Macrophage recruitment into a Matrigel plug is decreased in S100A10^−/− mice. WT and S100A10^−/− mice were implanted with a Matrigel plug containing 200 ng/mL basic fibroblast growth factor and 60 U/mL heparin. Plugs were removed after 7 days, fixed in formalin, and processed for immunohistochemical analysis. Sections were deparaffinized and incubated with anti-Mac-3 (A top panel, C) and anti-F4/80 antibody (A bottom panel). Microscopic fields containing the entire Matrigel plug (B), outer tissue surrounding the plug, Matrigel-tissue border, and center of Matrigel (D) were quantified by determining the percentage coverage of macrophages in each region using ImageJ software. Results are expressed as percentage of macrophages per field plus or minus SD of 3 independent experiments. Statistical analysis was performed by Student t test: ***P < .001. Arrows indicate the Matrigel-tissue border.