Low-level laser irradiation modifies the effect of hyperglycemia on adhesion molecule levels

Endothelium plays a key role in maintaining vascular homeostasis by secreting active factors involved in many biological processes such as hemostasis, angiogenesis, and inflammation. Hyperglycemia in diabetic patients causes dysfunction of endothelial cells. Soluble fractions of adhesion molecules like sE-selectin and vascular cell adhesion molecule (sVCAM) are considered as markers of endothelial damage. The low-level laser therapy (LLLT) effectively supports the conventional treatment of vascular complications in diabetes, for example hard-to-heal wounds in patients with diabetic foot syndrome. The aim of our study was to evaluate the effect of low-energy laser at the wavelength of 635 nm (visible light) and 830 nm (infrared) on the concentration of adhesion molecules: sE-selectin and sVCAM in the supernatant of endothelial cell culture of HUVEC line. Cells were cultured under high-glucose conditions of 30 mM/L. We have found an increase in sE-selectin and sVCAM levels in the supernatant of cells cultured under hyperglycemic conditions. This fact confirms detrimental influence of hyperglycemia on vascular endothelial cell cultures. LLLT can modulate the inflammation process. It leads to a decrease in sE-selectin and sVCAM concentration in the supernatant and an increase in the number of endothelial cells cultured under hyperglycemic conditions. The influence of LLLT is greater at the wavelength of 830 nm.     

Low-level infrared laser effect on plasmid DNA

Low-level laser therapy is used in the treatment of many diseases based on its biostimulative effect. However, the photobiological basis for its mechanism of action and adverse effects are not well understood. The aim of this study, using experimental models, was to evaluate the effects of laser on bacterial plasmids in alkaline agarose gel electrophoresis and Escherichia coli cultures. The electrophoretic profile of bacterial plasmids in alkaline agarose gels were used for studying lesions in DNA exposed to infrared laser. Transformation efficiency and survival of Escherichia coli AB1157 (wild-type), BH20 (fpg/mutM ^- ), BW9091 (xth^-), and DH5αF’Iq (recA ^- ) cells harboring pBSK plasmids were used as experimental models to assess the effect of laser on plasmid DNA outside and inside of cells. Data indicate low-level laser: (1) altered the electrophoretic profile of plasmids in alkaline gels at 2,500-Hz pulsed-emission mode but did not alter at continuous wave, 2.5- and 250-Hz pulsed-emission mode; (2) altered the transformation efficiency of plasmids in wild-type and fpg/mutM^- E. coli cells; (3) altered the survival fpg/mutM^-, xthA^- and recA^- E. coli cultures harboring pBSK plasmids. Low-level infrared laser with therapeutic fluencies at high frequency in pulsed-emission modes have effects on bacterial plasmids. Infrared laser action can differently affect the survival of plasmids in E. coli cells proficient and deficient in DNA repair mechanisms, therefore, laser therapy protocol should take into account fluencies, frequencies and wavelength of laser, as well as tissue conditions and genetic characteristics of cells before beginning treatment.     

Low-level (gallium-aluminum-arsenide) laser irradiation of Par-C10 cells and acinar cells of rat parotid gland

We investigated cell response, including cell proliferation and expression of heat stress protein and bcl-2, to clarify the influence of low-level [gallium-aluminum-arsenide (Ga-Al-As) diode] laser irradiation on Par-C10 cells derived from the acinar cells of rat parotid glands. Furthermore, we also investigated amylase release and cell death from irradiation in acinar cells from rat parotid glands. The number of Par-C10 cells in the laser-irradiated groups was higher than that in the non-irradiated group at days 5 and 7, and the difference was statistically significant (P < 0.01). Greater expression of heat shock protein (HSP)25 and bcl-2 was seen on days 1 and 3 in the irradiated group. Assay of the released amylase showed no significant difference statistically between the irradiated group and the non-irradiated group. Trypan blue exclusion assay revealed that there was no difference in the ratio of dead to live cells between the irradiated and the non-irradiated groups. These results suggest that low-level laser irradiation promotes cell proliferation and expression of anti-apoptosis proteins in Par-C10 cells, but it does not significantly affect amylase secretion and does not induce rapid cell death in isolated acinar cells from rat parotid glands.     

Low-level laser irradiation induces in vitro proliferation of stem cells from human exfoliated deciduous teeth

The aim of this study was to evaluate the effect of low-level laser irradiation (LLLI) on the proliferation and viability of stem cells from human exfoliated deciduous teeth (SHED). Cells were irradiated or not (control) with an InGaAlP laser diode (660 nm, 30 mW, continuous action mode) using two different energy densities (0.5 J/cm²—16 s; 1.0 J/cm²—33 s). Irradiation was performed at 0 and 48 h, with the laser probe fixed at a distance of 0.5 cm from the cells. Cell proliferation was analyzed at 0, 24, 48, and 72 h by the Trypan blue exclusion method and MTT assay. Cell cycle and Ki67 expression were analyzed by flow cytometry. Apoptosis-related events were evaluated by expression of annexin V/PI and nuclear morphological changes by staining with DAPI. Differences between groups at each time were analyzed by the Kruskal–Wallis and Mann–Whitney tests, adopting a level of significance of 5% (p < 0.05). The results showed that an energy density of 1.0 J/cm² promoted an increase in cell proliferation at 48 and 72 h compared to the control and 0.5 J/cm² groups. Cell cycle analysis revealed a predominance of cells in the S and G2/M phases in the irradiated groups. This finding was confirmed by the increased expression of Ki67. Low positive staining for annexin V and PI was observed in all groups, and no nuclear changes were detected, indicating that cell viability was not affected by the energy densities tested. It can be concluded that the LLLI parameters used (660 nm, 30 mW, 1.0 J/cm²) promote the proliferation of SHEDs and the maintenance of cell viability.     

Low-level laser irradiation (LLLI) promotes proliferation of mesenchymal and cardiac stem cells in culture

BACKGROUND AND OBJECTIVES: Low-level laser irradiation (LLLI) was found to promote the proliferation of various types of cells in vitro. Stem cells in general are of significance for implantation in regenerative medicine. The aim of the present study was to investigate the effect of LLLI on the proliferation of mesenchymal stem cells (MSCs) and cardiac stem cells (CSCs). STUDY DESIGN/MATERIALS AND METHODS: Isolation of MSCs and CSCs was performed. The cells were cultured and laser irradiation was applied at energy densities of 1 and 3 J/cm2. RESULTS: The number of MSCs and CSCs up to 2 and 4 weeks respectively, post-LLLI demonstrated a significant increase in the laser-treated cultures as compared to the control. CONCLUSION: The present study clearly demonstrates the ability of LLLI to promote proliferation of MSCs and CSCs in vitro. These results may have an important impact on regenerative medicine.     

Low-level laser irradiation modulates matrix metalloproteinase activity and gene expression in porcine aortic smooth muscle cells

BACKGROUND AND OBJECTIVES: The vascular extracellular matrix is maintained by a dynamic balance between matrix synthesis and degradation. This equilibrium is disrupted in arterial pathologies such as abdominal aortic aneurysm. Low-level laser irradiation (LLLI) promotes wound healing. However, its effect on smooth muscle cells (SMCs), a central player in these responses, has not been established. The current study was designed to determine the effects of LLLI on arterial SMC proliferation, inflammatory markers, and matrix proteins. STUDY DESIGN/MATERIALS AND METHODS: Porcine primary aortic SMCs were irradiated with a 780 nm laser diode (1 and 2 J/cm(2)). Trypan blue exclusion assay, immunofluorescent staining for collagen I and III, Sircol assay, gelatin zymography, and RT-PCR were used to monitor proliferation; collagen trihelix formation; collagen synthesis; matrix metalloproteinase-2 (MMP-2) activity, and gene expression of MMP-1, MMP-2, tissue inhibitor of MMP-1 (TIMP-1), TIMP-2, and IL-1-beta, respectively. RESULTS: LLLI-increased SMC proliferation by 16 and 22% (1 and 2 J/cm(2), respectively) compared to non-irradiated cells (P<0.01 and P<0.0005). Immediately after LLLI, trihelices of collagen I and III appeared as perinuclear fluorescent rings. Collagen synthesis was increased twofold (2 days after LLLI: 14.3+/-3.5 microg, non-irradiated control: 6.6+/-0.7 microg, and TGF-beta stimulated control: 7.1+/-1.2 microg, P<0.05), MMP-2 activity after LLLI was augmented (over non-irradiated control) by 66+/-18% (2 J/cm(2); P<0.05), and MMP-1 gene expression upregulated. However, TIMP-2 was upregulated, and MMP-2 gene expression downregulated. IL-1-beta gene expression was reduced. CONCLUSIONS: LLLI stimulates SMC proliferation, stimulates collagen synthesis, modulates the equilibrium between regulatory matrix remodeling enzymes, and inhibits pro-inflammatory IL-1-beta gene expression. These findings may be of therapeutic relevance for arterial diseases such as aneurysm where SMC depletion, weakened extracellular matrix, and an increase in pro-inflammatory markers are major pathologic components.     

Low-level 809 nm GaAlAs laser irradiation increases the proliferation rate of human laryngeal carcinoma cells in vitro

The aim of the study was to investigate the effect of low-level 809 nm laser irradiation on the proliferation rate of human larynx carcinoma cells in vitro. Epithelial tumor cells were obtained from a laryngeal carcinoma and cultured under standard conditions. For laser treatment the cells were spread on 96-well tissue culture plates. Sixty-six cell cultures were irradiated with an 809 nm GaAlAs laser. Another 66 served as controls. Power output was 10 mW(cw) and the time of exposure 75–300 s per well, corresponding to an energy fluence of 1.96–7.84 J/cm². Subsequent to laser treatment, the cultures were incubated for 72 h. The proliferation rate was determined by means of fluorescence activity of a redox indicator (Alamar Blue Assay) added to the cultures immediately after the respective treatment. The indicator is reduced by metabolic activity related to cellular growth. Proliferation was determined up to 72 h after laser application. The irradiated cells revealed a considerably higher proliferation activity. The differences were highly significant up to 72 h after irradiation (Mann–Whitney U test, p < 0.001). A cellular responsiveness of human laryngeal carcinoma cells to low-level laser irradiation is obvious. The cell line is therefore suitable for basic research investigations concerning the biological mechanisms of LLLT on cells.     

Effects of combination of melatonin and laser irradiation on ovarian cancer cells and endothelial lineage viability

The main goal of anti-cancer therapeutic approaches is to induce apoptosis in tumor masses but not in the normal tissues. Nevertheless, the combination of photodynamic irradiation with complementary oncostatic agents contributes to better therapeutic performance. Here, we applied two different cell lines; SKOV3 ovarian carcinoma cells and HUVECs umbilical cord cells as in vitro models to pinpoint whether pharmacological concentration of melatonin in combination with photodynamic therapy induces cell cytotoxicity. The cells were separately treated with various concentrations of melatonin (0 to 10 mM) and photodynamic irradiation alone or in combination. Cells were preliminary exposed to increasing concentrations of melatonin for 24 h and subsequently underwent laser irradiation for 60 s with an output power of 80 mW in continuous mode at 675 nm wavelength and a total light dose of 13.22 J/cm². Cell viability, apoptosis/necrosis rates, and reactive oxygen species levels as well as heat shock protein 70 expression were monitored after single and combined treatments. A statistical analysis was performed by applying one-way analysis of variance (ANOVA) and post hoc Tukey’s test. Combination treatment of both cell lines caused a marked increase in apoptosis/necrosis rate, reactive oxygen species generation, and heat shock protein 70 expression compared to incubation of the cells with each agent alone (p?<?0.05). SKOV3 cancer cells expressed higher level of heat shock protein 70 under experimental procedure as compared to HUVECs (p?<?0.05). Our results introduce melatonin as a potent stimulus for enhancing the efficacy of laser on induction of apoptosis in tumor cells.     

Low-level laser irradiation enhances the proliferation and osteogenic differentiation of PDLSCs via BMP signaling

Lasers in Medical Science - The aim of this in vitro study was to evaluate the effects of low-level laser therapy (LLLT) at different energy intensities on proliferation and osteogenesis of...     

The effect of low level laser irradiation on adult human adipose derived stem cells

This study investigated the effect of low level laser irradiation on primary cultures of adult human adipose derived stem cells (ADSC) using a 635-nm diode laser, at 5 J/cm(2) with a power output of 50.2 mW and a power density of 5.5 mW/cm(2). Cellular morphology did not appear to change after irradiation. Using the trypan blue exclusion test, the cellular viability of irradiated cells increased by 1% at 24 h and 1.6% at 48 h but was not statistically significant. However, the increase of cellular viability as measured by ATP luminescence was statistically significant at 48 h (p < 0.05). Proliferation of irradiated cells, measured by optical density, resulted in statistically significant increases in values compared to nonirradiated cells (p < 0.05) at both time points. Western blot analysis and immunocytochemical labeling indicated an increase in the expression of stem cell marker beta1-integrin after irradiation. These results indicate that 5 J/cm(2) of laser irradiation can positively affect human adipose stem cells by increasing cellular viability, proliferation, and expression of beta1-integrin.     

Low-level Er:YAG laser irradiation enhances osteoblast proliferation through activation of MAPK/ERK

Although the use of high-level Er:YAG laser irradiation has been increasing in periodontal and peri-implant therapy, the effects of low-level Er:YAG laser on surrounding tissues and cells remain unclear. In the present study, the effects of low-level Er:YAG laser irradiation on osteoblast proliferation were investigated. Cells of the osteoblastic cell line MC3T3-E1 were treated with low-level Er:YAG laser irradiation with various combinations of laser settings (fluence 0.7–17.2 J/cm²) and in the absence or presence of culture medium during irradiation. On day 1 and/or day 3, cell proliferation and death were determined by cell counting and by measurement of lactate dehydrogenase (LDH) levels. Further, the role of mitogen-activated protein kinase (MAPK) pathways in laser-enhanced cell proliferation was investigated by inhibiting the MAPK pathways and then measuring MAPK phosphorylation by Western blotting. Higher proliferation rates were found with various combinations of irradiation parameters on days 1 and 3. Significantly higher proliferation was also observed in laser-irradiated MC3T3-E1 cells at a fluence of approximately 1.0–15.1 J/cm², whereas no increase in LDH activity was observed. Further, low-level Er:YAG irradiation induced the phosphorylation of extracellular signal-regulated protein kinase (MAPK/ERK) 5 to 30 min after irradiation. Although MAPK/ERK 1/2 inhibitor U0126 significantly inhibited laser-enhanced cell proliferation, activation of stress-activated protein kinases/Jun N-terminal kinase (SAPK/JNK) and p38 MAPK was not clearly detected. These results suggest that low-level Er:YAG laser irradiation increases osteoblast proliferation mainly by activation of MAPK/ERK, suggesting that the Er:YAG laser may be able to promote bone healing following periodontal and peri-implant therapy.     

Low-level visible light (LLVL) irradiation promotes proliferation of mesenchymal stem cells

Low-level visible light irradiation was found to stimulate proliferation potential of various types of cells in vitro. Stem cells in general are of significance for implantation in regenerative medicine. The aim of the present study was to investigate the effect of low-level light irradiation on the proliferation of mesenchymal stem cells (MSCs). MSCs were isolated from the bone marrow, and light irradiation was applied at energy densities of 2.4, 4.8, and 7.2 J/cm². Illumination of the MSCs resulted in almost twofold increase in cell number as compared to controls. Elevated reactive oxygen species and nitric oxide production was also observed in MSCs cultures following illumination with broadband visible light. The present study clearly demonstrates the ability of broadband visible light illumination to promote proliferation of MSCs in vitro. These results may have an important impact on wound healing.     

Low-level laser irradiation facilitates fibronectin and collagen type I turnover during tooth movement in rats

The aim of this study was to investigate the effects of low-level laser (LLL) irradiation on the turnover of fibronectin and collagen type I in periodontal tissue during tooth movement in rats by immunohistochemistry. Thirty male Sprague-Dawley rats aged 15 weeks were assigned to either an experimental group (n = 15) that underwent LLL irradiation during tooth movement, or a control group (n = 15). In the experimental group, the gallium-aluminum-arsenide (Ga-Al-As) diode LLL (wavelength 808 nm; output 96 mW) was used to irradiate three areas on both the palatal side and the labial side of the maxillary incisor. The radiation was administered by the contact method for 10 s at 0.83 J/cm(2) energy dose, once a day for 7 days. Total energy dose over the complete schedule was 34.86 J/cm(2). The animals were killed on days 1, 3, 7, 14 and 21. There was no difference between the two groups in the amount of tooth movement. The immunohistochemistry results showed that the expression of fibronectin and collagen type I in the experimental group had significantly increased from day 1, with a more even distribution than in the control group, and that this difference was maintained until the end of the experiment. These results suggest that LLL irradiation facilitates the reorganization of the connective tissues during tooth movement in rats.