TGFbeta induces morphological and molecular changes similar to human anterior subcapsular cataract

Let-7c-3p suppresses lens epithelial-mesenchymal transition by inhibiting cadherin-11 expression in fibrotic cataract

Fibrotic cataract, including anterior subcapsular cataract (ASC) and posterior capsule opacification, always lead to visual impairment. Epithelial-mesenchymal transition (EMT) is a well-known event that causes phenotypic alterations in lens epithelial cells (LECs) during lens fibrosis. Accumulating studies have demonstrated that microRNAs are important regulators of EMT and fibrosis. However, the evidence explaining how microRNAs modulate the behavior and alter the cellular phenotypes of the lens epithelium in fibrotic cataract is insufficient. In this study, we found that hsa-let-7c-3p is downregulated in LECs in human ASC in vivo as well as in TGFβ2-induced EMT in vitro, indicating that hsa-let-7c-3p may participate in modulating the profibrotic processes in the lens. We then demonstrated that overexpression of hsa-let-7c-3p markedly suppressed human LEC proliferation and migration and attenuated TGFβ2-induced EMT and injury-induced ASC in a mouse model. In addition, hsa-let-7c-3p mediated lens fibrosis by directly targeting the CDH11 gene, which encodes cadherin-11 protein, an important mediator in the EMT signaling pathway. It decreased cadherin-11 protein expression at the posttranscriptional level but not at the transcriptional level by binding to a specific site in the 3-untranslated region (3'-UTR) of CDH11 mRNA. Moreover, blockade of cadherin-11 expression with a specific short hairpin RNA reversed TGFβ2-induced EMT in LECs in vitro. Collectively, these data demonstrated that hsa-let-7c-3p plays a clear role in attenuating ASC development and may be a novel candidate therapeutic for halting fibrosis and maintaining vision.

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.

Distinct gene expression profiles underlie morphological and etiological differences in pediatric cataracts

Purpose

Pediatric cataract is a major cause of preventable childhood blindness worldwide. Although genetic mutations or infections have been described in patients, the mechanistic basis of human cataract development remains poorly understood. Therefore, gene expression of structural, developmental, profibrotic, and transcription factors in phenotypically and etiologically distinct forms of pediatric cataracts were evaluated.

Methods

This cross-sectional study included 89 pediatric cataract subjects subtyped into 1) prenatal infectious (cytomegalovirus, rubella, and combined cytomegalovirus with rubella infection), 2) prenatal non-infectious, 3) posterior capsular anomalies, 4) postnatal, 5) traumatic, and 6) secondary, and compared to clear, non-cataractous material of eyes with the subluxated lenses. Expression of lens structure-related genes (Aqp-0, HspA4/Hsp70, CrygC), transcription factors (Tdrd7, FoxE3, Maf, Pitx 3) and profibrotic genes (Tgfβ, Bmp7, αSmA, vimentin) in surgically extracted cataract lens material were studied and correlated clinically.

Results

In cataract material, the lens-related gene expression profiles were uniquely associated with phenotype/etiology of different cataracts. Postnatal cataracts showed a significantly altered FoxE3 expression. Low levels of Tdrd7 expression correlated with posterior subcapsular opacity, whereas CrygC correlated significantly with anterior capsular ruptures. The expression of Aqp0 and Maf was elevated in infectious cataracts, particularly in CMV infections, compared to other cataract subtypes. Tgfβ showed significantly low expression in various cataract subtypes, whereas vimentin had elevated gene expression in infectious and prenatal cataracts.

Conclusion

A significant association between lens gene expression patterns in phenotypically and etiologically distinct subtypes of pediatric cataracts suggests regulatory mechanisms in cataractogenesis. The data reveal that cataract formation and presentation is a consequence of altered expression of a complex network of genes.

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.

Capsulotomy opening diameter outcomes in aphakic eyes after primary congenital cataract removal and its association

Aim

To observe the change of capsulotomy opening diameter (COD) in aphakic eyes after primary congenital cataract removal and investigate its influencing factors.

Methods

Ocular parameters, including corneal diameter (CD), axial length (AL), anterior and posterior COD (ACOD, PCOD), and age at surgery were recorded at primary congenital cataract removal and secondary intraocular lens implantation. The concentrations of 15 kinds of cytokines in aqueous humor samples collected at the primary surgery were detected. The change (Δ) of COD between two surgeries were described, and its association was analyzed.

Results

Fifty eyes from 33 patients with congenital cataract who underwent primary and secondary surgery were enrolled. The changes in ACOD and PCOD were not statistically significant on the whole. ΔACOD was positively correlated with ΔCD and the concentrations of PDGF-AA, VEGF and TGF-β1. The concentration of FGF-2 and the interval between two surgeries showed negative correlations with ΔACOD and ΔPCOD.

Conclusion

COD in aphakic eyes kept changing after primary surgery. The positive correlation between ΔACOD and ΔCD manifested the enlargement of ACOD was influenced by lateral eye growth. Meanwhile, ΔACOD was also associated with cytokines, indicating postoperative inflammation promoted the ACOD constriction.

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.

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.

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.

REPS2 downregulation facilitates FGF-induced adhesion and migration in human lens epithelial cells through FAK/Cdc42 signaling and contributes to posterior capsule opacification

Posterior capsular opacification (PCO) can cause postoperative visual loss after cataract surgery. Residual human lens epithelial cell (HLEC) proliferation, migration, epithelial-mesenchymal transition (EMT) and synthesis of extracellular matrix (ECM) are the entitative reasons for PCO. Low expression of Ral-binding protein 1-associated Eps domain-containing 2 (REPS2) and high levels of basic fibroblast growth factor (b-FGF) were observed in the lens and postoperative aqueous humor of cataract patients. REPS2 was identified as a negative regulator in growth factor signaling; however, its function in HLECs is unknown. This was first investigated in the present study by evaluating REPS2 expression in anterior lens capsules from cataract patients, a mouse cataract model, and HLE-b3 cells. The biological function of REPS2 in HLE-B3 cells was assessed by REPS2 silencing and Cell Counting Kit 8, wound healing, Transwell migration, F-actin staining, G-protein pulldown and western blot assays. In the present study, REPS2 was significantly downregulated in human and mouse cataract capsules and H₂O₂-treated HLE-B3 cells. REPS2 knockdown increased fibronectin, type I collagen, and α-smooth muscle actin expression levels and stimulated HLECs proliferation and migration; these effects were enhanced by FGF treatment and accompanied with focal adhesion kinase (FAK) phosphorylation, cell division cycle 42 (Cdc42) activation, focal adhesion protein upregulation, and F-actin cytoskeleton reorganization. However, treatment with the FAK inhibitor PF573228 abolished these effects. Thus, REPS2 downregulation in cataract HLECs induces their proliferation and facilitates FGF-induced ECM synthesis, EMT, cell adhesion and migration by activating FAK/Cdc42 signaling, which may underlie PCO pathogenesis.

Status of higher TGF-β1 and TGF-β2 levels in the aqueous humour of patients with diabetes and cataracts

Background

Transforming growth factor (TGF) is a cytokine that acts on the proliferation, migration, differentiation, and apoptosis of cells and the accumulation of extracellular matrix components. Very few studies have precisely evaluated the concentration of TGF-β in the aqueous humour (AH) of diabetic and cataract (DMC) eyes due to the low expression of proteins in the AH or other reasons. The concentrations of TGF-β1, -β2, and -β3 in the AH of the DMC group were compared with those of the age-related cataract (ARC) group.

Methods

We collected AH and lens epithelium samples from 33 DMC patients and 36 ARC patients. Luminex liquid suspension chip detection was applied to detect the concentration of TGF-β1, -β2, and -β3 in the AH samples. The expression of TGFB1/2/3 in lens epithelium samples was determined by quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The concentrations of TGF-β1 and TGF-β2 in AH samples of DMC eyes were higher than those of ARC eyes. The differences in TGF-β1 and TGF-β2 between the two groups were statistically significant (P value = 0.001 for TGF-β1, P value = 0.023 for TGF-β2). The difference of the correlation between TGF-β1 and glycosylated haemoglobin was significant (P value = 0.011, and Pearson correlation coefficient = 0.306). The difference of the correlation between TGF-β2 and glycosylated haemoglobin was significant (P value = 0.026, and Pearson correlation coefficient = 0.269). The mRNA expression levels of TGFB1 and TGFB2 were upregulated in DMC epithelium samples compared with ARC epithelium samples. The differences in TGFB1 and TGFB2 between the two groups were statistically significant (P value for TGFB1 = 0.041, P value for TGFB2 = 0.021).

Conclusions

The concentrations of TGF-β1 and TGF-β2 in AH samples were significantly higher in DMC eyes than in ARC eyes. The higher the glycosylated haemoglobin was, the higher the concentrations of TGF-β1 and -β2 were. The mRNA expression of TGFB1 and TGFB2 was significantly upregulated in DMC epithelial samples compared with ARC epithelial samples, suggesting the proinflammatory status of the anterior chamber of DMC eyes.

Aged Nrf2-Null Mice Develop All Major Types of Age-Related Cataracts

Purpose

Age-related cataracts affect the majority of older adults and are a leading cause of blindness worldwide. Treatments that delay cataract onset or severity have the potential to delay cataract surgery, but require relevant animal models that recapitulate the major types of cataracts for their development. Unfortunately, few such models are available. Here, we report the lens phenotypes of aged mice lacking the critical antioxidant transcription factor Nfe2l2 (designated as Nrf2 −/−).

Methods

Three independent cohorts of Nrf2 −/− and wild-type C57BL/6J mice were evaluated for cataracts using combinations of slit lamp imaging, photography of freshly dissected lenses, and histology. Mice were fed high glycemic diets, low glycemic diets, regular chow ad libitum, or regular chow with 30% caloric restriction.

Results

Nrf2 −/− mice developed significant opacities between 11 and 15 months and developed advanced cortical, posterior subcapsular, anterior subcapsular, and nuclear cataracts. Cataracts occurred similarly in male mice fed high or low glycemic diets, and were also observed in 21-month male and female Nrf2 −/− mice fed ad libitum or 30% caloric restriction. Histological observation of 18-month cataractous lenses revealed significant disruption to fiber cell architecture and the retention of nuclei throughout the cortical region of the lens. However, fiber cell denucleation and initiation of lens differentiation was normal at birth, with the first abnormalities observed at 3 months.

Conclusions

Nrf2 −/− mice offer a tool to understand how defective antioxidant signaling causes multiple forms of cataract and may be useful for screening drugs to prevent or delay cataractogenesis in susceptible adults.

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.

Exosomal miR-29b found in aqueous humour mediates calcium signaling in diabetic patients with cataract

AIM

To investigate the role of exosomal miR-29b and Ca²⁺ in regulating the function of human lens epithelial cells (HLECs).

METHODS

Exosomes were isolated from human aqueous humour (AH) by ultracentrifugation, and visualized by nanoparticle tracking and transmission electron microscopy. Exosomal miRNA sequencing was performed to identify differentially expressed miRNAs between diabetes with cataracts (DMC) group and age-related cataracts (ARC) group. TargetScan was used to predict potential target of certain miRNA. The expression of CACNA1C mRNA was determined by quantitative real-time polymerase chain reaction and CACNA1C protein was determined by Western blotting. Concentration of Ca²⁺ in human AH and the culture supernatant of cells were detected by the calcium assay kit. Cell counting kit-8 was used to determine cell viability.

RESULTS

Exosomes were isolated from human AH, which had a typical cup-shaped phenotype and a particle size distribution in accordance with micro extracellular vesicles. Exosomal miRNA sequencing revealed that miR-29b was significantly downregulated in DMC group compared with ARC. Ca²⁺ concentration of human AH in DMC was higher than that in ARC. The culture supernatant of cells transfected with miR-29b inhibitors had a higher concentration of Ca²⁺ than that transfected with miR-29b mimics. miR-29b reduced the viability of HLECs by upregulating CACNA1C expression.

CONCLUSION

Exosomes isolated from human AH contains abundant miRNAs. A significantly expressed miRNA, miR-29b, can affect the concentration of Ca²⁺ and regulate HLEC processes by upregulating CACNA1C.

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.

Laser-Activated Corneal Adhesive: Retinal Safety in Rabbit Model

Purpose

The purpose of this study was to investigate whether laser irradiation, used to activate an adhesive for sealing penetrating corneal incisions, causes any ophthalmoscopically or histologically visible retinal changes.

Methods

Baseline fundus assessment was conducted prior to laser irradiation of eyes of pigmented Dutch Belted rabbits. Treatment group was 18 eyes with the corneal adhesive activated in situ by a near infrared laser (125 mW for 45 seconds). The positive control group was 18 eyes, each irradiated for 60 seconds at 375, 500, 625, and 750 mW at different retinal locations. Unexposed regions of the retina were used as negative internal control. Ophthalmoscopic assessment was conducted immediately after laser exposure and prior to euthanasia. Retinas were histologically assessed at 0, 3, 72, and 168 hours after treatment.

Results

No ophthalmoscopically or histologically visible retinal changes were observed in the treatment group immediately, nor up to 168 hours after laser irradiation. In the positive control group, the incidences of ophthalmoscopically visible retinal lesions increased with irradiation power: 5.6% at 375 mW, 16.7% at 500 mW, 44.4% at 625 mW, and 50% at 750 mW. Histologically, retinal damage was observed as coagulative necrosis to all layers of the neural retina, including the retinal pigment epithelium.

Conclusions

The laser irradiation process used in the corneal adhesive technology did not cause any ophthalmoscopically or histologically visible retinal changes in the in vivo pigmented rabbit model. Prolonged exposure with this laser and at higher power can cause coagulative necrosis to the retina.

Translational Relevance

The corneal adhesive can be applied in humans without causing laser retinal damage.

Retinitis pigmentosa-associated anterior subcapsular cataract: morphological features and visual performance

PURPOSE

To investigate the morphological features and surgical outcomes of retinitis pigmentosa (RP)-associated anterior subcapsular cataract (ASC).

METHODS

Consecutive RP-associated ASC cases were reviewed, and one hundred patients (171 eyes) were included. Anterior segment photographed images by slit-lamp microscope were reviewed. Best-corrected visual acuity (BCVA) was recorded. The cases were classified according to preoperative best BCVA, the area (central, midperipheral and peripheral) and the density (Grade 1, vacuolar/bubble-like; Grade 2, plaque-like/translucent; and Grade 3, fibrotic/opaque) of ASC; subgroup analysis of surgical outcomes was then performed.

RESULTS

The mean age was 52.1 ± 13.7 years, and the 41-50-year group had the best BCVA. 13.5% of eyes had BCVA better than 20/63, 30.4% were between 20/400 and 20/63, and 56.1% were worse than 20/400. The percentage of ASCs in the central, midperipheral and peripheral areas was 55.0%, 37.4% and 7.6%, respectively. Postoperative BCVA was improved in the central and midperipheral groups (P < 0.001) but was not in the peripheral group (P = 0.07). The percentage of ASCs in density of Grade 1, 2 and 3 was 11.1%, 38.6% and 50.3%, respectively. Grade 2 and 3 achieved improved postoperative BCVA (P < 0.001), but Grade 1 did not (P = 0.693).

CONCLUSIONS

Mostly, ASC is located at the center of the pupillary area and affected the residual vision of RP patients. The patients benefited from cataract removal except for those with ASC extended to peripheral area. Surgery was also recommended for RP with ASC developed to be plaque-like and even fibrotic.

Early Onset of Age-Related Cataracts in Cystine/Glutamate Antiporter Knockout Mice

Purpose

The purpose of this study was to determine the importance of the xCT is a subunit. The cystine/glutamate antiporter is actually system xc-xCT subunit of the cystine/glutamate antiporter in maintaining redox balance by investigating the effects of the loss of xCT on lens transparency and cystine/cysteine balance in the aqueous humour.

Methods

C57Bl/6 wild-type and xCT knockout mice at five age groups (6 weeks to 12 months) were used. Lens transparency was examined using a slit-lamp and morphological changes visualized by immunolabelling and confocal microscopy. Quantification of glutathione in lenses and cysteine and cystine levels in the aqueous was conducted by liquid chromatography tandem mass spectrometry (LC-MS/MS).

Results

Slit-lamp examinations revealed that 3-month-old wild-type mice and xCT knockout mice lenses exhibited an anterior localized cataract. The frequency of this cataract significantly increased in the knockout mice compared to the wild-type mice. Morphological studies revealed a localized swelling of the lens fiber cells at the anterior pole. Glutathione levels in whole lenses were similar between wild-type and knockout mice. However, glutathione levels were significantly decreased at 3 months in the knockout mice in the lens epithelium compared to the wild-type mice. Aqueous cysteine levels remained similar between wild-type and knockout mice at all age groups, whereas cystine levels were significantly increased in 3-, 9-, and 12-month-old knockout mice compared to wild-type mice.

Conclusions

Loss of xCT resulted in the depletion of glutathione in the epithelium and an oxidative shift in the cysteine/cystine ratio of the aqueous. Together, these oxidative changes may contribute to the accelerated development of an anterior cataract in knockout mice, which appears to be a normal feature of aging in wild-type mice.

Lens-specific conditional knockout of tropomyosin 1 gene in mice causes abnormal fiber differentiation and lens opacity

Tropomyosin (Tpm) 1 and 2 are important in the epithelial mesenchymal transition of lens epithelial cells; however, the effect of Tpm1 depletion during aging remains obscure. We analyzed the age-related changes in the crystalline lens of Tpm1- conditional knockout mice (Tpm1-CKO). Floxed alleles of Tpm1 were conditionally deleted in the lens, using Pax6-cre transgenic mice. Lenses of embryonic day (ED) 14, postnatal 1-, 11-, and 48-week-old Tpm1-CKO and wild type mice were dissected to prepare paraffin sections, which subsequently underwent histological and immunohistochemical analysis. Tpm1 and α smooth muscle actin (αSMA) mRNA expression were assessed using RT-PCR. The homozygous Tpm1-CKO (Tpm1^-/-) lenses displayed a dramatic reduction in Tpm1 transcript, with no change to αSMA mRNA expression. Tpm1^-/- mice had small lenses with disorganized, vesiculated fiber cells, and loss of epithelial cells. The lenses of Tpm1^-/- mice had abnormal and disordered lens fiber cells with cortical and peri-nuclear liquefaction. Expression of filamentous-actin was reduced in the equator region of lenses derived from ED14, 1-, 11-, and 48-week-old Tpm1^-/- mice. Therefore, Tpm1 plays an integral role in mediating the integrity and fate of lens fiber differentiation and lens homeostasis during aging. Age-related Tpm1 dysregulation or deficiency may induce cataract formation.

Role of Decorin in Posterior Capsule Opacification and Eye Lens Development

Decorin (DCN) is involved in a variety of physiological and pathological processes. Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) has been proposed as a major cause for the development of posterior capsule opacification (PCO) after cataract surgery. We investigated the plausible target gene(s) that suppress PCO. The expression of Dcn was significantly upregulated in rat PCO tissues compared to that observed in the control using a microarray-based approach. LECs treated with fibroblast growth factor (FGF) 2 displayed an enhanced level of DCN expression, while LECs treated with transforming growth factor (TGF)β-2 showed a decrease in DCN expression. The expression of tropomyosin 1 (Tpm1), a marker of lens EMT increased after the addition of TGFβ-2 in human LEC; however, upregulation of Tpm1 mRNA or protein expression was reduced in human LECs overexpressing human DCN (hDCN). No phenotypic changes were observed in the lenses of 8- and 48-week-old transgenic mice for lens-specific hDCN (hDCN-Tg). Injury-induced EMT of the mouse lens, and the expression patterns of α smooth muscle actin, were attenuated in hDCN-Tg mice lenses. Overexpression of DCN inhibited the TGFβ-2-induced upregulation of Tpm1 and EMT observed during wound healing of the lens, but it did not affect mouse lens morphology until 48 weeks of age. Our findings demonstrate that DCN plays a significant role in regulating EMT formation of LECs and PCO, and suggest that for therapeutic intervention, maintenance of physiological expression of DCN is essential to attenuate EMT progression and PCO formation.

On the Nature of Murine Radiation-Induced Subcapsular Cataracts: Optical Coherence Tomography-Based Fine Classification, In Vivo Dynamics and Impact on Visual Acuity

Ionizing radiation is widely known to induce various kinds of lens cataracts, of which posterior subcapsular cataracts (PSCs) have the highest prevalence. Despite some studies regarding the epidemiology and biology of radiation-induced PSCs, the mechanism underscoring the formation of this type of lesions and their dose dependency remain uncertain. Within the current study, our team investigated the in vivo characteristics of PSCs in B6C3F1 mice (F1-hybrids of BL6 × C3H) that received 0.5-2 Gy γ-ray irradiation after postnatal day 70. For purposes of assessing lenticular damages, spectral domain optical coherence tomography was utilized, and the visual acuity of the mice was measured to analyze their levels of visual impairment, and histological sections were then prepared in to characterize in vivo phenotypes. Three varying in vivo phenotype anterior and posterior lesions were thus revealed and correlated with the applied doses to understand their marginal influence on the visual acuity of the studied mice. Histological data indicated no significantly increased odds ratios for PSCs below a dose of 1 Gy at the end of the observation time. Furthermore, our team demonstrated that when the frequencies of the posterior and anterior lesions were calculated at early time points, their responses were in accordance with a deterministic model, whereas at later time points, their responses were better described via a stochastic model. The current study will aid in honing the current understanding of radiation-induced cataract formation and contributes greatly to addressing the fundamental questions of lens dose response within the field of radiation biology.

Long-term myofibroblast persistence in the capsular bag contributes to the late spontaneous in-the-bag intraocular lens dislocation

Late spontaneous in-the-bag intraocular lens (IOL) dislocation is a complication presenting 6 months or later after cataract surgery. We aimed to characterize the cells in the lens capsules (LCs) of 18 patients with spontaneous late in-the-bag IOL dislocation. Patients' average age was 82.6 ± 1.5 years (range 72-98), and most of them had pseudoexfoliation syndrome (PEX). Cells from the LCs were positive for myofibroblast (αSMA), proliferation (Ki-67, PCNA), early lens development/lens progenitor (SOX2, PAX6), chemokine receptor (CXCR4), and transmembrane (N-cadherin) markers, while negative for epithelial (E-cadherin) marker. Moreover, the cells produced abundant fibronectin, type I and type V collagen in the nearby extracellular matrix (ECM). During ex vivo cultivation of dislocated IOL-LCs in toto, the cells proliferated and likely migrated onto the IOL's anterior side. EdU proliferation assay confirmed the proliferation potential of the myofibroblasts (MFBs) in dislocated IOL-LCs. Primary cultured lens epithelial cells/MFBs isolated from the LC of dislocated IOLs could induce collagen matrix contraction and continuously proliferated, migrated, and induced ECM remodeling. Taken together, this indicates that long-lived MFBs of dislocated IOLs might contribute to the pathogenic mechanisms in late in-the-bag IOL dislocation.

Exosomal miRNA Analysis of Aqueous Humour of Diabetes and Cataract Patients

BACKGROUND

The mechanism of diabetes and cataracts is complicated. Considering our increasing acknowledge of exosomes, exosomal miRNAs isolated from aqueous humour (AH) may play an important role in the mechanism of diabetes and cataracts. Our study aimed to isolate exosomes from human aqueous humour and study the functions of exosomal miRNAs on human lens epithelial cells (HLECs).

RESULTS

MiRNA sequencing revealed that 295 miRNAs were upregulated and 138 miRNAs were downregulated in exosomes of the diabetes and cataracts group (DMC) compared with the age-related cataracts group (ARC), among which miR-551b was highly expressed with a log2 fold change of 5.99. GO and KEGG analyses indicated that the predicted genes were mainly involved in cadherin binding, proteoglycans in cancer and AGE-RAGE signalling pathway in diabetic complications. We then examined the function of miR-551b and found that miR-551b reduced the viability and increased the apoptosis of HLECs by downregulating CRYAA expression.

CONCLUSIONS

Exosomes isolated from human aqueous humour contained abundant miRNAs. A highly expressed miRNA, miR-551b, could regulate the functions of HLEC by targeting CRYAA.

METHODS

We pooled all the aqueous humour of each group into one sample and isolated exosomes from human aqueous humour by ultracentrifugation, measured the size and concentration of exosomes by nanoparticle tracking analysis (NTA), observed the morphology of exosomes by transmission electron microscopy (TEM), and sequenced exosomal miRNAs. We performed bioinformatic analysis of the sequencing results, including GO analysis and KEGG pathway enrichment. We then examined CRYAA mRNA expression levels and protein levels by quantitative real-time PCR and Western blot. Cell Counting Kit-8 and flow cytometry were applied to examine cell viability, proliferation and apoptosis.

Laminin α4 overexpression in the anterior lens capsule may contribute to the senescence of human lens epithelial cells in age-related cataract

Senescence is a leading cause of age-related cataract (ARC). The current study indicated that the senescence-associated protein, p53, total laminin (LM), LMα4, and transforming growth factor-beta1 (TGF-β1) in the cataractous anterior lens capsules (ALCs) increase with the grades of ARC. In cataractous ALCs, patient age, total LM, LMα4, TGF-β1, were all positively correlated with p53. In lens epithelial cell (HLE B-3) senescence models, matrix metalloproteinase-9 (MMP-9) alleviated senescence by decreasing the expression of total LM and LMα4; TGF-β1 induced senescence by increasing the expression of total LM and LMα4. Furthermore, MMP-9 silencing increased p-p38 and LMα4 expression; anti-LMα4 globular domain antibody alleviated senescence by decreasing the expression of p-p38 and LMα4; pharmacological inhibition of p38 MAPK signaling alleviated senescence by decreasing the expression of LMα4. Finally, in cataractous ALCs, positive correlations were found between LMα4 and total LM, as well as between LMα4 and TGF-β1. Taken together, our results implied that the elevated LMα4, which was possibly caused by the decreased MMP-9, increased TGF-β1 and activated p38 MAPK signaling during senescence, leading to the development of ARC. LMα4 and its regulatory factors show potential as targets for drug development for prevention and treatment of ARC.

MicroRNA miR-29c-3p modulates FOS expression to repress EMT and cell proliferation while induces apoptosis in TGF-β2-treated lens epithelial cells regulated by lncRNA KCNQ1OT1

Age-related cataract (ARC) is a main cause of blindness for elderly people. MicroRNA hsa_miR-29c-3p (miR-29c-3p) was implicated in many biological processes in complicated diseases. However, the biological mechanism of miR-29c-3p in ARC is still undefined. Quantitative real-time polymerase chain reaction (qRT-PCR) showed that miR-29c-3p was lowly expressed, while FBJ murine osteosarcoma viral oncogene homolog (FOS) and KCNQ1 overlapping transcript 1 (KCNQ1OT1) were highly expressed in cataract tissues and in TGF-β2-treated SRA01/04 cells. Western blot assay indicated that TGF-β2 could promote epithelial-mesenchymal transition (EMT). Moreover, our data suggested that miR-29c-3p overexpression suppressed EMT, cell proliferation and promoted apoptosis in TGF-β2-treated SRA01/04 cells. The dual-luciferase reporter assay verified that FOS was a target of miR-29c-3p and miR-29c-3p was directly targeted by KCNQ1OT1. Furthermore, KCNQ1OT1 could regulate FOS expression by sponging miR-29c-3p. Functional assays revealed that miR-29c-3p regulated FOS to repress EMT, cell proliferation and facilitate apoptosis in TGF-β2-treated SRA01/04 cells mediated by KCNQ1OT1. In conclusion, KCNQ1OT1/miR-29c-3p/FOS axis played a vital role in the progression of ARC.

Fibronectin has multifunctional roles in posterior capsular opacification (PCO)

Fibrotic posterior capsular opacification (PCO), one of the major complications of cataract surgery, occurs when lens epithelial cells (LCs) left behind post cataract surgery (PCS) undergo epithelial to mesenchymal transition, migrate into the optical axis and produce opaque scar tissue. LCs left behind PCS robustly produce fibronectin, although its roles in fibrotic PCO are not known. In order to determine the function of fibronectin in PCO pathogenesis, we created mice lacking the fibronectin gene (FN conditional knock out -FNcKO) from the lens. While animals from this line have normal lenses, upon lens fiber cell removal which models cataract surgery, FNcKO LCs exhibit a greatly attenuated fibrotic response from 3 days PCS onward as assessed by a reduction in surgery-induced cell proliferation, and fibrotic extracellular matrix (ECM) production and deposition. This is correlated with less upregulation of Transforming Growth Factor β (TGFβ) and integrin signaling in FNcKO LCs PCS concomitant with sustained Bone Morphogenetic Protein (BMP) signaling and elevation of the epithelial cell marker E cadherin. Although the initial fibrotic response of FNcKO LCs was qualitatively normal at 48 h PCS as measured by the upregulation of fibrotic marker protein αSMA, RNA sequencing revealed that the fibrotic response was already quantitatively attenuated at this time, as measured by the upregulation of mRNAs encoding molecules that control, and are controlled by, TGFβ signaling, including many known markers of fibrosis. Most notably, gremlin-1, a known regulator of TGFβ superfamily signaling, was upregulated sharply in WT LCs PCS, while this response was attenuated in FNcKO LCs. As exogenous administration of either active TGFβ1 or gremlin-1 to FNcKO lens capsular bags rescued the attenuated fibrotic response of fibronectin null LCs PCS including the loss of SMAD2/3 phosphorylation, this suggests that fibronectin plays multifunctional roles in fibrotic PCO development.

Histone acetyltransferase and Polo-like kinase 3 inhibitors prevent rat galactose-induced cataract

Diabetic cataracts can occur at an early age, causing visual impairment or blindness. The detailed molecular mechanisms of diabetic cataract formation remain incompletely understood, and there is no well-documented prophylactic agent. Galactose-fed rats and ex vivo treatment of lenses with galactose are used as models of diabetic cataract. To assess the role of histone acetyltransferases, we conducted cataract prevention screening with known histone acetyltransferase (HAT) inhibitors. Ex vivo treatment with a HAT inhibitor strongly inhibited the formation of lens turbidity in high-galactose conditions, while addition of a histone deacetylase (HDAC) inhibitor aggravated turbidity. We conducted a microarray to identify genes differentially regulated by HATs and HDACs, leading to discovery of a novel cataract causative factor, Plk3. Plk3 mRNA levels correlated with the degree of turbidity, and Plk3 inhibition alleviated galactose-induced cataract formation. These findings indicate that epigenetically controlled Plk3 influences cataract formation. Our results demonstrate a novel approach for prevention of diabetic cataract using HAT and Plk3 inhibitors.

Age-related changes in eye lens biomechanics, morphology, refractive index and transparency

Life-long eye lens function requires an appropriate gradient refractive index, biomechanical integrity and transparency. We conducted an extensive study of wild-type mouse lenses 1-30 months of age to define common age-related changes. Biomechanical testing and morphometrics revealed an increase in lens volume and stiffness with age. Lens capsule thickness and peripheral fiber cell widths increased between 2 to 4 months of age but not further, and thus, cannot account for significant age-dependent increases in lens stiffness after 4 months. In lenses from mice older than 12 months, we routinely observed cataracts due to changes in cell structure, with anterior cataracts due to incomplete suture closure and a cortical ring cataract corresponding to a zone of compaction in cortical lens fiber cells. Refractive index measurements showed a rapid growth in peak refractive index between 1 to 6 months of age, and the area of highest refractive index is correlated with increases in lens nucleus size with age. These data provide a comprehensive overview of age-related changes in murine lenses, including lens size, stiffness, nuclear fraction, refractive index, transparency, capsule thickness and cell structure. Our results suggest similarities between murine and primate lenses and provide a baseline for future lens aging studies.

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.

High glucose: activating autophagy and affecting the biological behavior of human lens epithelial cells

AIM

To clarify the effect of autophagy on human lens epithelial cells (HLECs) under high glucose conditions.

METHODS

HLECs were cultured with different concentrations of glucose and 3-methyladenine (3-MA); the expression of autophagy-related protein LC3B was detected by Western blotting and immunofluorescence histochemistry. The migration of HLECs was quantified by scratch wound assay and the expression of transforming growth factor-β (TGF-β) was measured by real-time polymerase chain reaction.

RESULTS

Compared with 5 mmol/L normal glucose treatment, 40 mmol/L glucose treatment can significantly increase the generation of autophagosome in HLECs, which could be inhibited by 0.375 mmol/L 3-MA treatment. The migration of HLECs and the expression of TGF-β in HLECs induced by high glucose were significantly suppressed by 0.375 mmol/L 3-MA treatment.

CONCLUSION

Autophagy promotes HLECs cell migration and increases the expression of TGF-β after exposed to high glucose, which may relate to the development of diabetic cataract.

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.

β-Catenin/Smad3 Interaction Regulates Transforming Growth Factor-β-Induced Epithelial to Mesenchymal Transition in the Lens

Cataracts are the leading cause of blindness worldwide. Although surgery is a successful method to restore vision loss due to cataracts, post-surgical complications can occur, such as secondary cataracts, also known as posterior capsular opacification (PCO). PCO arises when lens epithelial cells (LEC) are left behind in the capsular bag following surgery and are induced to undergo epithelial to mesenchymal transition (EMT). Following EMT, LEC morphology and phenotype are altered leading to a loss of transparency and vision. Transforming growth factor (TGF)-β-induced signaling through both canonical, TGF-β/Smad, and non-canonical, β-catenin/Wnt and Rho/ROCK/MRTF-A, pathways have been shown to be involved in lens EMT, and thus PCO. However, the interactions between these signaling pathways in the lens have not been thoroughly explored. In the current study we use rat LEC explants as an ex vivo model, to examine the interplay between three TGF-β-mediated pathways using α-smooth muscle actin (α-SMA) as a molecular marker for EMT. We show that Smad3 inhibition via SIS3 prevents nuclear translocation of β-catenin and MRTF-A, and α-SMA expression, suggesting a key role of Smad3 in regulation of MRTF-A and β-catenin nuclear transport in LECs. Further, we demonstrate that inhibition of β-catenin/CBP interaction by ICG-001 decreased the amount of phosphorylated Smad3 upon TGF-β stimulation in addition to significantly decreasing the expression levels of TGF-β receptors, TBRII and TBRI. Overall, our findings demonstrate interdependence between the canonical and non-canonical TGF-β-mediated signaling pathways controlling EMT in the lens.

The Role of Peroxiredoxin 6 in Cell Signaling

Peroxiredoxin 6 (Prdx6, 1-cys peroxiredoxin) is a unique member of the peroxiredoxin family that, in contrast to other mammalian peroxiredoxins, lacks a resolving cysteine and uses glutathione and π glutathione S-transferase to complete its catalytic cycle. Prdx6 is also the only peroxiredoxin capable of reducing phospholipid hydroperoxides through its glutathione peroxidase (Gpx) activity. In addition to its peroxidase activity, Prdx6 expresses acidic calcium-independent phospholipase A₂ (aiPLA₂) and lysophosphatidylcholine acyl transferase (LPCAT) activities in separate catalytic sites. Prdx6 plays crucial roles in lung phospholipid metabolism, lipid peroxidation repair, and inflammatory signaling. Here, we review how the distinct activities of Prdx6 are regulated during physiological and pathological conditions, in addition to the role of Prdx6 in cellular signaling and disease.

Roles of TGF β and FGF Signals in the Lens: Tropomyosin Regulation for Posterior Capsule Opacity

Transforming growth factor (TGF) β and fibroblast growth factor (FGF) 2 are related to the development of posterior capsule opacification (PCO) after lens extraction surgery and other processes of epithelial–mesenchymal transition (EMT). Oxidative stress seems to activate TGF β1 largely through reactive oxygen species (ROS) production, which in turn alters the transcription of several survival genes, including lens epithelium-cell derived growth factor (LEDGF). Higher ROS levels attenuate LEDGF function, leading to down-regulation of peroxiredoxin 6 (Prdx6). TGF β is regulated by ROS in Prdx6 knock-out lens epithelial cells (LECs) and induces the up-regulation of tropomyosins (Tpms) 1/2, and EMT of LECs. Mouse and rat PCO are accompanied by elevated expression of Tpm2. Further, the expression of Tpm1/2 is induced by TGF β2 in LECs. Importantly, we previously showed that TGF β2 and FGF2 play regulatory roles in LECs in a contrasting manner. An injury-induced EMT of a mouse lens as a PCO model was attenuated in the absence of Tpm2. In this review, we present findings regarding the roles of TGF β and FGF2 in the differential regulation of EMT in the lens. Tpms may be associated with TGF β2- and FGF2-related EMT and PCO development.

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.

Functional role of peroxiredoxin 6 in the eye

Peroxiredoxin 6 (Prdx6) is the only mammalian 1-Cys member of the Prdx family, a group of enzymes which share the ability to reduce peroxides. In addition to its peroxidase function, Prdx6 also demonstrates phospholipase A₂ and lysophosphatidylcholine acyl transferase (LPCAT) activities. These enzymatic activities play an important role in regenerating oxidized membrane phospholipids and maintaining an appropriate balance of intracellular reactive oxygen species. Development of clinical pathologies, including those within the eye, have been linked to dysregulation of Prdx6 function. Interplay between external stressors like exposure to UV light, transforming growth factor β (TGF-β), and hyperglycemia in conjunction with diminished Prdx6 levels and loss of redox balance is associated with cellular changes in a variety of ophthalmic pathologies including cataracts, glaucoma, and retinal degeneration. Many of these cellular abnormalities can be rescued through supplementation with exogenous Prdx6. Additionally, corneal endothelial cells have been found to express high levels of Prdx6 in the plasma membrane. These findings highlight the importance of Prdx6 as an essential regulator of oxidative stress in the eye.

Long noncoding RNA KCNQ1OT1 promotes proliferation and epithelial‑mesenchymal transition by regulation of SMAD4 expression in lens epithelial cells

Long noncoding RNAs (lncRNAs) are associated with various diseases including cataracts. The role of lncRNA potassium voltage-gated channel subfamily Q member 1 opposite strand/antisense transcript 1 (KCNQ1OT1) on lens epithelial cell (LEC) proliferation and epithelial-mesenchymal transition (EMT) in cataracts disease remains unclear. In the present study, KCNQ1OT1 and mothers against decapentaplegic homolog (SMAD)4 expression levels were upregulated in human cataract lens posterior capsular samples and in transforming growth factor (TGF)-β2-treated SRA01/04 cells, as demonstrated by reverse transcription-quantitative polymerase chain reaction, immunohistochemical staining and western blot analyses. A further loss of function test revealed that suppression of KCNQ1OT1 inhibited the proliferation and EMT of TGF-β2-treated SRA01/04 cells. Additionally, the present study reported that increase and decrease of KCNQ1OT1 regulated SMAD4 expression, which indicated that SMAD4 may be a downstream gene of KCNQ1OT1. Finally, a constructed SMAD4 RNA interference experiment confirmed that the function of KCNQ1OT1 was to act on LEC proliferation and EMT, and this was achieved via the SMAD4 signaling pathway. The findings of the present study may provide a novel target for molecular therapy of cataracts disease.

CTGF Contributes to the Development of Posterior Capsule Opacification: an in vitro and in vivo study

Connective tissue growth factor (CTGF) is a crucial factor that plays a major role in the process of posterior capsule opacification (PCO). However, the effects of CTGF on the proliferation and migration of lens epithelial cells (LECs) and on the mechanism of the epithelial mesenchymal transition (EMT) and extracellular matrix (ECM) in human lens epithelial cells (HLECs) as well as the effects of shRNA-mediated CTGF knockdown on the development of PCO in rats remain unclear. In the present study, we found that CTGF promoted EMT, proliferation, migration and the expression of p-ERK1/2 protein in HLECs but exerted little effect on the expression of p-p38 and p-JNK1/2 proteins. MEK inhibitor U0126 effectively restrained the CTGF-induced expression of α-smooth muscle actin (α-SMA), fibronectin (Fn) and type I collagen (COL-1) in HLECs. CTGF knockdown effectively postponed the onset of PCO in the rats and significantly reduced the expression of α-SMA in the capsule. In conclusion, CTGF contributed to the development of PCO presumably by promoting proliferation, migration of LECs, EMT specific protein expression and ECM synthesis in HLECs, which is dependent on ERK signalling. Furthermore, blocking CTGF effectively inhibited PCO in the rats and the EMT specific protein expression in the lens capsule.

Trichostatin A Restores Expression of Adherens and Tight Junction Proteins during Transforming Growth Factor β-Mediated Epithelial-to-Mesenchymal Transition

Purpose:

Adherens junctions and polarity markers play an important role in maintaining epithelial phenotype but get altered during the epithelial-mesenchymal transition (EMT). Alterations of these markers during EMT of lens epithelial cell (LEC) can lead to vision compromising conditions. The aim of this study was to examine if Trichostatin-A (TSA), a histone deacetylase inhibitor, can prevent EMT by restoring the adherens junction complex in LEC.

Methods:

Fetal human lens epithelial cell line (FHL124) was used. Cells were treated with 10 ng/ml TGF-β2 in the presence or absence of TSA. Real time-PCR and western blotting were carried out for HDAC1, HDAC2, CDH1 (E-cad), TJP1 (ZO-1) and CTNNB1 (β-cat). Level of histone acetylation was analyzed by western blotting. Chromatin Immunoprecipitation was carried out to study the level of acetylated histone H4 and HDAC2 at the promoter regions of CDH1, TJP1, and CTNNB1. E-cad, ZO-1, and β-cat were localized using immunofluorescence. Kruskal-Wallis test was used for statistical analysis.

Results:

TSA down-regulated HDAC1 and HDAC2 and led to an increase in global acetylation. The mRNA and protein levels of E-cad, ZO-1, and β-cat decreased during EMT but were up-regulated by TSA treatment. TSA also helped in stabilizing these proteins at cell-cell junctions during EMT. TSA decreases association of HDAC2 at the promoter regions of adherens junction genes while increasing histone H4 acetylation status.

Conclusion:

TSA increases histone acetylation and restores the adherens junction complex in LECs. TSA helps in preventing EMT and thus shows potential against lens fibrosis and vision compromising conditions.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Morgagnian cataract resulting from a naturally occurring nonsense mutation elucidates a role of CPAMD8 in mammalian lens development

To investigate the genetic basis of hereditary lens opacities we analyzed 31 cases of bilateral congenital cataract in Red Holstein Friesian cattle. A genome-wide association study revealed a significant association on bovine chromosome 7 at positions 6,166,179 and 12,429,691. Whole genome re-sequencing of one case and four relatives showed a nonsense mutation (g.5995966C>T) in the PZP-like, alpha-2-macroglobulin domain containing 8 (CPAMD8) gene leading to a premature stop codon (CPAMD8 p.Gln74*) associated with cataract development in cattle. With immunohistochemistry we confirmed a physiological expression of CPAMD8 in the ciliary body epithelium of the eye in unaffected cattle, while the protein was not detectable in the ciliary body of cattle with cataracts. RNA expression of CPAMD8 was detected in healthy adult, fetal and cataractous lenses.

Bone Morphogenetic Protein-7 Suppresses TGFβ2-Induced Epithelial-Mesenchymal Transition in the Lens: Implications for Cataract Prevention

Purpose

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a key pathologic mechanism underlying cataract. Two members of the transforming growth factor-β (TGFβ) superfamily, TGFβ and bone morphogenetic protein-7 (BMP-7) have functionally distinct roles in EMT. While TGFβ is a potent inducer of EMT, BMP-7 counteracts the fibrogenic activity of TGFβ. We examine the modulating effect of BMP-7 on TGFβ-induced EMT in LECs.

Methods

Rat lens epithelial explants were treated exogenously with TGFβ2 alone or in combination with BMP-7 for up to 5 days. Expression levels of E-cadherin, β-catenin, α-smooth muscle actin (α-SMA), and phosphorylated downstream Smads were determined using immunofluorescence and Western blotting. Reverse transcriptase quantitative PCR (RT-qPCR) was used to study gene expression levels of EMT markers and downstream BMP target genes, including the Inhibitors of differentiation (Id).

Results

Transforming growth factor-β2 induced LECs to transdifferentiate into myofibroblastic cells. Addition of BMP-7 suppressed TGFβ2-induced α-SMA protein levels and mesenchymal gene expression, with retention of E-cadherin and β-catenin expression to the cell membrane. Addition of BMP-7 prevented lens capsular wrinkling and cellular loss associated with TGFβ2-induced EMT over the 5-day treatment period. The inhibitory effect of BMP-7 was accompanied by an early induction of pSmad1/5 and suppression of TGFβ2-induced pSmad2/3. Treatment with TGFβ2 alone suppressed gene expression of Id2/3 and addition of BMP-7 restored Id2/3 expression.

Conclusions

Exogenous administration of BMP-7 abrogated TGFβ2-induced EMT in rat lens epithelial explants. Understanding the complex interplay between the TGFβ- and BMP-7–associated Smad signaling pathways and their downstream target genes holds therapeutic promise in cataract prevention.

The murine lens: A model to investigate in vivo epithelial-mesenchymal transition

Epithelial–mesenchymal transition (EMT) produces myofibroblasts that contribute to the formation of fibrotic tissue with an impairment of tissue homeostasis and functionality. The crystalline lens of the eye is a unique transparent and isolated tissue. The lens vesicle becomes isolated from the surface ectoderm, its cells are all contained as they line the inner surface of the lens capsule. Clinically the formation of fibrotic tissue by the lens epithelial cells causes a type of cataract or opacification and contraction of the lens capsule postcataract surgery. Production of EMT in the intact animal lens by using specific gene transfer to the lens or experimental lens injury has been shown to be a powerful tool to investigate EMT processes. It is not easy to uncover whether the origin of the myofibroblast is epithelial cell‐derived or from other cell lineages in fibrotic tissues. However, myofibroblasts that appear in the crystalline lens pathology are totally derived from the lens epithelial cells for the reasons mentioned above. Here, we report on different animal models of lens EMT, using either transgenic approaches or injury to study the biological aspects of EMT. Developmental Dynamics 247:340–345, 2018. © 2017 The Authors Developmental Dynamics published by Wiley Periodicals, Inc. on behalf of American Association of Anatomists

Lens, Epithelial‐mesenchymal transition, mice.

ERK1/2 signaling is required for the initiation but not progression of TGFβ-induced lens epithelial to mesenchymal transition (EMT)

Transforming Growth Factor Beta (TGFβ) potently induces lens epithelial to mesenchymal transition (EMT). The resultant mesenchymal cells resemble those found in plaques of human forms of subcapsular cataract. Smad signaling has long been implicated as the sole driving force of TGFβ-mediated activity. Rat lens epithelial explants were used to examine the role of the Smad-independent signaling, namely the MAPK/ERK1/2 signaling pathway, in the initiation and progression of TGFβ-induced EMT. Phase contrast microscopy was used to observe the morphological changes associated with TGFβ-induced EMT in this model, including cell elongation, cell membrane blebbing, cell loss as indicated by the area of bare capsule and capsular wrinkling. The levels of Smad2, Smad2/3 and ERK1/2 phosphorylation measured using western blotting confirmed that the addition of UO126 was sufficient in blocking all TGFβ-induced ERK1/2 activation, as well as reducing Smad signaling at 18 h. Immunofluorescent labeling and further western blotting confirmed that TGFβ-induced EMT was associated with an increase in α-smooth muscle actin (α-SMA) and a reduction of E-cadherin at cell borders. Pre-treatment with UO126 was effective at blocking the TGFβ-induced EMT, as evidenced by a reduction of α-SMA expression and protein labeling, E-cadherin labeling at cell borders, and a reduction of cell loss, cell elongation and capsular wrinkling. Post-treatment with UO126 at 2 and 6 h after TGFβ addition was also effective at blocking EMT while post-treatment with UO126 at 24 and 48 h was not sufficient in hampering TGFβ-induced EMT. Our data implicates ERK1/2 signaling in the initiation but not the progression of TGFβ-induced EMT in rat lens epithelial cells. The tight regulation of intracellular signaling pathways such as ERK1/2 are required for the maintenance of lens epithelial cell integrity and hence tissue transparency. A greater understanding of the molecular mechanisms that drive the induction and progression of EMT in the lens will provide the basis for potential therapeutics for human cataract.

TGF-β1 serum concentrations and receptor expressions in the lens capsular of dogs with diabetes mellitus

Tissue fibrosis as complication of diabetes mellitus is known in humans. Because TGF-β1induces fibrosis and is elevated in humans suffering from diabetes mellitus we measured this growth factor in serum of dogs with diabetes mellitus and compared it with healthy dogs and those with fibrotic diseases. Further we measured the expression of TGF-β1receptor on lens capsule to investigate possible association between diabetes mellitus and cataract associated alterations. TGF-β1 was measured in serum of 12 dogs with diabetes mellitus, 20 healthy controls and 12 dogs with fibrotic diseases. Dogs with diabetes mellitus and fibrotic diseases have significantly increased TGF-β1 serum concentrations compared to healthy controls. Some dogs with diabetes mellitus showed increased expression of TGF-β1 receptor in lens capsule. Based on our observations we can conclude that TGF-β1 elevation in dogs with diabetes mellitus may induces complications of the disease and may participates on lens alteration.

FGF2 antagonizes aberrant TGFβ regulation of tropomyosin: role for posterior capsule opacity

Transforming growth factor (TGF) β2 and fibroblast growth factor (FGF) 2 are involved in regulation of posterior capsule opacification (PCO) and other processes of epithelial–mesenchymal transition (EMT) such as cancer progression, wound healing and tissue fibrosis as well as normal embryonic development. We previously used an in vivo rodent PCO model to show the expression of tropomyosin (Tpm) 1/2 was aberrantly up‐regulated in remodelling the actin cytoskeleton during EMT. In this in vitro study, we show the Tpms family of cytoskeleton proteins are involved in regulating and stabilizing actin microfilaments (F‐actin) and are induced by TGFβ2 during EMT in lens epithelial cells (LECs). Importantly, we found TGFβ2 and FGF2 played contrasting roles. Stress fibre formation and up‐regulation of α‐smooth muscle actin (αSMA) induced by TGFβ2 could be reversed by Tpm1/2 knock‐down by siRNA. Expression of Tpm1/2 and stress fibre formation induced by TGFβ2 could be reversed by FGF2. Furthermore, FGF2 delivery to TGFβ‐treated LECs perturbed EMT by reactivating the mitogen‐activated protein kinase (MAPK)/ extracellular signal‐regulated kinase (ERK) pathway and subsequently enhanced EMT. Conversely, MEK inhibitor (PD98059) abated the FGF2‐mediated Tpm1/2 and αSMA suppression. However, we found that normal LECs which underwent EMT showed enhanced migration in response to combined TGFβ and FGF2 stimulation. These findings may help clarify the mechanism reprogramming the actin cytoskeleton during morphogenetic EMT cell proliferation and fibre regeneration in PCO. We propose that understanding the physiological link between levels of FGF2, Tpm1/2 expression and TGFβs‐driven EMT orchestration may provide clue(s) to develop therapeutic strategies to treat PCO based on Tpm1/2.

RhoA/ROCK signaling regulates TGFβ-induced epithelial-mesenchymal transition of lens epithelial cells through MRTF-A

Transforming growth factor (TGF)-β-induced epithelial-mesenchymal transition (EMT) leads to the formation of ocular fibrotic pathologies, such as anterior subcapsular cataract and posterior capsule opacification. Remodeling of the actin cytoskeleton, mediated by the Rho family of GTPases, plays a key role in EMT, however, how actin dynamics affect downstream markers of EMT has not been fully determined. Our previous work suggests that myocardin related transcription factor A (MRTF-A), an actin-binding protein, might be an important mediator of TGFβ-induced EMT in lens epithelial cells. The aim of the current study was to determine the requirement of RhoA/ROCK signaling in mediating TGFβ-induced nuclear accumulation of MRTF-A, and ultimate expression of α-smooth muscle actin (αSMA), a marker of a contractile, myofibroblast phenotype. Using rat lens epithelial explants, we demonstrate that ROCK inhibition using Y-27632 prevents TGFβ-induced nuclear accumulation of MRTF-A, E-cadherin/β-catenin complex disassembly, and αSMA expression. Using a novel inhibitor specifically targeting MRTF-A signaling, CCG-203971, we further demonstrate the requirement of MRTF-A nuclear localization and activity in the induction of αSMA expression. Overall, our findings suggest that TGFβ-induced cytoskeletal reorganization through RhoA/ROCK/MRTF-A signaling is critical to EMT of lens epithelial cells.