The effect of low-level laser irradiation on hyperglycemia-induced inflammation in human gingival fibroblasts.

Hyperglycemia-induced inflammation can greatly increase the risk of periodontal disease in people with diabetes. Low-level laser irradiation (LLLI) has been used for wound healing and anti-inflammation in many cases, and LLLI is known to inhibit the lipopolysaccharide (LPS)-stimulated inflammatory response. However, the therapeutic effect of LLLI in diabetes patients with periodontitis remains unknown. In this study, we cultured human gingival fibroblasts (HGFs) in high-glucose medium (35 mM) to mimic a hyperglycemic environment, and then measured the anti-inflammatory effect of LLLI by assessing the expression of pro-inflammatory genes including tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6, and IL-8 by quantitative real-time polymerase chain reaction. The results demonstrated no significant inflammatory response in HGFs cultured in mannitol medium and in those treated only with LLLI. However, HGFs cultured only in high-glucose medium showed significantly higher expression of pro-inflammatory cytokine than in those treated together with LLLI. We then observed that LLLI reduced the expression of pro-inflammatory cytokines in HGFs cultured in high-glucose medium by modulating cAMP signaling. We also investigated whether antioxidant (vitamin C) treatment reduced the inflammatory effect of oxidative stress in HGFs cultured in high-glucose medium but found no additive effect upon co-treatment with LLLI, suggesting that LLLI may activate cAMP signaling, but not reactive oxygen species (ROS) signaling, to reduce the high glucose-induced inflammation. In conclusion, LLLI may have an anti-inflammatory effect on HGFs in a high glucose environment and may benefit the treatment of periodontal disease in diabetes patients.

Anti-inflammatory effects of low-level laser therapy on human periodontal ligament cells: in vitro study.

Periodontal disease is a chronic inflammatory disease that is commonly treated with surgical and nonsurgical techniques. However, both approaches have limitations. Low-level laser therapy (LLLT) has been widely applied in reducing inflammatory reactions, and research indicates that LLLT induces an anti-inflammatory effect that may enhance periodontal disease therapy. The purpose of this study was to investigate the anti-inflammatory effect of LLLT on human periodontal ligament cells (hPDLCs) in an inflammatory environment and aimed to determine the possible mechanism of action. Cells were cultured and treated with or without lipopolysaccharide (LPS) from Porphryromonas gingivalis or Escherichia coli, followed by irradiation with a gallium-aluminum-arsenide (GaAlAs) laser (660 nm) at an energy density of 8 J/cm2. Quantitative real-time polymerase chain reactions were used to assess the expression of pro-inflammatory genes, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6, and IL-8. The dual-luciferase reporter assay was used to examine nuclear factor-κB (NF-κB) transcriptional activity. An enzyme-linked immunosorbent assay was used to monitor the concentration of intracellular cyclic adenosine monophosphate (cAMP). Both LPS treatments significantly induced the mRNA expression of pro-inflammatory cytokines. However, LLLT inhibited the LPS-induced pro-inflammatory cytokine expression and elevated intracellular levels of cAMP. The LLLT inhibitory effect may function by downregulating NF-κB transcriptional activity and by increasing the intracellular levels of cAMP. LLLT might inhibit LPS-induced inflammation in hPDLCs through cAMP/NF-κB regulation. These results should be further studied to improve periodontal therapy.

Low power laser irradiation and human adipose-derived stem cell treatments promote bone regeneration in critical-sized calvarial defects in rats.

Both stem cell therapy and physical treatments have been shown to be beneficial in accelerating bone healing. However, the efficacy of combined treatment with stem cells and physical stimuli for large bone defects remains uncertain. The aim of this study was to evaluate the bone regeneration effects of low-power laser irradiation (LPLI) and human adipose-derived stem cell (ADSC) treatments during fracture repair using a comparative rat calvarial defect model. We evaluated the viability of human ADSCs, which were cultured on a porous PLGA scaffold using an MTS assay. The critical-sized calvarial bone defect rats were divided into 4 groups: control group, LPLI group, ADSC group, and ADSC+LPLI group. Bone formation was evaluated using micro-CT. New bone formation areas and osteogenic factor expression levels were then examined by histomorphological analysis and immunohistochemical staining. Our data showed that PLGA had no cytotoxic effect on human ADSCs. Micro-CT analyses revealed that both the LPLI and ADSC groups showed improved calvarial bone defect healing compared to the control group. In addition, the ADSC+LPLI group showed significantly increased bone volume at 16 weeks after surgery. The area of new bone formation ranked as follows: control group < LPLI group < ADSC group < ADSC+LPLI group. There were significant differences between the groups. In addition, both ADSC and ADSC+LPLI groups showed strong signals of vWF expression. ADSC and LPLI treatments improved fracture repair in critical-sized calvarial defects in rats. Importantly, the combined treatment of ADSCs and LPLI further enhances the bone healing process.

Low-power laser irradiation inhibits arecoline-induced fibrosis: an in vitro study.

Oral submucous fibrosis (OSF) is a potentially malignant disorder that is characterized by a progressive fibrosis in the oral submucosa. Arecoline, an alkaloid compound of the areca nut, is reported to be a major aetiological factor in the development of OSF. Low-power laser irradiation (LPLI) has been reported to be beneficial in fibrosis prevention in different damaged organs. The aim of this study was to investigate the potential therapeutic effects of LPLI on arecoline-induced fibrosis. Arecoline-stimulated human gingival fibroblasts (HGFs) were treated with or without LPLI. The expression levels of the fibrotic marker genes alpha-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF/CCN2) were analysed by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) and western blots. In addition, the transcriptional activity of CCN2 was further determined by a reporter assay. The results indicated that arecoline increased the messenger RNA and protein expression of CCN2 and α-SMA in HGF. Interestingly, both LPLI and forskolin, an adenylyl cyclase activator, reduced the expression of arecoline-mediated fibrotic marker genes and inhibited the transcriptional activity of CCN2. Moreover, pretreatment with SQ22536, an adenylyl cyclase inhibitor, blocked LPLI's inhibition of the expression of arecoline-mediated fibrotic marker genes. Our data suggest that LPLI may inhibit the expression of arecoline-mediated fibrotic marker genes via the cAMP signalling pathway.