Background: Light‐emitting diode (LED) is attracting attention as a new light source for phototherapy. However, its effects on periodontal tissue regeneration remain unknown. The aim of this study was to examine the effects of high‐power, red LED irradiation on human periodontal ligament stem cells (PDLSCs), which play an important role in periodontal tissue regeneration.Methods: PDLSCs were derived from adult human third molars. The light source was red LED (peak wavelength: 650 nm). Energy densities ranging from 0 to 10 J/cm² were tested to determine the optimal dose. PDLSC proliferation was measured using two parameters: live cell protease and ATP levels. After the cells were induced to differentiate, the effect of LED irradiation on osteogenic differentiation and mineralization was examined, with particular focus on the extracellular signal‐regulated kinase (ERK)1/2 signaling pathway using an ERK inhibitor (PD98059).Results: LED irradiation at 8 J/cm² led to a significant increase in PDLSC proliferation and enhanced Runx2 and Osterix mRNA expression, Alkaline phosphatase activity, procollagen type I C‐peptide and osteocalcin production, calcium deposition, and alizarin red S staining. In addition, LED induced the activation of ERK1/2, and the effects of LED on PDLSC proliferation, differentiation, and mineralization could be suppressed by treatment with PD98059.Conclusions: The results of this study show that 650‐nm high‐power, red, LED irradiation increases PDLSCs proliferation, and osteogenic differentiation and mineralization, mediated by ERK1/2 activation. These findings suggest that LED may be a useful tool for periodontal tissue regeneration.

Shikonin, an active ingredient of Lithospermum erythrorhizon, exerts anti-inflammatory and antibacterial effects, and promotes wound healing. We investigated whether shikonin stimulated gingival tissue wound healing in human gingival fibroblasts (hGF). In addition, we evaluated the effects of shikonin on the mitogen-activated protein kinase (MAPK) signaling pathway, which has an important role in wound healing. hGF were subjected to primary culture using gingiva collected from patients. The cells were exposed to/treated with Shikonin at concentrations ranging from 0.01 to 100 μM. The optimal concentration was determined by cell proliferation and migration assays. Type I collagen and fibronectin synthesis, the gene expression of vascular endothelial growth factor (VEGF) and FN, and the phosphorylation of Extracellular signal-regulated kinase (ERK) 1/2 were investigated. Identical experiments were performed in the presence of PD98059 our data suggest, a specific ERK 1/2 inhibitor. Shikonin significantly promoted hGF proliferation and migration. Shikonin (1 µM) was chosen as the optimal concentration. Shikonin promoted type I collagen and FN synthesis, increased VEGF and FN expression, and induced ERK 1/2 phosphorylation. These changes were partially suppressed by PD98059. In conclusion, Shikonin promoted the proliferation, migration, type I collagen and FN synthesis, and expression of VEGF and FN via ERK 1/2 signaling pathway in hGFs. Therefore, shikonin may promote periodontal tissue wound healing.

Human gingival fibroblasts (HGnFs) maintain periodontal tissue homeostasis through active proliferation and migration. Clinically, it is considered that the wound-healing ability of the gingival tissue is maintained even in environments with insufficient supply of nutrients, such as glucose, immediately after periodontal surgery. However, the effects of such glucose-deficient environments on HGnFs remain unclear. This study aimed to investigate the effects of low-glucose environment on HGnFs homeostasis. We evaluated gingival wound healing by examining cell proliferation and migration and collagen synthesis in HGnFs cultured in 100, 50, 25, and 0 mg/dL glucose in vitro. The cellular stress levels were determined by measuring the lactate dehydrogenase (LDH) and reactive oxygen species (ROS) levels. The glucose metabolism of HGnFs in the low-glucose concentrations was studied by measuring glucose transporter type 1 (GLUT1) mRNA expression, glucose uptake assays, lactate and ATP productions. Molecular effects were examined with a focus on the LKB1-AMPK signaling pathway. Autophagy activity in glucose-deprived HGnFs was evaluated by measuring the levels of autophagy-related proteins. Low glucose levels increased cellular stress levels, autophagy activity, and enhanced glucose metabolism through the LKB1-AMPK signaling pathway, providing more ATPs to promote wound healing. Our results regarding glucose transfer suggest the rapid healing of gingival wounds.

Gingival tissue experiences an environment of nutrient shortage, such as low glucose conditions, after periodontal surgery. Our previous studies found that this low glucose condition inhibits normal gingival cell functions. However, the mechanism by which this glucose-deficient environment causes cellular damage to human gingival fibroblasts (HGnFs) remains unclear. This study aimed to investigate the biological effects of ROS induction on HGnFs under low glucose conditions. ROS levels and cellular anti-ROS ability of HGnFs under different glucose concentrations were evaluated by measuring ROS formation and the expression of superoxide dismutase and heme oxygenase 1. Changes in cellular viability were investigated using 5-bromo-2′-deoxyuridine assay and cell survival detection, and the cellular damage was evaluated by the expression of inflammatory cytokines and changes in the expression of autophagy-related protein. ROS formation was then blocked using N-acetyl-L-cysteine (NAC), and the effects of ROS on HGnFs under low glucose conditions were investigated. Low glucose conditions induced ROS accumulation, reduced cellular activity, and induced inflammation and autophagy. After NAC application, the anti-ROS capacity increased, cellular activity improved, and inflammation and autophagy were controlled. This can be effectively controlled by the application of antioxidants such as NAC.