Abstract
We have recently shown that connexin 43 (Cx43), a major gap junction protein in osteoblasts, is expressed with an increase in cell density (CHIBA, H. et al.(1993). Cell Struc. Fund., 18 : 419-426). In the present study, we examined what kinds of hormones and cytokines regulate the gap junction protein in osteoblastic cells, using a human osteoblastic cell line (SV-HFO) after reaching a con fluent density to avoid influence of cell proliferation. Either retinoic acid (RA) or transforming growth factor-β1 (TGF-β1) induced the Cx43 expression of SV-HFO cells, as revealed by Northern blot analysis and immunocytochemistry. These modulators also increased gap junctional intercellular communication, in terms of the extent of dye transfer. On the other hand, 1α, 25-dihydroxyvitamin D3 did not influence the Cx43 expression and gap junctional intercellular communication of the cells. These results suggest that RA and TGF-β1 might maintain bone tissue as an organized tissue in vivo by increasing intercellular communication of osteoblastic cells.
