine differences between the carrageenan-only control group and the LLLT groups were statistically significant (p < 0.001). CONCLUSIONS: LLLT at the 660-nm and 684-nm wavelengths administered to inflamed rat paw tissue at a dose of 7.5 J/cm(2) reduce cytokine mRNA expression levels within 3 h in the laser-irradiated tissue.     

An experimental study of low-level laser therapy in rat Achilles tendon injury

The aim of this controlled animal study was to investigate the effect of low-level laser therapy (LLLT) administered 30 min after injury to the Achilles tendon. The study animals comprised 16 Sprague Dawley male rats divided in two groups. The right Achilles tendons were injured by blunt trauma using a mini guillotine, and were treated with LLLT or placebo LLLT 30 min later. The injury and LLLT procedures were then repeated 15 hours later on the same tendon. One group received active LLLT (λ = 904 nm, 60 mW mean output power, 0.158 W/cm² for 50 s, energy 3 J) and the other group received placebo LLLT 23 hours after LLLT. Ultrasonographic images were taken to measure the thickness of the right and left Achilles tendons. Animals were then killed, and all Achilles tendons were tested for ultimate tensile strength (UTS). All analyses were performed by blinded observers. There was a significant increase in tendon thickness in the active LLLT group when compared with the placebo group (p < 0.05) and there were no significant differences between the placebo and uninjured left tendons. There were no significant differences in UTS between laser-treated, placebo-treated and uninjured tendons. Laser irradiation of the Achilles tendon at 0.158 W/cm² for 50 s (3 J) administered within the first 30 min after blunt trauma, and repeated after 15 h, appears to lead to edema of the tendon measured 23 hours after LLLT. The guillotine blunt trauma model seems suitable for inflicting tendon injury and measuring the effects of treatment on edema by ultrasonography and UTS. More studies are needed to further refine this model.     

The effects of 780-nm low-level laser therapy on muscle healing process after cryolesion

The objective of this study was to assess the effects of 780-nm low-level laser therapy at different periods of 7, 14 and 21 days after cryolesion, including the dose (10 or 50 J/cm²), to promote a better muscle repair evidenced by histopathological and immunohistochemical analyses. Fifty-four male rats were divided into three groups: injured control group (CG)—injured animals without any treatment; injured 780-nm laser-treated group, at 10 J/cm² (G10); and injured 780-nm laser-treated group, at 50 J/cm² (G50). Each group was divided into three subgroups (n?=?6): 7, 14 and 21 days post-injury. Histopathological findings revealed better organised muscle fibres in the G10 and G50 during the periods of 7 and 14 days compared to the CG. The G10 and G50 during the 7 days showed a significant reduction (p?<?0.05) of lesion area compared to the CG, without differences between groups treated for 14 and 21 days. The G10 showed an increase of the amount of vessels after 14 days compared to the G50, but not in relation to controls. With regard to the immunohistochemical analyses of the MyoD factor, the G10 and G50 during the 7 days showed higher concentrations of immunomarkers than controls. Myogenin immunomarkers were similarly observed at days 7 and 14 in all the three groups analysed, whereas immunomarkers were found in none of the groups after 21 days of laser therapy. The results showed that laser, regardless the applied dose, has positive effects on muscle repair.     

Effects of low-level laser therapy (LLLT) on the nuclear factor (NF)-kappaB signaling pathway in traumatized muscle

BACKGROUND AND OBJECTIVE: To investigate the effects of low-level laser therapy (LLLT) on nuclear factor kappa B (NF-kappaB) activation and inducible nitric oxide synthase (iNOS) expression in an experimental model of muscle trauma. STUDY DESIGN/MATERIALS AND METHODS: Injury to the gastrocnemius muscle in the rat was produced by a single impact blunt trauma. A low-level galium arsenide (Ga-As) laser (904 nm, 45 mW, and 5 J/cm2) was applied for 35 seconds duration, continuously. RESULTS: Histological abnormalities with increase in collagen concentration, and oxidative stress were observed after trauma. This was accompanied by activation of NF-kappaB and upregulation of iNOS expression, whereas protein concentration of I kappa B alpha decreased. These effects were blocked by LLLT. CONCLUSION: LLLT reduced the inflammatory response induced by trauma and was able to block the effects of reactive oxygen species (ROS) release and the activation of NF-kappaB. The associated reduction of iNOS overexpression and collagen production suggest that the NF-kappaB pathway may be a signaling route involved in the pathogenesis of muscle trauma.     

Effects of the combination of low-level laser therapy and anionic polymer membranes on bone repair

Lasers in Medical Science - In view of the limitations of bone reconstruction surgeries using autologous grafts as a gold standard, tissue engineering is emerging as an alternative, which permits...     

低能量激光治疗在骨科领域的研究进展

低能量激光治疗(LLLT)可促进多种细胞的增殖和分化。例如,它可促进骨髓间充质干细胞(BMSC)向成骨细胞分化,抑制其向脂肪细胞分化,促进骨形成;促进脂肪间充质干细胞(ADSC)增殖和分化,促进生长因子的分泌;促进成骨细胞及人BMSC增殖、黏附和成骨分化;促进成纤维细胞增殖等。LLLT在骨科中常用于促进骨愈合及骨修复、改善骨质疏松、抑制炎症和缓解疼痛、促进创面愈合、治疗腕管综合征及修复脊髓损伤和周围神经损伤等。该文就LLLT在骨科领域的研究进展作一综述。     

Infrared (810-nm) low-level laser therapy on rat experimental knee inflammation

Arthritis of the knee is the most common type of joint inflammatory disorder and it is associated with pain and inflammation of the joint capsule. Few studies address the effects of the 810-nm laser in such conditions. Here we investigated the effects of low-level laser therapy (LLLT; infrared, 810-nm) in experimentally induced rat knee inflammation. Thirty male Wistar rats (230–250 g) were anesthetized and injected with carrageenan by an intra-articular route. After 6 and 12 h, all animals were killed by CO₂ inhalation and the articular cavity was washed for cellular and biochemical analysis. Articular tissue was carefully removed for real-time PCR analysis in order to evaluate COX-1 and COX-2 expression. LLLT was able to significantly inhibit the total number of leukocytes, as well as the myeloperoxidase activity with 1, 3, and 6 J (Joules) of energy. This result was corroborated by cell counting showing the reduction of polymorphonuclear cells at the inflammatory site. Vascular extravasation was significantly inhibited at the higher dose of energy of 10 J. Both COX-1 and 2 gene expression were significantly enhanced by laser irradiation while PGE₂ production was inhibited. Low-level laser therapy operating at 810 nm markedly reduced inflammatory signs of inflammation but increased COX-1 and 2 gene expression. Further studies are necessary to investigate the possible production of antiinflammatory mediators by COX enzymes induced by laser irradiation in knee inflammation.     

Effects of low-level laser therapy on soft and hard tissue healing after endodontic surgery

The aim of this prospective study was to examine possible benefits of low-level laser therapy (LLLT) on soft and hard tissue healing after endodontic surgery. Seventy-six endo-surgery cases on maxillary incisors were included. The patients were assigned randomly into control and laser groups. In the laser group, gallium-aluminum-arsenide (GaAlAs) diode laser irradiation (810 nm, 129 mW, 3.87 J/cm²) was performed immediately after surgery and daily for postoperative 7 days from buccal and palatal surfaces (5 min for each side). In the control group, patients were not subjected laser therapy. The patients were compared in terms of pain, clinical and radiological findings, and life quality indexes [Oral Health Impact Profile-14 (OHIP-14) and General Oral Health Assessment Index (GOHAI)]. Seventy-one patients completed the study (n?=?37 for control group, n?=?34 for laser group). The laser group showed better results in edema, wound healing, and the number of analgesic tablets used on the 1st, 3rd, and 7th postoperative days. Significant reduction in ecchymoses was observed in the laser group on the postop 3rd and 7th days. The patients had significantly lower pain on the 1st and 3rd postop days in laser group. The laser group showed significantly better results in OHIP-14 and GOHA indexes on postop days 1 and 3. The laser group showed significantly favorable results in terms of bone density, defect volume and area, and periapical index in the postop 3rd month. This study concluded that LLLT improved soft and hard tissue healing after endodontic surgery and also showed favorable effects on pain and life quality of patients especially in the early phase of healing period.