Red LED Enhances Proliferation and Osteogenic Differentiation of Human PDLSCs

Objectives: Light-emitting diode (LED) is a new light source for photptherapy. However, it has not been clarified that the effect of LED on periodontal tissue regeneration. The aim of this study was to investigate the effect of high-power, red LED irradiation on cell proliferation, and the osteogenic differentiation and mineralization of human periodontal ligament stem cells (PDLSCs).

Methods: Human PDLSCs were derived from female third molars. The light source was red LED (peak wavelength of 650 nm and power density of 1100 mW/cm²). Energy densities ranging from 0 to 10 J/cm2 were tested to determine the optimal dose. PDLSC proliferation was evaluated using two parameters: live cell protease and ATP levels. After the cells were induced to differentiate, Next, the effect of LED irradiation on osteogenic differentiation and mineralization was observed, with a 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 enhancing in PDLSC proliferation and enhanced Runx2 and Osterix mRNA expression, ALP activity, procollagen type 1 C-peptide and osteocalcin production, calcium deposition and Alizarin Red S staining. Furthermore, 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 present study clearly demonstrates that 650-nm high-power, red, LED irradiation increases PDLSCs proliferation, and osteogenic differentiation and mineralization, mediated by ERK1/2 activation. These findings show that LED may be a useful tool for periodontal tissue regeneration.