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Bloomberg.com: News: "Blood Vessels Made From Human Adult Stem Cells Grown in Mice

By Rob Waters

Blood Vessels Made From Human Adult Stem Cells Grown in Mice

By Rob Waters

July 18 (Bloomberg) -- Stem cells drawn from the blood system of adult humans or the umbilical cord blood of newborns, injected into mice, formed viable vessels that may one day deliver oxygen-rich blood to damaged organs, researchers said.

After one week, the cells spontaneously connected to one another and to the existing blood vessels of the rodents to form extensive networks that continued to transport blood over the next three weeks. The findings from Harvard Medical School were published in the journal Circulation.

If the process can be proven safe and replicated in people, it could provide a way to repair blood-starved regions of organs that have been damaged by heart attacks or other conditions that impair circulation. Unlike other experiments that have coaxed adult cells to perform new functions, the Harvard team didn't perform any genetic manipulation, said Joyce Bischoff, an associate professor at Harvard and Children's Hospital Boston.

``It's kind of a self-assembly process; they do the job on their own,'' Bischoff said in a telephone interview today. ``We mix them together and they talk to each other and give directions on how to form a blood vessel.''

The team drew samples from blood and bone marrow, isolated the stem cells within each, then mixed them with a gel material that is liquid when cold and solidifies at body temperature. The gel, after firming, formed scaffolds the cells could grow on. The materials were combined into a single suspension and injected into mice, Bischoff said.

The cells derived from blood ``form the lining of the blood vessel'' known as the endothelium and the bone marrow cells ``wrap around the endothelial cells to form the smooth muscle layer,'' Bischoff said.

Goal: Two-Day Vessels

Because damaged heart tissue or festering wounds need blood and oxygen quickly to heal, ``our goal is to speed it up to form blood vessels within one or two days,'' Bischoff said.

The advance could propel the emerging field of tissue engineering, which seeks to use stem cells and scaffolds to build replacement tissues and organs for people with various conditions. One closely held company, Tengion, based in East Norriton, Pennsylvania, is testing synthesized bladders in human trials and developing ways to create blood vessels and kidneys.

Before the method can be tested in humans, researchers will need to show that the cells they've isolated and expanded are pure and uncontaminated by other cell types. The technique will need to be proven safe in many more animals and the process will need to be done in a completely sterile environment that's certified by regulators.

``Science moves very slowly,'' Bischoff said.

To contact the reporter on this story: Rob Waters in San Francisco at rwaters5@bloomberg.net.
Last Updated: July 18, 2008 16:00 EDT