Washington ? Injections of human stem cells seem to directly repair some of the damage caused by spinal cord injury, according to research that helped partially paralyzed mice walk again.

The experiment, reported Monday, isn’t the first to show that stem cells offer tantalizing hope for spinal cord injury – other scientists have helped mice recover, too.

But the new work went an extra step, suggesting the connections that the stem cells form to help bridge the damaged spinal cord are key to recovery.

Surprisingly, they didn’t just form new nerve cells. They also formed cells that create the biological insulation that nerve fibers need to communicate. A number of neurological diseases, such as multiple sclerosis, involve loss of that insulation, called myelin.

The research is reported in Monday’s issue of Proceedings of the National Academy of Sciences.

The researchers injured the spinal cords of mice and nine days later injected some with the human neural stem cells.

Four months later, the treated mice could again step normally with their hind paws. Mice given no treatment or an injection with an unrelated cell showed no improvement.

The research was funded by the nonprofit Christopher Reeve Foundation and the National Institutes of Health. StemCells Inc. of Palo Alto, Calif., provided the fetal-derived stem cells.