Effects of green light photobiomodulation on Dental Pulp Stem Cells: enhanced proliferation and improved wound healingby cytoskeleton reorganization and cell softening
Résumé
Photobiomodulation (PBM) has been shown to improve cell proliferation and cell migration. Many cell types have been
investigated, with most studies using deep penetrating red light irradiation. Considering the interest of surface biostimulation
of oral mesenchymal cells after surgical wound, the present study aimed to assess green light irradiation effects on Dental Pulp
Stem Cells’ (DPSC) proliferation and migration. To understand the mechanisms underlying these effects, we investigated
cytoskeleton organization and subsequent cell shape and stiffness.
A 532-nm wavelength Nd:YAG laser (30 mW) was applied
between 30 and 600 s on DPSC in vitro. Cell proliferation was analyzed at 24, 48, and 72 h after irradiation, by cell counting and enzymatic activity quantification (paranitrophenylphosphate phosphatase (pNPP) test). A wound healing assay was used to study
cell migration after irradiation. Effects of PBM on cytoskeleton organization and cell shape were assessed by actin filaments
staining. Elasticity changes after irradiation were quantified in terms of Young’s modulus measured using Atomic Force
Microscopy (AFM) force spectroscopy. Green light significantly improved DPSC proliferation with a maximal effect obtained after 300-s irradiation (energy fluence 5 J/cm2). This irradiation had a significant impact on cell migration, improving wound
healing after 24 h. These results were concomitant with a decrease of cells’ Young’s modulus after irradiation. This cell softening
was explained by actin cytoskeleton reorganization, with diminution of cell circularity and more abundant pseudopodia. This
study highlights the interest of green laser PMB for the proliferation and migration of mesenchymal stem cells, with encouraging
results for clinical application, especially for surgical wound healing procedures.