The role of thrombin in proliferative vitreoretinopathy

Intraocular Fibrin Glue to Lower the Risk of Postoperative Vitreous Hemorrhage After Diabetic Pars Plana Vitrectomy

PURPOSE

To investigate the use of intraocular fibrin glue to lower the risk of vitreous hemorrhage (VH) after pars plana vitrectomy (PPV) in eyes with diabetic VH or traction retinal detachment.

METHODS

A matched, case-control, single-surgeon, pilot study of patients undergoing PPV for diabetic VH or traction retinal detachment with versus without fibrin glue was performed.

RESULTS

Thirty-nine patients (13 glue and 26 control patients) were included. In the glue group, mean (SD) logarithm of the minimum angle of resolution visual acuity (Snellen) significantly improved from 1.53 (0.6) (20/678) to 0.99 (0.9) (20/195) at postoperative month 6 ( P = 0.03). In the control group, mean logarithm of the minimum angle of resolution visual acuity also improved from 1.45 (0.8) (20/564) to 1.17 (0.9) (20/296) at postoperative Month 6 ( P = 0.3). Persistent post-PPV VH was similar between the 2 groups (15.4% in both groups, P > 0.99). However, early recurrent VH (<3 months post-PPV) was seen in 34.6% in the control group and none in the glue group ( P = 0.02). No intraocular inflammatory events were seen in the glue group.

CONCLUSION

Intraocular fibrin glue may be a safe adjuvant in diabetic vitrectomy and may reduce the rate of early recurrent postoperative VH.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Dabigatran and Wet AMD, Results From Retinal Pigment Epithelial Cell Monolayers, the Mouse Model of Choroidal Neovascularization, and Patients From the Medicare Data Base

Background

Age-related macular degeneration (AMD), the leading cause of irreversible blindness in elderly Caucasian populations, includes destruction of the blood-retina barrier (BRB) generated by the retinal pigment epithelium-Bruch’s membrane complex (RPE/BrM), and complement activation. Thrombin is likely to get access to those structures upon BRB integrity loss. Here we investigate the potential role of thrombin in AMD by analyzing effects of the thrombin inhibitor dabigatran.

Material and Methods

MarketScan data for patients aged ≥65 years on Medicare was used to identify association between AMD and dabigatran use. ARPE-19 cells grown as mature monolayers were analyzed for thrombin effects on barrier function (transepithelial resistance; TER) and downstream signaling (complement activation, expression of connective tissue growth factor (CTGF), and secretion of vascular endothelial growth factor (VEGF)). Laser-induced choroidal neovascularization (CNV) in mouse is used to test the identified downstream signaling.

Results

Risk of new wet AMD diagnosis was reduced in dabigatran users. In RPE monolayers, thrombin reduced TER, generated unique complement C3 and C5 cleavage products, led to C3d/MAC deposition on cell surfaces, and increased CTGF expression via PAR1-receptor activation and VEGF secretion. CNV lesion repair was accelerated by dabigatran, and molecular readouts suggest that downstream effects of thrombin include CTGF and VEGF, but not the complement system.

Conclusions

This study provides evidence of association between dabigatran use and reduced exudative AMD diagnosis. Based on the cell- and animal-based studies, we suggest that thrombin modulates wound healing and CTGF and VEGF expression, making dabigatran a potential novel treatment option in AMD.

A Novel Role of IL13Rα2 in the Pathogenesis of Proliferative Vitreoretinopathy

Proliferative vitreoretinopathy (PVR), an inflammatory and fibrotic blinding disease, is still a therapeutic challenge. Retinal pigment epithelial (RPE) cells dislodged in the vitreous play a central role in the PVR pathogenesis. To identify potential novel contributors to the pathogenesis of PVR, we investigated a profile of vitreous-induced changes in ARPE-19 cells by RNA sequencing. Bioinformatics analysis of the sequencing data showed that there were 258 genes up-regulated and 835 genes down-regulated in the ARPE-19 cells treated with human vitreous. Among these genes, there were three genes related to eye disease with more than threefold changes. In particular, quantitative PCR and western blot results showed that interleukin 13 receptor (IL13R)α2 that is over-expressed in a variety of cancers was up-regulated more than three times in the vitreous-treated ARPE-19 cells. Immunofluorescence analysis indicated that interleukin-13 receptor subunit α2 (IL13Rα2) was highly expressed in ARPE-19 cells within epiretinal membranes from patients with PVR. Importantly, blocking IL13Rα2 with its neutralizing antibody significantly inhibited vitreous-induced contraction of ARPE-19 cells, suggesting a novel role of IL13Rα2 in the PVR pathogenesis. These findings will improve our understanding of the molecular mechanisms by which PVR develops and provides potential targets for PVR therapeutics.

AdipoRon negatively regulates proliferation and migration of ARPE-19 human retinal pigment epithelial cells

Adiponectin is an adipokine playing important roles in metabolic, inflammatory and proliferative processes. At the time of surgery for rhegmatogenous retinal detachment, an altered expression of adipokines has been associated with the development of future proliferative vitreoretinopathy (PVR); this evidence as well as the presence of adiponectin receptors in ocular tissues and cell lines suggests a role of adiponectin in the physio-pathology of ocular conditions. Here, we investigated the effects of AdipoRon, an adiponectin agonist, on ARPE-19, a human retinal pigment epithelial cell line after confirming the expression of AdipoR1, AdipoR2, T-cadherin receptors. We evaluated the effects of AdipoRon in terms of vitality, survival, and migration; furthermore, we investigated the potential effects of AdipoRon on the inflammatory state of ARPE-19 cells analysing the levels of IL-10, VEGF, MCP-1 and IL-6 cytokines. Our findings indicated that AdipoRon, in a time and dose-dependent manner, reduces cell proliferation, migration, and colony formation of ARPE-19 cells. On the contrary, AdipoRon administration does not affect the expression of the tested cytokines. In conclusion, our results indicated that AdipoRon, may constitute an endogenous inhibitor of retinal pigment epithelial cell proliferation and migration, both processes deeply involved in development of PVR. Since PVR are characterized by an aberrant growth, migration and dedifferentiation of retinal pigment epithelial cells, our data contribute to open new fields of research to develop innovative therapeutic targets. Further studies are needed to clarify the effects of AdipoRon and of other small-molecule adiponectin analogs on retinal epithelium to clarify the functional role of adiponectin.

Repression of Smad4 by MicroRNA-1285 moderates TGF-β-induced epithelial-mesenchymal transition in proliferative vitreoretinopathy

The purpose of this study was to assess whether microRNA (miR)-1285 can suppress the epithelial-mesenchymal transition (EMT) in retinal pigment epithelial cells. Expression of miR-1285 was evaluated using quantitative real-time polymerase chain reaction (RT-qPCR). The features of EMT were assessed using Western blotting, immunocytochemical staining, scratch wound healing tests, modified Boyden chamber assay, and collagen gel contraction assay. A rabbit model of proliferative vitreoretinopathy (PVR) was used for in vivo testing, which involved the induction of PVR by injection of transfected ARPE cells into the vitreous chamber. Luciferase reporter assay was performed to identify the putative target of miR-1285. The expression of miR-1285 was downregulated in ARPE-19 cells treated with transforming growth factor (TGF)-β. Overexpression of miR-1285 led to upregulation of zonula occludens-1, downregulation of α-smooth muscle actin and vimentin, cell migration and cell contractility-all EMT features-in the TGF-β2-treated ARPE-19 cells. The reporter assay indicated that the 3' untranslated region of Smad4 was the direct target of miR1285. PVR progression was alleviated in the miR-1285 transfected rabbits. In conclusion, overexpression of miR-1285 attenuates TGF-β2-induced EMT in a rabbit model of PVR, and the effect of miR-1285 in PVR is dependent on Smad4. Further research is warranted to develop a feasible therapeutic approach for the prevention and treatment of PVR.

Activated Blood Coagulation Factor X (FXa) Contributes to the Development of Traumatic PVR Through Promoting RPE Epithelial-Mesenchymal Transition

Purpose

Uncontrolled coagulation reactions contribute to pathological fibroproliferation in several organs, and yet their role in proliferative vitreoretinopathy (PVR) remains to be elucidated. In this study, we evaluated the profibrotic effects of FXa in RPE cells and in a mouse model of PVR.

Methods

FXa levels in the eyes of traumatic PVR patients and rabbit models of mechanical ocular trauma was measured by ELISA and immunohistochemistry. FXa-induced RPE EMT was assessed by examining cell proliferation, migration, tight junction changes, and expression of fibrotic markers. For in vivo study, FXa was injected into dispase-injured eyes, then intraocular fibrosis was evaluated by histological analysis and Western blotting. The therapeutic effect of FXa inhibitor was also examined in PVR mouse models.

Results

Vitreous FXa were higher in patients with traumatic PVR compared to patients with macular hole. Moreover, expressions of FXa and PAR1 were found in the epiretinal membranes from traumatic PVR patients. Vitreous FXa were markedly increased after mechanical ocular trauma in rabbits. In vitro, FXa stimulated RPE EMT characterized as ZO-1 disruption, compromised cell polarity, and increased fibronectin expressions. Co-injection of FXa and dispase in mice induced more severely damaged retinal structures, and increased α-SMA expressions than FXa or dispase treatment alone. Oral FXa or thrombin inhibitors significantly blocked intraocular fibrosis in PVR mouse models. FXa promoted phospho-activation of p38 in ARPE19 cells, which was dependent on PAR1. Moreover, TGF-βR inhibitor also significantly alleviated FXa-induced intraocular fibrosis in mice.

Conclusions

FXa promotes intraocular fibrosis in mice via mechanisms involving RPE activation.

SINGLE NUCLEOTIDE POLYMORPHISMS IN RETINAL DETACHMENT PATIENTS WITH AND WITHOUT PROLIFERATIVE VITREORETINOPATHY

PURPOSE

To investigate differences in genotype distributions of single nucleotide polymorphisms within genes, encoding inflammatory mediators, among patients with rhegmatogenous retinal detachment (RRD) and patients with proliferative vitreoretinopathy (PVR).

METHODS

A genetic association study was performed on 191 Slovenian patients, divided into 2 groups: 113 RRD patients with PVR and 78 RRD patients without PVR. Genotype distributions were investigated within the following 13 single nucleotide polymorphisms: rs3760396 (CCL2), rs9990554 (FGF2), rs17561 (IL1A), rs2069763 (IL2), rs1800795 (IL6), rs1800871 (IL10), rs3008 (JAK3), rs2229094 (LTA), rs1042522 (TP53), rs7656613 (PDGFRA), rs7226855 (SMAD7), rs1800471 (TGFB1), and rs1800629 (TNF).

RESULTS

Differences in genotype distributions between patients with RRD with or without PVR were detected in rs1800795 (IL6) (P = 0.04), rs1800871 (in the vicinity of the IL10) (P = 0.034), and rs1800471 (TGFB1) (P = 0.032). After adjustment none of the 13 analyzed single nucleotide polymorphisms showed statistically significant associations in single nucleotide polymorphism genotype distributions between patients with RRD with and without PVR.

CONCLUSION

Further research is needed, particularly expanded multicentric population-based studies, to clarify the issue of genetic contribution to PVR from different genetic, clinical, and population-based aspects.

Hirudo (Leech) for proliferative vitreous retinopathy: A protocol for systemic review and meta-analysis

INTRODUCTION

Proliferative vitreous retinopathy (PVR) is characterized by proliferation of cells and contraction of membranes on either the retinal surface or in the vitreous cavity, which leads to retinal detachment and visual impairment. PVR is commonly seen in patients with rhegmatogenous retinal detachment and diabetic retinopathy, which seriously affects the patient's work and life. Previous studies indicated that Hirudo (Leech) or compound prescription containing Hirudo (Leech) for treatment of PVR would be effective. However, due to the lack of evidence, there are no specific methods or suggestions, so it is necessary to carry out systematic evaluations on Hirudo (Leech) for PVR and provide effective evidence for further research.

METHODS AND ANALYSIS

The following 8 databases will be searched: Cochrane Central Register of Controlled Trials, PubMed, MEDLINE, EMBASE, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, VIP Database, and Wanfang Database. All randomized controlled trials in English or Chinese related to Hirudo (Leech) for PVR will be included. Outcomes will include change in Vitreous opacity, Vision changes, production of the anterior macular membrane, and retinal detachment again. The incidence of adverse events will be assessed for safety evaluation. Study inclusion, data extraction and quality assessment will be performed independently by 2 reviewers. Assessment of risk of bias and data synthesis will be performed using Review Manager V.5.3.

RESULTS

In this systematic review and meta-analysis, we will synthesize the studies to assess the safety and efficacy of Hirudo (Leech) for PVR.

CONCLUSION

The summary of our study will clarify whether Hirudo (Leech) therapy could be an efficient and safe method for PVR, which can further guide the promotion and application of it.

OPEN SCIENCE FRAMEWORK OSF REGISTRATION NUMBER

10.17605/OSF.IO/FP7VG (https://osf.io/fp7vg).

Macular tractional retinal detachment: A rare complication of blunt trauma

Traumatic rhegmatogenous retinal detachment after blunt ocular trauma is a known entity. A tractional macular detachment occurring posttrauma without a retinal break is a unique presentation. A 25-year-old gentleman after blunt ocular trauma with a ball presented a week later with a vision of 20/800, large subretinal bleed and resolving vitreous hemorrhage in the right eye. Three weeks later, an extensive glial proliferation at the posterior pole and macular tractional retinal detachment was noted with the worsening of visual acuity. A vitrectomy, membrane peeling, and silicone oil tamponade with a subsequent silicone oil removal at 6 months stabilized the macula, and vision improved to 20/120. A tractional macular detachment post blunt trauma is rare albeit an interesting occurrence, which can be effectively managed with vitrectomy and allied procedures.

Thrombin-activated PAR1 membrane expression is regulated by Rab11a-RCP complex dissociation

PAR1 activation by thrombin promotes intracellular signaling leading to RPE cell transformation, proliferation, and migration, characteristic of fibroproliferative eye diseases. Due to the cleavage of PAR1 N-terminal domain, carried by thrombin, the arrest of PAR1 signaling is achieved by transport into lysosomes and degradation. Recent findings suggest that the GTPase Rab11a in conjunction with its effector RCP may direct PAR1 to lysosomes. Hereby we demonstrate that thrombin-induced PAR1 internalization and lysosomal targeting requires the disassembly of the Rab11a/RCP complex, and that this process depends on thrombin-induced intracellular calcium increase and calpain activation. These findings unveil a novel mechanism that regulates thrombin activated PAR1 internalization and degradation.

Extracellular Vesicles and MicroRNA: Putative Role in Diagnosis and Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is a complex, progressive, and heterogenous retinal degenerative disease associated with diabetes duration. It is characterized by glial, neural, and microvascular dysfunction, being the blood-retinal barrier (BRB) breakdown a hallmark of the early stages. In advanced stages, there is formation of new blood vessels, which are fragile and prone to leaking. This disease, if left untreated, may result in severe vision loss and eventually legal blindness. Although there are some available treatment options for DR, most of them are targeted to the advanced stages of the disease, have some adverse effects, and many patients do not adequately respond to the treatment, which demands further research. Oxidative stress and low-grade inflammation are closely associated processes that play a critical role in the development of DR. Retinal cells communicate with each other or with another one, using cell junctions, adhesion contacts, and secreted soluble factors that can act in neighboring or long-distance cells. Another mechanism of cell communication is via secreted extracellular vesicles (EVs), through exchange of material. Here, we review the current knowledge on deregulation of cell-to-cell communication through EVs, discussing the changes in miRNA expression profiling in body fluids and their role in the development of DR. Thereafter, current and promising therapeutic agents for preventing the progression of DR will be discussed.

Inflammation, angiogenesis and coagulation interplay in a variety of retinal diseases

PURPOSE

To evaluate and correlate levels of various proteins involved in coagulation, inflammation and angiogenesis processes in the vitreous of patients with different vitreoretinal pathologies.

METHODS

Vitreous samples were collected from patients scheduled for pars plana vitrectomy for the treatment of rhegmatogenous retinal detachment (RRD), vitreous haemorrhage or tractional retinal detachment associated with proliferative diabetic retinopathy (PDR). Macular hole and epiretinal membrane served as controls. Levels of vascular endothelial growth factor, thrombin-antithrombin III complex, interleukin-8, tissue factor, thrombomodulin, P-selectin, D-dimer and tissue factor pathway inhibitor were compared among the vitreoretinal pathology groups.

RESULTS

Compared to controls, patients with PDR had significantly higher levels of thrombin-antithrombin III complex (p < 0.001), vascular endothelial growth factor (p < 0.001), D-dimer (p = 0.038) and interleukin-8 (p = 0.04), and patients with RRD group had significantly higher levels only of thrombin-antithrombin III complex (p < 0.001). There was a significant linear correlation between levels of P-selectin and D-dimer (p = 0.003), P-selectin and interleukin-8 (p < 0.001), and D-dimer and IL-8 (p = 0.007). These correlations were particularly strong in the PDR group compared to the other groups.

CONCLUSION

Patients with PDR manifest high coagulative and angiogenic activity in the vitreous. These pathways are highly correlated with the inflammatory cascade.

PPARα activation directly upregulates thrombomodulin in the diabetic retina

Two large clinical studies showed that fenofibrate, a commonly used peroxisome proliferator-activated receptor α (PPARα) agonist, has protective effects against diabetic retinopathy. However, the underlying mechanism has not been clarified. We performed genome-wide analyses of gene expression and PPARα binding sites in vascular endothelial cells treated with the selective PPARα modulator pemafibrate and identified 221 target genes of PPARα including THBD, which encodes thrombomodulin (TM). ChIP-qPCR and luciferase reporter analyses showed that PPARα directly regulated THBD expression via binding to the promoter. In the rat diabetic retina, treatment with pemafibrate inhibited the expression of inflammatory molecules such as VCAM-1 and MCP1, and these effects were attenuated by intravitreal injection of small interfering RNA targeted to THBD. Furthermore, pemafibrate treatment inhibited diabetes-induced vascular leukostasis and leakage through the upregulation of THBD. Our results indicate that PPARα activation inhibits inflammatory and vasopermeable responses in the diabetic retina through the upregulation of TM.

Spectral-Domain Optical Coherence Tomography Analysis of Fibrotic Lesions in Neovascular Age-Related Macular Degeneration

PURPOSE

To describe the spectral-domain optical coherence tomography (OCT) features of fibrotic lesions associated with neovascular age-related macular degeneration (nAMD) and to outline the progression pathways from initial macular choroidal neovascular lesions (CNVs) to fibrosis.

METHODS

Patients with nAMD were retrospectively included when macular subretinal fibrosis was present. Fibrosis was categorized using spectral-domain OCT with respect to retinal pigment epithelium (RPE) in 836 spectral-domain OCT slices from 44 eyes of 39 patients. In addition, in 47 distinct eyes, 4181 spectral-domain OCT slices were retrospectively reviewed to longitudinally assess progression from the initial lesion to the final fibrosis.

RESULTS

Cross-sectional analysis classified fibrosis on spectral-domain OCT slices, as type A if located underneath the RPE, as type B if located above the RPE, and as type C if the remaining RPE was undistinguishable. The longitudinal analysis series revealed 3 progression pathways from the original CNV: 1) progression to type A, followed by RPE erosion and subretinal hyperreflective material, then type B and type C fibroglial lesion (FGL; 17/47 eyes); 2) progression to type B then type C FGL (17/47 eyes); and 3) persistence of type A with development of a flat, fibroatrophic lesion (13/47 eyes). Subretinal hyperreflective material, macular hemorrhage, or RPE tear occurred in 14 of 47, 13 of 47, and 10 of 47 eyes, respectively.

CONCLUSION

This spectral-domain OCT analysis identified various patterns of macular fibrosis in eyes with nAMD. Three pathways of progression to fibrosis were described including the well-established pathway of type 2 CNV progression to FGL and the progression of type 1 fibrovascular CNV to FGL or fibroatrophic lesion.

Inflammatory mediators of proliferative vitreoretinopathy: hypothesis and review

Purpose

To review the role of inflammatory mediators in proliferative vitreoretinopathy (PVR) development and the current treatment for PVR prevention.

Methods

A PubMed search was carried out using these keywords “PVR,” “inflammatory mediators,” “growth factors,” “cytokines” and “treatment.” Studies regarding inflammatory mediators and PVR therapy were included and published up to December 2019.

Results

Inflammatory mediators, namely growth factors and cytokines, have been implicated in the occurrence and development of PVR. Among various inflammatory mediators, transforming growth factor-β, platelet-derived growth factor, interleukin-6, interleukin-8 and tumor necrosis factor-α are considered to be particularly important. In this review, we focus on the hypothesis that growth factors and cytokines are involved in the development of PVR, and current treatment for the prevention of PVR.

Conclusion

We support the hypothesis that growth factors and cytokines may participate in the complex process of PVR development. More importantly, the identification of inflammatory mediators provides novel and efficacious therapeutic targets for the treatment of PVR.

Inflammatory and Fibrogenic Factors in Proliferative Vitreoretinopathy Development

Purpose

Proliferative vitreoretinopathy (PVR) occurs in 5%-10% of rhegmatogenous retinal detachment cases and is the principle cause for failure of retinal reattachment surgery. Although there are a number of surgical adjunctive agents available for preventing the development of PVR, all have limited efficacy. Discovering predictive molecular biomarkers to determine the probability of PVR development after retinal reattachment surgery will allow better patient stratification for more targeted drug evaluations.

Methods

Narrative literature review.

Results

We provide a summary of the inflammatory and fibrogenic factors found in ocular fluid samples during the development of retinal detachment and PVR and discuss their possible use as molecular PVR predictive biomarkers.

Conclusions

Studies monitoring the levels of the above factors have found that few if any have predictive biomarker value, suggesting that widening the phenotype of potential factors and a combinatorial approach are required to determine predictive biomarkers for PVR.

Translational Relevance

The identification of relevant biomarkers relies on an understanding of disease signaling pathways derived from basic science research. We discuss the extent to which those molecules identified as biomarkers and predictors of PVR relate to disease pathogenesis and could function as useful disease predictors. (http://www.umin.ac.jp/ctr/ number, UMIN000005604).

Combined cellular and soluble mediator analysis for improved diagnosis of vitreoretinal lymphoma

Purpose

Primary vitreoretinal lymphoma [(P)VRL]) is a rare malignancy of the eye localized in the retina, vitreous or choroid. Here, we aim to determine the value of the combination of innovative diagnostic methods for accurate differentiation between (P)VRL and non‐(P)VRL in patients with suspect uveitis or vitritis.

Methods

Multicolour flow cytometric immunophenotyping of cells in the vitreous samples was performed using the EuroFlow small sample tube. Additionally, cytokines/chemokines and growth factors were measured in the vitreous specimens using a multiplex immunoassay. Data were evaluated in predefined clinical subgroups using omniviz unsupervised Pearson's correlation visualization and unsupervised heatmap analysis.

Results

A total of 53 patients were prospectively included in the period 2012–2015. In the (P)VRL subgroup (n = 10), nine cases showed aberrant surface membrane immunoglobulin (SmIg) light chain expression. In the non‐(P)VRL group (n = 43) clearly skewed SmIg light chain expression was observed in two multiple sclerosis‐related uveitis cases, but not in other uveitis types. Soluble mediator measurement revealed high interleukin (IL)‐10/IL‐6 ratios, and high IL‐1RA levels in 9/10 (P)VRL cases, but not in any non‐(P)VRL case. Further correlation and heatmap analysis revealed a minimal signature of cellular parameters (CD19+ B cells, aberrant SmIg light chain expression) and cytokine parameters (IL‐10/IL‐6 ratio >1, high IL‐10, high IL‐1 RA, high monocyte chemotactic protein‐1, high macrophage inflammatory protein‐1β) to reliably distinguish (P)VRL from non‐(P)VRL.

Conclusion

Here, we show the power of a combined cellular and proteomics strategy for detecting (P)VRL in vitreous specimens, especially in cases with minor cellular (P)VRL infiltrates.

Comprehensive circular RNA profiling of proliferative vitreoretinopathy and its clinical significance

Proliferative vitreoretinopathy (PVR) is one of the major challenges in retinal surgery, which occurs in the patient with complex retinal surgery or penetrating eye injury. Circular RNAs (circRNAs) have emerged as important regulators in many biological processes and disease development. However, the characterization and function of circRNAs in PVR remains elusive. In this study, we identified 91 dysregulated circRNAs in the epiretinal membranes (ERMs) of PVR patients. We further investigated the expression pattern of circ_0043144. circ_0043144 was significantly up-regulated in the vitreous samples and the corresponding serum samples of the patients with PVR. circ_0043144 expression was significantly down-regulated after PVR operation. In vitro studies revealed that circ_0043144 was involved in the regulation of the proliferation, migration and secretion ability of ARPE-19 cells, which is critical for ERM formation. Collectively, this study indicates that circRNAs are potential regulators of the pathogenesis of PVR. circ_0043144 is a promising prognostic and diagnostic indicator for PVR diseases.

Determining the effect of low-dose isotretinoin on proliferative vitreoretinopathy: the DELIVER trial

PURPOSE

To examine the effect of low-dose, oral isotretinoin in lowering the risk of proliferative vitreoretinopathy (PVR) following rhegmatogenous retinal detachment (RRD) repair.

METHODS

Prospective, open label, dual-cohort study with pathology-matched historical controls. The prospective experimental arms included two cohorts, composed of 51 eyes with recurrent PVR-related RRD and 58 eyes with primary RRD associated with high-risk features for developing PVR. Eyes in the experimental arms received 20 mg of isotretinoin by mouth once daily for 12 weeks starting the day after surgical repair. The primary outcome measure was single surgery anatomical success rate at 3 months following the study surgery.

RESULTS

The single surgery anatomic success rate was 78.4% versus 70.0% (p=0.358) in eyes with recurrent PVR-related retinal detachment exposed to isotretinoin versus historical controls, respectively. In eyes with RRD at high risk for developing PVR, the single surgery success rate was 84.5% versus 61.1% (p=0.005) for eyes exposed to isotretinoin versus historical controls, respectively. For eyes enrolled in the experimental arms, the most common isotretinoin-related side effects were dry skin/mucus membranes in 106 patients (97.2%), abnormal sleep/dreams in 4 patients (3.7%) and fatigue in 3 patients (2.8%).

CONCLUSION

The management and prevention of PVR is challenging and complex. At the dose and duration given in this study, oral istotretinoin may reduce the risk of PVR-associated recurrent retinal detachment in eyes with primary RRD at high risk of developing PVR.

Dabigatran inhibits intravitreal thrombin activity

PURPOSE

Proliferative vitreoretinopathy (PVR) is a vitreoretinal disorder in which retinal pigment epithelial (RPE) cell activation contributes to both formation of fibrotic retinal membranes and inflammation. Vitreous of patients with PVR contains increased thrombin activity which induces profibrotic and proinflammatory programs in RPE cells. Inhibition of intravitreal thrombin activity may thus represent a therapeutic option for PVR. In this study, we examined the capacity of the clinically available direct thrombin inhibitor dabigatran to inhibit thrombin activity in vitreous fluids.

METHODS

ARPE-19 cells were cultured with the following: (i) thrombin, (ii) vitreous without thrombin activity and (iii) vitreous with elevated thrombin activity (PVR samples and thrombin spiked vitreous) either in the presence or absence of dabigatran (range: 10^-5 to 10^-7  M). Subsequently, CCL2, CXCL8, GMCSF, IL6 and PDGFB mRNA expression levels were determined by RQ-PCR and protein levels of 27 cytokines, chemokines and growth factors were detected in culture supernatants using a multiplex approach. In addition, the capacity of vitreous fluids obtained from patients after oral dabigatran intake was tested in an in vitro thrombin activity assay.

RESULTS

Thrombin and vitreous fluids containing thrombin activity induced CCL2, CXCL8, GM-CSF, IL-6 and PDGF-BB expression by ARPE-19 cells, which was inhibited by dabigatran. In addition, dabigatran that reached the vitreous after repeated oral intake did inhibit thrombin activity in the in vitro activity assay.

CONCLUSION

Proliferative vitreoretinopathy (PVR) is associated with increased intravitreal thrombin activity that activates profibrotic and proinflammatory pathways in RPE cells. Our findings provide evidence that this activation pathway can potentially be inhibited by dabigatran.

Thrombin-Induced Responses via Protease-Activated Receptor 1 Blocked by the Endothelium on Isolated Porcine Retinal Arterioles

PURPOSE

Thrombin, a serine protease, causes organ-specific responses to vessels. However, the mechanism by which thrombin affects the retinal microcirculation remains unclear. We examined the effects of thrombin on the retinal microvasculature and signaling mechanisms.

METHODS

Porcine retinal arterioles were isolated, cannulated, and pressurized (55 cmH₂O) without flow in this in vitro study. Videomicroscopy techniques recorded changes in diameter in the retinal arterioles in response to thrombin at concentrations ranging from 0.001 to 20 mU/ml.

RESULTS

Extraluminal administration of thrombin induced concentration-dependent vascular responses, that is, vasoconstriction at low concentrations less than 5 mU/ml and vasorelaxation with high concentrations greater than 5 mU/ml. However, intraluminal administration of thrombin (5 mU/m) did not constrict the retinal arterioles; in denuded vessels, intraluminal administration constricted the retinal arterioles. Thrombin-induced vasoconstriction was significantly (p < 0.01) suppressed by pretreatment with a protein kinase C (PKC) inhibitor and a protease-activated receptor (PAR)-1 inhibitor but not by PAR-2 and PAR-4 inhibitors or denudation. A rho kinase (ROCK) inhibitor also suppressed thrombin-induced vasoconstriction (5 mU/ml) compared with sodium nitroprusside. Endothelial denudation and pretreatment with an endothelial nitric oxide (NO) synthase inhibitor suppressed vasorelaxation caused by a high concentration of thrombin.

CONCLUSIONS

A low concentration of thrombin causes vasoconstriction of smooth muscles via PAR-1, PKC, and ROCK, and a high concentration of thrombin possibly causes vasorelaxation of the retinal arterioles via nitric oxide synthase activation in the endothelium. The vascular endothelium might block signaling of thrombin-induced vasoconstriction in the retinal arterioles when administered intraluminally.

Thrombin Generation in Vitreous and Subretinal Fluid of Patients with Retinal Detachment

PURPOSE

To measure prothrombin fragments (F1+2) and thrombin-antithrombin complex (TAT) in vitreous and subretinal fluid (SRF) of rhegmatogenous retinal detachment (RRD) patients and to validate and further specify our earlier finding of increased thrombin activity in patients with proliferative vitreoretinopathy (PVR).

METHODS

F1+2 and TAT were measured in 31 vitreous and 16 SRF samples using the Enzygnost® immunoassays.

RESULTS

We found significant levels of F1+2 and TAT in the vitreous of all patients with RRD compared to patients with macular hole or macular pucker. However, there was no significant difference between patients who would develop PVR in the future, had established PVR, and patients with uncomplicated RRD both in vitreous concentrations of F1+2 (Kruskal-Wallis p = 0.963) and TAT (p = 0.516).

CONCLUSION

The analysis of F1+2 and TAT confirmed significant thrombin generation in both vitreous and SRF of patients with RRD. An imbalance between the thrombin regulation mechanisms TAT and α2-macroglobulin possibly explains the difference from our previous findings.

Effects of Interleukin-6 on posterior capsular opacification

The purpose of this work was to determine the effects of interleukin-6 (IL-6) on the development of posterior capsular opacification (PCO) in vitro and in vivo. Western blot and real-time PCR were used to test the IL-6-induced epithelial-mesenchymal transition (EMT) marker α-smooth muscle actin (α-SMA), the extracellular matrix (ECM) markers fibronectin (Fn) and type I collagen (COL-1), transforming growth factor β₂ (TGF-β₂), and the activation and role of the JAK/STAT3 signaling pathway in human lens epithelial cells (HLECs). Immunocytofluorescence staining was performed to detect gp130 and IL-6Rα expression in HLECs. Rat PCO models were then established to examine the impact of STAT3 knockdown by shRNA adeno-associated virus on PCO development, and immunohistochemical staining was performed to detect the expression of Fn in the anterior and posterior capsule in vivo. We found that IL-6 promotes the expression of Fn, COL-1, TGF-β₂, p-JAK2 and p-STAT3 in HLECs but exerts little effect on α-SMA. The JAK/STAT3 inhibitor WP1066 effectively suppressed the IL-6-induced expression of Fn and COL-1 in lens epithelial cells. STAT3 knockdown effectively inhibited the development of PCO in rats and significantly reduced the expression of Fn in the anterior and posterior capsule. These data suggest that IL-6 contributes to the development of PCO by promoting TGF-β₂ activation and ECM synthesis through a JAK/STAT3 signaling-dependent mechanism. Furthermore, inhibiting JAK/STAT3 signaling effectively impairs both PCO development in rats and ECM synthesis in the lens capsule.

Thrombin-Induced Calpain Activation Promotes Protease-Activated Receptor 1 Internalization

The serine protease thrombin activates Protease-Activated Receptors (PARs), a family of G-protein-coupled receptors (GPCRs) activated by the proteolytic cleavage of their extracellular N-terminal domain. Four members of this family have been identified: PAR1–4. The activation of Protease-Activated Receptor 1(PAR1), the prototype of this receptor family, leads to an increase in intracellular Ca⁺² concentration ([Ca⁺²]i) mediated by G_q11α coupling and phospholipase C (PLC) activation. We have previously shown that the stimulation of PAR1 by thrombin promotes intracellular signaling leading to RPE cell transformation, proliferation, and migration which characterize fibroproliferative eye diseases leading to blindness. Within this context, the elucidation of the mechanisms involved in PAR1 inactivation is of utmost importance. Due to the irreversible nature of PAR1 activation, its inactivation must be efficiently regulated in order to terminate signaling. Using ARPE-19 human RPE cell line, we characterized thrombin-induced [Ca⁺²]i increase and demonstrated the calcium-dependent activation of μ-calpain mediated by PAR1. Calpains are a family of calcium-activated cysteine proteases involved in multiple cellular processes including the internalization of membrane proteins through clathrin-coated vesicles. We demonstrated that PAR1-induced calpain activation results in the degradation of α-spectrin by calpain, essential for receptor endocytosis, and the consequent decrease in PAR1 membrane expression. Collectively, the present results identify a novel μ-calpain-dependent mechanism for PAR1 inactivation following exposure to thrombin.

Correlation between Interleukin-6 and Thrombin-Antithrombin III Complex Levels in Retinal Diseases

PURPOSE

This study aims to evaluate and correlate the levels of interleukin-6 (IL-6) and thrombin-antithrombin III complex (TAT) in the vitreous of patients with different vitreoretinal pathologies.

METHODS

Vitreous samples were collected from 78 patients scheduled for pars plana vitrectomy at a tertiary medical center. Patients were divided by the underlying vitreoretinal pathophysiology, as follows: macular hole (MH)/epiretinal membrane (ERM) (n = 26); rhegmatogenous retinal detachment (RRD) (n = 32); and proliferative diabetic retinopathy (PDR) (n = 20). Levels of IL-6 and TAT were measured by enzyme-linked immunosorbent assay and compared among the groups.

RESULTS

A significant difference was found in the vitreal IL-6 and TAT levels between the MH/ERM group and both the PDR and RRD groups (P < 0.001 for all). Diabetes was associated with higher IL-6 levels in the RRD group. Different relationships between the IL-6 and TAT levels were revealed in patients with different ocular pathologies.

CONCLUSION

Our results imply that variations in vitreal TAT level may be attributable not only to an inflammatory reaction or blood-retinal barrier breakdown, but also to intraocular tissue-dependent regulation of thrombin.

All-trans retinoic acid suppresses the adhering ability of ARPE-19 cells via mitogen-activated protein kinase and focal adhesion kinase

This study investigated the signaling mechanism underlying the anti-adhesive effect of all-trans retinoic acid (ATRA) on retinal pigment epithelial ARPE-19 cells. Adhesion kinetics with or without ATRA treatment were profiled by adhesion assay. Surface coating with type IV collagen, fibronectin, laminin, but not type I collagen, significantly enhanced adhesion and spreading of ARPE-19 cells, while ATRA at subtoxic doses (ranging from 10^-7 to 10^-6 M) profoundly suppressed the extracellular matrix-enhanced adhesion ability. Cell attachment on FN activated PI3K/Akt and MAPK cascades, whereas ATRA pretreatment blunted the early phosphorylation of Akt and MAPK signaling mediators including p38 MAPK, JNK1/2, and ERK1/2. Mechanistically, signaling blockade with selective kinase inhibitors demonstrated that all MAPK pathways were involved in the anti-adhesive effect of ATRA, whereas the PI3K inhibitor treatment significantly potentiated the ATRA-suppressed RPE cell adhesion. Moreover, ATRA treatment did not affect intracellular F-actin distribution, but remarkably reduced focal adhesion kinase (FAK) expression and its nuclear localization during ARPE-19 cell attachment. In conclusion, ATRA suppresses the adhering ability of ARPE-19 cells at least in part through MAPK and FAK pathways. Signaling blockade with PI3K inhibitor could be regarded as an alternative modality for treating proliferative vitreoretinopathy.

Vitreous and subretinal fluid concentrations of orally administered dabigatran in patients with rhegmatogenous retinal detachment

PURPOSE

One of the factors that was shown to contribute to the development of proliferative vitreoretinopathy (PVR) is the coagulation factor thrombin. Therefore, a specific oral thrombin inhibitor such as dabigatran might be a possible therapeutic option. An oral drug has the advantage of patient-friendly prolonged administration in contrast to drugs that can only be applied during vitrectomy, on condition that the drug reaches the target site. We tested whether dabigatran reaches the vitreous and subretinal fluid (SRF) after a single oral dose of dabigatran.

METHODS

Twenty-eight patients with a retinal detachment received a single dose of 220 mg dabigatran etexilate 2-8 hr prior to surgery. During surgery, we took a blood sample and a vitreous or subretinal fluid sample. The concentration of dabigatran was measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

The dabigatran concentration between 2 and 9 hr after administration was higher in SRF than in vitreous (max 8.5 and 3.8 ng/ml). Corresponding plasma concentrations ranged from 15 to 225 ng/ml. There was a significant relationship between SRF levels and plasma levels (r_s  = 0.68, p = 0.014); the levels in vitreous fluid showed no such relationship (r_s  = 0.20, p = 0.48). In addition, we measured the vitreous concentration of a non-study patient using 150 mg dabigatran twice daily. The concentration was approximately 10 times higher than after a single dosage (25.8 ng/ml).

CONCLUSION

We demonstrate that oral intake of dabigatran, a candidate drug to modulate PVR, results in potentially relevant intraocular concentrations. We suggest that repeated dosing may lead to higher concentrations, but this should be further explored.

High frequency of latent Chlamydia trachomatis infection in patients with rhegmatogenous retinal detachment

AIM

To determine the frequency of detection of ocular and extraocular Chlamydia trachomatis (CT) infection in non-high myopes with rhegmatogenous retinal detachment (RRD).

METHODS

This was a single-center, nonrandomized, prospective, case-control study. One hundred and four patients were divided into a study group with RRD (n=63) and a control group with traumatic retinal detachment (n=41). Samples of subretinal fluid (SFR), conjunctival, urethral/cervical swabs, and blood were collected. The frequency of detection of CT infection in SRF samples was determined by polymerase chain reaction (PCR), direct fluorescence assay (DFA) and cell culture, whereas that in conjunctival swabs was determined by PCR and DFA, and those in urethral/cervical swabs and blood were determined by DFA. Yates Chi-square test (with Bonferroni correction) and two-tailed Student's t-test were used for statistical analysis.

RESULTS

SRF CT infection was detected more frequently in the study group (50.8%-71.4%) than in the control group (9.8%-12.2%) by all the methods used (P<0.01). The frequency of detection of conjunctival CT infection by DFA was higher in the RRD patients compared with the controls (81.0% vs 24.4%, P=0.004). The PCR detected conjunctival CT infection more often in the study group than in the controls (46.0% vs 9.8%, P=0.007). The DFA detected CT in blood specimens almost as frequently as in urogenital specimens, for the RRD patients (61.2% vs 63.5%) and the controls (7.3% vs 9.8%).

CONCLUSION

CT infection is detected with high frequency in non-high myopes with RRD.

Thrombosis and Hemorrhage in Diabetic Retinopathy: A Perspective from an Inflammatory Standpoint

Retinal ischemia and hemorrhage are hallmarks of worsening diabetic retinopathy, which can lead to neovascularization, macular edema, and severe vision loss. Although diabetes alters expression of clotting factors and their activities, and increases retinal microthromboses, the effects of thrombotic processes on the pathogenesis of diabetic retinopathy are not fully understood. In addition to the roles of coagulation and fibrinolytic cascades in thrombosis and hemostasis, components in these systems also mediate multiple effects on the vasculature that promote inflammation. Plasma kallikrein, thrombin, and urokinase are increased in diabetic retinopathy, and exert proinflammatory effects that contribute to retinal vascular dysfunction. The accumulation and activation of these and additional coagulation factors in the vitreous due to hemorrhage and chronic retinal injury in the diabetic retina may contribute to worsening of retinal inflammation and capillary dysfunction, which lead to retinal ischemia and edema. Further understanding of the role for specific coagulation factors in diabetic retinopathy may suggest new therapeutic opportunities for this vision-threatening disease.

Identification and characterization of proliferative retinopathy-related long noncoding RNAs

Proliferative vitreoretinopathy (PVR) is a serious complication of retinal detachment and vitreoretinal surgery, which can lead to severe vision reduction. Long non-coding RNAs (lncRNAs) play critical roles in many biological processes and disease development. We attempted to determine the role of lncRNAs in the setting of PVR. Microarray analysis revealed that 78 lncRNAs were abnormally expressed in the epiretinal membranes (ERMs) of PVR patients, including 48 up-regulated and 30 down-regulated lncRNA transcripts. We subsequently focus on one lncRNA, MALAT1, and investigated its expression pattern in the biofluid of PVR patients. MALAT1 was significantly up-regulated in the cellular and plasma fraction of peripheral blood in PVR patients. MALAT1 expression was obviously reduced after PVR operation. In vitro experiments revealed the role of MALAT1 in regulating RPE proliferation and migration, which is critical for ERMs formation. This study suggests that lncRNAs are the potential regulators of PVR pathology. MALAT1 is a potential prognostic indicator and a target for the diagnosis and gene therapy for PVR diseases.

Proliferative vitreoretinopathy: A new concept of disease pathogenesis and practical consequences

During the last four decades, proliferative vitreoretinopathy (PVR) has defied the efforts of many researchers to prevent its occurrence or development. Thus, PVR is still the major complication following retinal detachment (RD) surgery and a bottle-neck for advances in cell therapy that require intraocular surgery. In this review we tried to combine basic and clinical knowledge, as an example of translational research, providing new and practical information for clinicians. PVR was defined as the proliferation of cells after RD. This idea was used for classifying PVR and also for designing experimental models used for testing many drugs, none of which were successful in humans. We summarize current information regarding the pathogenic events that follow any RD because this information may be the key for understanding and treating the earliest stages of PVR. A major focus is made on the intraretinal changes derived mainly from retinal glial cell reactivity. These responses can lead to intraretinal PVR, an entity that has not been clearly recognized. Inflammation is one of the major components of PVR, and we describe new genetic biomarkers that have the potential to predict its development. New treatment approaches are analyzed, especially those directed towards neuroprotection, which can also be useful for preventing visual loss after any RD. We also summarize the results of different surgical techniques and clinical information that is oriented toward the identification of high risk patients. Finally, we provide some recommendations for future classification of PVR and for designing comparable protocols for testing new drugs or techniques.