The Use of Stem Cells in the Treatment of Parkinsons Disease

Parkinsons disease (PD) is a degenerative neurological disorder characterized by the cardinal motor features of tremor, bradykinesia and rigidity. It is associated with the extended loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc) resulting in a severe deficiency of DA in the striatum required for motor control. There is currently no cure for PD and the majority of treatments available aim to reverse dopamine deficiency and the relief of the symptoms. Based on promising findings from early trials, the transplantation of stem cells or stem cell derived progenitors has raised the possibility of using cell-based therapy to replace lost cells in the diseased brain. Embryonic stem cells (ESCs) are highly expandable and pluripotent cells that have the ability to differentiate into all cell types of the human body, including nervous system tissues, meaning that they have the potential to offer a lasting treatment for PD and other neurological diseases. However, possible issues with safety and ethics associated with the use of undifferentiated ESCs in humans have meant that alternative sources of transplantable cells has to be considered. Additionally, another approach is the stimulation of brain repair by endogenous stem cells via external manipulation. In this review, recent advances in stem cell research in PD will be discussed, giving an overview of the various strategies including the use of different stem cell populations for cell replacement and the possible modulation of endogenous stem cells that have the potential to provide effective cell-based therapy in future.