Fig. 3.

Heterozygous mice have increased neovasculature permeability. (A) Matrigel alone (right flank) or Matrigel containing B16-F1 tumor cells (left flank) was implanted under the skin of wild-type mice and heterozygous mice. Angiogenesis into the region of the Matrigel plug was evaluated by i.v. injection of a NIR dye (see Materials and Methods) at 7 or 10 days following implantation. There was no difference between 7 or 10 days of implantation, and both data sets were pooled into one. (a) Wild-type and (b) heterozygous mice both have a robust angiogenic response, as seen by the abundant vessel growth and branching in the left flank. However, extensive leakage from the neovasculature of the heterozygous mice was observed, as evidenced by the presence of NIR dye in extravascular regions within 4 seconds after i.v. injection. By contrast, the NIR dye remains within the vessels of the wild-type mouse after 20 seconds. (B) Ten seconds postinjection, all heterozygous mice exhibited permeability ratios >1.0, indicating leakage (gray lines). All wild-type mice maintained ratios <1.0, indicating dye retention (black lines). (C) The average permeability ratio 36 s after dye injection was significantly higher in heterozygotes than in wild types (P < 0.0001, Student's t test).