Unethical procedures, exploitation and inflated promises, that is what generally makes the headlines — and so it is with regenerative medicine and stem cells. Media reports have left the distinct impression that the research is rather dubious.
First is the long-standing controversy over the source material: human embryos. Research banned by the most powerful man in the world — as US President George W. Bush was when he stopped federal support for such work in 2001 — must be a bit dodgy, right? Then there are the regular reports of companies that are exploiting vulnerable — and often seriously ill — patients with promises of expensive, but unproven, miracle cures.
But behind the headlines is a different story. Scientists doing the systematic research needed to get cellular therapies into the clinic are finally making headway. Trials are now under way for treating an eye disorder called macular degeneration using retinal cells. And a trial using immature glial cells to treat spinal-cord injury has restarted after the company running it pulled out in 2011 (see Nature 510, 18; 2014).
It has taken many years to get to the starting line, but shortcuts are simply not possible, despite charlatan claims. It takes time to learn how to coax stem cells — either from human embryos or from reprogrammed adult cells known as induced pluripotent stem (iPS) cells — to develop into the right sort of replacement cell. It also takes time to work out how to get these cells to integrate into the host tissue and to function. And the steps required to work out how many replacement cells need to be delivered, and how to deliver them safely, cannot be rushed.
The eye and spinal cord are relatively isolated systems. Much will be learnt from them, but the brain and heart are altogether more complicated. Fixing damage in these systems is crucial, however, because together they provide the biggest disease burden in developed countries.
Happily, clinical trials are on the horizon. Treatments for Parkinson’s disease are just a few years away from clinical testing. And some for Huntington’s disease may not be far behind.
“News reports need to be careful not to overhype the potential of cellular therapies.”
Taking any radical therapy into humans requires caution. Ideally, researchers should be able to use data from a patient in one trial to refine the approach for one in another. So a decision by the Global Force for Parkinson’s Disease, or G-force, to bring together teams from Europe, the United States and Japan to define standards for cell preparation and patient selection and monitoring for future trials is particularly welcome (see page 195).
The G-force seems to have learnt the lessons of moving research to the clinic too fast and in isolated teams. Multiple trials of cells derived from fetal brains to treat Parkinson’s disease began in the late 1980s, but stopped in 2003 because the outcomes were an uninterpretable mishmash. And trials using adult stem cells to treat heart failure have shown wildly varying outcomes (see Nature 509, 15–16; 2014), perhaps owing in part to a lack of good preclinical data. But systematic research has now shown that heart cells derived from human embryonic stem cells can engraft into damaged primate hearts and synchronize their beats to it, at least to some extent. Some of the monkeys developed arrhythmias, showing that the technique still needs improvement. The principle of the therapy has been proven, however, which gives confidence that clinical trials may become possible.
Designing trials to agreed standards will ensure that researchers can understand why any one patient benefited, or failed to benefit, from the treatment. This will magnify the efficiency of the trials and speed up the development of therapies. It is a model that deserves to be widely copied.
News reports need to be careful not to overhype the potential of cellular therapies. As the field inches towards clinical testing, it is important that researchers clearly communicate to the media what the therapies are likely to achieve — and what they are not. Early trials are unlikely to show cures, but that does not diminish their value: even small improvements in quality of life are important to a person with a serious disability. A blind person who becomes able to discern light from shade, a paralysed person who regains some feeling in a limb and a person with advanced Parkinson’s disease who can walk independently, if not normally — each will think it worthwhile.
Like all new therapies, stem-cell repair will improve through trial and error. These approaches promise more trial and, hopefully, fewer errors.
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