Third, it's not clear which steps in the procedure were key to the success, nor whether another growth factor would be better. 
Amidst the gathering enthusiasm about spinal cord repair, some cautions are in order. For example, although the Karolinska Institute researchers were able to persuade rat spinal cord to bridge a gap, Wise Young of New York University notes they started with a clean cut across the spinal cord. In real life, most spinal-cord injuries occur in a crushing accident, and doctors are going to be quite reluctant to sever the remaining cord before a bridging operation. Thus it's not clear whether the procedure will transfer to people with real-world injuries.
Second, while the rats did regain some motor nerve function, Young says they were "barely able to stand."
Third, it's not clear which steps in the procedure were key to the success, nor whether another growth factor would be better.
On the bright side, incomplete repairs still represent a worthwhile goal, since "remarkably few spinal axons are required to recover some motor function," Young says. People with fewer than 10 percent of their original number of axons can walk quite well, he adds.
Finally, after years of discouragement, spinal cord repair is on the horizon. Instead of requiring another breakthrough, what is most needed is some time, some money and lots of effort. Already, science has brought better methods for protecting neurons from destruction, better healing techniques for damaged neurons and, for the first time, ways to grow neurons toward their targets.
Overall, says Young, the "possibility of effective regenerative therapies for human spinal cord injury is no longer a speculation but a realistic goal."
When Christopher Reeve asked how long he'd have to wait for a regenerative operation, Young offered a rough guess of seven years. The pressure is on the researchers to transfer their ideas from the lab to the clinic, he adds. "Nobody knows how long it will take, but I'm absolutely convinced we will achieve regeneration in the spinal cord."
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