Mayo Clinic researchers use magnetic attraction to improve stents, reduce blood clot risk

ROCHESTER, Minn. -- Mayo Clinic heart researchers have devised a new strategy to improve the effectiveness and safety of heart stents, which are used to open narrowed blood vessels and have been the recent subject of clotting concerns. Their novel approach is based on magnetizing healing cells from the patient's blood so the cells are quickly drawn to magnetically coated stents.

The research report appears in the Nov. 7 issue of the Journal of the American College of Cardiology (http://content.onlinejacc.org/). The Mayo team describes encouraging results from preclinical testing.

In the study, the cells were extracted from blood, and tiny iron-based paramagnetic particles were placed within the cells. Each stent was implanted through a tube (catheter) threaded through the blood vessels. Researchers then introduced the iron-tagged cells back into the blood vessel to test how well the magnetized stents captured the cells.

Because the healing cells -- also known as endothelial progenitor cells derived from circulating blood -- naturally fight blood clot formation, their swift magnetically guided arrival to the stent may reduce the chances of blood clot formation by lining the site fully and quickly, Mayo researchers say.

Results show a sixfold to 30-fold improvement in the magnetized stents' performance in capturing the healing endothelial cells, compared to the standard stents' ability to do so.

"The ability to rapidly coat implanted devices with living cells could accelerate local tissue healing and thereby reduce the risk of blood clot formation," says cardiologist Gurpreet Sandhu, M.D., Ph.D., lead investigator. "Our approach of magnetic cell targeting is the next generation of strategies for improving the safety of stents -- and it appears that magnetic forces may provide an elegant solution for cell capture. Additionally, this new magnetic targeting technology can be adapted to develop new cell-, gene- and drug-based treatments for cancer and other human diseases."

Dr. Sandhu adds that, while encouraging, the method is still experimental and not ready to be used on human patients. Researchers are refining their approach, including developing new biomaterials.

Significance of the Mayo Research
"Many people are currently concerned about the risk of blood clots associated in a small percentage of patients with the use of drug-eluting stents," says cardiologist and cardiac researcher Robert Simari, M.D., who co-authored the paper. "Our approach holds the potential to overcome the limitations of the current drug-eluting stent technology because we address the basic conditions of clot formation. One of the reasons clots can form in drug-eluting stent patients is that the area surrounding the stent is not relined fully or quickly enough with the cells in the body, called endothelial cells, that naturally fight blood clots. Our system delivers endothelial cells right where they need to be, rapidly, with the potential for limiting clot formation."

How It Works
Multiple steps led to the development of the new Mayo magnetic cell targeting stent system. For example, the researchers had to devise:

  • a way to successfully get endothelial cells derived from blood and grown in lab dishes to live and proliferate when tagged with tiny amounts of magnetically responsive material known as iron-based paramagnetic microspheres.
  • specially fabricated stainless steel stents coated with magnetic materials that demonstrated excellent ability to capture the magnetically tagged endothelial cells.

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Collaboration and Support
Other members of the Mayo research team are: Sorin Pislaru, M.D., Ph.D.; Adriana Harbuzariu, M.D.; Rajiv Gulati, M.D., Ph.D.; Tyra Witt; and Nicole Sandhu, M.D., Ph.D. Their work was supported by a grant from the National Institutes of Health.

Description of Animation
A stent is inserted by catheter into the blocked vessels. The catheter then delivers the healing cells into the stented area. The magnetized cells are drawn to the coated magnetic stent.

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