Restoring Eyesight to the Blind

Since neurons don't regenerate, brain damage is often permanent—but scientists would like to change that.

By Jessica Ruvinsky|Sunday, June 25, 2006
RELATED TAGS: BIOTECHNOLOGY, SENSES

THE STUDY

  "Nano Neuro Knitting: Peptide Nanofiber Scaffold for Brain Repair and Axon Regeneration With Functional Return of Vision," published in Proceedings of the National Academy of Sciences. The authors made blind hamsters see again.

THE PROBLEM

 Every year, 235,000 Americans are hospitalized for traumatic brain injuries, and 550,000 survive severe strokes. Since neurons don't regenerate, the damage is often permanent. Rutledge Ellis-Behnke, a neuroscientist at MIT, would like to change that by finding a way to repair brains.

THE FINDINGS

Before they could restore vision, Ellis-Behnke and his colleagues had to start by taking it away. They performed brain surgery on 16 hamster pups, anesthetizing the rodents and severing the optic tract on one side of the brain. Then the researchers set out to undo the damage they had inflicted.

The MIT team developed a neuron-healing mixture they call self-assembling peptide nanofiber scaffold solution—or in simpler terms, a solution that contains peptides (molecules related to proteins) shaped like miniature combs. Each comb is 0.0000002 of an inch long with four teeth, each one-fourth as large. When injected into the animals' brains, the solution flows into the gaps around the injury. Then the molecular combs line up and bridge the gaps between the severed neurons, forming scaffolds that allow the cells to flourish.

10 of the hamsters got a 0.003-ounce injection of the solution. "We didn't know if it would kill the animals or not," Ellis-Behnke says. The remaining 6 pups got a saline solution injection.

24 hours, 72 hours, 30 days, and 60 days later, the researchers killed the hamsters a few at a time and looked at their brain tissue under a microscope. In the 6 hamsters treated with saline solution, there was still a gaping hole in the optic tract. In the 10 hamsters treated with the peptide solution, the wound healed.

The real test is whether the treatment truly restored the hamsters' vision. "How do you ask a hamster if it can see?" Ellis-Behnke asks. His answer: Dangle a sunflower seed within its peripheral vision. If it turns, the severed neurons must once again be talking to the whole brain. The team tested adult hamsters that had undergone the same procedure as the pups.

75 percent of them consistently turned toward the seed; their vision had returned. None from the control group did so. Human trials might be a decade away.

THE RESEARCHERS

 Rutledge Ellis-Behnke pictures neurons as plants growing on trellises, which is not surprising since he grew up working in his parents' nursery. Now he travels back and forth between MIT and Hong Kong, where he teaches neuroanatomy. "It's not bad," he says. "It's 15 hours, like a long day at the office, but somebody brings you coffee and you don't have to get up." His 6 coauthors come from both continents. Shuguang Zhang of MIT, who also invented a solar cell based on spinach, developed the nanofiber scaffold solution in 1990. His scaffolds have since been used to grow cartilage and to repair the heart of a mouse. What else is in store? "You never know!" Zhang says.

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