Erythropoietin has so far been known to doctors as a hormone that boosts red-blood-cell production. Now, a mouse study led by Lois Smith, MD, PhD, an ophthalmologist at Children's Hospital Boston, shows it also keeps blood vessels alive and growing in the eye. The findings not only add a new function to the hormone, but also give doctors a reason to pause before prescribing it to patients with diseases affected by abnormal blood-vessel growth, such as retinopathy and cancer.
The study, published in the February issue of the Journal of Clinical Investigation (online January 24), also found that whether the hormone is a risk or benefit depends on the timing of administration.
Smith and first author Jing Chen, PhD, worked in mice with retinopathy, an eye disease that begins when healthy blood vessels nourishing the retina die. Numerous vessels then grow in, but they are deformed. Ultimately, the deformed vessels may pull the retina off the back of the eye, causing blindness.
The researchers measured erythropoietin produced in the retina as the disease progressed. Production was 3 to 10 times below normal during early-stage retinopathy, when healthy blood vessels died, and 12 to 33 times above normal during late-stage retinopathy, when deformed blood vessels grew into the retina. The researchers concluded that erythropoietin helps blood vessels survive and grow in the retina, with effects that may be healthy or harmful.
Next, the team examined whether giving erythropoietin could treat retinopathy. They injected erythropoietin into the bloodstream either early, as the mice lost healthy blood vessels, or later, when deformed blood vessels began to invade--then compared them with untreated mice.
Boosting erythropoietin early slowed the disease. The mice lost half as many healthy blood vessels, causing about 30 percent fewer deformed vessels to grow in. Raising erythropoietin levels later, when deformed
|Contact: Keri Stedman|
Children's Hospital Boston