Cell Therapy for Parkinson’s Disease ☆

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases. Current therapeutic approaches for PD provide temporary symptomatic relief, but none change the course of the disease. Pharmacological therapies are valuable but are not long lasting, and surgical treatment is actually no better than current medications. Transplantation of embryonic mesencephalic cells, based on an open-label pilot study, has encouraged cell therapy as an alternative treatment for PD. However, two recent double-blind placebo-controlled transplantation trials did not confirm the therapeutic effect observed in the open-label study and thus raised concerns about the feasibility of treatment using transplantation of fetal brain-derived mesencephalic cells. Similar results also occurred when retinal pigment epithelial (RPE) cells were used to treat PD patients. Recent advances in producing dopaminergic (DA) neurons from human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs) have inspired our hope for an alternative cell source for treating PD. Yet, there are noticeable challenges and concerns, including production of genetically stable DA neurons, overcoming host immune rejection, prevention of tumor formation in the graft, and integration of grafted DA neurons into host circuits. This article provides an overview of selective cell sources and cell differentiation stages in treating PD patients.