Innovative immunohistochemistry identifies MMP-9 expressing macrophages at the invasive front of murine HCC

Figure 2 Conglomerates of tumor associated macrophages express MMP-9 within the HCC tumor capsule. A: Immunofluorescence co-staining of collagen type I (green) and MMP-9 (red) displayed clusters of MMP-9 expressing cells in the tumor capsule. B: After photobleaching of the red fluorescence dye, macrophage marker F4/80 was visualized. The long arrows indicate MMP-9 positive macrophages. The shot arrow indicates an MMP-9 expressing cell which is negative for F4/80. DAPI was used for nucleus staining. The left panels provide a section overview with 200-fold magnification and bars represent 100 μm (left side of the panel: Tumor; dashed line: Tumor capsule; box: This is enlarged to 1000 × magnification in the corresponding panel, bars represent 20 μm). Original green and red channel micrographs (1000 ×) were shown. Images were derived by conventional wide field fluorescence microscopy. Representative digital overlays are shown.