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A role for aquaporin-4 during induction of form deprivation myopia in chick.

Goodyear MJ, Junghans BM, Giummarra L, Murphy MJ, Crewther DP, Crewther SG - Mol. Vis. (2008)

Bottom Line: Aquaporins (AQP) form a family of specialized water channels known to transport water across cell membranes and reduce osmotic gradients.The control eyes showed relatively constant levels of AQP4 expression until day 5 after which the level appeared to decrease.By comparison, positive AQP4 immunoreactivity in the nerve fiber layer increased significantly over the first 48 h in form-deprived eyes and in fellow eyes and then decreased over the next 48 h but not to the level of expression in the normal untreated eyes.

View Article: PubMed Central - PubMed

Affiliation: School of Psychological Science, La Trobe University, Melbourne, Australia.

ABSTRACT

Purpose: Aquaporins (AQP) form a family of specialized water channels known to transport water across cell membranes and reduce osmotic gradients. The isoform AQP4 is highly expressed in the astroglia of the brain and Müller cells in the retina. In the brain, AQP4 play a role in the control of cerebral edema by shunting excess fluid into blood vessels and by upregulating during conditions of hyperosmolarity. Thus, on the basis of the hyperosmolarity seen across the retina and choroid of hatchling chickens made myopic by form deprivation (FD), we predicted an upregulation of retinal AQP4 expression during induction of myopia.

Methods: Two-day-old hatchling chicks were monocularly form-deprived for 48, 72, or 96 h, and then after biometric assessment, the eyes of these animals and the normal controls of the same age were enucleated. Retinal tissue was prepared either for western blot analysis to show the presence of the AQP4 protein in the chick retina or for immunolocalization using polyclonal AQP4 antibodies to determine regional distribution and intensity of labeling during the induction of form deprivation myopia (FDM).

Results: As expected, ultrasonography demonstrated that all post hatchling eyes showed rapid elongation with occluded eyes elongating faster than fellow eyes or normal controls and becoming progressively more myopic with the duration of visual deprivation. Western blot analyses revealed an approximately 30 kDa band immunoreactive for AQP4 protein and confirmed the presence of AQP4 in chicks. Immunohistochemical staining showed the greatest positive immunoreactivity for antibodies to AQP4 in the inner retina along the vitreoretinal interface, nerve fiber layer, ganglion cell layer, and inner plexiform layer in all animals. The control eyes showed relatively constant levels of AQP4 expression until day 5 after which the level appeared to decrease. By comparison, positive AQP4 immunoreactivity in the nerve fiber layer increased significantly over the first 48 h in form-deprived eyes and in fellow eyes and then decreased over the next 48 h but not to the level of expression in the normal untreated eyes.

Conclusions: This is the first study to demonstrate the presence of AQP4 protein in the chick retina and to associate AQP4 expression in the inner retina with the initiation of form deprivation and the period of fastest axial elongation. This increased expression of AQP4 channels near the vitread border during the time of rapid growth suggests a role for AQP4 as a conduit for movement of retinal fluid into the vitreous in form-deprived chicks.

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AQP4 labeling of the chick retina. A confocal micrograph of a transverse section of the retina from a form-deprived eye after 72 h of occluder wear is shown. There is strong labeling in the nerve fiber layer (NFL), ganglion cell (GC) layer, and inner plexiform layer (IPL) but very weak labeling in the inner nuclear layer (INL). Note the branching brush-like appearance of the pattern of AQP4 expression and also the appearance of several sublaminae in the IPL, which is similar to the previously described morphology of the Müller cell [51]. Bar is 20 µm.
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f3: AQP4 labeling of the chick retina. A confocal micrograph of a transverse section of the retina from a form-deprived eye after 72 h of occluder wear is shown. There is strong labeling in the nerve fiber layer (NFL), ganglion cell (GC) layer, and inner plexiform layer (IPL) but very weak labeling in the inner nuclear layer (INL). Note the branching brush-like appearance of the pattern of AQP4 expression and also the appearance of several sublaminae in the IPL, which is similar to the previously described morphology of the Müller cell [51]. Bar is 20 µm.

Mentions: AQP4 expression showed a regionalized distribution across the transverse retina in all eyes. The most intense AQP4 immunoreactivity was always exhibited in the innermost portions of the retina along the vitreoretinal interface, the NFL, ganglion cell (GC) layer, and the IPL (Figure 1A). The appearance of the many interweaving branching processes matched that of the morphology of the chick Müller cell within the IPL and GC (see Figure 3) as first illustrated in the chick by Cajal Golgi staining (reproduced subsequently in Dreher et al. [51] using 4F3 and 4H11 immunocytochemical labeling. This study also confirmed the appearance of the many interweaving branching processes by the overlay of the immunolabeling image on the differential interference contrast image. The strongly labeled filamentous processes appeared as tightly wrapped bundles around individual ganglion cells (Figure 1A). Several sublaminae outlined by the pattern of AQP4 labeling could be seen within the IPL.


A role for aquaporin-4 during induction of form deprivation myopia in chick.

Goodyear MJ, Junghans BM, Giummarra L, Murphy MJ, Crewther DP, Crewther SG - Mol. Vis. (2008)

AQP4 labeling of the chick retina. A confocal micrograph of a transverse section of the retina from a form-deprived eye after 72 h of occluder wear is shown. There is strong labeling in the nerve fiber layer (NFL), ganglion cell (GC) layer, and inner plexiform layer (IPL) but very weak labeling in the inner nuclear layer (INL). Note the branching brush-like appearance of the pattern of AQP4 expression and also the appearance of several sublaminae in the IPL, which is similar to the previously described morphology of the Müller cell [51]. Bar is 20 µm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2254964&req=5

f3: AQP4 labeling of the chick retina. A confocal micrograph of a transverse section of the retina from a form-deprived eye after 72 h of occluder wear is shown. There is strong labeling in the nerve fiber layer (NFL), ganglion cell (GC) layer, and inner plexiform layer (IPL) but very weak labeling in the inner nuclear layer (INL). Note the branching brush-like appearance of the pattern of AQP4 expression and also the appearance of several sublaminae in the IPL, which is similar to the previously described morphology of the Müller cell [51]. Bar is 20 µm.
Mentions: AQP4 expression showed a regionalized distribution across the transverse retina in all eyes. The most intense AQP4 immunoreactivity was always exhibited in the innermost portions of the retina along the vitreoretinal interface, the NFL, ganglion cell (GC) layer, and the IPL (Figure 1A). The appearance of the many interweaving branching processes matched that of the morphology of the chick Müller cell within the IPL and GC (see Figure 3) as first illustrated in the chick by Cajal Golgi staining (reproduced subsequently in Dreher et al. [51] using 4F3 and 4H11 immunocytochemical labeling. This study also confirmed the appearance of the many interweaving branching processes by the overlay of the immunolabeling image on the differential interference contrast image. The strongly labeled filamentous processes appeared as tightly wrapped bundles around individual ganglion cells (Figure 1A). Several sublaminae outlined by the pattern of AQP4 labeling could be seen within the IPL.

Bottom Line: Aquaporins (AQP) form a family of specialized water channels known to transport water across cell membranes and reduce osmotic gradients.The control eyes showed relatively constant levels of AQP4 expression until day 5 after which the level appeared to decrease.By comparison, positive AQP4 immunoreactivity in the nerve fiber layer increased significantly over the first 48 h in form-deprived eyes and in fellow eyes and then decreased over the next 48 h but not to the level of expression in the normal untreated eyes.

View Article: PubMed Central - PubMed

Affiliation: School of Psychological Science, La Trobe University, Melbourne, Australia.

ABSTRACT

Purpose: Aquaporins (AQP) form a family of specialized water channels known to transport water across cell membranes and reduce osmotic gradients. The isoform AQP4 is highly expressed in the astroglia of the brain and Müller cells in the retina. In the brain, AQP4 play a role in the control of cerebral edema by shunting excess fluid into blood vessels and by upregulating during conditions of hyperosmolarity. Thus, on the basis of the hyperosmolarity seen across the retina and choroid of hatchling chickens made myopic by form deprivation (FD), we predicted an upregulation of retinal AQP4 expression during induction of myopia.

Methods: Two-day-old hatchling chicks were monocularly form-deprived for 48, 72, or 96 h, and then after biometric assessment, the eyes of these animals and the normal controls of the same age were enucleated. Retinal tissue was prepared either for western blot analysis to show the presence of the AQP4 protein in the chick retina or for immunolocalization using polyclonal AQP4 antibodies to determine regional distribution and intensity of labeling during the induction of form deprivation myopia (FDM).

Results: As expected, ultrasonography demonstrated that all post hatchling eyes showed rapid elongation with occluded eyes elongating faster than fellow eyes or normal controls and becoming progressively more myopic with the duration of visual deprivation. Western blot analyses revealed an approximately 30 kDa band immunoreactive for AQP4 protein and confirmed the presence of AQP4 in chicks. Immunohistochemical staining showed the greatest positive immunoreactivity for antibodies to AQP4 in the inner retina along the vitreoretinal interface, nerve fiber layer, ganglion cell layer, and inner plexiform layer in all animals. The control eyes showed relatively constant levels of AQP4 expression until day 5 after which the level appeared to decrease. By comparison, positive AQP4 immunoreactivity in the nerve fiber layer increased significantly over the first 48 h in form-deprived eyes and in fellow eyes and then decreased over the next 48 h but not to the level of expression in the normal untreated eyes.

Conclusions: This is the first study to demonstrate the presence of AQP4 protein in the chick retina and to associate AQP4 expression in the inner retina with the initiation of form deprivation and the period of fastest axial elongation. This increased expression of AQP4 channels near the vitread border during the time of rapid growth suggests a role for AQP4 as a conduit for movement of retinal fluid into the vitreous in form-deprived chicks.

Show MeSH
Related in: MedlinePlus