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Biomedicine

Stem Cells Repair Blood Vessels

A new method to boost growth of blood vessels with stem cells could improve cell therapies for diabetes and heart disease.

An efficient new method to generate what appears to be a novel type of stem cell could be a boon to diseases linked to lack of blood flow. Scientists in Massachusetts and Florida have developed a way to coax embryonic stem cells into a more adult form of stem cell that has the potential to form blood vessels. The new type of cells helped repair tissue in animals that had had heart attacks or eye damage due to diabetes.

Blood flows: Stem cells restore blood flow to a mouse whose blood vessels had been blocked. This series shows changes in blood flow in the injured leg, circled in red, over 30 days after receiving an injection of stem cells. The top image is 6 days postinjection, the bottom image is 30 days postinjection. Blue indicates no blood flow, with increasing blood-flow intensity indicated by green, yellow, and red.

“This is a significant achievement which may translate into therapy for a wide variety of disorders of insufficient blood vessels,” says Amish Raval, a cardiologist at the University of Wisconsin, Madison, who was not involved in the research.

The tissue damage that accompanies many diseases, including the ulcers that occur in diabetes and the heart-muscle damage associated with cardiovascular disease, is linked to an inadequate supply of blood. Researchers are currently trying to determine whether adult stem cells derived from bone marrow can boost blood flow in these diseases by triggering growth of new vessels. (See “Can Stem Cells Cure Heart Disease?”)

In the new study, scientists developed a way to turn embryonic stem cells into stem cells that are an earlier and thus more plastic form than the adult stem cells derived from bone marrow. Robert Lanza, vice president of research and scientific development at Advanced Cell Technologies, in Worcester, MA, and his collaborators then injected these stem cells into animals with various types of tissue damage: damaged retinas due to diabetes, experimentally induced heart attack, or lack of blood flow to the limb. The cells traveled to the injury site and repaired damaged blood vessels within 24 to 48 hours, according to findings published online in Nature Methods.

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“These cells have really been able to do a lot of novel things in terms of tissue injury and repair,” says Anthony Atala, director of the Institute for Regenerative Medicine, at Wake Forest University.

Experts say that the cells, which are derived from existing embryonic stem-cell lines, can be quickly grown in large quantities; in contrast, adult stem cells must be harvested from donors, a process that can take weeks. “What makes this study exciting is that the methods to culture … these cells do not require human or animal serum and can be scalable for large-volume therapeutic delivery,” says Raval. “In other words, this could become an ‘off the shelf’ product to treat human conditions where the blood supply is poor.”

Lanza has high hopes for the stem cells and has numerous collaborations in the works. He’s exploring the cells’ potential to prevent the progression of atherosclerosis, to treat stroke, and to be used as a starter ingredient to create “universal donor” blood cells for blood transfusions.

While exciting, much work remains to be done, cautions Raval. Among other challenges, he says, researchers still need to “determine the ability of these cells to avoid immune rejection.” And, he points out, anyone using cells derived from embryonic stem cells will have to “get past the political and ethical issues.”

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