OBJECTIVETo investigate the effect of Notch signaling pathway on human dental pulp cells.

METHODSThe γ-secretase inhibitor N-[N-(3, 5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester(DAPT) was applied to inhibit the Notch signaling pathway of human dental pulp cells. The solvent dimethly sulfoxide (DMSO) served as the negative control.Senescence conditions were evaluated by cells morphology changes, the alkaline phosphatase (ALP) expression and its activity, senescence-associated β-galactosidase (SA-β-Gal) expression and the senescence related gene p53 expression.

RESULTSAfter inhibition of the Notch signaling pathway, morphology changes, including flatter cells, larger plasma area, were seen in the 10th passage human dental pulp cells. ALP expression and activity showed a significant decrease at the 8th passage after inhibition (35.36 ± 2.55) U/g, compared with the negative control group[(49.76 ± 4.30) U/g] (t = 4.989, P = 0.008).SA-β-Gal-positive cells could be seen as early as the 8th passage and more positive cells were evident at the 10th passage. The relative expression level of p53 gene was elevated in the 10th passage cells (1.7 ± 0.4) compared with the negative control group(1.0) (t = 3.581, P = 0.012).

CONCLUSIONSHuman dental pulp cells became senescent at earlier passages after inhibition of Notch signaling pathway.Notch signaling pathway may affect life cycle of human dental pulp cells.