Ask most people why scientists are so keen to experiment with stem cells and it will not be long before they mention Alzheimer’s disease. Dementia patients might be elderly but they have become the poster kids for this new and controversial branch of medical technology.
When Chinese researchers claimed this week to have grown human brain cells in culture for the first time, many reports hailed the work as an important step towards a cure for Alzheimer’s. The disease, too, has become an issue in New York and Connecticut, where state politicians want to bypass the Bush Administration’s restrictions on federal support for embryonic stem (ES) cell research by funding it themselves.
Every time the media spotlight falls on these master cells, which can form any tissue in the human body, assertions about their potential to treat Alzheimer’s seem to follow. It is not hard to see why. Alzheimer’s afflicts about 400,000 people in Britain and 4.5 million in the US. Almost all of us know somebody who, like the late novelist Iris Murdoch, has been stripped of their faculties by this cruel degenerative disease. We fear it and pray that a treatment will be found before we become vulnerable ourselves.
Then there is the Reagan factor. Even those who thought little of the Great Communicator’s politics sympathised with his struggle against a condition that took away his finest gifts. His widow Nancy and his son Ron have become outspoken advocates of ES cell research, which they believe could spare other families the grief that they have had to endure.
Their stance has been particularly resonant because of the family’s previously close links with the pro-life lobby. The inference is plain: experience of this merciless disease is enough to overturn beliefs about the sanctity of the embryo. Ron Reagan Jr even agreed to speak at the Democratic convention last year, telling delegates that the US had a choice between “reason and ignorance, between true compassion and mere ideology”.
Few experts would dispute that he was right to point out that President Bush’s decision to ban federal funding of new ES cell projects is hampering research of great therapeutic promise. But the notion that Alzheimer’s patients are going to be the chief beneficiaries of the research — or even that they will benefit at all in the foresee-able future — is almost certainly wrong.
Talk to the scientists who work on stem cells or Alzheimer’s disease and most are puzzled that the two are so often mentioned in the same breath. They tend to think stem cells have little to contribute to this condition and even the most optimistic think that any advance is at least a decade away. Other approaches are more likely to lead to a treatment, while if the potential of ES cells is realised it will almost certainly be for something else.
Even advocates of ES cells concede this. Alzheimer’s is too devastating a disease to be a good candidate for ES cell therapy, they say. Should it prove possible to generate enough neurons to replace damaged ones — a difficult task in itself — there remains the troubling issue of where to put them. Cell death is so widespread in Alzheimer’s patients that much of the brain is affected. And our understanding of this complex organ remains so poor that trying to rebuild it from scratch isn’t really an option.
“It’s hard to know where you’d start,” says Stephen Minger, of King’s College London, who produced Britain’s first ES cell line. “There is so much damage that it would be a hugely challenging task to repair it all.”
Marcelle Morrison-Bogorad, of the US National Institute on Ageing, says: “What you’re dealing with here is a mind in disarray. It’s just a mess in there.” There is also growing evidence that memory loss and dementia set in before brain cells start dying in droves. This suggests that the problem lies not only with the cells themselves but also with the synapses, the connections between cells in which memories are stored.
As Michael Shelanski, of Columbia University, puts it: “Simply putting in more cells is not necessarily going to re-establish those connections.” Even if ES cells can help, they’re unlikely to bring back grandpa’s memory. They might slow the progression of the disease but won’t reverse damage that’s already been done.
Other less-hyped approaches stand a much greater chance of success. Vaccines that prevent the build-up of sticky plaques of protein look particularly encouraging, while anti-inflammatories, some vitamins and cholesterol-lowering drugs might also help.
Stem cells, however, are low on the radar screen. “There are many other avenues that are more likely to be valuable,” says Rachelle Doody, of Baylor College of Medicine in Houston. “There may be something that comes out of stem cell research that’s helpful in Alzheimer’s later, but it’s not the primary focus.”
The emphasis on Alzheimer’s ultimately does no one much good. It raises false hope among the relatives of Alzheimer’s patients. It risks diverting attention and resources from less fashionable research with a better chance of success. And it is giving the religious Right a powerful weapon with which to attack the whole field of stem cell research.
Pro-lifers and conservative columnists have already started to seize on the issue to suggest that the promise of ES cells is nothing more than a fiction. Once a few facts are manipulated to buttress a case, it becomes easier for critics to cast doubt on legitimate arguments, too.
Wesley Smith, for example, of the creationist Discovery Institute, based in Seattle, wrote recently in the Weekly Standard: “If biotechnology advocates would allow a grieving widow to believe cruel untruths about the potential for stem cells to cure Alzheimer’s, what other fairy tales are they telling us to win the political debate?” This alarms scientists working on other applications of ES cell research in which the prospects of success look much brighter. In Parkinson’s, for example, we know which cells go wrong — the dopamine neurons — and which brain regions are most affected. Previous experience with foetal and pig cells indicates that tissue transplants are likely to help. The same is true of type 1 diabetes.
ES cells are thus a very good bet for these conditions. Researchers seeking to translate their promise into therapy, however, worry that overblown claims about Alzheimer’s will politicise the entire field, to the detriment of patients.
“We have a duty to articulate in a responsible fashion what we think stem cell therapy can do,” says Minger, whose chief focus is on Parkinson’s disease.
“The Reagan intervention has meant that in the US, the debate now has very little to do with science and is almost all politics. I do not know of any reputable neurobiologist who has ever said that cell therapy for Alzheimer’s disease is a prime target. But the issue has become a lightning rod, both for those wanting a complete ban and those who want to throw an obscene amount of money at it. This does no one any good.”
