Quantification of angiogenesis as a function of scaffold depth at day 14. CD31-positive vessels in scaffold sections were outlined with red, blue and green color for 0-200 μm, 200-400 μm and 400-600 μm intervals, respectively (A). The vessel density (B) and percentage of area occupied by vessels (C) was evaluated at 200-μm intervals. Values represent the mean and standard deviation (n=4). V0 and V10 represent scaffold without VEGF and loaded with 10 μg of VEGF, respectively. H0 and Hm represent scaffolds without heparin and with heparin cross-linked for 15 hours, respectively.