Figure 2. Effects of exogenous Sonic hedgehog on in vitro angiogenesis in HUVECs on fibroblast feeder layer. Exogenenous Sonic hedgehog (Shh) enhances CD31-labeled, vessel-like tube tissue formation when compared with the control co-culture. Such enhancement of tube formation by exogenous Shh is suppressed by further addition of cyclopamine (A-C). Bar, 50 mm. Adding recombinant Shh at 5.0 nM promoted the formation of vessel-like tube formation in HUVECs as evaluated by the total length of the structure (D) and the number of the branching points (E). Further addition of cyclopamine (2.5 or 10.0 μM) suppressed the elongation and branching of the tube structure.