A study by University of California ( UC ) Irvine researchers found that transplanting human embryonic stem cells does not cause harm and can be used as a therapeutic strategy for the treatment of acute spinal cord injury.

Hans Keirstead at UC Irvine and colleagues at the Reeve-Irvine Research Center found that rats with either mild or severe spinal cord injuries that were transplanted with a treatment derived from human embryonic stem cells suffered no visible injury or ill effects as a result of the treatment itself. Furthermore, the study confirmed previous findings by Keirstead's lab -- since replicated by four other laboratories around the world -- that replacing a cell type lost after injury improves the outcome after spinal cord injury in rodents.

The findings are published in the journal Regenerative Medicine.

In 2005, Keirstead's lab was the first to coax human embryonic stem cells to become highly pure specialized cells known as oligodendrocytes. These cells are the building blocks of myelin, which acts as insulation for nerve fibers and is critical for maintenance of electrical conduction in the central nervous system. When myelin is stripped away through disease or injury, paralysis can occur.

In this study, as in the original one, when the rats suffering from severe spinal cord injury were injected with the oligodendrocytes seven days after injury, the cells migrated to the appropriate sites within the spinal cord and wrapped around the damaged neurons, forming new myelin tissue.

By contrast, the rats who were only mildly impaired showed no increase or decrease in myelin generation, and no change in their walking ability after transplantation. According to Keirstead, the injury was so minor that no loss of myelin occurred. Therefore, a treatment based on remyelination would have no effect and the animals recovered motor function on their own. More importantly, while the treatment did not help with functional recovery, it also did not impair it. Upon further examination, the scientists found no damage to the tissues surrounding the spinal cord indicating that the transplantation had not caused any damage to the animals.

" Our biggest safety concern was that in the case of a severe injury, any harm the stem cell-derived treatment could cause would be masked by the injury itself, " Keirstead said. " In this study, we can see in animals that are only slightly injured that the transplantation does not cause visible harm and the injury is not hiding any damage the cells may have caused to the spinal cord or the surrounding tissue."

Source: University of California – Irvine, 2006


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