- Damaged cartilage in joints can be regenerated
by pulling cells into the affected area with a magnet, says an orthopaedic
surgeon in Michigan. Alan Halpern, a surgeon in private practice in Kalamazoo,
believes that his technique could provide a cheaper, less invasive way
of repairing cartilage, the tough resilient tissue that buffers the bones
in joints.
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- "We have long been able to remove
chondrocytes--individual cartilage cells--from a patient, and grow them
in culture," says Halpern. But the problem is getting them back into
the damaged area and keeping them there, he says.
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- What Halpern does is drill into the bone
and insert small biodegradable magnets made of the same material as soluble
sutures. The material has been seeded with particles of iron. He then tags
cultured chondrocytes with 200-nanometre particles of magnetite, a strongly
magnetic form of iron oxide. "When these magnetically tagged chondrocytes
are injected into the joint, they migrate to the magnets implanted in the
bone, so they are in the right place to form new tissue," he says.
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- He has successfully tested the technique
in rabbits. "Cartilage from the rabbits treated with the tagged cells
looked like normal cartilage. It was not as rich in cells as the original
tissue, but it had the same shape and appeared functional," says Halpern.
"The joints in the controls, in which magnets were implanted but no
cells injected, had fibrous tissue which we know is not durable."
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- One of the latest methods of replacing
cartilage, introduced in 1995, involves opening up the joint, sewing on
some tissue taken from the leg and injecting cultured cartilage cells beneath
this membrane. The membrane keeps the cells in place. The average cost
of such an operation is $26 000.
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- Halpern, who has used this method successfully,
says his technique has the advantage that the joint does not have to be
opened up, because the magnets can be inserted using keyhole surgery.
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- He says that the new technique will also
be a lot cheaper because producing the magnets and tagged cells will cost
only a few hundred dollars. Halpern's company, Biomagnetics, will finance
further research and clinical trials.
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- Daniel Grande, a medical researcher at
North Shore University Hospital in New York who is familiar with Halpern's
work, says it could be important. "Using magnets is attractive in
theory," says Grande, "but more work will be needed to find over
what distance they can attract tagged cells, and whether implanted magnets
have any adverse effects."
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