Abstract
We have previously reported that dental pulp cells can form calcified nodules, and that apoptosis was detected around the nodules by using an in situ apoptosis detection kit. However, the relationship between nodule formation of the pulp cells and apoptosis has not yet been clarified. The purpose of this study was to confirm the role of apoptosis in the nodule formation of dental pulp cells in vitro. Dental pulp cells in explant culture originating from a patient with periodontitis were cultured from 5 to 9 limes in D-MEM. The cells were cultured for 4 weeks in the absence or presence of a Caspase-3 inhibitor, Caspase-3 /CPP32 Inhibitor-CHO, in order to examine its effect no inhibition of apoptosis of dental pulp cells. The formation of nodules by dental pulp cells was observed by phase contrast microscope in the fourth week of culture, and the total numbers of nodules in a definite field were counted. Apoptosis of dental pulp cells in nodules was detected with a Caspase-3 detection kit by FITC, and was observed by laser microscope. Statistical analysis on changes of the nodule numbers was done by paired or unpaired t-test. Results showed that the number of nodules formed in the absence or presence of the caspase-3 inhibitor increased every week during four weeks (P<0.01). However, the number of nodules in the presence of the caspase-3 inhibitor was significantly less than that of the control culture at three and four weeks (P<0.05). These results indicate that apoptosis of dental pulp cells in vitro occurres along nodule formation and precedes calcification.
