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Guorong Li, Michael Lucio De Ieso, Sina Farsiu, Daniel Stamer; Effects of aging on conventional outflow anatomy and physiology in C57BL/6 mice. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4621.
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© ARVO (1962-2015); The Authors (2016-present)
Aging is a primary risk factor for glaucoma. The aim of this study is to examine age-related changes in conventional outflow morphology and function in mice
Young (3-6 month old) and aged (29-31 month-old) C57BL/6 (C57) mice were studied. Intraocular pressure (IOP) was measured using TonoLab Tonometer under light anesthesia. Outflow facility was determined using iPerfusion in enucleated eyes. Ultrastructure of outflow tissues was visualized by transmission electron microscopy. Outflow tissue behavior in living animals was visualized by SD-OCT using custom hardware and software.
Eyes were clearly larger in the aged mice compared to young mice (n=5 young mice; n=3 aged mice), however IOP levels were similar between young (21.16±0.63 mmHg, n=14 mice 28 eyes) and aged (21.18±0.83 mmHg, n=8 mice 16 eyes) mice. Surprisingly, outflow facility was significantly higher in the aged mice compared to young mice (3.57±0.3 vs. 1.9±0.24 nl/mmHg/min, n=7 mice/14 eyes vs. n=10 mice/18 eyes, p=0.0003). Interestingly, beta value (indication of anterior chamber deepening) was significantly lower in the aged mice (0.17±0.14 vs. 0.88±0.1, p=0.0013). Ultrastructural analysis of aged outflow tissues showed more pigment accumulation in the juxtacanalicular region of the TM and focal sequestration of pigment in the ciliary body. In response to 1% pilocarpine treatment, SC luminal dimensions in aged mice slowly increased (after 10 min) compared to young mice, where the SC lumen rapidly enlarged within 5 min of treatment (n=3, 30 month-old aged mice; n=4, 2 month-old young mice).
Aging in C57 mice modified aqueous humor outflow tissue appearance, function and behavior, but not IOP. While outflow tissues appear less compliant in aged mice, outflow tissues also appear to have adapted with time to maintain IOP homeostasis.
This is a 2020 ARVO Annual Meeting abstract.
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