Abstract
Purpose :
The water transport is conducted by AQP0 for fiber cells and AQP1 for epithelium in the lens. We have previously shown that AQP0 deficiency in fiber cells causes significant upregulation of AQP1 in the epithelium. The increase in water influx from the epithelium caused further damage to the underlying fiber-cell mass. Enlarged anterior lens suture spaces and swollen fiber cells were frequently observed. Here, we report that AQP0-deficiency also induces EMT and connexins (Cx43 & Cx50) changes in lens epithelium.
Methods :
EMT markers (α-actin, fibronectin, vimentin), AQP1, and Cx43 & Cx50 antibodies were used to examine lenses from WT, AQP0-/-, and AQP0+/- mice (P4-16wks old) in this study.
Results :
By confocal immunolabeling on frozen sections, all WT lenses showed negative labeling for α-actin, fibronectin, and vimentin antibodies. In contrast, α-actin (a-SMA) was strongly labeled in the entire epithelial layer in AQP0-/- lenses at P8 and older. Several distinct clusters of labeled epithelial cells with multiple layers were seen overlying the anterior lens sutures. However, strongly labeled fibronectin was mainly found in the detached clusters of EMT cells in the fiber-cell mass. At 2 weeks old, the migrated clusters of mesenchymal cells have reached the lens nucleus, seemingly via the enlarged lens sutures. The migrated mesenchymal cells in the lens nucleus showed positively labeled α-actin, fibronectin, and AQP1 antibodies. A similar pattern of EMT also occurred in the AQP0+/- lenses, suggesting that partial deficiency of AQP0 was able to induce EMT in lens epithelium. By TEM analysis, 5-7 nm F-actin and 10 nm vimentin filaments were seen extensively distributed in EMT cells. Furthermore, since EMT causes epithelial structural changes, we examined possible alterations of Cx43 and Cx50 in epithelial whole mounts. While Cx43 labeling showed only a slight decrease, the labeling of Cx50 was dramatically reduced in the epithelium in AQP0-/- lenses with age, suggesting that cell-cell communication between the epithelium and fiber cells at the interface was significantly reduced during the EMT process.
Conclusions :
This study uncovers for the first time that AQP0 deficiency in lens fibers can induce EMT in anterior epithelial cells. As a result, some epithelial-mesenchymal cells can migrate into damaged nuclear fiber cells in the lens core, apparently through the enlarged anterior lens suture spaces.
This is a 2021 ARVO Annual Meeting abstract.