Sprouting of endothelial spheroids and tube formation of HUVECs depend on CD44v6. (A) Sprouting from spheroids of HUVECs was measured as described in “Sprouting assay.” Growth factor and peptide treatments are indicated. Pictures were taken after 48 hours, and sprouting was quantified using the computer program ImageJ. (B) Tubule formation induced by growth factors and peptides as indicated was quantified by counting the branching points or the total vessel length per field using the computer program ImageJ. An example for VEGF-A165 is shown. *Statistical significance (P < .05). The SD was calculated from 3 independent experiments.