Fig. 1.

Characterization of pig type II alveolar epithelial cells (T2AECs). A: time course of transmembrane electrical conductance (mS, millisiemens) of T2AECs growing on collagen I-coated Transwell membranes (n = 4 at each time point). B: immunostaining of tight junction marker zonula occludens-1 (ZO-1; red) in pig T2AECs 4 days after seeding. Nuclei were counterstained with DAPI (blue). Scale bar = 200 μm. C and D: Lysotrack green DND-26 (150 nmol/l, 30 min) was used to selectively stain lamellar bodies in primary cultures of airway (C) and alveolar (D) epithelial cells. Cells were grown on collagen I-coated Transwell membranes and imaged 4 days after seeding. Lamellar bodies were found in T2AECs (D) but not in tracheal alveolar epithelial cells (C). Nuclei were stained with Hoechst dye (blue). Scale bar = 200 μm. E and F: ultrastructure of pig T2AECs. T2AECs cultured at the air-liquid interface (ALI) for 4 days were fixed and processed for transmission electron microscopy. E: the majority of cells are cuboidal in shape with microvilli on the apical surface (denoted by arrow), consistent with a T2AEC identity. F: at higher magnification, lamellar bodies with a multilayered onionlike ultrastructure were observed (arrow). Scale bars = 2 μm for E and 0.2 μm for F.