Figure 5.

Histochemical and Immunohistochemical demonstration of collagen fibrils in cKO cortex. Sirius Red staining with polarized illumination reveals collagen fibrils in cKO cortex (B) but not littermate controls (A). Electron microscopy (C) reveals pericapillary collagen fibrils (arrows) in cKO cortex, not seen in control pericapillary matrix. D: Monoclonal antibody F1C3, specific for a conserved epitope on collagens I, III, and V, shows selective staining of parenchymal fibrils (arrowheads) in ERK2 cKO mice. Pial surface and vascular F1C3 immunoreactivity (arrows) was present in cKO as well as wild type cortex. E: Affinity-purified anti-collagen I antibody also labels parenchymal fibrils (arrowheads) in cKO cortex. Choroid plexus, known to contain abundant fibrillar collagen, serves as an internal positive control (corner inset, E) detected in both cKO and wt mice. Scale bars represent 50 μm (A, B, D, E) and 1 μm (C).