Dynamic phase of Alveolar Bone-derived Osteoblasts at High Calcium Ion Concentration with Bone Resorption Accentuation.

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Human alveolar bone-derived osteoblast-like cells were obtained from alveolar bone fragments of young (18-24 years old) and old (55-68 years old) patients. The cells that migrated from individual bone fragment were harvested separately and subcultured up to the third passage. After seeding the cells in 6-well microplates, the cells were cultured with α-MEM containing 10% FBS and 1.8 to 10 mM CaCl_2 for up to 72 h. The gene expression of extracellular matrix proteins, MMPs, TIMPs, osteoclast differentiation factor (ODF) and osteoclastogenesis inhibitory factor was examined at mRNA level by quantitative RT-PCR using specific primers. The following results were obtained.1. Although logarithmic cell proliferation was recognized in low Ca^<2+> concentration (1.8 and 2.5 mM), it was not recognized in high Ca^<2+> concentration (5 and 10 mM).2. Gene expression of bone sialoprotein and osteocalcin was increased by addition of high Ca^<2+> concentration in both age groups. Expression of type I collagen and osteonectin was not affected by addition of Ca^<2+> in both age groups.3. Expression of MMP-1 and MMP-2 was not affected by addition of Ca^<2+> in both age groups. MMP-3 expression was not detected with or without Ca^<2+> in both age groups.4. Expression of TIMP-1 and TIMP-2 was increased in Ca^<2+> concentration-dependent in both age groups, and the effects were recognized markedly in young age group.5. Expression of OCIF was increased by addition of high Ca^<2+> concentration in both age groups, and the effects were recognized markedly in young age group. In contrast, ODF expression was not detected with or without Ca^<2+> in both age groups.