Scientists progress in stem cell research

Experiments successful in curing mice of disease


Scientists at the Whitehead Institute have jumped a double hurdle in the race to cure disease with embryonic stem cells, the all-purpose clay from which the body is sculptured.

Working with mice, one team has mastered making embryonic stem cells metamorphose into cells that generate blood and immune systems. The other team converted skin cells from a mouse's tail back into the embryonic state and then, with the first team's technique, used them to cure a mouse whose blood and immune system had been destroyed. The experiments were published electronically Friday in the journal Cell.

The second experiment is the first demonstration of therapeutic cloning, a technique opposed by those who fear it may be used instead to clone a person. By providing proof of its possible benefits, the experiment "hopefully should influence the debate," said Dr. Rudolf Jaenisch of the Whitehead Institute in Cambridge, Mass.

Therapeutic cloning is based on the idea of taking a mature cell, such as a skin cell, from a patient, walking it back in biological time to its embryonic state, then growing mature cells of the type necessary to repair a diseased organ.

The controversy arises because the nucleus of the skin cell, containing the patient's genome or genetic information, would be injected into an unfertilized human egg whose nucleus had been removed. The injected human egg would be kept in laboratory glassware and allowed to divide a few times into an early embryo, from which embryonic stem cells can be harvested. If the embryo were placed into a woman's uterus, it might successfully develop.

Jaenisch and his colleagues have created mouse embryos by this method and converted them into blood-forming stem cells, first correcting an inborn genetic defect of the donor mouse by a standard genetic method. The blood-forming cells were then injected back into the mice that donated the nuclei. These mice had been irradiated to destroy their bone marrow cells and would have died without the new cells.

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