Abstract:Abstract: Objective To investigate the characteristics of differentiation of lung side population (LSP) cells in vitro. Methods Mouse lung tissue was taken, and mouse CD45-/CD31+ LSP cells were sorted by flow cyto-metry. Immunofluorescence was used to detect the expression of ATP-binding cassette sub-family G member 2 (ABCG2) in the isolated LSP cells. RT-PCR was applied to detect the expression of ABCG2, Tie2 and vWF in mouse CD45-/CD31+ LSP cells. After the LSP cells were cultured for 14 days, the expression of vWF was detected by immunofluorescence, and the mRNA expression of ABCG2 as well as vWF of both freshly isolated LSP cells and cultured LSP cells were examined by RT-PCR. Results Flow cytometry sorted out the CD45-/CD31+ LSP cells, and immunofluorescence tested that they expressed ABCG2. RT-PCR results revealed that LSP cells expressed ABCG2 as well as SMA and Tie2, but did not express vWF. LMP highly expressed vWF. The CD45-/CD31+ LSP cells expressed ABCG2, but did not express vWF before induction of differen-tiation; while the cells expressed vWF in stead of ABCG2 after the induction of differentiation. Conclusions CD45-/CD31+ LSP cells might be the progenitor cells of vascular endothelial cells, which possess the characteristics of stem cell differentiation, and can be differentiated into vascular endothelial cells in vitro.