Centenarians with the bodies of 50-year-olds will one day be a realistic possibility, say scientists.

Half of babies now born in the UK will reach 100, thanks to higher living standards, but our bodies are wearing out at the same rate.

To achieve "50 active years after 50", experts at Leeds University are spending £50m over five years looking at innovative solutions.

They plan to provide pensioners with own-grown tissues and durable implants.

New hips, knees and heart valves are the starting points, but eventually they envisage most of the body parts that flounder with age could be upgraded.

New lease of life

The university's Institute of Medical and Biological Engineering has already made a hip transplant that should last for life, rather than the 20 years maximum expected from current artificial hips.

The combination of a durable cobalt-chrome metal alloy socket and a ceramic ball or "head" means the joint should easily withstand the 100 million steps that a 50-year-old can be expected to take by their 100th birthday, says investigator Professor John Fisher.

Meanwhile, colleague Professor Eileen Ingham and her team have developed a unique way to allow the body to enhance itself.

The concept is to make transplantable tissues, and eventually organs, that the body can make its own, getting round the problem of rejection.

So far they have managed to make fully functioning heart valves using the technique.

It involves taking a healthy donor heart valve - from a human or a suitable animal, such as a pig - and gently stripping away its cells using a cocktail of enzymes and detergents.

The inert scaffold left can be transplanted into the patient without any fear of rejection - the main reason why normal transplants wear out and fail.

Proof of concept

Once transplanted, the body takes over and repopulates the scaffold with cells.

Trials in animals and on 40 patients in Brazil have shown promising results, says Prof Ingham.

They have licensed the technology to the NHS National Blood and Transplant Tissue Services so it can be used on any UK donated human tissue in the future.

The NHS is already looking into using the method on donor skin for burns patients.

Professor Christina Doyle of Xeno Medical, the medical device company that is developing the technologies, said the holy grail was to remove the heavy reliance on donor organs.

"That's where the technology will lead us eventually."

But she said: "To replace all donor tissue using this technology will take 30 to 50 years. Each single product will need to be designed and tested individually."

Prof Doyle said experts elsewhere were also working on similar regenerative therapies, but grown entirely outside of the body, to ensure that people can continue being as active during their second half-century as they were in their first.