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S. Koreans enhance cloning of stem cells

Page 3 of 3 -- Around the world, scientists have been establishing major efforts to create and study human embryonic stem cells, which can become any cell in the body. These efforts are aimed at answering a wide range of questions about how the body develops, and how this knowledge might be used to fight diseases.

What the South Korean team has been able to do is create human embryonic stem cells with the genetic material of particular patients. With cloning, also called nuclear transfer, the scientists take a cell from a patient, remove the cell's nucleus containing the genetic material, and place this nucleus in an egg cell that has had its own nucleus removed. This hybrid cell is then stimulated to grow for several days, until it becomes a nearly featureless ball of about 200 cells, a type of embryo known as a blastocyst.

The first application of this technology is the creation of cells to study diseases. The South Koreans created a human embryonic stem cell with the DNA of a 6-year-old girl who suffers from juvenile diabetes. Now scientists can observe how these cells develop into more specialized cells and compare this with the development of embryonic stem cells that do not have the genes that contribute to juvenile diabetes. This could show them where the first problems arise that lead to the disease.

The other principal application, a more distant prospect, is therapeutic. In the Science paper, the team reports creating nine embryonic stem cell lines from patients who have suffered spinal cord injuries. In theory, the embryonic stem cells from one of the patients might one day be coaxed into becoming a more specialized nervous system cell and then be given back to the original patient, repairing damage. Because these cells were cloned from the patient, it is thought that the risk of rejection would be minimal, though that is not certain.

The scientists said that the improvements in efficiency came from a combination of technical changes, including a better way of growing the embryonic stem cells, using human cells to support them -- and, more simply, a lot of practice.

Gareth Cook can be reached at  

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