Fig. 4. Altering the EphrinB2 to EphB4 ratio results in increased tube formation in HBMVECs and increases the rate of disorganized AVMEC tube formation with redundant sprouting.

At baseline, AVMECs exhibit poor tube formation relative to that of controls. This can be seen qualitatively by incomplete tube formation and sprouting (a) as well as quantitatively by the number of completed junctions (b). Augmenting the EphrinB2/EphB4 ratio by stimulating with exogenous EphrinB2 increases the number of junctions (*p = 0.01) (b), although sprouting is redundant and disorganized compared to that of HBMVECs (a). Inhibition of EphB4 does not alter AVMEC tube formation (these cells are known to have low endogenous EphB4 expression); EphB4 inhibition subtly but consistently increases the total number of completed junctions in HBMVECs (*p = 0.02).