Figure 1

Collagen morphology and the epithelial-stromal interaction in the mammary gland. (A) Picrosirius red staining (red), a selective collagen stain, indicating the primary stromal component is collagen (bar = 50 μm). (B) Low magnification (bar = 10 μm) TEM image of a mouse mammary duct (transverse section) showing the organization of epithelial (e) and myoepithelial (me) cells outside the lumen (L) in close association with the collagenous stroma (s), with myoepithelial cells not completely separating the stroma from the epithelial cells. (C) SEM image of the ductal end. (D) SEM image of collagen fibers interacting with ductal epithelial cells. (E) SEM image of collagen bundles wrapping around the cell in multiple directions. (F) Collagen fibrils possessing a rod-like structure with the characteristic ~67 nm banding pattern validating the presence of fibrillar collagen in proximity to epithelial cells. (G) SEM image of collagen fibrils immediately adjacent to the cell surface. (H) TEM image of collagen fibrils (col) next to the epithelial cell (e).