Abstract
Purpose :
This study aimed to determine whether TSP1 reduces outflow facility in ex vivo perfused porcine eyes and what hydrodynamic and morphologic changes may be responsible for this reduction.
Methods :
Fresh porcine eyes were obtained from local abattoirs within 6 hours of death. All eyes (N= 14 pairs) were perfused with Dulbecco’s phosphate-buffered saline containing 5.5 mM of D-glucose (GPBS) at 15 mmHg for 30 minutes to establish a stable baseline outflow facility. One eye of each pair was then exchanged and perfused with TSP1 (0.8 μg/mL) for 3 hours at 15mmHg, while the contralateral eye of each pair was exchanged and perfused with GPBS as control. Outflow facility was recorded. All eyes were then perfused with fluorescent tracer to label the outflow pattern, followed by perfusion-fixation. The anterior segment of each fixed eye was dissected into 16 radial segments and the images of frontal sections of the the trabecular meshwork (TM) and aqueous plexus (AP) were captured by a confocal microscope after nuclear counter-staining. The percentage effective filtration length (PEFL = ΣFL/ΣTLx100%) along the inner wall of APs in each eye was calculated. The sections were further processed for light microscopy. The morphology of the TM was evaluated and the cross-sectional areas of the episcleral veins (ESV) and intrascleral veins (ISV) (N=4 pairs) were measured using ImageJ. The measured data was normalized following the formula where the normalized area=vein area of TSP1 treated eye/vein area of the paired control eye, then statistical analysis was performed between the two groups.
Results :
Outflow facility was significantly lower after perfusion with TSP1 for 3 hours when compared to control eyes (N=14 pairs, p < 0.0001). No significant difference was observed in the PEFL along the inner wall of APs (N=7 pairs, p > 0.05) and in the general morphology of the TM between TSP-1-treated and control groups (N=4 pairs). However, the normalized areas of ESVs and ISVs of TSP-1-perfused eyes were significantly smaller than those in the control eyes by 50 ± 7% (p < 0.01) and 29 ± 8% (p < 0.05), respectively.
Conclusions :
Decreased outflow facility by TSP1 is associated with reducing the size of ESVs and ISVs. Our results highlight the potential for regulating IOP by targeting the size of ISVs and ESVs in the distal outflow pathway.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.