Figure 8.

Schematic summary of ERK2 cKO astrovascular phenotype. In control mouse cortex (left panel), reticulin-positive fibrillar collagen (blue) is limited to the pia/arachnoid and Virchow-Robbins spaces surrounding penetrating arterioles. In ERK2 cKO mice (right panel), fibrillar collagen accumulates in parenchymal neuropil in the form of short fibrils. Additional reticulin-positive material, probably a precursor to fibrillar collagen and not recognized by mAb F1C3 or anti-collagen I antibodies, also accumulates around all cortical capillaries in cKO cortex. Abnormal string vessels are found selectively in regions with elevated fibrillar collagen deposition, and perivascular astrocytes show elevated GFAP. The results suggest a model in which pericapillary astrocytes regulate either the production or the degradation of fibril-forming collagens via an ERK2-dependent signaling pathway.