Stem Cells Yield More Advances

Researchers in the United States say they have been able to coax embryonic stem cells into yielding a plentiful supply of versatile cells that can repair damage to blood vessels.

The precursor cells, called hemangioblasts, develop into one of two directions – either cells for the blood system or for the endothelium, the vessel of lining.

The study was published in Nature Methods, a journal of the London-based Nature group.

Stem cells are versatile precursors of adult cells. Embryonic stem cells are exceptionally versatile, because they can develop into almost every tissue of the body.

Their great promise has prompted scientists to hope that embryonic stem cells can be the source for lab-dish tissue to replace cells that are damaged by disease.

The strategy, led by a team at Advanced Cell Technology (ACT), a Massachusetts biotech company, entails culturing human embryonic stem cells in chemicals in two phases, so that the stem cells are “differentiated” into tiny clusters of hemangioblasts.

The hemangioblasts have been successfully tested on lab rodents with retinas, heart muscles and hind limbs with blood-vessel damage.

A long road of evaluation for safety and effectiveness lies ahead before the innovation enters the public domain, but the scientists say the goal of embryonic stem-cell derived hemangioblasts is alluring.

“An injection of these cells might potentially be able to prevent a patient from having a leg amputated or a patient from dying after a heart attack,” said senior author Robert Lanza, vice president of research and scientific development at ACT.

Lanza said the company intended to file a request to the US Food and Drug Administration by the end of 2008, seeking permission to conduct small-scale trials on human volunteers.

“We still have preclinical studies underway, and are hoping to make a final decision as to the specific indication in the next month or so,” Lanza said.

The trial focus would probably be on sight-afflicting conditions caused by blood vessel damage in the retina, he said.

“Diabetic retinopathy would be a good candidate (for the trials), although there are several other, more devastating indications that we’re also considering, such as branch retinal vein occlusion, for which there is currently no treatment.”

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