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Woo-Kuen Lo, Sondip K Biswas, Khadar Haroun; Two distinct patterns of epithelial AQP1 expression during lens development with their unique upregulations in AQP0-deficient cataractous mouse lenses. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2852.
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© ARVO (1962-2015); The Authors (2016-present)
The lens water transport is conducted by AQP1 for the epithelium and AQP0 for fiber cells during lens development and growth. AQP0 deficiency causes cataracts in lens fibers. Here, we report that two distinct patterns of epithelial AQP1 upregulations were triggered by the deficiency of AQP0 in fiber cells.
Lenses from WT and AQP0-/- and AQP0+/- (P3-24wks old) were used for confocal immunolabeling of AQP1 on frozen sections and epithelial whole mounts. ImageJ was used to determine the intensity values of the captured images. Lens morphology was studied.
Two expression patterns of AQP1 were observed in the lens epithelium in WT. At P3-9, AQP1 was labeled only in the central epithelium. After P9, AQP1 labeling was gradually increased and intensified in the equatorial zone (250μm long) with age, while only a small area of the labeling was retained in the central epithelium. In sharp contrast, in the AQP0-/- lenses at P3-9, the area and intensity of AQP1 labeling were significantly increased in the central epithelium which overlays the anterior suture of the fiber cells. The AQP1 upregulation was not regularly observed in the equatorial zone. After P9, AQP1 was consistently upregulated in two discrete central and equatorial zones. The confluent labeling of AQP1 in the entire epithelium was seen after 6 weeks of age. Moreover, AQP1 was upregulated in the AQP0+/- lenses. Steady AQP1 labeling was observed in the entire epithelium after 8 weeks of age, suggesting that the AQP1 upregulation in the epithelium can be induced by a partial deficiency of AQP0 in fibers. ImageJ quantification confirmed the increased intensity values of AQP1 labeling between the AQP0-deficient lenses and the age-matched WT. Morphological analyses revealed that the swollen anterior sutures were regularly associated with the cataractous fibers in AQP0-deficient lenses.
AQP1 is expressed in two distinct epithelial regions during lens development and growth. In the mature lens, the equatorial region is the major active route for inflow and outflow of water between the epithelium and fiber cells. In AQP0-deficient lenses, AQP1 was significantly upregulated in the central epithelium. This would cause a large increase in water influx from the epithelium into underlying fibers mostly via anterior sutures and result in further damage to fiber cells.
This is a 2020 ARVO Annual Meeting abstract.
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