Figure 4.

(a) Immunoblot shows stretch-induced upregulation of SM-specific protein synthesis in human lung mesenchymal cells undergoing myogenic differentiation. (b) Immunoblots show stimulation of SM protein synthesis in human fetal lung organ cultures by dextran-induced tissue stretching. In a and b the lungs were obtained from 18-week fetuses, after the onset of visceral and vascular SM differentiation. Therefore, the initial levels of SM protein are higher than in murine cells. (c and d) Immunohistochemistry shows SM α-actin in histological sections from human fetal lungs (18 weeks) cultured for 48 hours with 1% dextran in the culture medium outside the explant (c) and 1% dextran inside the airways (d). Notice the significant increment in bronchial SM cells in c compared with d (arrows). The vascular SM shows no differences (arrowheads). Results are representative of three experiments, each performed on quadruplicate lung explants per treatment. Bar, 20 μm.