Objective To evaluate the effects of quaternized chitosan[N-(2-hydroxy-3-trimethylammonium) propylchitosan chloride] (HTCC) on the proliferation and cell cycle activities of human periodontal ligament cells(HPDLCs) with different concentrations compared with chitosan(CS). Investigating the mechanisms underlying the use of HTCC is necessary. Methods Primary cells were isolated from human periodontal ligament. HPDLCs were cultured and characterized by immunocytochemistry. The effect of varying concentrations(2 000, 1 000, 100, 50, 10, 3, 1.5, 1, 0.5, and 0.2 mg•L-1) of HTCC and CS on HPDLCs were evaluated by methyl thiazolyl tetrazolium(MTT) assay. Flow cytometry (FCM) was used to determine the cell cycle states of HPDLCs with HTCC(3 g•L-1, 1 g•L-1, and 3 mg•L-1) and CS(3 g•L-1 and 3 mg•L-1). The SPSS 13.0 software package was used for statistical analysis. Results Immunocytochemistry results show that the cells stained positively to antibodies against vimentin and stained negatively to antibodies against cytokeratin, indicating that the cells were external embryo mesenchymal cells. The MTT assay showed decreased optical density(OD) values of HTCC at concentrations of 2 000, 1 000, 100, and 50 mg•L-1 and increased OD values at concentrations of 10, 3, 1.5, 1, 0.5, and 0.2 mg•L-1. CS accelerated the proliferation of HPDLC at all tested concentrations. Compared with the control, a significant difference was observed at 5 d(P
