First Cloned Embryo Yields Stem CellsThis is the achievement reported on Thursday by a team of researchers led by Woo Suk Hwang of Seoul National University.
"Because these cells carry the nuclear genome of the individual, after differentiation they could be expected to be transplanted without immune rejection for treatment of degenerative disorders," Woo said. "Our approach opens the door for the use of these specially developed cells in transplantation medicine."
The study was published online by the journal Science ahead of a meeting in Seattle of the American Association for the Advancement of Science.
Until now, only mouse cells have yielded embryonic stem cells, and there have been many failures to do the same using human and monkey embryos.
The South Korean team used the classic cloning technique, pioneered in Dolly the sheep, which is to take an egg and remove the nucleus, which contains virtually all of the DNA code for programming the egg into a human being. They then replaced the nucleus with one taken from an adult non-reproductive cell, fused them together and then cultured the egg in a warm nutrient bath so that it divided and developed into an early embryo.
Where they improved on this technique, though, was on several fronts. They had access to an extraordinarily large batch of fresh eggs — 242 donated by 16 unpaid volunteers — which enabled them to finetune their work as they went alone.
They also had stringent programs for timing the way the eggs were handled, and used a new procedure that gently extruded the nucleus rather than suctioned it out, thus reducing the risk of DNA damage to the egg.
Out of 242 eggs, the team cultured 30 blastocysts, or fertilized eggs, of which 20 developed into embryonic cell clusters. Only one of these 20 developed into a stem cell line; the scientists suspect that some of the cloned blastocysts may have suffered chromosomal abnormalities seen in other primate cloning attempts.
posted by Canadian Myelin Research Initiative at 8:01 PM
