Scientists have performed the first successful neural stem cell transplant into the brains of four boys with Pelizaeus-Merzbacher disease. The disorder is a rare but tragic condition that impacts motor abilities, coordination and cognitive function.
Pelizaeus-Merzbacher disease does its damage by stripping away the fatty substance called myelin that surrounds brain cells. Myelin acts as an insulator, like rubber on the outside of a wire, helping the electrical impulses that carry information in the brain travel at high speeds.
Now, in two new studies, both published this week in the journal Science Translational Medicine, researchers have shown that neural stem cells — cells that can turn into any type of brain cell — can be successfully implanted into the brain. More important, they showed that these brain cells often turn into a brain cell type called an oligodendrocyte — the type of cell that produces myelin.
They also demonstrated in both studies that the addition of the oligodendrocytes appears to improve the function of cells in the brain by adding new myelin.
In the first study, a group of researchers centered at Oregon Health & Sciences University implanted human neural stem cells into mice that had been genetically altered to have less myelin than normal. The scientists followed the mice as the cells changed from stem cells into brain cells and found that the majority of those cells turned into oligodendrocytes. Further, as the cells developed, the brain began to work better, integrating the new myelin into existing cells and improving the speed of information flow as a result.
But mice are one thing; showing it works in humans is another. In the second report, researchers from UC San Francisco implanted the same types of cells into four boys that had Pelizaeus-Merzbacher disease. Using brain imaging techniques, they were able to detect increased amounts of myelin in the boys’ brains. More important, three of the four boys showed small but real improvements in motor function.
While the treatment seems promising, the study was a small proof of a concept project, and there was no control group. That means another, larger study will have to be conducted before we know for sure that the approach actually helps people who have diseases that remove myelin.
But the study is an important first step: It appears to show that the approach is safe, as none of the boys have developed serious complications as a result of the therapy.
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