A new study reveals important information about retinopathy prematurity that causes blindness in premature babies.
Researchers at Children's Hospital Medical Center (CHMC; Cincinnati, OH, USA) and the University of California, San Francisco (UCSF; USA) used mouse models to examine the light-response pathway. To do so, they raised mice in both darkness and in a regular day-night cycles, starting at late term pregnancy, to examine the outcomes on vascular progression of the eye. The scientists confirmed the purpose of the light response pathway by changing an opsin gene in mice known as Opn4 that creates melanopsin; in other words, stopping the initiation of the photo pigment.
The researchers found that the mice with mutated Opn4, as well as those that were raised in darkness, showed similar random expansion of hyaloid vessels and unusual retinal vascular progression, powered by the protein vascular endothelial growth factor (VEGFA). The researchers showed that these vascular anomalies are explained by a light-response pathway that suppresses retinal neuron number, limits hypoxia, and as a consequence, holds local expression of VEGFA in check to ward off indiscriminate vascular expansion.
According to the study, the light-response pathway must occur during pregnancy in order to achieve the precisely planned program that creates a normal eye; it is crucial for the right number of photons to reach the mother's body by late term pregnancy. The researchers also saw that photons of light trigger melanopsin inside the fetus—not the mother—to aid development of healthy blood vessel and retinal neurons in the eye. Another function of the light-response pathway is to prepare the eye for vision by regulating retinal neuron number and initiating a series of events that ultimately pattern the ocular blood vessels. The study was published on January 16, 2013, in Nature.
“This fundamentally changes our understanding of how the retina develops,” said study coauthor Richard Lang, PhD, of the division of pediatric ophthalmology. “We have identified a light-response pathway that controls the number of retinal neurons. This has downstream effects on developing vasculature in the eye and is important because several major eye diseases are vascular diseases.”
Children's Hospital Medical Center
University of California, San Francisco