Human endothelial cells readily differentiate on thin layers of basement matrix spread on tissue culture plastic. (A) Representative images of HUVEC forming tube-like structures after 16 hours when plated onto 10 μl/2 cm2 of basement matrix in the presence of VEGF (25 ng/ml) or medium only control. Images were acquired using Leica DMIRB microscope (x10 objective). Scale bar = 200 μM. (B) Quantification of branches formed by HUVEC at 16 hours in the presence of VEGF, or medium control. Data represent mean (± S.E.M) number of branches/field from n = 4 separate donors. *p < 0.05 vs. medium control as determined by paired Student's t-test.