Abstract
Purpose :
Multi-lamellar bodies (MLBs) are structures of lysosomal origin containing multiple concentric membrane layers 0.2 to 2 μm in size. MLBs are found in normal cells, such as lung alveoli where they form and secrete lipids. When found in cells that normally lack MLBs as in the inherited lipid storage disorders, Niemann–Pick, Fabry, and Tay–Sachs disease, they indicate faulty lipid metabolism. We are determining if MLBs are found in monkey retinal epithelium and whether they change with retinal location and age.
Methods :
Electron microscopy (EM) is used to identify and examine MLBs in the retinal epithelium of seven rhesus monkeys ranging from one to forty four years of age.
Results :
Eyes younger than 25 years of age rarely contain MLBs, but after that the number of MLBs increases steadily with age. They are found at all retinal locations from the macula to the periphery but tend to be more numerous in and around the macula. They are invariably located in the basal third of the epithelial cell often close to the basal membrane. MLBs can be distinguished from rod outer segment phagosomes by the circularity of their lamellae, by the presence of a fine granular deposit, usually centrally located, and by the absence of a surrounding membrane. A mature MLB and an early stage MLB are illustrated in Figure (bar, 0.5 µm).
Conclusions :
The increasing presence of MLBs in the aging retinal epithelium implies that these cells are developing faulty lipid metabolism. This suggests that aging RPE cells are suffering from lysosomal dysfunction. If so, cationic amphiphilic lysosomotropic drugs such as chloroquine and chlorpromazine may promote the aging process in retinal epithelium and be wise to avoid.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.