(LONDON, ENGLAND) -- Scientists have successfully carried out the first human trials of replacement nipples that have been grown in a laboratory.

Although it is intended to develop the rest of the breasts using cells from a woman's own body, the nipples have been constructed from cartilage that has been derived from purified pig ear cells.

Progress in the new field of tissue engineering was discussed at a world congress of transplant experts in Rome last week. There is fierce competition among American biotech companies to be the first to capture the lucrative market for replacement breasts for cancer patients and those demanding cosmetic breast enlargement.

Curis of Cambridge, Massachusetts, which has developed the nipple technology and is the furthest ahead with research, believes that sales could exceed 250,000 a year. Britain is expected to be one of its biggest markets.

This country has one of the world's highest breast cancer rates, resulting in about 26,000 new diagnoses a year and more than 10,000 disfiguring operations. In addition, a further 15,000 women have cosmetic breast-enlargement operations.

Demand is expected to soar when natural tissue expansion can be used to enlarge breasts, instead of controversial artificial products such as silicone implants which have been linked to a range of side effects.

Craig Halberstadt is leading a research team at the Carolinas Medical Centre in Charlotte, North Carolina, which is working on behalf of Curis.

The tissue is grown using immature fat cells from elsewhere on a woman's body and expanding the tissue in a laboratory on a frame of biodegradable "scaffolding".

The expanded cell mass is injected back into the breast using a needle. "We are investigating how to use a material which is compatible with the body so as to enhance the ability of the host tissue to grow and maintain a natural shape," said Halberstadt.

"We are focusing on starting with smaller implants and gradually building up to larger ones, using a minimally invasive approach to implant the tissue back into the patient to reconstruct defects.

"It will have to be done in several stages because of the time it takes to establish a blood supply. But because it is minimally invasive we do not expect that to be a problem."

Work is also going ahead to find ways to reproduce complex internal organs.

Joseph Vacanti, a leading Massachusetts surgeon who pioneered the work on replacement breasts before selling the technology to Curis, is now looking at ways to reproduce complex internal organs such as kidneys and livers.

Speaking at the Rome meeting, he said: "We think this research on regenerating tissue can be applied to vital organs. The individual components are all commercially available. It is now up to researchers to make them work. The largest problem is not growing the cells, but creating a good enough blood supply to maintain a really large tissue mass."

David Sharpe, professor of plastic surgery at Bradford University and chairman of the British Association of Plastic Surgeons' breast special interest group, does at least one nipple reconstruction a week using the current techniques of removing skin from elsewhere on the body.

He welcomed the advent of the regrown nipple. "We also need something that will resist pressure," he said. "The nipple is the apex of the breast and a lot of things are pressed on it. Using our technique, they sometimes become quite flat."

The possibilities of the technology were heralded in 1995 when the American scientists Vacanti and his brother Charles unveiled a human ear grown from cartilage cells on the back of a mouse, which was providing its blood supply.

In the future it may be possible to regrow eardrums, damaged digestive systems and blood vessels.