2008 Volume 51 Issue 1 Pages 99-104
We have previously reported that densely calcified nodules formed from dental pulp cells are often observed in tissue culture, and that TNF-α receptor, Fas, and Fas-ligand in relation to apoptosis were detected in and around the nodules using an in situ apoptosis detection kit. However, the relationship between the nodule formation in the pulp cells and their occurrence of apoptosis has not yet been clarified. So, we tried to confirm this relationship in vitro. The dental pulp cells outgrown 5 to 9 times in the D-MEM (Dulbecco's modified Eagle Medium) harvested from a patient with periodontitis were cultured for 8 weeks and used in this study. The cells in the control group were cultured in the D-MEM culture alone, while those in the experimental group were cultured in another D-MEM containing the Caspase-3 inhibitor activated at the final stage of apoptosis. The process of nodule formation was examined and recorded using a phase contrast microscope from the start of the experiment. The Caspase-3 activity was labeled by FITC at 4 weeks and the cells containing the Caspase-3 were observed by a laser microscope. Statistical analysis of the change in number of nodules was done by a paired or unpaired t-test. As a result, the nodules were formed with time in the presence or absence of the Caspase-3 inhibitor, and were significantly increased in number. However, the number of nodules cultured in the presence of the Caspase-3 inhibitor was significantly less than that in the control group in and after three weeks. Caspase-3 activity was detected in both groups in the nodules of the 4-week culture. We had previously thought that apoptosis in cultured dental pulp cells occurred in the process of calcification. However, our findings suggest that apoptosis occurs during nodule formation.
