Quantitative Evaluation of Human Lens Epithelial Cell Viability and Cytolysis by Distilled Water Ex Vivo

Purpose: To investigate the role of distilled water (DW) in isolated human lens epithelial cells (LECs) viability and lysis ex vivo.Methods: After immersion in DW or balanced salt solution (BSS) for 1-, 2-, and 3-minutes, respectively, the cell viability of LECs was quantitatively evaluated. In addition, the capsule samples soaked in DW or BSS for 1-, 2-, and 3-minutes were combined with rinse for 1 minute to analyze the difference of LECs shedding percentage in each subgroup. The histopathological changes of the samples after treating were observed.Results: The percentage of LECs shed in DW immersion combined with rinse was significantly higher than in DW immersion alone (p all <0.001). In the subgroup soaked in DW for 3 minutes, the death number, mortality, and the percentage of cell shedding of LECs was the most (p all <0.001). The histopathological changes showed that the cell destruction in the DW subgroup for 1-, 2-, and 3-minutes, and the transmission electron microscope results showed that the cells were partially detached from the capsule in the DW 3 minutes subgroup.Conclusions: Soaking in the DW can cause LECs death, and DW immersion combined with rinse was an effective method to remove LECs. The histopathology changes of treated DW suggested cellular necrosis was one type of LECs death mechanism.

miRNA-26b suppresses the TGF-β2-induced progression of HLE-B3 cells via the PI3K/Akt pathway

AIM: To study the effect of miR-26b on lens epithelial cells induced by transforming growth factor beta (TGF-β) 2 and the underlying signaling pathways. METHODS: Human lens epithelial cell line B-3 (HLE-B3) was incubated with TGF-β2 (5 ng/mL) and then transfected with miR-26b mimics. The expression of miR-26b was determined using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), while 5’-bromodeoxyuridine (BrdU) and wound-healing assays were used to measure the growth and migration of HLE-B3 cells, respectively. The expression of epithelial-mesenchymal transition (EMT) markers and the activity of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway were measured by Western blotting assay and immunofluorescence staining. Electron microscopy was also used to observe cellular morphology. RESULTS: The expression levels of miR-26b were significantly reduced in human posterior capsular opacification-attached lens tissue and TGF-β2-stimulated HLE-B3 cells. In the presence of TGF-β2, the growth, migration, and EMT of HLE-B3 cells were distinctly enhanced; these effects were attenuated by the administration of miR-26b mimics. Furthermore, the overexpression of miR-26b significantly reduced upregulation of the PI3K/Akt pathway when stimulated by TGF-β2 in HLE-B3 cells. Moreover, the addition of an activator (740 Y-P) led to the upregulation of the PI3K/Akt pathway and abolished the protective effect of miR-26b on the HLE-B3 cells that was mediated by TGF-β2. CONCLUSION: The miR-26b suppresses TGF-β2-induced growth, migration, and EMT in HLE-B3 cells by regulating the PI3K/Akt signaling pathway.

Effect of a Lens Protein in Low-Temperature Culture of Novel Immortalized Human Lens Epithelial Cells (iHLEC-NY2)

The prevalence of nuclear cataracts was observed to be significantly higher among residents of tropical and subtropical regions compared to those of temperate and subarctic regions. We hypothesized that elevated environmental temperatures may pose a risk of nuclear cataract development. The results of our in silico simulation revealed that in temperate and tropical regions, the human lens temperature ranges from 35.0 °C to 37.5 °C depending on the environmental temperature. The medium temperature changes during the replacement regularly in the cell culture experiment were carefully monitored using a sensor connected to a thermometer and showed a decrease of 1.9 °C, 3.0 °C, 1.7 °C, and 0.1 °C, after 5 min when setting the temperature of the heat plate device at 35.0 °C, 37.5 °C, 40.0 °C, and 42.5 °C, respectively. In the newly created immortalized human lens epithelial cell line clone NY2 (iHLEC-NY2), the amounts of RNA synthesis of αA crystallin, protein expression, and amyloid β (Aβ)1-40 secreted into the medium were increased at the culture temperature of 37.5 °C compared to 35.0 °C. In short-term culture experiments, the secretion of Aβ1-40 observed in cataracts was increased at 37.5 °C compared to 35.0 °C, suggesting that the long-term exposure to a high-temperature environment may increase the risk of cataracts.

Glycation-mediated inter-protein cross-linking is promoted by chaperone–client complexes of α-crystallin: Implications for lens aging and presbyopia

Lens proteins become increasingly cross-linked through nondisulfide linkages during aging and cataract formation. One mechanism that has been implicated in this cross-linking is glycation through formation of advanced glycation end products (AGEs). Here, we found an age-associated increase in stiffness in human lenses that was directly correlated with levels of protein–cross-linking AGEs. α-Crystallin in the lens binds to other proteins and prevents their denaturation and aggregation through its chaperone-like activity. Using a FRET-based assay, we examined the stability of the αA-crystallin–γD-crystallin complex for up to 12 days and observed that this complex is stable in PBS and upon incubation with human lens–epithelial cell lysate or lens homogenate. Addition of 2 mm ATP to the lysate or homogenate did not decrease the stability of the complex. We also generated complexes of human αA-crystallin or αB-crystallin with alcohol dehydrogenase or citrate synthase by applying thermal stress. Upon glycation under physiological conditions, the chaperone–client complexes underwent greater extents of cross-linking than did uncomplexed protein mixtures. LC-MS/MS analyses revealed that the levels of cross-linking AGEs were significantly higher in the glycated chaperone–client complexes than in glycated but uncomplexed protein mixtures. Mouse lenses subjected to thermal stress followed by glycation lost resilience more extensively than lenses subjected to thermal stress or glycation alone, and this loss was accompanied by higher protein cross-linking and higher cross-linking AGE levels. These results uncover a protein cross-linking mechanism in the lens and suggest that AGE-mediated cross-linking of α-crystallin–client complexes could contribute to lens aging and presbyopia.