Experimental models for posterior capsule opacification research

Resveratrol Inhibits Wound Healing and Lens Fibrosis: A Putative Candidate for Posterior Capsule Opacification Prevention

Purpose

Posterior capsule opacification (PCO) is a common complication of cataract surgery. In addition to improved surgical methods and IOL designs, it is likely additional agents will be needed to improve patient outcomes. Presently no pharmacological agent is in clinical use to prevent PCO. Here we investigate the putative ability of resveratrol (RESV), a naturally occurring polyphenol, as a therapeutic agent.

Methods

The human lens epithelial cell line FHL124, a human lens capsular bag model, and central anterior epithelium were used as experimental systems. Standard culture was in 5% fetal calf serum Eagle's minimum essential medium; 10 ng/mL transforming growth factor-β2 (TGFβ2) was used to induce fibrotic changes. A scratch wound assay was used to measure cell migration and the patch assay was used to assess matrix contraction by FHL124 cells. Protein expression was assessed by immunocytochemistry and Western blot and gene expression by quantitative RT-PCR. In capsular bags, cell growth across the posterior lens capsule, capsular wrinkling, and epithelial-to-mesenchymal transition were determined by image analysis.

Results

In FHL124 cells, addition of 30 μM RESV significantly impeded cell migration in a wound-healing assay. RESV significantly inhibited TGFβ2-induced expression of the myofibroblast marker alpha-smooth muscle actin (α-SMA) at both the message and protein levels, as well as significantly inhibiting matrix contraction induced by TGFβ2. In human capsular bags, 30 μM RESV significantly inhibited cell growth. TGFβ2-induced α-SMA expression and capsular wrinkling were also significantly inhibited by RESV treatment. RESV significantly suppressed expression of TGFβ2-induced genes associated with fibrotic disease, including matrix metalloproteinase-2 in FHL124 cells, capsular bags, and central anterior epithelium.

Conclusions

RESV can counter PCO-related physiological events in two human lens model systems. RESV therefore has the potential to be used as a candidate agent for the prevention of PCO, which in turn could benefit millions of cataract patients.

Capsular fibrosis: a review of prevention methods and management

Opacification of the posterior capsule caused by residual lens epithelial cells (LEC) is still the most frequent long-term complication of cataract surgery. Beside the opacification of the visual axis with posterior capsule opacification (PCO), resulting in a decrease in visual function, fibrotic changes may also have a mechanical effect on intraocular lens (IOL) position such as axial shift, decentration, tilt and capsule striae. In this article, two types of capsular fibrosis are explored, on the one hand the anterior capsule fibrosis and on the other hand PCO. Results from clinical trials concerning their causes, natural course, incidence, influencing factors and possible methods of prophylaxis are presented.

Endoplasmic reticulum stress regulates epithelial‑mesenchymal transition in human lens epithelial cells

Epithelial‑to‑mesenchymal transition (EMT) of human lens epithelial cells (HLECs) serve an important role in cataract formation. The endoplasmic reticulum stress response (ER stress) has been demonstrated to regulate EMT in a number of tissues. The aim of the present study was to demonstrate the role of ER stress on EMT in HLECs. HLECs were treated with tunicamycin (TM) or thapsigargin (TG) to disturb ER homeostasis, and 4‑phenylbutyric acid (PBA) or sodium tauroursodeoxycholate (TUDCA) to restore ER homeostasis. Cell morphology was evaluated after 24 h. The long axis and aspect ratio of the cells were analyzed using ImageJ software. The results demonstrated that HLECs adopted an elongated morphology following treatment with TG, and the cellular aspect ratio increased. However, this morphological change was not observed following combination treatment with TG and PBA. Western blot analysis and immunofluorescence staining were used to measure the protein expression levels. A wound‑healing assay was performed to evaluate cell migration. Treatment with TM or TG increased the expression of the ER stress markers glucose‑regulated protein 78, phosphorylated eukaryotic initiation factor 2α, activating transcription factor (ATF)6, ATF4 and inositol‑requiring protein 1α and the EMT markers fibronectin, vimentin, α‑smooth muscle actin and neural cadherin. Furthermore, treatment with TM or TG decreased the expression of the epithelial cell marker epithelial cadherin and enhanced cell migration, which effects were inhibited following treatment with PBA or TUDCA. These results indicates that enhanced ER stress induced EMT and subsequently increased cell migration in HLECs in vitro.

Lysyl hydroxylase 3 is required for normal lens capsule formation and maintenance of lens epithelium integrity and fate

Lens abnormalities are a major cause of reduced vision and blindness. One mechanism that can lead to reduced lens transparency, i.e. cataract, is abnormal behavior of lens epithelial cells (LECs), the precursors of the transparent lens fiber cells. Here we describe a zebrafish mutation causing the embryonic lens epithelium to generate cellular masses comprising partially differentiated lens fiber cells. We identify the mutant gene as plod3, which encodes for Lysyl hydroxylase 3 (Lh3), an enzyme essential for modification of collagens, including Collagen IV, a main component of the lens capsule. We show that plod3-deficient lenses have abnormal lens epithelium from an early developmental stage, as well as abnormal lens capsules. Subsequently, upregulation of TGFβ signaling takes place, which drives the formation of lens epithelial cellular masses. We identify a similar phenotype in Collagen IVα5-deficient embryos, suggesting a key role for the defective lens capsule in the pathogenesis. We propose that plod3 and col4a5 mutant zebrafish can serve as useful models for better understanding the biology of LECs during embryonic development and in formation of lens epithelium-derived cataract.

Use of Human Pluripotent Stem Cells to Define Initiating Molecular Mechanisms of Cataract for Anti-Cataract Drug Discovery

Cataract is a leading cause of blindness worldwide. Currently, restoration of vision in cataract patients requires surgical removal of the cataract. Due to the large and increasing number of cataract patients, the annual cost of surgical cataract treatment amounts to billions of dollars. Limited access to functional human lens tissue during the early stages of cataract formation has hampered efforts to develop effective anti-cataract drugs. The ability of human pluripotent stem (PS) cells to make large numbers of normal or diseased human cell types raises the possibility that human PS cells may provide a new avenue for defining the molecular mechanisms responsible for different types of human cataract. Towards this end, methods have been established to differentiate human PS cells into both lens cells and transparent, light-focusing human micro-lenses. Sensitive and quantitative assays to measure light transmittance and focusing ability of human PS cell-derived micro-lenses have also been developed. This review will, therefore, examine how human PS cell-derived lens cells and micro-lenses might provide a new avenue for development of much-needed drugs to treat human cataract.

Histological comparison of in vitro and in vivo development of peripheral posterior capsule opacification in human donor tissue

In order to study the mechanisms involved in the development of posterior capsule opacification (PCO) we compared in vivo developed PCO with PCO formed in tissue culture with focus on the periphery of the lens capsule to evaluate lens regeneration potential. We studied three human tissue groups: Cultured lens capsules after mock cataract surgery (n = 6, 30 days), lens capsules from donors that had previously undergone cataract surgery (IOL capsules) (n = 12) and intact lenses (n = 6). All samples were stained with Vimentin, alpha Smooth Muscle Actin, Picro Sirius Red (for collagen) and Paired box protein (Pax6). We found that cultured capsules and less developed IOL capsules consisted mainly of monolayers of mesenchymal cells, while more developed IOL capsules, contained lens epithelial cells (LECs), globular cells and lens fiber cells. Many IOL capsule samples expressed collagen I and III in areas where cells were in contact with the IOL. Pax6 had a similar dispersed distribution in less developed IOL capsules and cultured capsules, while more developed IOL capsules and intact lenses, concentrated Pax6 in LECs at the equatorial lens bow. The similarities between cultured capsules and less developed IOL capsules indicate that our in vitro developed PCO is comparable to early in vivo developed PCO. The similar morphology of more developed IOL capsules and intact lenses seems to indicate an attempt at lens regeneration.

Long-term prevention of capsular opacification after lens-refilling surgery in a rabbit model

Purpose

To reduce capsular opacification by a peri‐surgical treatment of the lens capsule with drugs in an in vivo rabbit model. Lens‐refilling surgery is a potential therapeutic intervention to treat patients with a cataract lens. The lens material is replaced with an injectable (bio)polymer that retains the natural mechanical and optical lens properties, therewith allowing accommodation. The occurrence of capsular opacification mediated by lens epithelial cells negatively affects accommodation and vision and should be avoided in this lens restoration approach.

Methods

An in vivo rabbit animal model was used with lens replacement with a silicone‐based gel‐like polymer and concurrent treatment of the lens epithelium with drugs. A case‐study approach was applied as both drug combinations and implantation times were varied. The following drugs were investigated for their potential to prevent capsular opacification long‐term: actinomycin D, methotrexate, paclitaxel and Tween‐20. All were administered in a hyaluronic acid vehicle. The rabbits were clinically followed for periods up to 4 years postimplantation. Eyes, corneas and lenses were analysed post‐mortem using MRI and confocal microscopy.

Results

Treatment combinations containing actinomycin D generally led to the least appearance of capsular fibrosis. The use of Tween‐20 or paclitaxel without actinomycin D resulted in much earlier and pronounced fibrotic responses. The aspect of capsular opacification was highly variable in individual animals. Application of the drugs in a hyaluronic acid vehicle appeared to be a safe method that spared the corneal endothelium.

Conclusion

The feasibility of long‐term prevention of fibrosis over a period of more than 4 years has been demonstrated in lens refilling in the rabbit model.

An In Vitro Human Lens Capsular Bag Model Adopting a Graded Culture Regime to Assess Putative Impact of IOLs on PCO Formation

Purpose

To develop a culture regime for the in vitro human lens capsular bag model that better reflects clinical events following cataract surgery and to use this refined model to evaluate the putative impact of IOLs on PCO formation.

Methods

Capsulorhexis and lens extraction were performed on human donor eyes to generate capsular bags attached to the ciliary body by the zonules. Preparations were secured by pinning the ciliary body to a silicone ring and maintaining in 6 mL serum-free EMEM for 28 days or in a graded culture system (days 1-3, 5% human serum and 10 ng/mL TGFβ2; days 4-7, 2% human serum and 1 ng/mL TGFβ2; days 8-14, 1% human serum and 0.1 ng/mL TGFβ2; days 15-28, serum-free EMEM), which better mimics clinical changes. Preparations were monitored with phase-contrast and modified-dark-field microscopy. Cell coverage and light scatter were quantified using image analysis software. The transdifferentiation marker, α-SMA and matrix component, fibronectin were assessed by immunocytochemistry. To assess IOLs in the model, Alcon Acrysof or Hoya Vivinex IOLs were implanted in match-paired capsular bags.

Results

Match-paired experiments showed that graded culture enhanced growth, facilitated matrix contraction, increased transdifferentiation, and promoted matrix deposition relative to serum-free culture. The graded culture protocol was applied to match-paired bags implanted with a Hoya Vivinex or an Alcon Acrysof IOL. The Vivinex demonstrated a lag in growth across the posterior capsule. However, by day 28, coverage was similar, but light-scatter was greater with Acrysof implanted. Cell growth on the Acrysof IOL anterior surface was significantly greater than Vivinex.

Conclusions

The graded culture human capsular bag model serves as an excellent system to evaluate and develop intraocular lenses. The Hoya Vivinex IOL showed an overall better level of performance against postsurgical wound healing and PCO than the Alcon Acrysof using this model.

LncRNA FEZF1-AS1 Promotes TGF-β2-Mediated Proliferation and Migration in Human Lens Epithelial Cells SRA01/04

Posterior capsule opacification (PCO) is a common complication after cataract surgery attributed to the proliferation and migration of postoperative residual lens epithelial cells (LECs). The long noncoding RNA (lncRNA) FEZ family zinc finger 1 antisense RNA 1 (FEZF1-AS1) promotes the proliferation and migration of multiple types of cancer cells. Here, we discovered that FEZF1-AS1 is markedly upregulated in TGF-β2-treated SRA01/04 cells. In addition, the proliferation and migration of SRA01/04 cells were enhanced following TGF-β2 treatment. FEZF1-AS1 knockdown inhibited the TGF-β2-induced proliferation and migration of SRA01/04 cells. Accordingly, FEZF1-AS1 overexpression promoted the TGF-β2-induced proliferation and migration of SRA01/04 cells. Finally, FEZF1-AS1 upregulated TGF-β2-induced SRA01/04 cell proliferation and migration via boosting FEZF1 protein levels. Our findings indicate that the dysregulation of FEZF1-AS1 participates in the TGF-β2-induced proliferation and migration of human lens epithelial cells (HLECs), which might be achieved, at least in part, through the induction of FEZF1 expression.

Anti-tumor Drug THZ1 Suppresses TGFβ2-mediated EMT in Lens Epithelial Cells via Notch and TGFβ/Smad Signaling Pathway

Selective covalent CDK7 inhibitor THZ1 is a promising potential anti-tumor drug in many kinds of cancers. Epithelial-mesenchymal Transition (EMT) is highly related to cancer initiation, development, invasion and metastasis and other pathogenesis processes. We treated cancer cell line Hela229 and three retinoblastoma cell lines so-RB50, WERI-Rb-1, Y79 with gradient concentration of THZ1, and found that THZ1 could inhibit cell viability and EMT, suggesting that THZ1 may be a promising drug for human cervical cancer and retinoblastoma treatment. Our results verified the role of THZ1 in EMT for the first time, however, the mechanism needs further study. Here we report that THZ1 suppresses the TGFβ2 induced EMT in human SRA01/04 lens epithelial cells (LECs), rabbit primary lens epithelial cells, and whole rat lens culture semi-in vivo model. RNA-sequencing and KEGG analysis revealed that the THZ1 inhibits EMT by down-regulating phosphorylate Smad2 and Notch signaling pathway. On the other hand, we found that THZ1 could strongly inhibit LECs proliferation through G2/M phase arrest as well as attenuating of MAPK, PI3K/AKT signaling pathway. Our results uncovered the function and underlying mechanism of THZ1 in regulation of EMT, which provides a new perspective of the anti-tumor effect by THZ1 and may offer a novel treatment for PCO.

Epithelial-Mesenchymal Transdifferentiation in Pediatric Lens Epithelial Cells

Purpose

Posterior capsule opacification (PCO) is a complication after cataract surgery, particularly in children. Epithelial-mesenchymal transition (EMT) of lens epithelial cells, mediated by transforming growth factor beta (TGFβ), contributes to PCO. However, its pathogenesis in children is poorly understood. We correlated cell growth in culture with patient characteristics, studied gene expression of pediatric lens epithelial cells (pLEC), and examined the effects of TGFβ-2 on these cells in vitro.

Methods

Clinical characteristics of children with cataracts correlated with growth behavior of pLEC in vitro. mRNA expression of epithelial (αB-crystallin, connexin-43) and mesenchymal (αV-integrin, α-smooth muscle actin, collagen-Iα2, fibronectin-1) markers was quantified in pLEC and in cell line HLE-B3 in the presence and absence of TGFβ-2.

Results

Fifty-four anterior lens capsules from 40 children aged 1 to 180 months were obtained. Cell outgrowth occurred in 44% of the capsules from patients ≤ 12 months and in 33% of capsules from children aged 13 to 60 months, but in only 6% of capsules from children over 60 months. TGFβ-2 significantly upregulated expression of αB-crystallin (HLE-B3), αV-integrin (HLE-B3), collagen-Iα2, and fibronectin-1 (in pLEC and HLE-B3 cells).

Conclusions

Patient characteristics correlated with growth behavior of pLEC in vitro, paralleling a higher clinical incidence of PCO in younger children. Gene expression profiles of pLEC and HLE-B3 suggest that upregulation of αV-integrin, collagen-Iα2, and fibronectin-1 are involved in EMT.

Lens Epithelial Cells Initiate an Inflammatory Response Following Cataract Surgery

Purpose

Lens epithelial cell (LEC) conversion to myofibroblast is responsible for fibrotic cataract surgery complications including posterior capsular opacification. While transforming growth factor beta (TGFβ) signaling is important, the mechanisms by which the TGFβ pathway is activated post cataract surgery (PCS) are not well understood.

Methods

RNA-seq was performed on LECs obtained from a mouse cataract surgery model at the time of surgery and 24 hours later. Bioinformatic analysis was performed with iPathwayGuide. Expression dynamics were determined by immunofluorescence.

Results

The LEC transcriptome is massively altered by 24 hours PCS. The differentially expressed genes included those important for lens biology, and fibrotic markers. However, the most dramatic changes were in the expression of genes regulating the innate immune response, with the top three altered genes exhibiting greater than 1000-fold upregulation. Immunolocalization revealed that CXCL1, S100a9, CSF3, COX-2, CCL2, LCN2, and HMOX1 protein levels upregulate in LECs between 1 hour and 6 hours PCS and peak at 24 hours PCS, while their levels sharply attenuate by 3 days PCS. This massive upregulation of known inflammatory mediators precedes the infiltration of neutrophils into the eye at 18 hours PCS, the upregulation of canonical TGFβ signaling at 48 hours PCS, and the infiltration of macrophages at 3 days PCS.

Conclusions

These data demonstrate that LECs produce proinflammatory cytokines immediately following lens injury that could drive postsurgical flare, and suggest that inflammation may be a major player in the onset of lens-associated fibrotic disease PCS.

Long Noncoding RNA MALAT1 Acts as a Competing Endogenous RNA to Regulate TGF-β2 Induced Epithelial-Mesenchymal Transition of Lens Epithelial Cells by a MicroRNA-26a-Dependent Mechanism

The aim of the present study was to characterize whether the long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)/miR-26a/Smad4 axis is involved in epithelial–mesenchymal transition (EMT) of lens epithelial cells (LECs). Primary human LECs were separated and cultured. Microarray analysis showed that a total of 568 lncRNAs are differentially expressed in primary HLECs in the presence of TGF-β2 and MALAT1 is mostly significantly dysregulated lncRNAs, which is increased by nearly 17-fold. In addition, upregulation of MALAT1 and downregulation of miR-26a were detected in human posterior capsule opacification (PCO) attached LECs and the LECs obtained from patients with anterior polar cataracts by quantitative RT-PCR (qRT-PCR). Next, our results showed that TGF-β2 induces overexpression of EMT markers in primary HLECs via a MALAT1-dependent mechanism. The mechanism is that MALAT1 negatively regulates miR-26a and miR-26a directly targets Smad4 by luciferase reporter assays and RNA-binding protein immunoprecipitation assay. In summary, TGF-β2 induces MALAT1 overexpression, which in turn MALAT1 acts as a ceRNA targeting Smad4 by binding miR-26a and promotes the progression of EMT of LECs.

Determination of trypan blue efficacy in the mitigation of ex vivo canine PCO formation

PURPOSE

To determine whether trypan blue (TB) reduces canine lens epithelial cell (LEC) or corneal endothelial cell (CEC) viability in vitro; if cell death is noted, to subsequently evaluate the molecular mechanism.

METHODS

Cellular viability was determined using a lactate dehydrogenase (LDH) assay. In TB-treated LECs, caspase 3/7 activity was assessed to evaluate apoptosis; autophagy was evaluated using immunoblotting against LC3 and p62. To evaluate the effects of TB on ex vivo posterior capsule opacification (PCO), following mock cataract surgery, lens capsules were treated with TB and subsequently maintained in culture to determine LEC migration and proliferation.

RESULTS

Following acute exposure, TB did not significantly reduce LEC or CEC viability at any of the concentrations tested. Increased caspase 3/7 activity was found in LEC cultures treated with TB for an extended period of time; no change in LC3 or p62 expression was noted. Ex vivo PCO formation was not significantly altered by TB treatment.

CONCLUSIONS

Acute exposure to TB did not reduce LEC or CEC viability, and only longer exposure to TB was able to initiate apoptosis. Treatment with intraocular TB at the time of cataract surgery is likely safe to the CECs but will not prevent PCO formation.

Fibrosis: Shared Lessons From the Lens and Cornea

Regenerative repair in response to wounding involves cell proliferation and migration. This is followed by the reestablishment of cell structure and organization and a dynamic process of remodeling and restoration of the injured cells' extracellular matrix microenvironment and the integration of the newly synthesized matrix into the surrounding tissue. Fibrosis in the lungs, liver, and heart can lead to loss of life and in the eye to loss of vision. Learning to control fibrosis and restore normal tissue function after injury repair remains a goal of research in this area. Here we use knowledge gained using the lens and the cornea to provide insight into how fibrosis develops and clues to how it can be controlled. The lens and cornea are less complex than other tissues that develop life‐threatening fibrosis, but they are well characterized and research using them as model systems to study fibrosis is leading toward an improved understanding of fibrosis. Here we summarize the current state of the literature and how it is leading to promising new treatments. Anat Rec, 2019. © 2019 The Authors. The Anatomical Record published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists.

Cataract in diabetes mellitus

Diabetes mellitus (DM) is a chronic systemic disease that has increases in prevalence over time. DM can affect all ocular structures, with cataract being the most common ocular complication. Cataract is the leading cause of blindness worldwide. Due to several mechanisms, there is an increased incidence of cataract formation in the diabetic population. Advancements in technology have now made cataract surgery a common and safe procedure. However, the diabetic population is still at risk of vision-threatening complications, such as diabetic macular edema (ME), postoperative ME, diabetic retinopathy progression, and posterior capsular opacification.

Aldose Reductase Inhibition Prevents Development of Posterior Capsular Opacification in an In Vivo Model of Cataract Surgery

Purpose

Cataract surgery is a procedure by which the lens fiber cell mass is removed from its capsular bag and replaced with a synthetic intraocular lens. Postoperatively, remnant lens epithelial cells can undergo an aberrant wound healing response characterized by an epithelial-to-mesenchymal transition (EMT), leading to posterior capsular opacification (PCO). Aldose reductase (AR) inhibition has been shown to decrease EMT markers in cell culture models. In this study, we aim to demonstrate that AR inhibition can attenuate induction of EMT markers in an in vivo model of cataract surgery.

Methods

A modified extracapsular lens extraction (ECLE) was performed on C57BL/6 wildtype, AR overexpression (AR-Tg), and AR knockout mice. Immunofluorescent staining for the myofibroblast marker α-smooth muscle actin (α-SMA), epithelial marker E-cadherin, and lens fiber cell markers αA-crystallin and Aquaporin 0 was used to characterize postoperative PCO. Quantitative reverse transcription PCR (qRT-PCR) was employed to quantify postoperative changes in α-SMA, vimentin, fibronectin, and E-cadherin. In a separate experiment, the AR inhibitor Sorbinil was applied postoperatively and qRT-PCR was used to assess changes in EMT markers.

Results

Genetic AR knockout reduced ECLE-induced upregulation of α-SMA and downregulation of E-cadherin. These immunofluorescent changes were mirrored quantitatively in changes in mRNA levels. Similarly, Sorbinil blocked characteristic postoperative EMT changes in AR-Tg mice. Interestingly, genetic AR knockout did not prevent postoperative induction of the lens fiber cell markers αA-crystallin and Aquaporin 0.

Conclusions

AR inhibition prevents the postoperative changes in EMT markers characteristic of PCO yet preserves the postoperative induction of lens fiber cell markers.

Proteome-transcriptome analysis and proteome remodeling in mouse lens epithelium and fibers

Epithelial cells and differentiated fiber cells represent distinct compartments in the ocular lens. While previous studies have revealed proteins that are preferentially expressed in epithelial vs. fiber cells, a comprehensive proteomics library comparing the molecular compositions of epithelial vs. fiber cells is essential for understanding lens formation, function, disease and regenerative potential, and for efficient differentiation of pluripotent stem cells for modeling of lens development and pathology in vitro. To compare protein compositions between the lens epithelium and fibers, we employed tandem mass spectrometry (2D-LC/MS) analysis of microdissected mouse P0.5 lenses. Functional classifications of the top 525 identified proteins into gene ontology categories by molecular processes and subcellular localizations, were adapted for the lens. Expression levels of both epithelial and fiber proteomes were compared with whole lens proteome and mRNA levels using E14.5, E16.5, E18.5, and P0.5 RNA-Seq data sets. During this developmental time window, multiple complex biosynthetic and catabolic processes generate the molecular and structural foundation for lens transparency. As expected, crystallins showed a high correlation between their mRNA and protein levels. Comprehensive data analysis confirmed and/or predicted roles for transcription factors (TFs), RNA-binding proteins (e.g. Carhsp1), translational apparatus including ribosomal heterogeneity and initiation factors, microtubules, cytoskeletal [e.g. non-muscle myosin IIA heavy chain (Myh9) and βB2-spectrin (Sptbn2)] and membrane proteins in lens formation and maturation. Our data highlighted many proteins with unknown functions in the lens that were preferentially enriched in epithelium or fibers, setting the stage for future studies to further dissect the roles of these proteins in fiber cell differentiation vs. epithelial cell maintenance. In conclusion, the present proteomic datasets represent the first mouse lens epithelium and fiber cell proteomes, establish comparative analyses of protein and RNA-Seq data, and characterize the major proteome remodeling required to form the mature lens fiber cells.

Application of Spectral Domain Optical Coherence Tomography to Objectively Evaluate Posterior Capsular Opacity In Vivo

Objectives

To objectively evaluate posterior capsular opacification (PCO) with RTVue-100 spectral domain-OCT and assess the agreement with the Pentacam system.

Methods

Sixty-seven eyes diagnosed with PCO were included. RTVue-100 SD-OCT was used to scan the IOL outline and PCO at horizontal and vertical meridians. PCO was also imaged with a Pentacam and slit-lamp photography system. With RTVue-100 SD-OCT, the PCO area, thickness, density, and objective scores were recorded and used to evaluate the severity of PCO at 3 mm and 5 mm diameter ranges of the IOL optic region. We assessed the correlation of visual acuity, PCO characteristics, and PCO scores. PCO scores acquired from RTVue-100 SD-OCT images were also compared with those from the Pentacam. Differences between pear-type and fibrosis-type PCOs were also compared using RTVue-100 SD-OCT cross-sectional images.

Results

The cross-sectional images of PCO acquired with RTVue-100 SD-OCT corresponded well to Pentacam and slit-lamp retroillumination images. IOL-posterior capsular space, area, thickness, and density of the proliferated and accumulated LECs could be clearly visualized and quantified with RTVue-100 SD-OCT. PCO scores were correlated with decreased visual acuity, which was in line with the outcomes using the Pentacam. Differences between the pear-type and fibrosis-type PCO were statistically significant; pear-type PCOs showed a wider and thicker opacification region with lower density compared with fibrosis-type PCOs.

Conclusion

RTVue-100 SD-OCT could be a powerful tool in PCO objective evaluation and classification. OCT could be used to visualize the morphology and outline of PCO. Thus, it could discriminate and quantify differences between different types of PCO. PCO scores seem to be a useful factor that could reliably reflect PCO severity.

Fibronectin regulates growth factor signaling and cell differentiation in primary lens cells

Lens epithelial cells are bound to the lens extracellular matrix capsule, of which laminin is a major component. After cataract surgery, surviving lens epithelial cells are exposed to increased levels of fibronectin, and so we addressed whether fibronectin influences lens cell fate, using DCDML cells as a serum-free primary lens epithelial cell culture system. We found that culturing DCDMLs with plasma-derived fibronectin upregulated canonical TGFβ signaling relative to cells plated on laminin. Fibronectin-exposed cultures also showed increased TGFβ signaling-dependent differentiation into the two cell types responsible for posterior capsule opacification after cataract surgery, namely myofibroblasts and lens fiber cells. Increased TGFβ activity could be identified in the conditioned medium recovered from cells grown on fibronectin. Other experiments showed that plating DCDMLs on fibronectin overcomes the need for BMP in fibroblast growth factor (FGF)-induced lens fiber cell differentiation, a requirement that is restored when endogenous TGFβ signaling is inhibited. These results demonstrate how the TGFβ-fibronectin axis can profoundly affect lens cell fate. This axis represents a novel target for prevention of late-onset posterior capsule opacification, a common but currently intractable complication of cataract surgery.

ERK1/2-mediated EGFR-signaling is required for TGFβ-induced lens epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) plays a critical role in the pathogenesis of fibrotic cataract. Transforming growth factor-beta (TGFβ) is a potent inducer of this fibrotic process in lens. Recent studies in cancer progression have shown that in addition to activating the canonical Smad signaling pathway, TGFβ can also transactivate the epidermal growth factor receptor (EGFR) to enhance invasive cell migration. The present study aims to elucidate the involvement of EGFR-signaling in TGFβ-induced EMT in LECs. Treatment with TGFβ2 induced transdifferentiation of LECs into myofibroblastic cells, typical of an EMT. TGFβ2 induced the phosphorylation of the EGFR and upregulation of Egfr and Hb-egf gene expression. Pharmacologic inhibition of EGFR-signaling using PD153035 inhibited TGFβ-induced EMT, including the upregulation of mesenchymal markers and downregulation of epithelial markers. Crosstalk between TGFβ2-induced EGFR and ERK1/2 was evident, with both pathways impacting on Smad2/3-signaling. Our finding that TGFβ2 transactivates downstream EGFR-signaling reveals a previously unknown mechanism in the pathogenesis of cataract. Understanding the complex interplay between divergent canonical and non-canonical signaling pathways, as well as downstream target genes involved in TGFβ-induced EMT, will enable the development of more effective targeted therapies in the pharmacological treatment of cataract.

The role of focal adhesion kinase in transforming growth factor-β2 induced migration of human lens epithelial cells

The migration of lens epithelial cells towards the posterior capsule is a key event in the development of posterior capsule opacification (PCO). Accumulating evidence has described crosstalk between growth factors and adhesive signaling pathways in wound healing and cell migration. The aim of the present study was to elucidate an aberrant transforming growth factor (TGF)‑β2 signaling pathway that regulated the migration of lens epithelial cells in the pathological context of PCO. The expression of fibronectin, focal adhesion kinase (FAK) and phosphorylated (p)‑FAK in HLE‑B3 cells following TGF‑β2 treatment was determined by western blot analysis and the expression of integrin α5β1 was detected by flow cytometry. Cell migration capacity was measured by wound healing and Transwell assays in the presence of 1,2,4,5‑tetraaminobenzene tetrahydrochloride, a selective FAK inhibitor, fibronectin small interfering RNA interference, arginylglycylaspartic acid peptides or α5β1‑integrin neutralizing antibodies. The 1,2,4,5‑tetraaminobenzene tetrahydrochloride was administered daily to 16 rabbits following cataract surgery. Fibronectin and TGF‑β expression were increased in the PCO group, demonstrated by immunofluorescence assays. PCO grading was conducted by slit‑lamp biomicroscopy and evaluation of posterior capsule opacification software. It was observed that TGF‑β2 promoted HLE‑B3 cell migration and upregulated fibronectin expression, which was followed by an increased phosphorylation of FAK. In addition, TGF‑β2 treatment and fibronectin surface coating significantly increased cell migration and FAK activation, which was inhibited by disrupting fibronectin‑integrin α5β1 interaction with the arginylglycylaspartic acid peptide, α5β1‑integrin neutralizing antibody or fibronectin depletion. Finally, suppression of FAK signaling by its inhibitor significantly decreased cell migration in vitro and attenuated PCO development in vivo. In summary, TGF‑β2 was indicated to promote the migration of lens epithelial cells through the TGF‑β2/fibronectin/integrin/FAK axis. Inhibition of FAK activity decreased TGF‑β2‑mediated cell migration in vitro and improved the symptoms of PCO in a rabbit model.

EGF-Mediated Overexpression of Myc Attenuates miR-26b by Recruiting HDAC3 to Induce Epithelial-Mesenchymal Transition of Lens Epithelial Cells

The previous study has demonstrated that epidermal growth factor (EGF) and EGF receptor (EGFR) signaling plays a critical role in the development of posterior capsule opacification (PCO) through regulating lens epithelial cells (LECs) proliferation. Recent studies have suggested that the residual LECs undergo proliferation and migration, and epithelial-mesenchymal transition (EMT) is the important cause of PCO formation after cataract surgery. EMT of LECs is considered to be playing a central role in the pathogenesis of PCO. In the present study, we investigated whether and how EGF may regulate EMT of LECs. First, we demonstrated that EGF and EGFR signaling induces Myc overexpression in primary human lens epithelial cells (HLECs). In turn, Myc overexpression could inhibit miR-26b by recruitment of HDAC3. Consequently, the downregulated expression of miR-26b increased the expression of EZH2 in primary HLECs. Mechanistically, miR-26b directly controls EZH2 expression by targeting its 3′-UTR in HLECs by luciferase reporter assays. Finally, we demonstrated that EGF induces the expression of EMT markers in primary HLECs via a miR-26b-dependent mechanism. In summary, EGF activated Myc and Myc overexpression inhibited miR-26b by recruitment of HDAC3, which in turn induced the expression of EZH2 and promoted the progression of EMT in HLECs.

In wound repair vimentin mediates the transition of mesenchymal leader cells to a myofibroblast phenotype

Following injury, mesenchymal repair cells are activated to function as leader cells that modulate wound healing. These cells have the potential to differentiate to myofibroblasts, resulting in fibrosis and scarring. The signals underlying these differing pathways are complex and incompletely understood. The ex vivo mock cataract surgery cultures are an attractive model with which to address this question. With this model we study, concurrently, the mechanisms that control mesenchymal leader cell function in injury repair within their native microenvironment and the signals that induce this same cell population to acquire a myofibroblast phenotype when these cells encounter the environment of the adjacent tissue culture platform. Here we show that on injury, the cytoskeletal protein vimentin is released into the extracellular space, binds to the cell surface of the mesenchymal leader cells located at the wound edge in the native matrix environment, and supports wound closure. In profibrotic environments, the extracellular vimentin pool also links specifically to the mesenchymal leader cells and has an essential role in signaling their fate change to a myofibroblast. These findings suggest a novel role for extracellular, cell-surface–associated vimentin in mediating repair-cell function in wound repair and in transitioning these cells to a myofibroblast phenotype.

Therapeutic potential of a dual mTORC1/2 inhibitor for the prevention of posterior capsule opacification: An in vitro study

Mammalian target of rapamycin (mTOR) serves a central role in regulating cell growth and survival, and has been demonstrated to be involved in the pathological progression of posterior capsule opacification (PCO). In the present study, the potency of PP242, a novel dual inhibitor of mTOR complex 1/2 (mTORC1/2), in the suppression of the growth of human lens epithelial cells (HLECs) was investigated. Using a Cell Counting Kit‑8 and a wound healing assay, it was demonstrated that PP242 inhibited the proliferation and migration of HLECs. In addition, western blot analysis indicated that PP242 completely inhibited mTORC1 and mTORC2 downstream signaling activities, whereas rapamycin only partially inhibited mTORC1 activity within LECs. Furthermore, PP242 treatment led to an upregulation of the expression levels of p53 and B cell lymphoma‑2 (Bcl‑2)‑associated X and downregulation of Bcl‑2. In addition, flow cytometric analysis demonstrated that PP242 induced the cell cycle arrest at the G0/G1 phase, which may have caused apoptosis and induced autophagy within the LECs. The results of the present study suggested that administration of PP242 may potentially offer a novel therapeutic approach for the prevention of PCO.

Further Enhancement of Intraocular Open-Capsule Devices for Prevention of Posterior Capsule Opacification

Purpose

We improve the intraocular open-capsule devices (IOCD) for the prevention of posterior capsule opacification (PCO).

Methods

A total of 45 New Zealand rabbit eyes were divided into six similar groups after crystalline lens evacuation. Each group was implanted with a hydrophilic intraocular lens (IOL) and a hydrophilic IOCD of different designs. In the first experiment (Part A), a square design ring with and without large apertures was compared to a round design ring without apertures. In the second experiment (Part B), a square design ring with large apertures was compared to square design IOCDs with small apertures of high and low density. PCO and Soemmering's ring were evaluated clinically, by the Miyake Apple view, and histologically. The results were compared to a control group of eyes implanted with a hydrophilic IOL only.

Results

All devices showed significant prevention of PCO and Soemmering's ring compared to the control group. Part A: the square design with apertures had the lowest level of peripheral lens epithelial cells proliferation (protrusions). Part B: modifying the size and density of the apertures had no influence on those protrusions.

Conclusions

The IOCD significantly reduced the rate of PCO and its precursor, Soemmering's ring. The rings with the square edges and apertures produced the best results. The study was underpowered to determine the influence of the apertures design.

Translational Relevance

The IOCD has the potential to prevent up to 80% of the PCO cases; the most common complication after cataract surgery. The design of the ring is important for its success.

Genetically Engineered Liposome-like Nanovesicles as Active Targeted Transport Platform

Ligand-targeted delivery of drug molecules to various types of tumor cells remains a major challenge in precision medicine. Inspired by the secretion process and natural cargo delivery functions of natural exosomes, biomimetic synthetic strategies are exploited to prepare biofunctionalized liposome-like nanovesicles (BLNs) that can artificially display a wide variety of targeting protein/peptide ligands and directly encapsulate medical agents for enhanced drug delivery. Here, as a proof of concept, genetically engineered BLNs, which display human epidermal growth factor (hEGF) or anti-HER2 Affibody as targeting moieties, are developed to, respectively, target two types of tumor cells. Notably, in comparison to synthetic liposomes covalently coupled with hEGF, it is demonstrated in this work that biosynthetically displayed hEGF ligands on BLNs possess higher biological activities and targeting capabilities. Additionally, treatments with doxorubicin-loaded BLNs displaying Affibody ligands exhibit much better antitumor therapeutic outcomes than clinically approved liposomal doxorubicin (Doxil) in HER2-overexpressing BT474 tumor xenograft models. These data suggest that BLN is suitable as a potent surrogate for conventional proteoliposomes or immunoliposomes as a result of excellent targeting capacities and facile production of BLNs.

EDIL3 depletion suppress epithelial-mesenchymal transition of lens epithelial cells via transforming growth factor β pathway

AIM

To study the effect of discoidin I-like domaincontaining protein 3 (EDIL3) depletion on the proliferation and epithelial-mesenchymal transition (EMT) in human lens epithelial cells (LECs).

METHODS

RNA interference was used to inhibit the expression of EDIL3 in human LECs in vitro. The morphology of cells was observed using an inverted microscope. Cell proliferation was assessed using EdU kit. Cell migration was investigated using Transwell chamber and EMT of LECs was assessed using confocal microscope and Western blotting. The transforming growth factor β (TGFβ) pathway was investigated using Western blotting.

RESULTS

The data showed that silencing EDIL3 expression changed LECs morphology and suppressed LECs proliferation (P<0.05) and migration (P<0.01). Furthermore, the result of Western blotting showed that EDIL3 depletion reduced the expression of α-smooth muscle actin (α-SMA) (P<0.001) and vimentin (P<0.01), while increased the expression of E-cadherin (P<0.001). EDIL3 depletion could suppress the phosphorylation of Smad2 (P<0.01) and Smad3 (P<0.01) and the activation of exracellular signal regulated kinase (ERK) (P<0.05).

CONCLUSION

The findings indicate that EDIL3 might participate in the proliferation and EMT in LECs via TGFβ pathway and may be a potential therapeutic target for the treatment of posterior capsule opacification.

Light-focusing human micro-lenses generated from pluripotent stem cells model lens development and drug-induced cataract in vitro

Cataracts cause vision loss and blindness by impairing the ability of the ocular lens to focus light onto the retina. Various cataract risk factors have been identified, including drug treatments, age, smoking and diabetes. However, the molecular events responsible for these different forms of cataract are ill-defined, and the advent of modern cataract surgery in the 1960s virtually eliminated access to human lenses for research. Here, we demonstrate large-scale production of light-focusing human micro-lenses from spheroidal masses of human lens epithelial cells purified from differentiating pluripotent stem cells. The purified lens cells and micro-lenses display similar morphology, cellular arrangement, mRNA expression and protein expression to human lens cells and lenses. Exposing the micro-lenses to the emergent cystic fibrosis drug Vx-770 reduces micro-lens transparency and focusing ability. These human micro-lenses provide a powerful and large-scale platform for defining molecular disease mechanisms caused by cataract risk factors, for anti-cataract drug screening and for clinically relevant toxicity assays.

Anterior lens capsule and epithelium thickness measurements using spectral-domain optical coherence tomography

Background

To investigate the anterior lens capsule and epithelium thickness (defined as anterior lens capsular complex: ALCC) in normal Chinese subjects using spectral-domian optical coherence tomography (SD-OCT) and examine the factors that may influence the ALCC, such as age, gender, pupil diameter (PD) and signal strength index (SSI).

Methods

A prospective observational case series. One-hundred-thirty-four normal subjects (134 eyes) were included. The ALCCs were determined manually via SD-OCT. Using the pupil center as a reference position, the central ALCC (CALCC), nasal 1-mm ALCC (NALCC), temporal 1-mm ALCC (TALCC) and PD were measured manually.

Results

The mean CALCC, NALCC and TALCC were 33 ± 6 μm, 36 ± 7 μm and 34 ± 6 μm, respectively. The NALCC was significantly thicker than the CALCC (P < .001) and TALCC (P < .001). Moreover, CALCC was significantly thinner than TALCC (P = 0.013). Age was positively correlated with the CALCC (r = 0.292, P < .001), NALCC (r = 0.400, P < .001) and TALCC (r = 0.521, P < .001). PD, gender and SSI were not significantly correlated with the three ALCC parameters.

Conclusions

The SD-OCT can be used to demonstrate the ALCC thickness, and age is positively correlated with the ALCC in the central, nasal and temporal sides.

Dual function of TGFβ in lens epithelial cell fate: implications for secondary cataract

The most common vision-disrupting complication of cataract surgery is posterior capsule opacification (PCO; secondary cataract). PCO is caused by residual lens cells undergoing one of two very different cell fates: either transdifferentiating into myofibroblasts or maturing into lens fiber cells. Although TGFβ has been strongly implicated in lens cell fibrosis, the factors responsible for the latter process have not been identified. We show here for the first time that TGFβ can induce purified primary lens epithelial cells within the same culture to undergo differentiation into either lens fiber cells or myofibroblasts. Marker analysis confirmed that the two cell phenotypes were mutually exclusive. Blocking the p38 kinase pathway, either with direct inhibitors of the p38 MAP kinase or a small-molecule therapeutic that also inhibits the activation of p38, prevented TGFβ from inducing epithelial-myofibroblast transition and cell migration but did not prevent fiber cell differentiation. Rapamycin had the converse effect, linking MTOR signaling to induction of fiber cell differentiation by TGFβ. In addition to providing novel potential therapeutic strategies for PCO, our findings extend the so-called TGFβ paradox, in which TGFβ can induce two disparate cell fates, to a new epithelial disease state.

Laser capsulotomy following cataract surgery: Comparing time to capsulotomy with implantation of two broadly used intraocular lenses

PURPOSE

The aim of this study is to compare the length of time from uneventful cataract surgery using one of two common posterior chamber intraocular lenses (IOLs) (hydrophilic versus hydrophobic acrylic) to laser capsulotomy.

MATERIALS AND METHODS

Retrospective analysis of all patients who underwent neodymium: yttrium-aluminum-garnet laser capsulotomy between 2011 and 2014 following uneventful phacoemulsification surgery at a tertiary university-affiliated medical center. Medical records were reviewed for demographics, ocular comorbidities, operative details, postoperative follow-up, and findings of the precapsulotomy ophthalmologic examination. Parameters, including age, sex, laterality, visual acuity, surgeon's experience, and time from cataract surgery to capsulotomy, were compared between patients who received hydrophilic (SeeLens AF, Kibbutz Hanita, Israel) or hydrophobic (AcrySof SA60AT, Alcon Laboratories, Fort Worth, TX, USA) IOLs.

RESULTS

The cohort included 222 patients (255 eyes), of which, 107 were male and 115 female, of mean age 73 ± 8 years. Mean interval from cataract surgery to laser capsulotomy was 24 months (range 2-70) and was significantly shorter in patients with SeeLens (23 ± 13 months) than AcrySof IOL implantation (28 ± 13 months, P = 0.04). Lens type remained significant in multivariate analysis after including surgeon's experience and age as potential confounders (P = 0.04).

CONCLUSION

The hydrophilic SeeLens IOL is associated with a significantly shorter time interval from cataract surgery to laser capsulotomy than the hydrophobic AcrySof IOL.

Sulforaphane promotes ER stress, autophagy, and cell death: implications for cataract surgery

Abstract

Posterior capsule opacification (PCO) commonly develops following cataract surgery and is a wound-healing response that can ultimately lead to secondary visual loss. Improved management of this problem is required. The isothiocyanate, sulforaphane (SFN), is reported to exert cytoprotective and cytotoxic actions, and the latter may be exploited to treat/prevent PCO. SFN concentrations of 10 μM and above significantly impaired wound-healing in a human lens capsular bag model. A similar pattern of response was also seen with a human lens cell line, FHL124. SFN treatment promoted increased expression of endoplasmic reticulum (ER) stress genes, which also corresponded with protein expression. Evidence of autophagy was observed in response to SFN as determined by increased microtubule-associated protein 1A/1B-light chain 3 (LC3)-II levels and detection of autophagic vesicles. This response was disrupted by established autophagy inhibitors chloroquine and 3-MA. SFN was found to promote MAPK signaling, and inhibition of ERK activation using U0126 prevented SFN-induced LC3-II elevation and vesicle formation. SFN also significantly increased levels of reactive oxygen species. Taken together, our findings suggest that SFN is capable of reducing lens cell growth and viability and thus could serve as a putative therapeutic agent for PCO.

Key message

SFN reduces lens epithelial cell growth, migration, and viability.

SFN can promote ER stress and autophagy in lens cells.

SFN promotes MAPK signaling, and inhibition of MEK can suppress SFN-induced autophagy.

ER stress and autophagy in lens cells are likely promoted by ROS production.

SFN may help prevent posterior capsule opacification after cataract surgery.

Growth factor restriction impedes progression of wound healing following cataract surgery: identification of VEGF as a putative therapeutic target

Secondary visual loss occurs in millions of patients due to a wound-healing response, known as posterior capsule opacification (PCO), following cataract surgery. An intraocular lens (IOL) is implanted into residual lens tissue, known as the capsular bag, following cataract removal. Standard IOLs allow the anterior and posterior capsules to become physically connected. This places pressure on the IOL and improves contact with the underlying posterior capsule. New open bag IOL designs separate the anterior capsule and posterior capsules and further reduce PCO incidence. It is hypothesised that this results from reduced cytokine availability due to greater irrigation of the bag. We therefore explored the role of growth factor restriction on PCO using human lens cell and tissue culture models. We demonstrate that cytokine dilution, by increasing medium volume, significantly reduced cell coverage in both closed and open capsular bag models. This coincided with reduced cell density and myofibroblast formation. A screen of 27 cytokines identified nine candidates whose expression profile correlated with growth. In particular, VEGF was found to regulate cell survival, growth and myofibroblast formation. VEGF provides a therapeutic target to further manage PCO development and will yield best results when used in conjunction with open bag IOL designs.

Elevated Transforming Growth Factor-β2 in the Aqueous Humor: A Possible Explanation for High Rate of Capsular Contraction Syndrome in High Myopia

Purpose. The purpose of the study was to elucidate the role of transforming growth factor-beta 2 (TGF-β2) in the development of high myopic capsular contraction syndrome. Methods. Nineteen cases of capsular contraction syndrome, including 14 with high myopia, were collected, and their clinical data were reviewed. Aqueous humor and anterior capsular membranes were obtained during capsulotomy. Hematoxylin-eosin and immunohistochemical staining with anti-TGF-β2 antibody were performed on capsular membranes. TGF-β2 levels in aqueous humor were assayed using ELISA and western blot. Results. High myopia was significantly associated with the incidence of capsular contraction syndrome (odds ratio: 14.74, P < 0.001, 95% CI: 5.29–41.05). Histopathological analysis revealed proliferation of fibroblast-like lens epithelial cells on the shrunken anterior capsule, labeled with TGF-β2 antibodies. ELISA and Western blot showed higher levels of TGF-β2 in aqueous humor of patients with capsular contraction syndrome and high myopia. Conclusions. High myopia is a risk factor for capsular contraction syndrome. Elevated TGF-β2 levels in high myopic cataract patients may play an important role in the pathogenesis of capsular contraction syndrome.

Improving the drug development process by reducing the impact of adverse events: the case of cataracts considered

Cataract was used as a model for the prevalence and economic impact of adverse events during the drug development process. Meta-analysis revealed a reported prevalence of cataract at 12.0% (1.0-43.3%), 3.8% (2.4-12.5%), 1.0% (0.0-8.1%), 1.7% (0.0-34.8%) and 3.8% (2.3-5.7%) of compounds in preclinical, Phase I, II, III and IV clinical trials, respectively. Utilising a human-based in vitro screening assay to predict cataractogenic potential in human could allow better selection of novel compounds at early-stage drug development. This could significantly reduce costs and ultimately increase the probability of a drug obtaining FDA approval for a clinical application.