Can We Use Human Embryonic Stem Cells to Treat Brain and Spinal Cord Injury and Disease?

The potential use of human embryonic stem cells for the treatment of neurological disease and injury is discussed from the perspectives of two common disease scenarios. Spinal cord injury and diseases such as multiple sclerosis that affect specific cell types in the spinal cord represent a substantial proportion of all neuropathologies and are among the most heavily targeted by efforts to establish stem cell-based replacement therapies. Parkinson’s disease selectively destroys a single type of neuron in a restricted region of the brain. For this reason it was the first neurological disease for which cell replacement therapy was attempted in humans and is considered one of the most amenable to treatment using stem cells. Although the replacement of a single cell type or the repair of a restricted lesion would appear to be relatively straightforward, several issues conspire to make stem cell-based replacement therapy in the brain and spinal cord substantially more challenging. These include the inherent complexity of neural circuits, the problems of ensuring the survival of stem cells and their derivatives after implantation and directing their differentiation into the appropriate cell types, and the increased refractoriness of chronic injury to treatment due to changes in the cellular environment. A layman’s guide to the composition of brain and spinal cord tissue is provided, and an update of recent advances in basic neuroscience and stem cell research with relevance to these issues is presented.