Figure 4: Influence of collagen density on collagen degradation by MDA-MB-231 cells. MDA-MB-231 cells were cultured on collagen-coated substrates for 24 hours and then fixed. Cells were stained with F-actin (green) and DAPI (blue) and collagen was stained with collagen antibody (red). (A) Low magnification (20x) images of cells and matrix on different density surfaces after 24 hours in culture. The reduced collagen staining underneath the cells was attributed to matrix degradation, and exhibited a density-dependent behavior. Scale bar=200 μm. (B) Quantification of matrix degradation (i.e., collagen staining underneath cells) revealed increased degradation on higher density surfaces. Bars indicate statistical significance (*p < 0.005).