Abstract: Objective To investigate the effect of endothelin-1 on osteogenic differentiation in human periodontal ligament stem cells (PDLSCs). Methods PDLSCs were isolated from the periodontal ligament tissues of patients and then were treated with ET-1 (10^-9, 10^-8or 10^-7mol/L) for 7 d, 14 d, or 21 d.mRNA and protein expressions of Runx2, OCN, and COL1 were detected by real time PCR and western blot, respectively, and the role of ET-1 in osteogenic differentiation of PDLSCs was identified. Results The mRNA and protein expression of Runx2, OCN, and COL1gradually increased with the exposure of ET-1, peaking at day 21 (P＜ 0.05).At each time point (7 d, 14 d, and 21 d), the mRNA and protein expressions of Runx2, OCN, and COL1 were induced at a dose-dependent manner (10^-9, 10^-8or 10^-7mol/L). Conclusion ET-1 may promote osteogenic differentiation of PDLSCs by increasing expression of Runx2, OCN, and COL1.