LAST year, a team of scientists in California announced they had taken stem cells from the brains of rats and turned them into neurons in a Petri dish. It was good news: perhaps one day doctors would be able to do the same with people, extracting stem cells from the brain of, say, a Parkinson鈥檚 patient and making new neurons out of them to replenish the cells damaged in the patient鈥檚 brain.
Of course, the scientists were careful to stress that, were such a therapy to ever materialise, it would be years down the road. This was an animal study and it looked as if the neurons made in the lab didn鈥檛 make as many connections, or synapses, as regular neurons. Clearly the technique had yet to be perfected.
Except that a week before the findings were published, a second Californian team, working with Canadian biotech firm Celmed Biosciences, disclosed at a conference they had already done the experiment in a human鈥� in 1999.
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The patient was a 57-year-old man with Parkinson鈥檚 disease, and to assess the effectiveness the new neurons were implanted in just one side of his brain. The treated half of the brain is still doing well four years later, while the untreated half is showing signs of the disease. Michel Levesque, principal investigator at Celmed, says the patient now wants to get the cells implanted on the other side.
To Levesque, the experimental surgery is entirely in keeping with his calling as a physician. 鈥淲e鈥檙e taking care of patients,鈥� he says. But to other researchers, daring patient trials carried out before labs understand the science are the stuff of nightmares 鈥� especially when it involves something as potentially revolutionary as the stem cells that are increasingly being found in adult tissues as well as embryos. They fear that if some stem cell therapies move too quickly into the clinic, a mishap could occur that might jeopardise the whole enterprise.
The death of a single gene therapy patient in a clinical trial in the US a few years ago triggered a wave of nervous government inquiries, clampdowns from regulators and uncertainty about how to proceed. Is stem cell science heading the same way?
Certainly some stem cell therapies are being offered to patients surprisingly quickly. Surgeons at the Cleveland Clinic Foundation in Ohio are treating patients with damaged spinal discs by selecting bone-forming stem cells from bone marrow and injecting them into the spine. The idea is for the cells to turn into bone and fuse the vertebrae, which apparently alleviates pain. George Muschler, who designed the procedure, says patients respond well. Yet no formal clinical trials have been done to establish that placing such cells in the spine is safe and effective.
In March a 16-year-old boy from Almont, Michigan, became the first patient in the US to have bone marrow stem cells injected into a vessel feeding the heart. The boy had accidentally pierced his heart with a nail from a nail gun and doctors were hoping the stem cells would regenerate some of the injured tissue. It was headline news across the country, a high-profile feel-good story about the magic of stem cells. But just last month, regulators from the US Food and Drug Administration stepped in to ask the team at Beaumont Hospital in Royal Oak, Michigan, not to do another procedure. The FDA does not comment on ongoing cases but hospital officials say the agency felt the procedure was risky and that not enough studies had been done to warrant the human test.
Nobody is being accused of recklessly gambling with patients鈥� lives: the Michigan boy continues to do well and improve. What鈥檚 more, the same procedure is being tested with so far positive results in European clinical trials. But in the US at least, the idea of hospitals offering treatments based on experimental and unproven science is clearly worrying regulators.
Part of the problem is that many doctors automatically assume that because stem cells are not drugs they require neither government regulation nor clinical trials. Doctors tend to see cells as an extension of the patient and stem cell therapy as a procedure rather than a product that must be regulated. And in a sense, this is understandable. After all, new surgical techniques are introduced without randomised controlled trials or FDA approval. And bone marrow transplants have been routine for over 30 years.
Another part of the problem is that the rules governing this kind of research in the US have not yet been communicated loudly and clearly enough to doctors and researchers. Many will know that the FDA regulates embryonic stem cells and adult stem cells that are highly manipulated in culture. But other therapies fall in a fuzzier grey zone. Just how much cell manipulation has to take place before a therapy must be regulated? The FDA鈥檚 rules are hard to follow.
In order for the most people to benefit from stem cell therapies, they will have to be tested for safety and efficacy. That is the gold standard we apply to the medicines we transiently put in our body. It is surely sensible to make sure that a cell we inject into the body, perhaps permanently, conforms to that standard as well.