FRIDAY, July 18 (HealthDay News) — Researchers say they have grown in mice the kind of functioning heart blood vessels that cardiac surgeons create with bypass operations.
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One ultimate goal is to replace some heart surgery with injections of laboratory-grown cells that would establish themselves in the body, providing a system of blood vessels for damaged hearts that need more oxygen, said Juan M. Melero-Martin, a co-author of a paper in the July 18 issue of the journal Circulation Research: Journal of the American Heart Association.
"We are proving the concept in mice who are compromised so that they don't reject human cells," said Melero-Martin, a research fellow at Harvard Medical School and Children's Hospital Boston. "For clinical use, the way we envision it, if a patient has need to vascularize ischemic tissue, we can get cells from the patient ahead of time, grow them and inject them back into the patient."
Ischemic tissue is starved of blood because of blocked arteries or other damage, and revascularization restores the vessels through which blood can flow to that tissue.
The research team is not using stem cells, which are controversial, because they are obtained from human embryos. Instead, they are using what are called progenitor cells, easily obtained from blood or bone marrow, which can grow to become various sorts of adult cells. The progenitor cells used in the study grew into full-fledged blood vessel systems in the laboratory mice.
The researchers combined two kinds of progenitor cells, one for those that line the surface of blood vessels, the other for cells that surround the lining and provide stability. They found that a mix of the two kinds of progenitor cells derived from adult blood and bone marrow or umbilical cord and adult bone marrow gave the best growth of blood vessels.
"Our next goal down the line is to use them in humans," said Joyce Bischoff, associate professor of medicine at Harvard and senior author of the report.
Much work lies ahead, she said. "We need to do a lot more animal studies to test how these cells behave in different tissues," Bischoff said.
"We have proved that the cells have the ability," Melero-Martin said. "Now we have to see how to implement this in a clinical situation."
A version of the sort of human medical experiment that they envision has already been done by physicians at Goethe University in Frankfurt, Germany. Two years ago, they reported a study with 75 people who had heart attacks. Some were given injections of progenitor cells, derived either from bone marrow or blood. Improved heart function was seen in those who got the progenitor cells, the German researchers reported.
The work being done at Harvard could eventually be used to treat a number of conditions in which new blood vessels would help, such as severe wounds, the researchers said.
A current goal is to lessen the time needed to grow blood vessels outside the body, Bischoff said. Extensive growth now is seen after seven days, and the hope is to reduce that to 24 to 48 hours.
"If you have ischemic tissue, it's dying tissue, so the faster you can establish blood flow, the better," she said.
SOURCES: Juan M. Melero-Martin, Ph.D., research fellow, and Joyce Bischoff, Ph.D., associate professor of medicine, Harvard Medical School and Children's Hospital Boston; July 18, 2008, Circulation Research: Journal of the American Heart Association
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