WASHINGTON Stem cells made from human embryos can home in on damaged eyes, hearts and arteries of mice and rats, and appear to start repairs, a U.S. company said on Monday.
Massachusetts-based Advanced Cell Technology said it had devised a straightforward way to make blood vessel precursor cells out of the stem cells and plans to test them in humans.
"We figured out how to produce literally billions of so-called 'hemangioblasts' -- the mythical cell in the embryo that gives rise to our entire blood and immune system as well as to the blood vessels in our body," Dr. Robert Lanza, vice president of research and scientific development at ACT, said in an e-mail.
"We've also tested these cells in animals for the first time, and it turns out that they have incredible reparative potential."
Embryonic stem cells are the ultimate master cell of the body, giving rise to all of the tissues and organs. The use of human embryonic stem cells is controversial because many people oppose destroying the embryo.
The U.S. Congress has passed several bills that would expand federal funding of human embryonic stem cell research but President George W. Bush vetoed one and has said he will veto any more.
However, companies working with private funding, such as the over-the-counter listed ACT, may do as they please.
Working with embryonic stem cells is not easy. For medical uses, researchers would like to partly differentiate them -- start them down the road toward becoming a specific cell or tissue type.
Another roadblock is that many of the current batches, or lines, of stem cells must be grown in a serum culture taken from animal blood. This can contaminate them with viruses.
Writing in the journal Nature Methods, Lanza's team said they found a way to grow and differentiate human embryonic stem cells without using culture.
They directed the stem cells into becoming what they believe are hemangioblasts, the blood vessel precursor cells, although other teams will have to replicate this for it to be accepted.
"When injected into the bloodstream, they homed to the other side of the body and repaired damaged vasculature within 24 to 48 hours," Lanza said.
"For example, we injected the cells into mice with damaged retinas due to diabetes or other eye injury. The cells (labeled green) migrated to the injured eye, and incorporated and lit-up the entire damaged vasculature. The cells are really smart, and amazingly, knew not to do anything in uninjured eyes."
The researchers killed the mice to check the cells' progress, so they do not know the long-term effects.
"The cells also showed remarkable reparative capacity in animals with heart attacks and ischemic (blocked by a blood clot) limbs. The cells reduce the mortality rate by 50 percent after a massive heart attack," Lanza said.
"If the same thing works in humans (these would be the same human cells we would probably use), you might be able to prevent patients from having legs and other limbs amputated by simply injecting some cells."
William Caldwell, chairman and chief executive officer of Advanced Cell Technology, said the company wanted to test the cells in people and had asked the Food and Drug Administration for permission to do so by the end of next year.
"We also have studies underway indicating that the cells can also considerably accelerate wound healing, repair lung damage, and can even generate unlimited amounts of red blood cells for transfusion," Lanza said.