The eyes are body parts that can’t be accused of being slackers. Eighty percent of what sighted individuals know comes from the information that the eyes receive. In turn, the eyes require an enormous amount of energy. Since they are big energy consumers and have little reserve energy, that may be a reason why eyes are vulnerable to diseases, like retinitis pigmentosa and age-related macular degeneration.
The next question is, are there biomarkers that spotlight eyes at risk for disease? Research at NEI is pointing to that possibility. Since it is the mitochondria that produces energy so a cell can function, Anand Swaroop, Ph.D., chief of NEI’s Neurobiology-Neurodegeneration and Repair Laboratory, studied the mitochondria’s function in the photoreceptors of mice both with and without retinal degenerative disease.
Swaroop’s lab measured the mitochondrial oxygen consumption rate. His lab was able to do this by mounting several retina samples on mesh and placing them on a microplate. Doing this allowed them to see how the retina works within the context of tissue. The research showed that the photoreceptor mitochondria operate from 70 to 80 percent of maximum capacity. Having the mitochondria work at such a high capacity suggests a high rate of metabolic stress. Photoreceptors would be vulnerable to damage if something comes along to disrupt the mitochondria’s work. This led researchers to believe that the oxygen consumption rate of the mitochondria may be a biomarker for retinal disease before overt symptoms occur.
There are also studies underway to develop ways to detect changes in the mitochondria. The lab of Raul Covian, Ph.D at the National Heart, Lung and Blood Institute, has been working on techniques to determine the structure and connectivity of mitochondria in living cells of the heart. While things have to be worked out in order to transfer this to the retina, in principle, these techniques can be applied to the study mitochondrial function in a working retina.
And there’s even more research when it comes to detecting retinal disease! Bruce Berkowitz, Ph.D., a professor of Anatomy and Cell Biology and of Ophthalmology, at Wayne State University in Detroit, developed a diagnostic imaging technique to see what is going on in a working retina. His research deals with oxidative stress and since it leads to degenerative eye disease, such as retinitis pigmentosa, the next step would be to do anti-oxidant treatments. The trouble is no one has been able objectively evaluate how well anti-oxidant work in vivo.
Well, Berkowitz’s lab was able to develop a noninvasive MRI-based method to measure oxidative stress in mice with diabetic retinopathy. What makes this method innovative is that it measures the free radical production of the outer retinal cells without a contrast agent or special equipment. This method allows for the new perspectives about oxidative stress and potential treatments.
Yes, the eyes are two of the hardest working organs in the body. Soon there will be new ways to keep them in working order.