An Irish scientist has discovered yet another element in how the body grows nerve cells, bringing a step closer the day when spinal cord injuries might be repaired. The work, published in the current issue of the science journal, Nature, involves the study of a pancreatic protein, Reg-2, found in the embryo during foetal development but also when motor neurons, the nerves connecting the brain to muscles, are damaged. These are the only type of human nerve cells able to grow again after injury. They in turn grow only when stimulated by the growth and release of substances from cells which surround the neurons, Schwann cells. This regeneration process can be disrupted, as in motor neuron disease where the cells die but do not re-grow. The actor David Niven died of motor neuron disease and it has disabled the eminent scientist, Stephen Hawking.
Reg-2 had been known for years but how it did its work in rebuilding damaged nerves has not been clearly understood. But Cork-born Dr Rick Livesey, who completed his work while at Cambridge University in association with Prof Stephen Hunt and Mr John O'Brien, has found that the Reg-2 stimulates the growth of the Schwann cells. Dr Livesey is now based at Trinity College.
"The idea was to try to understand the mechanism behind Reg-2," Dr Livesey explained. "What we found was that when we injured motor neurons and Reg-2 was released, the Schwann cells around them started to proliferate. The Reg-2 signal is a signal for the Schwanns to grow and divide. It is an essential component for the growth of motor neurons."
Reg-2 is one of a family of five similar proteins discovered so far that have a role in foetal brain development and nerve cell growth. They are present in the foetus but their production ceases thereafter, unless nerve damage occurs. A Reg protein has been found to reappear again in patients suffering from Alzheimer's disease.
"One of the things we are pursuing is to try to see if the production of this protein could be used as a marker for motor neuron diseases," Dr Livesey said. Peripheral motor neurons are now increasingly applied as grafted tissues, used in an attempt to repair other types of nerve cells, and Reg-2 could be used to stimulate their growth.
"The clinical consequences are still miles away," Dr Livesey said.
