Mast cell basic fibroblast growth factor in silicosis.

To investigate the role of mast cells (MC) and their fibrogenic growth factors in silicosis, we performed quantitative immunohistochemistry for MC tryptase and for basic fibroblast growth factor (bFGF) in lung tissue from silicotic and control subjects. Anti-bFGF antibody was bound to lung MC, basement membrane, endothelial cells, and smooth-muscle cells. Morphometric analysis revealed that the volume density (V(v)) of MC was increased in silicotic lung and that the V(v) of bFGF-positive (bFGF(+)) cells was significantly higher than normal in silicotic lung. Most MC contained bFGF (rho = 0.88, p < 0.001). The V(v) of collagen/reticulin fibers was increased in silicosis and correlated with the V(v) of bFGF(+) cells (rho = 0.81, p < 0.001). Immature silicotic nodules contained bFGF(+) MC throughout the loose array of collagen/reticulin fibers. In large, mature nodules, the density of collagen/reticulin fibers was higher, and bFGF(+) MC were found only in the nodule periphery. Because of this circumferential MC alignment in silicotic nodules, we observed a negative correlation between the V(v) of bFGF(+) MC and the density of collagen/reticulin fibers in silicotic nodules (rho = -0.80, p < 0.001) and between the V(v) of all other nodule-associated cells and the density of collagen/reticulin fibers in the hypocellular nodule centers (rho = -0.84, p < 0.001). We conclude that MC that produce bFGF may play an important role in the development of silicosis.