DEVELOPMENT AND CHARACTERIZATION OF A HUMAN MARROW STROMAL CELL-LINE THAT ENHANCES OSTEOCLAST-LIKE CELL-FORMATION

We established a human bone marrow stromal cell line (Saka) by infecti ng marrow adherent cells from semisolid marrow cultures with a recombi nant simian virus-40 (SV40) virus. The cells expressed SV40 large tumo r antigen, had a fibroblast-like shape, and expressed fibronectin and vimentin. They did not contain detectable alkaline phosphatase activit y; express myeloid, lymphoid, or factor VIII-associated antigens; or d evelop adipocyte-like characteristics with dexamethasone treatment. Po lymerase chain reaction analysis of Saka cell RNA detected expression of messenger RNAs for interleukin-6 (IL-6), IL-1 beta, granulocyte-mac rophage colony-stimulating factor, macrophage colony-stimulating facto r, stem cell factor, and the 1,25-dihydroxyvitamin D-3 receptor. Cocul ture of Saka cells with human marrow mononuclear cells enhanced format ion of osteoclast-like multinucleated cells (MNC) in long term human b one marrow cultures. These MNC expressed calcitonin receptors and form ed resorption lacunae on dentine. In contrast, coculture of marrow mon onuclear cells with other SV40-transformed human marrow stromal cell l ines did not increase MNC formation. Conditioned medium from Saka cell s or coculture of bone marrow and Saka cells separated by a Millipore membrane did not enhance MNC formation. Addition of a neutralizing ant ibody to IL-6 or IL-1 beta blocked the effects of Saka cells on MNC fo rmation. These results suggest that marrow stromal cells enhance osteo clast formation in part through direct cell to cell contact and produc tion of IL-6 and/or IL-1 beta.