Impact of Photobiomodulation on the Pro-Osteogenic Activity of Dental Pulp Mesenchymal Stem/Stromal Cells

Photobiomodulation (PBM) consists of applying low-level laser light to biological tissues, leading to modulation of cellular functions. PBM has recently gained much attention in the field of regenerative dentistry thanks to its powerful effect on tissue repair and regeneration. Dental pulp mesenchymal stem/stromal cells (DP-MSCs) represent the ideal targets in regenerative dentistry due to their ability to stimulate the regeneration of mineralized and soft tissues and the paracrine factors that they produce. Although there have been several studies evaluating the influence of PBM on DP-MSCs' regenerative capacity, the results are conflicting, and there are few studies on the influence of PBM on the paracrine factors released by DP-MSCs. Therefore, the aim of this study was to investigate the effect of PBM, using different energy doses of laser irradiation, on the osteogenic capacity of DP-MSCs, focusing on changes in gene expression, mineralizing ability, and release of pro-osteogenic factors. DP-MSCs were irradiated in vitro and differentiated into an osteogenic phenotype. A cell viability assay, alizarin red staining, and TEM analysis were carried out to evaluate the effect of PBM on cell activity, morphology, and mineralization ability. The expression of the main osteogenesis-related markers Runx2, Col1A1, ALP, and BMP was measured to evaluate the influence of PBM on the ability of DP-MSCs to differentiate toward an osteogenic phenotype. The release of IL-6 and IL-8, which are mainly involved in bone remodeling processes, was investigated in the cell medium following PBM irradiation. The results showed a high level of cell viability, suggesting a lack of phototoxicity under the tested conditions. Furthermore, PBM had a significant effect on mineral deposition, IL-6 and IL-8 release, and expression of osteogenic markers. TEM analysis showed intracellular modifications linked mainly to mitochondria, the endoplasmic reticulum, and autophagic vesicles after PBM treatment. These findings demonstrated that the impact of PBM on the osteogenic potential of DP-MSCs is energy dose-dependent, supporting its potential as an effective strategy in regenerative dentistry, particularly for enhancing bone remodeling.