A milestone has been passed in the field of tissue engineering: the first group of patients has received organs that were grown from their own cells in a laboratory.

Scientists hope that laboratory-grown organs may one day help bring to an end the shortage of organs for transplantation, while avoiding the risk of rejection and infection that accompanies a donor organ.

Dr Anthony Atala will announce a long-term success today relating to seven children and teenagers who had implanted bladders grown from their own muscle and bladder cells.

He is working to grow 20 different tissues and organs, including blood vessels and hearts, in the laboratory.

Skin is already routinely grown, as is cartilage for knee implants. There are also efforts to grow the spongy tissues that swell with blood to make a penis erect.

"Dr Atala and colleagues should be praised for the milestone they have reached," said Dr Steve Chung of the Advanced Urology Institute of Illinois.

He added that more work was needed to follow up this "promising" report so that the technique could be used routinely.

Dr Atala, who is the director of the Institute for Regenerative Medicine at Wake Forest University Baptist school of medicine, Winston Salem, in North Carolina, describes in The Lancet how he grew the bladders from cells taken from young people between the ages of four and 19 who had poor bladder function because of a congenital birth defect that causes incomplete closure of the spine.

Since 1990 Dr Atala has developed an alternative way to build bladders, based in part on experiments he performed on dogs. In 1999 he implanted the first organ in a human patient.