Assessing the therapeutic potential of astaxanthin in experimental proliferative vitreoretinopathy models

PurposeThis study evaluates the effectiveness of astaxanthin in treating experimental proliferative vitreoretinopathy (PVR) in rats.MethodsFifty-six Sprague Dawley rats were divided into 4 groups. PVR was induced using dispase and astaxanthin was administered intravitreally at concentrations of 10 ng/μL and 100 ng/μL. The effects on TGF-ß, VEGF, PDGF, FGF2 and IL-1ß were measured by ELISA and retinal changes were analysed histopathologically and immunohistochemically.ResultsAstaxanthin at 10 ng/μL and 100 ng/μL administered to the treatment groups significantly decreased TGF-β, VEGF, FGF2, IL-1, and PDGF levels compared to the sham group (p < 0.05). At the 100 ng/μL dose, more significant decreases were observed, especially in PDGF and IL-1 levels (p < 0.01). Histopathologic scoring revealed that the treated groups had significantly lower PVR scores than the Sham group, with the highest dose showing the greatest improvement (p < 0.01). Furthermore, treated groups exhibited improved retinal architecture and reduced fibrotic tissue formation. Immunohistochemical staining for VEGF was positive in all groups except Control, with no significant differences in VEGF expression intensity between groups.ConclusionAstaxanthin effectively reduces both biochemical and histopathological markers of PVR, highlighting its potential as a novel therapeutic agent for managing this challenging condition in clinical practice.

Multikinase inhibition-mediated proliferative vitreoretinopathy therapy by nanoparticles in rabbits

Purpose

To investigate the efficacy of nanoparticles in treating proliferative vitreoretinopathy (PVR) through clinical observation, histology, and immunohistochemistry, despite unsatisfactory surgical outcomes and failed therapies for the current PVR treatment.

Design

Twelve rabbits were divided into control and nintedanib (NTB) groups. The rabbits underwent weekly ophthalmologic examinations over a period of four weeks.

Methods

At the end of the fourth week, the rabbits' eyes were removed for histological and immunohistochemical evaluation. Three additional rabbits outside the PVR model were administered a 0.5% NTB-loaded liposomal formulation in one eye. The drug concentrations in the vitreous samples were determined using high-pressure liquid chromatography on days 1, 7, 14, and 35.

Results

The PVR stages were low in the NTB group, and there was no significant difference between the NTB and control groups (p = 0.108). However, it is worth noting that the group treated with NTB had significantly fewer epiretinal membrane formations during the histological evaluation. In addition, the corrected fluorescence intensity measurement of the subjects for collagen-1 in the NTB group was significantly lower than that in the control group (p = 0.004). Most importantly, no significant adverse effects were observed.

Conclusions

Our study has provided preclinical support for a liposomal formulation containing NTB that, with single-dose administration, has the potential to be effective in vivo in preventing the development of PVR and its correlated pathologies without causing any significant side effects.

Intravitreal melatonin for the prevention of radiation retinopathy: a step beyond bevacizumab

PURPOSE

Intravitreal bevacizumab has been utilized to mitigate radiation retinopathy, yet the potential role of intravitreal melatonin for its prevention remains unexplored. This study aims to evaluate and compare the efficacy of intravitreal melatonin and bevacizumab in preventing radiation retinopathy in an experimental animal model.

MATERIALS AND METHODS

Twelve healthy male New Zealand white rabbits (n = 24 eyes) received a single 3000 cGy irradiation dose in both eyes. Intravitreal melatonin (100 mcg/kg = 300 mcg/0.05 mL) was administered to the left eyes of six rabbits, and bevacizumab (1.25 mg/0.05 mL) to the left eyes of the remaining six, with sham injections given to the right eyes as controls. Six weeks after irradiation, bilateral enucleation was performed for biochemical and histopathological evaluation.

RESULTS

Oxidative stress markers did not differ significantly between the groups (p = .827). Both melatonin and bevacizumab treatments markedly reduced axonal damage compared to the sham control group (p < .001). Melatonin also demonstrated a trend toward superior neuroprotective effects relative to bevacizumab, though this difference was not statistically significant (p = .07).

CONCLUSIONS

Intravitreal melatonin demonstrated efficacy comparable to bevacizumab in reducing radiation-induced retinopathy, with an encouraging trend toward enhanced neuroprotection. These findings position melatonin as a potential novel therapeutic for radiation retinopathy prophylaxis. Further research with larger, long-term studies is warranted to validate these results and investigate melatonin's broader applications in retinal protection.

Proliferative Vitreoretinopathy in Retinal Detachment: Perspectives on Building a Digital Twin Model Using Nintedanib

Proliferative vitreoretinopathy (PVR) is a pathological process characterized by the formation of fibrotic membranes that contract and lead to recurrent retinal detachment. Pars plana vitrectomy (PPV) is the primary treatment, but recurrence rates remain high, as surgery does not address the underlying molecular mechanisms driving fibrosis. Despite several proposed pharmacological interventions, no approved therapies exist, partly due to challenges in conducting preclinical and in vivo studies for ethical and safety reasons. This review explores the potential of computational models and Digital Twins, which are increasingly gaining attention in medicine. These tools could enable the development of progressively complex PVR models, from basic simulations to patient-specific Digital Twins. Nintedanib, a tyrosine kinase inhibitor targeting PDGFR, VEGFR, and FGFR, is presented as a prototype for computational models to simulate its effects on fibrotic pathways in virtual patient cohorts. Although still in its early stages, the integration of computational models and Digital Twins offers promising avenues for improving PVR management through more personalized therapeutic strategies.

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.

Targeting non-muscle myosin II inhibits proliferative vitreoretinopathy through regulating epithelial-mesenchymal transition

Proliferative vitreoretinopathy (PVR) is a common complication of rhegmatogenous retinal detachment, eventually leading to vision loss. To date, there are no effective drugs for the treatment of this disease. In this study, we investigated the effect of blebbistatin, a non-muscle myosin II inhibitor, on the ARPE-19 cell line and in a rabbit model of proliferative vitreoretinopathy. In vitro, we found that blebbistatin inhibited the epithelial-mesenchymal transition of retinal pigment epithelial (RPE) cells and inhibited the ability of RPE cells to migrate, proliferate, generate extracellular matrix, and affect contractility. In vivo the PVR model showed that blebbistatin significantly delayed PVR progression. It also partially prevents the loss of retinal function caused by PVR. Our results suggest that blebbistatin is a potential drug with clinical applications for the treatment of PVR.

Evaluation of a steroid delivery system to mitigate the severity of proliferative vitreoretinopathy in a minipig model

Purpose

To investigate the efficacy of liposomal prednisolone phosphate to mitigate the severity of proliferative vitreoretinopathy (PVR) in a minipig model of PVR.

Methods

A total of 18 eyes of 9 minipigs underwent PVR induction surgically. Eyes were randomized equally into three groups: intravitreal injection of liposomal prednisolone phosphate (LPP), triamcinolone acetonide (TA), and controls. PVR severity was graded on fundoscopic examination using a modified version of the Silicon Study Classification System. Severe PVR was defined as grade 2-5 on this classification, and the proportion of eyes with retinal detachment from severe PVR, defined as retinal re-detachment, i.e., PVR grade 2-5, was compared between treatment and control groups.

Results

On day 28, five eyes (83.3%) in the control group were observed to have severe PVR. Within the LPP group, one (16.7%) eye developed retinal detachment due to severe PVR. Grade 0 PVR was observed in four (66.7%) eyes, grade 1 in one (16.7%) eye, and grade 5 in one (16.7%) eye. Within the TA group, grade 0 PVR was observed in four eyes (66.7%), grade 1 in two eyes (16.6%), and grade 5 in one (16.7%) eye. The difference in the proportion of eyes with severe PVR was significantly lower in the LPP group compared to controls at day 28 (16.7% vs 83.3%, p=0.02). There was no significant difference in the rate of severe PVR or median PVR grade between the liposomal prednisolone phosphate and triamcinolone acetonide groups.

Conclusion

Liposomal prednisolone phosphate reduces the severity of PVR in a minipig model of PVR.

Experimental Models to Study Epithelial-Mesenchymal Transition in Proliferative Vitreoretinopathy

Proliferative vitreoretinal diseases (PVDs) encompass proliferative vitreoretinopathy (PVR), epiretinal membranes, and proliferative diabetic retinopathy. These vision-threatening diseases are characterized by the development of proliferative membranes above, within and/or below the retina following epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) and/or endothelial-mesenchymal transition of endothelial cells. As surgical peeling of PVD membranes remains the sole therapeutic option for patients, development of in vitro and in vivo models has become essential to better understand PVD pathogenesis and identify potential therapeutic targets. The in vitro models range from immortalized cell lines to human pluripotent stem-cell-derived RPE and primary cells subjected to various treatments to induce EMT and mimic PVD. In vivo PVR animal models using rabbit, mouse, rat, and swine have mainly been obtained through surgical means to mimic ocular trauma and retinal detachment, and through intravitreal injection of cells or enzymes to induce EMT and investigate cell proliferation and invasion. This review offers a comprehensive overview of the usefulness, advantages, and limitations of the current models available to investigate EMT in PVD.

Myo/Nog Cells Give Rise to Myofibroblasts During Epiretinal Membrane Formation in a Mouse Model of Proliferative Vitreoretinopathy

Purpose

Myo/Nog cells are the source of myofibroblasts in the lens and synthesize muscle proteins in human epiretinal membranes (ERMs). In the current study, we examined the response of Myo/Nog cells during ERM formation in a mouse model of proliferative vitreoretinopathy (PVR).

Methods

PVR was induced by intravitreal injections of gas and ARPE-19 cells. PVR grade was scored by fundus imaging, optical coherence tomography, and histology. Double label immunofluorescence localization was performed to quantify Myo/Nog cells, myofibroblasts, and leukocytes.

Results

Myo/Nog cells, identified by co-labeling with antibodies to brain-specific angiogenesis inhibitor 1 (BAI1) and Noggin, increased throughout the eye with induction of PVR and disease progression. They were present on the inner surface of the retina in grades 1/2 PVR and were the largest subpopulation of cells in grades 3 to 6 ERMs. All α-SMA-positive (+) cells and all but one striated myosin+ cell expressed BAI1 in grades 1 to 6 PVR. Folds and areas of retinal detachment were overlain by Myo/Nog cells containing muscle proteins. Low numbers of CD18, CD68, and CD45+ leukocytes were detected throughout the eye. Small subpopulations of BAI1+ cells expressed leukocyte markers. ARPE-19 cells were found in the vitreous but were rare in ERMs. Pigmented cells lacking Myo/Nog and muscle cell markers were present in ERMs and abundant within the retina by grade 5/6.

Conclusions

Myo/Nog cells differentiate into myofibroblasts that appear to contract and produce retinal folds and detachment. Targeting BAI1 for Myo/Nog cell depletion may be a pharmacological approach to preventing and treating 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.

Idelalisib inhibits experimental proliferative vitroretinopathy

Proliferative vitreoretinopathy (PVR) is a fibrotic eye disease that develops after rhegmatogenous retinal detachment surgery and open-globe traumatic injury. Idelalisib is a specific inhibitor of phosphoinositide 3-kinase (PI3K) δ. While PI3Kδ is primarily expressed in leukocytes, its expression is also considerably high in retinal pigment epithelial (RPE) cells, which play a crucial part in the PVR pathogenesis. Herein we show that GeoMx Digital Spatial Profiling uncovered strong expression of fibronectin in RPE cells within epiretinal membranes from patients with PVR, and that idelalisib (10 μM) inhibited Akt activation, fibronectin expression and collagen gel contraction induced by transforming growth factor (TGF)-β2 in human RPE cells. Furthermore, we discovered that idelalisib at a vitreal concentration of 10 μM, a non-toxic dose to the retina, prevented experimental PVR induced by intravitreally injected RPE cells in rabbits assessed by experienced ophthalmologists using an indirect ophthalmoscope plus a + 30 D fundus lens, electroretinography, optical coherence tomography and histological analysis. These data suggested idelalisib could be harnessed for preventing patients from PVR.

Intravitreal Tissue Plasminogen Activator Injection for the Treatment of Proliferative Vitreoretinopathy in a Rabbit Model

INTRODUCTION

The purpose of this study was to evaluate the effect of intravitreal injection of tissue plasminogen activator (tPA) on proliferative vitreoretinopathy (PVR).

METHODS

PVR was induced in a rabbit model by intraocular injection of dispase (0.05 U/0.1 mL). Progression of PVR was followed by indirect ophthalmic examination. Following 6 weeks, 5 animals received intravitreal injection of 25 µg/0.1 mL tPA and four were injected with balanced salt solution (BSS). Animals were euthanized at 48 h following tPA/BSS injection, and eyes were enucleated for histological evaluation and staining with α-smooth muscle actin (αSMA) and Sirius Red.

RESULTS

Following tPA injection, one eye had a reduction in PVR from grade 2 to 1 and three eyes remained stable. Following BSS, PVR grade was unchanged in three eyes. In one eye in each group, the severity of PVR could not be assessed due to limited view. Staining with αSMA showed reduced presence of fibroblasts in eyes injected with tPA compared with those injected with BSS. Collagen type I and III, demonstrated by Sirius Red staining, was reduced in the tPA group in comparison with controls.

CONCLUSION

Our results suggest that intravitreally injected tPA may show an inhibitory effect on PVR progression. Further exploration in clinical trials is desired.

Radiotherapy-induced alterations in vitreous humor: A new potential critical structure

Vitreous humor (VH) is not considered as a critical structure in the radiotherapy planning process. In the present study, an experimental animal model was performed to examine the effects of radiotherapy on VH. The right eyes of twelve New Zealand rabbits were irradiated to 60 Gy in 3 fractions in accordance with the scheme used in the treatment of uveal melanoma in our clinic, and contralateral (left) eyes were considered as control. Weekly ophthalmologic examination was performed after irradiation, for three months. At the end of the third month, enucleation and vitreous collection were conducted. The vitreous samples were subjected to metabolomic analyses, ELISA analyses, viscosity measurements, and electron microscopic examination. In control and experimental vitreous samples, 275 different metabolites were identified, and 34 were found to differ significantly between groups. In multivariate analyzes, a clear distinction was observed between control and irradiated vitreous samples. Pathway analysis revealed that nine pathways were affected, and these pathways were mainly related to amino acid metabolism. A significant decrease was observed in the expressions of type II, V, and XI collagens in protein level in the ELISA. There was a non-significant decrease in type IX collagen and viscosity. Electron microscopic examination revealed disrupted collagen fibrillar ultra-structure and dispersed collagen fragments in the experimental vitreous. An intact vitreous is essential for a healthy eye. In this study, we observed that radiation causes changes in the vitreous that may have long-term consequences.

The role of vitreous cortex remnants in proliferative vitreoretinopathy formation demonstrated by histopathology: A case report

Purpose

The pathogenesis of proliferative vitreoretinopathy (PVR), the most important cause of retinal detachment surgery failure, is still not fully understood. We previously hypothesized a causal link between vitreoschisis-induced vitreous cortex remnants (VCR) and PVR formation. The purpose of this case report is to demonstrate this association by showing the clinical occurrence of PVR in the presence of VCR across the retinal surface, illustrated by histopathological analysis.

Observations

A 69-year-old male was referred because of widespread epiretinal membrane formation after treatment of recurrent retinal detachments. During surgery with extensive membrane peeling, a large continuous membrane was peeled from the superior arcade towards the inferior temporal mid-periphery. Histopathological analysis of this membrane revealed areas with different characteristics: paucicellular laminar collagen-rich areas, suggestive for VCR, areas with increased cellularity, and more fibrotic areas with low cellularity.

The immunohistochemical analysis identified cell type variety in these areas: collagen-rich areas showed glial cells and hyalocytes, while in areas with high cellularity fibroblasts, macrophages and retinal pigment epithelial cells were found, which have previously been shown to play an important role in the development of PVR as they can transdifferentiate into myofibroblasts, which were seen in the more fibrotic areas.

Conclusions and importance

These findings support the theory that VCR have a role in PVR development, where VCR can act as a scaffold for fibrocellular proliferation. We suggest that the presence of VCR over the retinal surface should be qualified as a risk factor for PVR formation. Detection and adequate removal of VCR may improve the success rate of retinal detachment surgery.

Yes-associated protein is essential for proliferative vitreoretinopathy development via the epithelial-mesenchymal transition in retinal pigment epithelial fibrosis

This study was aim to investigate whether the progression of proliferative vitreoretinopathy (PVR) depended on the activation of Yes‐associated protein (YAP) and the subsequent epithelial‐mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cell. The effect of YAP activation on retinal fibrosis in a PVR mouse model and in human ARPE‐19 cells in vitro was studied. After treated with transforming growth factor‐β2(TGF‐β2), the expressions of fibrogenic molecules, YAP activation and the TGF‐β2‐Smad signalling pathway in ARPE‐19 cells were detected by Western blot and immunocytochemical analyses. The effect of YAP on change in fibrosis and EMT was tested by knockdown experiment using verteporfin (YAP inhibitor). YAP was upregulated in the PVR mouse model and during TGF‐β2–induced RPE cell EMT. In an in vivo study, verteporfin attenuated PVR progression in a mouse model. Additionally, YAP knockdown retained phenotype of RPE cells and ameliorated TGF‐β2–induced migration, gel contraction and EMT in vitro. YAP knockdown inhibited the TGF‐β2–induced upregulation of connective tissue growth factor (CTGF), smooth muscle actin (SMA‐α) and fibronectin. YAP was essential for the TGF‐β2–induced nuclear translocation and phosphorylation of Smad2/3. Our work provides direct evidence that YAP is an essential regulator of EMT and profibrotic responses in PVR and indicates that YAP inhibition could be a potential target in PVR therapeutic intervention.

Intravitreal connective tissue growth factor neutralizing antibody or bevacizumab alone or in combination for prevention of proliferative vitreoretinopathy in an experimental model

Connective tissue growth factor (CTGF) is released by retinal pigment epithelial (RPE) cells and detectable in proliferative membranes (PrMs). This experimental study was performed to investigate the mRNA and protein levels of both CTGF and vascular endothelial growth factor A (VEGF-A) in a rabbit model of proliferative vitreoretinopathy (PVR). In addition, the effects of a single intravitreal injection of the safe dose of anti-CTGF or bevacizumab as monotherapy and in combination were evaluated. PVR was induced in the right eye of albino rabbits by intravitreal injection of cultured adult human RPE cells. Quantitative real-time reverse transcription PCR (qRT-PCR) and Western blot analysis of CTGF and VEGF-A were performed on whole eye tissue in the PVR model versus controls at different time points. In the next step, the PVR models were assigned to five groups. The monotherapy groups received a single intravitreal injection of 0.1 ml of anti-CTGF 100 μg/ml (final concentration of 6.6 μg/ml in the vitreous) or 0.03 ml of 25 mg/ml bevacizumab. In the combined group, the abovementioned amounts of anti-CTGF and bevacizumab were injected intravitreally from separate sites in one session. No antibody injection was performed in the control group. Intravitreal injection of 0.1 ml of control IgG (1 mg/ml of isotype matched) antibody was performed in the placebo group. After 2 weeks, histologic evaluation including, trichrome staining for collagen, immunostaining by anti-alpha-smooth muscle actin for myofibroblasts, and anti-collagen type-1 antibody on paraffin embedded anterior-posterior sections was done. In addition, fundus photography was performed for clinically equivalent PVR staging. Twenty-four hours following PVR induction, CTGF mRNA and protein levels increased five- and- three-fold compared to controls, respectively (P < 0.001). VEGF-A mRNA and protein levels decreased significantly after 72 h of PVR induction compared to controls (P < 0.05). Means of PrM thickness and myofibroblast cell counts significantly decreased in the anti-CTGF group (P < 0.001 and P < 0.05, respectively). The mean area of collagen type-1 fibers of PrM in the mono- and combination therapy groups that received intravitreal anti-CTGF was significantly reduced (P < 0.001); in addition, mild PVR (stage-1 and 2) formation occurred in comparison with moderate to severe PVR (stage-4 and higher) in other groups. In conclusion, we found that intravitreal injection of CTGF neutralizing antibody resulted in a reduction in PrM thickness, collagen fibers and myofibroblast density in the PVR model. CTGF inhibition may represent a potential therapeutic target for PVR.

Topical delivery of a small molecule RUNX1 transcription factor inhibitor for the treatment of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is the leading cause of retinal detachment surgery failure. Despite significant advances in vitreoretinal surgery, it still remains without an effective prophylactic or therapeutic medical treatment. After ocular injury or retinal detachment, misplaced retinal cells undergo epithelial to mesenchymal transition (EMT) to form contractile membranes within the eye. We identified Runt-related transcription factor 1 (RUNX1) as a gene highly expressed in surgically-removed human PVR specimens. RUNX1 upregulation was a hallmark of EMT in primary cultures derived from human PVR membranes (C-PVR). The inhibition of RUNX1 reduced proliferation of human C-PVR cells in vitro, and curbed growth of freshly isolated human PVR membranes in an explant assay. We formulated Ro5-3335, a lipophilic small molecule RUNX1 inhibitor, into a nanoemulsion that when administered topically curbed the progression of disease in a novel rabbit model of mild PVR developed using C-PVR cells. Mass spectrometry analysis detected 2.67 ng/mL of Ro5-3335 within the vitreous cavity after treatment. This work shows a critical role for RUNX1 in PVR and supports the feasibility of targeting RUNX1 within the eye for the treatment of an EMT-mediated condition using a topical ophthalmic agent.

Endogenous or Exogenous Retinal Pigment Epithelial Cells: A Comparison of Two Experimental Animal Models of Proliferative Vitreoretinopathy

Purpose

Proliferative vitreoretinopathy (PVR) is a blinding condition that can occur following ocular penetrating injury and retinal detachment. To develop effective therapeutics for PVR, it is imperative to establish an animal model that is reproducible, closest in anatomy to the human eye, and most representative of the human disease. We compared two in vivo models of PVR in minipig eyes to assess reproducibility and consistency.

Methods

Six minipigs underwent PVR induction with procedure A and six underwent procedure B. In both procedures, PVR was induced with vitrectomy, bleb retinal detachment, retinotomy, and injection of platelet-rich plasma. In procedure A, retinal pigment epithelial (RPE) cells were harvested from cadaveric pig eyes and injected at the end of surgery. In procedure B, native RPE cells were released into the vitreous cavity by creating a RPE detachment and scraping the RPE layer. PVR severity was graded on fundoscopic examination with a modified Silicone Study Classification System for PVR. Severe PVR was defined as stages 2 to 5.

Results

Three eyes (50%) and five eyes (83.3%) developed re-detachment of the retina from severe PVR in procedures A and B, respectively (P = 0.55). Median PVR stage was higher in eyes that underwent procedure B compared to eyes that underwent procedure A, although the difference was not statistically significant (2.5 vs. 1.5, P = 0.26).

Conclusions

This new model utilizing native RPE cells achieved a high consistency in inducing severe PVR in the minipig.

Translational Relevance

Our model closely follows pathogenic events in human PVR, making it ideal for preclinical testing of novel therapeutics for PVR.

Cross-talk between microRNA-let7c and transforming growth factor-β2 during epithelial-to-mesenchymal transition of retinal pigment epithelial cells

AIM

To explore the roles of microRNA-let7c (miR-let7c) and transforming growth factor-β2 (TGF-β2) and cellular signaling during epithelial-to-mesenchymal transition (EMT) of retinal pigment epithelial cells.

METHODS

Retinal pigment epithelial (ARPE-19) cells were cultured with no serum for 12h, and then with recombinant human TGF-β2 for different lengths of time. ARPE-19 cells were transfected with 1×10⁶ TU/mL miR-let7c mimcs (miR-let7cM), miR-let7c mimcs negative control (miR-let7cMNC) and miR-let7c inhibitor (miR-let7cI) using the transfection reagent. The expression of keratin-18, vimentin, N-cadherin, IKB alpha, p65 were detected by Western blot, quantitative polymerase chain reaction and immunofluorescence.

RESULTS

The expression of miR-let7c was dramatically reduced and the nuclear factor-kappa B (NF-κB) signaling pathway was activated after induction by TGF-β2 (P<0.05). In turn, overexpressed miR-let7c significantly inhibited TGF-β2-induced EMT (P<0.05). However, miR-let7c was unable to inhibit TGF-β2-induced EMT when the NF-κB signaling pathway was inhibited by BAY11-7082 (P<0.01).

CONCLUSION

The miR-let7c regulates TGF-β2-induced EMT through the NF-κB signaling pathway in ARPE-19 cells.

Detection of Retinal Fibrosis in a Rabbit Model of Penetrating Eye Injury

INTRODUCTION

To establish a rabbit model of posterior penetrating eye injury as a platform to test potential therapeutics.

MATERIALS AND METHODS

Anesthetized rabbits received posterior penetrating eye injury in one eye, whereas contralateral eyes were maintained as uninjured controls. Rabbits were randomized into two experimental groups. Group A was euthanized on Day 14 postinjury to determine retinal fibrosis at an early phase of disease progression. Group B was euthanized on Day 28 postinjury to examine retinal fibrosis at a late phase of disease progression. We examined animals on postinjury Days 7, 14, 21, and 28 with indirect ophthalmoscope and fundus photography. After euthanasia, eyes were processed for histology and immunofluorescence labeling of fibrotic proteins α-smooth muscle actin and collagen I.

RESULTS

Early fibrosis was detected by Day 14, as indicated by indirect ophthalmoscopy and fundus imaging. Fibrotic membranes were visible at sites of injury. Immunofluorescence analysis detected α-smooth muscle actin and collagen I within the fibrotic membranes.

CONCLUSIONS

These data show that ocular fibrosis can be detected within 14 days after initial injury, with more severe fibrosis detected at 28 days postinjury. These results will be used to determine the optimal time points for later studies designed to test treatment strategies.

Phosphoinositide 3-kinase δ inactivation prevents vitreous-induced activation of AKT/MDM2/p53 and migration of retinal pigment epithelial cells

Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that play a critical role in transmitting signals from cell-surface molecules to intracellular protein effectors. Key PI3Ks include PI3Kα, PI3Kβ, and PI3Kδ, which are regulated by receptors. The signaling pathway comprising the PI3Ks, along with a Ser/Thr kinase (AKT), a proto-oncogene product (mouse double minute (MDM)2), and a tumor suppressor protein (p53), plays an essential role in experimental proliferative vitreoretinopathy (PVR), which is a fibrotic blinding eye disorder. However, which PI3K isoforms are involved in PVR is unknown. A major characteristic of PVR is the formation of epi (or sub)-retinal membranes that consist of extracellular matrix and cells, including retinal pigment epithelium (RPE) cells, glial cells, and macrophages. RPE cells are considered key players in PVR pathogenesis. Using immunoblotting and immunofluorescence analyses, we herein provide the evidence that PI3Kδ is highly expressed in human RPEs when it is primarily expressed in leukocytes. We also found that PI3Kδ inactivation through two approaches, CRISPR/Cas9-mediated depletion and a PI3Kδ-specific inhibitor (idelalisib), not only blocks vitreous-induced activation of AKT and MDM2 but also abrogates a vitreous-stimulated decrease in p53. Furthermore, we demonstrate that PI3Kδ inactivation prevents vitreous-induced proliferation, migration, and contraction of human RPEs. These results suggest that PI3Kδ may represent a potential therapeutic target for RPE-related eye diseases, including PVR.