Cytodynamics of in vitro developing airways and interaction with extracellular matrix proteins.

We studied epithelial and mesenchymal cell kinetics during lung branching and the possible importance of proteoglycan and collagen in rat fetal organ culture for 5 days, starting from 15 days gestation. The lungs were randomly divided into three groups: (1) basal medium (controls); (2) basal medium + beta-D-xyloside (beta-XYL); and (3) basal medium+cis-4-hydroxy-L-proline (cis-HYP). The labeling index of incorporation of 5-bromo-2-deoxyuridine (BrdU) was used as an indicator of DNA synthesis and assessed in the parent airways and in the tips and sides of peripheral buds. In controls, BrdU incorporation was highest in bud tips, followed by bud sides and then parent airway for both epithelium and mesenchyme. These data suggest that preferential cell proliferation occurs in normal airway branching. In parent airways, labeling of epithelium and mesenchyme was consistently diminished throughout the culture period in beta-XYL, whereas in cis-HYP this was not the case. In the peripheral buds, the DNA synthetic activity in both epithelium and mesenchyme was impaired in beta-XYL and cis-HYP, but the effect was more marked in beta-XYL. We conclude that although collagen may be required in peripheral bud morphogenesis, the proteoglycans appear to be essential in growth and development of both parent airways and peripheral buds in the lung.