The man who grew a finger

In every town in every part of this sprawling country you can find a faceless sprawling strip mall in which to do the shopping.

Rarely though would you expect to find a medical miracle working behind the counter of the mall's hobby shop.

That however is what Lee Spievak considers himself to be.

"I put my finger in," Mr Spievak says, pointing towards the propeller of a model aeroplane, "and that's when I sliced my finger off."

It took the end right off, down to the bone, about half an inch.

"We don't know where the piece went."

The photos of his severed finger tip are pretty graphic. You can understand why doctors said he'd lost it for good.

Today though, you wouldn't know it. Mr Spievak, who is 69 years old, shows off his finger, and it's all there, tissue, nerves, nail, skin, even his finger print.

'Pixie dust'

How? Well that's the truly remarkable part. It wasn't a transplant. Mr Spievak re-grew his finger tip. He used a powder - or pixie dust as he sometimes refers to it while telling his story.

Mr Speivak's brother Alan - who was working in the field of regenerative medicine - sent him the powder.

For ten days Mr Spievak put a little on his finger.

"The second time I put it on I already could see growth. Each day it was up further. Finally it closed up and was a finger.

"It took about four weeks before it was sealed."

Now he says he has "complete feeling, complete movement."

The "pixie dust" comes from the University of Pittsburgh, though in the lab Dr Stephen Badylak prefers to call it extra cellular matrix.

Pig's bladder

The process he has been pioneering over the last few years involves scraping the cells from the lining of a pig's bladder.

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How it works in detail The remaining tissue is then placed into acid, "cleaned" of all cells, and dried out.

It can be turned into sheets, or a powder.

It looks like a simple process, but of course the science is complex.

"There are all sorts of signals in the body," explains Dr Badylak.

"We have got signals that are good for forming scar, and others that are good for regenerating tissues.

"One way to think about these matrices is that we have taken out many of the stimuli for scar tissue formation and left those signals that were always there anyway for constructive remodelling."

In other words when the extra cellular matrix is put on a wound, scientists believe it stimulates cells in the tissue to grow rather than scar.

If they can perfect the technique, it might mean one day they could repair not just a severed finger, but severely burnt skin, or even damaged organs.

Clinical trial

They hope soon to start a clinical trial in Buenos Aires on a woman who has cancer of the oesophagus.

The normal procedure in such cases is often deadly. Doctors remove the cancerous portion and try to stretch the stomach lining up to meet the shortened oesophagus.

In the trial they will place the extra cellular matrix inside the body from where the portion of oesophagus has been removed, and hope to stimulate the cells around it to re-grow the missing portion.

So could limbs be re-grown? Dr Badylak is cautious, but believes the technology is potentially revolutionary.

"I think that within ten years that we will have strategies that will re-grow the bones, and promote the growth of functional tissue around those bones. And that is a major step towards eventually doing the entire limb."

That kind of talk has got the US military interested.

They are just about to start trials to re-grow parts of the fingers of injured soldiers.

Skin burns

They also hope the matrix might help veterans like Robert Henline re-grow burnt skin.

He was almost killed in an explosion while serving in Iraq. His four colleagues travelling with him in the army Humvee were all killed.

He suffered 35% burns to his head and upper body. His ears are almost totally gone, the skin on his head has been burnt to the bone, his face is a swollen raw mess.

So far he has undergone surgery 25 times. He reckons he has got another 30 to go.

Anything that could be done in terms of regeneration would be great he says.

"Life changing! I think I'm more scared of hospitals than I am of going back to Iraq again."

Like any developing technology there are many unknowns. There are worries about encouraging cancerous growths by using the matrix.

Doctors though believe that within the so called pixie dust lies an amazing medical discovery.

To watch related videos, please go to BBC News.