Canavan disease is a fatal neurological disorder, the most prevalent form of which begins in infancy. It is caused by mutation of the ASPA gene, resulting in the deterioration of white matter (myelin) in the brain and preventing the proper transmission of nerve signals.  The mutated ASPA gene causes the buildup of an amino acid called NAA and is typically found in neurons in the brain.  As a result of the NAA buildup, Canavan disease causes symptoms such as impaired motor function, mental retardation, and early death. Currently, there is no cure or standard of treatment for this condition.

Fortunately, CIRM-funded research conducted at City of Hope by Yanhong Shi, Ph.D. is developing a stem cell-based treatment for Canavan disease. The research is part of CIRM’s Translational Stage Research Program, which promotes the activities necessary for advancement to clinical study of a potential therapy.

The results from the study are promising, with the therapy improving motor function, reducing degeneration of various brain regions, and expanding lifespan in a Canavan disease mouse model.

For this study, induced pluripotent stem cells (iPSCs), which can turn into virtually any type of cells, were created from skin cells of Canavan disease patients. The newly created iPSCs were then used to create neural progenitor cells (NPCs), which have the ability to turn into various types of neural cells in the central nervous system. A functional version of the ASPA gene was then introduced into the NPCs. These newly created NPCs were then transplanted inside the brains of Canavan disease mice.

The study also used iPSCs engineered to have a functional version of the ASPA gene. The genetically modified iPSCs were then used to create oligodendrocyte progenitor cells (OPCs), which have the ability to turn into myelin. The OPCs were also transplanted inside the brains of mice.

The rationale for evaluating both NPCs and OPCs was that NPCs typically stayed at the site of injection while OPCs tend to migrate, which might have been important in terms of the effectiveness of the therapy.  However, the results of the study show that both NPCs and OPCs were effective, with both being able to reduce levels of NAA, presumably because NAA can move to where the ASPA enzyme is although NPCs do not migrate.  This resulted in improved motor function, recovery of myelin, and reduction of brain degeneration, in both the NPC and OPC-transplanted Canavan disease mice.

“Thanks to funding from CIRM and the hard work of my team here at City of Hope and collaborators at Center for Biomedicine and Genetics, Department of Molecular Imaging and Therapy, and Diabetes and Metabolism Institute at City of Hope, as well as collaborators from the University of Texas Medical Branch at Galveston, University of Rochester Medical Center, and Aarhus University, we were able to carry out this study which has demonstrated promising results,” said Dr. Shi.  “I hope that these findings can one day bring about an effective therapy for Canavan disease patients, who currently have no treatment options.”

Dr. Shi and her team will build on this research by starting IND-enabling studies using their NPC therapy soon.  This is the final step in securing approval from the Food and Drug Administration (FDA) in order to test the therapy in patients.  

The full study was published in Advanced Science.