Insulin-like growth factor binding protein-3 (IGFBP-3) seems to take a lead role in healthy eyesight, according to researchers at the University of Florida (UF), Harvard Medical School, and the University of Goteborg. The findings are described in separate papers that will be published in the June 19 issue of Proceedings of the National Academy of Sciences.
“We’ve identified a protein that is part of the body’s natural defenses in oxygen-deprived conditions,” says Maria B. Grant, M.D., a professor of pharmacology and therapeutics at UF’s College of Medicine. “When babies are born before levels of this protein are normal, blood vessels spread abnormally throughout the retina.”
Insulin-like growth factor binding protein-3 (IGFBP-3), was thought to exist exclusively to regulate insulin-like growth factor-1, a molecular growth factor that is necessary for the development of nerve, muscle, bone, liver, kidney, lung, eye, and other body tissues. However, in studies of mice and of human cells in cultures, scientists from UF found that IGFBP-3 activates stem cells and other reparative cells of the bone marrow and the lining of blood vessels.
At UF, researchers infused IGFBP-3 into one eye of each of nine mice before placing the animals into a high-oxygen chamber for five days. When scientists compared vascular growth within the retinas, they found blood vessels were closer to normal in eyes treated with IGFBP-3. When they repeated the experiment in 18 mice treated with bone marrow stem cells expressing IGFBP-3, they found the treated eyes developed normally.
Investigators from the Harvard Medical School and the University of Goteborg in Sweden arrived at essentially the same conclusion. In addition to studies in mice, Harvard research collaborators in Sweden examined infants with retinopathy of prematurity in a prospective clinical study and found that the IGFBP-3 levels were lower than those of healthy infants.
The team is currently conducting a Phase I study to evaluate the use of IGFBP-3 in combination with IGF-1 on prevention of retinopathy in premature infants, based on the clinical findings in their study.