Activation and dynamic expression of Notch signalling in dental pulp cells after injury invitro and invivo

AimTo investigate the expression pattern of Notch signalling in odontoblast-like cells stimulated by lipopolysaccharide (LPS) invitro, and in injured rat dental pulp invivo. MethodologyMouse odontoblast-like cells (MDPC-23) were exposed to LPS. Expression of Notch-related genes was detected by real-time PCR. A rat pulpitis model was established by mechanical injury and LPS plus mechanical injury was followed by the analysis of expression of Notch2 by immunohistochemical staining. One-way analysis of variance (anova) was performed to examine the effect of differing concentrations of LPS on cell proliferation, and least significant difference test was used for paired comparisons. For independent sample, t-test was performed to compare the expression of Notch signalling genes between LPS group and control group invitro. ResultsThe invitro study revealed the proliferation of MDPC-23 cells on exposure to 10ngmL(-1) to 1gmL(-1) LPS. Expression of Notch1 and Notch2 was significantly higher in the LPS group than that in the control group on day 1 and day 3 (P?0.05). The levels of both Delta1 and Jagged1 were higher in the study group than in the control group on day 3 (P=0.019 and P=0.034) and day 5 (P?0.001 and P=0.046), respectively. In addition, Hes1 levels were significantly higher in the study group than in the control group on day 5 (P=0.005). The invivo study demonstrated positive staining for Notch2, both in the mechanical injury (MI) group and in the LPS plus mechanical injury (LMI) group from day 3 to day 7, which showed very weak or absent staining on day 14, thereby demonstrating the dynamic nature of the change. ConclusionsBoth invitro and invivo activation and dynamic expression of Notch signalling in dental pulp cells after injury were found. Notch signalling activation by LPS stimulation or mechanical injury showed a similar pattern invivo.