During the second 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. During the second year we have more fully characterized our development candidate; MSC/anti-htt. We have documented that normal human donor 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. We reported this work at the Annual meeting of the American Academy of Neurology (G Mitchell, S Olson, K Pollock, A Kambal, W Cary, K Pepper, S Kalomoiris, and J Nolta. Mesenchymal Stem Cells as a Delivery Vehicle for Intercellular Delivery of RNAi to Treat Huntington’s disease. AAN IN10-1.010, 2011) and have recently completed and submitted a manuscript describing these results (S Olson, A Kambal, K Pollock, G Mitchell, H Stewart, S Kalomoiris, W Cary, C Nacey, K Pepper, J Nolta. Mesenchymal stem cell-mediated RNAi transfer to Huntington’s disease affected neuronal cells for reduction of huntingtin. Submitted, In Review, July 2011).
We have explored the molecular 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-siRNA 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. This work was also presented at AAN 2011, and a collaborative manuscript is in preparation for submission (S Olson, G McNerny, K Pollock, F Chuang, T Huser and J Nolta, Visualization of siRNA Complexed to RISC Machinery: Demonstrating Intercellular siRNA Transfer by Imaging Activity. MS in preparation, Presented at AAN 2011: IN4-1.014).
In the second year of funding we developed the models for in vivo efficacy testing of the siRNA-mediated knockdown of the mutant human htt RNA and protein in the brains of established and new strains of Huntington’s disease mice. Behavioral studies were conducted in two strains, the R6/2 immune competent mice and our new immune deficient strain, the NSG/HD, in comparison to normal littermate controls that are not affected by HD. We established the batteries of behavioral tests that are now needed to test efficacy of our development candidate in the brain, in year three. Established tests include rotarod, treadscan, pawgrip, spontaneous activity, nesting, locomotor activity, and the characteristic HD mouse hindlimb clasping phenotype. In addition we monitor the status of weight and tremor, grooming, eyes, hair, body position, and tail position, which all change over time in HD mice. These tests are conducted at 48 hour intervals by two highly trained technicians who are blinded to the treatment that the mouse had received. These behavioral and phenotypic tests have been established at the level of Good laboratory practices in our new Institute for Regenerative Cures shower-in barrier facility vivarium. We have documented the biosafety of intrastriatal injection of human MSC in immune deficient mice and are now examining the in vivo efficacy of the development candidate: human MSC engineered to continually produce the siRNA to knock down the mutant htt protein in vivo, which will be completed in year three.
As added leverage for this funded 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.