During the first year of funding we have made significant progress toward the goals of the funded CIRM grant TR1-01257: Sustained siRNA production from human MSC to treat Huntington’s disease and other neurodegenerative disorders.
The overall goal of the grant is to use human mesenchymal stem cells (MSC) as safe delivery vehicles to knock down levels of the mutant Huntingtin (htt) RNA and protein in the brain. There is mounting evidence in trinucleotide repeat disorders that the RNA, as well as the protein, is toxic and thus we will need to significantly reduce levels of both in order to have a durable impact on this devastating disease.
This year we have shown that human MSC engineered to produce anti-htt siRNA can directly transfer enough RNA interfering molecules into neurons in vitro to achieve significant reduction in levels of the htt protein. This is a significant achievement and a primary goal of our proposed studies, and demonstrates that the hypothesis for our proposed studies is valid. The transfer occurs through direct cell-to-cell transfer of siRNA, and we have filed an international patent for this process, working closely with our Innovation Access Program at UC Davis. A manuscript documenting the results of these studies is in preparation.
We continue to explore the precise methods by which the cell-to-cell transfer of small RNA molecules occurs, working in close collaboration with the national Center for Biophotonics Science and Technology at UC Davis. This Center is located across the street from our CIRM-funded Institute for Regenerative Cures (IRC) where our laboratory is located, and has equipment that allows visualization of protein-protein interactions in high clarity and detail. The proximity of our HD team researchers in the IRC to the Center for Biophotonics has been an important asset to our project and a collaborative manuscript is in preparation.
During year two of the proposed studies we will continue to document levels of reduction of the toxic htt protein in different types of neurons, including medium spiny neurons (MSN) derived from HD patient induced pluripotent stem cells (iPSC). We have made significant advances in developing the tools for these studies, including HD iPSC line generation and MSN maturation from human pluripotent cells in culture. A manuscript on improved techniques for generating MSN from pluripotent cells is in preparation. We have also worked closely with our colleagues at the UC Davis MIND Institute to achieve improved maturation and electrical activity in neurons derived from human pluripotent stem cells in vitro, and we are examining the impact of human MSC on enhancing survival of damaged human neurons.
In the second year of funding we will test efficacy of the siRNA-mediated knockdown of the mutant human htt RNA and protein in the brains of our newly developed strain of immune deficient Huntington’s disease mice. This strain was developed by our teams at UC Davis to allow testing of human cells in the mice, since the current strains of HD mice will reject human stem cells. A manuscript describing generation of this novel HD mouse strain is in preparation, in collaboration with our nationally prominent Center for Mouse Biology.
Behavioral studies will be conducted in this strain with and without the MSC/siRNA-mediated knockdown of the mutant protein, through years 2-3, in collaboration with our well established mouse neurobehavioral core at the UC Davis Center for Neurosciences. We have documented the safety of intrastriatal injection of human MSC in immune deficient mice and will next test the efficacy of human MSC engineered to continually produce the siRNA to knock down the mutant htt protein in vivo.
As added leverage for this grant program, and supported entirely by philanthropic donations from the community committed to curing HD, we have performed IND-enabling studies in support of an initial planned clinical trial that will use normal donor MSC (non-engineered) to validate their significant neurotrophic effects in the brain. These trophic effects have been documented in animal models. The planned study will be a phase 1 safety trial. We have completed the clinical protocol design and have received feedback from the Food and Drug Administration. We will be conducting additional studies in response to their queries, over the next 6-10 months, through a pilot grant obtained from our Clinical Translational Science Center (CTSC), which is located in the same building as our Institute. Upon completion of these additional studies we will submit the updated IND application to the FDA. MSCs for this project have been expanded and banked using standard operating procedures in place in the Good Manufacturing Practice Facility in the CIRM/UC Davis Institute for Regenerative Cures.
From the funded studies 4 manuscripts are now in preparation, a chapter is in press and a review paper on MSC to treat neurodegenerative diseases is in press.