Correction.
The blood of mice treated with iPS cells (above) does not show the cells sickle present in untreated mice (top).
J. Hanna et al, Science
Skin cells reprogrammed to act like embryonic stem cells -. A first breakthrough reported in human cells there 2 weeks - already showing promising as a therapeutic agent. In today's online edition of Science , researchers describe the use of induced pluripotent stem (iPS) to relieve the symptoms of sickle cell anemia in mice. The technique is not safe to try in people, but scientists say it is proof of principle that iPS cells could one day treat human disease.
induced pluripotent stem cells excite scientists because they represent a way to get custom-made stem cells without the ethical barriers to the use of embryos or oocytes ( science Today ay, November 20). Researchers hope they might be able to use the technique to replace defective cells in the body with healthy cells containing the patient's own DNA.
Tim Townes of the University of Alabama, Birmingham, and colleagues wondered whether iPS cells could be useful in a mouse model of sickle cell anemia. (The blood cells are much easier to replace than are the cells that make up the fabric). In afflicted humans, red blood cells become curved and can not flow easily through blood vessels. The mice show many of the symptoms that patients are human, and they were particularly good candidate to test the capabilities of iPS cells, said Rudolf Jaenisch cell researcher strains of the Whitehead Institute and Massachusetts Institute of Technology, once in Cambridge, who worked with Townes on the project.
cellsThe first step was the creation of specific iPS mice. Researchers took cells from the skin of the tail of mice to sickle cell and the inserted copies of four genes that render the cells have the characteristics of embryonic stem cells. They also added a corrected hemoglobin gene in cells and caused to become producing blood stem cells. Finally, the researchers injected these partially differentiated cells in sickle cell mice that had been treated with radiation to kill their own blood stem cells. Within weeks, the new cells produce mature blood cells, and the symptoms of sickle cell disease have improved dramatically, reports the team.
Townes and Jaenisch said he initially collaborated on a project that has used nuclear transfer to the corrected stem cells, a process called therapeutic cloning. But experiments have failed, he said, because nuclear transfer was too inefficient to produce the necessary cells. The technique of iPS cells "is amazingly effective," he said.
The document is an important step, said Jose Cibelli of Michigan State University in East Lansing. Laboratory results for iPS cells have been impressive so far, he said, "but if they do not have a therapeutic value, they will be far from getting to the point of replacing the idea of therapeutic cloning."
the next important step for the field, Cibelli said, is to find reliable ways to differentiate the cells into various types of cells useful and be sure that no undifferentiated cells remain to cause potential tumors. Other experiments with iPS cells have suggested that they might tend to cause cancer, but none of the treated mice showed no signs of tumors after 12 weeks. This is a promising sign, Townes said, but would need much longer studies before the technique could be considered safe enough to try in humans.
Related site
- More information about sickle cell anemia
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