FIG. 4.

Mesenchymal cells expressing high levels of Flk-1 express VE-cadherin but still lose their endothelial phenotype on EGM-2 removal. (A) Mesenchymal cells were cultured in EGM-2 for 7 days and sorted based on Flk-1 expression. The cells with highest Flk-1 expression (indicated by small box inset) were isolated, expanded, and analyzed again by FACS. (B) VE-cadherin expression is shown in original cells (left panel) and in Flk-1 sorted cells after expansion (right panel). (C, D) Phase contrast images of cells before and after sorting based on Flk-1 expression. (E) The majority of Flk-1 sorted cells expressed cell surface VE-cadherin. Only a few cells expressed α-SMA. (F) On removal of EGM-2 media, more cells with α-SMA positive stress fibers were observed. (G, H) EGM-2 removal led to reduced Flk-1 expression and increased α-SMA expression in cells originally sorted based on Flk-1 expression (*P<0.05, n=6).