A team of neuroscientists at the Massachusetts Institute of Technology and their colleagues at Hong Kong University purposefully wounded 53 newly born hamster pups. They cut a relatively deep gash--1.5 millimeters deep and two millimeters wide--through the optic tract in the brains of the young rodents. The wounds of 10 of the pups were then treated with 10 microliters of a solution composed of 99 percent water and 1 percent of a special ionic peptide. These short amino acids are capable of creating a molecular scaffold that can bridge such gaps.
Within 24 hours, the gash in the treated pups had begun to close (shown by the green area in the picture above, depicting regrowth), and by 30 days had completely closed. "We had never seen that before in any animals," says neuroscientist Rutledge Ellis-Behnke of M.I.T., who led the research. By placing a biological tracer in the hamsters' eyes the researchers also discovered that the neurons had actually grown back and reconnected through the center of the cut instead of routing around the wound--another first. None of the control animals showed any healing whatsoever.
The scientists then inflicted a similar wound on some adult hamsters to see if such connections could actually regenerate vision. By injecting 30 microliters of the solution, the scientists again healed the gaps in 30 days. And in subsequent behavioral tests, the animals had regained the ability to turn their eyes and heads toward a sunflower seed in their peripheral vision, though their turning response was slower than normal.
The solution, which forms a tight-fitting fibrous gel in the wound, appears to have no long-term side effects, breaking down into its constituent amino acids and exiting the body through the bloodstream and urine. "We have healing of the brain, which we've never seen before. We have axons growing through the center of the cut, which we've never seen before, and we have axons connecting to the target tissue," Rutledge notes. "If we could use something like this to mitigate the damage caused by cutting the brain with a knife, that would be great." The research appears online this week in Proceedings of the National Academy of Sciences.