Genetic Manipulation: Engineering Dopamine Producing Stem Cells

Abstract

Parkinson?s Disease is a neurodegenerative condition caused by the loss of midbrain neurons in the substantia nigra that synthesize the neurotransmitter dopamine. This neuronal loss results in movement, speech, and cognitive impairments that significantly impacts the quality of life in the affected individual. Currently the most widely used treatment is the administration of L-Dopa - the pre-cursor to dopamine. However this treatment is only palliative and often results in involuntary abnormal movements known as dyskinesias. Embryonic stem (ES) cells have been researched as an alternative therapy for neurodegenerative diseases because of their ability to differentiate into any tissue type as well as their ability to be transfected with foreign DNA. Transfecting ES cells with DNA driving the expression of Dopa-Decarboxylase (DDC) -- the enzyme responsible for the conversion of L-dopa to dopamine ? it is possible to create dopamine producing cell lines. During this summer experiment, Dopamine synthesis and the amount of L-Dopa concentrations have been calculated using a catecholamine extraction process and high performance liquid chromatography (HPLC). We demonstrate that ES cells can be engineered to produce large amounts of dopamine when provided with the substrate L-dopa. In culture, the cells survive and divide at rates comparable to the parental cells. These results suggest that a combination of molecular engineering with stem cell biology may produce a viable clinical alternative for the treatment of Parkinson?s Disease.