Scientists, for the first time, have cloned embryonic stem cells using reprogrammed adult skin cells, without using human embryos. But even so, the procedure raises ethical issues.
When the research group at Oregon Health and Science University announced on May 15 that it had turned human skin cells into embryonic stem cells for the first time it caused quite a commotion. The reactions ranged from horrified at the apparent breach of an ethical taboo, to amazement over this scientific breakthrough.
The procedure isn't new. The research group, headed by Shoukhrat Mitalipov, succeeded in producing so-called pluripotent stem cells, meaning cells that are capable of developing into any kind of tissue, using adult, rather than embryonic, stem cells.
The process used by Mitalipov is an important step in research because it does not require killing a human embryo that is, a potential human being to create transformative stem cells.
Significant step forward
The technique involves transplanting an individual's DNA into an egg cell that has been stripped of genetic material a variation of a method known as somatic cell nuclear transfer.
"A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells, into several different cell types, including nerve cells, liver cells and hearing cells," Mitalipov said.
He added that since the reprogrammed cells use genetic material from the patient there is no concern about transplant rejection.
The major advantage of this approach is that it does not use fertilized embryos to obtain stem cells, a technique that raises major ethical questions because the embryo is destroyed.
"The cytoplasm in the egg cell reprograms the differentiated [skin] cell back into a pluripotent cell nucleus," explained Andreas Trumpp, a stem cell researcher at the German Cancer Research Center in Heidelberg. "The cell divides and a small cluster of cells results a so-called blastocyte from which embryonic stem cells can be gleaned."
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Stem cell cloning remains highly controversial