Superparamagnetic particles of iron oxide were used to label blood cells. Doctors can use MRI to track the magnetic labels for over one week inside the body. It may help doctors track cells in the body to better determine if treatments work. Other forms of labeling use radiation and only can be tracked for a few hours.
Researchers showed that injecting immune cells containing magnetic particles into the bloodstream was safe and did not interfere with cell function. Magnetic resonance imaging (MRI) scans can then track the cells moving through the body.
“This could change how we assess new treatments affecting inflammation and the outcome of a heart attack or heart failure,” said Jennifer Richards, M.D., lead author and vascular surgeon at the University of Edinburgh’s Centre for Cardiovascular Science in Scotland.
With stem cell therapy, doctors can adapt blood cells to fight disease. But when developing these therapies, it’s hard to tell exactly where cells go and how many go where they are supposed to. Safely tracking them would help scientists better understand how new therapies combat heart disease.
Other tracing methods expose patients to excess radiation or only allow cells to be tracked for a few hours. But MRI scans use no radiation, and cells containing the particles can be monitored for at least a week.
There were four small-scale tests in humans:
* Six people were successfully given three thigh muscle injections of unlabeled cells, magnetically labeled cells, and an injection of just the magnetic material. The labeled cells were traceable up to seven days later.
* Two people were given six increasingly larger doses of magnetically labeled blood cells through a vein, and they had no negative effects.
* 12 people got intravenous injections of the labeled blood cells – six getting a high dose and six a low dose – which were traceable by MRI a week later.
* To test how well the cells travel to inflammation sites, one person was injected with the labeled blood cells, which were successfully followed by an MRI as the cells moved to an inflamed area of skin on the thigh. “This demonstrates that this method may be useful to facilitate the development of cell-based therapies in the future,” Richards said.
5 billion PBMC were labeled with SPIO. SPIO-labeled cells had similar in vitro viability, migratory capacity and pattern of cytokine release to unlabeled cells. Following intramuscular administration, up to 100 million SPIO-labeled cells were readily identifiable in vivo for at least 7 days using MRI. Using a phased-dosing study, we demonstrated that systemic delivery of up to a billion SPIO-labeled cells in humans is safe, and cells accumulating in the reticulo-endothelial system were detectable on clinical MRI. In a healthy volunteer model, a focus of cutaneous inflammation was induced in the thigh by intradermal injection of tuberculin. Intravenously-delivered SPIO-labeled cells tracked to the inflamed skin and were detectable on MRI scanning. Prussian blue staining of skin biopsies confirmed iron-laden cells in the inflamed skin.
Conclusions—Human PBMC can be labeled with SPIO without affecting their viability or function. SPIO-labeling for magnetic resonance cell tracking is a safe and feasible technique that has major potential for a range of cardiovascular applications including monitoring of cell therapies and tracking of inflammatory cells.