Stem cell grafting in parkinsonism--why, how and when.

Parkinson's disease is a devastating, progressive neurodegenerative disorder that affects the central and peripheral nervous systems. Although recent advancements have led to a better understanding of the disorder, there is currently no long-term disease-modifying strategy. Recently, preclinical data have identified the significant effects of pluripotent stem cell grafting in 6-OHDA and MPTP animal models of motor parkinsonism; there have also been some clinical data in patients with motor parkinsonism. Pluripotent stem cells can nestle in affected organs and can differentiate into a variety of cells, including neural (dopamine producing) cells. Depending on the environment into which they are grafted, these stem cells can also influence immune responses by regulating the activity of B-cells, T-cells, and NK-cells. Pluripotent stem cells can also produce chemotrophins, including BDNF (brain-derived neurotrophic factor), GDNF (glial-derived neurotrophic factor), NGF (nerve growth factor), TGF-β (transforming growth factor-β), IGF-1 (insulin-like growth factor 1), NT-3 (neurotrophin 3), and SCF-1 (stem cell factor 1). Influencing these trophic factors can influence plasticity. This article explores the potential of pluripotent stem cells in the treatment of PD. We will explore the utilization of pluripotent stem cells in the immunomodulation of B-cells, T-cells and NK-cells, the transdifferentiation of pluripotent stems cells into DA-cells, and the secretion of trophic factors and its relation to plasticity. We will also cover how best to conduct a clinical trial, which stem cells can be safely used in patients, what are the methods of induction before application, and how to re-apply stem cells in patients by intravasal, intrathecal or intracerebral methods. Finally, we will describe how to objectively record the clinical results.