Tuesday August 18 2009
Endothelial stem cells
Scientists have made “nanomagnets” that can guide stem cells to repair injuries, The Times has reported. The researchers have tagged stem cells with microscopic particles of iron, each “2,000 times smaller than the thickness of a human hair”, and used an external magnet to move them towards damaged arteries in rats, The Times's article on nanomagnets says. The technique has been shown to multiply by five the number of stem cells reaching targeted blood vessels.
This animal study investigated the targeting of endothelial progenitor cells, which are stem cells that are important in vascular healing. The research is encouraging, at least for vascular diseases, and, in time, the same techniques will no doubt also be tested for cancer therapies.
The researchers say that the nanoparticles used in this experiment are already approved for medical use by the US Food and Drug Administration, so human trials could begin within three to five years. If this is the case, then any treatments using this technique would be a minimum of a few years after that.
Where did the story come from?
This research on nanomagnets was carried out by Panagiotis G Kyrtatos and colleagues from the Centre for Advanced Biomedical Imaging at University College London (UCL) and the UCL Institute of Child Health in London. The study was supported by the Child Health Research Appeal Trust, the British Heart Foundation, the Alexander S. Onassis Public Benefit Foundation and the Biotechnology and Biological Sciences Research Council.
The study was published in the peer-reviewed Journal of the American College of Cardiology: Cardiovascular Interventions.
What kind of scientific study was this?
The researchers explain that although there have been promising advances in using cells to repair blood vessels, delivering the cells to the target area remains a difficulty.
In this laboratory and animal study the researchers magnetically tagged human endothelial progenitor cells (EPCs) with superparamagnetic iron oxide nanoparticles (SPIOs) and moved them to an area of arterial injury using a magnetic device positioned outside the body. SPIO nanoparticles are very small particles, usually between one and 100 nanometres wide (a nanometre is a millionth of a millimetre). EPCs are a type of stem cell that circulate in the blood and have the ability to become endothelial cells. Endothelial cells form the inner lining of blood vessels and are involved in developing new blood vessels.
The researchers first isolated human mononuclear cells (white blood cells) from donor blood. A particular cell type, called CD133+, was then isolated and cultured (grown) for three weeks. The cells’ behaviour outside the body, survivability and ability to differentiate or change into endothelial cells was then studied.
The researchers labelled the CD133+ cells with iron oxide nanoparticles to see whether the magnetic particles stuck to the surface of the cells. Computer simulations of the cells’ movements were also carried out.
Finally, rats in which the carotid artery in the neck had been artificially stripped of its lining were injected with the tagged cells. An external magnetic device was applied to the carotid artery for 12 minutes after some of the injections.
What were the results of the study?
Computer simulations predicted that the cells could be moved to targeted areas when the blood flow was similar to the flow found in a rat common carotid artery.
In the rat experiments, 24 hours after the injections the number of tagged cells found at the site of injury in the carotid arteries was five times higher in the rats exposed to the magnetic device than in those that were not.
What interpretations did the researchers draw from these results?
The researchers say that by using an externally applied magnetic device they have been able to move EPCs to the site of common carotid artery injury. They claim that the technology could be adapted to move cells in other organs, such as the heart or the brain, and could be a useful tool for localising stem cell therapies in other diseases.
What does the NHS Knowledge Service make of this study?
This study is promising in that it has demonstrated the feasibility of steering cells around the body. However, research has not yet shown that the repair process itself was improved. The technique will also need to be tested in humans.
Though the researchers do not explicitly mention cancer, this is one of the areas in which similar technology could potentially be used. More research could test whether it is possible to guide antibodies, viruses or chemotherapy drugs towards tumours while avoiding healthy tissue.
The scientists have said that as the nanoparticles used in the experiment are already approved for medical use by the US Food and Drug Administration, human trials of the technology could potentially begin within three to five years. This is quite a short time in research terms and means that there could be many more studies of this type reported in the next few years, before any license for use in humans is granted.