Purchase this article with an account.
Elizabeth Cone Cone-Kimball, Julie Schaub, Sarah Quillen, Mary Ellen Pease, Harry A Quigley; The Role of Aquaporins in the Optic Nerve Head Astrocytes in Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2004.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To study the distribution of aquaporin channels in the optic nerve head (ONH) region astrocytes & their response to IOP elevation in mice.
C57BL/6 mice (B6, N=20) & transgenic mice lacking aquaporin 4 (AQP4 null, N=16) were exposed to bead-induced IOP elevation for 3 days (3D GL) in one eye. Tissue was cryopreserved & sections immunolabeled with anti-aquaporins 1 (AQP1), 4 (AQP4), & 9 (AQP9). The α-dystroglycan (αDG) transmembrane complex, necessary for AQP channel formation, was immunolabeled. The mouse retina, pre-lamina, neck, unmyelinated ONH & myelinated ON were imaged by laser scanning microscopy (LSM) to identify normal aquaporin distribution & its changes after 3DGL.
LSM images of B6 mice found AQP4 was localized in retinal Muller cells & myelinated ON astrocytes, but not in prelaminar, neck or unmyelinated ONH (Fig 1). There was a comparable absence of AQP4 in the lamina cribrosa of normal pig & human ONH. AQP4 label outlined both astrocyte & blood vessel components. By contrast, αDG was present in all areas of the retina, ONH & ON, including regions devoid of AQP4 . After 3D GL in wild type B6 mice, AQP4 distribution was unchanged from normotensive eyes. AQP4 null mice were not different from wild type in baseline or degree of IOP elevation with bead injection (baseline- 10.6 ± 2.5 vs 10.7 ± 2.6, p=0.96 and 3D GL- 20.0 ± 3.1 vs 22.6 ± 5.7 mm Hg, p=0.24, respectively). AQP1 & 9 were not present in wild type mouse ONH region. In AQP4 null mice, AQP9 but not AQP1 was identified in the myelinated ON & photoreceptor layer (Fig 2). After 3D GL- B6 & AQP4 nulls mice label for AQP1 & 9 in the RGC layer & in the pre-laminar region. AQP4 null mice additionally labeled for AQP 1 in the umyelinated ONH. Results of 6 week IOP elevation in AQP4 null mice will be presented.
AQP4 is absent in the lamina cribrosa (all mammals studied) or its equivalent in mice, despite the presence of αDG complex throughout ONH astrocytic cell membranes. This regional phenotypic feature may affect small solute permeability & alter the glymphatic fluid pathway, either beneficially or detrimentally in response to increased IOP.
This is a 2020 ARVO Annual Meeting abstract.
Fig 1. AQP4(green) with minimal presence at the ONH(arrow), αDG(red) in mouse(A,B,C) & human(D).Scale Bar:50µm
Fig 2. Minimal presence of AQP1(green) in control tissue(A,C), increased after 3D GL(B,D). AQP9(red) was visible in AQP4 null mice(C), increased after 3D GL. Scale Bar:50µm
This PDF is available to Subscribers Only