Dr. Kirsty Horsey, Progress Educational Trust
12 February 2004
[BioNews, London]
Scientists in South Korea have extracted and grown stem cells from cloned, early human embryos, a breakthrough in 'therapeutic cloning' research. Using a modified version of the technique used to clone Dolly the sheep, the team, based at the Seoul National University, created 30 cloned human embryos. The researchers managed to extract stem cells from 20 of these, from which they managed to grow one human embryo stem (hES) cell line in the laboratory. Their work, which will be published in the journal Science, has been hailed as 'a landmark paper' by other scientists, and could pave the way for research into new treatments for many diseases.The stem cells present in very early embryos are the body's 'master' cells, capable of growing into any type of tissue. Since the unveiling of Dolly the cloned sheep, in February 1997, scientists have been investigating the possibility of using stem cells from cloned, early human embryos to develop tissue-matched therapies for diseases such as Parkinson's disease and diabetes: an approach known as therapeutic cloning.
To create Dolly, scientists at the Roslin Institute in Scotland used a technique called somatic cell nuclear transfer (SCNT), which involved transferring the nucleus of an adult sheep mammary gland cell into a donor egg stripped of its own genetic material. Since then, many other species of animal have been cloned using this technique, or modified versions of it. But creating SCNT embryos from humans (or any primate) has proved very difficult, although several groups have managed to isolate embryo stem cells from IVF (in vitro fertilization) embryos. Such cells are being used to carry out research into new therapies, although if used in human patients, they would face rejection by the body's immune system. Stem cells isolated from a person's own cloned (or reprogrammed) body cells would be an exact genetic match, however, and would not face transplant rejection problems.
Scientists at the US firm Advanced Cell Technology (ACT) first reported the creation of cloned human embryos in November 2001, but the team, lead by Dr Robert Lanza, did not manage to extract any stem cells from them. Commenting on the new research, Lanza said: 'you now have the cookbook, you have a methodology that's publicly available'. The South Korean team, lead by Drs Woo Suk Hwang and Shin Yong Moon, carried out their work on 247 unfertilised eggs donated by 16 women. The researchers removed the genetic material from 176 of them, choosing those at the most suitable stage of development. They removed the nuclei of these eggs, and replaced them with the genetic material from cumulus cells (cells that surround a developing egg), taken from each of the egg donor women, so that each clone was an exact genetic copy. 'They had an incredible amount of eggs and an opportunity to perfect the protocols; they tried 14 different protocols' said Dr Jose Cibelli, formerly of ACT. Their method yielded blastocysts (five or six day old embryos that contain ES cells) around 26 per cent of the time.
The discovery will provide scientists with a 'unique opportunity' to study human disease, says stem cell scientist Ron McKay. However, the Editor-in-chief of Science, Donald Kennedy, cautions that 'it may be years yet before embryonic stem cells can be used in transplantation medicine'. The breakthrough is also likely to reignite the debate over regulating attempts to clone human beings, whilst allowing therapeutic cloning research to continue.
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Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.