No abstract

Midkine (MK) is the product of a retinoic acid responsive gene and is a member of a new family of heparin-binding growth factors. Neurotrophic effects of MK were examined using cultured spinal cord and dorsal root ganglion (DRG) neurons derived from fetal mouse. MK, which was added to the culture medium at concentrations of 1-100 ng/ml, promoted survival of both types of neurons approximately 5-fold after 7 days in culture. For spinal cord neurons, the increased survival was reflected in an increase of choline acetyltransferase activity. MK also promoted neurite extension in spinal cord (2-fold) and DRG (1.7-fold) neurons. The survival-promoting activity of MK to these neurons was comparable to that of basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF). In spite of its significant effects on fetal neurons, MK was ineffective in sustaining survival of DRG neurons derived from postnatal mice. From these results, we conclude that MK is a neurotrophic factor to embryonic spinal cord and DRG neurons, and we propose that MK plays a significant role in embryogenesis of the nervous system.

Enriched populations of oligodendrocytes were isolated from adult human brains of 3-15 hours postmortem using the trypsinin digestion-Percoll density gradient method and were cultured for an extended period of time up to 6 months. Cell type specific antigens that were expressed by oligodendrocytes were galactocerebroside, myelin basic protein, proteolipid protein, 2'3'-cyclic nucleotide 3'-phosphohydrolase and myelin-associated glycoprotein. In addition, HLA-A,B,C and HLA-DR, respectively, Class I and Class II antigens of the major histocompatibility complex, were demonstrated on oligodendrocytes. Three classes of gangliosides, GM1, GM4, and GD3, were also demonstrated on oligodendrocytes, while GM1 and GM4 gangliosides were detected on the surface of astrocytes. The presence of "transitional" or "bipotential" glial cells that were derived from oligodendrocytes and that expressed both oligodendroglial and astrocytic phenotypes was demonstrated. Treatment of the cells by cyclic AMP and its derivatives reversed this dual phenotypic expression back to the oligodendroglial trait. Electron microscopic examination of oligodendrocytes indicated that they were capable of synthesizing and assembling myelin sheaths in culture in the absence of any neuronal signal input.

Neural stem cells (NSCs) of the central nervous system (CNS) recently have attracted a great deal of interest not only because of their importance in basic research on neural development, but also in terms of their therapeutic potential in neurological diseases, such as Parkinson's disease (PD). To examine if genetically modified NSCs are a suitable source for the cell and gene therapy of PD, an immortalized mouse NSC line, C17.2, was transduced with tyrosine hydroxylase (TH) gene and with GTP cyclohydrolase 1 (GTPCH1) gene, which are important enzymes in dopamine biosynthesis. The expression of TH in transduced C17.2-THGC cells was confirmed by RT-PCR, Western blot analysis, and immunocytochemistry, and expression of GTPCH1 by RT-PCR. The level of L-DOPA released by C17.2-THGC cells, as determined by HPLC assay, was 3793 pmol/10 6 cells, which is 760-fold higher than that produced by C17.2-TH cells, indicating that GTPCH1 expression is important for L-DOPA production by transduced C17.2 cells. Following the implantation of C17.2-THGcC NSCs into the striata of parkinsonian rats, a marked improvement in amphetamine-induced turning behavior was observed in parkinsonian rats grafted with C17.2-THGC cells but not in the control rats grafted with C17.2 cells. These results indicate that genetically modified NSCs grafted into the brain of the parkinsonian rats are capable of survival, migration, and neuronal differentiation. Collectively, these results suggest that NSCs have great potential as a source of cells for cell therapy and an effective vehicle for therapeutic gene transfer in Parkinson's disease.