N-acetylcysteine promotes cyclic mechanical stress-induced osteogenic differentiation of periodontal ligament stem cells by down-regulating Nrf2 expression.

Background/purpose: Mechanical stress plays a vital role in osteogenic differentiation of periodontal ligament stem cells (PDLSCs). Cyclic mechanical stress may up-regulate reactive oxygen species (ROS) level. N-acetylcysteine (NAC) possesses powerful antioxidant capacity. However, it is undefined the impact of NAC on osteogenic differentiation stimulated by cyclic mechanical stress in PDLSCs. The aim of our research was to study the effect of NAC on PDLSCs during osteogenic differentiation under cyclic mechanical stress. Materials and methods: The expression levels of osteogenesis markers were used to examine the osteogenic differentiation of PDLSCs. ROS production were measured by flow cytometry. The levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) were analyzed. We also examined the changes of alveolar bone and periodontal ligament (PDL) tissues in orthodontic rats by micro-computed tomography (micro-CT) system and immunohistochemistry (IHC) staining. The nuclear factor erythroid-2-related factor-2 (Nrf2) expression was examined. Results: NAC could enhance the osteogenic differentiation and up-regulate the GSH level as well as the ratio of GSH/GSSG, while down-regulate ROS generation and Nrf2 expression induced by cyclic mechanical stress in PDLSCs. NAC had beneficial effects on the microstructure of alveolar bone and enhanced the expression levels of osteogenesis markers, such as alkaline phosphatase (ALP) and collagen type 1 (COL1) in PDL in orthodontic rats at the tension side. Conclusion: NAC could improve the osteogenic differentiation stimulated by cyclic mechanical stress in PDLSCs and in orthodontic rats, suggesting a potential therapeutic approach for alveolar bone remodeling in orthodontics.