|Budget Amount *help
¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1999 : ¥1,200,000 (Direct Cost : ¥1,200,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
1) Establishment of a culture system for dental pulp cells
We developed a culture system for differentiation of dental pulp cells into odontoblast-like cells. Pulp cells were prepared from pulps of rat incisors by protease treatment. The cells were cultured in a medium containing ascorbic acid, dexamethasone and 2-glycerophosphate. The cells formed cellular nodules and then formed calcified deposits in the nodules. The cells had a high alkaline phosphatase activity. Expression of phosphophoryn/DSP, a protein specific to odontoblasts, was detected by using RT-PCR. Expression of BGP, a protein specific to calcified tissues, was also detected. These phenotypes indicates that the cell were differentiated into odontoblast-like cells.
2) Effects of bioactive factors on the expression of phosphophoryn/DSP
By using the above culture system, we examined effects of several reagents on the expression of odontoblast-specific genes. Dexamethasone, a differentiation factor for osteoblasts, enhanced the expression of the phosphophoryn/DSP. This agent promoted the differentiation of the pulp cells. Another osteotropic hormone, 1,25(OH)ィイD22ィエD2DィイD23ィエD2 had no effect on the expression. Bis-phosphonate, an agent inhibitory to calcification, activated the expression of the phosphophoryn/DSP, although it reduced the calcification. This result indicates that the bis-phosphonate promoted the differentiation of the pulp cells. Inhibition of the calcification can be caused by its physico-chemical activity.