Purchase this article with an account.
Laiyin Ma, Elliot D K Cha, Haiyan Gong; Sphingosine-1-Phosphate (S1P) Decreases Outflow Facility by Reducing Effective Filtration Area for Aqueous Humor Outflow in Bovine Eyes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2908.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
The cause of decreased aqueous outflow facility (C) in the conventional outflow pathway of primary open-angle glaucoma remains unknown. Sphingosine-1-phosphate (S1P), a lysophospholipid, was previously reported to decrease C in perfused porcine and human eyes. However, the morphological correlations to this decrease remain unclear. We hypothesize that decreased C by S1P is due to a decrease in effective filtration area (EFA), which results from increased connectivity between the juxtacanalicular connective tissue (JCT) and inner wall (IW) of aqueous plexus (AP) in bovine eyes.
Freshly enucleated bovine eyes were perfused at 15mmHg to establish a stable baseline C. One eye of each pair (N=7) was then perfused with 5μM S1P and the contralateral eye with GPBS for 2 hours. All eyes were perfused with a fixed volume of fluorescent microspheres (0.002%, 0.5μm) to trace the outflow pattern. Eyes were perfusion-fixed. Trabecular meshwork of eyes (N=4) were frontally sectioned for confocal microscopy. Total length (TL) and filtration length (FL) of AP were measured to calculate percent effective filtration length (PEFL=FL/TL). The tissue was further processed for light microscopy. JCT/IW separation (SL) was measured and calculated for percent separation length (PSL=SL/TL). Two-tailed Student’s t-test was used for statistical analysis.
C was significantly increased in both S1P (p=0.04) and control (p=0.002) groups compared to baseline. Although both groups exhibited washout effect, C was significantly lower in the S1P group (1.93±0.44μl/min/mmHg) compared to the control group (3.60±1.07μl/min/mmHg, p=0.005). A significantly lesser amount of tracer was observed along the JCT/IW region of S1P treated eyes, corresponding to a 62.63% decrease in PEFL compared to controls (p=0.001). A significant positive correlation was found between PEFL and the percent increase in C. Interestingly, no significant difference was found in PSL between the control (25.64±6.32%) and S1P (22.57±3.34%) groups.
Our results are consistent with our hypothesis that decreased C by S1P is due to a significant decrease in EFA in bovine eyes. However, the morphologic correlation was not related to increased connectivity between the JCT and IW. Further morphologic examination will be needed to understand what structural changes account for decreased EFA by S1P.
This PDF is available to Subscribers Only