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

Oxidative Stress, Glutaredoxins, and Their Therapeutic Potential in Posterior Capsular Opacification

Posterior capsular opacification (PCO) is the most common long-term complication of cataract surgery. Traditionally, the pathogenesis of PCO involves the residual lens epithelial cells (LECs), which undergo transdifferentiation into a myofibroblast phenotype, hyperproliferation, matrix contraction, and matrix deposition. This process is driven by the marked upregulation of inflammatory and growth factors post-surgery. Recently, research on the role of redox environments has gained considerable attention. LECs, which are in direct contact with the aqueous humour after cataract surgery, are subjected to oxidative stress due to decreased levels of reduced glutathione and increased oxygen content compared to contact with the outer fibre layer of the lens before surgery. In this review, we examine the critical role of oxidative stress in PCO formation. We also focus on glutaredoxins (Grxs), which are antioxidative enzymes produced via deglutathionylation, their protective role against PCO formation, and their therapeutic potential. Furthermore, we discuss the latest advancements in PCO therapy, particularly the development of advanced antioxidative pharmacological agents, and emphasise the importance and approaches of anti-inflammatory and antioxidant treatments in PCO management. In conclusion, this review highlights the significant roles of oxidative stress in PCO, the protective effects of Grxs against PCO formation, and the potential of anti-inflammatory and antioxidant therapies in treating PCO.

[Conbercept reverses TGF-β2-induced epithelial-mesenchymal transition in human lens epithelial cells by regulating the TGF-β/Smad signaling pathway]

OBJECTIVE

To investigate the mechanism by which conbercept reverses transforming growth factor-β2 (TGF-β2)-induced epithelial-mesenchymal transition (EMT) in human lens epithelial cells (HLECs).

METHODS

Cultured HLEC SRA01/04 cells were treated with TGF-β2, conbercept, or both, and the changes in cell proliferation, apoptosis, and migration were observed using MTT assay, flow cytometry, scratch assay, and Transwell assay. Western blotting and qRT-PCR were used to detect the changes in the expression of EMT-related epithelial cell markers (E-Cadherin, α-SMA, and Snail), extracellular matrix components, and genes related to the TGF-β/Smad signaling pathway.

RESULTS

Conbercept significantly reduced TGF-β2-induced EMT of SRA01/04 cells, decreased the expression levels of mesenchymal and extracellular matrix markers α-SMA, Snail, collagen I, collagen IV, and FN1, and upregulated the protein and mRNA expressions of E-cadherin (P <0.05). Transwell assay showed significantly lower cell migration ability in TGF-β2+conbercept group than in TGF-β2 group (P <0.05). Conbercept also inhibited the increase in Smad2/3 phosphorylation levels in HLEC-SRA01/04 cells with TGF-β2-induced EMT (P <0.01).

CONCLUSION

Conbercept inhibits TGF-β2 induced EMT by downregulating the expression of pSmad2/3 in TGF-β/Smad signaling pathway, indicating a potential therapeutic strategy against visual loss induced by posterior capsule opacification.

Egg White Peptides Accelerating the Wound Healing Process Through Modulating the PI3K-AKT Pathway: A Joint Analysis of Transcriptomic and Proteomic

Wound healing is a multiphase process with a complex repair mechanism; trauma-repairing products with safety and high efficiency have a great market demand. Egg white peptides (EWP) have various physiological regulatory functions and have been proven efficient in ameliorating skin damage. However, their underlying regulation mechanism has not been revealed. This study further evaluated the EWP ameliorating mechanism by conducting a full-thickness skin wound model. Results demonstrated that EWP administration significantly inhibited the expression of pro-inflammatory and shortened the inflammatory phase. Besides, EWP can accelerate the secretion of growth factors (PDGF, VEGF, and TGF-β1) in skin tissue, significantly increasing the regeneration of granulation tissue and endothelium in the proliferation phase, thereby promoting wound healing. After 400 mg/kg EWP interventions for 13 days postoperation, the wound healing rate reached 90%. The combination of transcriptomic and proteomic analyses demonstrated the ameliorating efficiency effects of EWP on wound healing. EWP mainly participates in the functional network with the PI3K-AKT signaling pathway as the core to accelerate wound healing. These findings suggest a promising EWP-based strategy for accelerating wound healing.

Inhibition of anterior capsule opacification and contraction by the elevated anterior rim of the intraocular lens optic

PURPOSE

To verify the anterior capsule opacification (ACO) and contraction (ACC) of the ZCB00V intraocular lens (IOL), made of the same material as the AR40e with a high ACC rate.

STUDY DESIGN

Retrospective cohort study.

METHODS

We evaluated 35 patients at 1 week, 1, 3 and 6 months post phacoemulsification with either a ZCB00V (n = 35) or FY-60AD (n = 34) IOL implantation. The ACC rate was calculated using retroillumination images of the anterior segment, and the ACO was measured using anterior segment photographs and image analysis software. The contact grade between the IOL and anterior capsule was estimated from the Pentacam® images.

RESULTS

The postoperative ACC rates (mean ± standard deviation) at 3 months were 1.03%±2.54% for the ZCB00V and, and 7.12%±9.47% for the FY-60AD. The ZCB00V-implanted eyes showed a significantly lower postoperative ACC at 1 week, 3 months, and 6 months (P < 0.01). On the other hand, the FY-60AD-implanted eyes had more pronounced ACO, and a significantly larger area of opacification (62.24%±21.32% vs. 16.90%±8.34%; P = 0.0005). Pentacam® analysis revealed a space between the anterior capsule and IOL surface in the ZCB00V-implanted eyes, whereas the anterior capsule firmly adhered to the IOL surface in the FY-60AD-implanted eyes.

CONCLUSION

The ACC and ACO were significantly lower in eyes with ZCB00V IOLs compared to those with the FY-60AD. The anterior segment image analysis revealed that the elevated anterior rim of the ZCB00V IOL prevented adhesion between the anterior capsule and IOL optic surface, suggesting an open capsule effect.

The lens epithelium as a major determinant in the development, maintenance, and regeneration of the crystalline lens

The crystalline lens is a transparent and refractive biconvex structure formed by lens epithelial cells (LECs) and lens fibers. Lens opacity, also known as cataracts, is the leading cause of blindness in the world. LECs are the principal cells of lens throughout human life, exhibiting different physiological properties and functions. During the embryonic stage, LECs proliferate and differentiate into lens fibers, which form the crystalline lens. Genetics and environment are vital factors that influence normal lens development. During maturation, LECs help maintain lens homeostasis through material transport, synthesis and metabolism as well as mitosis and proliferation. If disturbed, this will result in loss of lens transparency. After cataract surgery, the repair potential of LECs is activated and the structure and transparency of the regenerative tissue depends on postoperative microenvironment. This review summarizes recent research advances on the role of LECs in lens development, homeostasis, and regeneration, with a particular focus on the role of cholesterol synthesis (eg., lanosterol synthase) in lens development and homeostasis maintenance, and how the regenerative potential of LECs can be harnessed to develop surgical strategies and improve the outcomes of cataract surgery (Fig. 1). These new insights suggest that LECs are a major determinant of the physiological and pathological state of the lens. Further studies on their molecular biology will offer possibility to explore new approaches for cataract prevention and treatment.

Twelve-Month Clinical Outcomes After Implantation of a Novel, Modular, Anterior Shape-Changing Fluid Optic Intraocular Lens

PURPOSE

To report the initial safety and effectiveness profile for an anterior shape-changing, modular IOL, Juvene (JIOL), for the treatment of aphakia and presbyopia after removal of the natural crystalline lens due to cataract.

SETTING

Two private practices in Monterrey and Tijuana, Mexico.

DESIGN

Exploratory, prospective, multi-center, open-label, non-comparative clinical trial.

METHODS

A convenience sample of subjects aged 50-80 years with planned cataract surgery were recruited to undergo unilateral or bilateral implantation with the JIOL. Subjects were required to complete an informed consent and be able to dilate to at least 6.0 mm pharmacologically, be in good overall health, and have no significant eye health history to qualify. Visual acuities, defocus curves, and contrast sensitivity were measured for all subjects 12 months postoperatively.

RESULTS

Fifty-one of 58 eyes completed the 12-month visit. Intraoperative complication rates were extremely low (N=1; missed base lens tab). The most frequent adverse events (AE) were prolonged inflammation (N=6) and cystoid macular edema (N=4); all AEs were resolved without sequelae by the 12-month visit. Mean monocular logMAR corrected distance visual acuity (CDVA), distance-corrected intermediate (DCIVA) and near (DCNVA) were 0.01, 0.08, and 0.24, respectively. Defocus testing showed VA > 20/40 from approximately +1.00 D through -2.00 D. Binocular implantation (n=16) provided superior performance over monocular implantation.

CONCLUSIONS

The Juvene IOL offers a novel solution to treat presbyopia, providing clear functional vision performance across a range of distances with an acceptable initial safety profile.

Posterior capsule opacification: What's in the bag?

Cataract, a clouding of the lens, is the most common cause of blindness in the world. It has a marked impact on the wellbeing and productivity of individuals and has a major economic impact on healthcare providers. The only means of treating cataract is by surgical intervention. A modern cataract operation generates a capsular bag, which comprises a proportion of the anterior capsule and the entire posterior capsule. The bag remains in situ, partitions the aqueous and vitreous humours, and in the majority of cases, houses an intraocular lens (IOL). The production of a capsular bag following surgery permits a free passage of light along the visual axis through the transparent intraocular lens and thin acellular posterior capsule. Lens epithelial cells, however, remain attached to the anterior capsule, and in response to surgical trauma initiate a wound-healing response that ultimately leads to light scatter and a reduction in visual quality known as posterior capsule opacification (PCO). There are two commonly-described forms of PCO: fibrotic and regenerative. Fibrotic PCO follows classically defined fibrotic processes, namely hyperproliferation, matrix contraction, matrix deposition and epithelial cell trans-differentiation to a myofibroblast phenotype. Regenerative PCO is defined by lens fibre cell differentiation events that give rise to Soemmerring's ring and Elschnig's pearls and becomes evident at a later stage than the fibrotic form. Both fibrotic and regenerative forms of PCO contribute to a reduction in visual quality in patients. This review will highlight the wealth of tools available for PCO research, provide insight into our current knowledge of PCO and discuss putative management of PCO from IOL design to pharmacological interventions.

The human capsular bag model of posterior capsule opacification

Posterior capsule opacification (PCO) is the most common complication following cataract surgery and affects millions of patients. PCO is a consequence of surgical injury promoting a wound-healing response. Following surgery, residual lens epithelial cells grow on acellular regions of the lens capsule, including the central posterior capsule. These cells can undergo fibrotic changes, such that cell transdifferentiation to myofibroblasts, matrix deposition and matrix contraction can occur, which contribute to light scatter and the need for further corrective Nd:YAG laser capsulotomy in many patients. It is therefore of great importance to better understand how PCO develops and determine better approaches to manage the condition. To achieve this, experimental systems are required, and many are available to study PCO. While there may be a number of common features associated with PCO in different species, the mechanisms governing the condition can differ. Consequently, where possible, human systems should be employed. The human capsular bag model was established in a laboratory setting on donor eyes. A capsulorhexis is performed to create an opening in the anterior capsule followed by removal of the lens fibre mass. Residual fibre cells can be removed by irrigation/aspiration and if required, an intraocular lens can be implanted. The capsular bag is isolated from the eye and transferred to a dish for culture. The human capsular bag model has played an important role in understanding the biological processes driving PCO and enables evaluation of surgical approaches, IOLs and putative therapeutic agents to better manage PCO.

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.

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.

Incidence of posterior capsular opacification requiring Nd:YAG capsulotomy after cataract surgery and implantation of enVista® MX60 IOL

PURPOSE

To evaluate incidence of posterior capsule opacification requiring Nd:YAG capsulotomy over 3 years in a large series of eyes implanted with the enVista^® MX60 Intraocular Lens (IOL).

METHODS

A university-based, single-center, observational study of patients' medical records was conducted. Uneventful cataract surgery patients with in-the-bag implantations of the enVista^® MX60 IOL with a minimum of 24 months follow-up were included in the study. Exclusion criteria were insufficient follow-up (<24 months), intraoperative complications and combined surgery. The primary outcome measure was rate of YAG laser capsulotomy, while secondary outcome measures were time to YAG laser capsulotomy and rate of glistenings.

RESULTS

A total of 245 eyes of 143 patients received the MX60 IOL and were followed in the same center. Of these, 226 eyes were included in the study. Mean age was 80.7±8.3 years and M/F ratio was 42/101 (29.4/70.6%). The mean preoperative distance (logMAR) visual acuity was 0.67±0.5, while postoperatively it was 0.31±0.5 and 0.32±0.5 at the last visit. The Mean±SD follow-up time (min-max) was 35.2±7.2, (24-48.4) months. The incidence of Nd:YAG capsulotomy over 3 years was 5/226 (2.2%). Average time between surgery and Nd:YAG capsulotomy was 32.17 months. Univariate analysis of age, gender, presence of comorbidity and baseline visual acuity found no predictive factors for capsulotomy. No glistenings were reported at any postoperative visit.

CONCLUSION

The three-year cumulative incidence of PCO requiring Nd:YAG laser capsulotomy was 2.2% for the enVista^® MX-60 IOL, with no glistenings observed during follow-up. This low rate confirms the excellent safety profile of this IOL.

Prevention of posterior capsule opacification through intracapsular hydrogen peroxide or distilled water treatment in human donor tissue

In order to determine whether posterior capsule opacification after cataract surgery, could be delayed or inhibited through the application of hydrogen peroxide (H₂O₂) or distilled water (H₂Od),we extracted lens capsules from 25 human donor eye globes. Samples were treated for 5 min with either 30 mM H₂O₂ or H₂Od or used as controls, and cultured for one month, during which dark field and tilt illumination photos were taken. These were used to observe and quantify, time until cellular growth and confluence on the posterior capsule. After culture, histological sections were stained for H&E, α-SMA, Ki-67 and vimentin and evaluated. We prevented cellular growth in 50% of H₂Od and 58% H₂O₂ of treated samples. The overall prevention of cell growth compared to cultured controls was significant for both treatments while there was no significant difference between them. In the cases where cellular growth was not prevented, both treatments significantly delay cellular growth. Until day 28 none of the treated samples of either type that had shown growth reached total confluence. All cultured controls reached total confluence before treated samples (median = day 11.5). Also, histologically, there was a clear morphological difference between cultured controls and treated samples.

The role of HIF-1α in the TGF-β2-mediated epithelial-to-mesenchymal transition of human lens epithelial cells

Human lens epithelial cells (HLE) undergo mesenchymal transition and become fibrotic during posterior capsule opacification (PCO), which is a frequent complication after cataract surgery. TGF-β2 has been implicated in this fibrosis. Previous studies have focused on the role of hypoxia-inducible factor-1α (HIF-1α) in fibrotic diseases, but the role of HIF-1α in the TGF-β2-mediated fibrosis in HLE is not known. TGF-β2 treatment (10 ng/mL, 48 h) increased the HIF-1α levels along with the EMT markers in cultured human lens epithelial cells (FHL124 cells). The increase in HIF-1α corresponded to an increase in VEGF-A in the culture medium. However, exogenous addition of VEGF-A (up to 10 ng/mL) did not alter the EMT marker levels in HLE. Addition of a prolyl hydroxylase inhibitor, dimethyloxalylglycine (DMOG, up to 10 µM), enhanced the levels of HIF-1α, and secreted VEGF-A but did not alter the EMT marker levels. However, treatment of cells with a HIF-1α translational inhibitor, KC7F2, significantly reduced the TGF-β2-mediated EMT response. This was accompanied by a reduction in the ERK phosphorylation and nuclear translocation of Snail and Slug. Together, these data suggest that HIF-1α is important for the TGF-β2-mediated EMT of human lens epithelial cells.

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.