Effects of near-infrared low-level laser irradiation on microcirculation

BACKGROUND AND OBJECTIVE: Recently, there has been an increase in the clinical application of low-level laser irradiation (LLLI) in various fields. The present study was conducted to explore the effects of LLLI on microcirculation. STUDY DESIGN/MATERIAL AND METHODS: We investigated the effects of LLLI on rat mesenteric microcirculation in vivo, and on cytosolic calcium concentration ([Ca2+]i) in rat vascular smooth muscle cells (VSMCs) in vitro. RESULTS: LLLI caused potent dilation in the laser-irradiated arteriole, which led to marked increases in the arteriolar blood flow. The changes were partly attenuated in the initial phase by the superfusion of 15 microM L-NAME, but they were not affected by local denervation. Furthermore, LLLI caused a power-dependent decrease in [Ca2+]i in VSMCs. CONCLUSION: The circulatory changes observed seemed to be mediated largely by LLLI-induced reduction of [Ca2+]i in VSMCs, in addition to the involvement of NO in the initial phase.     

低能激光照射对大鼠梗死后心肌组织的影响

目的 观察低能激光照射(LLLI)对大鼠梗死后心肌组织的影响.方法 冠状动脉结扎法制作雌性SD大鼠心肌梗死模型,3周后,经超声筛选合格心肌梗死大鼠随机分为两组:(1)低能激光照射组(LLLI组);(2)对照组(Control组);另设假手术组(Sham组).LLLI组应用低能激光开胸单次照射后,以逆转录-聚合酶链反应(RT-PCR)法和Western blot法检测LLLI处理区内心肌组织中血管内皮生长因子(VEGF)的表达,照射后1h、1d、1周,分别测定LLLI处理区内心肌组织中超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量.结果 与Control组VEGF mRNA和蛋白的表达(2.12 ±0.58、1.02±0.41)及Sham组VEGF mRNA和蛋白的表达(2.42±0.26、0.92±0.37)比较,LLLI组显著提高了照射区域梗死后心肌组织中VEGF mRNA和蛋白的表达(4.42±2.88、2.62±1.83,P ＜0.05);Sham组与Control组之间比较差异无统计学意义(P＞0.05).在预处理后1h和1d,与Control组比较,LLLI组梗死后心肌组织中SOD的活性[(0.84±0.43)、(0.92±0.34) U/mg)]均显著提高;而MDA的产量[(0.56±0.31)、(0.50 ±0.29) nmol/mg]显著降低(P＜0.05).在预处理后1周,LLLI组与Control组之间上述指标差异无统计学意义(P＞0.05).结论 LLLI处理显著上调梗死后心肌组织中VEGF的表达及SOD的活性,降低了MDA的含量,从而能够改善梗死后心肌微环境,促进梗死后心肌细胞的再生与修复.     

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.     

Study on the selection of laser wavelengths in the intravascular low-level laser irradiation therapy

According to the absorption spectra of blood and hemoglobin, a photon-bond energy formula is established using physical methods and the effects on hemoglobin of low-level laser at different wavelengths are analyzed. The results show that lasers with the peak wavelengths of 200～240, 275, and 342 nm in the whole blood absorption spectra curve are easy to destroy protein molecules and then lead to hemoglobin lose biological activity. While lasers with wavelengths longer than 800 nm will reduce the oxygen carrying capacity of blood, only lasers with wavelengths between 630 and 670 nm have the best efficacy.     

The effects of low-level laser irradiation on bone tissue in diabetic rats

Diabetes mellitus (DM) leads to a decrease in bone mass and increase the risk of osteoporosis and in this context, many treatments have shown to accelerate bone metabolism. It seems that low-level laser therapy (LLLT) is able of stimulating osteoblast activity and produced increased biomechanical properties. However, its effects on bone in diabetic rats are not fully elucidated. The aim of this study was to evaluate the effects of LLLT on bone formation, immunoexpression of osteogenic factors, biomechanical properties and densitometric parameters in diabetic rats. Thirty male Wistar rats were randomly distributed into three experimental groups: control group, diabetic group, and laser-treated diabetic group. DM was induced by streptozotocin (STZ) and after 1 week laser treatment started. An 830-nm laser was used, performed for 18 sessions, during 6 weeks. At the end of the experiment, animals were euthanized and tibias and femurs were defleshed for analysis. Extensive resorptive areas as a result of osteoclasts activity were noticed in DG when compared to control. Laser-treated animals showed an increased cortical area. The immunohistochemical analysis revealed that LLLT produced an increased RUNX-2 expression compared to other groups. Similar RANK-L immunoexpression was observed for all experimental groups. In addition, laser irradiation produced a statistically increase in fracture force, bone mineral content (BMC) and bone mineral density compared to DG. The results of this study indicate that the STZ model was efficient in inducing DM 1 and producing a decrease in cortical diameter, biomechanical properties and in densitometric variables. In addition, it seems that LLLT stimulated bone metabolism, decreased resorptive areas, increased RUNX-2 expression, cortical area, fracture force, BMD, and BMC. Further studies should be developed to provide additional information concerning the mechanisms of action of laser therapy in diabetic bone in experimental and clinical trials.     

The effect of low-level laser irradiation on dog spermatozoa motility is dependent on laser output power

Biological tissues respond to low-level laser irradiation and so do dog spermatozoa. Among the main parameters to be considered when a biological tissue is irradiated is the output power. We have studied the effects on sperm motility of 655 nm continuous wave diode laser irradiation at different output powers with 3.34 J (5.97 J/cm²). The second fraction of fresh dog sperm was divided into five groups: control, and four to be irradiated with an average output power of 6.8 mW, 15.4 mW, 33.1 mW and 49.7 mW, respectively. At 0 min and 45 min after irradiation, pictures were taken and a computer aided sperm analysis (CASA) performed to analyse different motility parameters. The results showed that different output powers affected dog semen motility parameters differently. The highest output power showed the most intense effects. Significant changes in the structure of the motile sperm subpopulation were linked to the different output powers used.     

Histomorphologic and ultrastructural recovery of myopathy in rats treated with low-level laser therapy

The purpose of the present work was to study the effect of low-level laser therapy (LLLT): helium-neon (He-Ne) and gallium arsenide (Ga-As) laser on the histomorphology of muscle and mitochondria in experimental myopathy in rats. Thirty Suquía strain female rats were distributed in groups: (A) control (intact), (B) injured, (C) injured and treated with He-Ne laser, (D) injured and treated with Ga-As laser, (E) irradiated with He-Ne laser on the non-injured muscle, and (F) irradiated with Ga-As laser on the non-injured muscle. Myopathy was induced by injecting 0.05 mg/rat/day of adrenaline in the left gastrocnemius muscle at the same point on five consecutive days, in groups B, C, and D. LLLT was applied with 9.5 J cm^?2 daily for seven consecutive days in groups C, D, E, and F. The muscles were examined with optic and electronic microscopy. The inflammation was classified as absent, mild, and intense and the degree of mitochondrial alteration was graded I, II, III, and IV. Categorical data were statistically analyzed by Chi-square and the Fisher-Irwin Bilateral test, setting significant difference at p?<?0.05. The damage found in muscle and mitochondria histomorphology in animals with induced myopathy (B) was intense or severe inflammation with grade III or IV of mitochondrial alteration. They underwent significant regression (p?<?0.001) compared with the groups treated with He-Ne (C) and Ga-As (D) laser, in which mild or moderate inflammation was seen and mitochondrial alteration grades I and II, recovering normal myofibrillar architecture. No differences were found between the effects caused by the two lasers, or between groups A, E, and F. Group A was found to be different from B, C, and D (p?<?0.001). LLLT in experimental myopathy caused significant muscular and mitochondrial morphologic recovery.     

Effect of low-level laser irradiation and epidermal growth factor on adult human adipose-derived stem cells

The study investigated the effects of low-level laser radiation and epidermal growth factor (EGF) on adult adipose-derived stem cells (ADSCs) isolated from human adipose tissue. Isolated cells were cultured to semi-confluence, and the monolayers of ADSCs were exposed to low-level laser at 5 J/cm² using 636 nm diode laser. Cell viability and proliferation were monitored using adenosine triphosphate (ATP) luminescence and optical density at 0 h, 24 h and 48 h after irradiation. Application of low-level laser irradiation at 5 J/cm² on human ADSCs cultured with EGF increased the viability and proliferation of these cells. The results indicate that low-level laser irradiation in combination with EGF enhances the proliferation and maintenance of ADSCs in vitro.     

Effects of increased low-level diode laser irradiation time on extraction socket healing in rats

Lasers in Medical Science - In our previous studies, we confirmed that low-level laser therapy (LLLT) with a 980-nm gallium–aluminum–arsenide diode laser was beneficial for the healing...     

Effect of low-level laser irradiation on cytotoxicity of benzene in human normal fibroblast cells

Lasers in Medical Science - Benzene is volatile organic hydrocarbon which is widely used in a wide range of industries. Studies have shown that exposure to benzene consequences serious health risks...     

Effects of low-level laser irradiation on mesenchymal stem cell proliferation: a microarray analysis

Increased proliferation after low-level laser irradiation (LLLI) has been well demonstrated in many cell types including mesenchymal stem cells (MSCs), but the exact molecular mechanisms involved remain poorly understood. The aim of this study was to investigate the change in mRNA expression in rat MSCs after LLLI and to reveal the associated molecular mechanisms. MSCs were exposed to a diode laser (635 nm) as the irradiated group. Cells undergoing the same procedure without LLLI served as the control group. Proliferation was evaluated using the MTS assay. Differences in the gene expression profiles between irradiated and control MSCs at 4 days after LLLI were analyzed using a cDNA microarray. Gene ontology and pathway analysis were used to find the key regulating genes followed by real-time PCR to validate seven representative genes from the microarray assays. This procedure identified 119 differentially expressed genes. Real-time PCR confirmed that the expression levels of v-akt murine thymoma viral oncogene homolog 1 (Akt1), the cyclin D1 gene (Ccnd1) and the phosphatidylinositol 3-kinase, catalytic alpha polypeptide gene (Pik3ca) were upregulated after LLLI, whereas those of protein tyrosine phosphatase non-receptor type 6 (Ptpn6) and serine/threonine kinase 17b (Stk17b) were downregulated. cDNA microarray analysis revealed that after LLLI the expression levels of various genes involved in cell proliferation, apoptosis and the cell cycle were affected. Five genes, including Akt1, Ptpn6, Stk17b, Ccnd1 and Pik3ca, were confirmed and the PI3K/Akt/mTOR/eIF4E pathway was identified as possibly playing an important role in mediating the effects of LLLI on the proliferation of MSCs.     

In vitro effects of low-level laser irradiation at 660 nm on peripheral blood lymphocytes

BACKGROUND AND OBJECTIVE:The effects of low-level laser light irradiation are still highly contested, and the mechanisms of its action still unclear. This study was conducted to test the effects of low-level laser irradiation at 660 nm on human lymphocytes and to investigate the possible mechanisms by which these effects are produced. STUDY DESIGN/MATERIALS AND METHODS: Whole blood obtained by phlebotomy was irradiated at 660 nm by using energy fluences between 0 and 5.0 J/cm(2). The lymphocytes were isolated after irradiation of the whole blood. For the control experiment, the lymphocytes were first isolated and then irradiated at the same wavelength and energy fluence for comparison. The proliferation of lymphocytes and the formation of free radicals and lipid peroxides were monitored. Hemoglobin was also irradiated in a cell-free environment to test for the production of lipid peroxides. RESULTS: Lymphocyte proliferation was significantly higher (P<0.05) as expressed by a Stimulation Index in samples irradiated in the presence of whole blood compared with lymphocytes irradiated after isolation from whole blood. Free radical and lipid peroxide production also increased significantly when samples were irradiated in the presence of red blood cells. CONCLUSION: The present study supports the hypothesis that one mechanism for the photobiostimulation effect after irradiation at 660 nm is the reaction of light with hemoglobin, resulting in oxygen radical production.     

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.     

Stability of dental implants after irradiation with an 830-nm low-level laser: a double-blind randomized clinical study

Little is known about the benefits of low-level laser therapy (LLLT) on improvement of stability of dental implants. The aim of this randomized clinical study was to assess the LLLT effect on implants stability by means of resonance frequency analysis (RFA). Thirty implants were distributed bilaterally in the posterior mandible of eight patients. At the experimental side, the implants were submitted to LLLT (830?nm, 86?mW, 92.1?J/cm², 0.25?J, 3?s/point, at 20 points), and on the control side, the irradiation was simulated (placebo). The first irradiation was performed in the immediate postoperative period, and it was repeated every 48?h in the first 14?days. The initial implant stability quotient (ISQ) of the implants was measured by means of RFA. New ISQ measurements were made after 10?days, 3, 6, 9, and 12?weeks. The initial ISQ values ranged from 65–84, with a mean of 76, undergoing a significant drop in stability from the 10th day to the 6th week in the irradiated group, and presenting a gradual increase from the 6th to the 12th week. The highest ISQ values were observed on the 10th day in the irradiated group, and the lowest in the 6th week in both groups. Under the conditions of this study, no evidence was found of any effect of LLLT on the stability of the implants when measured by RFA. Since high primary stability and good bone quality are of major relevancy for a rigid bone–implant interface, additional LLLT may have little impact macroscopically.     

Effect of GaAlAs low-level laser therapy on mouth opening after orthognathic surgery

To evaluate low-level laser therapy (LLLT) as an adjunct to enhance postoperative mouth opening after orthognathic surgery. Prospective clinical trial of 82 patients allocated into an intervention group (laser, LG) and a control group (no laser, CG) and subgroups according to the procedure type : (1) surgically assisted rapid maxillary expansion (SARME); (2) maxillary surgery; (3) mandibular surgery; or (4) bimaxillary surgery. LG patients received LLLT immediately after surgery and every 24 h thereafter for 3 days, using a gallium–aluminum–arsenide (GaAlAs) diode laser (780 nm, 28 spots, 14 on each side of the face, output power 2 J/spot). Maximum mouth opening was measured using digital calipers at five time points: preoperative baseline and postoperative days 2, 7, 14, and 21. ANOVA was used to evaluate difference in mouth opening across groups. Significance was accepted at P??≤??0.05. Final average mouth opening differed between women (GL1?=?94.24%, GC1?=?89.54%, GL2?=?69.39%; GC2?=?68.46%; GL3?=?65.11%; GC3?=?58.64%; GL4?=?61.85%; GC4?=?57.11%) and men (GL1?=?86.92%, GC1?=?102.44%, GL2?=?77.56%; GC2?=?81.65%; GL3?=?80.29%; GC3?=?67.63%; GL4?=?66.93%; GC4?=?55.31%). There were no significant differences between the SARME and isolated maxillary/mandibular surgery groups. In the bimaxillary groups, average mouth opening was increased in all patients who received LLLT, significantly so in male patients. LLLT with a GaAlAs diode laser (780 nm) did not affect postoperative mouth opening after SARME, isolated maxillary surgery, or isolated mandibular surgery. However, it improved mouth opening in men who had undergone bimaxillary orthognathic surgery.