Supernatants from quartz dust treated human macrophages stimulate cell proliferation of different human lung cells as well as collagen-synthesis of human diploid lung fibroblasts in vitro.

Silicosis is a chronic lung disease, which is caused by inhalation of silica-containing dusts, leading to pulmonary fibrosis. Alveolar macrophages play a key-role in defence against these particles entering the lung. As a result of phagocytosis, the macrophages release mediators, which are involved in various processes of inflammation and immunological defence mechanisms. We established an in-vitro test system composed of human macrophages, human pneumocyte type II cells (line A-549), human diploid lung fibroblasts (line Wi38) and human tracheobronchial epithelial cells (line BEAS-2B). With this model, we were able to study the influence of various cytokines, produced by the macrophages, on cell proliferation and collagen synthesis (only fibroblasts) of the cells in our test-system. In this report, we will summarize data obtained from our in-vitro test system on two cytokines, which are thought to be important in pathogenesis of lung fibrosis: insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta (TGF-beta).