Neurospheres modified to produce glial cell line-derived neurotrophic factor increase the survival of transplanted dopamine neurons
Glial cell line-derived neurotrophic factor (GDNF) has been shown to increase the survival of dopamine neurons in a variety of in vitro and in vivo model systems. Therefore, it constitutes an important therapeutic protein with the potential to ameliorate dopamine neuronal degeneration in Parkinson's disease or to support dopamine neuronal replacement strategies. However, biophysical and practical considerations present obstacles for the direct delivery of the GDNF protein to CNS neurons. Here we show that rodent neural precursor cells isolated and expanded in culture as neurospheres (NS) can be genetically modified to express green fluorescent protein (GFP) or to release GDNF using lentiviral constructs. GDNF-NS increased the fibre outgrowth of primary embryonic dopamine neurons in cocultures, showing that the protein was released in biologically significant quantities. Furthermore, after transplantation into the 6-hydroxydopamine-lesioned rat striatum, GDNF-NS significantly increased the survival of cografted primary dopamine neurons. However, this was not reflected in behavioural recovery in these animals. We found that, by 6 weeks, few cells expressed GDNF or GFP, suggesting either that transgene expression was down-regulated over time or that the cells died. This may explain the initial effects on dopamine neuronal survival within the graft but the lack of long-term effect on subsequent fibre outgrowth and behaviour. Providing sustained levels of neural precursor-mediated transgene expression can be achieved following transplantation in the future; this approach may prove beneficial as an alternative therapeutic strategy in the cell-based management of Parkinson's disease.
Keywords: Animals ; Astrocytes/cytology ; Behavior ; Animal ; Cell Survival ; Cells ; Cultured ; Denervation ; Disease Models ; Animal ; Genetic Vectors ; Glial Cell Line-Derived Neurotrophic Factor ; *Graft Survival ; Green Fluorescent Proteins ; Indicators and Reagents/metabolism ; Lentivirus/genetics ; Luminescent Proteins/genetics ; *Nerve Growth Factors ; Nerve Tissue Proteins/*biosynthesis ; Neurites/physiology ; Neurons/*transplantation/ultrastructure ; Oxidopamine ; Parkinsonian Disorders/*surgery ; Rats ; Rats ; Sprague-Dawley ; *Stem Cell Transplantation ; Stem Cells/*metabolism ; Sympatholytics ; Animal ; Animal ; Rats
Cambridge Centre for Brain Repair, University of Cambridge, Forvie Site, Cambridge, United Kingdom.
Record created on 2008-08-27, modified on 2016-08-08