In August, University College London researchers demonstrated a technique whereby endothelial progenitor cells – a type of stem cell shown to be important in vascular healing processes – were magnetically tagged with a tiny iron-containing clinical agent, then successfully targeted to a site of arterial injury using a magnet positioned outside the body.
The result was a five-fold increase in cells at a site of vascular injury in rats. The team also demonstrated a six-fold increase in cell capture in an in vitro flow system (where microscopic particles are suspended in a stream of fluid and examined to see how they behave).
Dr Mark Lythgoe, UCL Centre for Advanced Biomedical Imaging and lead researcher said, "Because the material we used in this method is already FDA approved we could see this technology being applied in human clinical trials within 3-5 years. It’s feasible that heart attacks and other vascular injuries could eventually be treated using regular injections of magnetized stem cells. The technology could be adapted to localize cells in other organs and provide a useful tool for the systemic injection of all manner of cell therapies. And it’s not just limited to cells – by focusing tagged antibodies or viruses using this method, cancerous tumors could be much more specifically targeted.”
Panagiotis Kyrtatos, also from the UCL Centre for Advanced Biomedical Imaging and lead researcher of the study, added: “This research tackles one of the most critical challenges in the biomedical sciences today: ensuring the effective delivery and retention of cellular therapies to specific targets within the body."
Now, Rice University and the Texas Heart Institute have received a two-year $1 million Challenge Grant to develop an advanced stem-cell-tracking technology based on an ultrasensitive class of magnetic resonance imaging (MRI) contrast agents invented at Rice in 2005.
The grant's purpose is the refinement of cell-tracking nanotube technology that could make magnetic resonance imaging (MRI) up to 40 times more sensitive than existing MRIs and help guide adult stem cells within the human body to repair damaged hearts.
The grant will help perfect technology based on an ultrasensitive class of MRI contrast agents invented at Rice in 2005. Prescribed for about a third of all MRI patients today, contrast agents increase the sensitivity of MRI scans and make it easier for doctors to deliver a diagnosis. The most effective and common of these clinical agents contain a toxic metal called gadolinium, which is sequestered by wrapping the metal in organic molecules called chelates.
In Rice's new contrast agents, the gadolinium is encased inside hollow tubes of pure carbon, called nanotubes, to eliminate the metal's toxicity. These 'gadonanotubes' are at least 40 times more effective at boosting MRI signals than traditional gadolinium contrast agents.
"There's a great deal of interest in using stem cells to regenerate damaged heart tissue, but there hasn't been a really effective way to track the cells within the body and test their effectiveness," said gadonanotube inventor Lon Wilson, professor of chemistry at Rice. "Gadonanotubes may be what's needed because they are small enough to internally label individual cells with a large number of nanotubes and sensitive enough to track the cells in real time."
In addition, the gadonanotubes make the labeled cells highly magnetic so that it may be possible to steer the cells through the body with an external magnetic field. This may aid in keeping the stem cells in a desired place for the several weeks it takes them to differentiate into heart muscle cells.
Adapted from the University College London and Rice University announcements.
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