Promotion of Nd:YAP laser biostimulation on the proliferation and osteogenic differentiation of human periodontal ligament cells through WNT/β-catenin signaling pathway

Objective·To study the effect of neodymium-doped yttrium aluminum perovskite (Nd:YAP) laser biostimulation on the proliferation and osteogenic differentiation of human periodontal ligament cells (hPDLCs) and its possible mechanism.Methods·Five premolars removed for orthodontic reasons were collected from Changzhou Stomatological Hospital, and the periodontal ligament tissues from the middle 1/3 of the roots were taken to culture hPDLCs in vitro. The cells were irradiated with the biostimulation function [G (－) mode] of the Nd:YAP laser. According to the irradiation time, the cells were divided into a control group (without laser irradiation), and groups irradiated for 5 s, 10 s, 15 s, 20 s and 30 s. The cell counting kit-8 (CCK-8) method was used to detect the proliferation of hPDLCs in each group. After osteogenic differentiation was induced, the alkaline phosphatase (ALP) content and activity level of the cells were detected using an ALP staining kit and an ALP activity detection kit. The calcium salt level of the cells was evaluated by alizarin red S staining and calcium quantitative analysis. The expression of genes and proteins related to the WNT/β-catenin signaling pathway, including dickkopf-related protein 1 (DKK-1), β-catenin, and runt-related transcription factor 2 (RUNX2), was analyzed by quantitative real-time PCR (qPCR) and Western blotting.Results·The results of CCK-8 showed that the proliferation level of cells in the 10 s, 15 s, 20 s, and 30 s groups was enhanced from 3 d after irradiation (all P<0.05). After induction of osteogenic differentiation, ALP content, activity, and calcium salt level in the laser irradiation groups increased with the extension of irradiation time (all P<0.05). The results of qPCR and Western blotting analysis showed that the expression levels of the DKK-1 gene and protein in the laser irradiation groups decreased with the extension of irradiation time. However, the expression levels of β-catenin and RUNX2 genes and proteins increased significantly with the extension of irradiation time; there were statistically significant differences between the 15 s, 20 s, and 30 s groups and the control group (all P<0.05).Conclusion·Nd:YAP laser biostimulation may promote proliferation and osteogenic differentiation of hPDLCs through WNT/β-catenin signaling pathway.