TWIST1 modulates the odontoblast-like differentiation of human DPSCs. (A) Human DPSCs were stably transduced with lentiviruses expressing TWIST1 (LV-TWIST1) or empty lentiviral vectors expressing only enhanced green fluorescent protein (LV-EGFP). Western blot analysis showed the overexpression of Twist1 in DPSCs transduced with LV-TWIST1 compared with LV-EGFP. (B) Human DPSCs were transduced with lentiviruses expressing 2 short hairpin RNA targeting human TWIST1 mRNA (LV-ShT1 or LV-ShT2, respectively) or empty lentiviral vectors expressing only Turbo green fluorescent protein (LV-TGFP). Western blot analysis showed that LV-ShT1 and LV-ShT2 knocked down TWIST1 expression by 50% and 90%, respectively. (C) Western blot analysis of total proteins extracted from DPSCs stably transduced with TWIST1 overexpressing (LV-TWIST1, left panel) or silencing (LV-ShT2, right panel) lentiviral vectors or their control vectors. DPSCs stably transduced with the indicated lentiviral vectors were allowed to grow for 2 wks in the differentiation medium. Total proteins were extracted and analyzed with antibodies for ALP, OCN, DMP1, OPN, and DSP, with β-actin as a loading control. TWIST1 overexpression enhanced the expression of OCN, DMP1, and OPN as well as DSP, but had no apparent effect on ALP expression. Consistently, TWIST1 silencing dramatically enhanced the expression of ALP, but inhibited DMP1, OPN, and DSP, and had no effect on OCN expression.