The study looked at how mouse fetal lung cells grow in a lab dish. It found that a small peptide (GHK) plus some hormones can make the cells form branching structures, but the type of hormone determines whether certain lung cells develop. The way the cells are cultured (submerged vs. exposed to air) also changes the shape they take.

Differentiation of the respiratory region of fetal mouse lungs was investigated in serum-free medium supplemented with growth factors and hormones. Terminal buds from the margins of a lobe were removed from 16-day fetuses and organ cultures prepared either in submersion culture or at the air-medium interface. It was found that glycyl-L-histidyl-L-lysine, transferrin, and somatostatin were sufficient to promote branching in the absence of serum. However, type II pneumocytes containing lamellar bodies formed only in the presence of thyroxine or dexamethasone. At concentrations of these hormones slightly above the physiological range most of the cells became cuboidal and contained lamellar bodies; at lower concentrations regions of flattened cells appeared. In submersion culture a large, central cavity surrounded by saccules was formed rather than a branched tree. Thus, the pattern of differentiation is significantly influenced by culture conditions.