Transforming growth factor-beta-induced epithelial-mesenchymal transition in the lens: a model for cataract formation

Decorin the antifibrotic proteoglycan and its progression in therapy

Fibrosis, which underlies numerous chronic diseases, is characterized by excessive extracellular matrix (ECM) accumulation, resulting in disrupted tissue architecture. Decorin, a small leucine-rich proteoglycan synthesized primarily by fibroblasts and myoblasts, has emerged as a potent antifibrotic agent mainly by inhibiting transforming growth factor-β (TGF-β), which is a major driver of fibrosis in various tissues and organs such as the heart, eyes, skin, liver, muscle, etc. Numerous therapeutic applications of decorin showcase its ability to reduce fibrosis and improve tissue function. Advances in treatments utilizing recombinant protein, gene-delivery systems, and biomaterials, such as decorin-loaded hydrogels, have demonstrated decorin's potential to improve localized and systemic fibrosis therapies. This review discusses recent advances in decorin's antifibrotic potential and its therapeutic applications.

Harnessing the potential of recombinant human BMP2: regulating scleral changes in myopic guinea pigs

Studies have shown that the development of myopia is associated with scleral remodeling, but the exact mechanism is not yet clear. This study investigates the effects of vitreous injection of recombinant human bone morphogenetic protein 2 (rhBMP2) on scleral remodeling in myopic guinea pigs and the possible signaling pathways. Guinea pigs were randomly divided into normal control (NC) group, lens-induced myopia (LIM) group, rhBMP2 low-dose group (LD), rhBMP2 medium-dose group (MD), and rhBMP2 high-dose group (HD). After rhBMP2 intervention, myopic refraction was reduced and axial growth was delayed compared with the LIM group; Hematoxylin-eosin (H&E) staining showed that the arrangement of scleral collagen fibers was loose, the disorder was improved, and the cavities were reduced, especially in MD group; and immunofluorescence staining showed elevated α-SMA protein expression. Q-PCR and western blot results showed that after rhBMP2 intervention, at the mRNA and protein levels, the expression of BMPRIA, smad1, smad5, smad9, smad4, TIMP2, and Col1A1 was up-regulated, and MMP2 expression was down-regulated when compared with the LIM group. From this study, we conclude that after injecting rhBMP2 into the vitreous cavity of experimental myopic guinea pigs, it can bind to BMP2-related receptors, activate smad signaling pathway, affect the expression of MMP2/TIMP2, promote the expression of Col1A1 gene, regulate scleral remodeling, promote collagen I synthesis, and delay the development of myopia.

Understanding cataract development in axial myopia: The contribution of oxidative stress and related pathways

Myopia is an evolving global health challenge, with estimates suggesting that by 2050 it will affect half of the world's population, becoming the leading cause of irreversible vision loss. Moreover, myopia can lead to various complications, including the earlier onset of cataracts. Given the progressive aging of the population and the increase in life expectancy, this will contribute to a rising demand for cataract surgery, posing an additional challenge for healthcare systems. The pathogenesis of nuclear and posterior subcapsular cataract (PSC) development in axial myopia is complex and primarily involves intensified liquefaction of the vitreous body, excessive production of reactive oxygen species, impaired antioxidant defense, and chronic inflammation in the eyeball. These factors contribute to disruptions in mitochondrial homeostasis, abnormal cell signaling, lipid peroxidation, protein and nucleic acid damage, as well as the induction of adverse epigenetic modifications. Age-related and oxidative processes can cause destabilization of crystallins with subsequent protein accumulation, which finally drives to a lens opacification. Moreover, an altered redox status is one of the major contributors to the pathogenesis of PSC. This review aims to summarize the mechanisms known to be responsible for the accelerated development of cataracts in axial myopia and to enhance understanding of these relationships.

Heat stress regulates the migration and proliferation of lens epithelial cells through ferroptosis and NCOA4-FTH1 interaction

Posterior capsule opacification (PCO) due to the proliferation and migration of lens epithelial cells (LECs) is the main complication after surgery. Heat stress has demonstrated impressive results in halting cell proliferation and migration, while also facilitating cell death. This study aimed to investigate the role and mechanism of ferroptosis in the proliferation and migration of LECs under heat stress. CCK-8 assays, scratch assays, and transcriptome analysis were used to evaluate the impact of temperature on human lens epithelial cells (HLECs) and explore the potential mechanisms. The role of ferroptosis in the proliferation of HLECs induced by heat was investigated using the ferroptosis inhibitor Fer-1 and siRNA-mediated NCOA4 protein interference. Fluorescence staining and Western blot experiments were used to detect the expression of Fe2+, reactive oxygen species (ROS), and ferroptosis-related proteins NCOA4, FTH1, and SLC3A2. The results of CCK-8 assays, scratch assays, and transcriptome analysis demonstrated significant thermal effects on HLEC behavior. After heat treatment, there were significant changes in the fluorescence expression of Fe2+ and ROS in the HLECs and lens explant. In addition, the expression of NCOA4, FTH1, and SLC3A2 also changed significantly. Using Fer-1 or NCOA4 siRNA-mediated interference restored cell viability decreased by thermal stress. Furthermore, interference with NCOA4 protein effectively restored the expression of Fe2+, ROS, and FTH1. In conclusion, heat stress has a significant effect on LECs by regulating ferroptosis and the interaction between NCOA4 and FTH1 proteins play an important role.

The transcription factor CREB regulates epithelial-mesenchymal transition of lens epithelial cells by phosphorylation-dependent and phosphorylation-independent mechanisms

Epithelial mesenchymal transition (EMT) of lens epithelial cells (LECs) is one of the most important pathogenic mechanisms in lens fibrotic disorders, and the regulatory mechanisms of EMT have not been fully understood. Here, we demonstrate that the cAMP-response element binding protein (CREB) can regulate lens EMT in a phosphorylation-dependent and phosphorylation-independent manners with dual mechanisms. First, CREB-S133 phosphorylation is implicated in TGFβ-induced EMT of mouse LECs and also in injury-induced mouse anterior subcapsular cataract model. The interaction between CREB and p300 is necessary for CREB regulation of TGFβ-induced EMT, since inhibition of CREB-p300 interaction and p300 knockdown led to attenuated expression of mesenchymal genes. Second, S133A-CREB, a mutant mimicking constant dephosphorylation at S133, exhibits notable occupancy in the enhancers of mesenchymal genes and confers robust transcription activity on EMT genes. Introduction of R314A mutation in S133A-CREB, which abolishes the interaction between S133A-CREB and its co-activator, cAMP-regulated transcriptional co-activators led to substantial suppression of mesenchymal gene expression in mouse LECs. Taken together, our results showed that CREB regulates lens EMT in dual mechanisms and that the S133A-CREB acts as a novel transcription factor. Mechanistically, CREB interacts with p300 in a S133 phosphorylation-dependent manner to positively regulate lens EMT genes. In contrast, S133A-CREB interacts with cAMP-regulated transcriptional co-activators to confer a robust activation of lens EMT genes.

IL-8 promotes lens capsular residual cells migration by down-regulates expression of E-cadherin and ZO-1 via the CXCR1/2-NF-κB-RhoA signal pathway

BACKGROUND

Posterior capsular opacification is a major complication following cataract surgery, marked by proliferation, migration, epithelial-mesenchymal transition, and fibrosis of residual epithelial cells. Various inflammatory cytokines are upregulated and contribute to the development of posterior capsular opacification. The effect of interleukin-8 on residual epithelial cells has not been fully determined.

METHODS

Aqueous humor and anterior capsules samples were collected from cataract surgery. Capsular bags from rats and pigs were cultured in DMEM media. Protein and mRNA expressions were measured using immunoblot and qPCR. Cell migration was assessed using the transwell assay.

RESULTS

Interleukin-8 is an early inflammatory factor secreted by residual lens epithelial cells. Migration of lens epithelial cells in aqueous humor positively correlates with interleukin-8 levels, and this effect is inhibited by the receptors of interleukin-8 CXCR1/2 blocker Reparaxin. The expression of tight-junction protein ZO-1 and cell-adhesion protein E-cadherin were down-regulated by administrating interleukin-8, and cell migration of both SRA01/04 cell line in vitro and capsular residual epithelial cells ex vivo were up-regulated via activating RhoA expression and RhoA/GTPase activity. The loss-of- function studies demonstrate that interleukin-8 binding to its receptor CXCR1/2 activates NF-κB/p65, which then turns on the RhoA's expression and RhoA/GTPase activity, and RhoA-modulated the downexpression of E-cadherin and ZO-1 and the increase of cell migration.

CONCLUSIONS

The upregulation in interleukin-8 occurs early in posterior capsular opacification and contributes to down-regulating tight-junctions among epithelial cells and elevates cell migration via the CXCR1/2-NF-κB-RhoA signaling pathway. These demonstrated that interleukin-8 could be a potential target for preventing posterior capsular opacification.

Mefunidone Inhibits Inflammation, Oxidative Stress, and Epithelial-Mesenchymal Transition in Lens Epithelial Cells

Purpose

Inflammation, oxidative stress, and epithelial-mesenchymal transition (EMT) play crucial roles in forming posterior capsular opacification (PCO), particularly in fibrotic PCO. Here we investigated the protective effects of mefunidone (MFD), a novel compound with potent antifibrotic properties, which could be useful in preventing PCO.

Methods

We utilized an extracapsular lens extraction (ECLE) surgery in mice to simulate the development of PCO in vivo. Treatment was performed immediately postsurgery through the intracameral injection of MFD solution. Expression levels of EMT and inflammatory markers were analyzed using Western blot, qRT-PCR, immunofluorescence, and hematoxylin and eosin staining. Additionally, the oxidative stress indicator malondialdehyde and glutathione expression were monitored to assess the oxidative stress response. In vitro experiments, TGF-β2, and H2O2 were used to treat lens epithelial cells to induce EMT and oxidative stress models, respectively. These models were employed to explore the effects of MFD and investigate its underlying mechanisms.

Results

Compared to the model group, the group treated with anterior chamber MFD injection effectively suppressed inflammation, oxidative stress, and fibrotic responses within the capsular bag after ECLE and partially inhibited the downregulation of the epithelial marker E-cadherin. To further elucidate the underlying mechanisms, we discovered that MFD treatment in vitro remarkably reduced inflammation, decreased the production of reactive oxygen species, and suppressed the phosphorylation of TGF-β/SMAD as well as MAPK/ERK, thereby inhibiting the occurrence of EMT.

Conclusions

Our findings substantiate the efficacy of MFD in treating PCO and provide insights into its potential mechanisms of action.

Ocular toxicities of FDA-approved antibody drug conjugates

Antibody-drug conjugates (ADCs) are an emerging field of cancer treatments that are becoming more widespread in their use. However, there are potential ocular toxicities associated with these drugs that ophthalmologists need to be aware of to better maintain ocular health as patients undergo rigorous medical treatment for their conditions. While many ADCs have been approved by the Food and Drug Administration (FDA), many subsequent reports have been published regarding additional ocular side effects these drugs may cause. This review provides ophthalmologists with a practical guide on how to treat ocular toxicities associated with all FDA-approved ADCs to date. The potential pathophysiology of side effects is also discussed.

MicroRNA-1225-5p Promotes the Development of Fibrotic Cataracts via Keap1/Nrf2 Signaling

PURPOSE

Fibrotic cataracts, including anterior subcapsular cataract (ASC) as well as posterior capsule opacification (PCO), are a common vision-threatening cause worldwide. Still, little is known about the underlying mechanisms. Here, we demonstrate a miRNA-based pathway regulating the pathological fibrosis process of lens epithelium.

METHODS

Gain- and loss-of-function approaches, as well as multiple fibrosis models of the lens, were applied to validate the crucial role of two miR-1225 family members in the TGF-β2 induced PCO model of human LECs and injury-induced ASC model in mice.

RESULTS

Both miR-1225-3p and miR-1225-5p prominently stimulate the migration and EMT process of lens epithelial cells (LECs) in vitro as well as lens fibrosis in vivo. Moreover, we demonstrated that the underlying mechanism for these effects of miR-1225-5p is via directly targeting Keap1 to regulate Keap1/Nrf2 signaling. In addition, evidence showed that Keap1/Nrf2 signaling is activated in the TGF-β2 induced PCO model of human LECs and injury-induced ASC model in mice, and inhibition of the Nrf2 pathway can significantly reverse the process of LECs EMT as well as lens fibrosis.

CONCLUSIONS

These results suggest that blockade of miR-1225-5p prevents lens fibrosis via targeting Keap1 thereby inhibiting Nrf2 activation. The 'miR-1225-Keap1-Nrf2' signaling axis presumably holds therapeutic promise in the treatment of fibrotic cataracts.

High glucose promotes osteogenic differentiation of human lens epithelial cells through hypoxia-inducible factor (HIF) activation

Cataract, a leading cause of blindness, is characterised by lens opacification. Type 2 diabetes is associated with a two- to fivefold higher prevalence of cataracts. The risk of cataract formation increases with the duration of diabetes and the severity of hyperglycaemia. Hydroxyapatite deposition is present in cataractous lenses that could be the consequence of osteogenic differentiation and calcification of lens epithelial cells (LECs). We hypothesised that hyperglycaemia might promote the osteogenic differentiation of human LECs (HuLECs). Osteogenic medium (OM) containing excess phosphate and calcium with normal (1 g/L) or high (4.5 g/L) glucose was used to induce HuLEC calcification. High glucose accelerated and intensified OM-induced calcification of HuLECs, which was accompanied by hyperglycaemia-induced upregulation of the osteogenic markers Runx2, Sox9, alkaline phosphatase and osteocalcin, as well as nuclear translocation of Runx2. High glucose-induced calcification was abolished in Runx2-deficient HuLECs. Additionally, high glucose stabilised the regulatory alpha subunits of hypoxia-inducible factor 1 (HIF-1), triggered nuclear translocation of HIF-1α and increased the expression of HIF-1 target genes. Gene silencing of HIF-1α or HIF-2α attenuated hyperglycaemia-induced calcification of HuLECs, while hypoxia mimetics (desferrioxamine, CoCl2) enhanced calcification of HuLECs under normal glucose conditions. Overall, this study suggests that high glucose promotes HuLEC calcification via Runx2 and the activation of the HIF-1 signalling pathway. These findings may provide new insights into the pathogenesis of diabetic cataracts, shedding light on potential factors for intervention to treat this sight-threatening condition.

Transcriptome exploration of ferroptosis-related genes in TGFβ- induced lens epithelial to mesenchymal transition during posterior capsular opacification development

BACKGROUND

Posterior capsular opacification (PCO) is the main reason affecting the long-term postoperative result of cataract patient, and it is well accepted that fibrotic PCO is driven by transforming growth factor beta (TGFβ) signaling. Ferroptosis, closely related to various ocular diseases, but has not been explored in PCO.

METHODS

RNA sequencing (RNA-seq) was performed on both TGF-β2 treated and untreated primary lens epithelial cells (pLECs). Differentially expressed genes (DEGs) associated with ferroptosis were analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) to investigate their biological function. Additionally, protein-to-protein interactions among selected ferroptosis-related genes by PPI network and the top 10 genes with the highest score (MCC algorithm) were selected as the hub genes. The top 20 genes with significant fold change values were validated using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Our analysis revealed 1253 DEGs between TGF-β2 treated and untreated pLECs, uncovering 38 ferroptosis-related genes between two groups. Among these 38 ferroptosis-related genes,the most prominent GO enrichment analysis process involved in the response to oxidative stress (BPs), apical part of cell (CCs),antioxidant activity (MFs). KEGG were mainly concentrated in fluid shear stress and atherosclerosis, IL-17 and TNF signaling pathways, and validation of top 20 genes with significant fold change value were consistent with RNA-seq.

CONCLUSIONS

Our RNA-Seq data identified 38 ferroptosis-related genes in TGF-β2 treated and untreated pLECs, which is the first observation of ferroptosis related genes in primary human lens epithelial cells under TGF-β2 stimulation.

Tonic ErbB signaling underlies TGFβ-induced activation of ERK and is required for lens cell epithelial to myofibroblast transition

Fibrosis is a major, but incompletely understood, component of many diseases. The most common vision-disrupting complication of cataract surgery involves differentiation of residual lens cells into myofibroblasts. In serum-free primary cultures of lens epithelial cells (DCDMLs), inhibitors of either ERK or of ErbB signaling prevent TGFβ from upregulating both early (fibronectin) and late (αSMA) markers of myofibroblast differentiation. TGFβ stimulates ERK in DCDMLs within 1.5 h. Kinase inhibitors of ErbBs, but not of several other growth factor receptors in lens cells, reduce phospho ERK to below basal levels in the absence or presence of TGFβ. This effect is attributable to constitutive ErbB activity playing a major role in regulating the basal levels pERK. Additional studies support a model in which TGFβ-generated reactive oxygen species serve to indirectly amplify ERK signaling downstream of tonically active ErbBs to mediate myofibroblast differentiation. ERK activity is in turn essential for expression of ErbB1 and ErbB2, major inducers of ERK signaling. By mechanistically linking TGFβ, ErbB, and ERK signaling to myofibroblast differentiation, our data elucidate a new role for ErbBs in fibrosis and reveal a novel mode by which TGFβ directs lens cell fate.

Smurf1 Modulates Smad Signaling Pathway in Fibrotic Cataract Formation

Purpose

TGF-β/BMP signaling pathway plays a significant role in fibrotic cataract. Smurf1, a ubiquitin protein ligase, regulates the TGF-β/BMP signaling pathway through the ubiquitin-proteasome system (UPS). This study aims to investigate the role of Smurf1 in the progression of fibrotic cataract and its underlying mechanism.

Methods

We used a mouse model of injury-induced anterior subcapsular cataract (ASC) and administered the Smurf1 inhibitor A01 for in vivo investigations. RNA sequencing was performed to examine global gene expression changes. Protein levels were assessed by Simple Western analysis. The volume of subcapsular opacity was determined using whole-mount immunofluorescence of lens anterior capsules. Lentivirus was utilized to establish cell lines with Smurf1 knockdown or overexpression in SRA01/04. Lens epithelial cell (LEC) proliferation was evaluated by CCK8 and EdU assays. Cell cycle profile was determined by flow cytometry. LEC migration was measured using Transwell and wound healing assays.

Results

The mRNA levels of genes associated with cell proliferation, migration, epithelial-mesenchymal transition (EMT), TGF-β/BMP pathway, and UPS were upregulated in mouse ASC model. Smurf1 mRNA and protein levels were upregulated in lens capsules of patients and mice with ASC. Anterior chamber injection of A01 inhibited ASC formation and EMT. In vitro, Smurf1 knockdown reduced proliferation, migration and TGF-β2-induced EMT of LECs, concomitant with the upregulation of Smad1, Smad5, and pSmad1/5. Conversely, overexpression of Smurf1 showed opposite phenotypes.

Conclusions

Smurf1 regulates fibrotic cataract progression by influencing LEC proliferation, migration, and EMT through the modulation of the Smad signaling pathway, offering a novel target for the fibrotic cataract treatment.

Understanding the Role of Yes-Associated Protein (YAP) Signaling in the Transformation of Lens Epithelial Cells (EMT) and Fibrosis

Fibrotic cataracts, posterior capsular opacification (PCO), and anterior subcapsular cataracts (ASC) are mainly attributed to the transforming growth factor-β (TGFβ)-induced epithelial-to-mesenchymal transition (EMT) of lens epithelial cells (LECs). Previous investigations from our laboratory have shown the novel role of non-canonical TGFβ signaling in the progression of EMT in LECs. In this study, we have identified YAP as a critical signaling molecule involved in lens fibrosis. The observed increase in nuclear YAP in capsules of human ASC patients points toward the involvement of YAP in lens fibrosis. In addition, the immunohistochemical (IHC) analyses on ocular sections from mice that overexpress TGFβ in the lens (TGFβtg) showed a co-expression of YAP and α-SMA in the fibrotic plaques when compared to wild-type littermate lenses, which do not. The incubation of rat lens explants with verteporfin, a YAP inhibitor, prevented a TGFβ-induced fiber-like phenotype, α-SMA, and fibronectin expression, as well as delocalization of E-cadherin and β-catenin. Finally, LECs co-incubated with TGFβ and YAP inhibitor did not exhibit an induction in matrix metalloproteinase 2 compared to those LECs treated with TGFβ alone. In conclusion, these data demonstrate that YAP is required for TGFβ-mediated lens EMT and fibrosis.

Lanosterol Synthase Prevents EMT During Lens Epithelial Fibrosis Via Regulating SREBP1

Purpose

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a predominant pathological process underlying fibrotic cataracts. Here we investigated the role and mechanism of lanosterol synthase (LSS), a key rate-limiting enzyme in sterol biosynthesis, in EMT of LECs.

Methods

Human lens epithelial explants, primary rabbit LECs, and whole rat lenses were treated with TGFβ2. RNA-sequencing was conducted to explore genetic changes during fibrosis of human lens epithelial explants. Loss- and gain-of-function studies were performed in primary LECs to investigate roles and mechanisms of LSS, lanosterol and sterol regulatory element binding transcription protein 1 (SREBP1) in EMT. Rat lenses were applied to evaluate the potential effect of lanosterol on lens fibrosis. Expression of LSS, SREBP1, EMT-related regulators, and markers were analyzed by Western blot, qRT-PCR, or immunofluorescent staining.

Results

LSS and steroid biosynthesis were downregulated in TGFβ2-induced lens fibrosis. LSS inhibition directly triggered EMT by inducing Smad2/3 phosphorylation and nucleus translocation, an overexpression of LSS protected LECs from EMT by inhibiting Smad2/3 activation. Moreover, LSS inhibition decreased the expression of SREBP1, which regulated EMT via intervening TGFβ2/Smad2/3 transduction. Furthermore, lanosterol protected LECs from EMT caused by both TGFβ2 treatment and LSS inhibition via suppressing Smad2/3 activation and maintained lens transparency by preventing fibrotic plaques formation.

Conclusions

We first identified that LSS protected LECs from EMT and played an antifibrotic role to maintain lens transparency. Additionally, lanosterol and sterol biosynthesis regulation might be promising strategies for preventing and treating fibrotic cataracts.

Gene profiles and mutations in the development of cataracts in the ICR rat model of hereditary cataracts

Cataracts are opacifications of the lens that cause loss of visual acuity and ultimately of eyesight. Age-related cataract develops in most elderly people, but the mechanisms of cataract onset are incompletely understood. The Ihara Cataract Rat (ICR) is an animal model of hereditary cataracts showing cortical opacity that commonly develops prematurely. We identified putative mechanisms of cataract onset in the ICR rat model by measuring gene expression changes before and after cortical cataract development and conducting point mutation analysis. Genes differentially expressed between 4-week-old animals without cortical cataracts and 8-10-week-old animals with cortical cataracts were selected from microarray analysis. Three connections were identified by STRING analysis: (i) Epithelial-Mesenchymal Transition (EMT), including Col1a2, and Pik3r1. (ii) Lens homeostasis, including Aqp5, and Cpm. (iii) Lipid metabolism, including Scd1, Srebf1, and Pnpla3. Subsequently, mutation points were selected by comparing ICR rats with 12 different rats that do not develop cataracts. The apolipoprotein Apoc3 was mutated in ICR rats. Analyses of gene expression changes and point and mutations suggested that abnormalities in EMT or lipid metabolism could contribute to cataract development in ICR rats.

Arginase-1 promotes lens epithelial-to-mesenchymal transition in different models of anterior subcapsular cataract

BACKGROUND

Arginase-1 (ARG1) promotes collagen synthesis and cell proliferation. ARG1 is highly expressed in various tumour cells. The mechanisms of ARG1 in epithelial-to-mesenchymal transition (EMT)-associated cataracts were studied herein.

METHODS

C57BL/6 mice, a human lens epithelial cell line (HLEC-SRA01/04), and human lens capsule samples were used in this study. The right lens anterior capsule of the mouse eye was punctured through the central cornea with a 26-gauge hypodermic needle. Human lens epithelial cells (HLECs) were transfected with ARG1-targeted (siARG1) or negative control siRNA (siNC). For gene overexpression, HLECs were transfected with a plasmid bearing the ARG1 coding sequence or an empty vector. Medium containing 0.2% serum with or without transforming growth factor beta-2 (TGF-β2) was added for 6 or 24 h to detect mRNA or protein, respectively. The expression of related genes was measured by quantitative real-time polymerase chain reaction (RT-qPCR), western blotting, and immunohistochemical staining. Transwell assays and wound healing assays were used to determine cell migration. Cell proliferation, superoxide levels, nitric oxide (NO) levels, and arginase activity were estimated using Cell Counting Kit-8 assays, a superoxide assay kit, an NO assay kit, and an arginase activity kit.

RESULTS

ARG1, alpha-smooth muscle actin (α-SMA), fibronectin, and Ki67 expression increased after lens capsular injury, while zonula occludens-1 (ZO-1) expression decreased. Fibronectin and collagen type I alpha1 chain (collagen 1A1) expression increased, and cell migration increased significantly in ARG1-overexpressing HLECs compared with those transfected with an empty vector after TGF-β2 treatment. These effects were reversed by ARG1 knockdown. The arginase-related pathway plays an important role in EMT. mRNAs of enzymes of the arginase-related pathway were highly expressed after ARG1 overexpression. ARG1 knockdown suppressed these expression changes. Numidargistat (CB-1158) dihydrochloride (CB-1158), an ARG1 inhibitor, suppressed TGF-β2-induced anterior subcapsular cataract (ASC) by reducing the proliferation of lens epithelial cells (LECs) and decreasing fibronectin, α-SMA, collagen 1A1, and vimentin expression. Compared with that in nonanterior subcapsular cataract (non-ASC) patients, the expression of ARG1, collagen 1A1, vimentin, fibronectin, and Ki67 was markedly increased in ASC patients.

CONCLUSIONS

ARG1 can regulate EMT in EMT-associated cataracts. Based on the pathogenesis of ASC, these findings are expected to provide new therapeutic strategies for patients.

Endoplasmic reticulum stress: molecular mechanism and therapeutic targets

The endoplasmic reticulum (ER) functions as a quality-control organelle for protein homeostasis, or "proteostasis". The protein quality control systems involve ER-associated degradation, protein chaperons, and autophagy. ER stress is activated when proteostasis is broken with an accumulation of misfolded and unfolded proteins in the ER. ER stress activates an adaptive unfolded protein response to restore proteostasis by initiating protein kinase R-like ER kinase, activating transcription factor 6, and inositol requiring enzyme 1. ER stress is multifaceted, and acts on aspects at the epigenetic level, including transcription and protein processing. Accumulated data indicates its key role in protein homeostasis and other diverse functions involved in various ocular diseases, such as glaucoma, diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, achromatopsia, cataracts, ocular tumors, ocular surface diseases, and myopia. This review summarizes the molecular mechanisms underlying the aforementioned ocular diseases from an ER stress perspective. Drugs (chemicals, neurotrophic factors, and nanoparticles), gene therapy, and stem cell therapy are used to treat ocular diseases by alleviating ER stress. We delineate the advancement of therapy targeting ER stress to provide new treatment strategies for ocular diseases.

Current Approach to the Pathogenesis of Diabetic Cataracts

Cataracts remain the first or second leading cause of blindness in all world regions. In the diabetic population, cataracts not only have a 3–5 times higher incidence than in the healthy population but also affect people at a younger age. In patients with type 1 diabetes, cataracts occur on average 20 years earlier than in the non-diabetic population. In addition, the risk of developing cataracts increases with the duration of diabetes and poor metabolic control. A better understanding of the mechanisms leading to the formation of diabetic cataracts enables more effective treatment and a holistic approach to the patient.

FGF-2 Differentially Regulates Lens Epithelial Cell Behaviour during TGF-β-Induced EMT

Fibroblast growth factor (FGF) and transforming growth factor-beta (TGF-β) can regulate and/or dysregulate lens epithelial cell (LEC) behaviour, including proliferation, fibre differentiation, and epithelial–mesenchymal transition (EMT). Earlier studies have investigated the crosstalk between FGF and TGF-β in dictating lens cell fate, that appears to be dose dependent. Here, we tested the hypothesis that a fibre-differentiating dose of FGF differentially regulates the behaviour of lens epithelial cells undergoing TGF-β-induced EMT. Postnatal 21-day-old rat lens epithelial explants were treated with a fibre-differentiating dose of FGF-2 (200 ng/mL) and/or TGF-β2 (50 pg/mL) over a 7-day culture period. We compared central LECs (CLECs) and peripheral LECs (PLECs) using immunolabelling for changes in markers for EMT (α-SMA), lens fibre differentiation (β-crystallin), epithelial cell adhesion (β-catenin), and the cytoskeleton (alpha-tropomyosin), as well as Smad2/3- and MAPK/ERK1/2-signalling. Lens epithelial explants cotreated with FGF-2 and TGF-β2 exhibited a differential response, with CLECs undergoing EMT while PLECs favoured more of a lens fibre differentiation response, compared to the TGF-β-only-treated explants where all cells in the explants underwent EMT. The CLECs cotreated with FGF and TGF-β immunolabelled for α-SMA, with minimal β-crystallin, whereas the PLECs demonstrated strong β-crystallin reactivity and little α-SMA. Interestingly, compared to the TGF-β-only-treated explants, α-SMA was significantly decreased in the CLECs cotreated with FGF/TGF-β. Smad-dependent and independent signalling was increased in the FGF-2/TGF-β2 co-treated CLECs, that had a heightened number of cells with nuclear localisation of Smad2/3 compared to the PLECs, that in contrast had more pronounced ERK1/2-signalling over Smad2/3 activation. The current study has confirmed that FGF-2 is influential in differentially regulating the behaviour of LECs during TGF-β-induced EMT, leading to a heterogenous cell population, typical of that observed in the development of post-surgical, posterior capsular opacification (PCO). This highlights the cooperative relationship between FGF and TGF-β leading to lens pathology, providing a different perspective when considering preventative measures for controlling PCO.

Heparan sulfate proteoglycans (HSPGs) of the ocular lens

Heparan sulfate proteoglycans (HSPGs) reside in most cells; on their surface, in the pericellular milieu and/or extracellular matrix. In the eye, HSPGs can orchestrate the activity of key signalling molecules found in the ocular environment that promote its development and homeostasis. To date, our understanding of the specific roles played by individual HSPG family members, and the heterogeneity of their associated sulfated HS chains, is in its infancy. The crystalline lens is a relatively simple and well characterised ocular tissue that provides an ideal stage to showcase and model the expression and unique roles of individual HSPGs. Individual HSPG core proteins are differentially localised to eye tissues in a temporal and spatial developmental- and cell-type specific manner, and their loss or functional disruption results in unique phenotypic outcomes for the lens, and other ocular tissues. More recent work has found that different HS sulfation enzymes are also presented in a cell- and tissue-specific manner, and that disruption of these different sulfation patterns affects specific HS-protein interactions. Not surprisingly, these sulfated HS chains have also been reported to be required for lens and eye development, with dysregulation of HS chain structure and function leading to pathogenesis and eye-related phenotypes. In the lens, HSPGs undergo significant and specific changes in expression and function that can drive pathology, or in some cases, promote tissue repair. As master signalling regulators, HSPGs may one day serve as valuable biomarkers, and even as putative targets for the development of novel therapeutics, not only for the eye but for many other systemic pathologies.

Regulation of the Inflammatory Response, Proliferation, Migration, and Epithelial-Mesenchymal Transition of Human Lens Epithelial Cells by the lncRNA-MALAT1/miR-26a-5p/TET1 Signaling Axis

Background

The ocular inflammatory microenvironment has been reported to be closely associated with the occurrence and progression of highly myopic cataract (HMC). Long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) could alter the biological properties of mammalian cells by modulating the expression of inflammatory mediators; therefore, it may contribute to the development of HMC.

Objective

To investigate the function of MALAT1 in the inflammatory response, proliferation, migration, and epithelial-mesenchymal transition (EMT) of inflammatory and injured human lens epithelial cells (HLECs) and to reveal the underlying molecular signals.

Methods

Patients with HMC and age-related cataract (ARC) with an axial length of more than 26 mm were selected, and the anterior capsular tissue was obtained during cataract surgery. TNF-α (20 ng/mL) was chosen to induce inflammatory damage in HLECs to simulate the inflammatory microenvironment in HMC eyes. Specific siRNAs, inhibitors, and mimics were used to suppress or enhance the functions of MALAT1 and miR-26a-5p. RT-qPCR and Western blot analysis were performed to measure gene and protein expression, respectively.

Results

The expression of MALAT1 and the inflammatory mediators IL-6, MMP-2, and MMP-9 were significantly higher in HMC anterior capsule tissues than in ARC. TNF-α treatment increased the expression of MALAT1, while it also promoted the proliferation, migration, and EMT of HLECs. MALAT1 interference decreased the expression of IL-6 and MMP-2 and inhibited the aforementioned processes. Furthermore, MALAT1 negatively regulated the expression of miR-26a-5p and then promoted TET1 expression. TET1 was identified as a direct target of miR-26a-5p, and the promoting effect of MALAT1 on TET1 expression could be reversed by miR-26a-5p mimics.

Conclusion

The inflammatory environment and MALAT1 expression could be reciprocally induced in HLECs. MALAT1 may act as a ceRNA via the "sponge" miR-26a-5p and target TET1 to regulate the inflammatory response, proliferation, migration, and EMT processes in HLECs.

Role of Decorin in the Lens and Ocular Diseases

Decorin is an archetypal member of the small leucine-rich proteoglycan gene family and is involved in various biological functions and many signaling networks, interacting with extra-cellular matrix (ECM) components, growth factors, and receptor tyrosine kinases. Decorin also modulates the growth factors, cell proliferation, migration, and angiogenesis. It has been reported to be involved in many ischemic and fibrotic eye diseases, such as congenital stromal dystrophy of the cornea, anterior subcapsular fibrosis of the lens, proliferative vitreoretinopathy, et al. Furthermore, recent evidence supports its role in secondary posterior capsule opacification (PCO) after cataract surgery. The expression of decorin mRNA in lens epithelial cells in vitro was found to decrease upon transforming growth factor (TGF)-β-2 addition and increase upon fibroblast growth factor (FGF)-2 addition. Wound healing of the injured lens in mice transgenic for lens-specific human decorin was promoted by inhibiting myofibroblastic changes. Decorin may be associated with epithelial-mesenchymal transition and PCO development in the lens. Gene therapy and decorin administration have the potential to serve as excellent therapeutic approaches for modifying impaired wound healing, PCO, and other eye diseases related to fibrosis and angiogenesis. In this review, we present findings regarding the roles of decorin in the lens and ocular diseases.

Blue light attenuates TGF-β2-induced epithelial-mesenchymal transition in human lens epithelial cells via autophagy impairment

Background

Pathogenesis of posterior capsular opacification (PCO) was related to pathological epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs). It has been reported that blue light could have an effect on EMT. This study aims to elucidate the role and potential mechanism of autophagy in EMT after blue light exposure in LECs.

Methods

HLE-B3 cells were treated with TGF-β2 with different concentration and time to induce EMT as a model of PCO in vitro. Cells were exposed to blue light with or without TGF-β2. The expression levels of EMT-associated markers were analyzed by qRT-PCR, western blotting and cell migration ability was determined by transwell migration assay and wound healing assay. The expressions of autophagy-related proteins were analyzed by western blotting, immunofluorescence and transmission electron microscopy. Rapamycin and chloroquine were utilized in cells for autophagy activation and inhibition.

Results

TGF-β2 induced autophagy activation during EMT progression in HLE-B3 cells in a dose- and time-dependent manner. Blue light exposure inhibited TGF-β2-induced EMT characterized by inhibited expression of EMT related markers and reduced migration capacity. Meanwhile, blue light exposure impaired autophagy activated by TGF-β2. Furthermore, Autophagy activation with rapamycin rescued EMT attenuated by blue light. Autophagy inhibition with chloroquine reduced TGF-β2-induced EMT in HLE-B3 cells.

Conclusion

Blue light exposure had inhibited effects on TGF-β2-induced EMT in LECs through autophagy impairment, which provides a new insight on prevention and treatment of PCO.

Histone acetyltransferase inhibition reverses opacity in rat galactose-induced cataract

Cataract, a disease that causes opacity of the lens, is the leading cause of blindness worldwide. Cataracts secondary to diabetes are common, even in young patients, so they are of significant clinical importance. Here, we used an ex vivo model of galactose-induced cataracts in the rat lens to investigate the therapeutic effects of histone acetyltransferase (HAT) inhibitors. Among the tested HAT inhibitors, TH1834 was the only one that could reverse most of the opacity once it had formed in the lens. Combination treatment with C646/CPTH2 and CBP30/CPTH2 also had therapeutic effects. In lens cross-sections, vacuoles were present in the tissue of the cortical equatorial region of untreated cataract samples. In treated cataract samples, lens tissue regenerated to fill the vacuoles. To identify the genes regulated by HAT inhibitors, qRT-PCR was performed on treated and untreated cataract samples to determine candidate genes. Expression of Acta1 and Stmn4, both of which are involved in the cytoskeleton, were altered significantly in C646+CPTH2 samples. Expression of Emd, a nuclear membrane protein, and Prtfdc1, which is involved in cancer cell proliferation, were altered significantly in CBP30+CPTH2 samples. Acta1, Acta2, Arrdc3, Hebp2, Hist2h2ab, Pmf1, Ppdpf, Rbm3, RGD1561694, Slc16a6, Slfn13, Tagln, Tgfb1i1, and Tuba1c in TH1834 samples were significantly altered. These genes were primarily related to regulation of cell proliferation, the cytoskeleton, and cell differentiation. Expression levels increased with the onset of cataracts and was suppressed in samples treated with HAT inhibitors.

TGF-β/Smad Signalling Activation by HTRA1 Regulates the Function of Human Lens Epithelial Cells and Its Mechanism in Posterior Subcapsular Congenital Cataract

Congenital cataract is the leading cause of blindness among children worldwide. Patients with posterior subcapsular congenital cataract (PSC) in the central visual axis can result in worsening vision and stimulus deprivation amblyopia. However, the pathogenesis of PSC remains unclear. This study aims to explore the functional regulation and mechanism of HTRA1 in human lens epithelial cells (HLECs). HTRA1 was significantly downregulated in the lens capsules of children with PSC compared to normal controls. HTRA1 is a suppression factor of transforming growth factor-β (TGF-β) signalling pathway, which plays a key role in cataract formation. The results showed that the TGF-β/Smad signalling pathway was activated in the lens tissue of PSC. The effect of HTRA1 on cell proliferation, migration and apoptosis was measured in HLECs. In primary HLECs, the downregulation of HTRA1 can promote the proliferation and migration of HLECs by activating the TGF-β/Smad signalling pathway and can significantly upregulate the TGF-β/Smad downstream target genes FN1 and α-SMA. HTRA1 was also knocked out in the eyes of C57BL/6J mice via adeno-associated virus-mediated RNA interference. The results showed that HTRA1 knockout can significantly upregulate p-Smad2/3 and activate the TGF-β/Smad signalling pathway, resulting in abnormal proliferation and irregular arrangement of lens epithelial cells and leading to the occurrence of subcapsular cataract. To conclude, HTRA1 was significantly downregulated in children with PSC, and the downregulation of HTRA1 enhanced the proliferation and migration of HLECs by activating the TGF-β/Smad signalling pathway, which led to the occurrence of PSC.

The Immediate Early Response of Lens Epithelial Cells to Lens Injury

Cataracts are treated by lens fiber cell removal followed by intraocular lens (IOL) implantation into the lens capsule. While effective, this procedure leaves behind numerous lens epithelial cells (LECs) which undergo a wound healing response that frequently leads to posterior capsular opacification (PCO). In order to elucidate the acute response of LECs to lens fiber cell removal which models cataract surgery (post cataract surgery, PCS), RNA-seq was conducted on LECs derived from wild type mice at 0 and 6 h PCS. This analysis found that LECs upregulate the expression of numerous proinflammatory cytokines and profibrotic regulators by 6 h PCS suggesting rapid priming of pathways leading to inflammation and fibrosis PCS. LECs also highly upregulate the expression of numerous immediate early transcription factors (IETFs) by 6 h PCS and immunolocalization found elevated levels of these proteins by 3 h PCS, and this was preceded by the phosphorylation of ERK1/2 in injured LECs. Egr1 and FosB were among the highest expressed of these factors and qRT-PCR revealed that they also upregulate in explanted mouse lens epithelia suggesting potential roles in the LEC injury response. Analysis of lenses lacking either Egr1 or FosB revealed that both genes may regulate a portion of the acute LEC injury response, although neither gene was essential for expression of either proinflammatory or fibrotic markers at later times PCS suggesting that IETFs may work in concert to mediate the LEC injury response following cataract surgery.

Bit1 is involved in regulation between integrin and TGFβ signaling in lens epithelial cells

Bit1, as an integrin-specific effector, is specifically expressed in lens epithelial cells (LECs) and may be essential to maintain the normal function of LECs. The present study investigated the function of Bit1 and its regulatory mechanism in LECs. Knockdown of Bit1 was mediated by a lentivirus with a specific short-hairpin RNA against Bit1 in SRA01/04 cells. Cell proliferation ability was measured by CCK-8 assay. Cell migration was examined by transwell and wound-healing assays. The effect of Bit1 knockdown on genome-wide expression patterns was studied via a GeneChip® PrimeView™ Human Gene Expression Array. Based on the ingenuity pathway analysis (IPA), Bit1's regulation of target pathways and genes was verified by real-time qPCR and Western blotting. Bit1 knockdown inhibited proliferation, migration, and regulated cell cycle and apoptosis of LECs. Microarray gene expression analysis and IPA assays revealed that integrin and TGFβ signaling pathways were remarkably impacted by Bit1 expression. FAK, PAK2, ITGA5, and ITGB1 were identified as core node molecules under the control of Bit1. Bit1 participates in integrin and TGFβ signaling via regulating downstream FAK and PAK2 and subsequently affecting EMT-related gene expression including ITGA5, ITGB1, and αSMA. In conclusion, Bit1 plays as an important role in the regulation between integrin and TGFβ signaling, which affects cell survival, migration, and EMT of LECs.

Long Non-Coding RNA H19 Prevents Lens Fibrosis through Maintaining Lens Epithelial Cell Phenotypes

The integrity of lens epithelial cells (LECs) lays the foundation for lens function and transparency. By contrast, epithelial-mesenchymal transition (EMT) of LECs leads to lens fibrosis, such as anterior subcapsular cataracts (ASC) and fibrotic forms of posterior capsule opacification (PCO). However, the underlying mechanisms remain unclear. Here, we aimed to explore the role of long non-coding RNA (lncRNA) H19 in regulating TGF-β2-induced EMT during lens fibrosis, revealing a novel lncRNA-based regulatory mechanism. In this work, we identified that lncRNA H19 was highly expressed in LECs, but downregulated by exposure to TGF-β2. In both human lens epithelial explants and SRA01/04 cells, knockdown of H19 aggravated TGF-β2-induced EMT, while overexpressing H19 partially reversed EMT and restored lens epithelial phenotypes. Semi-in vivo whole lens culture and H19 knockout mice demonstrated the indispensable role of H19 in sustaining lens clarity through maintaining LEC features. Bioinformatic analyses further implied a potential H19-centered regulatory mechanism via Smad-dependent pathways, confirmed by in vitro experiments. In conclusion, we uncovered a novel role of H19 in inhibiting TGF-β2-induced EMT of the lens by suppressing Smad-dependent signaling, providing potential therapeutic targets for treating lens fibrosis.

Circ-POLR3A accelerates TGF-β2-induced promotion in cell viability, migration, and invasion of lens epithelial cells via miR-31/TXNIP signaling cascade

Posterior capsular opacification (PCO) is the major complication after cataract surgery and can result in secondary vision loss. Circular RNAs (circRNAs) are reported to play critical regulatory roles in multiple cell biological processes. The most common working mechanism of circRNAs is by acting as microRNA sponges. Here, we analyzed the role and mechanism of circRNA RNA polymerase III subunit A (POLR3A) in PCO. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell motility was assessed by transwell and wound healing assays. Dual-luciferase reporter and RNA-pull-down assays were performed to verify the interaction between microRNA-31 (miR-31) and circ-POLR3A or thioredoxin interacting protein (TXNIP). PCO cell model was established by treating SRA01/04 cells with transforming growth factor-β2 (TGF-β2). We found that TGF-β2 enhanced SRA01/04 cell viability, migration, and invasion abilities. Circ-POLR3A expression was upregulated in PCO tissues and TGF-β2-induced SRA01/04 cells. TGF-β2 promoted the viability and motility of SRA01/04 cells largely by upregulating circ-POLR3A. Circ-POLR3A negatively regulated the miR-31 level by directly interacting with it. Circ-POLR3A absence-induced influences in TGF-β2-induced SRA01/04 cells were partly reversed by silencing miR-31. miR-31 is directly bound to the 3'-untranslated region of TXNIP. TXNIP overexpression largely attenuated miR-31 overexpression-mediated effects in TGF-β2-induced SRA01/04 cells. Circ-POLR3A could elevate the protein expression of TXNIP by sponging miR-31. Exosomes were involved in mediating the delivery of circ-POLR3A in SRA01/04 cells. In conclusion, circ-POLR3A contributed to TGF-β2-induced promotion of cell viability, migration, and invasion of SRA01/04 cells by targeting miR-31/TXNIP axis.

Lens Fibrosis: Understanding the Dynamics of Cell Adhesion Signaling in Lens Epithelial-Mesenchymal Transition

Injury to the ocular lens perturbs cell-cell and cell-capsule/basement membrane interactions leading to a myriad of interconnected signaling events. These events include cell-adhesion and growth factor-mediated signaling pathways that can ultimately result in the induction and progression of epithelial-mesenchymal transition (EMT) of lens epithelial cells and fibrosis. Since the lens is avascular, consisting of a single layer of epithelial cells on its anterior surface and encased in a matrix rich capsule, it is one of the most simple and desired systems to investigate injury-induced signaling pathways that contribute to EMT and fibrosis. In this review, we will discuss the role of key cell-adhesion and mechanotransduction related signaling pathways that regulate EMT and fibrosis in the lens.

MYPT1/PP1-Mediated EZH2 Dephosphorylation at S21 Promotes Epithelial-Mesenchymal Transition in Fibrosis through Control of Multiple Families of Genes

The methyltransferase EZH2 plays an important role in regulating chromatin conformation and gene transcription. Phosphorylation of EZH2 at S21 by AKT kinase suppresses its function. However, protein phosphatases responsible for the dephosphorylation of EZH2-S21 remain elusive. Here, it is demonstrated that EZH2 is highly expressed in the ocular lens, and AKT-EZH2 axis is important in TGFβ-induced epithelial-mesenchymal transition (EMT). More importantly, it is identified that MYPT1/PP1 dephosphorylates EZH2-S21 and thus modulates its functions. MYPT1 knockout accelerates EMT, but expression of the EZH2-S21A mutant suppresses EMT through control of multiple families of genes. Furthermore, the phosphorylation status and gene expression modulation of EZH2 are implicated in control of anterior subcapsular cataracts (ASC) in human and mouse eyes. Together, the results identify the specific phosphatase for EZH2-S21 and reveal EZH2 dephosphorylation control of several families of genes implicated in lens EMT and ASC pathogenesis. These results provide important novel information in EZH2 function and regulation.

Activation of Nrf2/HO-1 Antioxidant Pathway by Heme Attenuates Calcification of Human Lens Epithelial Cells

Cataract, an opacification in the crystalline lens, is a leading cause of blindness. Deposition of hydroxyapatite occurs in a cataractous lens that could be the consequence of osteogenic differentiation of lens epithelial cells (LECs). Nuclear factor erythroid 2-related factor 2 (Nrf2) controls the transcription of a wide range of cytoprotective genes. Nrf2 upregulation attenuates cataract formation. Here we aimed to investigate the effect of Nrf2 system upregulation in LECs calcification. We induced osteogenic differentiation of human LECs (HuLECs) with increased phosphate and calcium-containing osteogenic medium (OM). OM-induced calcium and osteocalcin deposition in HuLECs. We used heme to activate Nrf2, which strongly upregulated the expression of Nrf2 and heme oxygenase-1 (HO-1). Heme-mediated Nrf2 activation was dependent on the production of reactive oxygens species. Heme inhibited Ca deposition, and the OM-induced increase of osteogenic markers, RUNX2, alkaline phosphatase, and OCN. Anti-calcification effect of heme was lost when the transcriptional activity of Nrf2 or the enzyme activity of HO-1 was blocked with pharmacological inhibitors. Among products of HO-1 catalyzed heme degradation iron mimicked the anti-calcification effect of heme. We concluded that heme-induced upregulation of the Nrf2/HO-1 system inhibits HuLECs calcification through the liberation of heme iron.

Interfering Hsa_circRNA_0060640 Suppresses TGF-β2-Induced Proliferation, Motility and EMT in Human Lens Epithelium Cells by Targeting miR-214-3p and Collagen Type I alpha2 Chain

BACKGROUND

Circular RNA (circRNA) is a novel star factor in the research of ocular diseases including cataract and the most common postoperative complication posterior capsule opacification (PCO). Hsa_circRNA_0060640 (circ_0060640) is an age-related cataract-related circRNA. However, its role in cataractogenesis is unrevealed yet.

METHODS

PCO in vitro model was established in human lens epithelium cells (hLECs) induced by transforming growth factor-beta2 (TGF-β2). RNA and protein expressions were respectively detected by quantitative PCR and western blotting. Direct interaction between two RNAs was predicted by Starbase tool and confirmed by dual-luciferase reporter assay. MTS and EdU assays measured cell proliferation; Transwell, starch wound and western blotting assays evaluated cell motility and epithelial-mesenchymal transition (EMT).

RESULTS

Circ_0060640 expression is higher in anterior lens capsule tissues from human cataractous eyes and TGF-β2-stimulated hLECs cells line SRA01/04. RNA interference of circ_0060640 could prevent SRA01/04 cells from TGF-β2-induced cell proliferation, migration and invasion, accompanied with decreased N-cadherin and α-smooth muscle actin and increased E-cadherin. Mechanistically, circ_0060640 directly controls microRNA (miR)-214-3p expression and then regulates gene expression of collagen type I alpha2 chain (COL1A2). Notably, COL1A2 inhibition is underlying the protective role of circ_0060640 silencing and miR-214-3p ectopic expression in TGF-β2-stimulated SRA01/04 cells.

CONCLUSION

Circ_0060640 is a novel cataract-related gene and its silencing could block TGF-β2-evoked hLECs proliferation, motility and EMT in vitro via targeting miR-214-3p-COL1A2 axis. Therefore, targeting circ_0060640 via RNA interference might be a treatment strategy for PCO development.

LncRNA GAS5 regulates migration and epithelial-to-mesenchymal transition in lens epithelial cells via the miR-204-3p/TGFBR1 axis

Diabetic cataract (DC) is a major ocular complication secondary to diabetes mellitus. The epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is an important event in DC progression. Long non-coding RNAs (lncRNAs) and microRNAs are involved in various biological processes and disorders. The aim of this study was to investigate the roles of lncRNA growth arrest-specific transcript 5 (GAS5) and microRNA-204-3p (miR-204-3p) deregulation in the pathogenic mechanism of high glucose (HG)-stimulated LECs. The results show that GAS5 was up-regulated, whereas miR-204-3p was down-regulated in anterior lens capsule tissues of DC patients and in HG-treated LECs compared to their controls, respectively. Functional experiments suggest that the lentivirus-mediated depletion of GAS5, as well as overexpression of miR-204-3p, suppressed migration and EMT in HG-treated LECs. Further mechanistic studies revealed that lncRNA GAS5/miR-204-3p/type 1 receptor of transforming growth factor-beta (TGFBR1) has a regulatory role in the process. Collectively, we demonstrated that dysregulation of GAS5 affects lens epithelial cell migration and EMT under HG conditions via the miR-204-3p/TGFBR1 axis. The current findings may provide new insights into the molecular mechanisms of DC development.

Curcumin suppresses TGF-β2-induced proliferation, migration, and invasion in lens epithelial cells by targeting KCNQ1OT1/miR-377-3p/COL1A2 axis in posterior capsule opacification

BACKGROUND

Posterior capsule opacification (PCO) is a common complication after cataract surgery, which can lead to secondary loss of vision. Curcumin has been reported to play a suppressive role in PCO progression, and the potential molecular mechanism was explored in this study.

METHODS

Cell viability and proliferation were analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and 5-Ethynyl-2'-deoxyuridine (EdU) assay. Transwell assay and wound healing assay were performed to assess cell invasion and migration abilities. Western blot assay and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were conducted to measure the expression of proteins and RNAs. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to confirm the interaction between microRNA-377-3p (miR-377-3p) and KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) or collagen type I alpha 2 chain (COL1A2).

RESULTS

Curcumin dose-dependently alleviated transforming growth factor-β2 (TGF-β2)-induced proliferation, migration, and invasion in SRA01/04 cells. KCNQ1OT1 was up-regulated in PCO patients and TGF-β2-induced SRA01/04 cells. Curcumin-induced protective effects in TGF-β2-induced SRA01/04 cells were largely overturned by KCNQ1OT1 overexpression. KCNQ1OT1 directly interacted with miR-377-3p and negatively regulated its expression. miR-377-3p silencing overturned Curcumin-mediated protective effects in SRA01/04 cells upon TGF-β2 treatment. miR-377-3p directly interacted with the 3' untranslated region (3'UTR) of COL1A2. COL1A2 overexpression largely counteracted KCNQ1OT1 silencing-induced effects in TGF-β2-stimulated SRA01/04 cells. KCNQ1OT1 could up-regulate COL1A2 expression by sponging miR-377-3p in SRA01/04 cells.

CONCLUSION

In conclusion, Curcumin suppressed TGF-β2-induced malignant changes in lens epithelial cells by targeting KCNQ1OT1/miR-377-3p/COL1A2 axis.

TRPM7 Elicits Proliferation and Differentiation of Human Lens Epithelial Cells through the TGF-β/Smad Pathways

Epithelial-mesenchymal transition (EMT) plays a crucial role in the development of cataract. This study aimed to explore the effects of TRPM7 on the proliferation and differentiation of human lens epithelial cells. TRPM7 was over-expressed in LECs treated with TGF-β2. Down-regulation of TRPM7 attenuated the increase in cell viability and cell proliferation induced by TGF-β2. The LEC migration induced by TGF-β2 was also repressed by down-regulation of TRPM7. Epithelial-specific protein E-cadherin was up-regulated through knock-down of TRPM7. EMT-specific proteins, α-SMA, fibronectin and vimentin, were down-regulated through knockdown of TRPM7. Moreover, phosphorylation of Smad2 and Smad3 was also prevented by inhibition of TRPM7. Therefore, TRPM7 elicited LEC proliferation and EMT through enhancing activation of the TGF-β/Smad pathways, implying a new therapeutic target for cataract.

Tight junction protein 1 promotes vasculature remodeling via regulating USP2/TWIST1 in bladder cancer

Bladder cancer (BLCA) is the most common malignant tumor of the urinary system and is characterized by high metastatic rates and poor prognosis. The expression of tight junction protein 1 (TJP1) is associated with bladder cancer invasion; however, the mechanism by which TJP1 affects vasculature remodeling remains unknown. In this study, we found that TJP1 expression correlated with tumor angiogenesis and poor overall survival in clinical samples. Furthermore, TJP1 overexpression promoted tumor angiogenesis in BLCA cells and stimulated recruitment of macrophages to tumors by upregulating CCL2 expression. Mechanistically, TJP1 interacted with TWIST1 and enhanced the transcriptional activity of CCL2. The impairment of tumor angiogenesis caused by knockdown of TJP1 was dramatically rescued by overexpression of TWIST1. Furthermore, TJP1 recruited USP2, which deubiquitinated TWIST1, thereby protecting TWIST1 from proteasome-mediated protein degradation. In conclusion, our results suggest that TJP1 controls angiogenesis in BLCA via TWIST1-dependent regulation of CCL2. We demonstrate that TJP1 functions as a scaffold for the interaction between USP2 and TWIST1 and this may provide potential therapeutic targets in bladder cancer.

The local wound environment is a key determinant of the outcome of TGFβ signaling on the fibrotic response of CD44+ leader cells in an ex vivo post-cataract-surgery model

The cytokine transforming growth factor beta (TGFβ) has a role in regulating the normal and pathological response to wound healing, yet how it shifts from a pro-repair to a pro-fibrotic function within the wound environment is still unclear. Using a clinically relevant ex vivo post-cataract surgery model that mimics the lens fibrotic disease posterior capsule opacification (PCO), we investigated the influence of two distinct wound environments on shaping the TGFβ-mediated injury response of CD44⁺ vimentin-rich leader cells. The substantial fibrotic response of this cell population occurred within a rigid wound environment under the control of endogenous TGFβ. However, TGFβ was dispensable for the role of leader cells in wound healing on the endogenous basement membrane wound environment, where repair occurs in the absence of a major fibrotic outcome. A difference between leader cell function in these distinct environments was their cell surface expression of the latent TGFβ activator, αvβ3 integrin. This receptor is exclusively found on this CD44⁺ cell population when they localize to the leading edge of the rigid wound environment. Providing exogenous TGFβ to bypass any differences in the ability of the leader cells to sustain activation of TGFβ in different environments revealed their inherent ability to induce pro-fibrotic reactions on the basement membrane wound environment. Furthermore, exposure of the leader cells in the rigid wound environment to TGFβ led to an accelerated fibrotic response including the earlier appearance of pro-collagen + cells, alpha smooth muscle actin (αSMA)+ myofibroblasts, and increased fibrotic matrix production. Collectively, these findings show the influence of the local wound environment on the extent and severity of TGFβ-induced fibrotic responses. These findings have important implications for understanding the development of the lens fibrotic disease PCO in response to cataract surgery wounding.

αVβ8 integrin targeting to prevent posterior capsular opacification

Fibrotic posterior capsular opacification (PCO), a major complication of cataract surgery, is driven by transforming growth factor–β (TGF-β). Previously, αV integrins were found to be critical for the onset of TGF-β–mediated PCO in vivo; however, the functional heterodimer was unknown. Here, β8 integrin–conditional knockout (β8ITG-cKO) lens epithelial cells (LCs) attenuated their fibrotic responses, while both β5 and β6 integrin–null LCs underwent fibrotic changes similar to WT at 5 days post cataract surgery (PCS). RNA-Seq revealed that β8ITG-cKO LCs attenuated their upregulation of integrins and their ligands, as well as known targets of TGF-β–induced signaling, at 24 hours PCS. Treatment of β8ITG-cKO eyes with active TGF-β1 at the time of surgery rescued the fibrotic response. Treatment of WT mice with an anti-αVβ8 integrin function blocking antibody at the time of surgery ameliorated both canonical TGF-β signaling and LC fibrotic response PCS, and treatment at 5 days PCS, after surgically induced fibrotic responses were established, largely reversed this fibrotic response. These data suggest that αVβ8 integrin is a major regulator of TGF-β activation by LCs PCS and that therapeutics targeting αVβ8 integrin could be effective for fibrotic PCO prevention and treatment.

Bilateral Anterior Subcapsular Cataract Development Following Initiation of Enfortumab Vedotin

Enfortumab vedotin is an antibody–drug conjugate that was recently granted accelerated US Food and Drug Administration approval for the treatment of locally advanced or metastatic urothelial cancer. Early clinical trials identified blurry vision, increased lacrimation and other events associated with dry eye as potential side effects. We report a case of bilateral anterior subcapsular cataract development following initiation of enfortumab vedotin. Enfortumab vedotin is not previously known to cause cataract development or progression and, thus, our patient’s presentation may reflect the first report of an undocumented adverse effect of this novel agent.

Insights into Bone Morphogenetic Protein-(BMP-) Signaling in Ocular Lens Biology and Pathology

Bone morphogenetic proteins (BMPs) are a diverse class of growth factors that belong to the transforming growth factor-beta (TGFβ) superfamily. Although originally discovered to possess osteogenic properties, BMPs have since been identified as critical regulators of many biological processes, including cell-fate determination, cell proliferation, differentiation and morphogenesis, throughout the body. In the ocular lens, BMPs are important in orchestrating fundamental developmental processes such as induction of lens morphogenesis, and specialized differentiation of its fiber cells. Moreover, BMPs have been reported to facilitate regeneration of the lens, as well as abrogate pathological processes such as TGFβ-induced epithelial-mesenchymal transition (EMT) and apoptosis. In this review, we summarize recent insights in this topic and discuss the complexities of BMP-signaling including the role of individual BMP ligands, receptors, extracellular antagonists and cross-talk between canonical and non-canonical BMP-signaling cascades in the lens. By understanding the molecular mechanisms underlying BMP activity, we can advance their potential therapeutic role in cataract prevention and lens regeneration.

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.

Whole mount staining of lenses for visualization of lens epithelial cell proteins

Whole mount imaging of the lens allows for high spatial resolution visualization of lens epithelial structures by using small molecule fluorescent probes. However, the visualization of specific proteins in lens epithelial cells within whole lenses remains a challenge as the capsule that surrounds the lens does not allow penetration of antibodies. Here we describe a whole mount imaging method that allows us to overcome this challenge by digesting the lens capsules of paraformaldehyde fixed lenses using collagenase. This method enables the penetration of antibodies for effective visualization of proteins in the epithelium of whole lenses.•

A limitation to lens whole mount imaging is the ability to visualize specific proteins as the collagen capsule surrounding the lens impedes the penetration of antibodies

•

This protocol helps overcome this limitation by a light collagenase digestion of the capsule of fixed lenses prior to immunostaining

•

This method allows for the imaging of specific proteins in the epithelium of the whole lens tissue

Mutation of the TRPM3 cation channel underlies progressive cataract development and lens calcification associated with pro-fibrotic and immune cell responses

Transient-receptor-potential cation channel, subfamily M, member 3 (TRPM3) serves as a polymodal calcium sensor in diverse mammalian cell-types. Mutation of the human TRPM3 gene (TRPM3) has been linked with inherited forms of early-onset cataract with or without other eye abnormalities. Here, we have characterized the ocular phenotypes of germline "knock-in" mice that harbor a human cataract-associated isoleucine-to-methionine mutation (p.I65M) in TRPM3 (Trpm3-mutant) compared with germline "knock-out" mice that functionally lack TRPM3 (Trpm3-null). Despite strong expression of Trpm3 in lens epithelial cells, neither heterozygous (Trpm3^+/- ) nor homozygous (Trpm3^-/- ) Trpm3-null mice developed cataract; however, the latter exhibited a mild impairment of lens growth. In contrast, homozygous Trpm3-M/M mutants developed severe, progressive, anterior pyramid-like cataract with microphthalmia, whereas heterozygous Trpm3-I/M and hemizygous Trpm3-M/- mutants developed anterior pyramidal cataract with delayed onset and progression-consistent with a semi-dominant lens phenotype. Histochemical staining revealed abnormal accumulation of calcium phosphate-like deposits and collagen fibrils in Trpm3-mutant lenses and immunoblotting detected increased αII-spectrin cleavage products consistent with calpain hyper-activation. Immunofluorescent confocal microscopy of Trpm3-M/M mutant lenses revealed fiber cell membrane degeneration that was accompanied by accumulation of alpha-smooth muscle actin positive (α-SMA+ve) myofibroblast-like cells and macrosialin positive (CD68+ve) macrophage-like cells. Collectively, our mouse model data support an ocular disease association for TRPM3 in humans and suggest that (1) Trpm3 deficiency impaired lens growth but not lens transparency and (2) Trpm3 dysfunction resulted in progressive lens degeneration and calcification coupled with pro-fibrotic (α-SMA+ve) and immune (CD68+ve) cell responses.

Transforming growth factor-β2-mediated mesenchymal transition in lens epithelial cells is repressed in the absence of RAGE

Transforming growth factor-β2 (TGFβ2)-mediated epithelial to mesenchymal transition (EMT) in lens epithelial cells (LECs) has been implicated in fibrosis associated with secondary cataracts. In this study, we investigated whether the receptor for advanced glycation end products (RAGE) plays a role in TGFβ2-mediated EMT in LECs. Unlike in the LECs from wild-type mice, TGFβ2 failed to elicit an EMT response in LECs from RAGE knockout mice. The lack of RAGE also diminished TGFβ2-mediated Smad signaling. In addition, treatment with TGFβ2 increased IL-6 levels in LECs from wild-type mice but not in those from RAGE knockout mice. Treatment of human LECs with the RAGE inhibitor FPS-ZM1 reduced TGFβ2-mediated Smad signaling and the EMT response. Unlike that in wild-type lenses, the removal of fiber cell tissue in RAGE knockout lenses did not result in elevated levels of α-smooth muscle actin (α-SMA), fibronectin (FN), and integrin β1 in capsule-adherent LECs. Taken together, these results suggest that TGFβ2 signaling is intricately linked to RAGE. Targeting RAGE could be explored as a therapeutic strategy against secondary cataracts.

Immune cells in lens injury repair and fibrosis

Immune cells, both tissue resident immune cells and those immune cells recruited in response to wounding or degenerative conditions, are essential to both the maintenance and restoration of homeostasis in most tissues. These cells are typically provided to tissues by their closely associated vasculatures. However, the lens, like many of the tissues in the eye, are considered immune privileged sites because they have no associated vasculature. Such absence of immune cells was thought to protect the lens from inflammatory responses that would bring with them the danger of causing vision impairing opacities. However, it has now been shown, as occurs in other immune privileged sites in the eye, that novel pathways exist by which immune cells come to associate with the lens to protect it, maintain its homeostasis, and function in its regenerative repair. Here we review the discoveries that have revealed there are both innate and adaptive immune system responses to lens, and that, like most other tissues, the lens harbors a population of resident immune cells, which are the sentinels of danger or injury to a tissue. While resident and recruited immune cells are essential elements of lens homeostasis and repair, they also become the agents of disease, particularly as progenitors of pro-fibrogenic myofibroblasts. There still remains much to learn about the function of lens-associated immune cells in protection, repair and disease, the knowledge of which will provide new tools for maintaining the core functions of the lens in the visual system.