Species difference exists in the effects of 1α,25(OH)2D3 and its analogue 2-methylene-19-nor-(20S)-1,25-dihydroxyvitamin D3 (2MD) on osteoblastic cells

The direct effect of 1α,25(OH)2D3 on osteoblasts remains unclear. In this study, we evaluated the in vitro effects of 1α,25(OH)2D3 and its analogue, 2-methylene-19-nor-(20S)-1,25-dihydroxyvitamin D3 (2MD), on osteoblasts from three different species, i.e. bone marrow stromal cells from the Sprague–Dawley (SD) rat, from the C57BL/6 mouse, as well as human osteoblast NHOst cells and human osteosarcoma derived MG-63 cells. We found that in rat cells, both compounds increased cell proliferation, inhibited cell apoptosis and increased alkaline phosphatase (ALP) activity. In mouse cells, however, both compounds initiated cell apoptosis and inhibited ALP activity. In human cells, although cell proliferation was inhibited by both compounds, cell apoptosis was inhibited and ALP activity was enhanced. In each species, 2MD was much more potent than 1α,25(OH)2D3. To summarize, species differences should be taken into account in studies of vitamin D effects. However, in all tested species – rat, mouse and human – 2MD is considerably more potent in its effects on osteoblastic cells in vitro than 1α,25(OH)2D3.