Tissue engineers grow penis - with feeling

Tissue engineers who recently demonstrated penis replacement in animals have now added a vital missing component - nerve cells.

The nerve cells are very important - they are responsible for all the sensory function, says Anthony Atala, at Boston Children's Hospital. In order to do complete [penile] replacements we need to make sure all of the parts are there, including the nerves.

In September 2002, Atala and his colleagues replaced missing chunks of penis in live rabbits with tissues grown in the lab. But the replacement penile tissues consisted only of muscle and endothelial cells, which were inserted alongside intact nerve cells. Their new work is the first time that penile nerve tissue has been regenerated.

This is exciting and extends their work logically in several directions, says reconstructive surgeon Hunter Wessells of the University of Washington School of Medicine in Seattle.

The regeneration of nerves is an important step towards one day creating engineered replacement penile tissue for men who have lost parts of the penis following prostate cancer surgery or an accident, or to enhance the genitals of children born with abnormalities.

Mimicking nature

The secret to regrowing the nerve cells is mimicking nature, explains Atala. His team began by building millimetre-wide collagen channels. These replicate the sheaths that, like the insulation around a bundle of electrical wires, surround nerves in the body.

The team then cut away the nerve cells in the penises of live rats and sewed the collagen channels to the severed nerve stumps. After three months, functional nerve cells one centimetre long had grown inside the channels.

The physical support from the collagen appeared to be all that was needed to coax the nerve cells into growing. The collagen-supported cells grew just as well as nerves that were grafted on in experiments conducted for comparison.

The next challenge will be encouraging them to grow to even greater lengths without losing their functionality, says Atala.

Splice and connect

In the next few years, Wessels envisions using the technique to solve the challenging problem of returning feeling, or just the ability to have an erection, to men with intact penises who have lost nerve function.

Growing nerves in situ could replace the technique of nerve grafts, which requires the removal of valuable tissue from another part of the body. Nerve grafts were first used in penises in 2000.

But he says it will be closer to 10 years before a fully-functional tissue engineered penis is grown in the lab and attached to a man or child. That will require overcoming the challenge of splicing and connecting nerves in the lab-grown penis to the central nervous system, he warns.

The new research was presented by Atala at the annual meeting of the American Urological Association in Chicago on Tuesday.

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