Scientists are a step closer to the secret of body part regeneration

A tiny fish has taken scientists a step closer to unlocking the secrets of body part regeneration, a power possessed by some animals but not humans.

The ability to "grow back" a perfectly formed duplicate organ or limb to replace one lost through injury or disease is the 'Holy Grail' of regenerative medicine.

Some animals perform this miraculous feat effortlessly. Earthworms, crayfish and tadpoles are examples. A crayfish that loses a leg simply grows a new one.

The tiny flatworm Planaria can be cut into as many as 32 pieces, each of which will grow into a whole new animal complete with eyes, mouth and internal organs.

Scientists know the process involves mechanisms normally found in developing embryos, but are still not clear about what they are.

The new US study of zebrafish has identified a key cellular pathway that appears to trigger regeneration by switching on certain genes.

"This is the first real molecular insight into what is happening during limb regeneration," said lead researcher Dr Scott Stewart, from the Salk Institute in La Jolla, California.

"Until now, how amputation is translated into gene activation has been like magic. Finally, we have a handle on a process we can actually follow."

The Salk scientists focused on a biological 'priming' system that keeps embryonic cells ready to become whatever kind of tissue they are destined to be. They discovered a particular enzyme, or biological catalyst protein, seemed to be crucial to the process.

The scientists now plan to take a closer look at the enzyme and find out how it operates. They also want to discover how the genes are switched off again once regeneration is complete.