Mice were injected subcutaneously with 0.5 mL Matrigel alone, Matrigel with PTX (100 ng/mL), Matrigel plus bFGF (150 ng/mL) with or without PTX (100 ng/mL), Matrigel plus murine VEGF (150 ng/mL) with or without PTX (100 ng/mL), Matrigel plus bFGF (150 ng/mL) plus VEGF (150 ng/mL) with or without PTX (100 ng/mL), Matrigel plus bFGF (150 ng/mL) plus VEGF (150 ng/mL) with or without control murine IgG₁(hybridoma 11711, 200 μg/mL) or Matrigel plus bFGF (150 ng/mL) plus VEGF (150 ng/mL) with or without neutralizing monoclonal anti–SDF-1 antibody (clone 79014.111, 200 μg/mL). Mice that received PTX with Matrigel were also injected intravenously with PTX (200 ng/mouse) on days 0 and 1. Plugs were removed after 7 days, and histologic sections were stained by Masson trichrome. Results reflect the mean surface area (expressed in μm²) occupied by cells within a surface area of 10⁶ μm². Nonoverlapping fields covering the entire plug were scanned; there were 12 to 16 plug sections per group. Surface areas were measured by semi-automated digital analysis.