Paralysed mice walk after stem cell injections

US scientists have used nerve stem cells to treat mice affected by severe spinal cord injuries. The team, based at the University of California at Irvine, said the treated animals regained the ability to walk just a few weeks after receiving the injections. The findings, published in the Proceedings of the National Academy of Sciences, add to growing evidence that stem cells from a variety of sources could lead to new therapies for spinal cord injuries and diseases.

The researchers used nerve stem cells obtained from 16-18 week-old aborted human fetuses. They injected mice with around 75,000 of these cells, at four sites surrounding the injury. After nine days, the treated animals were more mobile, and a few weeks later they could walk again. Microscope analysis revealed that the injected cells had turned into both neurons (nerve cells), and also new oligodendrocytes - cells that produce the protective substance myelin, which protects and insulates nerve cells.

Study author Brian Cummings said the team were 'excited to find that the cells responded to the damage by making appropriate new cells that could assist in repair', adding 'this study supports the possibility that formation of new neurons may contribute to recovery'. To check whether the cell injections really were linked to the improvement of the mice, the scientists gave some of the recovering animals a toxin that kills human cells. The walking ability of the mice given the toxin regressed again, whilst those spared the treatment continued to improve.

The company that supplied the cells used in the study, StemCells Inc, is one of three US firms who say they are close to testing human neural stem cells as therapies, according to a report in the Washington Post. Earlier this year, another team at the University of California at Irvine successfully treated rats with spinal cord injuries, using cells derived from human embryonic stem cells (ES cells) by Geron. And unpublished research shows that human fetal spinal cord cells developed by NeuralStem Inc can also help repair spinal cord damage in rats. All three companies hope to obtain permission from the US Food and Drug Administration to begin testing their cells in humans, perhaps as early as next year.