<ORIGINAL>Effects of extracellular calcium on normal human bone cells

P(論文)It has been demonstrated that elevated extracellular calcium can inhibit the formation of osteoclast-like cells and stimulate osteoblastic proliferation, indicating that extracellular calcium is very important for the process of bone remodeling. The current study was carried out to examine the effect of increased extracellular calcium on the cell It has been demonstrated that elevated extracellular calcium can inhibit the formation of osteoclast-like cells and stimulate osteoblastic proliferation, indicating that extracellular calcium is very important for the process of bone remodeling. The current study was carried out to examine the effect of increased extracellular calcium on the cell proliferation, differentiation, chemotactic activity, prostaglandin E_2 (PGE_2) synthesis and mRNA levels of bone morphogenetic proteins (BMP), well-documented osteoinductive proteins, in normal human mandible-derived bone cells (HOB-M cells) in vitro. The results are as follows. 1. An increase in extracellular calcium significantly increased cell proliferation with an optimal dose at 0.4mM (added CaCl_2), as assessed by XTT proliferation assay. 2. While elevated extracellular calcium failed to increase alkaline phosphatase (ALP) activity or osteocalcin secretion, it significantly increased procollagen type I carboxy-terminal peptide (PICP) production, a useful measure of type I collagen synthesis. 3. Increased extracellular calcium did not significantly affect the chemotactic activity of HOB-M cells. 4. Treatment with increased calcium (0.4-1.2mM ; added CaCl_2) for 24 hrs significantly increased the PGE_2 synthesis into the media. 5. However, addition of indomethacin (10^M), an inhibitor of PGE_2 synthesis, did not block the increased cell proliferation by calcium. 6. Mild increases (0.1-0.4mM ; added CaCl_2) in extracellular calcium markedly increased the mRNA levels of BMP-2, -4 and -5, after 0.5- and 24-hour incubations as evaluated by reverse transcription-polymerase chain reaction (RT-PCR). 7. However, a severe increase (1.2mM ; added CaCl_2) in extracellular calcium failed to affect the mRNA levels of BMP, except for an increase in mRNA level of BMP-5 at 24 hr. These results indicate that extracellular calcium is one of the potent regulatory factors of BMP, type I collagen as well as PGE_2 in human osteoblastic cells.departmental bulletin pape