Objective To explore the dynamic changes of tracheal stem cells during tracheal regeneration after injury induced by fluorouracil(5-FU) in rats. Methods Extracorporeal tracheal injury(Wistar rats) was induced by 5-FU.ABCG2 expression in tracheal epithelium during the process of regeneration was analyzed by indirect immunofluorescence and Western blotting. Results 1.After treatment with 5-FU for 12 hours,the tracheal epithelium shed and there were ABCG2 positive cells among residual cells in G-0.Three hours after the removal of 5-FU,the tracheal rings were covered with flattened epithelial cells. ABCG2 positive cells increased slightly.Six-nine hours after the removal of 5FU,the epithelial cells changed into cuboidal,correspondingly,the ABCG2 positive cells increased obviously;At 24 hours after the removal of 5-FU,most of the epithelial cells were cuboidal and merged into pieces,but the ABCG2 positive cells decreased obviously;Until 48 hours after the removal of 5-FU,only a few positive cells could be seen with the pseudostratified mucociliary epithelium restored similar to its original mode.There were no detectable ABCG2 positive cells in normal tracheal epithelium.2.Western blotting analysis showed that there were different ABCG2 levels at different times after the removal of 5-FU which in accordance with the change of immunofluorescene.ABCG2 was minimally detected after treatment with 5-FU for 12 hours,reaching a maximal level at 6 hours after the removal of 5-FU,and then decreased over time.Until 48 hours after the removal of 5-FU,very low ABCG2 level was detected.Conclusion The expression of ABCG2 is correlated to the number of tracheal stem cells,suggesting that ABCG2 may serve as a marker for isolating stem cells from tracheal epithelium.