September 29, 1994
Media Contact:Marc Kusinitz
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'The next step will be to use this animal model to test possible treatments for vision loss..."
A researcher at Johns Hopkins has shown that a type of genetically engineered mouse used to study sickle cell anemia also is a good model for the complications that occur in two blinding diseases that affect millions of Americans, and for studying drugs to treat them.
The mouse shows the same changes in blood vessels of the light-sensitive retina that occur in people with sickle cell anemia and macular degeneration, a common cause of vision loss among the elderly, according to Gerard A. Lutty, Ph.D., assistant professor at the Wilmer Eye Institute. The results of his study are published in the August issue of the American Journal of Pathology.
Using genetic engineering technology developed by researchers at Columbia University, a group at Albert Einstein College of Medicine in collaboration with the Columbia group raised mice with human genes that caused the same type of damage in the spleen, kidney and lungs that occurs in humans with sickle cell anemia. Alerted by reports of these findings, Lutty obtained some of the mice from Albert Einstein and checked their retinas to see if they also showed signs of eye damage similar to that seen in humans with sickle cell anemia.
Sickle cell disease blocks blood vessels nourishing the eye, setting off a chain reaction that disrupt blood flow and injures the retina. The retina becomes starved for oxygen and energy, so new blood vessels grow into the retina-a proliferative process called neovascularization. Neovascularization is one of the stages in proliferative sickle cell retinopathy, Lutty says.
These new blood vessels often grow unchecked into the vitreous, the fluid that fills the eyeball. The new growth can strain the retina so that it detaches from the wall of the eye, resulting in blindness.
In addition, the mice have occlusions, or blockage, of capillaries in the choroid, a thin sheet of blood vessels behind the retina. They also display abnormal growth of blood vessels in the choroid, according to Lutty. These are hallmarks of macular degeneration.
"We've been able to show that mice from the transgenic mouse model for sickle cell disease are the first animals we know of to develop both proliferative retinopathy, an abnormal overgrowth of blood vessels in the retina, and new blood vessel growth from the choroid," says Lutty. "The next step will be to use this animal model to test possible drug treatments for occlusions by sickle red blood cells and for vision loss, such as drugs that inhibit neovascularization."
Other authors of the paper were Agathe Pachnis, Ph.D. and Frank Costantini, M.D. (Columbia University, New York, N.Y.) and Mary E. Fabry, Ph.D. and Ronald L. Nagel, M.D. (The Albert Einstein College of Medicine, New York, N.Y.).
The research was supported by Research to Prevent Blindness and the National Heart Lung and Blood Institute.