Parkinson’s Disease (PD) is a devastating disorder that is caused by the loss of a particular type of neuron in the brain. PD patients show movement abnormalities which worsen over time and significantly reduce the quality of life. Current treatments reduce the severity of these problems but very often the efficacy of these treatments gradually weakens over time leaving patients with few therapeutic options, some of which carry significant unwanted side effects. Since the development of growing undifferentiated human stem cells in the late 1990’s, much has been learned in regards to how to make these cells develop into neuronal cells, in particular the same type of neuron that is lost in a PD patient. Therefore, a cellular therapy has been envisioned for the treatment of PD, however, the complex nature of this disease requires higher level models in which potential therapies can be accurately evaluated before moving a therapy to clinical trials.

Previous work using human fetal tissue showed improvement of PD symptoms in an animal model and human clinical trials, however, distinctive movement abnormalities arose from the use of this treatment and combined with the ethical issues, it is not a viable therapeutic strategy. Recent work suggests that the use of embryonic stem cells for the treatment of PD may be possible but a direct comparison of the different types of cells derived from these was lacking. Additionally, tumors caused by these cells have been reported.

Our research efforts funded by this CIRM award allowed us to complete the largest stem cell therapy comparison for PD using the most accurate disease model available. Over the last 3 years we have evaluated the efficacy of 8 potential therapeutic cell types and 2 control cell types (in addition to various other control groups to rule out any possibility that the observations may have resulted from something other than cells). From these efforts we have confidently identified a strategy for producing cells that show a dramatic reduction in the PD symptoms in this model and these cells will be developed for clinical trials. Furthermore, we have incorporated a critical step for ensuring the safety of this cell therapy by including a purification technique that removes cells that may give rise to tumors or produce unknown or unwanted effects.