Groundbreaking rat experiment offers new hope for paralyzed humans

Swiss scientists have conducted an experiment in which paraplegic rats have re-learned to walk, run, and evade obstacles. The spectacular results followed a physical training regimen that included electrical and chemical stimulation of the rats' damaged spinal columns and the use of a "robotic postural interface". The study, published June 1 in Science, could have profound implications for paralyzed humans suffering from similar spinal cord injuries.

To conduct the study, the research team, led by Grégoire Courtine of the Federal Institute of Technology in Lausanne, took ten rats and severed all the direct nerve connections to their hind legs, stopping short of severing the spinal cord. By doing so, the rats became paraplegics, but were able to retain use of their front legs.

The scientists then worked to "re-awaken" the rats' spinal brain by injecting them with a solution of cell binding chemicals - a concoction of neurotransmitters consisting of serotonin, dopamine and norepinephrine. The chemical solution subsequently triggered cell responses by binding the chemicals to receptors on the spinal neurons.

Following this stage, the rats were put on a daily regimen in which they were outfitted with the robotic postural interface, a tiny vest that made them stand upright on their hind legs, forcing them to bear their own weight. The rats were enticed to move forward by pieces of cheese and chocolate (both Swiss, of course) that were placed just outside of their reach. It was through this regular exercise, plus the electrical stimulation and chemical treatments, that the scientists were able to facilitate growth.

During the rehabilitation sessions, the researchers applied electric stimulation to re-activate the previously useless limbs, helping the rats move their legs again - albeit involuntarily. But it didn't take long for the rats to regain voluntary control. All it took was three weeks of 30-minute daily sessions to help them make their first steps. And after six weeks, all of the rats could walk independently. Some could even run and climb stairs.

It was through this regular routine that the rats were able to re-establish the connections to their limbs to help them bypass the injured spinal cord and activate their hind limbs voluntarily. Consequently, the observation that a stimulated spinal column can still function despite being physically isolated from the brain is a rather profound discovery.

The success of the experiment has reinforced the suggestion that human paraplegics can be rehabilitated in this way. It's been known for some time that stimulation and training can improve muscle control after similar injuries to both humans and animals.

It's important to note that the Swiss study does not apply to all spinal injuries. The rats' spinal columns were cut without being completely severed, meaning that there were still some nerve connections that extended through the injured area. That said, this kind of injury accounts for a sizeable proportion of human paraplegics, as many as 25-35%.

The Swiss scientists hope to start human trials within two years.

Top image via École Polytechnique Fédérale de Lausanne. Via NYT, LAT, and Reuters.