Abstract
Purpose :
Glycocalyx is a hair-like structure covering the endothelium of the aqueous outflow pathway. While outflow is segmental around the circumference of the globe, variations in glycocalyx morphology in different flow regions are still unclear. This study investigated morphological differences of glycocalyx in different flow regions along the trabecular outflow pathway in bovine eyes.
Methods :
We perfused enucleated bovine eyes (n=8) with fluorescein to identify high- and low-flow regions of the trabecular outflow pathway, then fixative with Alcian Blue 8GX to label glycocalyx. Radial wedges of high- and low-flow regions of the anterior chamber angles were processed for transmission electron microscopy. The coverage and thickness of glycocalyx were measured with ImageJ, and the percentage of glycocalyx-filled pores was compared in high- and low-flow regions. The proportion of giant vacuoles (GVs) with glycocalyx lining the inner membrane was compared between GVs with and without intracellular pores (I-pores).
Results :
Glycocalyx thickness in epi-scleral veins (ESVs) was significantly greater than that in the trabecular meshwork beams (TMBs) (p<0.001), aqueous plexus (AP) (p<0.01) and collector channels (p<0.01) in high-flow regions. In low-flow regions, glycocalyx thickness was significantly greater in the ESVs than in the TMBs (p<0.05). No significant differences were found in glycocalyx coverage and thickness between flow regions. There were more unfilled than filled pores in both flow regions. Glycocalyx was observed lining the opening of B-pores and the inside the cellular membrane of 93 % GVs with I-pores. There was a significant association between coverage of glycocalyx along the inner cellular membrane of GVs and GVs with I-pores (X2=58.192, p<0.001; chi-square test).
Conclusions :
Glycocalyx thickness in ESVs was significantly greater than that in the TMBs in both flow regions. Our results suggest that variations in shear stress might play a role in determining glycocalyx morphology along the outflow pathway. Glycocalyx covered the inner cellular membrane of GVs mainly in GVs with I-pores and covered B-pores in the inner wall of the AP, suggesting a relationship between flow and glycocalyx synthesis.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.