Fig. 2. Destabilization of endothelial-cell-monolayer integrity in co-culture spheroids of HUVECs and HUASMCs by exogenous Ang-2. Control co-culture spheroids have an intact CD31-positive endothelial-cell monolayer (A). Treatment of co-culture spheroids with Ang-1 (B) or VEGF (E) has no effect on the integrity of the surface endothelial-cell monolayer. Treatment of co-culture spheroids with Ang-2 leads to destabilization of the endothelial-cell monolayer within 4 hours, as evidenced by intense detachment of individual and groups of endothelial cells (C; high magnification in D, arrowheads). Monolayer destabilization elicited by exogenous Ang-2 is rescued by Ang-1 (F), sTie-2 (G) and VEGF (H). (I) Quantitative assessment of the Ang-2-mediated denudation by image analysis of the denuded spheroid surface area. Results are expressed as means ± s.d. of three independent experiments quantifying ten spheroids per experiment. ^**, P<0.001 compared with all other treatment groups.