U.S. scientists for the first time have used a cloning technique to get tailor-made embryonic stem cells to grow in unfertilized human egg cells, a landmark finding and a potential new flashpoint for opponents of stem cell research.
The researchers were trying to prove it is possible to use a cloning technology called somatic cell nuclear transfer, or SCNT, to make embryonic stem cells that match a patient's DNA.
The achievement, published on Wednesday in the journal Nature, is significant because such patient-specific cells potentially can be transplanted to replace damaged cells in people with diabetes and other diseases without risk of rejection by the immune system.
This technique could ignite new controversy because some opponents consider it to be cloning, which they fiercely oppose.
"This paper will be seen as significant both by those who are trying to use SCNT to produce human patient-specific embryonic stem cell lines and by those who oppose human 'cloning' experiments," said Professor Robin Lovell-Badge, a division head at Britain's National Institute for Medical Research.
Stem cells are the body's master cells, the source material for all other cells. Proponents of embryonic stem cells say they could transform medicine, providing treatments for blindness, juvenile diabetes or severe injuries.
Normally, SCNT involves removing genetic material from the nucleus of the host egg cell and replacing it with the nucleus from adult cells, the technique used to clone animals such as Dolly the sheep in 1996. But scientists so far have failed to get these cells to grow and divide beyond a very early stage in humans and non-human primates.
Scientists in this study, led by Dieter Egli and Scott Noggle at The New York Stem Cell Foundation Laboratory in New York, retained the genetic material from the host egg and simply added the nucleus from the adult cells.
"Rather surprisingly – as this means that they are creating an embryo with too many copies of each chromosome – these constructs developed well and efficiently to the blastocyst stage (the stage … where the embryo is about 80 to 100 cells)," Prof. Lovell-Badge said in a statement.
She said the result falls short because the scientists did not obtain useful cell lines, but they may help explain why other techniques have failed.
"This study shows that the conventional approach to somatic cell nuclear transfer is inefficient in humans," said Professor Mary Herbert of Britain's Newcastle University and Newcastle Fertility Centre.
"While this approach does not in itself provide a solution, it takes us a step closer to understanding where the problems lie," Dr. Herbert said.
He said the latest study offers a new approach that may allow scientists to compare different techniques of creating these important and powerful cells.