Parkinson's disease is a debilitating chronic and progressive disease characterized by muscle rigidity, tremor, slowing of movement progressing to inability to move, and various difficulties with speech, posture, and cognition. It is generally agreed that the loss of a particular type of brain cell called the dopamine neuron is responsible. Drug therapy is useful in early stages but becomes less effective as the disease progresses. Dopamine cell transplantation has been successful to some degree, but has been limited by the number of cells available for transplant as well as the long term functional viability of such cells. Recently it has been shown that the exposure of human embryonic stem cells to a cocktail of growth factors leads to the production of substantial numbers of dopamine cells. Thus human embryonic stem cells may yield an inexhaustible supply of such neurons. However, the efficacy of such cells in transplant therapy depends on such cells exhibiting the necessary characteristics of dopamine cells, most importantly the ability to produce and release dopamine when transplanted into the brain. The work proposed here will allow a complete characterization of the properties of such cells in terms of their neurochemistry, degree of activity and ability to make and release dopamine. Using a variety of markers we have developed and are developing in live cells, we will be able to isolate a homogeneous population of dopamine cells produced from human embryonic stem cells and optimized for their ability to replace the function of the lost dopamine neurons in Parkinson's disease. We see this as a necessary "quality control" step to assure the maximum therapeutic value of such cells. Eventually we will transplant such functionally verified dopamine cells into animal models of Parkinson's disease as the next step to their eventual therapeutic use in human Parkinsonian patients.
Statement of Benefit to California:
Parkinson's disease is a debilitating chronic and progressive disease characterized by muscle rigidity, tremor, slowing of movement progressing to inability to move, and various difficulties with speech, posture, and cognition. The incidence of newly diagnosed Parkinson's disease in California is estimated at about 13/100,000 citizens per year. Assuming a population of 36 million in California, that yields 468,000 newly diagnosed cases of Parkinson's disease every year in California. Clearly this is one of the most prevalent neurological disorders in California. This translates into a tremendous decrease in productivity of the work force, let alone the immense cost in medical care, and the personal cost in human suffering. The ability to transform human embryonic stem cells into dopamine neurons holds probably the greatest potential for cure of this terrible disease. However, stem cells do not uniformly turn into dopamine neurons when exposed to appropriate growth factors. Thus this proposal is aimed at optimizing the transformation by finding the best conditions for transformation, followed by functional characterization of those cells by a wide variety of neurochemical and physiological assays. The result will be a homogeneous population of functionally optimized dopamine neurons that will be maximally useful for transplantation first into animal models of Parkinson's and ultimately into human patients.