Cloning stem cells: What does it mean?

STORY HIGHLIGHTS

(CNN) -- A human embryo, containing about a couple hundred cells, is smaller than the period at the end of a sentence. Scientists need strong microscopes to see these precursors to life, and to take from them stem cells, which have the potential to become any cell in the body.

Earlier this week a breakthrough in this field was announced. A group of researchers published in the journal Cell proof that they had created embryonic stem cells through cloning. The scientists produced embryos using human skin cells, and then used the embryos to produce stem cell lines.

"It is an incredibly powerful approach with potential to generate almost any tissue in the body, genetically identical to the patient," said Jeff Karp, associate professor at Harvard Medical School and co-director of the Center for Regenerative Therapeutics at the Brigham and Women's Hospital in Boston.

Creating an embryo just from an egg and a skin cell seems like magic, but just how practical would the subsequent stem cells be? And does it actually amount to cloning?

What they did

Normally, an embryo is created when sperm enters the egg and it starts to divide. But, in the Cell study, Shoukhrat Mitalipov and colleagues at Oregon Health and Sciences University began with skin cells from an 8-month-old baby that had a genetic disease. They did not use sperm.

To create each embryo, they took the DNA out of an egg, so that it was hollow, and replaced it with the skin cell's DNA instead. The baby's DNA was the only genetic material being used.

With the help of chemicals, the egg started to divide just like a normal fertilized egg would. Then, within several days, embryos genetically identical to the baby were created, from which stem cells were derived.

Embryonic stems research is inherently controversial because in order to use the stem cells for science, the embryo, which is a collection of cells that could develop into a fully formed human, is destroyed, even though embryos in these procedures are left over from in vitro fertilization.

More:
Cloning stem cells: What does it mean?