South Koreans produce cloned human embryos
WASHINGTON – Scientists in South Korea have made nearly a dozen cloned human embryos that are genetic twins of patients with various medical problems and have isolated from those embryos batches of stem cells with the potential to replace failing tissues in those patients.
The experiments mark a significant advance in therapeutic cloning, the fast-paced but controversial field that aims to make customized heart tissues for heart attack patients, nerves for patients with spinal cord injuries and a host of other laboratory-grown spare parts genetically tailored to the patients who need them.
The single previous claim that stem cells had been derived from a cloned human embryo, reported last year by the same team at Seoul National University’s College of Veterinary Medicine, left some scientists doubting the results. Moreover, the process appeared to be hopelessly inefficient, requiring almost 250 human eggs extracted from female donors to get just one cloned embryo with its precious cache of stem cells.
In the new experiments, described in today’s online version of the journal Science, the team needed only 17 eggs on average to make each batch of stem cells, which have the capability to develop into any type of tissue. That means just a single egg-retrieval procedure of the sort used routinely in fertility clinics is now adequate to produce a colony of personalized cells with the potential to treat a wide spectrum of diseases.
If therapeutic cloning can indeed be achieved with the same efficiency as such a widely accepted medical procedure, it would deeply undercut one of the major ethics arguments against it: that it would require egg donations by countless women – at some risk – to make enough embryos and stem cells to be medically useful.
“I think this paper will have enormous impact on the political discussion,” said Rudolf Jaenisch, a stem cell researcher at the Whitehead Institute for Biomedical Research in Cambridge, Mass.
The new research was led by Woo Suk-hwang, a cow cloning expert whose recent rise to international fame for his stem cell work has made him somewhat of a folk hero in Korea.
In another major advance, the Koreans said they are cultivating the stem cell lines in dishes without any animal cells. Virtually all other human embryonic stem cell lines to date have been grown for at least a while on mouse cells, which secrete a cocktail of hormones that support the growth of finicky stem cells.
By growing the stem cells on a bed of human support cells instead of mouse cells, the team does not have to worry that animal viruses or other contaminants may prevent transplanting the stem cells, or tissue grown from them, into patients – the ultimate goal.
“We want to find a way to cure devastating diseases, and one of the big points of our research is patients (now) have immune-matched, cloned, embryonic stem cells,” Woo said in a telephone interview.
The team is now working to transform the cells into various kinds of tissues – a process at which scientists are becoming increasingly adept – but has no current plans to put them into patients, Woo said.