| Co-Investigator(Kenkyū-buntansha) |
SHINKI Toshimasa Showa University School of Dentistry, Lecturer, 歯学部, 講師 (90138420)
TAKAHASHI Naoyuki Showa University School of Dentistry, Associate Professor, 歯学部, 助教授 (90119222)
SUDA Tatsuo Showa University School of Dentistry, Professor, 歯学部, 教授 (90014034)
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| Research Abstract |
We previously reported that 1alpha, 25-dihydroxyvitamin D_3 [1alpha, 25(OH)_2D_3] specifically stimulates production of the third component of complement (C3) by murine osteoblastic cells and marrow-derived stromal cells (ST2) in vitro. We also exmamined tissue-specific production of C3 in vivo in vitamin D-deficient mice, some of which received supplemental 1alpha, 25(OH)_2D_3. Western blot analysis indicated that the C3 protein band in bone was undetectable in vitamin D-deficient mice, but became distinct 48h after 1alpha, 25(OH)_2D_3 administration. The mRNA expression of C3 in bone was also undetectable in vitamin D-deficient mice and appeared as early as 24h after 1alpha, 25(OH)_2D_3 administration. The serum concentration of C3 in vitamin D-deficient mice was almost identical to that in normal mice and was unchanged after 1alpha, 25(OH)_2D_3 administration. These results demonstrate that 1alpha, 25(OH)_2D_3 tissue-specifically regulates in vivo production of C3 in bone.
To examine the possible roles of C3 in bone, bone marrow cells were cultured with antibodies against C3 and C3 receptors (Mac-1, C12, and 7G6) and the purified mouse C3 protein. Adding anti-C3 antibody together with 1alpha, 25(OH)_2D_3 to bone marrow cultures greatly inhibited not only the appearance of osteoclast-like mono and multi nucleated cells, but also the growth of macrophage-like mononuclear cells and stromal cells. 1alpha, 25(OH)_2D_3 inhibited the M-CSF-dependent growth of bone marrow macrophages, but the inhibition was prevented by adding C3 protein. These results suggest that the C3 protein produced by stromal cells in response to 1alpha, 25(OH)_2D_3 is somehow involved in osteoclast development by potentiating M-CSF-dependent proliferation of bone marrow cells and induction of osteoclast differentiation.
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