Expression and Role of Oct3/4 in Injury-Repair Process of Rat Alveolar Epithelium after 5-Fu Treatment

We aimed to investigate how the embryonic stem cell-related gene Oct3/4 changes during the injury-repair process of distal pulmonary epithelium induced by 5-fluorouracil (5-Fu).

We have developed the lung injury model induced by 5-Fu and observed the dynamic changes of Oct3/4 by indirect immunofluorescence, Western blot, and quantitative real-time PCR. Immunofluorescence double staining was used to compare the positions of Oct3/4(+) cells and other reported alveolar epithelial stem cells.

Oct3/4(+) cells were not found in normal rat lung epithelial cells. However, after treatment with 5-Fu, Oct3/4(+) cells appeared at 12 h, reached the peak at 24 h, then decreased at 48 h, and eventually disappeared at 72 h. Oct3/4 was localized in the nucleus. We found that the sites of Clara cell secretory protein and surfactant protein-C dual positive cells were apparently different from Oct3/4(+) cells.

Our results revealed that, in rat alveolar epithelium, expression of Oct3/4 could be induced after treatment with 5-Fu, then decreased gradually, and was silenced following the alveolar epithelial differentiation. We hold that Oct3/4(+) cells are lung stem cells, which can provide new evidence for identification and isolation of lung epithelial stem cells.