Scientists have cured sickle cell anaemia in mice using stem cells produced without using embryos. The procedure involved reprogramming skin cells from the mice back to an extremely flexible embryo-like state, then replacing the defective gene that caused the disease. When the cells were injected back into mice they reversed the symptoms of the disease.

The study is the first to show that the new technique for producing stem cells, unveiled last month in Science, can be used to cure disease. It was hailed as a development that would make cloning largely irrelevant because it allowed flexible cells to be created without using embryos.

The team took skin cells from a mouse that had been genetically modified to mimic the symptoms of sickle cell anaemia, a genetic disease which produces abnormally shaped red blood cells less efficient at carrying oxygen round the body.

The researchers modified these skin cells by inserting four genes which act together as master regulators, rewinding the cells back to an embryonic state. Next the team coaxed the cells down a different developmental route to become the precursors of bone marrow stem cells which produce blood cells. The team replaced the defective gene that causes sickle cell and injected them back into the mouse's body. They report in Science that the blood and kidney functions returned to normal.

"This demonstrates that stem cells have the same potential for therapy as embryonic stem cells," said Rudolph Jaenisch at the Whitehead Institute for Biomedical Research.