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A little bit of science: New Advances In Nerve Regeneration By AYALA OCHERT c.1996 Nature News Service Hope that spinal injuries might be repaired, restoring movement to those with paralysis, is no longer misplaced. The latest result in a long line of recent promising experiments in nerve regeneration might also benefit victims of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. After an injury many nerves are able to repair themselves, but the nerve cells of the brain and spinal cord, which are vital to our every movement and sensation, are tragically incapable of regenerating. The only exception occurs in the brain of a developing fetus, or so it was thought. Dr. Fred H. Gage and colleagues from the Salk Institute in La Jolla, Calif., have been examining certain cells, in defined areas of the brain, which, like nerve cells in the fetal brain, can actually grow and mature into fully functioning brain cells. Until now, much research into brain or spinal regrowth has made use of fetal nerve tissue, but Gage's team was interested in probing the full potential of the adult central nervous system (brain and spinal cord). As the researchers report in the Oct. 17 issue of Nature, they concentrated their efforts on two areas of the brain that are `proliferative zones.'' Nerves in these areas can develop from immature progenitors into fully fledged brain cells suited to their specific purpose. In laboratory cultures, cells from these zones can be persuaded to grow into mature cells, but what might they get up to actually inside the brain? The researchers took cells from one such zone and grafted them into a different proliferative zone. They also grafted the cells into an area of the brain where nerve cells don't normally grow and mature. Immature nerve cells from an area normally associated with memory, when grafted into an area responsible for our sense of smell, actually grew into fully mature smell-sensing nerves. But when grafted onto an area where cells don't normally continue to grow in adulthood, they didn't grow and mature. This research shows that patches of undifferentiated nerve cells that survive in this pristine state until adulthood can be persuaded to differentiate into nerve cells characteristic of the surroundings in which they find themselves, provided that those surroundings are conducive to such development. While these experiments don't immediately suggest a therapy for diseases such as Alzheimer's and Parkinson's, in which parts of the brain degenerate, they do offer hope. One controversial treatment for Parkinson's disease had involved brain cells from human fetuses, but this raised concern over the ethics of using such tissue. Indeed, many countries now ban experimentation with human fetuses, or put a limit on the age of fetuses that can be experimented with. The knowledge that some adult brain cells are capable of growing in parts of the brain might reduce the reliance on fetal cells and the chances of the brain rejecting these grafts. These findings are just the latest in recent years that are overturning conventional wisdom about what we can dare to hope for in future treatments for those with brain and spinal injuries and neurodegenerative diseases. This summer, in a remarkable experiment reported in the journal Science, Dr. Henrich Cheng and colleagues got the spinal cord of rats to grow across a clean break, restoring their ability to stand, and proving that cells of the central nervous system do have the potential to regenerate. Other treatments for spinal-cord injuries involve medicines that rejuvenate damaged nerve cells, those that reduce further damage, and those that maximize the functioning of partially damaged nerves. Yet other treatments attempt to restore function using ``neural prostheses'' - miniaturized computers, sensors and electrodes that can replace parts of a damaged nervous system. Just a decade ago there was deep pessimism among researchers in this field. But these developments, including this latest research, now make it realistic to expect regeneration of an injured human spinal cord in the next ten years. (Distributed by New York Times Special Features) NYT-10-16-96 1045EDT< Margaret Tuchman(54yrs,dx1980) [log in to unmask] *******************************************************************