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Xiaoyun Chen, Wei Xiao, Shaobi Ye, Yizhi Liu; The Jagged/Notch pathway is involved in TGFβ2-mediated epithelial-mesenchymal transition of human lens epithelial cells and rat anterior subcapsular cataract. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1219.
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The epithelial-mesenchymal transition (EMT) of lens epithelium cells (LECs) plays a key role in anterior subcapsular cataract (ASC) and posterior capsule opacification (PCO), which are important reasons of visual impairment. The Jagged/Notch pathway has been reported to be essential in EMT during embryonic development, fibrotic diseases and cancer metastasis. However, the function of Jagged/Notch signaling in LEC EMT is unknown. We hypothesized that a crosstalk between Notch and TGFβ2 signaling could induce EMT in LECs, which subsequently contributes to ASC and PCO.
The human lens epithelial cell line SRA01/04 was cultured in the presence of TGβ2 alone or with DAPT for 48 hours. The levels of mRNA and protein expression were measured by real-time quantitative PCR and immunoblotting. The expression of EMT markers were also determined by immunofluorescence. The lenses from adult rats were cultured with 5 ng/ml of TGFβ2 for 7 days to induce ASC. Cryo-section and immunofluorescent staining were used to examine the subcapsular clumpy opacities and EMT markers expression.
Stimulation of LECs with TGFβ2 for 48 h increased the expression of Jagged-1, Notch-1, Notch-2, Notch-3 and Notch target genes Hes-1and Hey-1, and induced typical molecular changes of EMT. In contrast, blockade of Notch pathway with DAPT (a specific inhibitor of Notch receptor cleavage), inhibited TGFβ2-induced the up-regulation of collagen type IV, fibronectin, and N-cadherin expression and cytoskeletal changes. Besides canonical Smad signaling, noncanonical PI3K/Akt and MAPK pathways also contribute to TGFβ2 induced activation of Notch pathway in LECs. In addition, treatment of LECs with DAPT attenuated the TGFβ2-induced phosphorylation of Smad2/3. When the lenses were cultured with TGFβ2 for 7 days, lenses developed obvious clumpy anterior opacities beneath the lens capsule, whereas the lenses cultured with DAPT remained transparent, retained normal lens morphology, and did not have accumulation of fibronectin , type IV collagen, α-SMA and vimentin.
Our data suggest that the Jagged/Notch signaling pathway plays a critical role in TGFβ2-induced EMT in human LECs and may contribute to the development of ASC and PCO. Inhibition of the Jagged/Notch signaling therefore may have therapeutic value in the prevention and treatment of ASC and PCO.
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