Proliferative vitreoretinopathy: pathobiology, surgical management, and adjunctive treatment

Clinical therapeutics for proliferative vitreoretinopathy in retinal detachment

Proliferative vitreoretinopathy (PVR) is an abnormal and prolonged healing response to retinal injury (retinal detachment, post retinal detachment surgery) characterised by: pre/subretinal membrane formation; retinal gliosis and retinal shortening, retinal pigment epithelium cell proliferation; and increased glial (mainly Mu¨ller cells), fibroblast and inflammatory cell (macrophage, lymphocyte) activity, leading to tractional retinal holes/breaks and multiple costly eye operations suffered by patients. PVR can cause retinal re-detachment following primary surgical intervention for rhegmatogenous retinal detachment. Vitrectomy and scleral buckling surgery are the main approaches for treating PVR complications of retinal detachment. Patients require many operations to remove the scar tissue but vision results are suboptimal, and do not meet patient expectations. Over the past 40 years, this has been one of the greatest challenges for vitreoretinal surgeons and patients. Despite previous large clinical trials of multiple candidate drug therapeutics, no proven adjunctive treatment currently exists to either prevent, reduce, or treat PVR formation in retinal detachment. Both cellular proliferation and the intraocular inflammatory response are realistic targets for adjunctive treatments in PVR. The cellular components of PVR periretinal membranes (retinal pigment epithelial, glial, inflammatory and fibroblastic cells) proliferate and are thus targets for antiproliferative agents. In recent years, several new therapeutics have been tested, and we present an updated review of the clinical therapeutics for PVR in retinal detachment.

Proliferative vitreoretinopathy: a revised concept of retinal injury and response

Previous concepts for the pathogenesis of proliferative vitreoretinopathy (PVR) have focused on the central role of retinal pigment epithelium cells only, potentially contributing to the lack of clinical advances. More recent studies have demonstrated the essential role of retinal glial cells in the PVR healing response but failed to identify a consistent triggering mechanism.We propose a revised concept for the pathogenesis of PVR based on retinal injury and response. A posterior vitreous detachment (PVD) is invariably present in patients with rhegmatogenous retinal detachment and PVR. There is evidence to suggest that the shearing forces of acute PVD can cause mechanical injury to the inner retina and trigger a subsequent intraretinal glial healing response. That response is characterised by subclinical glial cell activation and proliferation that may then be amplified into full-blown PVR by coexisting pathology such as retinal breaks and detachment.Whether a PVD causes interface pathology depends on the plane of separation of the posterior vitreous and areas of increased vitreoretinal adhesions. If the vitreous separates in a plane or location that damages the inner retina then glial cell activation and proliferation are likely to develop. The severity of the subclinical inner retinal damage may then represent one of the missing links in our understanding of the pathogenesis of PVR and would explain many of the findings we encounter in clinical practice. Controlling the process of acute PVD and subsequent intraretinal response may be essential in the prevention and management of PVR.

Proliferative vitreoretinopathy: an update on the current and emerging treatment options

Proliferative vitreoretinopathy (PVR) remains the main cause of failure in retinal detachment (RD) surgery and a demanding challenge for vitreoretinal surgeons. Despite the large improvements in surgical techniques and a better understanding of PVR pathogenesis in the last years, satisfactory anatomical and visual outcomes have not been provided yet. For this reason, several different adjunctive pharmacological agents have been investigated in combination with surgery. In this review, we analyze the current and emerging adjunctive treatment options for the management of PVR and we discuss their possible clinical application and beneficial role in this subgroup of patients.

Randomised controlled trial of adjunctive triamcinolone acetonide in eyes undergoing vitreoretinal surgery following open globe trauma: The ASCOT study

BACKGROUND/AIMS

To investigate the clinical effectiveness of adjunctive triamcinolone acetonide (TA) given at the time of vitreoretinal surgery following open globe trauma (OGT).

METHODS

A phase 3, multicentre, double-masked randomised controlled trial of patients undergoing vitrectomy following OGT comparing adjunctive TA (intravitreal and subtenons) against standard care (2014-2020). The primary outcome was the proportion of patients with at least 10 Early Treatment Diabetic Retinopathy Study (ETDRS) letter improvement in corrected visual acuity (VA) at 6 months. Secondary outcomes included: change in ETDRS, retinal detachment (RD) secondary to PVR, retinal reattachment, macular reattachment, tractional RD, number of operations, hypotony, elevated intraocular pressure and quality of life.

RESULTS

280 patients were randomised over 75 months, of which 259 completed the study. 46.9% (n=61/130) of patients in the treatment group had a 10-letter improvement in VA compared with 43.4% (n=56/129) of the control group (difference 3.5% (95% CI -8.6% to 15.6%), OR=1.03 (95% CI 0.61 to 1.75), p=0.908)). Secondary outcome measures also failed to show any treatment benefit. For two of the secondary outcome measures, stable complete retinal and macular reattachment, outcomes were worse in the treatment group compared with controls, respectively, 51.6% (n=65/126) vs 64.2% (n=79/123), OR=0.59 (95% CI 0.36 to 0.99), and 54.0% (n=68/126) vs 66.7% (n=82/123), OR=0.59 (95% CI 0.35 to 0.98), for TA vs control.

CONCLUSION

The use of combined intraocular and sub-Tenons capsule TA is not recommended as an adjunct to vitrectomy surgery following OGT.

TRIAL REGISTRATION NUMBER

NCT02873026.

Intravitreal Injection of Bevacizumab for the Prevention of Postoperative Proliferative Vitreoretinopathy in High-Risk Patients Selected by Laser Flare Photometry

INTRODUCTION

To evaluate the effect of an intravitreal injection of bevacizumab at the time of rhegmatogenous retinal detachment (RRD) surgery, on postoperative proliferative vitreoretinopathy (PVR) in high-risk patients selected by laser flare photometry.

METHODS

This single-center observational retrospective cohort study included 137 consecutive patients who underwent pars plana vitrectomy and gas tamponade for primary RRD with increased aqueous flare between July 2016 and June 2021. From June 2019, an intravitreal injection of bevacizumab was administered as an adjunct to RRD repair. Patients who underwent surgery before this time and who did not receive intravitreal bevacizumab served as controls. The main outcome was the rate of retinal redetachment due to PVR.

RESULTS

The median flare value was 22.0 (16.5-36.5) pc/ms in the control group and 28.2 (19.7-41.0) pc/ms in the bevacizumab group (p = 0.063). Eyes treated with bevacizumab were more likely to have macula-off RRD (p = 0.003), grade B PVR (p = 0.038), and worse visual acuity (p = 0.004) than controls. The rate of PVR redetachment was significantly lower in the bevacizumab group (11.1%) than in the control (30.1%) (p = 0.012). This difference was more pronounced after adjusting for potential confounding factors (p = 0.005); the risk of developing PVR was 4.5-fold higher in controls (95% CI, 1.6-12.8). After adjustment, the final median visual acuity was also significantly higher in eyes treated with bevacizumab (p = 0.025).

CONCLUSION

This pilot study provides preliminary evidence that bevacizumab may reduce the risk of PVR-related recurrent RRD and improve visual outcomes in high-risk patients selected by laser flare photometry.

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.

Ligand-independent activation of platelet-derived growth factor receptor β promotes vitreous-induced contraction of retinal pigment epithelial cells

BACKGROUND

Epiretinal membranes in patients with proliferative vitreoretinopathy (PVR) consist of extracellular matrix and a number of cell types including retinal pigment epithelial (RPE) cells and fibroblasts, whose contraction causes retinal detachment. In RPE cells depletion of platelet-derived growth factor (PDGF) receptor (PDGFR)β suppresses vitreous-induced Akt activation, whereas in fibroblasts Akt activation through indirect activation of PDGFRα by growth factors outside the PDGF family (non-PDGFs) plays an essential role in experimental PVR. Whether non-PDGFs in the vitreous, however, were also able to activate PDGFRβ in RPE cells remained elusive.

METHODS

The CRISPR/Cas9 technology was utilized to edit a genomic PDGFRB locus in RPE cells derived from an epiretinal membrane (RPEM) from a patient with PVR, and a retroviral vector was used to express a truncated PDGFRβ short of a PDGF-binding domain in the RPEM cells lacking PDGFRβ. Western blot was employed to analyze expression of PDGFRβ and α-smooth muscle actin, and signaling events (p-PDGFRβ and p-Akt). Cellular assays (proliferation, migration and contraction) were also applied in this study.

RESULTS

Expression of a truncated PDGFRβ lacking a PDGF-binding domain in the RPEM cells whose PDGFRB gene has been silent using the CRISPR/Cas9 technology restores vitreous-induced Akt activation as well as cell proliferation, epithelial-mesenchymal transition, migration and contraction. In addition, we show that scavenging reactive oxygen species (ROS) with N-acetyl-cysteine and inhibiting Src family kinases (SFKs) with their specific inhibitor SU6656 blunt the vitreous-induced activation of the truncated PDGFRβ and Akt as well as the cellular events related to the PVR pathogenesis. These discoveries suggest that in RPE cells PDGFRβ can be activated indirectly by non-PDGFs in the vitreous via an intracellular pathway of ROS/SFKs to facilitate the development of PVR, thereby providing novel opportunities for PVR therapeutics.

CONCLUSION

The data shown here will improve our understanding of the mechanism by which PDGFRβ can be activated by non-PDGFs in the vitreous via an intracellular route of ROS/SFKs and provide a conceptual foundation for preventing PVR by inhibiting PDGFRβ transactivation (ligand-independent activation).

A randomised controlled trial of adjunctive triamcinolone acetonide in eyes undergoing vitreoretinal surgery for open globe trauma - the ASCOT study

Background

Eyes sustaining open globe trauma are at high risk of severe visual impairment. Proliferative vitreoretinopathy is the most common cause of retinal detachment and visual loss in eyes with open globe trauma. There is evidence from experimental studies and pilot clinical trials that the use of adjunctive steroid medication triamcinolone acetonide can reduce the incidence of proliferative vitreoretinopathy and improve outcomes of surgery for open globe trauma.

Objective

The Adjunctive Steroid Combination in Ocular Trauma or ASCOT study aimed to investigate the clinical effectiveness of adjunctive triamcinolone acetonide given at the time of vitreoretinal surgery for open globe trauma.

Design

A phase 3 multicentre double-masked randomised controlled trial randomising patients undergoing vitrectomy following open globe trauma to either adjunctive triamcinolone acetonide or standard care.

Setting

Hospital vitreoretinal surgical services dealing with open globe trauma.

Participants

Patients undergoing vitrectomy surgery who had sustained open globe trauma.

Interventions

Triamcinolone acetonide 4 mg/0.1 ml into the vitreous cavity and 40 mg/1 ml sub-Tenon's or standard vitreoretinal surgery and postoperative care.

Main outcome measures

The primary outcome was the proportion of patients with at least 10 letters of improvement in corrected visual acuity at six months. Secondary outcomes included retinal detachment secondary to proliferative vitreoretinopathy, retinal reattachment, macula reattachment, tractional retinal detachment, number of operations, hypotony, elevated intraocular pressure and quality of life. Health-related quality of life was assessed using the EuroQol Five Domain and Visual Function Questionnaire 25 questionnaires.

Results

A total of 280 patients were randomised; 129 were analysed from the control group and 130 from the treatment group. The treatment group appeared, by chance, to have more severe pathology on presentation. The primary outcome (improvement in visual acuity) and principal secondary outcome (change in visual acuity) did not demonstrate any treatment benefit for triamcinolone acetonide. The proportion of patients with improvement in visual acuity was 47% for triamcinolone acetonide and 43% for standard care (odds ratio 1.03, 95% confidence interval 0.61 to 1.75, p = 0.908); the baseline adjusted mean difference in the six-month change in visual acuity was -2.65 (95% confidence interval -9.22 to 3.92, p = 0.430) for triamcinolone acetonide relative to control. Similarly, the secondary outcome measures failed to show any treatment benefit. For two of the secondary outcome measures, stable complete retinal reattachment and stable macular retinal reattachment, outcomes for the treatment group were significantly worse for triamcinolone acetonide at the 5% level (respectively, odds ratio 0.59, 95% confidence interval 0.36 to 0.99, p = 0.044 and odds ratio 0.59, 95% confidence interval 0.35 to 0.98, p = 0.041) compared with control in favour of control. The cost of the intervention was £132 per patient. Health economics outcome measures (Early Treatment Diabetic Retinopathy Study, Visual Function Questionnaire 25 and EuroQol Five Dimensions) did not demonstrate any significant difference in quality-adjusted life-years.

Conclusions

The use of combined intraocular and sub-Tenon's capsule triamcinolone acetonide is not recommended as an adjunct to vitrectomy surgery for intraocular trauma. Secondary outcome measures are suggestive of a negative effect of the adjunct, although the treatment group appeared to have more severe pathology on presentation.

Future work

The use of alternative adjunctive medications in cases undergoing surgery for open globe trauma should be investigated. Refinement of clinical grading and case selection will enable better trail design for future studies.

Trial registration

This trial is registered as ISRCTN 30012492, EudraCT number 2014-002193-37, REC 14/LNO/1428, IRAS 156358, Local R&D registration CHAD 1031.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (12/35/64) and will be published in full in Health Technology Assessment; Vol. 27, No. 12. See the NIHR Journals Library website for further project information.

Role of m6A methylation in retinal diseases

Retinal diseases remain among the leading causes of visual impairment in developed countries, despite great efforts in prevention and early intervention. Due to the limited efficacy of current retinal therapies, novel therapeutic methods are urgently required. Over the past two decades, advances in next-generation sequencing technology have facilitated research on RNA modifications, which can elucidate the relevance of epigenetic mechanisms to disease. N6-methyladenosine (m6A), formed by methylation of adenosine at the N6-position, is the most widely studied RNA modification and plays an important role in RNA metabolism. It is dynamically regulated by writers (methyltransferases) and erasers (demethylases), and recognized by readers (m6A binding proteins). Although the discovery of m6A methylation can be traced back to the 1970s, its regulatory roles in retinal diseases are rarely appreciated. Here, we provide an overview of m6A methylation, and discuss its effects and possible mechanisms on retinal diseases, including diabetic retinopathy, age-related macular degeneration, retinoblastoma, retinitis pigmentosa, and proliferative vitreoretinopathy. Furthermore, we highlight potential agents targeting m6A methylation for retinal disease treatment and discuss the limitations and challenges of research in the field of m6A methylation.

Vitrectomy with Silicone Oil Tamponade and Single-Dose Intravitreal Methotrexate for Recurrent Retinal Detachment with Proliferative Vitreoretinopathy

Our case emphasizes the approach of a single-dose of intraoperative methotrexate (MTX) - applied directly into silicone oil - to arrest the anomalous progression of proliferative vitreoretinopathy (PVR). A 78-year-old male presented with severe vision loss secondary to a pseudophakic macula-off rhegmatogenous retinal detachment oculus sinister (OS). He was initially treated with primary pars plana vitrectomy and intraocular gas; however, the patient developed recurrent macula-off retinal detachment complicated by proliferative vitreoretinopathy OS. Subsequent management involved vitrectomy with membrane removal, silicone oil tamponade, and adjuvant intravitreal MTX. The patient had an uneventful postoperative recovery with a dramatic vision improvement after silicone oil removal OS. Here, we highlight the use of silicone oil tamponade with single-dose adjuvant MTX for the management of complex retinal detachment associated with proliferative vitreoretinopathy.

Amniotic Membrane Enhances the Characteristics and Function of Stem Cell-Derived Retinal Pigment Epithelium Sheets by Inhibiting the Epithelial-Mesenchymal Transition

Human pluripotent stem cell-derived retinal pigment epithelium (iRPE) is an attractive cell source for disease modeling and cell replacement therapy of retinal disorders with RPE defects. However, there are still challenges to develop appropriate culture conditions close to in vivo microenvironment to generate iRPE sheets, which mimic more faithfully the characteristics and functions of the human RPE cells. Here, we developed a simple, novel platform to construct authentic iRPE sheets using human amniotic membrane (hAM) as a natural scaffold. The decellularized hAM (dAM) provided a Bruch's membrane (BM)-like bioscaffold, supported the iRPE growth and enhanced the epithelial features, polarity distribution and functional features of iRPE cells. Importantly, RNA-seq analysis was performed to compare the transcriptomes of iRPE cells cultured on different substrates, which revealed the potential mechanism that dAM supported and promoted iRPE growth was the inhibition of epithelial mesenchymal transition (EMT). The tissue-engineered iRPE sheets survived and kept monolayer when transplanted into the subretinal space of rabbits. All together, our results indicate that the dAM imitating the natural BM allows for engineering authentic human RPE sheets, which will provide valuable biomaterials for disease modeling, drug screening and cell replacement therapy of retinal degenerative diseases. STATEMENT OF SIGNIFICANCE: : Engineered RPE sheets have a great advantage over RPE cell suspension for transplantation as they support RPE growth in an intact monolayer which RPE functions are dependent on. The substrates for RPE culture play a critical role to maintain the physiological functions of the RPE in stem cell therapies for patients with retinal degeneration. In this study, we constructed engineered iRPE sheets on the decellularized human amniotic membrane (dAM) scaffolds, which contributed to enhancing epithelial features, polarity distribution and functional features of iRPE. dAM exhibited the ability of anti-epithelial mesenchymal transition (EMT) to support iRPE growth. Furtherly, the results of transplanted in vivo demonstrated the feasibility of iRPE sheets in retina regenerative therapy. Engineering RPE sheets on dAM is a promising strategy to facilitate the development of iRPE replacement therapy and retinal disease modeling.

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

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

Heavy Silicone Oil as an Endotamponade in Recurrent or Complicated Retinal Detachment and Macular Hole

Objectives:

To evaluate the efficacy and safety of heavy silicone oil as an endotamponade in patients with recurrent or complicated retinal detachment and macular hole.

Materials and Methods:

Nineteen eyes of 19 patients who underwent heavy silicone oil endotamponade for different indications were included in the study and evaluated by retrospective chart review. At each visit, patients underwent detailed ophthalmological examination and anatomical and functional outcomes, silicone oil emulsification, intraocular inflammation, presence of proliferative vitreoretinopathy, preoperative and postoperative visual acuity, and postoperative complications were recorded.

Results:

The study included 19 eyes of 19 consecutive patients: 13 women (68.4%) and 6 men (31.6%). The patients’ median age was 60 years (interquartile range [IQR]: 44-70 years) and the median follow-up time was 19 months (IQR: 9-31 months). Indications for heavy silicone oil endotamponade were recurrent retinal detachment in 11 eyes (57.8%), inferior retinal detachment in 5 eyes (26.3%), inferior rhegmatogenous retinal detachment, recurrent macular hole in 2 patients (10.5%), and macular hole in 1 patient (5.2%). Median best corrected visual acuity was 2 logMAR (IQR: 1-2.6) preoperatively and 0.99 logMAR (IQR: 0.4-2) postoperatively (p<0.001). Postoperative anatomical success was achieved in all patients. Densiron 68 was used for endotamponade in 14 patients (73.7%), Densiron XTRA in 3 patients (15.8%), and AlaHeavy 1.07 in 2 patients. Heavy silicone oil emulsification was observed in only 3 patients (15.8%).

Conclusion:

Although heavy silicone oil has limitations as an endotamponade, such as intraocular pressure increase, emulsification, intraocular inflammation, and the risk of complications during removal, it is a safe and effective alternative in eyes requiring inferior retinal tamponade for indications like proliferative vitreoretinopathy and recurrent macular holes.

FEATURES AND OUTCOMES OF EYES THAT UNDERWENT SURGICAL REPAIR OF RHEGMATOGENOUS RETINAL DETACHMENTS AFTER BEING TREATED FOR ACUTE ENDOPHTHALMITIS

PURPOSE

To evaluate the etiology, clinical course, and outcomes of eyes that suffered postendophthalmitis rhegmatogenous retinal detachments.

METHODS

A retrospective, consecutive case series was conducted of patients managed at Associated Retinal Consultants P.C. from January 2013 to December 2019. Patients were identified as having had endophthalmitis by ICD-9/10 codes. Those with endophthalmitis and/or rhegmatogenous retinal detachment not managed at Associated Retinal Consultants from January were excluded.

RESULTS

Charts of 413 patients were reviewed and 19 met inclusion criteria. Incidence of rhegmatogenous retinal detachment following infectious endophthalmitis was 4.6%. The most common inciting events for endophthalmitis was intravitreal injection (9 of 19) and cataract surgery (7 of 19). Fifteen of 19 patients were treated with an injection of intravitreal antibiotics and 4 underwent immediate vitrectomy with antibiotic injection. Biopsy cultures were obtained in 18 of 19 patients and yielded positive growth in 12 (66.7%). Seventeen of the 19 eyes were operable. Final retinal reattachment rate was 88.2% (15 of 17). Mean final logMAR visual acuity was 1.58 (Snellen 20/765). Factors associated with worse final visual acuity after surgical repair included preceding intravitreal injection (P = 0.001), streptococcus species (P = 0.024), presence of proliferative vitreoretinopathy (P = 0.015), and use of silicone oil during primary rhegmatogenous retinal detachment repair (P = 0.010).

CONCLUSION

Rhegmatogenous retinal detachments following endophthalmitis occur infrequently. Although most eyes can be repaired surgically, visual outcomes are often poor, particularly in eyes that were infected with streptococcal species and had associated proliferative vitreoretinopathy.

Current Situation and Challenges in Vitreous Substitutes

Vitreo-retinal disorders constitute a significant portion of treatable ocular diseases. These pathologies often require vitreo-retinal surgery and, as a consequence, the use of vitreous substitutes. Nowadays, the vitreous substitutes that are used in clinical practice are mainly divided into gases (air, SF₆ , C₂ F₆ , C₃ F₈ ) and liquids (perfluorocarbon liquids, silicone oils, and heavy silicone oils). There are specific advantages and drawbacks to each of these, which determine their clinical indications. However, developing the ideal biomaterial for vitreous substitution continues to be one of the most important challenges in ophthalmology, and a multidisciplinary approach is required. In this sense, recent research has focused on the development of biocompatible, biodegradable, and injectable hydrogels (natural, synthetic, and smart), which also act as medium and long-term internal tamponade agents. This comprehensive review aims to cover the main characteristics and indications for use of the extensive range of vitreous substitutes that are currently used in clinical practice, before going on to describe the hydrogels that have been developed recently and which have emerged as promising biomaterials for vitreous substitution.

Eupatilin attenuates TGF-β2-induced proliferation and epithelial-mesenchymal transition of retinal pigment epithelial cells

PURPOSE

The main characteristic of proliferative vitreoretinopathy (PVR) is migration, adhesion, and epithelial-mesenchymal transition (EMT) of retinal pigment epithelial cells (RPE). Eupatilin is a naturally occurring flavone that has the potential to inhibit cell proliferation and EMT. However, its efficacy on the PVR model induced by transforming growth factor-2 (TGF-β2) is unknown. In this study, the potential effect of eupatilin on proliferation and EMT in the treatment of RPE was investigated.

METHODS

Serum starved human RPE cells (ARPE-19) were treated with 10 ng/ml TGF-β2 alone or co-treated with 25 μM eupatilin for 48 h. Quantitative real-time PCR and Western blot analysis were used to assess targets at the mRNA and protein expression level, respectively. Apoptosis and cell cycle progression was assessed by image-based cytometry. The effect of treatment on cell migration was evaluated by wound healing assay.

RESULTS

Eupatilin inhibited TGF-β2-induced RPE cell proliferation via regulating the cell cycle and inducing apoptosis. TGF-β2 upregulated mRNA expression of mesenchymal markers fibronectin and vimentin was significantly downregulated by the treatment, while the epithelial markers E-cadherin and occludin expression was upregulated. The therapy significantly suppressed TGF-β2 encouraged cell migration through downregulating the expression of transcription factors Twist, Snail, and ZEB1 induced by TGF-β2. Furthermore, eupatilin significantly inhibited the expression of MMP-1, -7, and -9, and suppressed NF-κB signalling.

CONCLUSION

These results suggest that eupatilin could inhibit the proliferation and transformation into fibroblast-like cells of RPE cells; thus the agent may be a potential therapeutic value in treating PVR.

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

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

Surgical Transplantation of Human RPE Stem Cell-Derived RPE Monolayers into Non-Human Primates with Immunosuppression

Recent trials of retinal pigment epithelium (RPE) transplantation for the treatment of disorders such as age-related macular degeneration have been promising. However, limitations of existing strategies include the uncertain survival of RPE cells delivered by cell suspension and the inherent risk of uncontrolled cell proliferation in the vitreous cavity. Human RPE stem cell-derived RPE (hRPESC-RPE) transplantation can rescue vision in a rat model of retinal dystrophy and survive in the rabbit retina for at least 1 month. The present study placed hRPESC-RPE monolayers under the macula of a non-human primate model for 3 months. The transplant was able to recover in vivo and maintained healthy photoreceptors. Importantly, there was no evidence that subretinally transplanted monolayers underwent an epithelial-mesenchymal transition. Neither gliosis in adjacent retina nor epiretinal membranes were observed. These findings suggest that hRPESC-RPE monolayers are safe and may be a useful source for RPE cell replacement therapy.

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hRPESC-RPE monolayer transplanted under macula of non-human primates

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Transplanted hRPESC-RPE recovers in vivo and maintains healthy photoreceptors

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Transplanted cells did not undergo epithelial-mesenchymal transition

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Gliosis was not observed in adjacent retina for up to at least 3 months

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.

[Melfalan in the treatment of proliferative vitreoretinopathy (experimental study)]

PURPOSE

To study of the effectiveness of the drug Melphalan as an antiproliferative agent during experimental proliferative vitreoretinopathy (PVR).

MATERIAL AND METHODS

The experimental study used data from 24 eyes of 12 Chinchilla rabbits weighing 2.5-3.0 kg, which had PVR modeled in both eyes by intravitreal injection of a culture of heterogeneous activated fibroblast cells consisting of 200,000 cells in 0.1 ml. Treatment of experimental PVR was performed 1 day after the modeling process. In the first group of animals (6 eyes), 0.02 mg of Melphalan was administered intravitreally. In the second group of animals (6 eyes), 0.005 mg of Melphalan concentrated in 0.1 ml was administered intravitreally. Left eyes in both groups remained without treatment. Animals were observed for 1 month using biomicroscopy and ophthalmoscopy. 30 days after the animals were removed from the experiment, the eyes were enucleated, fixed in 10% buffered formalin and subjected to standard histological examination. The study of paraffin sections of the eyes was performed using the microscopic system «Leica» (Leica Microsystems, Germany) with built-in digital camera at the magnification of 200-600.

RESULTS

In groups 1 and 2 of the study in the eyes of rabbits that received treatment, PVR was absent, unlike the eyes without treatment, where PVR remained. In group 1, where the dose of Melphalan was 0.02 mg in 0.1 ml, there were changes in the RPE (retinal pigment epithelium), which was regarded as a retinotoxic effect. Glial degeneration and thinning of the retina with disappearance of the photoreceptor layer (the outer nuclear and plexiform layers) resulted from the disturbance of retinal metabolism caused by RPE destruction. In group 2, structure of the retina remained more intact: isolated foci were noted with a decrease in the volume of the outer nuclear layer, shortening of rods and cones with preservation of the inner layers of the retina.

CONCLUSION

A single intravitreal injection of 0.005 mg Melphalan had a positive therapeutic antiproliferative effect on the PVR model with minimal retinotoxic changes.

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.

Proliferative vitreoretinopathy: revised concepts of pathogenesis and adjunctive treatment

Proliferative vitreoretinopathy (PVR) remains a significant challenge for vitreoretinal surgeons. Its incidence, as a complication of retinal detachment, does not appear to have altered despite improvement in surgical techniques. Extensive laboratory research has been undertaken to investigate the pathogenesis of PVR and the use of adjunctive mediations to modify the disease process. To date these studies have not resulted in improved clinical management of PVR. Previous concepts of the pathogenesis of PVR, focussing on a central role for RPE cells, may be flawed and could potentially have contributed to the lack of clinical advances. Revised clinical classifications and novel approaches to adjunctive treatment may in the future result in improved surgical outcomes.

Comparison of Chemokine CXCL-1 and Interleukin-6 Concentrations in the Subretinal Fluid and Vitreous in Rhegmatogenous Retinal Detachment

Purpose: Comparison of IL-6 and CXCL-1 concentrations and CXCL-1/IL-6 ratio correlations with clinical parameters (RRD extent, duration, and proliferative vitreoretinopathy - PVR-grade) between subretinal fluid (SRF) and vitreous during rhegmatogenous retinal detachment (RRD) complicated with PVR.Methods: A total of 71 eyes of 71 patients with primary RRD possibly complicated with PVR were included; 36 eyes treated with scleral buckling and 35 eyes with pars-plana vitrectomy. Enzyme-Linked Immuno-sorbent Assay was employed for CXCL-1/IL-6 measurement (ng/ml).Results: Correlation analysis between mean CXCL-1/IL-6 ratio and clinical parameters revealed non-significant results. CXCL-1/IL-6 ratio was significantly elevated in phakic eye vitreous. Optimum circumstances for elevated chemokine levels during RRD were considerable extent (2-3-quadrant) and duration (29-60-day) complicated with PVR C.Conclusions: SRF appears to be characterized by greater chemokine concentrations while vitreous retains several structural characteristics that may assist in investigating inflammation and improving understanding of underlying pathophysiological mechanisms during RRD complicated with PVR.

Autophagy resists EMT process to maintain retinal pigment epithelium homeostasis

Proliferative vitreoretinopathy (PVR) is the most serious fibrous complication that causes vision loss after intraocular surgery, and there is currently no effective treatment in clinical. Autophagy is an important cell biological mechanism in maintaining the homeostasis of tissues and cells, resisting the process of EMT. However, it is still unclear whether autophagy could resist intraocular fibrosis and prevent PVR progression. In this study, we investigated the expression of mesenchymal biomarkers in autophagy deficiency cells and found these proteins were increased. The mesenchymal protein transcription factor Twist can bind to autophagy related protein p62 and promote the degradation of Twist, which reduced the expression of mesenchymal markers. By constructing an EMT model of retinal pigment epithelial (RPE) cells in vitro, we found that autophagy was activated in the EMT process of RPE cells. Moreover, in autophagy deficient RPE cell line via knockdown autophagy related protein 7 (Atg7), the expression of epithelial marker claudin-1 was suppressed and the mesenchymal markers were increased, accompanied by an increase in cell migration and contractility. Importantly, RPE epithelial properties can be maintained by promoting autophagy and effectively reversing TFG-β2-induced RPE fibrosis. These observations reveal that autophagy may be an effective way to treat 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.

Crocetin inhibits PDGF-BB-induced proliferation and migration of retinal pigment epithelial cells

In proliferative vitreoretinopathy (PVR), the proliferation and migration of retinal pigment epithelial (RPE) cells are important to pathogenesis. Platelet-derived growth factor (PDGF) is an important factor in the underlying mechanism. Several studies have shown that PDGF induced the proliferation and migration effects on RPE cells in PVR. Crocetin-anantioxidant carotenoid that is abundant in saffron-has been shown to suppress the migration and proliferation of many cell types, but studies of the effects on RPE cell migration and proliferation are incomplete. Therefore, we investigated the inhibitory effect of crocetin on the proliferation and migration of ARPE-19 cells induced by PDGF-BB, an isoform of PDGF. The proliferation of cells was assessed by Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assays. The apoptosis of cells was assessed by flow cytometric analysis. The migration of RPE cells was detected by a Transwell migration assay and an in vitro scratch assay. The levels of main regulatory proteins for apoptosis and the PDGF-BB-induced signaling pathway were determined by western blot analysis. The proliferation and migration of ARPE-19 cells treated with crocetin (100-400 μM) and PDGF-BB (20 ng/ml) were significantly inhibited in a concentration- and time-dependent manner. Crocetin exhibited potent inducing effects on the apoptosis of PDGF-BB-induced ARPE-19 cells via the modulation of Bcl-2 family regulators in a concentration-dependent manner. The inhibitory effects of crocetin on PDGF-BB-induced platelet-derived growth factor receptor β (PDGFRβ) and the underlying pathways of PI3K/Akt and ERK, p38, JNK activation were identified. The results showed that crocetin is an effective inhibitor of PDGF-BB-induced proliferation and migration of ARPE-19 cell through the downregulation of regulatory signaling pathways.

Three-dimensional poly(lactic-co-glycolic acid)/silica colloidal crystal microparticles for sustained drug release and visualized monitoring

In this paper, a three-dimensional (3D) poly(lactic-co-glycolic acid) (PLGA)/silica colloidal crystal drug delivery system with sustained drug release and visualized release monitoring was developed. This system had employed silica colloidal crystal microparticles as template skeleton, PLGA as drug carrier and dexamethasone (DEX) as therapeutic agent. The fabrication of the microparticle-based system included droplet formation based-on microfluidics, silica nanoparticle self-assembly and layer-by-layer deposition of PLGA containing DEX. In 370 μm droplets, the silica colloidal nanoparticles could self-assemble orderly into microparticles with a diameter of 187 μm, featuring red structure color. During the deposition of PLGA with the drug into the voids of the template microparticles, the reflection peak red-shifted and weakened until the voids were completely filled. Owing to the gradual degradation of PLGA, the release of DEX was triggered and sustained for 4 weeks with a cumulative release of 94.9%, while the structure color of the microparticles recovered during the release process. The color change could be recognized by the naked eyes, which would benefit the non-invasive monitoring of the drug release. The in vitro cytotoxicity and long-term inhibiting proliferation were investigated on retinal pigment epithelial cells. The inhibition effect of DEX released from the microparticles showed concentration-dependence from 40 to 200 μg mL^-1 and time-dependence within 7 days. As a sustained drug delivery system with self-reporting drug release, the particles have potential applications in treatment of intraocular diseases.

Cigarette smoke-induced EGFR activation promotes epithelial mesenchymal migration of human retinal pigment epithelial cells through regulation of the FAK-mediated Syk/Src pathway

Epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells is inevitable change of age‑related macular degeneration (AMD). Smoking is a major risk factor for the development of EMT in several diseases, including lung cancer. Cigarette smoke‑induced stress promotes the production of epidermal growth factor (EGF) in RPE cells. However, the underlying signaling pathways induced by aberrant EGF receptor (EGFR) expression in cigarette smoke-exposed RPE cells remain largely unknown. In the present study, the morphological transformation and production of EMT-associated cytokines were investigated to analyze the effect of smoking on the retina. Furthermore, EGF‑treated or cigarette smoke‑exposed RPE cells, as well as the downstream targets of EGFR, were investigated to identify the key molecules involved in EMT of cigarette smoke‑stimulated RPE cells via immunoblotting. Exposure of RPE cells to cigarette smoke extract (CSE) induced secretion of VEGF and TGF‑β1, and increased the expression of EMT markers. CSE‑mediated focal adhesion kinase (FAK) activation resulted in the phosphorylation and activation of spleen associated tyrosine kinase (Syk)/Src proto‑oncogene, non‑receptor tyrosine kinase (Src), leading to migration and invasion of RPE cells. Knockdown of FAK or pharmacological inhibition of Syk/Src abrogated CSE‑mediated VEGF and TGF‑β1 production and blocked the phosphorylation of Smad2/3 in CSE‑stimulated RPE cells. Erlotinib (an EGFR inhibitor) suppressed EGF and CSE‑mediated switch from an epithelial to mesenchymal phenotype. Baicalein, an inhi-bitor of 12/15‑lipooxygenase, also efficiently suppressed CSE‑induced EMT processes by inhibiting EGFR‑associated downstream signaling transduction. The results identified a novel signaling pathway mediated by EGFR in CSE‑activated RPE cells, and suggest baicalein as a potential new therapeutic drug for CSE‑associated retinopathy.

Vitreous hemorrhage and Rhegmatogenous retinal detachment that developed after botulinum toxin injection to the extraocular muscle: case report

Background

The authors report a case of a rare complication that occurred after botulinum toxin injection to the extraocular muscle, which was easily overlooked and successfully corrected by surgery.

Case presentation

A 34-year-old female patient visited our clinic for diplopia and ocular motility disorder after removal of an epidermoid tumor of the brain. At her initial visit, her best-corrected visual acuity (BCVA) was 20/20 for both eyes. An alternate cover test showed 45 prism-diopter esotropia and 3 prism-diopter hypertropia in the right eye. Following 6 months of observation, the deviation of the strabismus did not improve, and botulinum toxin was injected into the right medial rectus (RMR). After 6 days, she visited our clinic with decreased visual acuity of her right eye. The BCVA was found to be 20/50 for her right eye. Funduscopic examination presented a retinal tear inferonasal to the optic disc with preretinal hemorrhage. Subretinal fluid nasal to the fovea was seen on optical coherence tomography (OCT). Barrier laser photocoagulation was done around the retinal tear; however, her visual acuity continued to decrease, and vitreous hemorrhage and subretinal fluid at the lesion did not improve. In addition, a newly developed epiretinal membrane was seen on OCT. An alternate cover test presented 30 prism-diopter right esotropia. 19 weeks after RMR botulinum toxin injection, she received pars plana vitrectomy, membranectomy, endolaser barrier photocoagulation, and intravitreal bevacizumab (Avastin®) injection. After 4 months, her visual acuity improved to 20/20, and only 4 prism-diopter of right hypertropia and 3 prism-diopter of exotropia were noted. Vitreous opacity and the epiretinal membrane were completely removed, as confirmed by funduscopic and examination.

Conclusions

Sudden loss of vision after injection of botulinum toxin into the extraocular muscle may suggest a serious complication, and a prompt, thorough ophthalmic examination should be performed. If improvements are not observed, rapid surgical intervention is recommended to prevent additional complications.

Electronic supplementary material

The online version of this article (10.1186/s12886-017-0649-2) contains supplementary material, which is available to authorized users.

OM-101 Decreases the Fibrotic Response Associated with Proliferative Vitreoretinopathy

Purpose

This study aimed to investigate the effect of OM-101 on the fibrotic response occurring in proliferative vitreoretinopathy (PVR) in an animal model.

Methods

Antifibrotic effect of OM-101 was investigated in vivo. As control, eight weeks old c57black mice underwent intravitreal injection with Hepes (group A) or dispase (0.3 units), to induce retinal detachment (RD) and PVR. The dispase-injected mice were randomly divided into two groups B and C (N = 25 mice); in group C, the eyes were treated with intravitreal injection of OM-101 (3 μl), and group B with PBS, as a control. After additional five days, mice were injected with the same initial treatment. Three days later, mice were euthanized, and the eyes were enucleated and processed for histological analysis.

Results

Intravitreal injection of dispase caused RD in 64% of the mice in group B, and 93% of those mice had PVR. Only 32% of mice treated with OM-101 and dispase (group C) developed RD, and only 25% of those developed PVR.

Conclusions

OM-101 was found effective in reducing the incidence of RD and PVR maintaining the normal architecture of the retina. This study suggests that OM-101 is a potentially effective and safe drug for the treatment of PVR patients.

Myofibroblast transdifferentiation: The dark force in ocular wound healing and fibrosis

Wound healing is one of the most complex biological processes to occur in life. Repair of tissue following injury involves dynamic interactions between multiple cell types, growth factors, inflammatory mediators and components of the extracellular matrix (ECM). Aberrant and uncontrolled wound healing leads to a non-functional mass of fibrotic tissue. In the eye, fibrotic disease disrupts the normally transparent ocular tissues resulting in irreversible loss of vision. A common feature in fibrotic eye disease is the transdifferentiation of cells into myofibroblasts that can occur through a process known as epithelial-mesenchymal transition (EMT). Myofibroblasts rapidly produce excessive amounts of ECM and exert tractional forces across the ECM, resulting in the distortion of tissue architecture. Transforming growth factor-beta (TGFβ) plays a major role in myofibroblast transdifferentiation and has been implicated in numerous fibrotic eye diseases including corneal opacification, pterygium, anterior subcapsular cataract, posterior capsular opacification, proliferative vitreoretinopathy, fibrovascular membrane formation associated with proliferative diabetic retinopathy, submacular fibrosis, glaucoma and orbital fibrosis. This review serves to introduce the pathological functions of the myofibroblast in fibrotic eye disease. We also highlight recent developments in elucidating the multiple signaling pathways involved in fibrogenesis that may be exploited in the development of novel anti-fibrotic therapies to reduce ocular morbidity due to scarring.

Effect of Methotrexate on an In Vitro Patient-Derived Model of Proliferative Vitreoretinopathy

Purpose

The purpose of this study was to develop a method for isolating, culturing, and characterizing cells from patient-derived membranes in proliferative vitreoretinopathy (PVR) to be used for drug testing.

Methods

PVR membranes were obtained from six patients with grade C PVR. Membrane fragments were analyzed by gross evaluation, fixed for immunohistologic studies to establish cell identity, or digested with collagenase II to obtain single cell suspensions for culture. PVR-derived primary cultures were used to examine the effects of methotrexate (MTX) on proliferation, migration, and cell death.

Results

Gross analysis of PVR membranes showed presence of pigmented cells, indicative of retinal pigment epithelial cells. Immunohistochemistry identified cells expressing α-smooth muscle actin, glial fibrillary acidic protein, Bestrophin-1, and F4/80, suggesting the presence of multiple cell types in PVR. Robust PVR primary cultures (C-PVR) were successfully obtained from human membranes, and these cells retained the expression of cell identity markers in culture. C-PVR cultures formed membranes and band-like structures in culture reminiscent of the human condition. MTX significantly reduced the proliferation and band formation of C-PVR, whereas it had no significant effect on cell migration. MTX also induced regulated cell death within C-PVR as assessed by increased expression of caspase-3/7.

Conclusions

PVR cells obtained from human membranes can be successfully isolated, cultured, and profiled in vitro. Using these primary cultures, we identified MTX as capable of significantly reducing growth and inducing cell death of PVR cells in vitro.

Biological Involvement of MicroRNAs in Proliferative Vitreoretinopathy

Even with a high surgical success rate for retinal detachment and proliferative vitreoretinopathy (PVR) supported by the robust improvement in vitrectomy surgery and its related devices, certain questions still remain for the pathogenesis and treatment of PVR. One of the important biological events in PVR is epithelial–mesenchymal transition (EMT) of the retinal pigment epithelial (RPE) cells. MicroRNAs are noncoding, small, single-strand RNAs that posttranscriptionally regulate gene expression and have essential roles in homeostasis and pathogenesis in many diseases. Recently, microRNAs also had a critical role in EMT in many tissues and cells. One main purpose of this brief review is to describe the knowledge obtained from microRNA research, especially concerning vitreoretinal diseases. In addition, the potential role of microRNAs in prevention of PVR by regulating EMT in RPE cells is described. Understanding microRNA involvement in PVR could be helpful for developing new biological markers or therapeutic targets and reducing the rate of visual disability due to PVR.

Validity of aqueous flare measurement in predicting proliferative vitreoretinopathy in patients with rhegmatogenous retinal detachment

PURPOSE

To investigate aqueous flare as a preoperative predictor for later proliferative vitreoretinopathy (PVR) development in patients with rhegmatogenous retinal detachment (RD) and to determine the validity of this measurement in patients at low clinical risk for postoperative PVR.

METHODS

This study included 100 eyes of 100 patients who underwent surgery for primary RD. Aqueous flare was determined preoperatively with a laser flare-cell meter (Kowa FM-500, Kowa Company Ltd, Tokyo, Japan). Patients were followed for at least 6 months postoperatively. Failures related to PVR were recorded for statistical analysis.

RESULTS

Twenty eyes (20%) developed PVR postoperatively. Preoperative flare values in these eyes were significantly higher than in eyes with no redetachment (48.12 ± 61.24 versus 17.74 ± 29.63 photon counts per millisecond (pc/ms), p = 0.002). The odds ratio for PVR development with flare values >15 pc/ms was 12.3 (p < 0.0001, 95% confidence interval, 3.54-42.59). Of 54 eyes at low clinical risk for postoperative PVR, five developed PVR postoperatively. Flare values were significantly higher in these eyes (25.30 ± 7.10 pc/ms) than in eyes with no redetachment (12.44 ± 10.16 pc/ms, p = 0.008). Using logistic regression, the odds ratio of PVR redetachment risk increased by the factor 1.078 per 1 pc/ms of flare value (95% CI, 1.01-1.15).

CONCLUSION

Preoperative aqueous flare is a strong predictive factor for PVR redetachment. The laser flare-cell meter provides a fast and safe tool to accurately identify patients at risk for postoperative PVR, especially when clinical examination did not predict this risk.

Slow-Release Dexamethasone in Proliferative Vitreoretinopathy: A Prospective, Randomized Controlled Clinical Trial

PURPOSE

To test the hypothesis that adjunctive slow-release dexamethasone implant (Ozurdex; Allergan Inc, Irvine, CA) can improve the outcomes of vitreoretinal surgery for established proliferative vitreoretinopathy (PVR).

DESIGN

A 2-year, single-center, prospective, participant- and surgeon-masked randomized controlled clinical trial (EudraCT No. 2011-004498-96).

PARTICIPANTS

A total of 140 patients requiring vitrectomy surgery with silicone oil for retinal detachment with established PVR (Grade C) were randomized to standard (control) or study treatment (adjunct) in a 1:1 allocation ratio.

METHODS

Intraoperatively, the adjunct group received an injection of 0.7 mg of slow-release dexamethasone (Ozurdex) at the time of (1) vitrectomy surgery and (2) silicone oil removal. The control group received standard care.

MAIN OUTCOME MEASURES

Primary outcome measure was the proportion of patients with a stable retinal reattachment with removal of silicone oil without additional vitreoretinal surgical intervention at 6 months. Secondary outcomes included (1) final visual acuity (VA) (median and Early Treatment Diabetic Retinopathy Study [ETDRS] of 55 letters or better); (2) cystoid macular edema (CMO), foveal thickness, and macular volume; (3) development of overt PVR recurrence; (4) complete and posterior retinal reattachment; (5) tractional retinal detachment; (6) hypotony/increased intraocular pressure (IOP); (7) macula pucker/epiretinal membrane; (8) cataract; and (9) quality of life.

RESULTS

All 140 patients were recruited within 25 months of study commencement; 138 patients had primary outcome data. Primary outcome assessment showed similar results in anatomic success between the 2 groups (49.3% vs. 46.3%, adjunct vs. control; odds ratio, 0.89; 95% confidence interval, 0.46-1.74; P = 0.733). Mean VA at 6 months was 38.3 ETDRS letters and 40.2 letters in the adjunct and control groups, respectively. Secondary anatomic outcomes (complete/posterior reattachment rates and PVR recurrence) were comparable between the 2 groups. At 6 months, fewer adjunct patients had CMO (42.7%) or a foveal thickness of >300 μm (47.6%) compared with controls (67.2% and 67.7%, respectively, P = 0.004, P = 0.023).

CONCLUSIONS

A slow-release dexamethasone implant did not improve the primary anatomic success rate in eyes undergoing vitrectomy surgery with silicone oil for PVR. Further clinical trials are indicated to improve anatomic and visual outcomes in these eyes, but this study suggests that there is a greater reduction in CMO observed at 6 months in vitrectomized eyes treated with slow-release dexamethasone.

Resveratrol inhibits transforming growth factor-β2-induced epithelial-to-mesenchymal transition in human retinal pigment epithelial cells by suppressing the Smad pathway

Proliferative vitreoretinopathy (PVR) is the main cause of failure following retinal detachment surgery. Transforming growth factor (TGF)-β2-induced epithelial-to-mesenchymal transition (EMT) plays an important role in the development of PVR, and EMT inhibition decreases collagen gel contraction and fibrotic membrane formation, resulting in prevention of PVR. Resveratrol is naturally found in red wine and has inhibitory effects on EMT. Resveratrol is widely used in cardioprotection, neuroprotection, chemotherapy, and antiaging therapy. The purpose of this study was to investigate the effects of resveratrol on TGF-β2-induced EMT in ARPE-19 cells in vitro. We found that resveratrol suppressed the decrease of zona occludens-1 (ZO-1) and caused an increase of alpha-smooth muscle actin expression in TGF-β2-treated ARPE-19 cells, assessed using Western blots; moreover, it also suppressed the decrease in ZO-1 and the increase of vimentin expression, observed using immunocytochemistry. Resveratrol attenuated TGF-β2-induced wound closure and cell migration in ARPE-19 cells in a scratch wound test and modified Boyden chamber assay, respectively. We also found that resveratrol reduced collagen gel contraction - assessed by collagen matrix contraction assay - and suppressed the phosphorylation of Smad2 and Smad3 in TGF-β2-treated ARPE-19 cells. These results suggest that resveratrol mediates anti-EMT effects, which could be used in the prevention of PVR.

Histopathological and ophthalmoscopic evaluation of apocynin on experimental proliferative vitreoretinopathy in rabbit eyes

The aim of the current study was to evaluate the effect of apocynin (APO) on the development of proliferative vitreoretinopathy (PVR). New Zealand-type male rabbits were randomly grouped into three as follows: (1) Sham group rabbits which were applied intraperitoneal (i.p.) vehicle without PVR; (2) PVR group rabbits where PVR was created and an i.p. vehicle was administered for 21 successive days; (3) PVR + APO group rabbits where PVR was created and i.p. APO was administered for 21 successive days. Fundus examination was conducted with an indirect ophthalmoscope before starting the experiments and at each visit afterwards. At the end of the work, the rabbits were sacrificed under high-dose anesthesia and then eye tissues were taken for histopathological analyses. In the PVR + APO group, histopathologic and ophthalmoscopic examination revealed significant decrease in PVR formation. As the result, it has been observed that APO at least partially inhibits PVR formation.

Adjunctive intraocular and peri-ocular steroid (triamcinolone acetonide) versus standard treatment in eyes undergoing vitreoretinal surgery for open globe trauma (ASCOT): study protocol for a phase III, multi-centre, double-masked randomised controlled trial

BACKGROUND

Eyes sustaining open globe trauma are at high risk of severe visual impairment. Ocular injuries which result in visual loss invariably affect the posterior segment of the eye, and prevention of visual loss involves posterior segment (vitreoretinal) surgery. Despite improvements in vitreoretinal surgical techniques, outcomes in these patients remain unsatisfactory, and development of the intraocular scarring response proliferative vitreoretinopathy is the leading cause. Proliferative vitreoretinopathy is the most common cause of recurrent retinal detachment in these eyes; it is reported to occur in up to 45 % of cases.

METHODS/DESIGN

The Adjunctive Steroid Combination in Ocular Trauma (ASCOT) trial is a multi-centre, double-masked, parallel-arm randomised controlled trial with an internal pilot designed to investigate the effectiveness and cost-effectiveness of using intravitreal and sub-Tenon's triamcinolone acetonide peri-operatively in patients undergoing vitrectomy following open globe trauma. In total, 300 eyes of 300 patients will be recruited and randomly allocated to one of two treatment groups. Both groups will receive standard surgical treatment and routine pre-operative and post-operative treatment and care. The treatment group will receive an adjunctive peri-operative steroid combination (triamcinolone acetonide) consisting of 4 mg/0.1 ml into the vitreous cavity and 40 mg/1 ml into the sub-Tenon's space. The trial incorporates a two-stage internal pilot to examine projected recruitment and retention rates. Progression criteria from the internal pilot study will enable us to determine whether to undertake the main trial. Patients and primary outcome assessors will be masked to treatment allocation. The primary outcome will be an improvement from baseline to 6 months of at least 10 on the corrected visual acuity as measured by ETDRS letter score. Secondary outcomes will be development of scarring, retinal detachment, intraocular pressure abnormalities, quality of life and public sector service use.

DISCUSSION

This is the first powered, controlled clinical trial to investigate the use of adjunctive triamcinolone in patients undergoing vitrectomy following open globe trauma.

TRIAL REGISTRATION

EudraCT2014-002193-37 . Registered on 5 September 2014. ISRCTN30012492 . Registered on 5 September 2014.

Effects of mechanical stress and vitreous samples in retinal pigment epithelial cells

In rhegmatogenous retinal detachment (RRD), scattered RPE cells from the basement membrane into the vitreous cavity undergo an epithelial mesenchymal transition (EMT) and form the intraocular fibrous membrane in response to vitreous fluid. We investigated whether exposure to vitreous samples was associated with EMT-associated signals and mesenchymal characters. Human vitreous samples were collected from patients with RRD, epiretinal membrane (ERM), or macular hole (MH). We evaluated the effects of vitreous on ARPE-19 cells in suspension cultures using poly 2-hydroxyethyl methacrylate-coated dishes and three-dimensional (3D) Matrigel cultures. We found that exposure to vitreous samples did not induce morphological changes or accelerate wound closure in monolayers. Several samples showed increased phosphorylation of Smad2 and nuclear translocation of nuclear factor-κB. Mechanical stress triggered an elevation of phosphorylation levels in Smad2. In addition, exposure to vitreous fluid increased the phosphorylation of p38 mitogen-activated protein kinase in cell suspension cultures after mechanical stress. Moreover, ARPE-19 cells showed a stellate invasive phenotype in 3D Matrigel cultures with vitreous samples. In this study, we demonstrated that mechanical stress and vitreous were associated with EMT-associated signals and invasive phenotypes in 3D cultures but not in monolayers. These results have important implications for the role of vitreous humor in the induction of EMT and intraocular fibrosis.

Proteomic Analysis of the Vitreous following Experimental Retinal Detachment in Rabbits

Purpose. The pathogenesis of rhegmatogenous retinal detachment (RRD) remains incompletely understood, with no clinically effective treatment for potentially severe complications such as photoreceptor cell death and proliferative vitreoretinopathy. Here we investigate the protein profile of the vitreous following experimental retinal detachment using a comparative proteomic based approach. Materials and Methods. Retinal detachment was created in the right eyes of six New Zealand red pigmented rabbits. Sham surgery was undertaken in five other rabbits that were used as controls. After seven days the eyes were enucleated and the vitreous was removed. The vitreous samples were evaluated with two-dimensional polyacrylamide gel electrophoresis and the differentially expressed proteins were identified with tandem mass spectrometry. Results. Ten protein spots were found to be at least twofold differentially expressed when comparing the vitreous samples of the sham and retinal detachment surgery groups. Protein spots that were upregulated in the vitreous following retinal detachment were identified as albumin fragments, and those downregulated were found to be peroxiredoxin 2, collagen-Iα1 fragment, and α-1-antiproteinase F. Conclusions. Proteomic investigation of the rabbit vitreous has identified a set of proteins that help further our understanding of the pathogenesis of rhegmatogenous retinal detachment and its complications.

Developing Extracellular Matrix Technology to Treat Retinal or Optic Nerve Injury(1,2,3)

Adult mammalian CNS neurons often degenerate after injury, leading to lost neurologic functions. In the visual system, retinal or optic nerve injury often leads to retinal ganglion cell axon degeneration and irreversible vision loss. CNS axon degeneration is increasingly linked to the innate immune response to injury, which leads to tissue-destructive inflammation and scarring. Extracellular matrix (ECM) technology can reduce inflammation, while increasing functional tissue remodeling, over scarring, in various tissues and organs, including the peripheral nervous system. However, applying ECM technology to CNS injuries has been limited and virtually unstudied in the visual system. Here we discuss advances in deriving fetal CNS-specific ECMs, like fetal porcine brain, retina, and optic nerve, and fetal non-CNS-specific ECMs, like fetal urinary bladder, and the potential for using tissue-specific ECMs to treat retinal or optic nerve injuries in two platforms. The first platform is an ECM hydrogel that can be administered as a retrobulbar, periocular, or even intraocular injection. The second platform is an ECM hydrogel and polymer "biohybrid" sheet that can be readily shaped and wrapped around a nerve. Both platforms can be tuned mechanically and biochemically to deliver factors like neurotrophins, immunotherapeutics, or stem cells. Since clinical CNS therapies often use general anti-inflammatory agents, which can reduce tissue-destructive inflammation but also suppress tissue-reparative immune system functions, tissue-specific, ECM-based devices may fill an important need by providing naturally derived, biocompatible, and highly translatable platforms that can modulate the innate immune response to promote a positive functional outcome.