June 12, 2012
Some Stem-Cells May Not Be The Answer For Heart Disease
The use of stem-cells -- building-block cells that are harvested from embryos or adults -- to treat heart disease could rely on faith as much as it does science, after billions of dollars in research has not produced the results that researchers have been looking for.
Questions and concerns on the topic arose during the recent opening of the multi-million-dollar Scottish Center for Regenerative Medicine (SCRM) in Edinburgh, chaired by Sir Ian Wilmut, the renowned scientist whose Dolly the sheep clone in 1996, was a groundbreaking step in stem cell technology.
During the opening ceremonies of the Center, Christine Mummery of the Leiden University Medical Center in the Netherlands discussed how a 2001 claim, based on mice experimentation, indicated that bone-marrow cells could mend heart damaged by coronary disease, caused a mad rush of people to the clinics looking for a cure-all.
With nothing in the way of systematic research in animals, the first patients were being treated within a year, prematurely by Mummery´s account. She argued that the paper that launched the mass stampede was “completely wrong,” and subsequent studies proved that. But despite the findings, the 2001 paper has never been withdrawn.
Norwegian professor Harald Arnesen in 2007 voiced his concerns over those heart trials as well. He concluded that they were “not convincing” and that one German team had achieved striking results only because the control group had done particularly badly. Arnesen called for a moratorium on this kind of stem-cell therapy, based on that research.
But neither Arnesen, nor Mummery, could deter clinicians. Another trial, the largest to date, began in January 2012 and included 3,000 heart-attack patients recruited from across Europe. The trial was funded by the European Union as well.
The idea behind the trials is straightforward. During a heart attack, a clogged blood vessel starves heart muscle of oxygen. Up to a billion heart muscle cells, called cardiomyocytes, can be damaged, and the body responds by replacing them with relatively inflexible scar tissue, which can lead to fatal heart failure.
What is notably surprising, explained Mummery, is that stem cells come in many different forms: Embryonic stem cells are the building-blocks of the body and have the potential to turn into all 200 cell types found in the human body. Adult stem cells, however, are limited in what they can do. For example, bone marrow stem cells only generate blood cells.
So, the 2001 study claiming that bone marrow stem cells could turn into healthy heart muscle was a surprising and exciting claim, although a bold move.
Analysis in the human heart trials have shown that, at best, the amount of blood pumped during a contraction of one heart chamber rose by a mere 5 percent after treatment. While it may be significant for a patient whose heart efficiency has fallen to 30 percent of normal, the results are still relatively meager.
Mummery, et al., said it is difficult to turn stem cells into the right type of cell reliably, and there are a number of other risks, such as uncontrolled growths.
The key to making real progress with stem cells is completing rigorous systematic research before jumping the gun, as the 2001 study did. It takes careful experiments, not belief, to make a huge leap from the laboratory to the hospital.