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Stem Cells from Bone Marrow May Help Mend Eyes
Mon Jul 29, 2002
By Merritt McKinney

NEW YORK (Reuters Health) - New research in mice suggests stem cells collected from bone marrow could be used to treat several sight-robbing eye diseases that involve abnormal blood vessel growth.

When injected into the eyes of newborn mice, the stem cells grew into blood vessels, and may have prevented the loss of vision that normally occurs in this type of mouse.

The results of the animal experiments are encouraging, but there is a long way to go before human studies can start, since it is uncertain whether the same cells exist in people, according to the study's lead author, Dr. Martin Friedlander, of The Scripps Research Institute in La Jolla, California.

"If it works, it would be great," he told Reuters Health in an interview.

Several common eye diseases involve abnormalities in the blood vessels in the retina, the light-sensitive layer located on the inner surface of the back of the eye.

Diabetic retinopathy, a cause of blindness in diabetics, and age-related macular degeneration, the number one cause of blindness in the elderly, are both characterized by the growth of too many blood vessels. An inherited condition, retinitis pigmentosa, can cause blindness because blood vessels in the retina degenerate.

Friedlander and his colleagues studied a type of stem cell commonly found in bone marrow called a hematopoietic stem cell. Such stem cells have the capability to form the cells of the blood and immune system. However, there is also a subset of cells, called endothelial precursor cells, or EPCs, that form blood vessels.

According to the study in an advance online publication of the September issue of Nature Medicine, Friedlander and his colleagues report that hematopoietic stem cells that contain lots of EPCs can be used to promote and inhibit the growth of blood vessels in the retina.

The researchers injected EPC-enriched hematopoietic cells into the eyes of baby mice that had a disease similar to retinitis pigmentosa. The cells interacted with a second type of cell known as an astrocyte and "completely rescued" the at-risk blood vessels, Friedlander said. The mice went on to develop completely normal blood vessels in the retina, he said.

The California researcher added that the treatment also seemed to rescue some photoreceptors, structures that are destroyed in retinitis pigmentosa. Though the results raise the possibility of using bone marrow cells to treat retinitis pigmentosa in people, Friedlander said that it is "still to be seen" whether vision is restored in the mice.

The bone marrow cells also seem promising for the treatment of eye diseases marked by too many blood vessels, according to Friedlander. The researchers genetically engineered the EPCs to produce a powerful substance that prevents blood vessel growth, and were able to interfere with the formation of blood vessels in the retina.

The cells may also help in treating diabetic retinopathy, a condition in which new blood vessels grow because the eye is not getting enough oxygen. Unfortunately, these new blood vessels leak and otherwise wreak havoc on the eye.

The traditional approach, Friedlander said, has been to develop ways to stop new blood vessels from forming. But this only treats the symptoms and does not solve the problem of inadequate oxygen for the eyes.

Friedlander speculated that it might be possible to stop diabetic eye disease by injecting bone marrow cells into the eyes of diabetics in the early stages of the disease. The stem cells would be expected to encourage the growth of normal blood vessels to supply oxygen but would prevent too many vessels from forming. The researcher cautioned, however, that this approach has not even been tested in mice, much less in people.

The study was funded by the National Eye Institute and several other government and not-for-profit sources.

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Date last modified August 17, 2002