Scientists in the United States say they have been able to make human cells live longer by altering their genetic material.

The research may offer renewed hope for age-related illnesses and the fight against cancer.

Rejuvenated cells

Most cells in the body grow and divide to form organs and tissues but cells can divide only a limited number of times before they stop.

Now scientists have found out why.

It is to do with their chromosomes, the long threads of DNA at the centre of each cell.

The key to a long life?

The ends of each chromosomes are capped to protect them by structures called telomeres.

Each time the cell divides the telomeres gets shorter until the cell can divide no more.

Scientists at the University of Texas have discovered that making the telomeres bigger again encourages cells to divide and grow once more.

No magic elixir

The American team stress that it has not discovered the key to everlasting life but says the discovery may help in combatting certain diseases such as cancer where cells divide uncontrollably.

British experts said the discovery is important but add a note of caution.

Professor Kirkwood has words of caution

Professor Tom Kirkwood from Manchester University said: "Ageing is such a complex process that we shouldn't immediately hail this scientific advance as being a step on the path to eternal youth.

"Many people regard the issue of quality of life in older age as being much more important than necessarily being able to extend life span."

"But understanding how it is that cells change during the ageing process and how we can modify those processes gives us a much greater degree of insight into this enormous challenge."

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