[Notch activation delayed ageing of human dental pulp cells]

To establish model of dental pulp cells with activated Notch signaling pathway, and investigate the effect of activating Notch signaling pathway on senescence of human dental pulp cells in vitro.

Human dental pulp cells were isolated, cultured as usual, and used from the 4(th) passage. The cells were divided into the activated group and the negative control group. In the activated group, the way of coating dishes with Jagged1 protein (10 mg/L) was used to activate Notch signaling pathway. The negative control group cells received no treatment. In the 4(th), 8(th), and 10(th) passages, the expression levels of the Notch signaling pathway downstream gene Hes1 were verified by real-time quantitative PCR (RT-qPCR). The cell changes after activating Notch signaling pathway were observed at three levels: (1) The cell morphology changes were observed through invert phase contrast microscope. The cell activity was detected with MTT assay. (2) The alkaline phosphatase (ALP) expression and its activity, and senescence-associated &bgr;-galatosidase (SA-β-Gal) expression were observed with the kit. (3) The expression changes of senescence related genes were verified using RT-qPCR. The difference between the negative control group and the activated group was analyzed using student's t test.

The expression level of the downstream gene Hes1 of Notch signaling pathway increased after coating the dishes with Jagged1 protein, indicating the establishment of the model of dental pulp cells with activated Notch signaling pathway. Compared with the negative control group, the aging cells of the activated group appeared relatively late. In the 8(th) and 10(th) passage, the cell activity increased. In the 10th passage, ALP activity increased, but SA-β-Gal expression decreased. p16 gene expression decreased in each passage, and p53 gene expression decreased in the 8(th) and 10(th) passages.

Jagged1 could activate Notch signaling pathway effectively. Through activating Notch signaling pathway, the dental pulp cells showed a trend of senescence delay at different levels, such as cell morphology, metabolic enzyme expressions and related gene expressions.