Researchers led by Don Lo of Duke University Medical Center and Cogent Neuroscience, Inc., in Durham, North Carolina, have developed a novel brain-slice platform for identifying therapeutic targets for neurodegenerative diseases, including Alzheimer’s, Huntington’s, and Parkinson’s, as well as stroke and glaucoma. At this month’s Neuroscience meeting, Lo’s group presented eight posters describing their various models and preliminary results of "hits" they have identified so far.
The platform is based on rodent brain slices that are biolistically transfected, that is, with a gene gun that employs a pulse of helium to fire small gold particles coated with human DNA and fluorescent reporter constructs at living brain slices, which are kept viable in culture for up to two weeks. The tissue slices retain their three-dimensional structure, enabling testing on intact living brain cells in a quasi-natural environment including surrounding glial cells.
Lo called the model "almost in vivo, essentially an animal model in a dish. We’ve used every trick in the book to recapitulate the neurologic diseases we’re interested in studying-genes, environmental insults, whatever we know causes the disorder in humans." The team presented data in Orlando on their models for stroke, glaucoma and Huntington’s disease. The effort attempts to overcome the time constraints of using transgenic animal models to test drug candidates and the high failure rate of compounds identified in cell-free protein-binding models. Lo also sees it as helping to close the "innovation gap" between academic basic research, where compounds may be discovered, and the high-throughput screening that typically occurs only at biotech and pharmaceutical firms.
The job of identifying therapeutic targets is not driven by hypotheses, Lo said: "We just throw drugs and disease genes at these models and see what blocks the pathology." So far, his group has identified some new drug candidates that have not yet been investigated for therapeutic use. They also have shown that their assays could have predicted the failure of drugs that did not show efficacy in clinical trials, including a number of the neuroprotective drugs that were investigated for stroke. While the brain-slice test confirmed that these compounds were indeed neuroprotective, the protection was seen only within a narrow set of experimental conditions, which may explain their clinical disappointment.
Once a disease model is developed, the team can screen about 1,000 genes or compounds in a matter of months, said Lo’s colleague Peter Reinhart, also at Duke and Cogent. To date, they have screened 5,000 molecules against the stroke model, and a few hundred genes and 3,000 compounds using the Huntington’s model. The method enables investigation of multigenic diseases; Reinhart said they have used as many as 11 genes in one model. The team is just beginning to screen compounds for Alzheimer’s using a model developed with combined DNA constructs for APP, tau, Aβ42 and ApoE4. (The Alzheimer’s model was not presented.)—By guest writer Brenda Patoine.
Brenda Patoine is a science writer in Lagrangeville, New York, who writes for BrainWork and other publications.
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