Ongoing degeneration and death of dopaminergic (DA) neurons in the midbrain is the hallmark of Parkinson’s disease (PD), a movement disorder that manifests with tremor, bradykinesia and rigidity. Existing therapies for PD are only palliative and treat the symptoms but do not address the underlying cause. Levodopa, the gold standard pharmacological treatment to restore dopamine, is compromised over time by decreased efficacy and increased side effects. Neurosurgical treatments, such as pallidotomy, thalamotomy and deep brain stimulation are considered after failure of pharmacological treatment.
Cell replacement therapy involves grafting cells that produce dopamine into the striatum. The proof of principal of this approach has been demonstrated in human PD patients using human brain tissue. However, stem cells are currently the only potential source of reliable, continuous, homogenous and qualified populations of DA neurons for cell therapy. Likewise, the inherent properties of stem cells make them indispensable for investigations aimed at unraveling disease mechanisms for disease modeling and drug discovery.
Although human embryonic stem cells (hESCs) potentially offer an unlimited source of cells for cell therapy, to date variations in the efficiency of dopaminergic cell generation, the heterogeneous cellular composition and supply limitations, prevented this therapeutic approach from moving forward towards clinical application. The downstream genetic control of the DA inductive process has not been fully elucidated. Consequently, we are still unable to control the generation of DA neurons from stem cells in vitro or able to control and predict the number of DA-expressing neurons in vivo after transplantation.
Undefined cell populations could lead to unpredictable side effects. Thus, the composition of the graft and the proportion of DA neurons in the cell preparation impact the beneficial outcome.
To advance cell replacement therapy and drug discovery for PD patients, applied stem cell biology is critical to determine the composition of the therapeutic cellular product and to control the proportion of dopamine and other lineages present. The only way to achieve this goal is to master the generation of specific neural lineages.
In this application we propose to define the molecular determinants controlling the generation of the DA phenotype in the A9 DA neurons, the type of DA neurons that consistently promote functional recovery in animal models of PD. This will enable us to induce not only pure DA neuronal populations but to also control the production and proportion of DA neurons in the human neural stem cell cultures and preparations used for cell transplantation.
Knowledge from these studies will unravel the gene network involved in the induction, maintenance and stabilization of the DA phenotype, characteristics that are critical to the success of the therapeutic efficacy of the cells.
We have isolated a human neural stem cell line from embryonic stem cells with midbrain properties that we believe is optimal for developing a potential therapeutic product to treat Parkinson’s disease. However the molecular determinants controlling the generation of the dopaminergic neurons are still not fully understood, which could compromise the success of the product development and the therapeutic strategy.
We have proposed three aims to define the core transcriptional regulatory circuit controlling the generation of the A9 dopaminergic neurons, the type of cells that consistently promote functional recovery after transplantation in animals models of PD. This will enable us to induce not only pure dopaminergic neuronal populations but to also control the production and proportion of dopaminergic neurons in the human neural stem cell cultures and preparations for therapeutic use.
We believe these experiments will provide the foundation for developing a consistent, predictable, safe and efficacious cellular product for Parkinson’s disease patients. This technology will generate intellectual property that will be made available for California based companies to develop and commercialize. All tools and technologies that we develop will be made available to all Californian based scientists in non-profit and industrial organizations. We expect that the money spent on this project will benefit the California research community and will accelerate the research toward developing an efficacious and safe cellular product for treating Parkinson’s disease.