To observe the growing conditions and transdifferentiation of type Ⅱ alveolar epithelial cell (AEC Ⅱ) in vitro.

Primarily culture AEC Ⅱ were isolated and purified by differential adhesion methods, the cells were divided randomly into 0 day, 2 days, 4 days, 6 days and 8 days groups, respectively. The growing conditions of AEC Ⅱ and the cells number under the inverted microscope were recorded, the growth curve was drawn based on the cells number at every time point. Cell activity was observed with the typan blue dye exclusion method. The flow cytometry assayed the cell cycle and cell apoptosis, and the electron microscope was used to observe ultra cellular structures. The immunity fluorescence technology was used to observe the positive expression of surfactant protein C (SP - C) and aquaporin 5 (AQP5) by laser confocal microscopy.

The cell number at 0 day, 2 days, 4 days, 6 days and 8 days was (4.02±0.99)×10⁸L^-1, (10.41±0.24)×10⁸L^-1, (27.90±1.91)×10⁸L^-1, (27.12±0.85)×10⁸L^-1 and (26.29±1.59)×10⁸L^-1, respectively, the cell number was statistically different compared 2 days with 0 day and 4 days with 2 days (P_a<0.05). The cell activity at 2 days, 4 days, 6 days, 8 days was (97.00±0.71)%, (97.20±0.84)%, (95.00±0.71)% and (92.80±1.30)%, respectively, the difference of cell activities was statistical significant compared 6 days with 4 days, 8 days with 6 days (P_a<0.05). Cell cycle showed that in air group, the cell ratio of G1 phase and S phase were highest partly at 6 days and 4 days, but the ratio at each time spot had no statistical significant difference compared with preceding time spots (P_a>0.05). Cell apoptosis showed that in air group, the proportion of Annexin - V⁺/PI^- subgroups was highest at 4 days, but it had statistical significant difference compared with 2 days and 6 days (P<0.05). The Annexin - V⁺/PI⁺ subgroup cells accounted for the proportion to be highest at 8 days, and the difference had not statistically significant compared with 6 days (P>0.05). But the difference was statistically significant between at 6 days and at 4 days (P<0.05). Cell cellular structures indicated that there were some cells which were situated between AECⅡ and AEC Ⅰ state. This kind of cells had the microvilli on the cell surface but had no lamellar bodies in intracytoplasm, and some of these cells had lamellar bodies in intracytoplasm but had no microvilli on the cell surface. Immunity fluorescence showed that SP - C positive green fluorescence could be observed in some of cell cytoblastema at 6 days, fluorescence intensity was a little weaken than that at 2 days and 4 days, and the positive red fluorescence AQP5 in these cells could be also observed, whose fluorescence intensity was different to each other, the cells with less AQP5 had more SP - C expression. The fluorescence was strongest at 4 days and decreased gradually afterward.

Originally cultured AECⅡ has the strongest multiplication ability in the early culture time, and its multiplication and differentiation ability decreased in the late culture time. The AEC Ⅱ cultured in vitro can be transdifferentiated into AEC Ⅰ.

type Ⅱ alveolar epithelial cell; growth condition; transdifferentiation; surfactant protein C; aquaporin 5