[Characterization of rat periodontal ligament cells in culture]

It has been reported that periodontal ligament cells (PDLC) show osteoblastic phenotypes in culture. In most previous studies, PDLC have been obtained from the tooth root surface, however, a new method in which PDLC are obtained from the coagulum after tooth extraction has been proposed recently. To compare PDLC from tooth surface with these from coagulum, PDLC from both sources were cultured and examined. PDLC from both sources responded to PTH or PGE2 increasing cAMP and showed high alkaline phosphatase (ALP) activity. Some PDLC cultures produced mineralized tissues and these mineralizing cultures showed high ALP activity with high gene expression level of type I collagen, bone sialoprotein, and osteopontin in comparison with non-mineralizing cultures. PDLC from both sources expressed various osteoblastic or cementoblastic phenotypes and seemed to contain heterogenous mesenchymal cell population with various differentiation potentials. However, the frequency of cellular transmigration, rate of mineralized tissue formation, increased level of cAMP that responded to PTH or PGE2, and osteopontin expression pattern were different between PDLC from both sources. These differences indicate that PDLC cultures from coagulum contain more immature cells than PDLC from tooth surface.