Figure 5. Collagen fibers are longer and more aligned in highly-metastatic (periostin^high) breast tumors.

(A) Second harmonic generation (SHG) images of collagen fibers (pseudo-colored in cyan) in EO771 or EO771.LMB mammary tumors. Scale bars: 150 μm, insets: 3x zoom. (B) Total collagen area in primary tumors (n = 3–4 mice per group). Each data point represents a different histological section. Statistics shown for Mann-Whitney test. (C) Curvature of collagen fibers, measured as mean change in angle along fibers, in primary tumors (n = 3–4 mice per group). Each data point represents a histological section. Statistics shown for unpaired Student’s t test. (D) Representative histogram of collagen fiber orientation in primary tumors. A peaked histogram represents aligned fibers whereas a flat histogram represents random organization. (E) Quantification of collagen fiber length in primary tumors, represented as a histogram (left) and scatter plot (right). Each point represents an individual fiber. 130–160 fibers quantified from multiple histological sections (n = 3 mice per group) and results compared using a Mann-Whitney test.