Embryo stem cells help treat paralysed rats

US scientists have successfully treated rats with spinal cord injuries, using cells derived from human embryonic stem cells (ES cell). The team, based at the Reeve-Irvine Research Center at the University of California, Irvine, reports that the cells restored movement in rats treated seven days after the initial injury, but did not work on rats that had been injured for ten months. The researchers say that their findings, published in the Journal of Neuroscience, offer hope for treating patients during the very early stages of spinal cord injury.

Many researchers think that ES cells, which have the potential to grow into almost any type of cell, hold great promise for treating a range of serious medical conditions. The Irvine team, who presented preliminary results from the study at a conference two years ago, used ES cells to grow specialised 'nerve insulating' cells, called oligodendrocytes. These cells form myelin, the substance that covers and insulates nerve cell fibres, in the same way that plastic insulates electrical wires. If nerve cells lose their myelin covering through disease or injury, then the patient can lose sensory or movement ability, leading to paralysis if the spinal cord is severely affected.

The scientists injected the human ES cell-derived oligodendroctyes into rats that had experienced a partial spinal cord injury, which meant they could no longer walk properly. They treated one group seven days after the injury, and another group ten months after the damage had been sustained. In the rats treated after seven days, myelin formed around the damaged nerve cells in the spinal cord, and within two months the animals showed 'significant improvements' in walking ability, compared to untreated rats. However, there was no such improvement in the rats treated after ten months, because although the transplanted cells survived, myelin could not form due to the scar tissue that had grown around the damaged nerves.

Team leader Hans Keirstead says the group are 'very excited' with the results, which highlight the importance of myelin loss in spinal cord injury. 'This study suggests one approach to treating people who've just suffered spinal cord injury, although there is still much work to do before we can engage in human clinical tests', he said. It is thought that stem cell treatments in humans could be given during the first few weeks following injury, when rods and ties are placed in the spinal column to stabilise it.