The Role Of Vimentin In Glial Scar Formation

The injury of adult mammalian CNS leads to a complex series of cellular and molecular events, as cells respond to trauma and attempt to repair damaged regions of brain or spinal cord. Unlike the successful healing responses in the peripheral nervous system, adult CNS injury leads to permanent disability, because most severe injured axons fail to regenerate, which was early noticed by Cajal in 1928. The swelling of glial cell nucleus, bodies and processes, likely accompanying hyperplasia and hypertrophy of the glial cells are the principal pathological manifestation being called reactive gliosis and glial scar. In the immediate vincity of injuried site, astrocytes become 搑eactive,?with dramatically elevation of levels of cytoskeletal elements, membrane proteins, and extracellular components. These reactive astrocytes participate in the repair process by forming a scar, reestablishing a glial limiting membrane. The astrocytic scar protects the parenchyma of the CNS from exposure to external, non-CNS environment. The glial scar and the immediate environment are believed to represent a physical or molecular barrier disrupting the continuity of previously established axonal pathways. The disruption may contribute to the lack of axonal regeneration in the CNS. Up-to-now the mechanism of glial scar is still unclear. Not only does glial fibrillary acidic protein express markedly in reactive astrocyte, another main intermediate filament-vimentin (Vim) that expresses normally at the developmental period re-appears in glial cell following adult CNS injury. It suggests that Vim may contribute to glial scar formation and has some relation III with GFAP. Former study focused on the effect of GFAP and little attention had been paid to the effect of Vim during glial scar formation. In this study we have established a model with stab wound of cerebrum in vivo to test thoroughly the expression of Vim. Then the effect of ciliary neurotrophic factor (CNTF) on reactive gliosis was studied. Antisense and sense Vim recombinant retroviruses were constructed and used both in vivo and in vitro to test the effect of Vim in the formation of glial scar and the relation between GFAP and Vim. The results are as follows: 1.Expression of Vim after stab wound in rats cerebrum After stab wound in rat cerebrum Vim RNA increased markedly at the immediate wound site by retro-transcription PCR; Vim positive intmunostaining cell appeared at the region of molecular layer of cortex, corpus callosum and hippocampus of wounded rats. The number of GFAP positive immunostaining cell was larger than that of Vim positive cell. Hyperplasia and hypertrophy of glial cell was obvious at 1 week after injury. It was obsearved that densely interwoven processes formed glial scar at 4 weeks after injury. The number of Vim positive immunostaining cell also increased signiflcently measuring by flow cytometry. 2.The effect of ciliary neurotrophic factor on glial scar formation We studied the expression of GFAP after human recombined CNTF was given into wound track in vivo. Increased GFAP expression by immunohistochemistry dependent on the dosage of CNTF was obsearved during 7-weeks period. Also it can be at the contralateral uninjured cerebral region a distance away from stab site. The expression of Vim and GFAP in vitro was enhanced when CNTF added, which might not be achieved by rising the concentr...