MicroRNA-18b mediates the inhibitory effects of nicotine on periodontal ligament-derived stem cell

Objective: To investigate the level change of miR-18b in PDLSCs with nicotine exposure and its effect on PDLSCs' proliferation, migration and osteogenic differentiation. Methods: PDLSCs were isolated from periodontal ligament tissues which obtained from smoker patients and age-matched non-smoker. miR-18b levels in PDLSCs from different sources were detected using qRT-PCR. PDLSCs from non-smoker were treated with nicotine and the miR-18b level changes were confirmed at different time point after exposure. miR-18b was downregulated by miR-18b inhibitor transfection in PDLSCs and the influence of miR-18b knockdown on proliferation, apoptosis and migration of nicotine exposed PDLSCs were estimated using Cell Titer-Blue Assay, flow cytometry and time-lapse microscope, respectively. The changes of osteogenic differentiation markers including ALP, RUNX2, OCN and OPN were also analyzed using qRT-PCR and western blot. Furthermore, bioinformatics analysis was performed to predict the target genes of miR-18 followed with gene ontology analysis. Result: Higher miR-18b level was observed in PDLSCs from smoker and nicotine-treated PDLSCs. Restoring of miR-18b level in PDLSCs could relieve the inhibitory effect of nicotine on proliferation, migration and decrease apoptosis; however, it could not change the osteogenic differentiation markers. miR-18b may target the genes involved with protein localization and cellular localization. Conclusion: Nicotine has an inhibitory effect on proliferation, migration and osteogenic differentiation in PDLSCs; miR-18b may be a crucial regulator in these nicotine-associated functional changes.