CHARACTERIZATION OF A SYSTEM OF MINERALIZED-TISSUE FORMATION BY RAT DENTAL-PULP CELLS IN CULTURE

Pulp tissue was obtained from maxillary incisors of young adult male W istar rats, minced and digested with 0.5% trypsin and 0.02% EGTA at 37 -degrees-C for 30 min. Dissociated cells were cultured with or without 10 nM dexamethasone using Eagle's minimal essential medium supplement ed with 10% fetal bovine serum and 50 mug/ml ascorbic acid. Confluent cells were subcultured at 7 days and the medium further supplemented w ith beta-glycerophosphate (beta-GP). Dexamethasone in primary culture and/or secondary culture enhanced the formation of mineralized tissue while > 5mM beta-GP was necessary for mineralization to occur. Biochem ical analysis of the radiolabelled medium revealed that these cells pr oduced type I, type I trimer and type III collagens. Analysis of [(PO4 )-P-32]-labelled medium, using DEAE-Sephacel ion-exchange chromatograp hy and sodium dodecylsulphate-polyacrylamide gel electrophoresis, show ed that these cells produced phosphophoryn-like protein. These results indicate that some of the rat dental pulp cells in culture express an odontoblast-like phenotype.