Promising Outcomes of Original Grant:
Recombinant plasmid DNA encoding for glial cell line-derived neurotrophic factor (GDNF) was compacted into nanoparticles, injected safely into the brain, and successfully transfected brain cells to over-express GDNF and provide neurotrophic support for dopamine neurons. The results of the original studies closely supported the hypothesis that compacted DNA nanoparticles could be used to deliver plasmid DNA to brain cells and produce transgene expression of GDNF that was beneficial to dopamine neurons.
Objectives for Supplemental Investigation:
In this project, we will compare the long-term transgene expression of several plasmids encoding for GDNF. One plasmid, pGDNF, has already demonstrated stable expression and neuroprotection in the brain and other plasmids will be optimized for long-term expression using a novel expression element. We will inject the compacted plasmids into the brains of animals with experimental Parkinson’s disease. Studies will be designed to assess GDNF protein and mRNA expression (endogenous and transgene) in the brain over a six month period as well as determine if this treatment results in improvement of motor function. This study is a collaborative project between my laboratory and Copernicus Therapeutics, Inc. (Cleveland, Ohio).
Importance of This Research for the Development of a New PD Therapy:
The results from our studies indicate that compacted DNA nanoparticles can be used as a non-viral gene therapy technique to deliver therapeutic genes to brain cells. In particular, we have demonstrated that compacted DNA nanoparticles can deliver a therapeutic gene encoding for GDNF to the nigrostriatal pathway and successfully overexpress GDNF in the striatum, which has been shown to be therapeutic in patients suffering from Parkinson’s disease.
In this optimization study, the research team tested various GDNF plasmids and compared GDNF DNA incorporating sequences. The group reported the results from a dose-response study that used four different pGDNF expression plasmids that were compacted into nanoparticles and then injected into the striatum. Protein analysis for GDNF in striatal tissue samples were determined one week later and it was determined that a plasmid encoding for natural GDNF provided the best transgene expression (of note, a different variant is used in most preclinical studies) resulting in GDNF protein levels that were more than 400 perecent higher than baseline levels for at least an eight-week period.
The optimized plasmid from the dose-response study is currently being tested in a longitudinal study of GDNF overexpression in the striatum; if necessary, a proprietary element that confers long term expression of other transgenes will be included in the plasmid design. The ultimate goal of our studies is to design a GDNF expression plasmid that can be compacted into nanoparticles, injected into the brain, and then produce long-term transgene expression of GDNF in the striatum.
Yurek, D. M., Fletcher, A. M., Kowalczyk, T. H., Padegimas, L., and Cooper, M. J., 2009. Compacted DNA nanoparticle gene transfer of GDNF to the rat striatum enhances the survival of grafted fetal dopamine neurons. Cell Transplant, in press.
Yurek, D. M., Fletcher, A. M., Smith, G. M., Seroogy, K. B., Ziady, A. G., Molter, J., Kowalczyk, T. H., Padegimas, L., and Cooper, M. J., 2009. Long-term transgene expression in the central nervous system using DNA nanoparticles. Mol Ther 17, 641-650.