The goals of this project are to study the gene expression of growth factors, myelin~related proteins, and other glial proteins by glial cells during nervous system injury and regeneration. This year, studies on cuprizone~induced CNS demyelination in young mice were extended by studying relative levels of myelin~related protein mRNAs during demyelination and recovery. The results showed that during cuprizone administration, mRNAs for myelin basic protein (MBP), proteolipid protein (PLP), and cyclic nucleotide phosphodiesterase (CNP) decreased to a minimum 14~28 days after starting cuprizone. They rose while the drug was continued, indicating that some oligodendroglia escaped from cuprizone toxicity before the drug was stopped. After cuprizone treatment ceased, myelin~related protein mRNAs rose rapidly to levels that substantially exceeded those seen in littermate controls, a result consistent with the rapid demyelination that has been observed morphologically. We also compared relative mRNA and peptide levels of insulin~like growth factor~I (IGF~I), one of the binding proteins (IGF~BP~2), its receptor (IGF~I~R), and of glial fibrillary acidic protein (GFAP) produced by astrocytes during experimental cryogenic spinal cord injury and during experimental autoimmune encephalomyelitis (EAE). When focal lesions are produced in the dorsal columns of rat thoracic spinal cords by cryogenic injury, lesion margins are known to contain hypertrophic astrocytes and regenerating, remyelinated axons 30~60 days after injury. In situ hybridization studies with specific oligonucleotide and RNA probes showed that mRNA levels for GFAP, IGF~I and IGF~BP~2 increased in lesion margins 7~21 days after injury. Double immunostaining with cell~specific markers showed that the cells producing IGF~I mRNA and peptide were GFAP~positive hypertrophic astrocytes and not microglia or macrophages. The production of IGF~I has also been studied in EAE, a frequently studied model of the human demyelinating disease, multiple sclerosis. EAE was induced in Lewis rats; they developed characteristic clinical signs and were sacrificed 8~ 40 days post innoculation (dpi). Spinal cord sections were examined after treatment with histological stains, specific antisera, or either oligonucleotide or RNA probes. Elevated GFAP, IGF~I, IGF~BP~2, IGF~I~R mRNA and peptide levels were detected 14 dpi; they increased and peaked 26 dpi when lesions showed severe demyelination and early myelin regeneration. IGF~I were produced by astrocytes; oligoderoglia (the myelin~forming cells in the CNS) expressed IGF~BP~2 and IGF~I~R. Decreased expression of IGF~I and GFAP were observed during clinical recovery 26~40 dpi.
