Liberation of a fibrogenic factor from human blood monocytes, ascites cells, cultured histiocytes and transformed mouse macrophages by treatment with SiO2.

Human monocytes and ascites macrophages from cirrhotic patients were isolated in Percoll-gradient and cultured with and without silica. Similar experiments were carried out also with cultured malignant human histiocytes and transformed mouse macrophages. The fibrogenic activity of the culture media was tested by measuring the incorporation of [3H]proline and [3H]thymidine into cultured rat granuloma and human synovial cells. Media from silica-treated monocytes, ascites macrophages and certain histiocyte and mouse macrophage lines caused an increase in the incorporation of both [3H]proline and [3H]thymidine into collagen and DNA, respectively, in both cell systems. Alkaline RNase activities were decreased markedly in the media from silica-treated ascites macrophages but not in the media of the monocytes or histiocytes.