Researchers, reporting in Science, have announced the successful treatment of a mouse with sickle-cell anaemia using stem cell lines created from adult mouse cells.
Rudolf Jaenisch, of the Whitehead Institute for Biomedical Research in Cambridge Massachusetts, and Tim Townes, of the University of Alabama at Birmingham, worked with colleagues to show that stem cells produced without embryos can be used to cure disease. This opens up the possibility that one day therapies could be created from a person's own tissue, meaning there would be no risk of rejection by the immune system.
The team used iPS (induced pluripotent stem) cells, which are adult stem cells that have been reprogrammed to behave like embryonic stem cells. The cells were taken from a mouse that had been genetically modified to display the symptoms of sickle cell anaemia; a genetic disease that produces abnormally shaped red blood cells, which are less efficient at transporting oxygen around the body. Once the cells had been transformed into the embryonic state they were encouraged to develop into potential bone marrow stem cells. By replacing the defective gene causing sickle cell, these would then produce healthy red blood cells. The engineered cells were then injected back into three sick mice. Twelve weeks later the mice that had been treated were found to have more normal blood, with higher red blood cell counts than untreated sickle cell mice. 'This demonstrates that stem cells have the same potential for therapy as embryonic stem cells,' said Dr Jaenisch.
However, there are potential complications arising from the procedure. The retroviruses that are used to insert the therapeutic gene into the DNA of the stem cells have the ability to make random changes to DNA anywhere in the body, potentially leading to cancer. Dr Jaenisch said 'We need a delivery system that doesn't integrate itself into the genome. Retroviruses can disrupt genes that should not be disrupted or activate genes that should not be activated'. There are also concerns over how easy and safe it would be to transfer the procedure from mice to humans.
Further research will also be needed to find out how these stem cells compare with embryonic stem cells and adult stem cells, in order to find out which variety are the safest and most successful. There is speculation that a combination of cells might be used, or different cells for different diseases. Evan Snyder, a director for the Burnham Institute for Medical Research in La Jolla, California, commented, 'It's just like an artist who has a really wide palette of colours. To give you a beautiful picture, we want to be free to dabble in all the colours'.