INTRODUCTION AND AIM: Primary Open-Angle Glaucoma (POAG) is a leading cause of blindness worldwide. The pathology is characterized by elevated resistance to aqueous humor (AH) outflow which leads to an increased intra-ocular pressure (IOP). Elevated IOP is a risk factor for the development and progression of POAG because increased IOP can cause visual impairments or blindness by damaging the optic nerve. Previous studies indicated that Thrombospondin-1 (TSP-1) expression is higher in glaucomatous eyes and TSP1-deficient mice exhibit lowered IOP, suggesting TSP-1 plays a role in regulating IOP. A preliminary study in the Gong Lab has showed that TSP-1 decreased outflow facility in porcine eyes. This study aims to explore morphologic changes in the trabecular meshwork and episcleral veins (ESVs) in porcine eyes that were previously treated with either TSP-1 or phosphate-buffered saline containing 5.5 mM D-glucose (GPBS).
METHODS: Nine fresh porcine eyes were used in this study. All eyes were perfused with GPBS for 30 minutes to establish a stable baseline outflow facility. TSP-1 (0.8μg/mL) was then exchanged and perfused to one eye of each pair for 3 hours, while GPBS was exchanged and perfused to the contralateral eyes (N=5) as the control group. All perfusion was performed at a consistent pressure of 15mmHg, and the outflow facility was recorded. After perfusion, all eyes were perfused with a fluorescent tracer to label the outflow pattern, and then they were perfusion-fixed. The tissue of the anterior chamber angle of each eye was dissected and processed for light microscopy. One TSP-1 treated eye was excluded for morphologic study due to damage of the tissue. Three wedges from each eye were used for data collection and analysis. Semi-thin sections of each sample were cut and stained with 0.1% Toluidine Blue. The morphology of trabecular meshwork was evaluated. Numbers of episcleral veins (ESVs) were counted and their sizes (cross-sectional areas) were measured using ImageJ (NIH). This study was masked and decoded after all the measurements were done. Statistical significance between control and TSP-1 treated was analyzed.
RESULTS: Outflow facility was significantly decreased in the TSP-1 treated group compared to the control group (performed by other members in Gong lab). The average cross-sectional area of ESVs (797.0 ± 30.1 μm2) in the TSP-1 treated group was significantly smaller than the area of ESVs (1628.2 ± 191.3 μm2) in the control group (P<0.05). No significant morphologic differences were found in the TM of TSP-1 treated eyes when compared to the control.
CONCLUSIONS: TSP-1 reduced the size (cross-sectional area) of ESVs, which may contribute to decreased outflow. The findings of this study suggest that blocking TSP1- induced vasoconstriction in the ESVs could be a potential target to increase outflow facility or lower IOP for glaucoma treatment.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/47449 |
| Date | 03 November 2023 |
| Creators | Khan, Abid |
| Contributors | Gong, Haiyan |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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