The specific production of the third component of complement by osteoblastic cells treated with 1α,25-dihydroxyvitamin D 3

Abstract

A 190 kDa protein was purified from conditioned media of mouse marrow-derived stromal cell (ST2) cultures treated with 1α 25-dihydroxyvitamin D 3 (1α,25(OH) 2D 3) and identified as the third component of mouse complement (C3). Northern and Western blot analysis revealed that the production of C3 by ST2 and primary osteoblastic cells was strictly dependent on 1α,25(OH) 2D 3, but the production by hepatocytes was not. Adding 1α,25(OH) 2D 3 together with mouse C3 antibody to bone marrow cultures greatly inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive osteoclast-like multinucleated cells. Adding C3 alone induced no TRAP-positive cell formation. These results suggest that, in bone tissues, C3 is specifically produced by osteoblasts in response to 1α,25(OH) 2D 3 and somehow involved in inducing differentiation of bone marrow cells into osteoclasts in concert with other factors produced by osteoblasts in response to 1α,25(OH) 2D 3.