Photobiomodulatory effect delivered by low-level laser on dental pulp stem cell differentiation for osteogenic lineage

Background: Photobiomodulation (PBM) therapy has attracted major interest in the field of tissue engineering as it can enhance stem cell differentiation. It has been shown that PBM therapy can stimulate differentiation of cells in culture by exerting biomodulatory effect. Recent evidences show that PBM therapy can positively modulate dental pulp stem cell (DPSC) properties. Combination of PBM therapy with growth factors and biomaterials can possibly accelerate osteogenic differentiation of dental pulp stem cells. Aims: To evaluate the biomodulatory effect of low-level laser dose on dental pulp stem cells in the presence of hydroxyapatite-based scaffold particle for osteogenic differentiation. Materials and methods: DPSCs were harvested from human premolar teeth and expanded using mesenchymal stem cell medium. Characterization of DPSCs was done using fluorescence-activated cell sorting with CD105, CD44, CD34, and CD45 markers. Cultured DPSCs along with the N-acetylcysteine-labeled hydroxyapatite (NAC-HA) particles and osteogenic differentiation media were exposed to gallium-aluminum-arsenide (Ga-Al-As) diode laser at 810 nm. Cells were divided into 3 groups: L1 (single exposure), L2 (double exposure), and control (no exposure). Osteodifferentiation after PBM therapy was assessed using Alizarin red S staining, Alkaline phosphatase activity (ALP), and by osteopontin expression. Differences between groups at each time point were analyzed using the Mann–Whitney U test. A level of significance of 5% was adopted (p < 0.05). Results: DPSCs grown on NAC-HA polymers show increased cell adhesion and proliferation. Double irradiated groups were consistent with increased calcium (71%) and alkaline phosphatase activity (75%) when compared with single-irradiated groups. mRNA expression of osteopontin was relatively increased in a significant (p < 0.001) manner in L2 when compared with L1 group. Alizarin red S and ALP positive staining confirmed the presence of calcium deposition in the test samples. The osteopontin expression of L2 (216.681) as compared with L1 (123.276) group prove the efficacy of double exposures over a single dose of PBM therapy. Conclusion: The result envisages the enhanced osteogenic potential of PBM therapy on the differentiation of DPSCs in NAC-HA scaffolds. Double exposure of PBM therapy expresses better biomodulatory effect on DPSCs as compared with the single dose. © 2019, Springer Nature Switzerland AG.