Embryonic stem cells have been shown to restore movement after paralysis. And with genetic engineering, stem cells can act as sophisticated protein delivery systems. Scientists have used them to deliver GDNF, a factor to aid in the survival of neurons targeted by Parkinson's and Huntington's diseases. Another team has used them to seek and destroy brain tumor cells. And a Norwegian group has proved that even in adults, neural stem cells have the power to become functioning neurons.
Scientists at the University of California , Irvine , have reversed spinal cord damage in paralyzed adult rats, allowing them to walk again. The researchers, led by Hans Keirstead, PhD, used human embryonic stem cells, which have the potential to become any cell type in the entire body--and turned them into oligodendrocytes--a type of cell in the brain. Oligodendrocytes form the fatty substance myelin that insulates the long wirelike extensions of nerve cells, called axons. Oligodendrocytes wrap themselves around these axons, allowing electrical signals to be rapidly transmitted to other cells in the brain and body.
Spinal cord injury results in a cut through the axons, breaking the information circuit and resulting in paralysis. Even if the neurons are able to regrow new axons, they require oligodendrocytes to form new myelin. "By transplanting new oligodendrocytes, we repaired the lost insulation," Keirstead says.
The researchers manipulated human embryonic stem cells to become oligodendrocyte progenitor cells (OPCs), an intermediate step before becoming oligodendrocytes. Once implanted to the nervous system of rats, the cells completed their maturation.