The chondroitin sulfate proteoglycans neurocan and phosphacan are expressed by reactive astrocytes in the chronic CNS glial scar

• Authors: Robert McKeon, Emory University; Michael J. Jurynec, Emory University; Charles R. Buck, Emory University
• Journal Title: Journal of Neuroscience Nursing
• Volume: Volume 19, Number 24
• Publisher: Lippincott, Williams & Wilkins | 1999-12-15, Pages 10778-10788
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1523/JNEUROSCI.19-24-10778.1999
• Subjects: Biology, Cell; Biology, Physiology
• Keywords: Science & Technology; Life Sciences & Biomedicine; Neurosciences; Neurosciences & Neurology; chondroitin sulfate proteoglycans; reactive astrocytes; glial scars; axonal regeneration; CNS injury; gene expression; PROTEIN-TYROSINE-PHOSPHATASE; CENTRAL-NERVOUS-SYSTEM; CELL-ADHESION MOLECULES; GROWTH-FACTOR-BETA; NEURITE OUTGROWTH INHIBITOR; 6B4 PROTEOGLYCAN/PHOSPHACAN; BRAIN INJURY; EXTRACELLULAR VARIANT; NG2 PROTEOGLYCAN; GENE-EXPRESSION

Abstract

Chondroitin sulfate proteoglycans (CS-PGs) expressed by reactive astrocytes may contribute to the axon growth-inhibitory environment of the injured CNS. The specific potentially inhibitory CS-PGs present in areas of reactive gliosis, however, have yet to be thoroughly examined. In this study, we used immunohistochemistry, combined immunohistochemistry-in situ hybridization, immunoblot analysis, and reverse transcription-PCR to examine the expression of specific CS-PGs by reactive astrocytes in an in vivo model of reactive gliosis: that is, the glial scar, after cortical injury. Neurocan and phosphacan can be localized to reactive astrocytes 30 d after CNS injury, whereas brevican and versican are not expressed in the chronic glial scar. Neurocan is also expressed by astrocytes in primary cell culture. Relative to the amount present in cultured astrocytes or uninjured cortex, neurocan expression increases significantly in the glial scar resulting from cortical injury, including the reexpression of the neonatal isoform of neurocan. In contrast, phosphacan protein levels are decreased in the glial scar compared with the uninjured brain. Because these CS-PGs are capable of inhibiting neurite outgrowth in vitro, our data suggest that phosphacan and neurocan in areas of reactive gliosis may contribute to axonal regenerative failure after CNS injury.