In the light of the Korean stem-cell scandal, many big claims about stem cells are looking decidedly doubtful. Hyeoni Kim believed that the miracle cure for his paraplegia was around the corner. He had been paralyzed at just 8 years old when he was hit by a car on his way home from school. So when South Korea's science superstar, Woo Suk Hwang, asked if his team could take skin cells from Kim and use them to obtain stem cells that might one day provide a cure, Kim and his family were delighted. When Hwang visited him in hospital in April 2003, the boy, then 9, asked him if he would walk again. "I promise," Hwang replied. That promise became immortalized in a Korean postage stamp showing a man rising from his wheelchair. But it was always highly questionable. Even if Hwang had managed to derive cloned embryonic stem cells (ESCs) from the skin cells of Kim and 10 others - as he claimed in May 2005 - he would still have been a long way from mending Kim's paraplegia.
Stem cell science has been hailed as modern medicine's best hope - to treat the untreatable, to keep us fit in old age and even, perhaps, to help the severely disabled to walk again. But scandal in South Korea has rocked this science - with one of its leading proponents labeled a fraud, and as the scientists reflect on the ethics of their work and its practical limits, where does this leave all of us, the potential patients?
Stem cells, unlike ordinary cells, have the unique power to re-create themselves when they divide. There are two types: the first, adult stem cells, are cued up to become particular cell types - say nerve, blood, bone or heart. These can carry out valuable repairs - but only in their specialist part of the body. The second group is embryonic stem cells. Found in the early human embryo, these are highly sought after because they can re-create themselves indefinitely. Also, since they are not yet switched to become specific cell types, they have the potential to repair damaged and diseased organs anywhere in the body.
Dr Hwang claimed to have created 11 stem cell lines from human embryos, cloned so that the cells exactly matched an individual patient - the Holy Grail of stem cell science. It turned out much of his work was fake, and crucially that he'd had to use far more human eggs than he'd said. The challenge now, for embryonic stem cell scientists at least, is to find ways to make stem cells without using vast quantities of human eggs - in short supply and, for some, ethically questionable. Until now, scientists have relied on creating stem cells from left over embryos from IVF. Before the Hwang expose, researchers had hoped to join the elite club of scientists using cloning to study the cellular processes behind disease. Now, to avoid using up human eggs on an uncertain technique, most workers have a plan for a new - and potentially controversial - way around that: cloned human-animal hybrids. Researchers now would like to use non-human eggs - for instance rabbit eggs. But therapies are at least 10 years away. A team at the University of Cambridge has another plan. Roger Pedersen, director of the centre for stem cell research at the university, told us about a plan that avoids cloning, and fresh human eggs, and relies instead on off-the-shelf matches from a bank of stem cell lines from selected donors. Then there's the man with a third way to avoid the need for human eggs. Mohammed Taranissi runs one of the UK's most successful fertility clinics. He's promoting what he calls "stem-brid" technology, which uses the stem cell line itself as a surrogate egg. But there's a new realism now among embryonic stem cell scientists about how long it will be before they can help people.
That leaves their counterparts working on adult stem cells. They now expect to deliver treatments much sooner. One team, at the London Chest Hospital, is using adult stem cells taken from a patient's own bone marrow to try to repair the damage caused by a heart attack. Dr Anthony Mathur is the cardiologist in charge of the trial - the largest of its kind in the world. He is quoted as saying: "My passionate feeling here is that this type of therapy, cellular therapy, is going to revolutionize the way we practice medicine." Half the patients are treated with stem cells and half with just the fluid, or growth factor in which the cells are found. Neither Dr Mathur nor the patients know who's getting what but that's crucial in order to gather definitive, scientifically controlled data. Across London, another adult stem cell trial could yield results within months. At the Institute of Neurology, they hope to use unique adult stem cells from the lining of a patient's own nose to treat nerve and spinal cord injury. Professor Geoffrey Raisman, who's leading this research was quoted on BBC: "The interest in embryonic stem cells has led to adult stem cells being very much neglected. And whereas I think for embryonic stem cells we're talking about a long time ahead before these cells are going to be in use, in our case we're thinking of clinical trials within this year." It would seem a safe bet that adult stem cells will deliver first - but the enthusiasm for this science as a whole is still there, despite the reality check brought about by Dr Hwang.
I agree completely with Prof. Roger Pedersen from Cambridge who says: “We hope that discoveries that are made quietly and without the glare of lights... will ultimately change the way we treat diseases”.
