Human embryonic stem cell therapies for neurodegenerative diseases
There is a renewed enthusiasm for the clinical translation of human embryonic stem (hES) cells. This is abetted by putative clinically-compliant strategies for hES cell maintenance and directed differentiation, greater understanding of and accessibility to cells through formal cell registries and centralized cell banking for distribution, the revised US government policy on funding hES cell research, and paradoxically the discovery of induced pluripotent stem (iPS) cells. Additionally, as we consider the constraints (practical and fiscal) of delivering cell therapies for global healthcare, the more efficient and economical application of allogeneic vs autologous treatments will bolster the clinical entry of hES cell derivatives. Neurodegenerative disorders such as Parkinson's disease are primary candidates for hES cell therapy, although there are significant hurdles to be overcome. The present review considers key advances and challenges to translating hES cells into novel therapies for neurodegenerative diseases, with special consideration given to Parkinson's disease and Alzheimer's disease. Importantly, despite the focus on degenerative brain disorders and hES cells, many of the issues canvassed by this review are relevant to systemic application of hES cells and other pluripotent stem cells such as iPS cells.