Regenerative medicine for the brain that enables periodic repair in situ is essential to the future of human longevity. This is the only tissue in the body that cannot be outright replaced as a last resort, as its structure defines the data of the mind. Scientists are making some progress towards this goal, applying the tools developed in stem cell research in an increasingly refined way:
Researchers have taken an important step in the area of cell therapy: repairing the cerebral cortex of the adult mouse using a graft of cortical neurons derived from embryonic stem cells. The cerebral cortex is one of the most complex structures in our brain. It is composed of about a hundred types of neurons organised into 6 layers and numerous distinct neuroanatomical and functional areas. Brain injuries, whether caused by trauma or neurodegeneration, lead to cell death accompanied by considerable functional impairment. In order to overcome the limited ability of the neurons of the adult nervous system to regenerate spontaneously, cell replacement strategies employing embryonic tissue transplantation show attractive potential.
A major challenge in repairing the brain is obtaining cortical neurons from the appropriate layer and area in order to restore the damaged cortical pathways in a specific manner. The results show, for the first time, using mice, that pluripotent stem cells differentiated into cortical neurons make it possible to reestablish damaged adult cortical circuits, both neuroanatomically and functionally. These results also suggest that damaged circuits can be restored only by using neurons of the same type as the damaged area. This study constitutes an important step in the development of cell therapy as applied to the cerebral cortex.
Much research will be needed before there is any clinical application in humans. Nonetheless, for the researchers, "The success of our cell engineering experiments, which make it possible to produce nerve cells in a controlled and unlimited manner, and to transplant them, is a world first. These studies open up new approaches for repairing the damaged brain, particularly following stroke or brain trauma."