BOSTON, July 23: Scientists have grown replacement organs for sheep, rats and rabbits using the animals' own cells and lab moulds to help the tissue take shape - a technique that could be used someday to make spare parts for people.

While scientists have already found ways to grow skin and cartilage, two Harvard researchers claim to be the first to have grown animal tissue from a variety of organs, including the heart, kidneys and bladder.

``As surgeons, that's what we dream about, having a shelf full of body parts,'' said Anthony Atala, who pioneered the technique with Dario Fauza.

Their new method to be presented today at a conference of the British Association of Pediatric Surgeons in Istanbul, Turkey has already been used to build new bladders and windpipes for sheep, a kidney for a rat, and leg muscles for a rabbit.

The organs built with tissue taken from both grown and fetal animals were transplanted into those creatures and have worked just fine so far, the researchers said.

The two doctors said the greatest hope for the technique could be in correcting common birth defects. They have developed a method for growing replacement organs for newborns while they are still in the womb.

For example, if a foetus has a malformed trachea, surgeons could extract some of those cells from the womb, grow the new windpipe in the lab and have it ready to be transplanted when the baby is born.

``This can save lives,'' Fauza said.

Tests on humans, in the womb and out, are set to begin within a year, and the researchers hope to get approval from the Food and Drug Administration for routine use within five years.

Cornell University researcher Thomas Mcdonald, who studies the development of sheep foetuses, said the method appears to be a way around the biggest obstacle to organ transplants - the body's rejection of foreign parts.

Normally, surgeons have been forced to use mismatched tissues to repair defects, like a piece of intestine to patch a hole in the bladder.

``It sounds like a wonderful technique and it sounds very doable,'' McDonald said. ``It's just that nobody has tried it until now.''

The procedure is tricky and requires balancing delicate laboratory work with microscopic surgery inside the womb. Doctors first detect birth defects using ultrasound, as early as three 1/2 months into pregnancy.

They operate on the foetus two-thirds of the way through pregnancy. Through small incisions, they lower a surgical camera and long, narrow instruments into the womb. Guided by a large video monitor, they remove a pea-size sample of the defective organ. Drugs are used to prevent the mother from going into labour.

Then it's on to the laboratory.

Under ventilation hoods, lab technicians separate different types of cells and place them in dishes of a clear solution rich in proteins and nutrients.

With the solution, which is the key to the process, the tissue can grow in an incubator at an astounding rate. A sample the size of a square cm could produce enough tissue within two months to cover two football fields.

Next, Atala and Fauza build the organ by draping fragile tissue over biodegradable scaffolds.

Copyright © 1997 Indian Express Newspapers (Bombay) Ltd.