The role of swollen astrocytes in human brain lesions after edema--an immunohistochemical study using formalin-fixed paraffin-embedded sections.

Swollen astrocytes (SAs) in the white matter after brain edema were immunohistochemically studied in cases with cerebral vascular events, brain tumor and protracted non-missile head injury. SAs showed a decrease in reactivity to glial fibrillary acidic protein (GFAP) and, on the other hand, were positive for laminin, an extracellular matrix glycoprotein known to be secreted by astrocytes. SAs in protracted lesions were strongly positive for both vimentin and plasma proteins including IgG, IgM, C3d and C4d. Remarkable vimentin expression in SAs, instead of GFAP, strongly suggests that SAs are not going to degenerate but are bearing up to regenerate in such circumstances. A number of vimentin-positive buttons also appeared in such protracted lesions, demonstrating disintegration of the processes of SAs. Immunohistochemical detection of plasma proteins in SAs are believed to indicate a facilitated activation in SAs to transform to macrophage-like cells and to act as phagocytes. In addition, demonstration of laminin may suggest hyperactivity of laminin production in SAs after both axonal injury and concomitant edema in order to stimulate neuritic regeneration.