Figure 4.

KGF overexpression in the lung protects the lung alveolar epithelium from hyperoxia-induced cell death. KGF transgene-positive mice were maintained without Dox (KGF⁻) or were supplied with Dox (KGF⁺) in drinking water 24 h before exposure to room air or 100% O₂ for up to 72 h. Lungs were fixed in glutaraldehyde and ultrathin sections were obtained and analyzed by electron microscopy. (Top) Normal lung architecture in KGF transgene-positive animals without Dox (KGF⁻) exposed to room air for 72 h. Similar observations were made with KGF transgene-negative animals (data not shown). (Middle) KGF⁻ O₂: Hyperoxic exposure in the absence of induction of KGF shows alveolar disintegration. Capillaries also show aberrant morphology with endothelium peeling away from the basement membranes (arrows). Blood cells (*) in the alveolar space indicate hemorrhage. (Bottom) KGF⁺ O₂: Hyperoxic exposure in the presence of KGF preserved the ultrastructure of the cells lining the alveolar space. However, the endothelium and accessory cells lining the capillaries have undergone apoptosis (arrowheads; nuclear condensation is evident). Five animals were included per group and multiple areas, i.e., samples from various parts of each lung, were evaluated. (Bar = 2 μm, representative of all images.) TII, type II cell; Cap, capillary.