Pathological mineralization in a serially passaged cell line from rat pulp.

The ultrastructure of crystal formation in association with dental pulp cells isolated from rat incisor was studied in vitro. A clone, RPC-K, was obtained and incubated with Na-beta-glycerophosphate (BGP). Growing pulp cells showed low alkaline phosphatase (ALP) activity, which began to increase with cell proliferation. Pulp cells formed cell multilayers after day 14 of culture. Mineralized tissues were observed within cell multilayers on day 28 of culture. Vesicular structures were found around degenerate and necrotic cells. Some of these vesicles contained needle-like crystals. Organic structures appeared at the periphery of mineralized tissues with a post-embedding demineralization and staining method. Electron diffraction patterns of the newly formed crystals revealed a pattern consistent with hydroxyapatite (HAP). These findings suggest that the RPC-K cell line might be useful for a model system to investigate pathological mineralization.