Abstract
Abstract: :
Purpose: To compare the density profile of RPE cells and S-cones in the foveal region of normal and carotenoid-depleted monkeys. Methods: Rhesus monkeys were fed semi-synthetic diets without carotenoids for their whole life. Macular regions of the retinas were serially sectioned at 2 microns thickness after embedment in plastic. Nuclei were stained with DAPI and outer segments of S-cones were immunolabelled prior to imaging with a fluorescence microscope. Sets of images from 5 serial sections were aligned by computer software (SEM Align, Boston University) for reconstruction of the macular region. The numbers of RPE cell nuclei were counted along the vertical meridian. The outer segments of the S-cones were counted when there was closest connection between the inner segment and outer segment within the serial sections. Results: Normal RPE density profiles have a peak at the foveal center. The numbers of RPE cells decrease with eccentricity to 1.5 mm and remain relatively constant up to 2.5 mm from foveal center. Depleted animals have a dip of RPE density at the foveal center. Student's t-test was done on the differences between the RPE cell density at the center and the average between the immediately adjacent regions at 0.365mm. There was a significant difference between the RPE density profiles in normal and carotenoid-depleted monkeys (P<0.005). The density profile of S-cones had a peak at the center and the numbers of S-cones decreased rapidly with eccentricity. However, there was no difference in the S-cone density profile in normal and in carotenoid-depleted animals. Conclusion: Carotenoid-depleted monkeys have an abnormal density profile of RPE cells in the foveal region. Indeed, these animals had an increase in macular transmission defects seen in fluorescein angiograms, indicating a lack of integrity of the foveal RPE. However, there is no loss of S-cones in the foveal region. These results suggest that lutein and zeaxanthin are important for the development or maintenance of a normal density profile of RPE cells in the fovea.
Keywords: 337 carotenoids/carotenoid binding proteins • 462 macular pigment • 567 retinal pigment epithelium