Journal
INVESTIGATIVE OPHTHALMOLOGY & VISUAL SCIENCE
Volume 60, Issue 5, Pages 1630-1643Publisher
ASSOC RESEARCH VISION OPHTHALMOLOGY INC
DOI: 10.1167/iovs.18-26011
Keywords
Schlemm's canal endothelium; cellular connectivity; giant vacuoles; pores; serial block-face scanning electron microscopy; 3D electron microscopy
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Funding
- BrightFocus Foundation [2016099]
- NIH/NEI [EY022634, EY019696]
- Massachusetts Lions Eye Research Fund
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PURPOSE. We investigated whether cellular connectivity between Schlemm's canal (SC) inner wall (IW) endothelium, and juxtacanalicular connective tissue (JCT), and between IW endothelial cells, plays a role in giant vacuole (GV) and pore formation by comparing perfusion- and immersion-fixed eyes. METHODS. Normal human donor eyes (n = 4) were either immersion-fixed (0 mm Hg) or perfusion- fixed (15 mm Hg). Trabecular meshwork near SC was imaged using serial block-face scanning electron microscopy. A total of 12 IW cells from each group were 3D-reconstructed from similar to 7040 electron micrographs and compared. In each cell, connections between IW cells and JCT cells/matrix were quantified; IW/IW connectivity was measured by cell border overlap length. GV volume, density, shape, and intracellular and paracellular pores were analyzed. RESULTS. The mean number of IW/JCT cell-cell connections per cell significantly decreased (P < 0.01) while the summed GV volume per cell significantly increased (P < 0.01) in perfusion-fixed eyes compared to immersion-fixed eyes. Intracellular pores were observed in 14.6% of GVs in perfusion-fixed eyes and not observed in immersion-fixed eyes. The mean IW/IW overlap length per cell decreased (P < 0.01), and paracellular pores were found only in regions where IW/IW connectivity was minimal (overlap length = 0 mu m) in perfusion-fixed eyes and not observed in immersion-fixed eyes. CONCLUSIONS. Our data suggest that changes in IW/JCT connectivity may be an important factor in the formation of larger GVs, and decreased IW/IW connectivity may promote paracellular pore formation. Targeting the IW/JCT and IW/IW connectivity may therefore be a potential strategy to regulate outflow resistance and IOP.
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