Objective: To explore the effects of red LEDs on the proliferation and osteogenic differentiation of human stem cells from apical papilla (hSCAPs). Methods: hSCAPs were obtained by isolation, culture and flow cytometry in vitro and irradiated with 1, 3, 5, and 7 J/cm2 red LEDs. The proliferation of hSCAPs was detected using a CCK-8 assay. The osteogenic differentiation of hSCAPs was evaluated using alkaline phosphatase (ALP) staining, ALP activity assay and Alizarin red quantitative detection. The effect of 5 J/cm2 red LEDs on the expression levels of the ALP, Runx2, OCN, OPN and BSP genes and proteins was detected by RT-PCR and western blot, respectively. Results: Red LEDs at 1, 3, 5, and 7 J/cm2 promoted the proliferation of hSCAPs (P < 0.05). The effects of red LEDs with different light energies on the proliferation of hSCAPs were different at different time points (P < 0.05). On the 7th and 14th days after irradiation, red LEDs promoted the osteogenic differentiation of hSCAPs, and the effect of 5 J/cm2 red LEDs was the most obvious under osteogenic induction culture conditions (P<0.05). Red LEDs (5 J/cm2) promoted the expression of the ALP, Runx2, OCN, OPN and BSP genes and proteins (P < 0.05). Conclusion Red LEDs promoted the proliferation and osteogenic differentiation of hSCAPs.

Objective : To study the effect of light-emitting diode (LED) red light on the osteogenic/odontogenic differentiation of human dental pulp stem cells (hDPSCs) and its mechanism were discussed. Methods: This study has been reviewed and approved by the Ethics Committee. hDPSCs were cultured by tissue block enzyme digestion. The proliferative capacity of hDPSCs was detected by the CCK-8 at days 1, 3, 5 and 7 under stimulation with 0, 1, 5 and 10 μg/mL lipopolysaccharide (LPS), and the LPS stimulatory concentration was screened. The CG group (mineralization induction), LPS+CG group, and LPS+CG+ (2, 4, 6, 8, and 10 J/cm2) LED red light groups were set. On day 7, alkaline phosphatase (ALP) staining and ALP activity were determined. Relative expression levels of the ALP, osterix (OSX), dentin matrix protein-1 (DMP-1) and dentin sialophosphoprotein (DSPP) genes were measured by qRT-PCR. On day 21, alizarin red staining and calcium nodule quantitative determination were performed to screen the best light energy. The LPS+CG group and LPS+CG+LED group (optimal energy) were set up, and the secretion and expression levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were detected by ELISAs on days 1, 3, 5 and 7. The relative expression levels of the extracellular regulated protein kinases 1/2 (ERK1/2), p38, c-Jun N-terminal kinase (JNK), and extracellular regulated protein kinases 5 (ERK5) proteins and their phosphorylated proteins in the MAPK signaling pathway were detected by Western blots. After the pathway was blocked, the relative expression levels of the ALP, OSX, DMP-1, and DSPP proteins after LED red light irradiation on day 7 were detected by Western blots. Results: CCK-8 assays showed that the proliferation of hDPSCs induced by 10 μg/mL LPS was lower than that of the 0, 1, and 5 μg/mL groups on the 5th and 7th days (P<0.05), and 10 μg/mL was selected as the LPS stimulatory concentration in the follow-up experiment. ALP staining, ALP activity, gene expression levels of ALP, OSX, DMP-1 and DSPP and calcium nodule quantification in the LPS+CG+4 J/cm2 group were higher than those in the other treatment groups (P<0.05). 4 J/cm2 LED red light had the strongest ability to promote osteogenic/odontogenic differentiation and was used as the LED light energy density in subsequent experiments. ELISA showed that the secretion and expression levels of TNF-α and IL-1β in the LPS+CG+LED group were lower than those in the LPS+CG group on the 5th and 7th days (P<0.05). Western blot analysis showed that 4 J/cm2 LED red light promoted the expression levels of the p-ERK1/2, p-p38, p-JNK and p-ERK5 proteins. After the MAPK pathway was blocked, the expression levels of the ALP, OSX, DMP-1, and DSPP proteins in the LPS+CG+LED+U0126 (ERK1/2 inhibitor), SP600125 (JNK inhibitor), and BIX02189 (ERK5 inhibitor) groups were lower than those in the LPS+CG+LED group (P<0.001). The protein expression levels of ALP, OSX and DMP-1 in the LPS+CG+LED+SB203580 (p38 inhibitor) group were not significantly different from those in the LPS+CG+LED group (P>0.05). Conclusion In inflammatory conditions, LED red light promotes osteogenic/odontogenic differentiation of hDPSCs. This effect may be attributed to enhancement of the ERK1/2, JNK, and ERK5 signaling pathways, which reduces the production of the inflammatory cytokines TNF-α and IL-1β.

Objective: To explore the effects of red LED light mediated by the Kelch-like ECH-associated protein 1-nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (KEAP1-NRF2/HO-1) pathway on osteogenic differentiation and oxidative stress damage of human periodontal ligament stem cells (hPDLSCs) induced by high glucose, which provides a basis for the application of red light-emitting diode (LED) light in cell antioxidative damage. Methods: hPDLSCs were identified by flow cytometric analysis, alkaline phosphatase (ALP) staining and Alizarin red-S staining; hPDLSCs were pretreated in a high glucose environment for 48 hours and irradiated with 1, 3, or 5 J/cm2 red LED light. A CCK-8 assay was performed to choose the radiant exposure that had the strongest effect on promoting the cell proliferation rate for subsequent experiments. hPDLSCs were divided into a control group, a high glucose group and a high glucose+light exposure group. ALP staining, ALP activity, Alizarin red-S staining and quantitative calcified nodules were used to detect the osteogenic differentiation of hPDLSCs; qRT-PCR and Western blot were used to detect the gene and protein expression levels of ALP, runt-related transcription factor 2 (RUNX2) and osterix (OSX); the relative mRNA expression levels of antioxidant enzyme-related genes superoxide dismutase 2 (SOD2) and catalase (CAT) in hPDLSCs were detected by qRT-PCR; reactive oxygen species (ROS) levels were detected by fluorescence microscopy and flow cytometry; the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) levels in cell supernatants were detected by ELISA; the NRF2-specific inhibitor ML385 was used to inhibit the NRF2 pathway; ALP staining and ALP activity were used to detect the markers of early osteogenic differentiation; qRT-PCR was used to detect the gene expression of ALP, RUNX2 and OSX; and the protein expression levels of KEAP1, NRF2 and HO-1 were detected by Western blot. Results : Identified, and irradiant exposure of 5 J/cm2 was chosen for subsequent experiments. Red LED light irradiation (5 J/cm2) improved the osteogenic differentiation of hPDLSCs induced by high glucose (P<0.05), increased the mRNA and protein levels of ALP, RUNX2 and OSX (P<0.05), upregulated the mRNA expression levels of SOD2 and CAT (P<0.05), reduced the levels of ROS (P<0.05), and reduced TNF-α and IL-1β levels in the cell supernatants (P<0.05). When ML385 was added to inhibit the NRF2 pathway, the ALP activity of cells was decreased (P<0.05); the gene expression levels of ALP, RUNX2 and OSX were downregulated (P<0.05); the protein level of KEAP1 was upregulated (P<0.05); and the protein levels of NRF2 and HO-1 were downregulated (P<0.05) Conclusion Red LED light may promote the proliferation and osteoblastic differentiation of hPDLSCs induced by high glucose through the KEAP1-NRF2/HO-1 pathway and reduce the oxidative stress damage to hPDLSCs induced by high glucose.