MMP-7 reactivates sVEGFR-1-inactivated VEGF in angiogenesis assays. (A) Microscopic photographs of the HUVEC network formation in the tube formation assay. NC indicates incubation of HUVECs with MCDB131 medium with 0.1% BSA in the assay. VEGF indicates the medium containing 20 ng/mL VEGF. VEGF + sVEGFR-1 indicates the medium with VEGF and sVEGFR-1 incubated for 24 hours before being added to HUVECs. VEGF + sVEGFR-1 + MMP-7 indicates the medium with VEGF and sVEGFR-1 incubated for 24 hours followed by incubation with MMP-7 for 24 hours before being added to HUVECs. Bars represent 500 μm. (B) Quantification of tube length in the tube formation assay. *P < .01, n = 4. (C) Quantification of HUVECs that migrated in the migration assay. *P < .01, n = 3.