US stem cell research progresses despite limitationsBMJ 2005; 330 doi: http://dx.doi.org/10.1136/bmj.330.7506.1467-b (Published 23 June 2005) Cite this as: BMJ 2005;330:1467
Scientists in the United States, supported by private funds, are circumventing the so called “presidential” stem lines approved by President Bush in August 2001 for publicly funded research and are managing to conduct further stem cell research.
Currently, federal funding for stem cell research in the US is possible only on the 22 lines in existence before 9 August 2001. The US House of Representatives recently passed a bill to increase government funding for research on human embryos, and a Gallup poll in early May showed that 60% of Americans said medical research involving stem cells was morally acceptable. However, President Bush has said he would veto the bill (BMJ 2005;330:1285), because of his Christian belief that embryos were “emerging human life.”
The 22 stem cell lines are all thought to be unsuitable for human treatment, because they were grown on mouse feeder cells. These cells are required to prevent cells from automatically differentiating into other cell types (BMJ 2005;330:214).
However US scientists are trying to do what they can with private funding. At a New York Academy of Sciences symposium earlier this month Gordon Keller, professor of gene and cell medicine at Mount Sinai School of Medicine in New York and president elect of the International Society for Stem Cell Research, reported on his research.
This showed that the mesoderm generating haematopoietic and vascular cells in mice differ from the mesoderm that gives rise to cardiac cells, indicating that cell fates or destinations are established very early in embryonic development. Professor Keller heads an international stem cell centre in New York funded with $10m (£5.5m; €8.2m) from the financier Leon Black.
Professor Lorenz Studer, of the stem cell and tumour biology laboratory at Memorial Sloan-Kettering Cancer Center in New York, reported successfully transferring cloned embryonic stem cells to correct Parkinson's disease in mice. The new cells produced dopamine, and the mice no longer exhibited the chronic circling behaviour typical of “Parkinson's mice.”
Dr Ronald Crystal, chairman of genetic medicine at Weill Cornell Medical College in New York and an organiser of the symposium, said, “Parkinson's disease is a very good target because it's a very small area of the brain and a lot is known about the cells … and what is needed to cure the disease,” he said. But he pointed out that there are risks. “I think the gene therapy and stem cell fields are going to come together because you have to control stem cells. Gene transfer is the way to do that.”
Dr Ali Brivanlou, head of the laboratory of molecular vertebrate embryology at the Rockefeller University in New York, discussed human embryonic stem cell renewal or “stemness”—the ability to replicate rather than to differentiate into various cell types.
His group has shown that a particular signalling pathway determines self renewal in mouse stem cells but not in human embryonic stem cells. But a chemical from sea snails maintains mouse and human stem cells in a state of self renewal without the need for mouse feeder cells. Withdrawal of the compound leads to normal differentiation in both human and mouse cells.
John Burn, head of the UK's Institute of Human Genetics at the University of Newcastle upon Tyne, said that research using mouse and human stem cells is complementary. Many studies of developmental pathways can be done only in animal models, he said.
He cited, as a case in point, the cloning of human embryos from eggs grown in the laboratory, the discovery of which was reported at the 21st annual conference of the European Society of Human Reproduction and Embryology in Copenhagen this week.
He said: “It is almost certain that cloned eggs will never be used to treat infertile couples, because of the risk of malformation due to disturbed imprinting. If it is ever done, it will be based on several years of research in the mouse and other species.”
But he dismissed suggestions that stem cell research in mice was an alternative to human stem cell studies. “No therapeutic agent [for humans] can be generated from mouse stem cells, due to the risk of cross species transfer of infectious agents.” He added: “There's not a snowball's chance in hell that a patient will be treated with mouse stem cell derived tissues.”