Effect of PF-4–derived peptides on angiogenesis in vitro. ACE cells are grown onto 3-dimensional collagen type I gels in the presence of 10 ng/mL FGF-2 (A) or VEGF (B) in the presence or absence of 10 μmol/L of the different peptides. Photomicrographs were taken after 7 days incubation. Results were quantified as indicated in Materials and Methods and expressed as the mean ± SD of experiments done in duplicates.