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Haiyan Gong, Adrian Cann, Ruiyi Ren; Characterization of the Mouse Aqueous Outflow Pathway Using Serial Sectioning and 3D Reconstruction. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5650.
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© ARVO (1962-2015); The Authors (2016-present)
The mouse eye is a useful model in glaucoma research due to its low cost, potential for genetic manipulation, and anatomical similarity to humans. However, the anatomy of the aqueous outflow pathway of mouse eye has not been carefully characterized. The aim of this study was to characterize the entire trabecular meshwork outflow pathway in mouse eyes using serial sectioning and three-dimensional reconstruction.
Eyes of C57BL/6 mice (N=9) were fixed with modified Karnovsky’s fixative, processed and embedded in epon-araldite. One-micron, frontal and radial, serial sections were cut, stained with toluidine blue and scanned on a whole slide scanner. Images of serial sections were registered using Fiji image processing software. Collector channels (CCs) were counted and their locations were recorded in four eyes by scrolling through the aligned image sequence. Width of the CC ostia and dimensions of Schlemm’s canal (SC) were measured.
In mouse eyes, 34-45 CCs were found with uneven circumferential distribution, draining aqueous humor from SC into a continuous venous network in the sclera. CCs varied greatly in morphology. Two types of connection between SC and episcleral veins were identified: 1). Perpendicular CCs formed a right angle with SC and the scleral veins. This type of CC tended to have a greater diameter. 2). The second type of CC formed an oblique angle with SC. These CCs traveled parallel to SC for some distance before joining the episcleral vein. Compared to humans, mice possess a larger SC, relative to the size of their eye, with slightly different proportionalities between the width (anterior to posterior distance, 122±42.1µm), height (distance between inner and outer wall, 14.3±11.0µm), and perimeter length (7.9±0.2mm) of SC.
Mice and humans have a similar aqueous outflow system, but the mouse venous network within the sclera is simpler than in humans. This study documents the normal trabecular outflow pathway of mouse eyes in great detail, providing an anatomical basis for further comparison of the changes in ocular hypertensive mouse models and for validation of other new imaging techniques.
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