N-acetylcysteine promotes osteogenic differentiation in periodontal ligament stem cells under cyclic mechanical stretch

Abstract Background Biomechanical forces are vital for the regulation of skeletal tissue. Mechanical stretch plays a vital role in osteogenic differentiation of periodontal ligament stem cells (PDLSCs) during orthodontic treatment. Cyclic mechanical stretch may trigger the up-regulated production of reactive oxygen species (ROS). ROS has a critical effect on bone cell function and the pathophysiology of bone diseases. N-acetylcysteine (NAC), a ROS scavenger, possesses powerful antioxidant capacity. The aim of this study was to determine the role of ROS and NAC in PDLSCs during osteogenic differentiation under cyclic mechanical stretch. We further investigated that the therapeutic potential of NAC to improve the changes of the microstructure of alveolar bone during orthodontic tooth movement in rats by micro-CT system. Methods The expression of COL1 (collagen type I), RUNX2 (runt-related transcription factor 2) and OPN (osteopontin) by qRT-PCR and Western blot experiments, and alkaline phosphatase (ALP) staining as well as ALP activity tests were used to examine osteogenic differentiation tendency of PDLSCs subjected to cyclic mechanical stretch of 10% and 0.5Hz deformation induced by the Flexcell tension system. ROS production in PDLSCs were measured under cyclic mechanical stretch by Flow Cytometry. The levels of reduced glutathione (GSH), oxidized GSH (GSSG) and the GSH/GSSG ratio with or without NAC treatment were analyzed. And we evaluated the changes of the microstructure of alveolar bone during orthodontic tooth movement in rats employing micro-CT system. Results NAC treatment could promote the osteogenic differentiation of PDLSCs under cyclic mechanical stretch. Down-regulated ROS generation and the up-regulated level of GSH and the ratio of GSH/GSSG in PDLSCs treated with NAC were observed in response to cyclic mechanical stretch. NAC improved the microstructure of alveolar bone, including BV/TV (bone volume/total volume), Tb.Th (trabecular thickness), Tb.Sp (trabecular separation) and SMI (microstructure model index), during orthodontic tooth movement in rats. Conclusion These results revealed that NAC might be a potential therapeutic approach for the remodeling of the alveolar bone during orthodontic tooth movement.