Much research remains to be done before we see stem cell treatments, writes Dick Ahlstrom, Science Editor
Public confusion will follow reports that a doctor is Cork is offering medical treatments using "stem cells" purchased from Switzerland. While stem cell research is very definitely under way and promises great things, there are currently no proven stem cell treatments against any disease available anywhere in the world.
It is reported that people suffering from Multiple Sclerosis (MS) - a progressive neurological disorder that robs people of their movement, speech and independence - are paying large sums for the treatment. Vulnerable people, who are keen for a cure, will often ignore forthright recommendations against spending money on such treatments, recommendations by credible support bodies such as MS Ireland.
The unfortunate truth is that we do not yet have a stem cell-based treatment for MS and there isn't one in prospect in the short-term. If anything, the nature of MS, which affects nervous tissues throughout the body, is a particular challenge for stem cell researchers.
Far easier, yet still not available, are stem cell treatments for the damage caused by heart attacks.
Public confusion is not helped given the way that stem cell technology is sometimes talked up in the media. It offers huge promise and indisputably has the potential to cure disease, but we have not got there yet. Much research remains to be done before we see off-the-shelf stem cell treatments.
Stem cells themselves are of great interest to medical researchers because they are the "starter" cells from which other cell types grow.
These are truly universal cells, ready to divide and grow into the dozens of tissue types found in the body. It is this versatility that scientists hope to exploit if they can encourage or coerce them to grow into heart cells, blood vessels, brain cells, nervous tissue and so forth as a way to cure disease.
The most "powerful" and potentially most useful stem cells are those recovered from the early embryo, when it is no more than a hollow shell. However, recovering cells from this source is ethically fraught because it results in the destruction of a living embryo.
Stem cells come from other sources as well. They can be recovered from umbilical cord blood. There are also stem cells available in adult tissues, but these are far less versatile. If recovered in the liver they tend to grow only into the various liver cells, and if from the bone marrow they only become blood cells. It is simply not enough to collect and grow these cells however.
You have to be able to dictate what they change into and where they go in order to treat disease.
Like electrical wires protected by plastic, a layer of cells called the myelin sheath protects nerve fibres. Patients with MS suffer a progressive loss of myelin, leaving the nerve fibres exposed and unable to transmit signals properly.
In the case of MS you want the stem cells to travel to the damaged nerve fibres and then change into myelin cells before lodging to renew the missing sheath. This however demonstrates the great challenge in the use of stem cells.
First, if stem cells are universal and can change into anything, what will force them to go directly to the nerve cells? How can you ensure they don't wander into other tissues? Second, even if you can get the stem cell into position near the nerve fibre, how can you ensure it changes into the right cell type? Will it become more nerve fibre or myelin or some other nearby tissue?
Scientists have not yet overcome these problems and so are not in a position to use stem cells to treat human disease. Nor is there any study showing that if tried in humans these stem cells will be safe and won't cause other diseases.
Researchers are getting around some of these challenges in the lab however, leading to hopes that treatments will come in time. All cells talk to one another by releasing signalling proteins. One approach is to surround the stem cell with the signalling proteins appropriate to the tissue type you want to create.
With heart attack patients, stem cells are injected close to the site of damage where they change to become replacement heart muscle cells. A post-heart attack treatment is under initial human trials, the closest thing we have to a working stem cell treatment, but one still in its earliest experimental stages.
There are those who will argue they have received benefit from unproven stem cell treatments. The Swiss supplier points to successful case histories on its website.
However, these are not worth the time or effort of reading. Only strict and properly structured clinical trials can prove the efficacy of a medical treatment. Anecdotal claims do not count in serious medicine, real evidence is necessary.
This kind of personal testimony is also potentially suspect due to the placebo effect. Some patients in well done medical trials will be given a placebo, usually sugar tablets, and as with patients who actually receive a test drug, will be asked how well the drug worked.
In trial after trial, researchers find that between 30 and 40 per cent of those receiving the placebo will report an improvement in symptoms. One can therefore assume that a large fraction of the positive outcomes seen on the Swiss website were attributable to the placebo effect. Where are all the failures?