Adult human neural stem cells have successfully regenerated damaged spinal cord tissue and improved mobility in paralyzed mice, US scientists reported on Monday.

The findings, posted on the on-line Proceedings of the National Academy of Sciences, point to the promise of using stem cells to cure humans who have spinal cord injuries, said the researchers at the University of California, Irvine.

The researchers found that adult human neural stem cells differentiated into new oligodendrocyte cells that restored myelin around damaged mouse axons after being injected into mice with spinal cord injuries.

Meanwhile, transplanted cells differentiated into new neurons that formed synaptic connections with mouse neurons.

"This work is a promising first step, and supports the need to study multiple stem cell types for the possibility of treating of human neurological injury and disease," said Aileen Anderson, lead investigator of the study.

Myelin is the biological insulation for nerve fibers that is critical for maintenance of electrical conduction in the central nervous system. When myelin is stripped away through disease or injury, sensory and motor deficiencies result and, in some cases, paralysis can occur.

Previous research has shown that transplantation of oligodendrocyte precursors derived from human embryonic stem cells restores mobility in rats.

"We set out to find whether these cells would be able to respond to the injury in an appropriate and beneficial way on their own," said Brian Cummings, first author of the paper.

"We were excited to find that the cells responded to the damage by making appropriate new cells that could assist in repair. This study supports the possibility that formation of new myelin and new neurons may contribute to recovery."

Mice that received human neural stem cells nine days after spinal cord injury showed improvements in walking ability compared to those that received either no cells or a control transplant of human fibroblast cells, which cannot differentiate into nervous system cells.

Further experiments showed behavioral improvements after either moderate or more severe injuries, with the treated mice being able to step using the hind paws and coordinate stepping between paws whereas control mice were uncoordinated, said the researchers.

The cells survived and improved walking ability for at least four months after transplantation. Sixteen weeks after transplantation, the researchers killed the engrafted human cells with diphtheria toxin. This procedure abolished the improvements in walking, suggesting that the human neural stem cells were the vital catalysts for the maintained mobility.

Although additional studies will be necessary to evaluate therapeutic potential, the results suggest that human neural stem cells derived from fetal tissue and expanded into cell banks could have benefits for treating injuries of the central nervous system such as spinal cord injury, according to the researchers.

Source: Xinhua