Application of Embryonic Stem Cells in Parkinson’s Disease

The nervous system is a stimulating target for regenerative medicine. Parkinson’s disease (PD), which afflicts over a 1 million people in the US, is a chronic neurodegenerative disorder characterized by the degeneration and death of midbrain neurons that produce the neurotransmitter dopamine (DA), resulting in tremors at rest, an inability to initiate or complete routine movements, muscle rigidity, postural instability, and lack of facial expression. Although the etiology of idiopathic PD is not known, several predisposing factors for the dopaminergic depletion associated with the disease have been suggested, including programmed cell death, viral infection, and environmental toxins. DA neurons, in the substantia nigra pars compacta, play a prominent role in the control of many brain functions, such as voluntary movements and many behavioral processes (Maxwell & Li, 2005). These neurons can be identified via the expression of some specific transcription factors, including Engrailed 1 (EN1), PITX3, NURR1, and LMX1b, which are also very important in the development of DA neurons (Smidt et al., 2003).