Primary cell culture of green fluorescent protein-positive (GFP+) rat lung epithelial cells. Shown is immunostaining of freshly isolated GFP-modified rat pulmonary epithelium, enriched for alveolar cell types, at day 7 in both experimental conditions. (A–D) and (E–H) Immunostaining of keratin [red; rhodamine (Alexa Fluor 568)] in rolled and static cultures, respectively. Nuclei are stained with DAPI (blue). (I–L) and (M–P) Surfactant protein C (SP-C) (blue; Alexa Fluor 405) and ZO-1 [red; rhodamine (Alexa Fluor 568)] in rolled and static cultures, respectively. Cells cultured in the bioreactor displayed greater keratin expression, greater ZO-1 expression, and greater SP-C expression than their submerged counterparts, suggesting that the reactor might be a versatile tool for growing a broad array of epithelial subtypes. Scale bars: 53 µm.