Scientists have successfully implanted human neural stem cells into the brains of children with a rare neurological disorder, called Pelizaeus-Merzbacher disease (PMD). People with PMD have severe deficits in speech and movement, and often do not survive to adolescence. PMD is an inherited condition, which leads to the loss of myelin, a fatty insulating substance that wraps around nerve cells to allow proper electrical signalling in the brain.
Researchers found that upon transplantation the stem cells developed into the main myelin-producing cells of the brain, called oligodendrocytes. 'For the first time, we have evidence that transplanted neural stem cells are able to produce new myelin in patients with a severe myelination disease', said Dr Nalin Gupta, lead author and associate professor of neurological surgery at the University of California, San Francisco (UCSF).
The phase I clinical trial was performed on the infants primarily to test safety, following promising findings in a mouse model of the disease. The neural stem cells, derived from donated fetal brain tissue by the biotechnology company Stem Cells, Inc, were surgically implanted into the brains of four boys with early-onset PMD.
One of the major concerns was whether or not the children would reject the cells, as the treatment did not use their own stem cells. Drugs were therefore used to suppress the children's immune systems and one year on the cells were still surviving. Neurological examinations were used to check the progress of the patients and magnetic resonance imaging (MRI) was used to detect the production of myelin.
'Without such studies in human patients, we won't really know how transplanted cells behave – whether they disperse or migrate, whether they engraft or degenerate and die, whether immune-suppressing regimens really work or not', said Dr Arnold Kriegstein, from the UCSF School of Medicine, who was not involved in the study.
The use of stem cells to effectively replace lost or dying cells has been a long sought-after goal in the treatment of a wide variety of brain disorders, including Alzheimer's disease, multiple sclerosis and stroke.
Dr Kriegstein remarked: 'It's only through these investigations that we will be able to refine the necessary procedures and technologies and make progress toward cell-based therapies for this disease and related disorders'.
The findings were published in the journal Science Translational Medicine.