Vascular endothelial growth factor acts primarily via platelet-derived growth factor receptor α to promote proliferative vitreoretinopathy

Development and validation of the Artificial Intelligence-Proliferative Vitreoretinopathy (AI-PVR) Insight system for deep learning-based diagnosis and postoperative risk prediction in proliferative vitreoretinopathy using multimodal fundus imaging

Background

Early diagnosis of proliferative vitreoretinopathy (PVR) is crucial for preventing vision loss and ensuring effective treatment of retinal detachment. This study developed and validated a system named Artificial Intelligence-Proliferative Vitreoretinopathy (AI-PVR) Insight, which aims to automate the identification, grading, and postoperative risk assessment of PVR.

Methods

We retrospectively collected data from 1,700 eyes of 1,700 patients who underwent vitrectomy at the Eye Hospital affiliated with Nanchang University and at Jiangxi Provincial People's Hospital from June 2015 to December 2023 for the development and validation of the AI-PVR Insight system performance. This system is based on two deep learning models, TwinsSVT and DenseNet-121, which extract features from three modalities: B-scan ultrasound (B-scan), optical coherence tomography (OCT), and ultra-widefield (UWF) retinal imaging. After principal component analysis (PCA) dimension reduction and feature fusion, multi-layer perceptron (MLP) or support vector machine (SVM) classifiers are used to identify PVR, assess severity, and predict postoperative risks. The performance of the system was evaluated by calculating area under the curve (AUC) values, accuracy, precision, recall, and F1 scores.

Results

The AI-PVR Insight system demonstrated exceptional performance in PVR identification and severity grading, with AUC values exceeding 0.957 (0.902, 1.000) on internal and external test sets, respectively. For predicting postoperative PVR risk, the system achieved AUC values above 0.827 (0.737, 0.916) on both test sets, respectively.

Conclusions

The AI-PVR Insight system has successfully achieved automatic identification, grading, and postoperative risk assessment of PVR, providing clinical physicians with support in formulating more targeted treatment plans and delivering critical insights for the effective prevention and management of PVR progression.

Subsequent intraocular lens surgery in eyes with combined versus sequential phacovitrectomy

OBJECTIVE

To determine the risk factors for subsequent intraocular lens (IOL) surgery among eyes undergoing either combined or sequential phacovitrectomy.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Adult patients undergoing phacoemulsification at 8 United Kingdom National Health Service clinical centers between July 2003 and March 2015. Patients undergoing surgery for a dropped nucleus fragment, glaucoma, or iris problems were excluded.

METHODS

The eyes were categorized into 3 groups: with previous vitrectomy, undergoing combined phacovitrectomy, and with both previous vitrectomy and current combined phacovitrectomy. These groups were compared based on preoperative ocular and systemic factors, intraoperative findings, and the subsequent need for a second IOL surgery. The Poisson model was used to calculate adjusted relative risks (aRR).

RESULTS

5,215 eyes were included: 2,124 with previous vitrectomy, 2,512 with combined phacovitrectomy, and 579 eyes with previous vitrectomy and currently combined phacovitrectomy. The risk of subsequent IOL surgery was 0.6% (reference group) in eyes with previous vitrectomy, 1.6% (aRR 2.6, CI: 1.4-5.1) in eyes with current combined phacovitrectomy, and 3.3% (aRR 3.8, CI: 1.7-8.3) in eyes with previous plus current combined phacovitrectomy. Other significant risk factors were age (aRR 0.98/year), pseudoexfoliation (aRR 6.76, CI: 2-28), zonular dialysis (aRR 10.6, CI: 4.8-24), scleral buckle in the current surgery (aRR 8.05, CI: 4-14), and the use of silicone oil (aRR 3.6, CI: 1.6-8.4) compared to no tamponade.

CONCLUSIONS

Combined phacovitrectomy was associated with a higher risk of IOL complications than sequential surgery. This information is useful for planning surgery in patients requiring both cataract and retinal surgeries.

Preoperative Intravitreal Conbercept Injection Reduced Both Angiogenic and Inflammatory Cytokines in Patients With Proliferative Diabetic Retinopathy

Aims: To investigate the impact of intravitreal injection of conbercept, a recombinant fusion protein with decoy receptors for the vascular endothelial growth factor (VEGF) family, on intraocular concentrations of angiogenic and inflammatory mediators in patients with proliferative diabetic retinopathy (PDR), analyzed its potential impact on surgical outcomes. Methods: Forty eyes from 40 patients with PDR were included in this prospective study. Patients received intravitreal injection of conbercept followed by vitrectomy or phacovitrectomy in 1 week. Aqueous humor samples were collected before and 1 week after the conbercept injection. The concentrations of angiogenic and inflammatory cytokines and chemokines were measured by flow cytometry. Follow-up clinical data were collected and analyzed. Results: Intravitreal conbercept injection significantly decreased aqueous concentrations of VEGF (325.5 (baseline) versus 22.3 pg/mL (postinjection), p < 0.0001), PlGF (39.5 versus 24.5 pg/mL, p < 0.0001), and PDGF-A (54.1 versus 47.0 pg/mL, p = 0.0016), while no impact on bFGF levels. For inflammatory mediators, the concentration of TNF-α (0.79 versus 0.45 pg/mL, p = 0.0004) and IL-8 (180.6 versus 86 pg/mL, p < 0.0001) were decreased, while IL-6 (184.1 versus 333.7 pg/mL, p = 0.0003) and IL-10 (1.1 versus 1.5 pg/mL, p = 0.0032) were increased. No significant changes in IFN-γ or MCP-1 were detected. Three months after surgery, the mean best-corrected visual acuity improved from a baseline of 1.8 ± 0.1 logMAR to 0.7 ± 0.1 logMAR (p < 0.0001), with 36 eyes (90%) achieving an improvement of visual function. Conclusions: Intravitreal conbercept injection presents dual effects of antiangiogenesis and anti-inflammation and can be served as an adjuvant treatment to vitrectomy for PDR patients.

Management, risk factors and treatment outcomes of rhegmatogenous retinal detachment associated with giant retinal tears: scoping review

BACKGROUND

Rhegmatogenous retinal detachment (RRD) is a serious condition that occurs when the retina detaches from its underlying retinal pigment epithelium. RRDs associated with giant retinal tears (GRTs) are caused by retinal tears at least 90° or one-quarter of the circumferential extent. This scoping review systematically identifies and summarizes clinical studies evaluating surgical techniques for the management of GRT-related RRDs, discusses functional and visual outcomes and the risk factors affecting treatment outcomes.

METHODS

This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Scopus, Google Scholar, and Springer Link databases were searched for relevant papers (from January 2001 to March 2023). Studies that were published in the English language and reported the risk factors, management, and treatment outcomes of GRT-related RRDs were included in the review. The outcome measures included anatomic success rates, changes in BCVA (logMAR) from baseline to the final follow-up, and adverse events.

RESULTS

A total of 11,982 articles were identified. After the title and abstract review, 71 studies were deemed eligible for full-text review. Thirty-six studies that met the eligibility criteria were included in the final review. Four surgical techniques were identified: pars plana vitrectomy (PPV), combined PPV and scleral buckling, scleral buckling alone, and pneumatic retinopexy. Various types of tamponades, including gas, silicone oil, and air, have been used. PPV was the most commonly used surgical technique in 33.1-100% of patients. Among the 20 studies that used PPV alone, 17 were associated with preoperative PVR. In addition, scleral buckling alone or in combination with PPV was reported as a treatment option in 10 studies, with 2-100% of patients experiencing scleral buckling alone and 13.6-100% experiencing combined PPV and complementary scleral buckling. Primary anatomic success (PAS) was achieved with retinal reattachment via a single operation with no residual tamponade, whereas final anatomic success (FAS) was achieved via more than one operation with no residual tamponade. Reported single surgery anatomic success (SSAS) rates range from 65.51 to 100%. The preoperative best-corrected visual acuity (BCVA) ranged from 0.067 to 2.47 logMAR, whereas the postoperative BCVA ranged from 0.08 to 2.3 logMAR. An improvement in visual acuity was observed in 29 studies. Cataracts (3.9-28.3%) were the most common postoperative complication, followed by high IOP (0.01-51.2%) and PVR (0.8-31.57%).

CONCLUSION

PPV is the most common surgical technique, and currently microincision vitrectomy surgery (MIVS) systems are commonly employed. Silicone oil is the most frequently used tamponade in RRD repair. Risk factors for GRT-related RRD include age, sex, lens status, high myopia status, proliferative vitreoretinopathy (PVR), presenting visual acuity, the extent of the GRT and retinal detachment, and macular involvement. Future research areas include guidelines to reduce variability in the reporting of surgical methodology, choice of tamponades, and reporting of functional and visual outcomes to inform the best therapeutic interventions in GRT-related RRD.

Proliferative Vitreoretinopathy: Pathophysiology and Therapeutic Approaches

Proliferative vitreoretinopathy (PVR) is a complication of retinal detachment (RD) that is characterized by the development of retinal stiffness and contractile membranes on the surface or underside of the retina. It can occur in primary RD and make repair more challenging, or it can occur following initial successful RD repair and lead to re-detachment. Though our understanding of the pathophysiology underlying PVR membrane formation has grown based on cellular and animal models, there remains no currently approved medical therapy for treatment or prevention of PVR. Though some pharmacologic agents remain under active investigation, many have failed to show consistent benefit in human trials despite promising results from preclinical models. Further research is essential not only to enhance our understanding of PVR pathophysiology but also to identify novel therapeutic strategies for treating PVR in human patients.

Vitreous Levels of Vascular Endothelial Growth Factor and Platelet-Derived Growth Factor in Patients with Proliferative Diabetic Retinopathy: A Clinical Correlation

Background: The global epidemic status of diabetic retinopathy (DR) and its burden presents an ongoing challenge to health-care systems. It is of great interest to investigate potential prognostic biomarkers of DR. Such markers could aid in detecting early stages of DR, predicting DR progression and its response to therapeutics. Herein, we investigate the prognostic value of intravitreal concentrations of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) in a DR cohort. Materials and methods: Vitreous sample acquisition was conducted at King Abdullah University Hospital (KAUH) between December 2020 and June 2022. Samples were obtained from any patient scheduled to undergo a pars plana vitrectomy (PPV) for any indication. Included patients were categorized into a DR group or a corresponding non-diabetic (ND) control group. Demographics, clinicopathological variables, standardized laboratory tests results, and optical coherence tomography (OCT) data were obtained for each included individual. Intravitreal concentrations of VEGF and PDGF were assessed using commercial enzyme-linked immunosorbent assay (ELISA). Results: A total of 80 eyes from 80 patients (DR group: n = 42 and ND control group: n = 38) were included in the analysis. The vitreous VEGF levels were significantly higher in the DR group compared to the ND control group (DR group 5744.06 ± 761.5 pg/mL versus ND control group 817.94 ± 403.1 pg/mL, p = 0.0001). In addition, the vitreous PDGF levels were also significantly higher in the DR group than those in the ND control group (DR group 4031.51 ± 410.2 pg/mL versus ND control group 2691.46 ± 821.0 pg/mL, p = 0.001). Bassline differences between test groups and clinical factors impacting VEGF and PDGF concentrations were investigated as well. Multiple regression analysis indicated PDGF as the sole independent risk factor affecting best-corrected visual acuity (BCVA) at the last follow-up visit: the higher the PDGF vitreous levels, the worst the BCVA. Conclusions: Vitreous concentrations of VEGF and PDGF are correlated with DR severity and may exhibit a possible prognostic potential value in DR. Further clinical and experimental data are warranted to confirm the observed findings and to help incorporate them into daily practice.

The Effect of Anti-Autotaxin Aptamers on the Development of Proliferative Vitreoretinopathy

This study investigated the effect of anti-autotaxin (ATX) aptamers on the development of proliferative vitreoretinopathy (PVR) in both in vivo and in vitro PVR swine models. For the in vitro study, primary retinal pigment epithelial (RPE) cells were obtained from porcine eyes and cultured for cell proliferation and migration assays. For the in vivo study, a swine PVR model was established by inducing retinal detachment and injecting cultured RPE cells (2.0 × 106). Concurrently, 1 week after RPE cell injection, the anti-ATX aptamer, RBM-006 (10 mg/mL, 0.1 mL), was injected twice into the vitreous cavity. Post-injection effects of the anti-ATX aptamer on PVR development in the in vivo swine PVR model were investigated. For the in vitro evaluation, the cultured RPE cell proliferation and migration were significantly reduced at anti-ATX aptamer concentrations of 0.5-0.05 mg and at only 0.5 mg, respectively. Intravitreal administration of the anti-ATX aptamer also prevented tractional retinal detachment caused by PVR in the in vivo PVR model. We observed that the anti-ATX aptamer, RBM-006, inhibited PVR-related RPE cell proliferation and migration in vitro and inhibited the progression of PVR in the in vivo model, suggesting that the anti-ATX aptamer may be effective in preventing PVR.

Proliferative Vitreoretinopathy: A Reappraisal

Proliferative vitreoretinopathy (PVR) remains the main cause of failure after retinal detachment (RD) surgery. Despite the development of modern technologies and sophisticated techniques for the management of RD, the growth of fibrocellular membranes within the vitreous cavity and on both sides of the retinal surface, as well as intraretinal fibrosis, can compromise surgical outcomes. Since 1983, when the term PVR was coined by the Retina Society, a lot of knowledge has been obtained about the physiopathology and risk factors of PVR, but, despite the proposal of a lot of therapeutic challenges, surgical skills seem to be the only effective way to manage PVR complications.

Non-viral gene therapy using RNA interference with PDGFR-α mediated epithelial-mesenchymal transformation for proliferative vitreoretinopathy

Fibrotic eye diseases, a series of severe oculopathy, that will destroy normal ocular refractive media and imaging structures. It is characterized by the transformation of the epithelial cells into mesenchyme cells. Proliferative vitreoretinopathy (PVR) is one of these representative diseases. In this investigation, polyethylene glycol grafted branched Polyethyleneimine (PEI-g-PEG) was used as a non-viral gene vector in gene therapy of PVR to achieve anti-fibroblastic effects in vitro and in vivo by interfering with platelet-derived growth factor alpha receptor (PDGFR-α) in the epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells. The plasmid was wrapped by electrostatic conjugation. Physical characterization of the complexes indicated that the gene complexes were successfully prepared. In vitro, cellular experiments showed excellent biocompatibility of PEI-g-PEG, efficient cellular uptake of the gene complexes, and successful expression of the corresponding fragments. Through gene silencing technique, PEI-g-PEG/PDGFR-α shRNA successfully inhibited the process of EMT in vitro. Furthermore, in vivo animal experiments suggested that this method could effectively inhibit the progression of fibroproliferative membranes of PVR. Herein, a feasible and promising clinical idea was provided for developing non-viral gene vectors and preventing fibroblastic eye diseases by RNA interference (RNAi) technology.

Use of Heavy Silicon Oil as Intraocular Tamponade for Inferior Retinal Detachment Complicated by Proliferative Vitreoretinopathy: A Multicentric Experience

INTRODUCTION

This is a multicentric study on the use of heavy silicon oil (HSO) as an intraocular tamponade for inferior retinal detachment (RD) complicated by proliferative vitreoretinopathy (PVR).

METHODS

139 eyes treated for RD with PVR were included in the study. 10 (7.2%) were affected by primary RD with inferior PVR, while 129 (92.8%) were affected by recurrent RD with inferior PVR. 102 eyes (73.9%) had received a silicon oil (SO) tamponade in a previous intervention prior to receiving HSO. Mean follow-up was 36.5 (standard deviation = 32.3) months.

RESULTS

The median interval between HSO injection and removal was 4 months (interquartile range: 3). At the time of HSO removal, the retina was attached in 120 eyes (87.6%), whereas in 17 eyes (12.4%), it had re-detached while the HSO was in situ. 32 eyes (23.2%) showed recurrent RD. A subsequent RD relapse was observed in 14.2% of cases with no RD at the time of HSO removal, and in 88.2% if an RD was present at the time of HSO removal. Advancing age showed a positive association with retinal attachment at the end of follow-up, while the risk of RD relapse at the end of the follow-up showed a significant negative association with HSO tamponade duration and with the use of SO rather than air or gas as post-HSO tamponade materials. Mean best corrected visual acuity was 1.1 logarithm of minimum angle of resolution at all follow-up time points. 56 cases (40.3%) needed treatment for elevated intraocular pressure (IOP), with which no clinically relevant variables were associated during follow-up.

CONCLUSION

HSO represents a safe and effective tamponade in cases of inferior RD with PVR. The presence of RD at the time of HSO removal is a negative prognostic factor for the development of a subsequent RD relapse. According to our findings, in cases of RD at the time of HSO removal, a short-term tamponade should definitely be avoided, in favor of SO. Special attention must be paid to the risk of IOP elevation, and patients should be closely monitored.

Outcomes of chronic macula-off retinal detachment repair

PURPOSE

There have been disparate outcomes in the few studies that have looked at anatomic success and visual acuity (VA) in chronic retinal rhegmatogenous detachment (RRD) repair. Chronic retinal detachments (RD) without a posterior vitreous detachment (PVD) occur in young myopes often secondary to an atrophic hole. These patients are often asymptomatic, and studies report good surgical anatomic results. However, chronic RD with a PVD is symptomatic but presents late due to patient compliance. This paper aims to evaluate this lesser-studied chronic macula-off RD with PVD.

METHODS

After obtaining Institutional Review Board (IRB) approval, patients who had undergone surgical intervention for all diagnosis codes of RD were identified in the Denver Health Medical Center database. Medical records were reviewed, and patients found to have open-globe injuries, tractional RD due to proliferative diabetic retinopathy, macula-on detachments, and RD due to previous ocular surgery were excluded. Similarly, patients without PVD were also excluded. A total of 37 patients with PVD-type chronic macula-off RD were thus identified and preoperative characteristics, surgical intervention, and complications were analyzed.

RESULTS

The average patient age was 53.8 years. The length of RRD duration ranged from 30 to 365 days (mean 136.7 days). Twenty-six (70.3% patients had proliferative vitreoretinopathy (PVR) grade C or greater. Initial anatomic success-defined as re-attachment after one surgery-was 54.1%. The final attachment was 94.6%. Fifteen of 37 (40.5%) of the patients had issues with drop adherence, positioning, or missing post-operative appointments.

CONCLUSION

Chronic macula-off RD with a PVD should be identified as it is associated with much lower rates of initial re-attachment. Socioeconomic factors likely are the driving factor for patients with PVD-type chronic macula-off RD to present late, struggle with positioning, and have difficulty with follow-up and drop compliance. These extended periods without treatment then lead to high rates of PVR and poor initial anatomic success. However, repair of PVD-type chronic macula-off RD should still be pursued as final anatomic success is high.

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

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

Mechanisms of Epithelial-Mesenchymal Transition and Prevention of Dispase-Induced PVR by Delivery of an Antioxidant αB Crystallin Peptide

Proliferative Vitreoretinopathy (PVR) is a refractory retinal disease whose primary pathogenesis involves the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells. At present, there is no effective treatment other than surgery for PVR. The purpose of this study was to investigate the effect of αB crystallin peptide (αBC-P) on EMT in PVR. We have previously shown that this peptide is antiapoptotic and regulates RPE redox status. Subconfluent primary human RPE (hRPE) cells were stimulated by TGFβ2 (10 ng/mL) with or without αBC-P (50 or 75 μg/mL) for 48 h and expression of EMT/mesenchymal to epithelial transition (MET) markers was determined. Mitochondrial ROS (mtROS) generation in hRPE cells treated with TGFβ2 was analyzed. The effect of TGFβ2 and αBC-P on oxidative phosphorylation (OXPHOS) and glycolysis in hRPE was studied. RPE cell migration was also assessed. A PVR-like phenotype was induced by intravitreal dispase injection in C57BL/6J mice. PVR progression and potential therapeutic efficiency of αBC-Elastin-like polypeptides (ELP) was studied using fundus photography, OCT imaging, ERG, and histologic analysis of the retina. αSMA, E-cadherin, Vimentin, Fibronectin and, RPE65, and CTGF were analyzed on Day 28. Additionally, the amount of VEGF-A in retinal cell lysates was measured. The EMT-associated αSMA, Vimentin, SNAIL and SLUG showed a significant upregulation with TGFβ2, and their expression was significantly suppressed by cotreatment with αBC-P. The MET-associated markers, E-cadherin and Sirt1, were significantly downregulated by TGFβ2 and were restored by αBC-P. Incubation of hRPE with TGFβ2 for 24 h showed a marked increase in mitochondrial ROS which was noticeably inhibited by αBC-ELP. We also showed that after TGFβ2 treatment, SMAD4 translocated to mitochondria which was blocked by αBC-ELP. Mitochondrial oxygen consumption rate increased with TGFβ2 treatment for 48 h, and αBC-P co-treatment caused a further increase in OCR. Glycolytic functions of RPE were significantly suppressed with αBC-P (75 μg/mL). In addition, αBC-P significantly inhibited the migration from TGFβ2 treatment in hRPE cells. The formation of proliferative membranes was suppressed in the αBC-ELP-treated group, as evidenced by fundus, OCT, and H&E staining in dispase-induced PVR in mice. Furthermore, ERG showed an improvement in c-wave amplitude. In addition, immunostaining showed significant suppression of αSMA and RPE65 expression. It was also observed that αBC-ELP significantly reduced the expression level of vimentin, fibronectin, and CTGF. Our findings suggest that the antioxidant αBC-P may have therapeutic potential in preventing PVR by reversing the phenotype of EMT/MET and improving the mitochondrial function in RPE cells.

Large inferior retinectomies for proliferative vitreoretinopathy in silicone oil-filled eyes

Background

To describe the anatomical and functional outcomes and late complications in patients who developed inferior proliferative vitreoretinopathy (PVR) in silicone oil-filled eyes and who required reoperation with large inferior retinectomy.

Methods

This is a single-center, retrospective, interventional case series analysis. The study involved 18 individuals with tractional retinal re-detachment due to PVR development inferiorly in eyes who had undergone prior pars plana vitrectomy and silicone oil as a tamponade. All patients included in the study underwent secondary surgery with large inferior retinectomy (from 120° to 270°) and silicone oil filling.

Results

The mean follow-up period was 44.0 ± 31.5 (± SD) months (range: 4 to 96 months. The anatomical success, defined as the complete reattachment of the retina until the last follow-up, was observed in 88.9% of the cases. The postoperative visual acuity ranged from 20/100 to hand motion at 60 cm. Only two cases (11.1%) did not achieve anatomical success at the last follow-up due to recurrent PVR and retinal re-detachment (one including hypotony). All of the patients were pseudophakic. The PVR grade, as well as the presence of PVR prior to primary surgery, showed no statistical correlation with BCVA, the extent of retinectomies, and final macular status. There was a statistically significant correlation between "Final BCVA" and "Initial BCVA" (r = 0.654) and between "Final BCVA" and "Extent of Retinectomy" (r = 0.615).

Conclusions

Reoperation in eyes filled with silicone oil may be required when PVR is developed. Secondary surgery in these cases with large inferior retinectomy and silicone oil implantation may reach good anatomical success with low rates of late complications, besides improving visual acuity. A better BCVA at the time of re-RD diagnosis and cases of retinectomies with greater extensions showed a positive correlation with better functional outcomes.

Trial registration Research Ethics Committee of the Suel Abujamra Institute reviewed and approved this study protocol (approval number, 5.404.961).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40942-022-00420-1.

Managing PVR in the Era of Small Gauge Surgery

Proliferative vitreoretinopathy (PVR) is the leading cause of failed rhegmatogenous retinal detachment (RRD) surgery. Based upon the presence of clinical features and due to associated underlying risk factors, it is classified into various grades based upon its severity and extent of involvement. Despite excellent skills, flawless techniques, and high-end technology applied in the management of RRD, PVR still occurs in 5–10% of cases. Due to the advancements in wide angle viewing systems, advance vitrectomy machines and fluidics, early identification, use of long-term heavy silicon oil tamponades, high-speed cutters, small-gauge vitrectomies, use of perfluorocarbon liquid (PFCL), and small-gauge forceps and scissors, the success rate in the management of PVR has increased leading to improved anatomical outcomes. However, functional outcomes do not correlate well with improved anatomical outcomes. Various complications occur after RRD repair that are responsible for re-retinal detachment and recurrence of PVR. This article highlights causes, risk factors, classification, grading, diagnosis, and approach to management of PVR and post-PVR surgery complications.

Proliferative diabetic retinopathy transcriptomes reveal angiogenesis, anti-angiogenic therapy escape mechanisms, fibrosis and lymphatic involvement

Proliferative diabetic retinopathy (PDR) is a sight-threatening diabetic complication in urgent need of new therapies. In this study we identify potential molecular mechanisms and target candidates in the pathogenesis of PDR fibrovascular tissue formation. We performed mRNA sequencing of RNA isolated from eleven excised fibrovascular membranes of type 1 diabetic PDR patients and two non-diabetic patients with rhegmatogenous retinal detachment with proliferative vitreoretinopathy. We determined differentially expressed genes between these groups and performed pathway and gene ontology term enrichment analyses to identify potential underlying mechanisms, pathways, and regulators. Multiple pro-angiogenic processes, including VEGFA-dependent and -independent pathways, as well as processes related to lymphatic development, epithelial to mesenchymal transition (EMT), wound healing, inflammation, fibrosis, and extracellular matrix (ECM) composition, were overrepresented in PDR. Overrepresentation of different angiogenic processes may help to explain the transient nature of the benefits that many patients receive from current intravitreal anti-angiogenic therapies, highlighting the importance of combinatorial treatments. Enrichment of genes and pathways related to lymphatic development indicates that targeting lymphatic involvement in PDR progression could have therapeutic relevance. Together with overrepresentation of EMT and fibrosis as well as differential ECM composition, these findings demonstrate the complexity of PDR fibrovascular tissue formation and provide avenues for the development of novel treatments.

The Role of Intravitreal Anti-VEGF Agents in Rabbit Eye Model of Open-Globe Injury

Purpose

To evaluate the effects of intravitreal anti-VEGF agents in a rabbit model of open-globe injury (OGI).

Methods

OGI was induced in the right eyes of 75 Belgian rabbits by making 5 mm circumferential incision placed 6 mm behind the limbus. The rabbits were divided into 4 groups: control (n = 5), OGI group (n = 40), and intravitreal Ranibizumab and Conbercept (n = 15 each). Ranibizumab or Conbercept was injected into the vitreous at 0.5 hours, 3 days, or 7 days. Vitreous fluid was collected, and levels of growth factors and cytokines were measured by enzyme-linked immunosorbent assay (ELISA). On day 28 after OGI, B scan examination and histological examination were performed to evaluate intravitreal proliferation and formation of epiretinal fibrosis.

Results

Vitreous levels of vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-β), and plasminogen activator inhibitor-1 (PAI-1) were significantly increased in rabbit eyes after OGI. Compared to eyes in OGI group, anti-VEGF treatments significantly reduced these growth factors and cytokines. Among the 7 eyes examined from each group for intravitreal proliferative changes, they were found in 7 of 7 (100%) in OGI group and were decreased by Ranibizumab and Conbercept to 5 of 7 (71.4%) and 4 of 7 (57.1%), respectively. Both Ranibizumab and Conbercept inhibited epiretinal scar formation at the wound site, with Conbercept showing the greatest effect (maximal length of scar (L), L_OGI = 503 ± 82.44 μm, L_Ranibizumab = 355 ± 43.66 μm, and L_Conbercept = 250.33 ± 36.02 μm).

Conclusion

Anti-VEGF treatments after OGI significantly attenuated the upregulation of growth factors and cytokines in the vitreous and prevented intravitreal proliferation and epiretinal scar formation and thus may protect against the development of posttraumatic complications such as proliferative vitreoretinopathy (PVR).

[Proliferative vitreoretinopathy prophylaxis : Mission (im)possible]

BACKGROUND

Proliferative vitreoretinopathy (PVR) is one of the most important complications following vitreoretinal surgery. So far, surgical strategies have been the gold standard in treatment. Pharmacological approaches for prevention and treatment of PVR are under clinical investigation and intervene in different phases of the PVR cascade.

METHODS

The relevant literature as well as own data and experience with PVR are discussed in this review article. The most important aspects of pharmacological approaches for PVR prophylaxis and treatment are explained.

RESULTS

A prophylactic use of systemic prednisone administration as an anti-inflammatory substance showed contradictory results, while there was no additional benefit for intravitreal triamcinolone. Orally administered isotretinoin also seems to be able to minimize the formation of PVR after retinal reattachment surgery, whereas there was no improvement in the success rate in established PVR. Cell proliferation inhibitors have already been extensively studied. The combined intravitreal prophylactic approach of 5‑fluorouracil and low molecular weight heparin was recently further investigated in a multicenter, placebo-controlled study and showed a positive effect in some studies. New preclinical and experimental approaches include the inhibition of growth factors, modulation of integrin activity and the induction of apoptosis.

CONCLUSION

Most clinical studies dealt with an anti-inflammatory or antiproliferative approach. So far, no pharmacological substance has been established for the treatment of PVR but there are promising approaches for prophylaxis.

Salinomycin inhibits proliferative vitreoretinopathy formation in a mouse model

Proliferative vitreoretinopathy (PVR) is a progressive disease that develops in a subset of patients who undergo surgery for retinal detachment repair, and results in significant vision loss. PVR is characterized by the migration of retinal pigment epithelial (RPE) cells into the vitreous cavity, where they undergo epithelial-to-mesenchymal transition and form contractile membranes within the vitreous and along the retina, resulting in recurrent retinal detachments. Currently, surgical intervention is the only treatment for PVR and there are no pharmacological agents that effectively inhibit or prevent PVR formation. Here, we show that a single intravitreal injection of the polyether ionophore salinomycin (SNC) effectively inhibits the formation of PVR in a mouse model with no evidence of retinal toxicity. After 4 weeks, fundus photography and optical coherence tomography (OCT) demonstrated development of mean PVR grade of 3.5 (SD: 1.3) in mouse eyes injected with RPE cells/DMSO (vehicle), compared to mean PVR grade of 1.6 (SD: 1.3) in eyes injected with RPE cells/SNC (p = 0.001). Additionally, immunohistochemistry analysis showed RPE cells/SNC treatment reduced both fibrotic (αSMA, FN1, Vim) and inflammatory (GFAP, CD3, CD20) markers compared to control RPE cells/DMSO treatment. Finally, qPCR analysis confirmed that Tgfβ, Tnfα, Mcp1 (inflammatory/cytokine markers), and Fn1, Col1a1 and Acta2 (fibrotic markers) were significantly attenuated in the RPE cells/SNC group compared to RPE/DMSO control. These results suggest that SNC is a potential pharmacologic agent for the prevention of PVR in humans and warrants further investigation.

Systems Biology Will Direct Vascular-Targeted Therapy for Obesity

Healthy adipose tissue expansion and metabolism during weight gain require coordinated angiogenesis and lymphangiogenesis. These vascular growth processes rely on the vascular endothelial growth factor (VEGF) family of ligands and receptors (VEGFRs). Several studies have shown that controlling vascular growth by regulating VEGF:VEGFR signaling can be beneficial for treating obesity; however, dysregulated angiogenesis and lymphangiogenesis are associated with several chronic tissue inflammation symptoms, including hypoxia, immune cell accumulation, and fibrosis, leading to obesity-related metabolic disorders. An ideal obesity treatment should minimize adipose tissue expansion and the advent of adverse metabolic consequences, which could be achieved by normalizing VEGF:VEGFR signaling. Toward this goal, a systematic investigation of the interdependency of vascular and metabolic systems in obesity and tools to predict personalized treatment ranges are necessary to improve patient outcomes through vascular-targeted therapies. Systems biology can identify the critical VEGF:VEGFR signaling mechanisms that can be targeted to regress adipose tissue expansion and can predict the metabolic consequences of different vascular-targeted approaches. Establishing a predictive, biologically faithful platform requires appropriate computational models and quantitative tissue-specific data. Here, we discuss the involvement of VEGF:VEGFR signaling in angiogenesis, lymphangiogenesis, adipogenesis, and macrophage specification – key mechanisms that regulate adipose tissue expansion and metabolism. We then provide useful computational approaches for simulating these mechanisms, and detail quantitative techniques for acquiring tissue-specific parameters. Systems biology, through computational models and quantitative data, will enable an accurate representation of obese adipose tissue that can be used to direct the development of vascular-targeted therapies for obesity and associated metabolic disorders.

Vitreous and Serum Concentrations of Vascular Endothelial Growth Factor and Platelet-Derived Growth Factor in Proliferative Diabetic Retinopathy

Purpose

This study aimed to investigate the concentrations of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) in vitreous and serum samples, analyze the ratio, and compare among proliferative diabetic retinopathy (PDR) subgroups.

Patients and Methods

This study included 17 eyes of patients with PDR, identified as the PDR group which was divided into three subgroups (vitreous hemorrhage [VH], VH with fibrotic tissues, and tractional retinal detachment), and five control eyes (nucleus and intraocular lens drop). Vitreous and serum samples were obtained on the same day. The VEGF-A and PDGF-AB concentrations were calculated by enzyme-linked immunosorbent assay.

Results

The VEGF-A and PDGF-AB concentrations in vitreous samples were significantly higher in the PDR group (630.72 ± 342.81 pg/mL) compared with those in the control group (153.58 ± 145.85 pg/mL); however, they were not detected in serum samples. The vitreous/serum ratio of the VEGF-A concentration in the PDR group (2.1 ± 1.8) was significantly higher compared with that in the control group (0.31 ± 0.33). The VEGF-A concentrations in vitreous samples were highest in the VH group and lowest in the VH with fibrotic tissue subgroup (mean difference 536.16 pg/mL). The vitreous VEGF-A/PDGF-AB concentration ratios were also significantly different among the PDR subgroups.

Conclusion

High concentrations of VEGF and PDGF in vitreous samples of PDR eyes indicate its local related activity in PDR pathology. There is a possibility of PDGF involvement in the pathogenesis of PDR. The VEGF/PDGF concentration ratios possibly play a significant role in the formation of fibrotic tissue in PDR.

Gremlin mediates the TGF-β-induced induction of profibrogenic genes in human retinal pigment epithelial cells

Proliferative vitreoretinopathy (PVR) is characterised by the contraction and growth of fibrotic membranes on the retina and within the vitreous body. Retinal pigment epithelial (RPE) cells, a major cellular component of the fibrotic membrane, is one of the cell types that have been previously reported to associate with PVR pathogenesis. During PVR, RPE cells undergo increased cell proliferation, migration and the secretion of extracellular matrix molecules, such as fibronectin and type I collagen. A variety of cytokines and growth factors are involved in the formation of the fibrotic membrane. Although gremlin has been reported to serve an important role in the regulation of epithelial-to-mesenchymal transition in PVR, the relationship between gremlin and the expression of profibrogenic factors in human RPE cells remains unclear. In the present study, gremlin promoted RPE cell proliferation and the expression of type I collagen and fibronectin. In addition, knocking down gremlin expression by siRNA significantly suppressed the transforming growth factor (TGF)-β1- and TGF-β2-induced expression of type I collagen and fibronectin in RPE cells. These findings suggest that gremlin may serve an important role in the development of PVR.

Blockade of MDM2 with inactive Cas9 prevents epithelial to mesenchymal transition in retinal pigment epithelial cells

Epithelial to mesenchymal transition (EMT) plays an important role in the pathogenesis of proliferative vitreoretinopathy (PVR). We aimed to demonstrate the role of mouse double minute 2 (MDM2) in transforming growth factor-beta 2 (TGF-β2)-induced EMT in human retinal pigment epithelial cells (RPEs). Immunofluorescence was used to assess MDM2 expression in epiretinal membranes (ERMs) from patients with PVR. A single guide (sg)RNA targeting the second promoter of MDM2 was cloned into a mutant lentiviral Clustered Regularly Interspaced Short Palindromic Repeats (lentiCRISPR) v2 (D10A and H840A) vector for expressing nuclease dead Cas9 (dCas9)/MDM2-sgRNA in RPEs. In addition, MDM2-sgRNA was also cloned into a pLV-sgRNA-dCas9-Kruppel associated box (KRAB) vector for expressing dCas9 fused with a transcriptional repressor KRAB/MDM2-sgRNA. TGF-β2-induced expression of MDM2 and EMT biomarkers were assessed by quantitative polymerase chain reaction (q-PCR), western blot, or immunofluorescence. Wound-healing and proliferation assays were used to evaluate the role of MDM2 in TGF-β2-induced responses in RPEs. As a result, we found that MDM2 was expressed obviously in ERMs, and that TGF-β2-induced expression of MDM2 and EMT biomarkers Fibronectin, N-cadherin and Vimentin in RPEs. Importantly, we discovered that the dCas9/MDM2-sgRNA blocked TGF-β2-induced expression of MDM2 and the EMT biomarkers without affecting their basal expression, whereas the dCas9-KRAB/MDM2-sgRNA suppressed basal MDM2 expression in RPEs. These cells could not be maintained continuously because their viability was greatly reduced. Next, we found that Nutlin-3, a small molecule blocking the interaction of MDM2 with p53, inhibited TGF-β2-induced expression of Fibronectin and N-cadherin but not Vimentin in RPEs, indicating that MDM2 functions in both p53-dependent and -independent pathways. Finally, our experimental data demonstrated that dCas9/MDM2-sgRNA suppressed TGF-β2-dependent cell proliferation and migration without disturbing the unstimulated basal activity. In conclusion, the CRISPR/dCas9 capability for blocking TGF-β2-induced expression of MDM2 and EMT biomarkers can be exploited for a therapeutic approach to PVR.

Characterisation of the inflammatory cytokine and growth factor profile in a rabbit model of proliferative vitreoretinopathy

To clarify the mechanisms and their temporal relationship in the development of proliferative vitreoretinopathy (PVR), we measured vitreous levels of pro-inflammatory cytokines and growth factors in a rabbit model of PVR. PVR was surgically induced in 11 rabbit eyes by vitrectomy, retinotomy, cryotherapy and injection of platelet-rich plasma at baseline. Severity of PVR was assessed on dilated fundal examination with indirect binocular ophthalmoscopy and graded based on the revised experimental PVR classification. Severe PVR was defined as stage 5 or worse. Vitreous concentrations of interleukin 6 (IL-6), interleukin 8 (IL-8), interleukin 1 beta (IL-1 β), tumor necrosis factor beta (TNF-β), granulocyte macrophage colony stimulating factor (GM-CSF), interferon gamma (IFN-γ), C reactive protein; (CRP), placental growth factor (PlGF), platelet derived growth factor BB (PDGF-BB), vascular endothelial growth factor (VEGF) and angiopoietin 2 (Ang-2) at weeks 2, 3 and 4 were compared to baseline and correlations between the cytokines with PVR severity were assessed. Four weeks after PVR induction, 5 eyes (45.5%) had developed severe PVR. IL-8 was raised at 2 weeks post PVR induction (1.46 ± 0.48 pg/ml vs 0.53 ± 0.25 pg/ml, p = 0.04) and remained significantly elevated at week 4 (2.6 ± 3.1 pg/ml, p = 0.03). CRP was significantly raised at week 4 (34.8 ± 12.0 pg/ml vs 13.0 ± 13.1 pg/ml, p < 0.001). Among the growth factors, PDGF-BB was the earliest to show significantly elevated levels, at 3 weeks (50.4 ± 19.0 pg/ml vs 6.2 ± 10.1 pg/ml) and remained elevated at week 4 (p = 0.002), while PlGF (11.2 ± 7.7 pg/ml vs 5.3 ± 3.8 pg/ml, p = 0.002) and Ang2 (13617.0 ± 8170.2 pg/ml vs 38593.8 ± 8313.4, p = 0.02) were significantly raised at week 4. IFN-γ (p = 0.03), PDGF-BB (p = 0.02) and VEGF (p = 0.02) were significantly associated with PVR severity. We demonstrated that inflammatory cytokines IL-6, -8, elevation post PVR induction is followed by elevated levels of fibroproliferative growth factors, Ang2, PlGF, VEGF and PDGF-BB in the development of PVR. These findings will guide future studies targeting appropriate therapeutic strategies for the treatment of PVR.

Utility of Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium for an In Vitro Model of Proliferative Vitreoretinopathy

The advent of stem cell technology, including the technology to induce pluripotency in somatic cells, and direct differentiation of stem cells into specific somatic cell types, has created an exciting new field of scientific research. Much of the work with pluripotent stem (PS) cells has been focused on the exploration and exploitation of their potential as cells/tissue replacement therapies for personalized medicine. However, PS and stem cell-derived somatic cells are also proving to be valuable tools to study disease pathology and tissue-specific responses to injury. High-throughput drug screening assays using tissue-specific injury models have the potential to identify specific and effective treatments that will promote wound healing. Retinal pigment epithelium (RPE) derived from induced pluripotent stem cells (iPS-RPE) are well characterized cells that exhibit the phenotype and functions of in vivo RPE. In addition to their role as a source of cells to replace damaged or diseased RPE, iPS-RPE provide a robust platform for in vitro drug screening to identify novel therapeutics to promote healing and repair of ocular tissues after injury. Proliferative vitreoretinopathy (PVR) is an abnormal wound healing process that occurs after retinal tears or detachments. In this chapter, the role of iPS-RPE in the development of an in vitro model of PVR is described. Comprehensive analyses of the iPS-RPE response to injury suggests that these cells provide a physiologically relevant tool to investigate the cellular mechanisms of the three phases of PVR pathology: migration, proliferation, and contraction. This in vitro model will provide valuable information regarding cellular wound healing responses specific to RPE and enable the identification of effective therapeutics.

Proliferative Vitreoretinopathy: A Review

Proliferative vitreoretinopathy (PVR) is the most common cause for failure of rhegmatogenous retinal detachment repair and is characterized by the growth and contraction of cellular membranes within the vitreous cavity and on both sides of the retinal surface as well as intraretinal fibrosis. Currently, PVR is thought to be an abnormal wound healing response that is primarily driven by inflammatory, retinal, and RPE cells. At this time, surgery is the only management option for PVR as there is no proven pharmacologic agent for the treatment or prevention of PVR. Laboratory research to better understand PVR pathophysiology and clinical trials of various agents to prevent PVR formation are ongoing.

Repair of primary RRD - comparing pars plana vitrectomy procedure with combined phacovitrectomy with standard foldable intraocular lens implantation

Background

Pars plana vitrectomy (PPV) combined with phacoemulsification and primary intraocular lens implantation can be performed for the repair of primary rhegmatogenous retinal detachment (RRD; PHACOVIT group). The safety and efficacy of this combined ophthalmic procedure on RRD surgery outcomes remain unclear compared with more conventional PPV technique alone (VITRET group). We explored the need for reoperation after primary surgical procedure in these two groups.

Methods

Retrospective, longitudinal, register-based cohort of RRD patients was operated in University Eye Clinic, Helsinki, Finland, during 2008–2014. The main outcome measure was reoperation rate during a postoperative follow-up period of 1 year due to retinal re-detachment, vitreous rehemorrhage, postoperative endophthalmitis, secondary pucker, macular hole or other reasons.

Results

We analyzed 1,690 consecutive RRD cases, out of which 1,564 patients were treated in the PPV VITRET group and 126 patients in the PHACOVIT-operated group. Risk for reoperation was 2.67 times higher in the PHACOVIT group compared to the PPV VITRET group (95% CI 1.85–3.85).

Conclusion

The reoperation rate was higher in RRD eyes operated with combined cataract surgery plus PPV, suggesting that RRD eyes should not primarily undergo combined PHACOVIT surgery.

Platelet-Derived Growth Factor Subunit B Signaling Promotes Pericyte Migration in Response to Loud Sound in the Cochlear Stria Vascularis

Normal blood supply to the cochlea is critical for hearing. Noise damages auditory sensory cells and has a marked effect on the microvasculature in the cochlear lateral wall. Pericytes in the stria vascularis (strial pericytes) are particularly vulnerable and sensitive to acoustic trauma. Exposure of NG2DsRedBAC transgenic mice (6-8 weeks old) to wide-band noise at a level of 120 dB for 3 h per day for 2 consecutive days produced a significant hearing threshold shift and caused pericytes to protrude and migrate from their normal endothelial attachment sites. The pericyte migration was associated with increased expression of platelet-derived growth factor beta (PDGF-BB). Blockade of PDGF-BB signaling with either imatinib, a potent PDGF-BB receptor (PDGFR) inhibitor, or APB5, a specific PDGFRβ blocker, significantly attenuated the pericyte migration from strial vessel walls. The PDGF-BB-mediated strial pericyte migration was further confirmed in an in vitro cell migration assay, as well as in an in vivo live animal model used in conjunction with confocal fluorescence microscopy. Pericyte migration took one of two different forms, here denoted protrusion and detachment. The protrusion is characterized by pericytes with a prominent triangular shape, or pericytes extending fine strands to neighboring capillaries. The detachment is characterized by pericyte detachment and movement away from vessels. We also found the sites of pericyte migration highly associated with regions of vascular leakage. In particular, under transmission electron microscopy (TEM), multiple vesicles at the sites of endothelial cells with loosely attached pericytes were observed. These data show that cochlear pericytes are markedly affected by acoustic trauma, causing them to display abnormal morphology. The effect of loud sound on pericytes is mediated by upregulation of PDGF-BB. Normal functioning pericytes are required for vascular stability.

The importance of pegaptanib sodium treatment for patients with vascular active vitreoretinopathy

The aim of the present study was to report the importance of pegaptanib sodium (PGSD) injection treatment for vascular active vitreoretinopathy (VAVR). A total of 82 patients with VAVR diagnosed by increasing subretinal exudation were enrolled and received a single intravitreal injection of PGSD. The efficacies of PGSD for patients with VAVR were analyzed using photography, fluorescein angiography and optical coherence tomography. The pathological changes in vascular activity, amount of exudation and visual acuity between the PGSD, and placebo group were also compared. The results demonstrated that the PGSD injection significantly decreased subretinal exudation and leakage compared with the placebo when assessed using fluorescein angiography in a 12-month follow-up. It was observed that the PGSD injection inhibited inflammatory cytokines interleukin-1β and tumor necrosis factor α for patients with VAVR compared with the placebo. Furthermore, results demonstrated that the average inflammation score and intraocular pressure was significantly decreased compared with the placebo. Visual acuity was improved from 1.3 to 0.7 in the majority of patients in the PGSD group. In conclusion, the outcomes of the present study indicate that the PGSD intravitreal injection is an efficient treatment option for patients with VAVR.

Odorant Receptor 51E2 Agonist β-ionone Regulates RPE Cell Migration and Proliferation

The odorant receptor 51E2 (OR51E2), which is well-characterized in prostate cancer cells and epidermal pigment cells, was identified for the first time as the most highly expressed OR in human fetal and adult retinal pigment epithelial (RPE) cells. Immunofluorescence staining and Western blot analysis revealed OR51E2 localization throughout the cytosol and in the plasma membrane. Additionally, immunohistochemical staining of diverse layers of the eye showed that the expression of OR51E2 is restricted to the pigment cells of the RPE and choroid. The results of Ca²⁺-imaging experiments demonstrate that activation of OR51E2 triggers a Ca²⁺ dependent signal pathway in RPE cells. Downstream signaling of OR51E2 involves the activation of adenylyl cyclase, ERK1/2 and AKT. The activity of these protein kinases likely accounts for the demonstrated increase in the migration and proliferation of RPE cells upon stimulation with the OR51E2 ligand β-ionone. These findings suggest that OR51E2 is involved in the regulation of RPE cell growth. Thus, OR51E2 represents a potential target for the treatment of proliferative disorders.

PDGFs and their receptors

The platelet-derived growth factor (PDGF)/PDGFR receptor (PDGFR) family is essential for a vast array of physiological processes such as migration and proliferation of percityes that contribute to the formation and proper function of blood vessels. While ligand-dependent de-repression of the PDGFR's kinase activity is the major mode by which the PDGFR is activated, there are additional mechanisms to activate PDGFRs. Deregulated PDGFR activity contributes to various pathological conditions, and hence the PDGF/PDGFR family members are viable therapeutic targets. An increased appreciation of which PDGFR contributes to pathology, biomarkers that indicate the amplitude and mode of activation, and receptor-specific antagonists are necessary for the development of next-generation therapies that target the PDGF/PDGFR family.

Inhibition of Proliferation and Epithelial Mesenchymal Transition in Retinal Pigment Epithelial Cells by Heavy Chain-Hyaluronan/Pentraxin 3

Proliferative vitreoretinopathy (PVR) is mediated by proliferation and epithelial mesenchymal transition (EMT) of retinal pigment epithelium (RPE). Because heavy chain-hyaluronic acid/pentraxin 3 (HC-HA/PTX3) purified from human amniotic membrane exerts anti-inflammatory and anti-scarring actions, we hypothesized that HC-HA/PTX3 could inhibit these PVR-related processes in vitro. In this study, we first optimized an ARPE-19 cell culture model to mimic PVR by defining cell density, growth factors, and cultivation time. Using this low cell density culture model and HA as a control, we tested effects of HC-HA/PTX3 on the cell viability (cytotoxicity), proliferation (EGF + FGF-2) and EMT (TGF-β1). Furthermore, we determined effects of HC-HA/PTX3 on cell migration (EGF + FGF-2 + TGF-β1) and collagen gel contraction (TGF-β1). We found both HA and HC-HA/PTX3 were not toxic to unstimulated RPE cells. Only HC-HA/PTX3 dose-dependently inhibited proliferation and EMT of stimulated RPE cells by down-regulating Wnt (β-catenin, LEF1) and TGF-β (Smad2/3, collagen type I, α-SMA) signaling, respectively. Additionally, HA and HC-HA/PTX3 inhibited migration but only HC-HA/PTX3 inhibited collagen gel contraction. These results suggest HC-HA/PTX3 is a non-toxic, potent inhibitor of proliferation and EMT of RPE in vitro, and HC-HA/PTX3’s ability to inhibit PVR formation warrants evaluation in an animal model.

MicroRNA-182 Suppresses HGF/SF-Induced Increases in Retinal Pigment Epithelial Cell Proliferation and Migration through Targeting c-Met

As increases in hepatocyte growth factor/scatter factor (HGF/SF) induce retinal pigment epithelial (RPE) migration and proliferation into the vitreous cavity and contribute to proliferative vitreoretinopathy (PVR) development, we determined if changes in miR-182 expression affect such behavioral changes. We found that miR-182 expression was less in PVR clinical samples than in primary RPE cells whereas c-Met was upregulated. Ectopic miR-182 inhibited RPE cell proliferation, cell cycle, and migration. Bioinformatic analysis identified c-Met as a miR-182 target, which was confirmed with the luciferase reporter assay. Transfection of miR-182 into RPE cells induced c-Met downregulation, which led to reduced cell proliferation and migration through declines in p-Akt formation. MiR-182 downregulation along with c-Met upregulation in PVR tissues suggest that these two opposing effects play important roles in PVR development. As ectopic miR-182 expression suppressed RPE cell proliferation and migration, strategies to selectively upregulate miR-182 expression in a clinical setting may provide a novel option to treat this disease.

Vascular Endothelial Cell Growth Factor A Acts via Platelet-Derived Growth Factor Receptor α To Promote Viability of Cells Enduring Hypoxia

Vascular endothelial cell growth factor A (VEGF) is a biologically and therapeutically important growth factor because it promotes angiogenesis in response to hypoxia, which underlies a wide variety of both physiological and pathological settings. We report here that both VEGF receptor 2 (VEGFR2)-positive and -negative cells depended on VEGF to endure hypoxia. VEGF enhanced the viability of platelet-derived growth factor receptor α (PDGFRα)-positive and VEGFR2-negative cells by enabling indirect activation of PDGFRα, thereby reducing the level of p53. We conclude that the breadth of VEGF's influence extends beyond VEGFR-positive cells and propose a plausible mechanistic explanation of this phenomenon.

Effect of Serial Intrasilicone Oil Bevacizumab Injections in Eyes With Recurrent Proliferative Vitreoretinopathy Retinal Detachment

PURPOSE

To investigate the effect of serial intrasilicone oil bevacizumab injections (1.25 mg/0.05 mL) on visual acuity (VA) and anatomic outcomes in eyes undergoing proliferative vitreoretinopathy (PVR)-related retinal detachment (RD) repair.

DESIGN

Prospective, nonrandomized, historical-control pilot study.

METHODS

setting: Tertiary care center.

STUDY POPULATION

Nondiabetic eyes undergoing pars plana vitrectomy (PPV) and silicone oil tamponade with or without scleral buckling procedure (SBP) for recurrent RD due to PVR.

INTERVENTION

Intrasilicone oil injection of 1.25 mg bevacizumab was performed intraoperatively and at postoperative months 1, 2, and 3.

OUTCOMES

Retinal reattachment rate, final VA, and rate of epiretinal membrane (ERM) formation at month 6.

RESULTS

Twenty eyes of 20 patients were enrolled and compared to a historical control group composed of 35 age- and sex-matched controls. In the study group, logMAR VA improved from mean 1.78 ± 0.43 (Snellen 20/1205) to 1.43 ± 0.70 (Snellen 20/538, P = .04), retinal reattachment was achieved in 14 of 20 eyes (70%), and ERM formation was observed in 7 of 20 eyes (35%) at 6 months. In the control group, logMAR VA improved from mean 1.50 ± 0.74 (Snellen 20/632) to 1.43 ± 0.58 (Snellen 20/538, P = .64), retinal reattachment was achieved in 25 of 35 eyes (71%), and ERM formation was observed in 7 of 35 eyes (20%) at 6 months. No significant difference in final VA (P = .96), retinal reattachment rate (P = .75), or ERM formation (P = .33) was observed between groups. No intrasilicone oil injection-related adverse events occurred.

CONCLUSIONS

Serial intrasilicone oil injections of bevacizumab did not improve retinal reattachment rate, improve final VA, or reduce ERM formation in patients undergoing PVR-related RD surgery.

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

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