Infiltration of parenchyma by SVMs after injury. (A) SVMs infiltrated the stratum oriens of the hippocampus in injured mice (right panel) but not in sham animals (left panel). cSO, contralateral stratum oriens of hippocampus; ffx, fimbria/fornix; lv, lateral ventricle; th, thalamus. (B) SVMs migrate significantly farther into parenchyma of injured animals compared to sham injury (*p < 0.01). (C) Infiltration of hippocampus begins days after injury and cells remain for weeks (*p < 0.05 compared to sham). (D) Temporal pattern of infiltration corresponds to neuropil degeneration (black punctate staining, bottom left) activation of resident microglia (shown by increased IB4 staining, bottom middle) and glial activation (indicated by phospho-ERK immunoreactivity, bottom right). GSD, Gallyas silver degeneration stain; pERK, phospho-extracellular signal-related kinase.