This study investigated the morphologic differences of the giant vacuoles (GVs) in the inner wall endothelium of Schlemm’s canal (SC) in human eyes perfused at either 30 mmHg or 7 mmHg (physiologic pressure in enucleated eyes) using serial block-face scanning electron microscopy (SBF-SEM) paired with three-dimensional reconstruction software.
Two normal human eyes were perfused at 30 mmHg with fluorescent tracers to mark regions of active and inactive flow, followed by perfusion-fixation. Tissue wedges (n = 6) of trabecular meshwork including SC from high-, low-, and non-flow areas of each eye (determined by tracer distribution) were dissected and processed for SBF-SEM. Four types of GVs were identified: Type I GVs which lack both a basal opening and an Ipore; Type II GVs which have a basal opening but lack an I-pore; Type III GVs which have an I-pore but lack a basal opening; and Type IV GVs which possess both a basal opening and an I-pore. Types and spans of GVs were collected from the SBF-SEM images, and volumes of GVs from a random subset were measured using 3D reconstruction. Results were compared with findings from an earlier study conducted with two eyes perfused at 7 mmHg and prepared in the same manner (Soares, 2022). In total, 19,047 SBF-SEM images were analyzed between 7 mmHg (n = 9586) and 30 mmHg (n = 9461) using Reconstruct. Statistical analysis comparing data between the two pressures was performed using R.
There were more GVs found at 30 mmHg (n = 1541) when compared with 7 mmHg (n = 1312), and there were more Type IV GVs at 30 mmHg when compared with 7 mmHg. Type IV GVs occurred most frequently in high-flow areas at both pressures. GVs with I-pores were greater in size (both span and volume) than GVs without I-pores in all flow areas at both pressures. Type IV GVs were larger than Type II GVs which were larger than Type I GVs at both pressures. The span of GVs without I-pores was significantly greater at 7 mmHg. However, there was no significant difference between the volumes of GVs with or without I-pores between the two pressures.
The result that GVs with I-pores were larger in size than GVs without I-pores at all conditions appears to support the theory that GV size is an important contributing factor to I-pore formation. The differences in span but not volume of GVs without I-pores between two pressures suggest that GVs at high pressure may be more convex in shape and may protrude further into SC, a situation which could contribute to thinning of the cellular membrane of GVs. Finally, the result that more Type IV GVs were found in high-flow areas at both pressures implies that the changing percentage of Type IV GVs likely plays a role in regulating segmental flow. / 2025-02-26T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/48198 |
| Date | 26 February 2024 |
| Creators | Goodman, Isaac |
| Contributors | Gong, Haiyan |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0022 seconds