A brief review of the histopathology of proliferative vitreoretinopathy (PVR)

Role of HDAC3 in the epithelial-mesenchymal transition of retinal pigment epithelium cells: Implications for proliferative vitreoretinopathy

Proliferative vitreoretinopathy(PVR) is a type of fibrotic eye disease with a poor clinical prognosis. Increasing evidence has shown that the primary pathological mechanism of PVR is the epithelial-mesenchymal transition(EMT) of retinal pigment epithelium(RPE) cells. Histone deacetylase 3(HDAC3) is a crucial enzyme involved in regulating the acetylation level of proteins. Several studies have reported associations between HDAC3 levels and EMT in various tumors; however, the specific effect of HDAC3 on PVR remains largely unknown. The current study found that HDAC3 was highly expressed in both human PVR membranes and experimental PVR. In vivo, silencing HDAC3 in RPE cells reduced their ability to develop experimental PVR through suppression of EMT. In vitro, inhibition of HDAC3 in RPE cells suppressed EGF-mediated cell proliferation, migration, and EMT. Additionally, overexpression of HDAC3 in RPE cells promoted cell proliferation, migration, and EMT. Mechanistically, the results of chromatin immunoprecipitation(ChIP) and luciferase assays revealed a direct binding of the transcription factor MAZ to the promoter region of HDAC3, thereby promoting its transcription. Furthermore, It was demonstrated that HDAC3 facilitated EMT by interacting with AKT and contributing to its deacetylation. In summary, our findings indicated the involvement of HDAC3 in the EMT of RPE cells, as well as its role in PVR through the regulation of the AKT pathway. These results suggested that targeting HDAC3 could be a potential strategy for preventing and treating PVR.

PHB2 alleviates retinal pigment epithelium cell fibrosis by suppressing the AGE-RAGE pathway

Fibrosis is the primary cause of retinal detachment and visual decline. Here, we investigated the role of Prohibitin 2 (PHB2) in modulating fibrosis in ARPE-19 cells stimulated by transforming growth factor (TGF)-β2. The proliferation, migration, and apoptosis of ARPE-19 cells were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound healing, and flow cytometry assays, and levels of fibrosis-associated and pathway-related proteins were determined by performing western blotting. To examine the mechanisms underlying ARPE-19 cell fibrosis, we performed RNA sequencing, protein-protein interaction network, and enrichment analyses. We detected increases in the expression of the fibrosis-related proteins fibronectin and collagen I in response to TGF-β2 treatment, whereas the expression of PHB2 was downregulated. PHB2 overexpression suppressed the proliferation and migration of TGF-β2-stimulated ARPE-19 cells, promoted apoptosis, and inhibited fibrosis and Smad and non-Smad pathways. PHB2 overexpression inhibited the advanced glycation end-product (AGE)-receptor of advanced glycation end-product (RAGE) pathway activated by TGF-β2 treatment, which contributed to enhancing the effects of PHB2 on cellular processes, fibrosis, and Smad and non-Smad pathways. Conversely, exogenous application of AGE counteracted the effects of PHB2 overexpression. We conclude that by suppressing the AGE-RAGE pathway, PHB2 exerts an inhibitory effect on TGF-β2-induced fibrosis in ARPE-19 cells.

The effect of Coix lachrymal L. seed extract on the expression of inflammation and fibrogenesis genes in human retinal pigment epithelial cells

Proliferative vitreoretinopathy (PVR) is a vision-threatening condition associated with retinal-detachment (RD), primarily caused by fibrocellular scar membrane formation. This study investigates the therapeutic potential of adlay seed extract fractions in mitigating PVR-associated pathways, focusing on oxidative stress, proliferation, inflammation, and fibrogenesis in retinal pigment epithelial (RPE) cells. Adlay seed extract fractions (methanolic: MeOH and residual: Res) were obtained through solvent extraction and characterized for carbohydrate, protein, flavonoid content, and antioxidant activity. RPE cells were cultured, and their viability in response to adlay fractions was assessed using the MTT assay. Gene expression analysis of IL-1β, IL-6, LIF, TGF-β, Snail and α-SMA genes was conducted via real-time PCR after treatment with adlay fractions. The Res fraction exhibited higher levels of protein, carbohydrate, flavonoids, and phenols compared to the MeOH fraction, along with significantly enhanced antioxidant activity. Both fractions showed inhibitory effects on RPE cell viability, with the Res fraction demonstrating a more pronounced impact. Gene expression analysis revealed a significant decrease in IL-6 and TGF-β expression with the MeOH fraction treatment, while the Res fraction led to decreased expression of IL-6, LIF, TGF-β, Snail and α-SMA, indicating a more comprehensive modulation of PVR-associated pathways. This study highlights the potential therapeutic benefits of adlay seed extract fractions in mitigating PVR-associated pathways in RPE cells. The Res fraction, particularly rich in bioactive compounds and exhibiting potent antioxidant activity, shows promise in attenuating oxidative stress, proliferation, inflammation, and fibrogenesis, critical processes in PVR development. These findings underscore the potential of adlay seed extracts as a novel therapeutic strategy for PVR warranting further investigation and clinical validation.

Survey of Dopamine Receptor D2 Antagonists as Retinal Antifibrotics

Purpose: To evaluate the potency and efficacy of a library of dopamine receptor D2 (D2R) antagonists in the mitigation of fibrotic activation in retinal pigment epithelial (RPE) cells. Methods: ARPE-19 cells were cultured and treated with methotrexate or 27 district D2R antagonists using a fibronectin deposition assay. The most potent compounds were then further assessed in assays measuring cellular proliferation, cellular migration, and profibrotic gene expression. Results: The previously established antifibrotic D2R antagonist loxapine exerted a robust and dose-dependent inhibition of fibronectin deposition, whereas methotrexate exerted minimal inhibition. The most potent D2R antagonist identified, fluphenazine, effectively blocked in vitro models of fibrosis at 300-1,000 nM concentrations. Conclusions: Here we found multiple FDA-approved D2R antagonists that potently block RPE cell fibrogenesis. These findings further support the potential of D2R antagonism as a potential therapeutic for retinal fibrotic disease.

Silencing the long noncoding RNA MALAT1 inhibits vitreous-induced epithelial-mesenchymal transition in RPE cells by regulating the PDGFRs/AKT axis

PURPOSE

Epithelial-mesenchymal transition (EMT) is a crucial pathological process that contributes to proliferative vitreoretinopathy (PVR), and research indicates that factors present in the vitreous that target cells play pivotal roles in regulating EMT. Experimental studies have confirmed that rabbit vitreous (RV) promotes EMT in human retinal pigment epithelial (RPE) cells. The long noncoding RNA (lncRNA) MALAT1 has been implicated in EMT in various diseases. Thus, this study aimed to investigate the involvement of lncRNA MALAT1 in vitreous-induced EMT in RPE cells.

METHODS

MALAT1 was knocked down in ARPE-19 cells by short hairpin RNA (shRNA) transfection. Reverse transcription PCR (RT‒PCR) was used to evaluate MALAT1 expression, and Western blotting analysis was used to measure the expression of EMT-related proteins. Wound-healing, Transwell, and cell contraction assays were conducted to assess cell migration, invasion, and contraction, respectively. Additionally, cell proliferation was assessed using the CCK-8 assay, and cytoskeletal changes were examined by immunofluorescence.

RESULTS

MALAT1 expression was significantly increased in ARPE-19 cells cultured with RV. Silencing MALAT1 effectively suppressed EMT and downregulated the associated factors snail1 and E-cadherin. Furthermore, silencing MALAT1 inhibited the RV-induced migration, invasion, proliferation, and contraction of ARPE-19 cells. Silencing MALAT1 also decreased RV-induced AKT and P53 phosphorylation.

CONCLUSIONS

In conclusion, lncRNA MALAT1 participates in regulating vitreous-induced EMT in human RPE cells; these results provide new insight into the pathogenesis of PVR and offer a potential direction for the development of antiproliferative drugs.

Hyalocytes-guardians of the vitreoretinal interface

Originally discovered in the nineteenth century, hyalocytes are the resident macrophage cell population in the vitreous body. Despite this, a comprehensive understanding of their precise function and immunological significance has only recently emerged. In this article, we summarize recent in-depth investigations deciphering the critical role of hyalocytes in various aspects of vitreous physiology, such as the molecular biology and functions of hyalocytes during development, adult homeostasis, and disease. Hyalocytes are involved in fetal vitreous development, hyaloid vasculature regression, surveillance and metabolism of the vitreoretinal interface, synthesis and breakdown of vitreous components, and maintenance of vitreous transparency. While sharing certain resemblances with other myeloid cell populations such as retinal microglia, hyalocytes possess a distinct molecular signature and exhibit a gene expression profile tailored to the specific needs of their host tissue. In addition to inflammatory eye diseases such as uveitis, hyalocytes play important roles in conditions characterized by anomalous posterior vitreous detachment (PVD) and vitreoschisis. These can be hypercellular tractional vitreo-retinopathies, such as macular pucker, proliferative vitreo-retinopathy (PVR), and proliferative diabetic vitreo-retinopathy (PDVR), as well as paucicellular disorders such as vitreo-macular traction syndrome and macular holes. Notably, hyalocytes assume a significant role in the early pathophysiology of these disorders by promoting cell migration and proliferation, as well as subsequent membrane contraction, and vitreoretinal traction. Thus, early intervention targeting hyalocytes could potentially mitigate disease progression and prevent the development of proliferative vitreoretinal disorders altogether, by eliminating the involvement of vitreous and hyalocytes.

Survivin inhibition attenuates EGF-induced epithelial mesenchymal transformation of human RPE cells via the EGFR/MAPK pathway

PURPOSE

The abnormal growth factors-induced epithelial-mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells was known as a vital pathogenesis of proliferative vitreoretinopathy (PVR). This study aims to explore how survivin inhibition affects EMT induced by epidermal growth factor (EGF) in RPE cells.

METHODS

Human primary RPE cells were identified in vitro. EMT in RPE cells was induced by EGF. Inhibition of survivin in RPE cells was accomplished through the use of a survivin inhibitor (YM155) and survivin siRNA. The viability, proliferation and migration of RPE cells was detected by methylthiazol tetrazolium assay, bromodeoxyuridine labeling assay, and wound healing assay, respectively. The EGF receptor /mitogen-activated protein kinase (EGFR/MAPK) proteins and EMT-related proteins were measured by western blot and immunofluorescence assay.

RESULTS

EGF induced significant EMT in RPE cells, activated the phosphorylation of EGFR/MAPK signaling proteins, and caused changes to EMT-related proteins. YM155 suppressed RPE cells' viability, proliferation, and migration; induced the phosphorylation of EGFR, JNK, and P38MAPK; and down regulated EGFR and phosphorylated ERK. YM155 also increased expression of E-cadherin and ZO-1 proteins and reduced expression of N-cadherin, Vimentin, and α-SMA proteins. The EGF-induced increase of RPE cell proliferation and migration was constrained by survivin inhibition. Moreover, survivin inhibition in RPE cells suppressed the EGF-caused phosphorylation of EGFR/MAPK proteins and attenuated the EGF-induced reduction of E-cadherin and ZO-1 proteins and increase of N-cadherin, Vimentin, and α-SMA proteins.

CONCLUSIONS

Survivin inhibition attenuates EGF-induced EMT of RPE cells by affecting the EGFR/MAPK signaling pathway. Survivin might be a promising target for preventing PVR.

Postoperative Proliferation Detection in Eyes Treated for Rhegmatogenous Retinal Detachment by WideField OCT Angiography

Purpose

Proliferative retinal changes may occur postsurgery for rhegmatogenous retinal detachment (RRD), possibly preceding recurrent detachment. This study aims to establish the groundwork for an imaging system capable of discerning changes in retinal vessel tortuosity after RRD repair, analyzing widefield optical coherence tomography angiography (WF-OCTA) images.

Methods

Eighty-eight eyes of 86 patients with RRD who underwent surgical procedures and had repeated imaging with clear widefield optical coherence tomography (WF-OCT) and WF-OCTA on different postoperative days were enrolled in this retrospective study. We compared WF-OCTA images over time to identify alterations in retinal vessel tortuosity and observed regional changes in retinal morphology.

Results

After image processing, changes in retinal vessel tortuosity were detected in 66 quadrants. These changes, attributed to retinal traction from proliferative membranes, were observed in 56 quadrants, among which retinal thickness remained unchanged in seven sectors (12.5%) according to the WF-OCT map. In nine quadrants, changes in retinal vessel tortuosity were attributed to changes in subretinal fluid, aligning with observable variations in retinal thickness.

Conclusions

Observation of vessel tortuosity changes using WF-OCTA can help detect early postoperative proliferative changes in eyes with RRD.

Translational Relevance

Because WF-OCTA can detect minute vessel tortuosity changes, it can offer a noninvasive alternative for the detection of early postoperative proliferative changes.

Tricetin suppresses the cell migration and BMP-6 expression through p38 signaling pathways in human retinal pigment epithelium cells

Proliferative vitreoretinopathy (PVR) is a visual-threatening disease, which cause from the migration of retinal pigment epithelium (RPE). Tricetin, a family of flavonoids, can inhibit the metastasis of several cancers. Herein, we aim to evaluate the possible effect of tricetin on inhibiting ARPE-19 cells migration. The Boyden chamber assay, wound healing assay, RNA sequencing, and Western blot analysis were applied in our experiment. The results revealed that tricetin inhibited the cell migration abilities of ARPE-19 cells. Moreover, using RNA sequencing technology, we revealed that tricetin repressed bone morphogenetic protein-6 (BMP-6) gene expressions in ARPE-19 cells. Overexpression of BMP-6 resulted in significant restoration of cell migration capabilities of tricetin-treated ARPE-19 cells. Furthermore, tricetin suppressed the phosphorylation of the p38 signaling pathway. Moreover, blocking the p38 pathway also inhibits BMP-6 expression and migration in the ARPE-19 cells. In conclusion, this study revealed that tricetin inhibits the ARPE-19 cell migration mainly via the suppression of BMP-6 expression and p38 signaling pathway.

Changes of aqueous humor cytokine profiles of patients with high intraocular pressure after PPV for retinal detachment

High intraocular pressure (IOP) is one of the early complications after pars plana vitrectomy (PPV), which may cause glaucoma and poor visual prognosis secondary to surgery. Proliferative vitreoretinopathy (PVR) is one of the complications of retinal detachment (RD) and is the main reason for the poor prognosis, which is related to different kinds of cytokines. It's essential for the basic mechanism to analyze the relative aqueous humor cytokine profiles with IOP after PPV for RD. In this study, we have collected the aqueous humor of 16 patients and qualified 27 cytokines using Luminex and compared biomarkers with the high IOP group and the normal group. As a result, the concentrations of VEGF, IL-6, FGF2, and G-CSF upregulated significantly (P < 0.05), while VEGFR2 downregulated significantly (P < 0.05) in the high IOP group. IL-6 was positively correlated with high IOP (r = 0.561, P = 0.041). Meanwhile, the concentrations of IL-6 (r = 0.543, P = 0.03), IL-5 (r = 0.576, P = 0.019), IL-15 (r = 0.614, P = 0.011), IL-4 (r = 0.517, P = 0.04), ICAM-1 (r = 0.611, P = 0.012), and G-CSF (r = 0.636, P = 0.008) were significantly associated with preoperative PVR classification, and the aqueous humor levels of IL-4 (r = 0.567, P = 0.022), HGF (r = 0.701, P = 0.005), and MCP-1 (r = 0.565, P = 0.035) are significant relative to laser points. Hence, cytokines might potentially be the therapeutic target of high IOP after PPV.

Epithelial-mesenchymal Transition (EMT) and the Effect of Atorvastatin on it in ARPE-19 cells

Proliferative vitreoretinopathy (PVR) develops after an unsuccessful or complicated recovery from rhegmatogenous retinal detachment (RRD) surgery. Intraocular scar formation with the contribution of epithelial-mesenchymal transition (EMT) in RPE cells is prominent in the pathology of PVR. In the present study, the EMT process was experimentally induced in human retinal pigment epithelium (RPE; ARPE-19) cells, and the effect of atorvastatin on the process was studied. The mRNA and protein levels of mesenchymal markers actin alpha 2 (ACTA2) / alpha-smooth muscle actin (α-SMA) and fibronectin (FN), and epithelial markers occludin (OCLN) and zonula occludens-1 (ZO-1) were measured using quantitative real-time PCR (qRT-PCR) and western blot methods, respectively. In addition, α-SMA and FN were visualized using immunofluorescence staining. Cells were photographed under a phase contrast light microscope. Changes in the functionality of cells following the EMT process were studied using the IncuCyte scratch wound cell migration assay and the collagen cell invasion assay with confocal microscopy. The induction of EMT in ARPE-19 cells increased the expression of mesenchymal markers ACTA2/α-SMA and fibronectin and reduced the expression of epithelial marker OCLN both at mRNA and protein levels. The mRNA levels of ZO-1 were lower after EMT, as well. Increased levels of α-SMA and FN were confirmed by immunofluorescence staining. Atorvastatin further increased the mRNA levels of mesenchymal markers ACTA2 and FN as well as the protein levels of α-SMA and reduced the mRNA levels of epithelial markers OCLN and ZO-1 under the EMT process. EMT promoted wound closure and cell invasion into the 3D collagen matrix when compared to untreated control cells. These data present cellular changes upon the induction of the EMT process in ARPE-19 cells and the propensity of atorvastatin to complement the effect. More studies are needed to confirm the exact influence of the EMT process and atorvastatin treatment on the PVR development after RRD surgery.

Bone morphogenetic protein-6 suppresses TGF-β2-induced epithelial-mesenchymal transition in retinal pigment epithelium

AIM

To evaluate the effect of bone morphogenetic protein-6 (BMP-6) on transforming growth factor (TGF)-β2-induced epithelial-mesenchymal transition (EMT) in retinal pigment epithelium (RPE).

METHODS

Adult retinal pigment epithelial cell line (ARPE-19) were randomly divided into control, TGF-β2 (5 µg/L), and BMP-6 small interfering RNA (siRNA) group. The cell morphology was observed by microscopy, and the cell migration ability were detected by Transwell chamber. The EMT-related indexes and BMP-6 protein levels were detected by Western blotting. Furthermore, a BMP-6 overexpression plasmid was constructed and RPE cells were divided into the control group, TGF-β2+empty plasmid group, BMP-6 overexpression group, and TGF-β2+BMP-6 overexpression group. The EMT-related indexes and extracellular regulated protein kinases (ERK) protein levels were detected.

RESULTS

Compared with the control group, the migration of RPE cells in the TGF-β2 group was significantly enhanced. TGF-β2 increased the protein expression levels of α-smooth muscle actin (α-SMA), fibronectin and vimentin but significantly decreased the protein levels of E-cadherin and BMP-6 (P<0.05) in RPE. Similarly, the migration of RPE cells in the BMP-6 siRNA group was also significantly enhanced. BMP-6 siRNA increased the protein expression levels of α-SMA, fibronectin and vimentin but significantly decreased the protein expression levels of E-cadherin (P<0.05). Overexpression of BMP-6 inhibited the migration of RPE cells induced by TGF-β2 and prevented TGF-β2 from affecting EMT-related biomarkers (P<0.05).

CONCLUSION

BMP-6 prevents the EMT in RPE cells induced by TGF-β2, which may provide a theoretical basis for the prevention and treatment of proliferative vitreoretinopathy.

Microfluidic Fabricated Liposomes for Nutlin-3a Ocular Delivery as Potential Candidate for Proliferative Vitreoretinal Diseases Treatment

Purpose

Proliferative vitreoretinal diseases (PVDs) represent a heterogeneous group of pathologies characterized by the presence of retinal proliferative membranes, in whose development retinal pigment epithelium (RPE) is deeply involved. As the only effective treatment for PVDs at present is surgery, we aimed to investigate the potential therapeutic activity of Nutlin-3a, a small non-genotoxic inhibitor of the MDM2/p53 interaction, on ARPE-19 cell line and on human RPE primary cells, as in vitro models of RPE and, more importantly, to formulate and evaluate Nutlin-3a loaded liposomes designed for ophthalmic administration.

Methods

Liposomes were produced using an innovative approach by a microfluidic device under selection of different conditions. Liposome size distribution was evaluated by photon correlation spectroscopy and centrifugal field flow fractionation, while the liposome structure was studied by transmission electron microscopy and Fourier-transform infrared spectroscopy. The Nutlin-3a entrapment capacity was evaluated by ultrafiltration and HPLC. Nutlin-3a biological effectiveness as a solution or loaded in liposomes was evaluated by viability, proliferation, apoptosis and migration assays and by morphological analysis.

Results

The microfluidic formulative study enabled the selection of liposomes composed of phosphatidylcholine (PC) 5.4 or 8.2 mg/mL and 10% ethanol, characterized by roundish vesicular structures with 150-250 nm mean diameters. Particularly, liposomes based on the lower PC concentration were characterized by higher stability. Nutlin-3a was effectively encapsulated in liposomes and was able to induce a significant reduction of viability and migration in RPE cell models.

Conclusion

Our results lay the basis for a possible use of liposomes for the ocular delivery of Nutlin-3a.

Bone morphogenetic protein 6 (BMP6) antagonises experimental proliferative vitreoretinopathy established by TGF-β2 stimulation in retinal pigment epithelial cells through modulation of the p38 and JNK MAPK pathways

The formation of the epiretinal fibrotic membrane by retinal pigment epithelial (RPE) cells is a primary pathological change for proliferative vitreoretinopathy (PVR). Bone morphogenetic protein 6 (BMP6) is an antifibrogenic factor in various cells. To date, it is still unknown whether BMP6 can interfere with the fibrogenesis of RPE cells during the progression of PVR. This work aimed to address the relationship between BMP6 and transforming growth factor-β2 (TGF-β2)-elicited fibrogenesis of RPE cells, an experimental model for studying PVR in vitro. The BMP6 level was down-regulated, while the TGF-β2 level was up-regulated in the vitreous humor of PVR patients. The BMP6 level was down-regulated in human RPE cells challenged with TGF-β2. The treatment of RPE cells with TGF-β2 resulted in significant increases in proliferation, migration, epithelial-to-mesenchymal transition (EMT), and extracellular matrix (ECM) remodelling. These effects were found to be inhibited by the overexpression of BMP6 or exacerbated by the knockdown of BMP6. BMP6 overexpression reduced the phosphorylation of p38 and JNK in TGF-β2-stimulated RPE cells, while BMP6 knockdown showed the opposite effects. The inhibition of p38 or JNK partially reversed the BMP6-silencing-induced promoting effects on TGF-β2-elicited fibrogenesis in RPE cells. Taken together, BMP6 demonstrates the ability to counteract the proliferation, migration, EMT, and ECM remodelling of RPE cells induced by TGF-β2. This is achieved through the regulation of the p38 and JNK MAPK pathways. These findings imply a potential connection between BMP6 and PVR, and highlight the potential application of BMP6 in therapeutic interventions for PVR.

Transition to Chronic Fibrosis in an Animal Model of Retinal Detachment With Features of Proliferative Vitreoretinopathy

Purpose

Proliferative vitreoretinopathy (PVR) is the most common cause of failure of surgically repaired rhegmatogenous retinal detachment (RRD). Chemically induced and cell injection PVR models do not fully simulate the clinical characteristics of PVR in the post-RRD context. There is an unmet need for translational models in which to study mechanisms and treatments specific to RRD-PVR.

Methods

RRD was induced in adult Dutch Belted rabbits. Posterior segments were fixed or processed for RNA sequencing at 6 hours and 2, 7, 14, and 35 days after induction. Histochemical staining and immunolabeling for glial fibrillary acidic protein, alpha smooth muscle actin, vascular endothelial growth factor receptor 2, CD68, and RPE 65 kDa protein were performed, and labeling intensity was scored. Single cell RNA sequencing was performed.

Results

Acute histopathological changes included intravitreal and intraretinal hemorrhage, leukocytic vitritis, chorioretinitis, and retinal rarefaction. Chronic lesions showed retinal atrophy, gliosis, fibrotic subretinal membranes, and epiretinal fibrovascular proliferation. Fibrillar collagen was present in the fibrocellular and fibrovascular membranes in chronic lesions. Moderate to strong labeling of glia and vasculature was detected in chronic lesions. At day 14, most cells profiled by single cell sequencing were identified as Mϋller glia and microglia, consistent with immunolabeling. Expression of several fibrillar collagen genes was upregulated in chronic lesions.

Conclusions

Histological and transcriptional features of this rabbit model simulate important features of human RRD-PVR, including the transition to chronic intraretinal and periretinal fibrosis. This animal model of RRD with features of PVR will enable further research on targeted treatment interventions.

Predictive values of systemic inflammation biomarkers in proliferative vitreoretinopathy associated with primary rhegmatogenous retinal detachment

CLINICAL RELEVANCE

Proliferative vitreoretinopathy (PVR) is still the leading cause of surgical failure after rhegmatogenous retinal detachment (RRD) repair. The factors that can predict the development of PVR remain to be elucidated.

BACKGROUND

This study evaluates the predictive values of the systemic immune-inflammation index, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio in patients with primary RRD with and without PVR.

METHODS

A total of 150 patients with RRD and 51 age- and sex-matched healthy participants were included in the study. Patients who developed PVR within three months after surgery were enrolled as PVR cases (n = 75, Group 1), and those who did not develop PVR were enrolled in RRD without the PVR group (n = 75, Group 2). Ocular examination findings and medical records of all participants were analysed retrospectively. Peripheral blood samples were collected, and systemic immune-inflammation index, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratios were calculated. The systemic immune-inflammation index calculation formula is: (Neutrophil/lymphocyte) × Platelet.

RESULTS

The median neutrophil-to-lymphocyte ratio and systemic immune-inflammation index levels were significantly higher in Group 1 patients compared to Group 2 and the control groups (p = 0.01, for both). However, the groups were similar regarding median platelet-to-lymphocyte ratio (p = 0.917). The optimal cut-off values of neutrophil-to-lymphocyte ratio and systemic immune-inflammation index were calculated as 1.72 (with 72% sensitivity and 48% specificity) and 407.9 (with 72% sensitivity and 49.3% specificity), respectively, for predicting PVR development in patients with RRD.

CONCLUSION

Neutrophil-to-lymphocyte ratio and systemic immune-inflammation index may be useful biomarkers for predicting the risk of PVR development in RRD patients.

A de novo missense mutation in MPP2 confers an increased risk of Vogt-Koyanagi-Harada disease as shown by trio-based whole-exome sequencing

Vogt-Koyanagi-Harada (VKH) disease is a leading cause of blindness in young and middle-aged people. However, the etiology of VKH disease remains unclear. Here, we performed the first trio-based whole-exome sequencing study, which enrolled 25 VKH patients and 50 controls, followed by a study of 2081 VKH patients from a Han Chinese population to uncover detrimental mutations. A total of 15 de novo mutations in VKH patients were identified, with one of the most important being the membrane palmitoylated protein 2 (MPP2) p.K315N (MPP2-N315) mutation. The MPP2-N315 mutation was highly deleterious according to bioinformatic predictions. Additionally, this mutation appears rare, being absent from the 1000 Genome Project and Genome Aggregation Database, and it is highly conserved in 10 species, including humans and mice. Subsequent studies showed that pathological phenotypes and retinal vascular leakage were aggravated in MPP2-N315 mutation knock-in or MPP2-N315 adeno-associated virus-treated mice with experimental autoimmune uveitis (EAU). In vitro, we used clustered regularly interspaced short palindromic repeats (CRISPR‒Cas9) gene editing technology to delete intrinsic MPP2 before overexpressing wild-type MPP2 or MPP2-N315. Levels of cytokines, such as IL-1β, IL-17E, and vascular endothelial growth factor A, were increased, and barrier function was destroyed in the MPP2-N315 mutant ARPE19 cells. Mechanistically, the MPP2-N315 mutation had a stronger ability to directly bind to ANXA2 than MPP2-K315, as shown by LC‒MS/MS and Co-IP, and resulted in activation of the ERK3/IL-17E pathway. Overall, our results demonstrated that the MPP2-K315N mutation may increase susceptibility to VKH disease.

In vitro laboratory models of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR), the most common cause of recurrent retinal detachment, is characterized by the formation and contraction of fibrotic membranes on the surface of the retina. There are no Food and Drug Administration (FDA)-approved drugs to prevent or treat PVR. Therefore, it is necessary to develop accurate in vitro models of the disease that will enable researchers to screen drug candidates and prioritize the most promising candidates for clinical studies. We provide a summary of recent in vitro PVR models, as well as avenues for model improvement. Several in vitro PVR models were identified, including various types of cell cultures. Additionally, novel techniques that have not been used to model PVR were identified, including organoids, hydrogels, and organ-on-a-chip models. Novel ideas for improving in vitro PVR models are highlighted. Researchers may consult this review to help design in vitro models of PVR, which will aid in the development of therapies to treat the disease.

Mechanism underlying Müller cell pyroptosis and its role in the development of proliferative vitreoretinopathy

OBJECTIVES

To explore the mechanism underlying Müller Cell Pyroptosis (MCP) and its role in the development of Proliferative Vitreoretinopathy (PVR).

METHOD

The expression of pyroptosis-related factors, namely, cysteinyl aspartate-specific proteinase (caspase-1), interleukin (IL)-1β, IL-18, and Gasdermin D (GSDMD), was detected by quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) and western blotting at the mRNA and protein levels, respectively, in retinal tissues. Müller and spontaneously Arising Retinal Pigment Epithelia (ARPE)-19 primary cells with GSDMD overexpression or knockdown were cultivated. Western blotting was used to detect the levels of the following pyroptosis-related factors in retinal tissues: caspase-1, IL-1β, IL-18, and GSDMD. Through Cell Adhesion (CA) experiments, the changes in ARPE-19 CA in each group were observed. The migration and invasion of ARPE-19 cells were measured using the Transwell assay. The proliferation of ARPE-19 cells was measured with a Cell Counting Kit 8 (CCK-8) assay. Finally, the expression of the cytokines IL-1β and IL-18 in the ARPE-19 cell culture medium was detected using the Enzyme-Linked Immunosorbent Assay (ELISA).

RESULTS

Compared with the surrounding normal tissues, the expression of caspase-1, IL-1β, IL-18, and GSDMD at the protein and mRNA levels in the retinal proliferative membrane samples of the patients decreased significantly (p < 0.05). MCP significantly enhanced ARPE-19 CA, migration and invasion, proliferation, and cytokine expression (p < 0.05).

CONCLUSIONS

MCP can promote the development of PVR lesions.

Human Wharton's Jelly Mesenchymal Stem Cell Secretome Modifies the Processes of Neuroprotection and Epithelial-Mesenchymal Transition in Retinal Pigment Epithelium at Transcriptional Level

BACKGROUND

Retinal pigment epithelium (RPE) cells are potential targets for treating retinal detachment (RD) and proliferative vitreoretinopathy (PVR), considering the importance of neuroprotection and epithelial-mesenchymal transition (EMT) of RPE in these conditions. This study investigated the effect of human Wharton's jelly mesenchymal stem cell secretome (WJMSC-S) on the expression of genes involved in both neuroprotection and EMT in RPE cells in vitro (TRKB, MAPK, PI3K, BDNF, and NGF).

METHODS

RPE cells from passages 5-7 were treated with WJMSC-S (or the vehicle culture medium as control) for 24 h at 37◦C and subsequently subjected to RNA extraction and cDNA synthesis. Gene expression level was evaluated using real-time PCR in the treated versus control cells.

RESULTS

The results of our study showed that WJMSC-S led to a significant downregulation in three out of five studied gene expression (MAPK, TRKB, and NGF), and simultaneously, remarkably upregulated the expression of the BDNF gene.

CONCLUSIONS

According to the present data, WJMSC-S can affect the EMT and neuroprotection processes at the mRNA level by suppressing EMT and promoting neuroprotection in RPE cells. This finding may have positive clinical implications in the context of RD and PVR.

Effect of N-oleoyl dopamine on myofibroblast trans-differentiation of retinal pigment epithelial cells

Retinal pigment epithelial (RPE) cells contribute to several clinical conditions resulting in retinal fibrotic scars. Myofibroblast trans-differentiation of RPE cells is a critical step in the process of retinal fibrosis. In this study, we investigated the effects of N-oleoyl dopamine (OLDA), a newer endocannabinoid with a structure distinct from classic endocannabinoids, on TGF-β2-induced myofibroblast trans-differentiation of porcine RPE cells. Using an in vitro collagen matrix contraction assay, OLDA was found to inhibit TGF-β2 induced contraction of collagen matrices by porcine RPE cells. This effect was concentration-dependent, with significant inhibition of contraction observed at 3 μM and 10 μM. OLDA did not affect the proliferation of porcine RPE cells. Immunocytochemistry showed that at 3 μM, OLDA decreased incorporation of α-SMA in the stress fibers of TGF-β2-treated RPE cells. In addition, western blot analysis showed that 3 μM OLDA significantly downregulated TGF-β2-induced α-SMA protein expression. Taken together these results demonstrate that OLDA inhibits TGF-β induced myofibroblast trans-differentiation of RPE cells. It has been established that classic endocannabinoid such as anandamide, by activating the CB1 cannabinoid receptor, promote fibrosis in multiple organ systems. In contrast, this study demonstrates that OLDA, an endocannabinoid with a chemical structure distinct from classic endocannabinoids, inhibits myofibroblast trans-differentiation, an important step in fibrosis. Unlike classic endocannabinoids, OLDA has weak affinity for the CB1 receptor. Instead, OLDA acts on non-classic cannabinoid receptors such as GPR119, GPR6, and TRPV1. Therefore, our study indicates that the newer endocannabinoid OLDA and its non-classic cannabinoid receptors could potentially be novel therapeutic targets for treating ocular diseases involving retinal fibrosis and fibrotic pathologies in other organ systems.

Inflammation and Oxidative Stress Gene Variability in Retinal Detachment Patients with and without Proliferative Vitreoretinopathy

This study investigated the association between certain genetic variations and the risk of developing proliferative vitreoretinopathy (PVR) after surgery. The study was conducted on 192 patients with primary rhegmatogenous retinal detachment (RRD) who underwent 3-port pars plana vitrectomy (PPV). The distribution of single nucleotide polymorphisms (SNPs) located in genes involved in inflammation and oxidative stress associated with PVR pathways were analyzed among patients with and without postoperative PVR grade C1 or higher. A total of 7 defined SNPs of 5 genes were selected for genotyping: rs4880 (SOD2); rs1001179 (CAT); rs1050450 (GPX1); rs1143623, rs16944, rs1071676 (IL1B); rs2910164 (MIR146A) using competitive allele-specific polymerase chain reaction. The association of SNPs with PVR risk was evaluated using logistic regression. Furthermore, the possible association of SNPs with postoperative clinical parameters was evaluated using non-parametric tests. The difference between two genotype frequencies between patients with or without PVR grade C1 or higher was found to be statistically significant: SOD2 rs4880 and IL1B rs1071676. Carriers of at least one polymorphic IL1B rs1071676 GG allele appeared to have better postoperative best-corrected visual acuity only in patients without PVR (p = 0.070). Our study suggests that certain genetic variations may play a role in the development of PVR after surgery. These findings may have important implications for identifying patients at higher risk for PVR and developing new treatments.

Aerosolized, Gas-Phase, Intravitreal Methotrexate Reduces Proliferative Vitreoretinopathy in a Randomized Trial in a Porcine Model

Purpose

To determine the effectiveness of aerosol-delivered methotrexate (AD-MTx) in a large-animal (porcine) model of proliferative vitreoretinopathy (PVR).

Design

Prospective, randomized, interventional, double-masked, controlled, large-animal study with predetermined clinical and histopathologic outcome criteria.

Controls

Half of the pigs were randomly assigned to receive an identical volume of aerosol-delivered normal saline (AD-NS) using identical delivery systems and treatment intervals.

Methods

Proliferative vitreoretinopathy was surgically induced in 16 pigs (8 males and 8 females), randomly assigned to receive 2 doses (group A) or 3 doses (group B) of either AD-MTx (1.6 mg/0.4 ml) or normal saline (AD-NS). Group A pigs were euthanized at week 2 (n = 8), and group B pigs were euthanized at week 3 (n = 8). Masked clinical PVR scores (0-6) by a vitreoretinal surgeon and histopathology PVR scores (0-8) by a masked ophthalmic pathologist were used to determine outcomes.

Main Outcome Measures

The mean, combined clinical and histopathology scores (both anterior and posterior) were used to determine the overall treatment effect between the groups.

Results

The mean masked score (± standard deviation) when all grading end points (clinical + histopathology) were combined was a mean of 8.0 ± 2.3 in the AD-MTx group versus a higher 9.9 ± 2.0 in the AD-NS control group (P = 0.05). The clinical score was 3.88 ± 1.2 in the AD-MTx group versus 4.63 ± 1.6 in the AD-NS group (P = 0.16). The histopathology score for anterior PVR was 2.5 ± 0.8 in the AD-MTx group versus 2.5 ± 0.5 in the AD-NS group (P = 0.50), and the posterior PVR was 1.63 ± 1.6 in the AD-MTx group versus 2.75 ± 1.3 in the AD-NS group (P = 0.07). When the frequency of methotrexate dosing in group A (2 doses) was compared with that in group B (3 doses), the mean score was 8.75 versus 9.13 (P = 0.38), respectively, suggesting an insignificant difference.

Conclusions

After surgical induction of PVR in an aggressive, high-risk, large-animal model, AD-MTx reduced posterior PVR formation compared with AD-NS. Additional dosing at week 3 did not improve the outcomes. No difference in anterior PVR formation was noted with intervention. This novel drug delivery system has implications for PVR reduction and warrants further investigation.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

The essential role of N6-methyladenosine RNA methylation in complex eye diseases

There are many complex eye diseases which are the leading causes of blindness, however, the pathogenesis of the complex eye diseases is not fully understood, especially the underlying molecular mechanisms of N6-methyladenosine (m6A) RNA methylation in the eye diseases have not been extensive clarified. Our review summarizes the latest advances in the studies of m6A modification in the pathogenesis of the complex eye diseases, including cornea disease, cataract, diabetic retinopathy, age-related macular degeneration, proliferative vitreoretinopathy, Graves' disease, uveal melanoma, retinoblastoma, and traumatic optic neuropathy. We further discuss the possibility of developing m6A modification signatures as biomarkers for the diagnosis of the eye diseases, as well as potential therapeutic approaches.

Increased intravitreal glucose in rhegmatogenous retinal detachment

PURPOSE

Altered glucose metabolism, along with low-grade inflammation, has been proposed to be involved in retinal detachment (RD)-induced cone loss. Here, we assessed intravitreal glucose and cytological profile in patients with macula-off RD.

METHODS

Glucose concentration was analysed in vitreous samples from 137 non-diabetic patients undergoing vitrectomy for either primary macula-off RD (n = 73) or epiretinal membrane (ERM; n = 64). Cellularity was assessed in vitreous cytospin preparations by a semi-quantitative immunostaining approach.

RESULTS

Intravitreal glucose concentration was higher in the RD group (2.28 mmol.L-1 n =73 vs 1.6 mmol.L-1 n = 64; p < 0.0001). Overall cellularity and density of macrophages were significantly higher in the vitreous of RD patients (respectively p = 0.003 and p < 0.0001). Among the RD patients, intravitreal glucose concentration correlated with macrophages density (p = 0.002): its levels remained significantly higher in eyes in which macrophages were innumerable compared to lower macrophages densities RD eyes (p = 0.0095).

CONCLUSIONS

We observed a strong relationship between intravitreal glucose concentration and vitreous macrophage density. Additional indicators for vitreous glycation and low-grade inflammation should be further studied.

DAPL1 prevents epithelial-mesenchymal transition in the retinal pigment epithelium and experimental proliferative vitreoretinopathy

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is a hallmark of the pathogenesis of proliferative vitreoretinopathy (PVR) that can lead to severe vision loss. Nevertheless, the precise regulatory mechanisms underlying the pathogenesis of PVR remain largely unknown. Here, we show that the expression of death-associated protein-like 1 (DAPL1) is downregulated in PVR membranes and that DAPL1 deficiency promotes EMT in RPE cells in mice. In fact, adeno-associated virus (AAV)-mediated DAPL1 overexpression in RPE cells of Dapl1-deficient mice inhibited EMT in physiological and retinal-detachment states. In a rabbit model of PVR, ARPE-19 cells overexpressing DAPL1 showed reduced ability to induce experimental PVR, and AAV-mediated DAPL1 delivery attenuated the severity of experimental PVR. Furthermore, a mechanistic study revealed that DAPL1 promotes P21 phosphorylation and its stabilization partially through NFκB (RelA) in RPE cells, whereas the knockdown of P21 led to neutralizing effects on DAPL1-dependent EMT inhibition and enhanced the severity of experimental PVR. These results suggest that DAPL1 acts as a novel suppressor of RPE-EMT and has an important role in antagonizing the pathogenesis of experimental PVR. Hence, this finding has implications for understanding the mechanism of and potential therapeutic applications for PVR.

p21CIP/WAF1 saRNA inhibits proliferative vitreoretinopathy in a rabbit model

PURPOSE

Proliferative vitreoretinopathy (PVR) is a disease process resulting from proliferation of retinal pigment epithelial (RPE) cells in the vitreous and periretinal area, leading to periretinal membrane formation and traction and eventually to postoperative failure after vitreo-retinal surgery for primary rhegmatogenous retinal detachment (RRD). The present study was designed to test the therapeutic potential of a p21CIP/WAF1 (p21) inducing saRNA for PVR.

METHODS

A chemically modified p21 saRNA (RAG1-40-53) was tested in cultured human RPE cells for p21 induction and for the inhibition of cell proliferation, migration and cell cycle progression. RAG1-40-53 was further conjugated to a cholesterol moiety and tested for pharmacokinetics and pharmacodynamics in rabbit eyes and for therapeutic effects after intravitreal administration in a rabbit PVR model established by injecting human RPE cells.

RESULTS

RAG1-40-53 (0.3 mg, 1 mg) significantly induced p21 expression in RPE cells and inhibited cell proliferation, the progression of cell cycle at the G0/G1 phase and TGF-β1 induced migration. After a single intravitreal injection into rabbit eyes, cholesterol-conjugated RAG1-40-53 exhibited sustained concentration in the vitreal humor beyond at least 8 days and prevented the progression of established PVR.

CONCLUSION

p21 saRNA could represent a novel therapeutics for PVR by exerting a antiproliferation and antimigration effect on RPE cells.

Assessment of histological and immunohistochemical features of retinal tissues using a novel tissue submission procedure

We introduce a novel tissue submission procedure without additional equipment or storage facilities for assessing the histological and immunohistochemical features of retinal tissues. In total, 150 specimens were collected from patients who underwent vitrectomy or macular surgery from January to December 2020. Ninety-eight specimens were submitted using the new procedure, and 58 specimens were submitted as flat-mount slides to compare specimen adequacy. The tissues submitted using the new procedure were subjected to paraffin-embedding and sectioning for hematoxylin & eosin staining. Additional immunohistochemical analysis was performed to assess the cellular composition in retinal tissues with diverse etiologies. The new submission procedure had an adequacy ratio of 75.51%, which was comparable to that of the flat-mount method (p = 0.1397). The new method could produce high-quality images of histological features of tissues and facilitated immunohistochemical analysis to demonstrate cell origins. More glial cells (p = 0.000) and myofibroblasts (p = 0.012) were detected in the epiretinal membranes (ERMs) than in the internal limiting membranes (ILMs). Subgroup analysis revealed that secondary ERMs contained more macrophage-like cells (p = 0.001) and retinal pigment epithelial cells (p = 0.000) than did idiopathic ERMs. Our novel tissue submission procedure can be applied to routine clinical practice. Our study provides additional histological and immunohistochemical evidence of cellular components in retinal tissues based on a large number of human tissue samples. Moreover, tissues submitted using the new method can be permanently preserved, enabling future investigation for potential prognostic or therapeutic targets.

Role of Oxidative Stress in Ocular Diseases: A Balancing Act

Redox homeostasis is a delicate balancing act of maintaining appropriate levels of antioxidant defense mechanisms and reactive oxidizing oxygen and nitrogen species. Any disruption of this balance leads to oxidative stress, which is a key pathogenic factor in several ocular diseases. In this review, we present the current evidence for oxidative stress and mitochondrial dysfunction in conditions affecting both the anterior segment (e.g., dry eye disease, keratoconus, cataract) and posterior segment (age-related macular degeneration, proliferative vitreoretinopathy, diabetic retinopathy, glaucoma) of the human eye. We posit that further development of therapeutic interventions to promote pro-regenerative responses and maintenance of the redox balance may delay or prevent the progression of these major ocular pathologies. Continued efforts in this field will not only yield a better understanding of the molecular mechanisms underlying the pathogenesis of ocular diseases but also enable the identification of novel druggable redox targets and antioxidant therapies.

Intravitreal slow-release dexamethasone alleviates traumatic proliferative vitreoretinopathy by inhibiting persistent inflammation and Müller cell gliosis in rabbits

AIM

To evaluate the effects of intravitreal slow-release dexamethasone on traumatic proliferative vitreoretinopathy (PVR) and Müller cell gliosis and preliminarily explored the possible inflammatory mechanism in a rabbit model induced by penetrating ocular trauma.

METHODS

Traumatic PVR was induced in the right eyes of pigmented rabbits by performing an 8-mm circumferential scleral incision placed 2.5 mm behind the limbus, followed by treatment with a slow-release dexamethasone implant (Ozurdex) or sham injection. Left eyes were used as normal controls. The intraocular pressure (IOP) was monitored using an iCare tonometer. PVR severity was evaluated via anatomical and histopathological examinations every week for 6wk; specific inflammatory cytokine and proliferative marker levels were measured by quantitative real-time polymerase chain reaction, Western blot, protein chip analysis, or immunofluorescence staining.

RESULTS

During the observation period, PVR severity gradually increased. Intense Müller cell gliosis was observed in the peripheral retina near the wound and in the whole retina of PVR group. Ozurdex significantly alleviated PVR development and Müller cell gliosis. Post-traumatic inflammation fluctuated and was persistent. The interleukin-1β (IL-1β) mRNA level was significantly upregulated, peaking on day 3 and increasing again on day 21 after injury. The expression of nod-like receptor family pyrin domain containing 3 (NLRP3) showed a similar trend that began earlier than that of IL-1β expression. Ozurdex suppressed the expression of IL-1β, NLRP3, and phosphorylated nuclear factor-kappa B (NF-κB). The average IOP after treatment was within normal limits.

CONCLUSION

The present study demonstrates chronic and fluctuating inflammation in a traumatic PVR rabbit model over 6wk. Ozurdex treatment significantly inhibites inflammatory cytokines expression and Müller cell gliosis, and thus alleviates PVR severity. This study highlights the important role of IL-1β, and Ozurdex inhibites inflammation presumably via the NF-κB/NLRP3/IL-1β inflammatory axis. In summary, Ozurdex provides a potential therapeutic option for traumatic PVR.

NFκB-Mediated Expression of Phosphoinositide 3-Kinase δ Is Critical for Mesenchymal Transition in Retinal Pigment Epithelial Cells

Epithelial mesenchymal transition (EMT) plays a vital role in a variety of human diseases including proliferative vitreoretinopathy (PVR), in which retinal pigment epithelial (RPE) cells play a key part. Transcriptomic analysis showed that the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway was up-regulated in human RPE cells upon treatment with transforming growth factor (TGF)-β2, a multifunctional cytokine associated with clinical PVR. Stimulation of human RPE cells with TGF-β2 induced expression of p110δ (the catalytic subunit of PI3Kδ) and activation of NFκB/p65. CRISPR-Cas9-mediated depletion of p110δ or NFκB/p65 suppressed TGF-β2-induced fibronectin expression and activation of Akt as well as migration of these cells. Intriguingly, abrogating expression of NFκB/p65 also blocked TGF-β2-induced expression of p110δ, and luciferase reporter assay indicated that TGF-β2 induced NFκB/p65 binding to the promoter of the PIK3CD that encodes p110δ. These data reveal that NFκB/p65-mediated expression of PI3Kδ is essential in human RPE cells for TGF-β2-induced EMT, uncovering hindrance of TGF-β2-induced expression of p110δ as a novel approach to inhibit PVR.

Upregulation of Neuroinflammatory Protein Biomarkers in Acute Rhegmatogenous Retinal Detachments

The purpose of this study is to characterize the inflammatory cytokine profile in rhegmatogenous retinal detachments (RRDs) compared to surgical controls. Vitreous humor was collected from patients undergoing vitrectomy for RRD and noninflammatory vitreoretinal diseases. A quantitative immunoassay was used to measure the levels of 36 cytokine markers. Linear regression analysis with the duration of detachment as the predictor and log-transformed cytokine levels as the outcome was conducted for normally distributed cytokines as determined by the Shapiro-Wilk test. The analysis was adjusted for age, sex, and race. The Kruskal-Wallis test was used for cytokines not normally distributed. Twenty-seven RRD cases and thirteen control cases were studied. Between all RRDs and controls, fibroblast growth factor 2 (FGF2) (p = 0.0029), inducible protein-10(IP-10) (p = 0.0021), monocyte chemoattractant protein-1 (MCP-1) (p = 0.0040), interleukin (IL)-16 (p = 0.018), IL-8 (p = 0.0148), IL-6 (p = 0.0071), eotaxin (p = 0.0323), macrophage inflammatory protein (MIP)-1 alpha (p = 0.0149), MIP-1 beta (p = 0.0032), and the thymus and activation regulated cytokine (TARC) (p = 0.0121) were elevated in RRD cases. Between acute RRDs (n = 16) and controls, FGF2 (p = 0.0001), IP10 (p = 0.0027), MCP-1 (p = 0.0015), MIP-1β (p = 0.0004), IL-8 (p = 0.0146), and IL-6 (p = 0.0031) were elevated. Determining alterations in inflammatory cytokine profiles may aid in understanding their impact on RRD development, clinical course, and complications before and after surgical repair.

Outcomes and predictors of vitrectomy and silicone oil tamponade in retinal detachments complicated by proliferative vitreoretinopathy

AIM

To evaluate outcomes and determine factors influencing the outcomes of vitrectomy with silicone oil (SO) endotamponade for the management of rhegmatogenous retinal detachment (RRD) complicated by advanced proliferative vitreoretinopathy (PVR).

METHODS

This is a retrospective, interventional case series of eyes with PVR grade C associated RRD with or without prior surgery that underwent vitreoretinal surgery and SO tamponade. Eyes with a minimum follow-up of 6mo after SO extraction were included. Eyes were classified into three PVR subgroups according to severity and extension of proliferation. The influence of several preoperative, intraoperative and postoperative factors upon the functional and anatomical outcomes was assessed using multivariate logistic regression analysis.

RESULTS

A hundred and one eyes of 101 patients that met the inclusion criteria were studied. Seventy-five of 101 eyes (74.3%) had successful retinal reattachment after one operation. Increased aqueous cell and flare at the first week exam had a statistically significant association with redetachment, recurrent membrane proliferation and keratopathy. Visual acuity improvement was significantly associated with faint postoperative aqueous inflammation values, primary vitrectomy and PVR outside of the posterior pole.

CONCLUSION

Although encouraging anatomical and functional outcomes are achieved after vitrectomy and SO tamponade in eyes with RRD complicated by PVR, an increase in aqueous flare or cells at the first week follow-up is most likely to result in postoperative late complications. Primary vitrectomy, PVR associated with minimal posterior pole extension and absent to mild postoperative aqueous inflammation are associated with improved post-operative final visual acuity.

MicroRNA-4516 suppresses proliferative vitreoretinopathy development via negatively regulating OTX1

Proliferative vitreoretinopathy (PVR) progression is associated with TGF-β2-induced epithelial–mesenchymal transition (EMT) in retinal pigment epithelial (RPE) cells. In cancer cells, miR-4516 downregulates orthodenticle homeobox 1 (OTX1)-mediated cell invasion. Moreover, OTX1 is shown to be involved in invasion and EMT. The purpose of this study was to assess whether microRNA (miR-4516) suppresses EMT in RPE cells. EMT features were assessed using Western blotting, immunocytochemical staining, scratch-wound healing, modified Boyden chamber assay, and collagen gel contraction assay. For in vivo testing, a rabbit model was used, which involved induction of PVR by injection of transfected spontaneously arising RPE (ARPE) cells into the vitreous chamber. The putative target of miR-4516 was identified by luciferase reporter assay. Results showed that TGF-β2-induced transdifferentiation and migration of RPE cells was inhibited by miR-4516 delivery. Overexpression of miR-4516 led to upregulation of zonula occludens-1, downregulation of α-smooth muscle actin and vimentin, and cell contractility—all EMT features—in the TGF-β2-treated ARPE-19 cells. MiR-4516 regulated OTX1 expression negatively by binding to its 3’-UTR. TGF-β2-induced phosphorylated ERK was inhibited in miR-4516-overexpressing ARPE-19 cells. MiR-4516 suppressed experimental PVR in vitro and in vivo. In conclusion, the overexpression of miR-4516 suppresses TGF-β2-induced EMT in a PVR model, and its role in PVR depends on OTX1/ERK. Further research is needed to develop a feasible treatment method to prevent and treat PVR.

miRNA‑124 regulates palmitic acid‑induced epithelial‑mesenchymal transition and cell migration in human retinal pigment epithelial cells by targeting LIN7C

The present study revealed that palmitic acid (PA) treatment induced epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, which are involved in the progression of proliferative vitreoretinopathy (PVR). ARPE-19 cells were treated with PA followed by miRNA screening and EMT marker detection using qRT-PCR. Then, miR-124 mimic or inhibitor was transfected into ARPE-19 cells to explore the role of miR-124 on the EMT of ARPE-19 cells using transwell assay. The underlying mechanism of miRNA were predicted by bioinformatics method and confirmed by luciferase activity reporter assay. Furthermore, gain-of-function strategy was also used to explore the role of LIN7C in the EMT of ARPE-19 cells. The expression of miRNA or mRNA expression was determined by qRT-PCR and the protein expression was determined using western blot assay. The result presented that PA reduced the expression of E-cadherin/ZO-1 whilst increasing the expression of fibronectin/α-SMA. In addition, PA treatment enhanced the expression of microRNA (miR)-124 in ARPE-19 cells. Overexpression of miR-124 enhanced PA-induced upregulation of E-cadherin and ZO-1 expression and downregulation of fibronectin and α-SMA. Moreover, miR-124 mimic also enhanced the migration of ARPE-19 cells induced by PA treatment. Inversely, miR-124 inhibitor presented opposite effect on PA-induced EMT and cell migration in ARPE-19 cells. Luciferase activity reporter assay confirmed that Lin-7 homolog C (LIN7C) was a direct target of miR-124 in ARPE-19 cells. Overexpression of LIN7C was found to suppress the migration ability and expression of fibronectin and α-SMA, while increasing expression of E-cadherin and ZO-1; miR-124 mimic abrogated the inhibitive effect of LIN7C on the EMT of ARPE-19 cells and PA further enhanced this abolishment. Collectively, these findings suggest that miR-124/LIN7C can modulate EMT and cell migration in RPE cells, which may have therapeutic implications in the management of PVR diseases.

Therapeutic Validation of GEF-H1 Using a De Novo Designed Inhibitor in Models of Retinal Disease

Inflammation and fibrosis are important components of diseases that contribute to the malfunction of epithelia and endothelia. The Rho guanine nucleotide exchange factor (GEF) GEF-H1/ARHGEF-2 is induced in disease and stimulates inflammatory and fibrotic processes, cell migration, and metastasis. Here, we have generated peptide inhibitors to block the function of GEF-H1. Inhibitors were designed using a structural in silico approach or by isolating an inhibitory sequence from the autoregulatory C-terminal domain. Candidate inhibitors were tested for their ability to block RhoA/GEF-H1 binding in vitro, and their potency and specificity in cell-based assays. Successful inhibitors were then evaluated in models of TGFβ-induced fibrosis, LPS-stimulated endothelial cell-cell junction disruption, and cell migration. Finally, the most potent inhibitor was successfully tested in an experimental retinal disease mouse model, in which it inhibited blood vessel leakage and ameliorated retinal inflammation when treatment was initiated after disease diagnosis. Thus, an antagonist that blocks GEF-H1 signaling effectively inhibits disease features in in vitro and in vivo disease models, demonstrating that GEF-H1 is an effective therapeutic target and establishing a new therapeutic approach.

A bio-functional polymer that prevents retinal scarring through modulation of NRF2 signalling pathway

One common cause of vision loss after retinal detachment surgery is the formation of proliferative and contractile fibrocellular membranes. This aberrant wound healing process is mediated by epithelial-mesenchymal transition (EMT) and hyper-proliferation of retinal pigment epithelial (RPE) cells. Current treatment relies primarily on surgical removal of these membranes. Here, we demonstrate that a bio-functional polymer by itself is able to prevent retinal scarring in an experimental rabbit model of proliferative vitreoretinopathy. This is mediated primarily via clathrin-dependent internalisation of polymeric micelles, downstream suppression of canonical EMT transcription factors, reduction of RPE cell hyper-proliferation and migration. Nuclear factor erythroid 2-related factor 2 signalling pathway was identified in a genome-wide transcriptomic profiling as a key sensor and effector. This study highlights the potential of using synthetic bio-functional polymer to modulate RPE cellular behaviour and offers a potential therapy for retinal scarring prevention.

Proteomic Insight into the Role of Exosomes in Proliferative Vitreoretinopathy Development

Purpose: To characterize vitreous humor (VH) exosomes and to explore their role in the development of proliferative vitreoretinopathy (PVR) using mass spectrometry-based proteome profiling. Methods: Exosomes were isolated from undiluted VH from patients with retinal detachment (RD) with various stages of PVR (n = 9), macular hole (MH; n = 5), or epiretinal membrane (ERM; n = 5) using differential ultracentrifugation. The exosomal size, morphology, and exosome markers were analyzed using a nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and an exosome detection antibody array. The tryptic fragment sequencing of exosome-contained proteins was performed using liquid chromatography–tandem mass spectrometry (LC-MS/MS) and a Thermo Lumos Fusion Tribrid Orbitrap mass spectrometer. The pathway analysis of the MS data was performed. Results: The number of exosome particles were significantly increased only in the RD with severe PVR group compared with the control groups and the RD without PVR or with mild PVR groups. Of 724 exosome proteins identified, 382 were differentially expressed (DE) and 176 were uniquely present in PVR. Both DE proteins and exosome proteins that were only present in PVR were enriched in proteins associated with previously known key pathways related to PVR development, including reactive retinal gliosis, pathologic cellular proliferation, inflammation, growth of connective tissues, and epithelial mesenchymal transition (EMT). The SPP1, CLU, VCAN, COL2A1, and SEMA7A that are significantly upregulated in PVR were related to the tissue remodeling. Conclusions: Exosomes may play a key role in mediating tissue remodeling along with a complex set of pathways involved in PVR development.

Dopamine Receptor Signaling Regulates Fibrotic Activation of Retinal Pigmented Epithelial Cells

Retinal pigmented epithelial (RPE) cells play an important role in retinal fibrotic diseases such as proliferative vitreoretinopathy (PVR). The purpose of this study was to elucidate the involvement of dopamine receptor signaling in regulating the fibrotic activation of RPE cells. Dopamine receptor expression, the effect of dopamine on fibrotic activity, and dopamine production were measured in the human RPE cell line ARPE-19. The fibrotic activation of RPE cells was evaluated in response to treatments with selective dopamine receptor agonists and antagonists by measuring gene expression, migration, proliferation, and fibronectin deposition. DRD2 and DRD5 are the dominant dopaminergic receptors expressed in ARPE-19 cells and TGFβ stimulates enhances autocrine release of dopamine which we show further exasperates fibrotic activation. Finally, treatment with D2 dopamine receptor antagonists or D5 dopamine receptor agonists inhibits profibrotic gene expression, migration, proliferation, and fibronectin deposition and thus may serve as effective mechanisms for treating retinal fibrosis including PVR.

Emergency Vitrectomies for Retinal Detachment Before and During the Coronavirus Pandemic - A Retrospective Single Centre Analysis

Background While the corona pandemic and the resulting containment measures affect the number of elective surgical procedures, the impact on emergency surgical interventions is less tangible. This analysis quantifies the frequency of emergency vitrectomies for retinal detachment and investigates underlying factors.

Methods Retrospective identification of patients who underwent primary emergency vitrectomies for retinal detachment at the Cantonal Hospital of Lucerne between 01.01.2018 – 31.12.2020. Parameters were collected, including demographics, date of hospitalisation, reported onset of symptoms, pre-operative best corrected visual acuity (BCVA), involvement of the macula, and canton of residence.

Results Overall, a total of 665 patients with 683 eyes underwent emergency surgery for primary retinal detachment in the time span of 01.01.2018 – 31.12.2020. Median monthly number of surgeries was 20. During the first Swiss national lockdown (16.03.2020 – 19.04.2020), a minimum of 9 vitrectomies was recorded in March 2020. A maximum of 36 vitrectomies was conducted in August 2020. The mean age of patients was 61.5 years. Of the 665 patients, 133 (20.0%) were residents of the canton of Ticino. Median pre-operative BCVA was 0.25 over all three years, and no significant reduction in pre-operative BCVA was observed during or after the lockdown. The proportion of eyes with involvement of the macula was 52.2%. In 2018, this proportion (47.6%) was significantly lower than in 2019 and 2020 (Chi ² test, p < 0.001). However, cases with macular involvement in post lockdown months were not more frequent. Median time in days from reported symptom onset to hospitalisation was 5 days. In April 2020, the proportion of patients with > 14 days symptom duration was significantly higher (Chi ² test, p < 0.001). During the lockdown, there was a significant reduction in cases from Ticino. Also, patients from Ticino showed proportionally longer symptom duration after the lockdown.

Conclusion A significant reduction in the number of emergency vitrectomies was observed for the initial period of the coronavirus pandemic. Delayed emergency presentation is not assumed, since there was no increase in severity (i.e. macular involvement) or prolonged symptoms in the months following the lockdown. More protracted symptoms were only observed in patients from Ticino. The initial low numbers were generally made good later in the year.

Raloxifene, a cannabinoid type-2 receptor inverse agonist, mitigates visual deficits and pathology and modulates microglia after ocular blast

Visual deficits after ocular blast injury (OBI) are common, but pharmacological approaches to improve long-term outcomes have not been identified. Blast forces frequently damage the retina and optic nerves, and work on experimental animals has shown the pro-inflammatory actions of microglia can further exacerbate such injuries. Cannabinoid type-2 receptor (CB2) inverse agonists specifically target activated microglia, biasing them away from the harmful pro-inflammatory M1 state toward the helpful reparative M2 state. We previously found that treating mice with CB2 inverse agonists after traumatic brain injury, produced by either focal cranial air blast or dorsal cranial impact, greatly attenuated the visual deficits and pathology that otherwise resulted. Here we examined the consequences of single and repeat OBI and the benefit provided by raloxifene, an FDA-approved estrogen receptor drug that possesses noteworthy CB2 inverse agonism. After single OBI, although the amplitudes of the A- and B-waves of the electroretinogram and pupil light response appeared to be normal, the mice showed hints of deficits in contrast sensitivity and visual acuity, a trend toward optic nerve axon loss, and significantly increased light aversion, which were reversed by 2 weeks of daily treatment with raloxifene. Mice subjected to repeat OBI (5 blasts spaced 1 min apart), exhibited more severe visual deficits, including decreases in contrast sensitivity, visual acuity, the amplitudes of the A- and B-waves of the electroretinogram, light aversion, and resting pupil diameter (i.e. hyperconstriction), accompanied by the loss of photoreceptor cells and optic nerve axons, nearly all of which were mitigated by raloxifene. Interestingly, optic nerve axon abundance was strongly correlated with contrast sensitivity and visual acuity across all groups of experimental mice in the repeat OBI study, suggesting optic nerve axon loss with rOBI and its attenuation with raloxifene are associated with the extent of these two deficits while photoreceptor abundance was highly correlated with A-wave amplitude and resting pupil size, suggesting a prominent role for photoreceptors in these two deficits. Quantitative PCR (qPCR) showed levels of M1-type microglial markers (e.g. iNOS, IL1β, TNFα, and CD32) in retina, optic nerve, and thalamus were increased 3 days after repeat OBI. With raloxifene treatment, the overall expression of M1 markers was more similar to that in sham mice. Raloxifene treatment was also associated with the elevation of IL10 transcripts in all three tissues compared to repeat OBI alone, but the results for the three other M2 microglial markers we examined were more varied. Taken together, the qPCR results suggest that raloxifene benefit for visual function and pathology was associated with a lessening of the pro-inflammatory actions of microglia. The benefit we find for raloxifene following OBI provides a strong basis for phase-2 efficacy testing in human clinical trials for treating ocular injury.

Epiretinal proliferation after rhegmatogenous retinal detachment

PURPOSE

To determine the characteristics and appearance rate of epiretinal proliferation (ERP) on SD-OCT after surgery for rhegmatogenous retinal detachment (RRD) repair.

METHODS

One hundred eight eyes of 108 patients who underwent one or more surgeries for RRD were enrolled. The eyes with other maculopathies that were directly related to RRD were excluded. Image acquisition was performed with SD-OCT (Heidelberg Engineering, Germany). Clinical charts were reviewed to assess clinical and surgical findings. Statistical analyses were performed using XLSTAT (Assinsoft, Paris, France).

RESULTS

ERP was found in 9.3% eyes (n = 10). The mean initial visual acuity (logMAR) was 1.34 ± 0.82 in the ERP group compared to 0.49 ± 0.70 in the non-ERP group. PVR was present in 70.0% and chronic macular edema was found in 80.0% of eyes which developed ERP. The mean number of vitreoretinal surgeries in eyes with ERP was 3.3 ± 1.19 and only 1.44 ± 1.02 in eyes without. Silicone oil was used in 60.0% of eyes which developed ERP compared to 13.9% in the non-ERP group.

CONCLUSION

ERP is a late-onset postoperative finding in eyes with RRD and can occur in absence of macular holes. Overall, ERP is more frequent in eyes with complicated courses of RRD including multiple operations, PVR, usage of silicone oil, and chronic macular edema.

Vitreoschisis and retinal detachment: New insight in proliferative vitreoretinopathy

PURPOSE

To assess the occurrence of peripheral vitreoschisis-induced vitreous cortex remnants (p-VCRs) in primary rhegmatogenous retinal detachment (RD) and investigate whether the presence of p-VCRs results in a greater risk of RD recurrence, secondary to Proliferative Vitreoretinopathy (PVR) development after pars plana vitrectomy (PPV).

METHODS

Patients who underwent PPV for primary rhegmatogenous RD between January 2016 and December 2018 were included. The presence of residual p-VCRs was confirmed intraoperatively using triamcinolone acetonide (TA). Patients with p-VCRs were divided into two groups: Group A comprised of patients who underwent PPV without p-VCR removal, while Group B included patients who underwent PPV with p-VCR removal.

RESULTS

Four hundred-thirteen eyes with evidence of p-VCR were analyzed. Two-hundred-twenty-three eyes underwent PPV without VCR removal (Group A), while 190 eyes underwent PPV with p-VCR removal (Group B). Primary anatomical success was 91.5% in the Group A and 95.4% in the group B. Retinal re-detachment due to PVR occurred in 17 (7.6%) eyes in Group A and in four (2.1%) eyes in Group B within the first 3 months (p  =  0.01). Among group A, in 11 eyes, there was a diffuse posterior PVR grade C, while six eyes were focal PVR grade C. In Group B, we observed four retinal re-detachment due to focal PVR grade C.

CONCLUSION

The presence of p-VCRs seems to be associated with a higher incidence of PVR development and might also result in more complex RD recurrence, this suggests the need for more aggressive VCRs removal during the first surgery.

LncRNA NEAT1 Recruits SFPQ to Regulate MITF Splicing and Control RPE Cell Proliferation

Purpose

Retinal pigment epithelium (RPE) cell proliferation is precisely regulated to maintain retinal homoeostasis. Microphthalmia-associated transcription factor (MITF), a critical transcription factor in RPE cells, has two alternatively spliced isoforms: (+)MITF and (-)MITF. Previous work has shown that (-)MITF but not (+)MITF inhibits RPE cell proliferation. This study aims to investigate the role of long non-coding RNA (lncRNA) nuclear-enriched abundant transcript 1 (NEAT1) in regulating MITF splicing and hence proliferation of RPE cells.

Methods

Mouse RPE, primary cultured mouse RPE cells, and different proliferative human embryonic stem cell (hESC)-RPE cells were used to evaluate the expression of (+)MITF, (-)MITF, and NEAT1 by reverse-transcription PCR (RT-PCR) or quantitative RT-PCR. NEAT1 was knocked down using specific small interfering RNAs (siRNAs). Splicing factor proline- and glutamine-rich (SFPQ) was overexpressed with the use of lentivirus infection. Cell proliferation was analyzed by cell number counting and Ki67 immunostaining. RNA immunoprecipitation (RIP) was used to analyze the co-binding between the SFPQ and MITF or NEAT1.

Results

NEAT1 was highly expressed in proliferative RPE cells, which had low expression of (-)MITF. Knockdown of NEAT1 in RPE cells switched the MITF splicing pattern to produce higher levels of (-)MITF and inhibited cell proliferation. Mechanistically, NEAT1 recruited SFPQ to bind directly with MITF mRNA to regulate its alternative splicing. Overexpression of SFPQ in ARPE-19 cells enhanced the binding enrichment of SFPQ to MITF and increased the splicing efficiency of (+)MITF. The binding affinity between SFPQ and MITF was decreased after NEAT1 knockdown.

Conclusions

NEAT1 acts as a scaffold to recruit SFPQ to MITF mRNA and promote its binding affinity, which plays an important role in regulating the alternative splicing of MITF and RPE cell proliferation.

Intraocular perfluorodecalin and silicone oil tamponade (double filling) in the management of complicated retinal detachment: functional and anatomical outcomes using small-gauge surgery

Purpose

To describe the functional and anatomical results of complicated retinal detachment (RD) treated with small-gauge pars plana vitrectomy (PPV) and combined perfluorodecalin and polydimethylsiloxane tamponade (double filling, DF).

Methods

Retrospective analysis of consecutive patients with complex RD (severe proliferative vitreoretinopathy, inferior/posterior/giant retinal tears, and traumatic detachments) treated with small-gauge PPV, membrane peeling, and DF at the Department of Ophthalmology at San Gerardo Hospital, Monza, Italy. Main outcome measures included best-corrected visual acuity (BCVA), rates of retinal reattachment, and complications.

Results

This study included 15 patients with a median follow-up (FU) of 6 months (range 1–22). Three patients with early retinal redetachment under tamponade and FU shorter than 3 months were excluded from the final functional analysis, but they were considered anatomical failure. At the last examination, BCVA improved in 50% of patients and remained stable in 25% of patients and anatomical success was achieved in 73% of eyes, 64% of them without any endotamponade. Three eyes had retinal redetachment after perfluorodecalin/silicone oil exchange because of diffuse proliferative vitreoretinopathy (PVR) and required reoperation to achieve retinal attachment. In eyes with anatomical success, macular pucker was the most frequent long-term complication (27%).

Conclusion

In the management of complex RD, small-gauge pars plana vitrectomy, and double filling endotamponade using wide-angle viewing systems was a well-tolerated and effective technique to preserve visual acuity and achieve anatomical success.

The Proteome of Preretinal Tissue in Proliferative Vitreoretinopathy

BACKGROUND AND OBJECTIVE

Proliferative vitreoretinopathy (PVR) is the leading cause of retinal detachment repair failure. However, the molecular pathogenesis remains incompletely understood. Determining the proteome of PVR will help to identify novel therapeutic targets.

MATERIALS AND METHODS

Preretinal tissue samples, delaminated during surgery from six PVR cases and one idiopathic epiretinal membrane (ERM) were analyzed by mass spectrometry. Tandem mass spectra were extracted using the UniProt database, generating a list of 896 proteins, which were subjected to pathway set and fold-change (ERM vs PVR) analyses.

RESULTS

Two pathways were enriched in PVR: extracellular matrix (ECM) organization and extracellular structure organization. A fold-change analysis comparing mean total spectral counts from PVR to an ERM control identified fibronectin, the ECM glycoprotein, as the protein most significantly elevated in PVR compared to ERM.

CONCLUSION

These data identify pathwayskey to PVR progression, including thoseinvolved in cell-mediated ECM assembly and thus tractional force generation at the cellular level. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:S5-S12.].