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Z. Lu, Y. Zhang, T. F. Freddo, H. Gong; Hydrodynamic and Morphological Characteristics Between Washout Effect and Y27632 Treatment in Monkey Eyes. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4848.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the effects of Y-27632 (Y27) and washout on outflow facility (C), on the hydrodynamic patterns of outflow, and the morphology of the inner wall (IW) and juxtacanalicular tissue (JCT) in monkey eyes.
Twelve fresh enucleated monkey eyes were perfused at 15 mmHg with Dulbecco's PBS containing 5.5 mM glucose (GPBS) to establish a baseline C. Four eyes were perfused for a short-duration (30 min) as a control, 4 eyes for a long-duration (180 min) to induce washout, and 4 eyes with GPBS+50 µM Y27 for 30 min. All eyes were perfused with fluorescent microspheres (0.5µm; 0.002%) to label the hydrodynamic patterns of outflow before perfusion-fixation. Confocal images of frontal sections were taken along the (IW) of Schlemm’s canal (SC). The total length (TL) and the tracer-decorated length (L) of the IW were measured, and the average percent effective filtration length (PEFL=L/TL) was calculated. Sections with SC were examined by light and electron microscopy. The TL of IW and the length exhibiting separation (SL) in the JCT were measured. The average percent separation length (PLS= SL/TL) was calculated.
C increased 150% [0.58±0.20 vs 1.46±0.70 µl/min/mmHg, p<0.01] above baseline after long-duration, and 115% [0.53±0.13 vs 1.12±0.22 µl/min/mmHg, p=0.004] after Y27 treatment, but remained unchanged after short-duration perfusion (0.44±0.16 vs 0.62±0.21 µl/min/mmHg, p=0.46). A more uniform tracer distribution was seen in the eyes with long-duration perfusion and Y27 treatment than with short-duration perfusion. The average PEFL in both long-duration (83.4±2.1%) and Y27 treated eyes (82.5±1.6%) was 3.4-fold larger than in short-duration eyes (24.2±4.2%, P<0.001). The JCT appeared distended in long-duration perfusion and Y27 treated eyes compared to short-duration perfusion eyes. The connections between JCT cells and between JCT cell and matrix were lost in distended regions. The PLS in the JCT was 2.3-fold larger in long-duration perfusion (77.4±3.3%) and 2.2-fold larger in Y27 treated eyes (75.2±5.3%) than in short-duration perfusion eyes (33.5±5.3%, p=0.001).
Increase in C after washout and Y27 treatment coincides with an increase in available area for aqueous outflow and greater separation in the JCT. These hydrodynamic changes are likely driven by morphologic changes associated with a decrease in cell-cell and cell-matrix connections in the JCT. Y27 and washout may share a similar mechanism by redistributing aqueous outflow through a larger area in the JCT.
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