Abstract
Purpose :
The basal surface of the retinal pigment epithelium (RPE) is folded into a complex basal labyrinth. The three dimensional structure of epithelial basal surfaces is thought to affect the transport of solutes and water across them. The structure of the RPE basal labyrinth is perturbed as a result of aging, smoking and in several diseases. The aim of this study was to analyse and define the structural organisation of the basal labyrinth of RPE cells and determine how that structure responds to changes in local osmotic pressure, age and disease.
Methods :
We used conventional transmission and serial block-face scanning electron microscopy to examine the structure of the basal labyrinth in eyes from wild type mice and a choroideremia mouse model of different ages with and without osmotic shock before fixation.
Results :
We identified structurally distinct zones (stacked, ribbon-like and cisternal regions) within the RPE basal labyrinth. Spacing between the basal infoldings was affected by subtle changes in the osmotic milieu whilst osmotic shock induced dramatic remodelling of the infoldings. Quantitative analysis demonstrated a loss of structure within the basal labyrinth that increased with age and occurred prematurely in a model of choroideremia. A junctional complex crosslinks closely opposed basal infoldings while glycosaminoglycans link more distantly aligned infoldings.
Conclusions :
The basal labyrinth is more structured than previously considered, responds to osmotic challenge and is maintained by a number of cross-linking elements. Dramatic and quantifiable changes in architecture of the basal labyrinth occur with age and in choroideremia, which likely compromise trans-epithelial transport.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.