Regrow Your Own

Many species, notably amphibians and certain fish, can regenerate a wide variety of their body parts.

The salamander can regenerate its limbs, its tail, its upper and lower jaws, the lens and the retina of its eye, and its intestine. …

Mammals, too, can renew damaged parts of their body. …

In many of these cases, regeneration begins when the mature cells at the site of a wound start to revert to an immature state. The clump of immature cells, known as a blastema, then regrows the missing part, perhaps by tapping into the embryogenesis program that first formed the animal.

Initiation of a blastema and the formation of the embryo are obviously separate biological programs, but "the processes must converge at some point," says Professor Jeremy Brockes [UCL Biochemistry & Molecular Biology], a leading regeneration researcher. …

The capacity for regeneration exists in such a wide variety of species that it is unlikely to have evolved independently in each, regeneration researchers believe.

Rather, they say, the machinery for regeneration must be a basic part of animal genetic equipment, but the genes have for some reason fallen into disuse in many species. …

The genetics of regenerating animals, like the salamander, are largely unknown. Hence the process of regeneration has received little attention from research biologists. But there is a group of vertebrates that can regenerate very successfully, said Professor Brockes. "It would be rather surprising if there weren't some interesting and important lessons one could learn from them." …

Many proponents of regeneration, while conceding they have a great deal more to learn, believe stem cell therapy too may not be as close to clinical use as its advocates sometimes suggest. Professor Brockes noted that the blastema's reliance on internal information contrasts with a principal assumption of stem cell therapy, that stem cells inserted into a damaged tissue will use local cues to behave appropriately and integrate into the surrounding tissue.

Stem cell therapists assume that injected cells can replace missing tissue with guidance from the invisible template supplied by chemical signals from nearby cells. That is the solution a human engineer might logically think of, Professor Brockes said, but evolution has chosen a different one.

Nicholas Wade, 'New York Times'