Long-Term Culture of Distal Airway Epithelial Cells Allows Differentiation Towards Alveolar Epithelial Cells Suited for Influenza Virus Studies

Imai-Matsushima, Aki; Martin-Sancho, Laura; Karlas, Alexander; Imai, Seiichiro; Zoranovic, Tamara; Hocke, Andreas C.; Mollenkopf, Hans-Joachim; Berger, Hilmar; Meyer, Thomas F.

Next, we examined alveolar epithelial cell markers by immunofluorescence staining of AQP5 and SP-C (Fig. 4E) . We also detected increased expression of surfactant proteins over time (Fig. 4F ). The induced cells showed a spectrum of populations with different staining intensities of ProSP-C and AQP5 (Fig. 4G) , shifting from mainly ProSP-C + cells at 48 h to mainly ProSP-C-/AQP5+ cells at 144 h of differentiation. These results are in congruence with the view that type II cells spontaneously differentiate into type I cells [26, 27] . Cellular morphology also changed from a type II-like to a large, flat type I-like phenotype (Suppl. C − /AQP − cells increased to 89.7% by 144 h, and ProSP-C + /AQP5 − cells were not detected without induction (Fig. 4G) . A comprehensive schematic illustration of primary DAEC expansion and differentiation is included in Fig. 8 .