专八考试：阅读理解之健康类（2）

Seven years ago I stood on a bridge over the M40 doing a “piece to camera” for a report about spinal repair. The aim was to come up with a metaphor for how researchers at University College London were trying to overcome spinal cord paralysis.

It went something like this: “Imagine your spinal cord as a motorway, the cars travelling up and down are the nerve fi bres carrying messages from your brain to all parts of the body. If this gets damaged the cars can’t travel. The messages are blocked, the patient is paralysed.

Normally there is no way of repairing a severed spinal cord. But the team at UCL took nasal stem cells, and implanted them into the area of damage. These formed a bridge, along which the nerve fibres re-grew and re-connected.

The research at the Spinal Repair Unit at UCL involved rats, not humans. In my TV report we showed rats unable to climb a metal ladder after one of their front paws had been paralysed to mimic a spinal cord injury. But after an injection of stem cells, the rats were able to move nearly as well as uninjured animals.

The hope then—and now—is that such animal experiments will translate into similar break-throughs with patients. Seven years on and the team at UCL led by Professor Geoff Raisman are still working on translating this into a proven therapy for patients. He told me “this is difficult and complex work and we want to ensure we get things right.” So it was with a sense of caution that I approached some Swiss research in the latest edition of the journal Science in which paralysed rats were able to walk again after a combination of electrical-chemical stimulation and rehabilitation training.

The research prompted some newspaper reports talking of “new hope” for paralysed patients. The lead researcher, Professor Gregoire Courtine enthused: “This is the World-Cup of neuro-reha- bilitation. Our rats have become athletes when just weeks before they were completely paralysed.”

A brief summary of the research is this: the team at the Federal Institute of Technology (FIT) in Lausanne injected chemicals into the paralysed rats aimed at stimulating neurons that control lower body movement. Shortly after the injection their spinal cords were stimulated with electrodes.

The rats were placed in a harness on a treadmill which gave them the impression of having a working spinal column and they were encouraged to walk towards the end of a platform where a chocolate reward was waiting. Over time the animals learned to walk and even run again.

The major question is this: What does this mean for humans who are paralysed?

Prof. Courtine said he was optimistic patient trials would begin in “a year or two” at Balgrist University Hospital Spinal Cord Injury Centre in Zurich. Other scientists gave a mixed response to the findings. Dr Elizabeth Bradbury, Medical Research Council Senior Fellow, King’s College London, described the Swiss experiments as “elegant” and “ground-breaking”. But she said questions remained before its usefulness in humans could be determined.

She said: “Firstly, will this approach work in contusion/compression type injuries? These injuries involve blunt trauma, bruising and compression of the spinal cord and are the most common form of human spinal cord injury. Very few human spinal cord injuries occur as a result of a direct cut through spinal tissue (as was the injury model in the Courtine study).

“Secondly, will this technique work in chronic (long-term) spinal injuries? It is not yet known whether it is possible to generate extensive neuroplasticity in a system that has been injured for a long time and now contains many more complications such as abundant scar tissue, large holes in the spinal cord and where many spinal nerve cells and long range nerve fi bres have died or degenerated.”

That term “neuroplasticity” is crucial. It refers to the ability of the brain and spinal cord to adapt and recover from moderate injury—something which researchers have been trying to exploit for years.