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

Exosomes containing miR-148a-3p derived from mesenchymal stem cells suppress epithelial-mesenchymal transition in lens epithelial cells

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is responsible for the development of fibrotic cataracts, which contribute to severe visual impairment. Recent evidence has shown that mesenchymal stem cell-derived exosomes (MSC-Exo) can attenuate EMT in several tissues. However, the effect of MSC-Exo on EMT in LECs (LECs-EMT) has not been determined. In this study, we isolated exosomes from human umbilical cord MSCs (hucMSC-Exo) and evaluated their effect on LECs-EMT both in vitro and in vivo. HucMSC-Exo application significantly suppressed the expression of mesenchymal cell-associated genes while increasing the expression of epithelial cell-associated genes. Cell proliferation and migration of LECs undergoing EMT were inhibited after hucMSC-Exo treatment. The volume of EMT plaques in mice with injury-induced anterior subcapsular cataract (ASC) was significantly reduced in the hucMSC-Exo-treated group. Furthermore, miR-148a-3p was abundant in hucMSC-Exo. After transfection with miR-148a-3p inhibitor, the anti-fibrotic effect of hucMSC-Exo was attenuated in LECs-EMT. A dual-luciferase reporter assay identified PRNP as a direct target gene of miR-148a-3p. Furthermore, we verified that hucMSC-Exo inhibited LECs-EMT through the miR-148a-3p/PRNP axis and the potential downstream ERK signaling pathway. Taken together, our work reveals the inhibitory effect of hucMSC-Exo on LECs-EMT and the underlying mechanism involved, which may provide potential therapeutic options for fibrotic cataracts.

Cascade catalytic multilayer modified intraocular lens for enhanced and safer posterior capsule opacification prevention

Posterior capsule opacification (PCO) is the most common complication after cataract surgery. It is primarily caused by the proliferation, migration, and adhesion of residual lens epithelial cells within the capsular bag following phacoemulsification and intraocular lens (IOL) implantation. Although investigations of surface modification onto IOL have partially reduced PCO development in recent years, there are still challenges in long-term efficacy and intraocular biocompatibility. In this study, a cascade catalytic system is constructed using natural enzymes onto mesoporous silica nanoparticles (MSNs), which are subsequently fixed to the surface of IOL through layer-by-layer self-assemble of alternating positive and negative charges. The cascade catalytic reaction is trigged simply by glucose within the pouch to produce reactive oxygen species (ROS) without introducing any toxic drugs or external energy, attempting to minimize the possible toxic side effects to surrounding tissues. In vivo and in vitro experiments indicate the effective inhibition of PCO and favorable intraocular compatibility of the cascade catalytic platform modified IOL. More importantly, the modified IOL retains good optical performance and imaging quality, demonstrating promising prospects for application. This study provides a new possibility for enhanced and safer PCO prevention, playing great significance in clinical treatment. STATEMENT OF SIGNIFICANCE: Cascade catalytic nanoparticles-loaded multilayer modified IOL is obtained via LbL technique. The multilayer coating improves both the loading capacity and the activity of the cascade catalytic nanoparticles. The cascade catalytic reaction is trigged by glucose, producing ROS that efficiently induces apoptosis and death of remaining cells on IOL without introducing any toxic drugs or external energy. The innovative IOL provides a promising approach for enhanced and safer prevention of PCO.

Research progress on antioxidants and protein aggregation inhibitors in cataract prevention and therapy (Review)

Cataracts are primarily caused by aging or gene mutations and are the leading cause of blindness globally. As the older population increases, the number of patients with a cataract is expected to grow rapidly. At present, cataract surgery to replace the lens with an artificial intraocular lens is the principal treatment method. However, surgery has several drawbacks, including economic burdens and complications such as inflammation, xerophthalmia, macular edema and posterior capsular opacification. Thus, developing an effective non‑surgical treatment strategy is beneficial to both patients and public health. Mechanistically, cataract formation may be due to various reasons but is primarily initiated and promoted by oxidative stress and is closely associated with crystallin aggregation. In the present review, the current research progress on anti‑cataract drugs, including antioxidants and protein aggregation inhibitors is examined. It summarizes strategies for preventing and treating cataract through cell apoptosis and protein aggregation inhibition while discussing their limitations and further prospects.

Promising Pharmacological Interventions for Posterior Capsule Opacification: A Review

Phacoemulsification combined with intraocular lens implantation is the primary treatment for cataract. Although this treatment strategy benefits patients with cataracts, posterior capsule opacification (PCO) remains a common complication that impairs vision and affects treatment outcomes. The pathogenesis of PCO is associated with the proliferation, migration, and fibrogenesis activity of residual lens epithelial cells, with epithelial-mesenchymal transition (EMT) serving as a key mechanism underlying the condition. Transforming growth factor-beta 2 (TGF-β2) is a major promotor of EMT, thereby driving PCO development. Most studies have shown that drugs and miRNAs mitigate EMT by inhibiting, clearing, or eliminating LECs. In addition, targeting EMT-related signaling pathways in TGF-β2-stimulated LECs has garnered attention as a research focus. This review highlights potential treatments for PCO and details the mechanisms by which drugs and miRNAs counter EMT.

NIR-triggered thermosensitive polymer brush coating modified intraocular lens for smart prevention of posterior capsular opacification

Posterior capsule opacification (PCO) is the most common complication after cataract surgery. Drug-eluting intraocular lens (IOLs) is a promising concept of PCO treatment in modern cataract surgery. However, the large dose of drugs in IOL leads to uncontrollable and unpredictable drug release, which inevitably brings risks of overtreatment and ocular toxicity. Herein, a low-power NIR-triggered thermosensitive IOL named IDG@P(NIPAM-co-AA)-IOL is proposed to improve security and prevent PCO by synergetic controlled drug therapy and simultaneous photo-therapy. Thermosensitive polymer brushes Poly(N-isopropylacrylamide-co-Acrylic acid) (P(NIPAM-co-AA)) is prepared on IOL via surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization. Then, Doxorubicin (DOX) and Indocyanine green (ICG) co-loaded Gelatin NPs (IDG NPs) are loaded in P(NIPAM-co-AA) by temperature control. The IDG NPs perform in suit photodynamic & photothermal therapy (PTT&PDT), and the produced heat also provides a trigger for controllable drug therapy with a cascade effect. Such functional IOL shows excellent synergistic drug-phototherapy effect and NIR-triggered drug release behavior. And there is no obvious PCO occurrence in IDG@P(NIPAM-co-AA) IOL under NIR irradiation compared with control group. This proposed IDG@P(NIPAM-co-AA)-IOL serves as a promising platform that combines phototherapy and drug-therapy to enhance the therapeutic potential and medication safety for future clinical application of PCO treatment.

Current Approach to the Pathogenesis of Diabetic Cataracts

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

The Role of Resveratrol in Eye Diseases—A Review of the Literature

Resveratrol (3,5,4′-trans-trihydroxystilbene) is a polyphenolic phytoalexin belonging to the stilbene family. It is commonly found in grape skins and seeds, as well as other plant-based foods. Oxidative stress and inflammation play a key role in the initiation and progression of age-related eye disorders (glaucoma, cataracts, diabetic retinopathy, and macular degeneration) that lead to a progressive loss of vision and blindness. Even though the way resveratrol affects the human body and the course of many diseases is still the subject of ongoing scientific research, it has been shown that the broad spectrum of anti-inflammatory and neuroprotective properties of resveratrol has a beneficial effect on eye tissues. In our research, we decided to analyze the current scientific literature on resveratrol, its possible mechanisms of action, and its therapeutic application in order to assess its effectiveness in eye diseases.

Oxidative stress induces inflammation of lens cells and triggers immune surveillance of ocular tissues

Recent reports have challenged the notion that the lens is immune-privileged. However, these studies have not fully identified the molecular mechanism(s) that promote immune surveillance of the lens. Using a mouse model of targeted glutathione (GSH) deficiency in ocular surface tissues, we have investigated the role of oxidative stress in upregulating cytokine expression and promoting immune surveillance of the eye. RNA-sequencing of lenses from postnatal day (P) 1-aged Gclcf/f;Le-CreTg/- (KO) and Gclcf/f;Le-Cre-/- control (CON) mice revealed upregulation of many cytokines (e.g., CCL4, GDF15, CSF1) and immune response genes in the lenses of KO mice. The eyes of KO mice had a greater number of cells in the aqueous and vitreous humors at P1, P20 and P50 than age-matched CON and Gclcw/w;Le-CreTg/- (CRE) mice. Histological analyses revealed the presence of innate immune cells (i.e., macrophages, leukocytes) in ocular structures of the KO mice. At P20, the expression of cytokines and ROS content was higher in the lenses of KO mice than in those from age-matched CRE and CON mice, suggesting that oxidative stress may induce cytokine expression. In vitro administration of the oxidant, hydrogen peroxide, and the depletion of GSH (using buthionine sulfoximine (BSO)) in 21EM15 lens epithelial cells induced cytokine expression, an effect that was prevented by co-treatment of the cells with N-acetyl-l-cysteine (NAC), a antioxidant. The in vivo and ex vivo induction of cytokine expression by oxidative stress was associated with the expression of markers of epithelial-to-mesenchymal transition (EMT), α-SMA, in lens cells. Given that EMT of lens epithelial cells causes posterior capsule opacification (PCO), we propose that oxidative stress induces cytokine expression, EMT and the development of PCO in a positive feedback loop. Collectively these data indicate that oxidative stress induces inflammation of lens cells which promotes immune surveillance of ocular structures.

TGF-β2-induced circ-PRDM5 regulates migration, invasion, and EMT through the miR-92b-3p/COL1A2 pathway in human lens epithelial cells

CircRNA circ-PRDM5 (PR/SET domain 5) (circ-PRDM5) is overexpressed in age-related cataracts. Nevertheless, the biological role of circ-PRDM5 in posterior capsule opacities (PCO) (a common complication after cataract surgery) is unclear. Human lens epithelial cells SRA01/04 (LECs) were stimulated with TGF-β2 (transforming growth factor beta-2) to mimic the PCO model in vitro. Cell viability, migration, and invasion were determined by MTT, transwell, or wound-healing assays. Protein levels of EMT (epithelial-to-mesenchymal transition) markers and COL1A2 (collagen type I alpha 2 chain) were analyzed by western blotting (WB). Relative expression of circ-PRDM5, miR-92b-3p, and COL1A2 mRNA was analyzed by qRT-PCR. The targeting relationship was confirmed by dual-luciferase reporter and RIP assays. We observed that circ-PRDM5 and COL1A2 were upregulated in PCO tissues and TGF-β2-treated LECs, while miR-92b-3p was downregulated. Both circ-PRDM5 and COL1A2 knockdown impaired TGF-β2-induced LEC migration, invasion, and EMT. Also, circ-PRDM5 could adsorb miR-92b-3p to regulate COL1A2 expression. Furthermore, miR-92b-3p inhibitor offset circ-PRDM5 knockdown-mediated influence on migration, invasion, and EMT of LECs under TGF-β2 stimulation. Also, COL1A2 overexpression overturned the repressive influence of miR-92b-3p mimic on TGF-β2-induced LEC migration, invasion, and EMT. In summary, TGF-β2-induced circ-PRDM5 facilitated LEC migration, invasion, and EMT by adsorbing miR-92b-3p and increasing COL1A2 expression, offering new insights into the development of PCO.

Drug-eluting intraocular lens with sustained bromfenac release for conquering posterior capsular opacification

Cataract is the leading cause of visual impairment, and posterior capsular opacification (PCO) is the most common long-term complication of modern cataract surgery, which can cause severe visual impairment after surgery. The proliferation, migration, and epithelial-mesenchymal transition (EMT) of residual lens epithelial cells (LECs) stimulated by growth factors and cytokines, are the key pathological mechanisms involved in the development of PCO. This study demonstrated that non-steroidal anti-inflammatory drug (NSAID), bromfenac, was capable of effectively inhibiting cell migration, overexpression of EMT markers, such as fibronectin (FN), matrix metalloproteinase 2 (MMP2), α-smooth muscle actin (α-SMA), and transcription factor Snail, and extracellular signal-regulated kinase (ERK)/glycogen synthase kinase-3β (GSK-3β) signaling induced by transforming growth factor-β2 (TGF-β2) in vitro. The inhibitory effect of bromfenac on TGF-β2-induced EMT was also verified on a primary lens epithelial cell model using human anterior capsules. Furthermore, based on ultrasonic spray technology, we developed a drug-eluting intraocular lens (IOL) using poly (lactic-co-glycolic acid) (PLGA) with sustained bromfenac release ability for the prevention of PCO development. In the rabbit models of cataract surgery, bromfenac-eluting IOL exhibited remarkable PCO prevention and inflammation suppression effects with excellent biocompatibility. In conclusion, bromfenac can inhibit TGF-β2-induced cell migration and the EMT of LECs via ERK/GSK-3β/Snail signaling. The present study offers a novel approach for preventing PCO through PLGA-based drug sustained-release IOLs.

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Bromfenac inhibited TGF-β2-induced migration and EMT of LECs through ERK/GSK-3β/Snail signaling.

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Drug-eluting IOLs with sustained bromfenac release were developed based on ultrasonic spray technology.

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Bromfenac-eluting IOLs exhibited remarkable PCO prevention and inflammation suppression effects in vivo.

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Bromfenac-eluting IOLs hold great potential for clinical application of PCO prevention.

New Highlights of Resveratrol: A Review of Properties against Ocular Diseases

Eye diseases are currently a major public health concern due to the growing number of cases resulting from both an aging of populations and exogenous factors linked to our lifestyles. Thus, many treatments including surgical pharmacological approaches have emerged, and special attention has been paid to prevention, where diet plays a preponderant role. Recently, potential antioxidants such as resveratrol have received much attention as potential tools against various ocular diseases. In this review, we focus on the mechanisms of resveratrol against ocular diseases, in particular age-related macular degeneration, glaucoma, cataract, diabetic retinopathy, and vitreoretinopathy. We analyze, in relation to the different steps of each disease, the resveratrol properties at multiple levels, such as cellular and molecular signaling as well as physiological effects. We show and discuss the relationship to reactive oxygen species, the regulation of inflammatory process, and how resveratrol can prevent ocular diseases through a potential epigenetic action by the activation of sirtuin-1. Lastly, various new forms of resveratrol delivery are emerging at the same time as some clinical trials are raising more questions about the future of resveratrol as a potential tool for prevention or in therapeutic strategies against ocular diseases. More preclinical studies are required to provide further insights into RSV's potential adjuvant activity.

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.

Biochemical Evidence Indicates the Preventive Effect of Resveratrol and Nicotinamide in the Treatment of STZ-induced Diabetic Cataract

PURPOSE

High glucose level is a strong initiator of both oxidative stress and DNA damage to various cellular proteins. This activates the poly ADP-ribose polymerase (PARP) enzyme, which is responsible for disturbing physiological energy metabolic homeostasis. The present study aimed to elucidate the association between stress and the PARP pathway by using resveratrol (RSV) and nicotinamide (NAM, PARP inhibitor) to treat diabetic cataract.

METHOD

Albino rats were used for the experimental study. A single streptozotocin administration (55 mg/kg, i.p.) prompted diabetes in the animals. The experimental groups were the normal group (non-diabetic) and the diabetic groups: the diabetic control animals (group D), the diabetic animals treated with RSV at 40 mg/kg/day, i.p. (D+ RSV group), NAM at 100 and 300 mg/kg/day, i.p. (D+ NAM100, D+ NAM300 groups, respectively), and a combination of RSV and NAM i.p. (D+ RSV+NAM100 = Combi 1 group, D+ RSV+NAM300 = Combi 2 group). Glucose levels and the eyes were examined biweekly; various cataractogenic parameters in the lenses were examined after completion of the eight-week experimental protocol.

RESULTS

Compared to diabetic control, RSV monotherapy significantly decreased hyperglycemia and other lenticular alterations. NAM at the high dose only showed beneficial effects without altering the blood glucose level, lenticular aldose reductase (AR) activity, and sorbitol content, primarily restored the lenticular NAD level and decreased oxidative stress in diabetic rats. These findings regarding NAM treatment indicate that a pathway other than the antioxidant defense system and the polyol pathway, which might be due to PARP inhibition, is involved in diabetic cataracts. Moreover, compared to RSV monotherapy, combination treatments were effective.

CONCLUSION

These results indicate that hyperglycemia and oxidative-osmotic-nitrosative stress play central roles in the pathophysiology of diabetic cataracts. Moreover, our study also revealed that concurrent treatment with the RSV and NAM may prove useful in the pharmacotherapy of diabetes and its secondary complications such as cataract.

Research Progress of Drug Prophylaxis for Lens Capsule Opacification after Cataract Surgery

Phacoemulsification combined with intraocular lens (IOL) implantation is the international standard operation procedure for cataract and has been generalized worldwide. However, lens capsule opacification, one of the common complications after cataract surgery, impacts the recovery of patients' visual function to a large extent. Lens capsule opacification has two types, anterior capsule opacification (ACO) and posterior capsule opacification (PCO), according to the location. There is not an accepted approach to treat ACO. Nd : YAG laser capsulotomy, the common treatment of PCO, can effectively improve the vision, but may cause a series of complications and is inappropriate for children who are too young to cooperate with this treatment. It is generally known that the responses of lens epithelial cells (LECs) after cataract surgery, including cell proliferation, migration, and epithelial-mesenchymal transition (EMT), play a key role in the pathogenesis of lens capsule opacification. Scholars found that substantial drugs can reduce the occurrence of lens capsule opacification by inhibiting, clearing, or killing LECs, and made great efforts as well as innovations on the exploration of drug species or modes of administration. This article is a systematic interpretation and elaboration about how to prevent lens capsule opacification after cataract surgery via different drugs.

Long Noncoding RNA NEAT1 Regulates TGF-β2-Induced Epithelial-Mesenchymal Transition of Lens Epithelial Cells through the miR-34a/Snail1 and miR-204/Zeb1 Pathways

The aim of this study was to explore whether the long noncoding RNA nuclear paraspeckle assembly transcript 1 (NEAT1)/miR-34a/Snail1 and NEAT1/miR-204/Zeb1 pathways are involved in epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs). Primary human LECs (HLECs) were separated and cultured. Our results identified that TGF-β2 induces NEAT1 overexpression in a dose-dependent manner and a time-dependent manner. Additionally, TGF-β2 induced downregulation of E-cadherin and upregulation of fibronectin in primary HLECs through a NEAT1-dependent mechanism. Microarray analysis showed that NEAT1 overexpression inhibited the miR-34a and miR-204 levels in the LECs. The expression of miR-34a and miR-204 was decreased, and the levels of Snail1 and Zeb1 were elevated in human posterior capsule opacification- (PCO-) attached LECs and the LECs obtained from anterior subcapsular cataract (ASC) by quantitative RT-PCR (qRT-PCR). Mechanistic studies revealed that NEAT1 negatively regulates miR-34a or miR-204, and miR-34a or miR-204 directly targets Snail1 or Zeb1 by luciferase assay and RNA-binding protein immunoprecipitation assay, respectively. Overall, the NEAT1/miR-34a/Snail1 and NEAT1/miR-204/Zeb1 pathways are involved in TGF-β2-induced EMT of HLECs. In summary, TGF-β2 induces NEAT1 overexpression, which in turn suggests that NEAT1 acts as a ceRNA targeting Snail1 or Zeb1 by binding miR-34a or miR-204, and promotes the progression of EMT of LECs.

Supercritical fluid technology for the development of innovative ophthalmic medical devices: Drug loaded intraocular lenses to mitigate posterior capsule opacification

Supercritical impregnation technology was applied to load acrylic intraocular lenses (IOLs) with methotrexate to produce a sustained drug delivery device to mitigate posterior capsule opacification. Drug release kinetics were studied in vitro and used to determine the drug loading. Loaded IOLs and control IOLs treated under the same operating conditions, but without drug, were implanted ex vivo in human donor capsular bags. The typical cell growth was observed and immunofluorescence staining of three common fibrosis markers, fibronectin, F-actin and α-smooth muscle actin was carried out. Transparent IOLs presenting a sustained release of methotrexate for more than 80 days were produced. Drug loading varying between 0.43 and 0.75 ± 0.03 µg_drug·mg^-1_IOL were obtained when varying the supercritical impregnation pressure (8 and 25 MPa) and duration (30 and 240 min) at 308 K. The use of ethanol (5 mol%) as a co-solvent did not influence the impregnation efficiency and was even unfavorable at certain conditions. Even if the implantation of methotrexate loaded IOLs did not lead to a statistically significant variation in the duration required for a full cell coverage of the posterior capsule in the human capsular bag model, it was shown to reduce fibrosis by inhibiting epithelial-mesenchymal transformation. The innovative application presented has the potential to gain clinical relevance.

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.