STEM cells have for the first time been harvested from embryos without killing them, using a technique that could eventually provide children with a personal store of spare part tissue for treating diseases later in life. The successful experiment in the United States paves the way for scientists to create and “bank” master cells that are genetically identical to children before they are born. Should the child grow up to develop a disease such as diabetes or Parkinson’s, the cells could be used for therapy.

It also promises to address one of the strongest ethical objections to embryonic stem (ES) cell research. The cells have great medical potential as they can form any type of tissue in the human body, but their use is opposed by religious groups, as they can be extracted only by destroying embryos.

If the new procedure, tested so far only on mice, also works in human beings, it would allow researchers to obtain ES cells from embryos that remain intact and could go on to become children.

Once a single cell has been removed from an eight-cell embryo, conceived by IVF, it would be grown into a colony of ES cells in the laboratory. These would be frozen and banked, or donated for medical research. The rest of the embryo would then be implanted into a woman’s womb, where it would have a good chance of giving rise to a normal pregnancy. Single cells are already removed from embryos to screen for genetic diseases such as cystic fibrosis, without any known adverse effects.

Robert Lanza, of Advanced Cell Technologies in Worcester, Massachusetts, who led the research, said that children born in this way would grow up with a lifetime supply of perfectly matched stem cells that could be used to treat any diseases they might develop.

“If the cells were taken from an embryo that resulted in a child when implanted, they would be a perfect genetic match,” he said. “They could be frozen down and stored, and used throughout the child’s lifetime if it developed diabetes or heart disease, or even if it was going bald and wanted a hair transplant.”

The technique could also add to the stock of ES cells that can be used for research funded by the US Government. In 2001 President Bush banned the use of federal money for studies of new stem cells created by destroying human embryos, but tissue extracted this way could circumvent that ruling.

Details of the new method are published online in the journal Nature. Dr Lanza plans to repeat the experiment with human embryos within a year, with a view to providing ES cells for use in research.

In the study, which will be discussed today at the American Society for Reproductive Medicine conference in Montreal, Dr Lanza removed a single cell from mouse embryos that had grown to the eight-cell stage.

This cell was then placed in culture with other ES cells, where it developed into a fresh colony of the master tissue. Tests proved that the new ES cells were indeed pluripotent: capable of forming the full variety of tissue types.

The embryos from which the cells were removed were then implanted back into the wombs of mice. Of 47 such embryos transferred, 23, or 49 per cent, developed into healthy pups. The success rate was essentially the same as a control group of normal mouse embryos, which thrived 51 per cent of the time.

Scientists and ethicists welcomed the work, though they cautioned that it has yet to be repeated with human embryos.

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