Distribution of cytokine proteins within epiretinal membranes in proliferative vitreoretinopathy

Intravitreal Infliximab for the Treatment of Proliferative Vitreoretinopathy (FIXER): A Randomized Controlled Phase 2 Trial

OBJECTIVE

To study the safety and efficacy of intravitreal infliximab administered at the conclusion of pars plana vitrectomy (PPV) in the treatment of proliferative vitreoretinopathy (PVR) associated with rhegmatogenous retinal detachment (RRD).

DESIGN

Randomized controlled phase 2 clinical trial.

SUBJECTS

Patients with primary RRD and Grade C PVR, according to the updated Retina Society Classification.

METHODS

Sixty-six Patients were randomized in a 1:1 ratio to undergo PPV and silicone oil (SO) injection with or without intravitreal injection of 1 mg/0.05 mL of infliximab in the air-filled globe before SO injection at PPV conclusion. Surgeons were masked to treatment allocation until PPV conclusion.

MAIN OUTCOME MEASURES

The primary outcome measure was anatomic success (defined as complete retinal reattachment without a tamponade at 6 months post SO removal). Secondary outcome measures were final best corrected visual acuity (BCVA), single operation success rate (SOSR), rate of recurrent detachment, central macular thickness (CMT) by macular optical coherence tomography (OCT), macular function by multifocal electroretinogram and macular vascular density (VD) by OCT angiography.

RESULTS

60 eyes of 60 patients, 30 eyes in each group, completed the study. At baseline, there were no differences regarding age, gender, history of trauma, lens status, duration of RRD, BCVA, intraocular pressure (IOP), intra-ocular inflammation (IOI), detachment extent in clock hours, number/size of breaks, presence of vitreous hemorrhage, axial length, or grade/extent of PVR between both groups. For the outcome measures, 30 eyes in the infliximab group achieved anatomic success vs 29 eyes in the control group. The SOSR was higher in the infliximab group (26) vs the control (23), but this was not statistically significant (p = 0.317). Final BCVA was better in the infliximab group (mean logMAR (SD) = 0.96 (0.4), Snellen equivalent ≈ 20/180) vs the control (1.14 (0.4), Snellen equivalent ≈ 20/280) (p = 0.044). There were no differences regarding IOP, IOI, time of SO removal, macular function, CMT, or VD.

CONCLUSION

PPV with SO tamponade with or without intravitreal infliximab is effective in treating PVR-associated RRD. Infliximab may be associated with modest improvement in final visual outcomes but not anatomical outcomes.

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.

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

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

TNF-α and NF-κB signaling play a critical role in cigarette smoke-induced epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is characterized by the growth and contraction of cellular membranes within the vitreous cavity and on both surfaces of the retina, resulting in recurrent retinal detachments and poor visual outcomes. Proinflammatory cytokines like tumor necrosis factor alpha (TNFα) have been associated with PVR and the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells. Cigarette smoke is the only known modifiable risk factor for PVR, but the mechanisms are unclear. The purpose of this study was to examine the impact of cigarette smoke on the proinflammatory TNFα/NF-κB/Snail pathway in RPE cells to better understand the mechanisms through which cigarette smoke increases the risk of PVR. Human ARPE-19 cells were exposed to cigarette smoke extract (CSE), for 4 to 24-hours and TNFα, Snail, IL-6, IL-8, and α-SMA levels were analyzed by qPCR and/or Western blot. The severity of PVR formation was assessed in a murine model of PVR after intravitreal injection of ARPE-19 cells pre-treated with CSE or not. Fundus imaging, OCT imaging, and histologic analysis 4 weeks after injection were used to examine PVR severity. ARPE-19 cells exposed to CSE expressed higher levels of TNFα, SNAIL, IL6 and IL8 mRNA as well as SNAIL, Vimentin and α-SMA protein. Inhibition of TNFα and NF-κB pathways blocked the effect of CSE. In vivo, intravitreal injection of ARPE-19 cells treated with CSE resulted in more severe PVR compared to mice injected with untreated RPE cells. These studies suggest that the TNFα pathway is involved in the mechanism whereby cigarette smoke increases PVR. Further investigation into the role of TNFα/NF-κB/Snail in driving PVR and pharmacological targeting of these pathways in disease are warranted.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

MicroRNAs in the Vitreous Humor of Patients with Retinal Detachment and a Different Grading of Proliferative Vitreoretinopathy: A Pilot Study

Purpose

Although the expression of microRNAs (miRNAs) in retinal pigment epithelial (RPE) cells undergoing epithelial-mesenchymal transition (EMT) is involved in the pathogenesis of proliferative vitreoretinopathy (PVR), its expression in the vitreous of patients with primary retinal detachment (RD) and different PVR grading has not yet been investigated. We assessed the expression of miRNAs in the vitreous humor (VH) of patients diagnosed with RD and different grading of PVR.

Methods

The VH was extracted from the core of the vitreous chamber in patients who had undergone standard vitrectomy for primary RD. RNA was extracted and TaqMan Low-Density Arrays (TLDAs) were used for miRNA profiling that was performed by single TaqMan assays. A gene ontology (GO) analysis was performed on the differentially expressed miRNAs.

Results

A total of 15 eyes with RD, 3 eyes for each grade of PVR (A, B, C, and D) and 3 from unaffected individuals, were enrolled in this prospective comparative study. Twenty miRNAs were altered in the comparison among pathological groups. Interestingly, the expression of miR-143-3p, miR-224-5p, miR-361-5p, miR-452-5p, miR-486-3p, and miR-891a-5p increased with the worsening of PVR grading. We also identified 34 miRNAs showing differential expression in PVR compared to control vitreous samples. GO analysis showed that the deregulated miRNAs participate in processes previously associated with PVR pathogenesis.

Conclusions

The present pilot study suggested that dysregulated vitreal miRNAs may be considered as a biomarker of PVR and associated with the PVR-related complications in patients with RD.

Translational Relevance

The correlation between vitreal miRNAs and the pathological phenotypes are essential to identify the novel miRNA-based mechanisms underlying the PVR disease that would improve the diagnosis and treatment of the condition.

Inflammatory mediators of proliferative vitreoretinopathy: hypothesis and review

Purpose

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

Methods

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

Results

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

Conclusion

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

The effect of infliximab and octreotide on cytokine levels experimental proliferative vitreoretinopathy

Purpose: To investigate the efficiency of intravitreal octreotide, which has previously been shown to have benefits in the treatment of proliferative vitreoretinopathy (PVR), and intravitreal infliximab as a novel option in an experimental dispase-induced PVR model.Methods: A total of 28 pigmented guinea pigs were divided into four groups, and each group consisted of seven subjects. Group 1 (control) was treated with a 0.2 mL saline solution intravitreally from 1.5 mm behind the limbus. Group 2 (sham) was treated with 0.07 IU/0.1 mL dispase 0.1 mL saline solution using the same method. Group 3(infliximab) received 0.07 IU/0.1 mL dispase and 1 mg/0.1 mL infliximab, and group 4(octreotide) was treated with 0.07 IU/0.1 mL dispase and 1 mg/0.1 mL octreotide. An intravitreal injection of infliximab and octreotide was administered to groups 3 and 4 two times during the experiment. The subjects were held for a 10-week period to await for the formation of PVR. At the end of ten weeks, the eyes were enucleated, and tumour necrosis factor-alpha (TNF-α), interleukin 1(IL-1), interleukin 6 (IL-6), transforming growth factor (TGF-β), and platelet-derived growth factor (PDGF) and levels in homogenised retina tissue were measured using the enzyme linked-immuno-sorbent assay (ELISA) method.Results: Retinal TNF-α, IL-1, IL-6, and PDGF levels had significantly decreased in treatment groups compared to the sham group (p < 0.05). The decrease in the level of TGF-β was not statistically significant between the treatment and the sham groups (p > 0.05).Conclusions: Intravitreal infliximab can inhibit the development of PVR and reduce levels of cytokine, which plays an essential role in the pathogenesis of PVR. The results of our study suggest that it may be possible to identify the ideal adjuvant pharmacological drugs that are effective in preventing PVR.

Effect of etanercept on post-traumatic proliferative vitreoretinopathy

AIM

To evaluate the safety and efficacy of intravitreal etanercept in the inhibiting of proliferative vitreoretinopathy (PVR) in a model of penetrating ocular injury.

METHODS

Penetrating ocular injury on the retina of rabbit was induced, which was subsequently treated using 0.1 mL of sterile water or 0.1 mL of 12.5 mg/mL etanercept. The development of PVR was evaluated by fundus images, the B-scan, and the histopathology. The mRNA and protein expressions of tumor necrosis factor-α (TNF-α), transforming growth factor β (TGF-β) as well as connective tissue growth factor (CTGF) were examined at various time points after the etanercept injection with the reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting, respectively. The safety of etanercept was evaluated by injection of 12.5 mg/mL etanercept into a normal rabbit eye without penetrating trauma.

RESULTS

Clinical assessment and grading clearly demonstrated that the PVR formation was prevented in etanercept-treated animals, which was confirmed via fundus images, B-scan and histopathology. The RT-PCR and Western blotting showed increased mRNA and protein expression of TNF-α, TGF-β as well as CTGF in the retina of rabbits following penetrating ocular injury, and these factors were dramatically mitigated by ocular etanercept treatment. In addition, there was no adverse effect of etanercept intravitreal injection in normal eyes without penetrating trauma, it showed normal structure and histology.

CONCLUSION

The etanercept is a potential therapy for inhibiting PVR development. To assess the clinic application of the etanercept in preventing PVR, further clinical studies are required.

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.

Levels of Anti-Retinal Antibodies in Retinal Detachment and Proliferative Vitreoretinopathy

PURPOSE

The purpose of the study is to investigate the correlation between intraocular anti-retinal antibodies and clinical measurements in patients with rhegmatogenous retinal detachment (RRD) and proliferative vitreoretinopathy (PVR).

MATERIAL AND METHODS

Aqueous humor and vitreous samples were collected from patients with RRD, PVR, and from control subjects with macular hole. The levels of total protein (TP), IgG, and anti-retinal antibodies were determined with a bicinchoninic acid assay, enzyme-linked immunosorbent assay, and dot blot, respectively. Correlations between these measurements were assessed using Pearson's correlation test. Analysis of variance followed by a post-hoc test or the Student t-test was used to compare differences between groups.

RESULTS

The levels of anti-retinal antibodies and IgG were correlated with each other (P < 0.010). The IgG concentration was higher in patients with PVR than in controls in both the aqueous humor (P < 0.001) and the vitreous (P < 0.001), but not in patients with RRD. Conversely, TP levels and anti-retinal antibodies in both ocular fluids from RRD and PVR patients did not significantly differ from the controls. In a subgroup analysis, vitreal anti-retinal antibody levels were correlated with average macular thickness in the re-attached macula following surgery for macula-off RRD/PVR (P = 0.012). Furthermore, patients with post-operative cystoid macular edema had a higher level of vitreal anti-retinal antibodies than those without (P = 0.009).

CONCLUSIONS

Intravitreal anti-retinal antibodies were increased in the eyes with maculopathy after surgical intervention for RRD/PVR.

SMOKING IS A RISK FACTOR FOR PROLIFERATIVE VITREORETINOPATHY AFTER TRAUMATIC RETINAL DETACHMENT

PURPOSE

To determine the incidence of retinal redetachment due to proliferative vitreoretinopathy after open-globe trauma in smokers and nonsmokers.

METHODS

A total of 892 patients comprising 893 open-globe injuries, in whom 255 eyes were diagnosed with a retinal detachment, and 138 underwent surgical repair were analyzed in a retrospective case-control study. Time to redetachment was examined using the Kaplan-Meier method and analysis of risk factors was analyzed using Cox proportional hazards modeling.

RESULTS

Within one year after retinal detachment surgery, 47% (95% CI, 39-56%) of all 138 repaired retinas redetached because of proliferative vitreoretinopathy. Being a smoker was associated with a higher rate of detachment (adjusted hazard ratio 1.96, P = 0.01). As shown in previous studies, the presence of proliferative vitreoretinopathy at the time of surgery was also an independent risk factor for failure (adjusted hazard ratio 2.13, P = 0.005). Treatment with vitrectomy-buckle compared favorably to vitrectomy alone (adjusted hazard ratio 0.58, P = 0.04). Only 8% of eyes that redetached achieved a best-corrected visual acuity of 20/200 or better, in comparison to 44% of eyes that did not redetach (P < 0.001).

CONCLUSION

Proliferative vitreoretinopathy is a common complication after the repair of retinal detachment associated with open-globe trauma, and being a smoker is a risk factor for redetachment. Further study is needed to understand the pathophysiologic mechanisms underlying this correlation.

Müller glia as an important source of cytokines and inflammatory factors present in the gliotic retina during proliferative vitreoretinopathy

Retinal gliosis is characterized by biochemical and physiological changes that often lead to Müller glia proliferation and hypertrophy and is a feature of many neuro-degenerative and inflammatory diseases such as proliferative vitreoretinopathy (PVR). Although Müller glia are known to release inflammatory factors and cytokines, it is not clear whether cytokine production by these cells mirrors the pattern of factors present in the gliotic retina. Lysates from normal cadaveric retina and gliotic retinal specimens from patients undergoing retinectomy for treatment of PVR, the Müller cell line MIO-M1 and four human Müller glial cell preparations isolated from normal retina were examined for their expression of cytokines and inflammatory factors using semi-quantitative dot blot antibody arrays and quantitative arrays. Comparative analysis of the expression of inflammatory factors showed that in comparison with normal retina, gliotic retina exhibited greater than twofold increase in 24/102 factors examined by semiquantitative arrays, and a significant increase in 19 out of 27 factors assessed by quantitative methods (P < 0.05 to P < 0.001). It was observed that with the exception of some chemotactic factors, the majority of cytokines and inflammatory factors were produced by Müller glia in vitro and included G-CSF, MCP-1, PDGF-bb, RANTES, VEGF, and TGFβ2. These results showed that a large number of inflammatory factors expressed by Müller glia in vitro are upregulated in the gliotic retina, suggesting that targeting the production of inflammatory factors by Müller glia may constitute a valid approach to prevent neural damage during retinal gliosis and this merits further investigations.

Disease pathways in proliferative vitreoretinopathy: an ongoing challenge

Despite remarkable advances in vitreoretinal surgery, proliferative vitreoretinopathy (PVR) remains a common cause of severe visual loss or blindness. One of the critical reasons for PVR-induced blindness is tractional retinal detachment due to the formation of contractile preretinal fibrous membranes. This membrane formation is characterized by the proliferation and migration of cells and the excessive synthesis and deposition of extracellular matrix proteins. Herein we present the disease pathways of PVR, reviewing the role of both systemic and intraocular cells as well as molecular mediators. A chronological sequence of events leading to PVR is also hypothesized. Better understanding of the pathogenesis of PVR is needed in order to improve disease management. Efforts should be oriented towards greater cooperation between basic researchers and clinicians, aimed at matching the different clinical scenarios with the biological markers of the disease.

[Proliferative vitreoretinopathy: pathophysiology and clinical diagnosis]

Proliferative vitreoretinopathy (PVR) remains one of the most common causes of failed retinal detachment (RD) surgery. Many histological and clinical studies have highlighted the chain of events leading to PVR: cellular migration into the vitreous cavity, cellular differentiation, myofibroblast proliferation and activation, synthesis of extracellular matrix proteins, then contraction of preretinal tissues. The development of PVR can be explained schematically by cellular exposure to growth factors and cytokines (particularly retinal pigment epithelial cells and glial cells), in the context of break-down of the blood-retinal barrier (inflammation, choroidal detachment, iatrogenic effect of cryotherapy and surgery) and of cellular contact with the vitreous. Although the pathophysiology of PVR is now better understood, its severity remains an issue. A systematic search for preoperative PVR risk factors allows the most suitable therapeutic option to be chosen.

The prevalence and incidence of epiretinal membranes in eyes with inactive extramacular CMV retinitis

PURPOSE

To determine the prevalence and incidence of epiretinal membranes (ERM) in eyes with inactive extramacular cytomegalovirus (CMV) retinitis in patients with acquired immune deficiency syndrome (AIDS).

METHODS

A case-control report from a longitudinal multicenter observational study by the Studies of the Ocular Complications of AIDS (SOCA) Research Group. A total of 357 eyes of 270 patients with inactive CMV retinitis and 1084 eyes of 552 patients with no ocular opportunistic infection (OOI) were studied. Stereoscopic views of the posterior pole from fundus photographs were assessed at baseline and year 5 visits for the presence of macular ERM. Generalized estimating equations (GEE) logistic regression was used to compare the prevalence and 5-year incidence of ERM in eyes with and without CMV retinitis at enrollment. Crude and adjusted logistic regression was performed adjusting for possible confounders. Main outcome measures included the prevalence, incidence, estimated prevalence, and incidence odds ratios.

RESULTS

The prevalence of ERM at enrollment was 14.8% (53/357) in eyes with CMV retinitis versus 1.8% (19/1084) in eyes with no OOI. The incidence of ERM at 5 years was 18.6% (16/86) in eyes with CMV retinitis versus 2.4% (6/253) in eyes with no OOI. The crude odds ratio (OR) (95% confidence interval, CI) for prevalence was 9.8 (5.5-17.5) (P < 0.01). The crude OR (95% CI) for incidence was 9.4 (3.2-27.9) (P < 0.01).

CONCLUSIONS

A history of extramacular CMV retinitis is associated with increased prevalence and incidence of ERM formation compared to what is seen in eyes without ocular opportunistic infections in AIDS patients.

A TGF-β receptor 1 inhibitor for prevention of proliferative vitreoretinopathy

This study evaluates the use of the TGF-β receptor 1 inhibitor LY-364947 (LY) to prevent proliferative vitreoretinopathy (PVR). For the in vitro experiments Human Tenon's Fibroblasts (HTFs) and retinal pigment epithelial (RPE) cells were treated with different concentrations of LY to determine HTF proliferation and RPE transdifferentiation. For in vivo testing 30 rabbits underwent a PVR trauma model. The animals received different concentrations of intravitreally injected LY, with or without vitrectomy. LY treatment reduced HTF proliferation and RPE transdifferentiation in vitro. In vivo intravitreal injection of LY prevented PVR development significantly. This positive effect was also present when LY injection was combined with vitrectomy. Intravitreal injection of LY prevented tractional retinal detachment in 14 out of 15 animals. In conclusion, treatment with the TGF-β receptor 1 inhibitor LY reduces HTF proliferation and RPE transdifferentiation in vitro and prevents proliferative vitreoretinopathy and subsequent tractional retinal detachment in vivo.

Mechanisms of inflammation in proliferative vitreoretinopathy: from bench to bedside

Proliferative vitreoretinopathy (PVR) is a vision-threatening disease and a common complication of surgery to correct rhegmatogenous retinal detachment (RRD). Several models of the pathogenesis of this disease have been described with some of these models focusing on the role of inflammatory cells and other models focusing on the role of growth factors and cytokines in the vitreous which come into contact with intraretinal and retinal pigment epithelial cells. New experiments have shed light on the pathogenesis of PVR and offer promising avenues for clinical intervention before PVR develops. One such target is the indirect pathway of activation of platelet-derived growth factor receptor alpha (PDGRα), which plays an important role in PVR. Clinical trials assessing the efficacy of 5-fluorouracil (5-FU) and low-molecular-weight heparin (LMWH), daunorubicin, and 13-cis-retinoic acid, among other therapies, have yielded mixed results. Here we review inflammatory and other mechanisms involved in the pathogenesis of PVR, we highlight important clinical trials, and we discuss how findings at the bench have the potential to be translated to the bedside.

Interleukin-6 and matrix metalloproteinase expression in the subretinal fluid during proliferative vitreoretinopathy: correlation with extent, duration of RRD and PVR grade

PURPOSE

To investigate interleukin (IL)-6 protein levels in the subretinal fluid (SRF) of patients with rhegmatogenous retinal detachment (RRD) complicated by proliferative vitreoretinopathy (PVR); to correlate the IL-6 levels with matrix metalloproteinases (MMP)-1, -2, -3, -8, -9 and tissue inhibitor of metalloproteinases (TIMP)-1 with respect to RRD extent, duration and PVR grade.

METHODS

Thirty-one SRF samples from 31 eyes of 31 patients with RRD complicated with PVR and five SRF samples from five eyes of five patients suffering from RRD not complicated with PVR were collected during treatment by scleral buckling. Enzyme-Linked Immunosorbent Assay was employed for the measurement of IL-6, MMP-1, -3, -8 and TIMP-1 levels while the enzymatic activity of MMP-2 and MMP-9 was assessed by gelatin zymography.

RESULTS

Protein levels of IL-6 (p=0.050), MMP-1 (p=0.001), MMP-3 (p=0.005), MMP-8 (p=0.003), TIMP-1 (p=0.001) as well as enzymatic activity of proMMP-2 (p=0.001), MMP-2 (p=0.023) and MMP-9 (p=0.015), were significantly higher in the SRF of PVR patients compared to controls. IL-6 levels correlated significantly with TIMP-1 (r=0.528, p=0.035). Regarding clinical parameters of the detachment, IL-6 levels correlated with RRD extent (r=0.592, p=0.016), but not with RRD duration (p=0.857) and PVR grade (p=0.594). Regression analysis revealed positive correlations between IL-6 and MMP-2.

CONCLUSIONS

There was a significant correlation between IL-6 and TIMP-1 levels in the SRF of PVR patients. The findings of this study are in agreement with relevant studies concerning IL-6 involvement in the modulation of MMP expression and are indicative of IL-6 and MMP activity during PVR, mainly that of MMP-2 and TIMP-1.

The role of Bcl-xL in mouse RPE cell survival

PURPOSE. Retinal pigment epithelial (RPE) cell survival plays a critical role in normal physiology and in retinal diseases, such as age-related macular degeneration (AMD) and proliferative vitreoretinopathy (PVR). We have previously demonstrated that Bcl-x(L) is an important cell survival protein in human RPE (hRPE) cells. Herein, we determined the role of Bcl-x(L) as a survival protein in mouse RPE (mRPE) cells. METHODS. Survival factor gene expression and Bcl-x(L) protein distribution were determined using qRT-PCR and immunohistochemistry, respectively. Cultured mRPE cells were transfected with two modified 2'-O-methoxyethoxy antisense oligonucleotides (ASOs): Bcl-x(L)-mismatched control and Bcl-x(L)-specific. Bcl-x(L) protein levels were analyzed using Western blot. To determine the effects of survival factor regulation in mRPE cells, cultured cells were treated for 24 hours with mouse TNF-α, human IL-1β, and human TNF-α. RESULTS. Bcl-x(L) was the most highly expressed survival factor in both mouse eyecup and cultured mRPE cells, whereas Bax was the most highly expressed antisurvival factor. Bcl-x(L) was expressed in the RPE layer, and the distribution among the retinal layers was similar to that observed in human eyecups. IL-1β and TNF-α had minimal effect on Bcl-x(L) and Bax expression and strongly upregulated Traf-1. Transfection with Bcl-x(L)-specific ASO resulted in markedly diminished Bcl-x(L) gene expression, Bcl-x(L) protein levels, and cell number. CONCLUSIONS. Bcl-x(L) is the most highly expressed survival gene in mRPE cells and is essential for mRPE cell survival. Our data suggest that mouse tissue is an appropriate model for investigations of RPE survival factor genes.

Interleukin-6 and the matrix metalloproteinase response in the vitreous during proliferative vitreoretinopathy

PURPOSE

To investigate the levels of IL-6 in the vitreous of patients with RRD complicated with PVR and correlate the IL-6 levels with matrix metalloproteinase (MMP)-1,-2,-3,-8,-9 and tissue inhibitor of metalloproteinases (TIMP)-1 with respect to RRD extent, duration and PVR grade.

DESIGN

Cohort study.

PARTICIPANTS

Twenty-eight vitreous samples from 28 eyes of 28 patients with RRD complicated with PVR.

METHODS

Institutional study. Twenty-eight vitreous samples from 28 eyes of 28 patients with RRD complicated with PVR were collected during pars plana vitrectomy (PPV) and were compared to vitreous control samples. IL-6, MMP-1,-3,-8 and TIMP-1 levels were measured using ELISA while enzymatic activity of MMP-2, and -9 was determined employing gelatin zymography.

RESULTS

Protein IL-6 (p=0.030), MMP-1 (p=0.003), MMP-3 (p=0.003), TIMP-1 (p=0.001) levels as well as enzymatic activity of proMMP-9 (p=0.013), MMP-9 (p=0.017) and proMMP-2 (p=0.010), were significantly increased in PVR patients as compared to controls. IL-6 levels correlated with MMP-1 (p=0.002), proMMP-2 (p=0.006), MMP-3 (p=0.001) and TIMP-1 (p=0.006). Regression analysis revealed positive correlations between IL-6 and all MMPs and TIMP-1.

CONCLUSIONS

Taking into account the previously established effect of interleukins in MMP activity, the findings of this study suggest a role of IL-6 in MMP stimulation during PVR development.

A strong genetic association between the tumor necrosis factor locus and proliferative vitreoretinopathy: the retina 4 project

OBJECTIVE

To assess the genetic contribution to proliferative vitreoretinopathy (PVR) and report the strong association observed in the tumor necrosis factor (TNF) locus.

DESIGN

As a component of The Retina 4 Project, a case-controlled, candidate gene association study in the TNF locus was conducted.

PARTICIPANTS AND CONTROLS

Blood from 450 patients with (138 cases) and without (312 controls) post-rhegmatogenous retinal detachment (RD) PVR was genotyped to determine polymorphisms located in the TNFα gene.

METHODS

Single nucleotide polymorphisms (SNPs) with correlation coefficients of ≥ 0.8 and a minor allelic frequency of ≥ 10% were studied. Functional SNPs or SNPs previously described in association with other inflammatory diseases were also added for analysis. The SNPlex Genotyping System (Applied Biosystems, Foster City, CA) was used for genotyping. Single nucleotide polymorphism and haplotype analyses were performed. Bioinformatic tools were used to evaluate those SNPs that were significantly associated.

MAIN OUTCOME MEASURES

Single and haplotypic significant associations with PVR.

RESULTS

A total of 11 common tag SNPs in the following genes were analyzed: lymphotoxin alpha (LTA), TNFα, leukocyte-specific transcript 1 (LST1), and the activating natural killer receptor p30 (NCR3). After permutation, there was a significant association in the non-synonymous polymorphism rs2229094(T→C) in the LTA gene (P = 0.0283), which encodes a cysteine to arginine change in the signal peptide. This marker was also present in all significant haplotypic associations and was not observed in any nonsignificant associations. When this SNP was analyzed using bioinformatic tools, the hydropathy profile changed, as well as the transmembrane region and the splicing site predictions.

CONCLUSIONS

The strong association found in the rs2229094(T→C) of the LTA gene may indicate an important role of this polymorphism in the development of PVR. If supported in extended studies, the rs2229094(T→C) may have significant implications regarding the genetic risk of the retinal repairing process.

Proliferative vitreoretinopathy: pathobiology and therapeutic targets

The cell biology and molecular mediators of proliferative vitreoretinopathy continue to be elucidated. The purpose of this review is to summarize contemporary findings in the visual and neurosciences relevant to the pathophysiology of proliferative vitreoretinopathy, with an emphasis on the biologic mediators that represent potential therapeutic targets.

Involvement of Müller glial cells in epiretinal membrane formation

BACKGROUND

Proliferative retinopathies are considered to represent maladapted retinal wound repair processes driven by growth factor- and cytokine-induced overstimulation of proliferation, migration, extracellular matrix production and contraction of retinal cells. The formation of neovascular membranes represents an attempt to reoxygenize non-perfused retinal areas. Müller glial cells play a crucial role in the pathogenesis of proliferative retinopathies. This review summarizes the present knowledge regarding the role of Müller cells in periretinal membrane formation, especially in the early steps of epiretinal membrane formation, which involve an interaction of inflammatory and glial cells, and gives a survey of the factors which are suggested to be implicated in the induction of Müller cell gliosis and proliferation.

CONCLUSIONS

Alterations in the membrane conductance of Müller cells suggest that Müller cells may alter their phenotype into progenitor-like cells in the course of proliferative retinopathies; transdifferentiated Müller cells may have great impact for the development of new cell-based therapies.

Proteome Profiling of Vitreoretinal Diseases by Cluster Analysis

Vitreous samples collected in retinopathic surgeries have diverse properties, making proteomics analysis difficult. We report a cluster analysis to evade this difficulty. Vitreous and subretinal fluid samples were collected from 60 patients during surgical operation of non-proliferative diabetic retinopathy, proliferative diabetic retinopathy, proliferative vitreoretinopathy, and rhegmatogenous retinal detachment. For controls we collected vitreous fluid from patients of idiopathic macular hole, epiretinal, and from a healthy postmortem donor. Proteins from these samples were subjected to quantitative proteomics using two-dimensional gel electrophoresis. We selected 105 proteins robustly expressed among ca 400 protein spots and subjected them to permutation test. By using permutation test analysis we observed unique variations in the expression of some of these proteins in vitreoretinal diseases when compared to the control and to each other: 1) the levels of inflammation-associate proteins such as AAT, APOA4, ALB, and TF were significantly higher in all four types of vitreoretinal diseases, and 2) each vitreoretinal disease elevates a unique set of proteins which can be interpreted based on the pathology of retinopathy. Our protocol will be effective for the study of protein expression in other types of clinical samples of diverse property.

Obestatin-mediated proliferation of human retinal pigment epithelial cells: regulatory mechanisms

In this work, we have evaluated the effect of the new discovered peptide obestatin on cell proliferation in primary cultures of human retinal epithelial cells (hRPE cells). The results showed that this peptide induced, in a dose-dependent manner, cell proliferation by MEK/ERK 1/2 phosphorylation. A sequential analysis of the obestatin transmembrane signaling pathway showed that the ERK 1/2 activity is partially blocked after preincubation of the cells with pertussis toxin (PTX), as well as by wortmannin (an inhibitor of PI3K), claphostin C (an inhibitor of PKC), and PP2 (which inhibits the non receptor tyrosine kinase Src). Upon administration of obestatin, the intracellular levels of phospho-PKCepsilon-, theta-, and micro-isoenzymes rise with different time courses, from which PKCepsilon might be responsible for ERK 1/2 response. Based on the experimental data, a signaling pathway involving the consecutive activation of Gi, PI3K, novel PKC (probably PKCepsilon), and Src for ERK 1/2 activation is proposed. These results incorporate a new mitogenic factor to the group of factors that regulate proliferation of hRPE cells.

Glucosamine sulfate inhibits leukocyte adhesion in response to cytokine stimulation of retinal pigment epithelial cells in vitro

Glucosamine is an amine-containing sugar that exhibits immunosuppressive effects in vitro and in vivo, although its mechanism of action is unknown. We investigated whether glucosamine sulfate (GS) modulates the proinflammatory cytokine interleukin (IL)-1beta-induced expression and production of intercellular adhesion molecule (ICAM)-1, the mechanism responsible for this effect, and whether GS inhibits leukocyte adhesion to the monolayer of retinal pigment epithelial (RPE) cells stimulated with various cytokines. We used flow cytometry and an ARPE-19 cell model to determine the effect of GS on the production of ICAM-1 in response to IL-1beta, IL-6, tumor necrosis factor (TNF)-alpha plus IL-1beta, TNF-alpha plus IL-6, and TNF-alpha plus interferon (IFN)-gamma. We also used semiquantitative RT-PCR to determine the effect of GS on IL-1beta-induced expression of the ICAM-1 gene, and immunocytochemistry and western blotting to measure the effect of GS on the activation and nuclear translocation of the nuclear factor NF-kappaB and the degradation of cytoplasmic IkappaB. The functionality of GS-modulated ICAM-1 on leukocyte adhesion was demonstrated in an RPE cell-neutrophil adherence assay. IL-1beta increased the expression of ICAM-1 at the mRNA and protein levels in ARPE-19 cells. GS downregulated the production of ICAM-1 induced by IL-1beta, IL-6, TNF-alpha, and IFN-gamma at the protein level in a dose-dependent manner. GS also inhibited the nuclear translocation of NF-kappaB subunit p65 and partially prevented the degradation of cytoplasmic IkappaB in IL-1beta-stimulated ARPE-19 cells. GS significantly decreased the number of neutrophils adhering to the RPE monolayer in response to cytokines IL-1beta, IL-6, TNF-alpha, and IFN-gamma. GS inhibits the expression of the ICAM-1 gene in ARPE-19 cells stimulated with IL-1beta by blocking NF-kappaB subunit p65 translocation and by partially preventing IkappaB degradation. GS also decreases leukocyte adhesion to the monolayer of ARPE-19 cells stimulated with various cytokines by decreasing ICAM-1 production. Our study demonstrates a potentially important property of GS in reducing ICAM-1-mediated inflammatory mechanisms in the eye.

Upregulation of RAGE and its ligands in proliferative retinal disease

We sought to study the presence of the receptor for advanced glycation endproducts (RAGE) and its ligands, advanced glycation endproducts (AGEs), S100/calgranulins and amphoterin (high mobility group box 1 protein; HMGB1), in the vitreous cavity and epiretinal membranes (ERMs) of eyes of patients with proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). Undiluted vitreous specimens were collected from 30 eyes of 30 patients undergoing pars plana vitrectomy for repair of retinal detachment (RD) secondary to PDR (n = 15) or PVR (n = 15). The vitreous samples obtained from 10 eyes undergoing macular hole repair were used as controls. Epiretinal membranes were obtained from eight eyes with PDR and from 10 eyes with PVR. The levels of AGEs in the vitreous were measured using ELISA. The vitreous levels of soluble RAGE (sRAGE), S100/calgranulins and amphoterin were measured using Western blot analyses. The localization of RAGE and its ligands in ERMs was determined with immunohistochemistry. The vitreous levels of sRAGE were significantly increased in both PDR and PVR (p < or = 0.05) compared to control vitreous. In both PDR and PVR, the vitreous levels of AGEs (p < or = 0.01), S100/calgranulins (p < or = 0.05), and amphoterin (p < or = 0.01) were also elevated compared to control eyes. Expression of RAGE was detected in six of eight ERMs from eyes with PDR and eight of 10 ERMs from eyes with PVR. Many cells expressing RAGE also expressed vimentin, suggesting a glial cell origin. Ligands for RAGE were also detected in ERMs, with AGEs detected in five eyes with PDR and eight eyes with PVR. Similarly, S100 and amphoterin ERM expression was observed in six eyes with PDR; these ligands were also expressed in ERMs from eyes with PVR (8 and 7 cases, respectively). We conclude that RAGE and its ligands are increased in the vitreous cavity of eyes with PDR and PVR and are present in ERMs of eyes with these proliferative retinal disorders. These findings suggest a role for the proinflammatory RAGE axis in the pathogenesis of proliferative retinal diseases.

The bovine vitreous-derived lipid factor (bVLF) is a powerful inhibitor of retinal pigmented epithelial (hRPE) cell proliferation

Human retinal pigmented epithelial cell (hRPE) proliferation plays a significant role in various proliferative diseases associated to the retina that leads to loss of vision, such as proliferative vitreoretinopathy. In the current study, the role of the bovine vitreous lipid factor (bVLF) in hRPE cell proliferation has been investigated. bVLF is a bioactive lipid isolated from the bovine vitreous body with strong Ca(2+)-mobilizing activity in fibroblast. In the first approach, the effects of bVLF on Ca(2+)-mobilizing activity were investigated in hRPE. The results showed that bVLF induced, in a dose-dependent manner, a Ca(2+) mobilization from PA-sensitive intracellular stores [non-Ins(1,4,5)P(3)-sensitive stores], in which extracellular Ca(2+) participated. The increase in intracellular Ca(2+) was associated with a dose-dependent inhibiting effect on cell proliferation. At a dose of 10 microg/mL, bVLF caused a 26% or a 44% inhibition in hRPE cell proliferation during the 3- or the 6-day culture periods, respectively. These effects appear to be specific in hRPE cells, since EFGR-T17 fibroblast cells treated with equivalent amounts of bVLF did not show any inhibiting effects. This inhibitory action was not associated to apoptotic/necrotic processes. Furthermore, bVLF inhibited EGF-, bFGF-, IGF-I-, PDGF-, HGF- and VEGF-induced proliferation of the hRPE cells. Moreover, this inhibitory response was also observed in FBS-induced hRPE cell proliferation. bVLF, at a concentration of 10 microg/mL, induced 16% inhibition of proliferation during a culture period of 3 days. This inhibitory action was greater during the 6-day culture period, exceeding 40%. With regard to this action, the results showed that bVLF has a potent inhibitory effect on ERK1/2 activation, and plays a key role in the control of hRPE cell proliferation. These observations contribute to the knowledge of inhibitory factors responsible for keeping antiproliferative environment that preserve the RPE-associated activities in normal states. It advances the interesting possibility that this factor or a factor with characteristics common to bVLF might be involved in the pathogenesis of abnormal proliferative eye processes.

The effect of prinomastat (AG3340), a potent inhibitor of matrix metalloproteinase, on a new animal model of epiretinal membrane

PURPOSE

To develop a simple epiretinal membrane (ERM) animal model and evaluate the efficacy of prinomastat (AG3340), a synthetic inhibitor of matrix metalloproteinase.

METHODS

This experiment was carried out on 18 eyes of nine Brown Norway rats. Preretinal hemorrhage was induced bilaterally using diode laser focused deeply on choroidal blood vessels. One day later, AG3340 was injected intravitreally in the right eyes while the left eyes received equal amounts of vehicle. The developed epiretinal membrane was measured in disk areas and compared between groups.

RESULTS

Clinically, preretinal hemorrhage showed a slow clearance persisting for 8 to 10 weeks. ERM was well established around 12 weeks. Histologically, ERMs consist of fibroblast and glial cells embedded in collagen-rich extracellular matrix infiltrated by macrophages. Seventy-five percent of the hemorrhagic laser burns in the control group developed ERM, whereas only 25% of the hemorrhagic laser burns in treated group developed ERM (P = 0.01). The total surface area of developed ERM was 3.66 DD in treated eyes versus 25.45 DD in control eyes (P = 0.049). The mean surface area of ERM per eye was 0.52 disk areas +/- 1.05 in treated eyes versus 3.18 +/- 3.07 in control eyes.

CONCLUSION

We demonstrated that ERM can be induced on rat retina by simple hemorrhagic retinal laser coagulation. This new animal model could be used for future evaluation of different medical treatment modalities for proliferating ERM. Furthermore, AG3340 demonstrated an inhibitory effect on ERM formation in this new rat model.

Expression of heme oxygenase-1 is repressed by interferon-gamma and induced by hypoxia in human retinal pigment epithelial cells

The retinal pigment epithelium (RPE) is essential for maintenance of photoreceptors and normally functions under conditions enriched with reactive oxygen species. RPE therefore expresses various defense enzymes against oxidative stress, including heme oxygenase-1 (HO-1). HO-1 catalyzes heme breakdown to release iron, carbon monoxide, and biliverdin, which is reduced to bilirubin, a potent radical scavenger. HO-1 expression is induced by various environmental factors, which has been established as a defense mechanism. To explore the hypothesis that the expression level of HO-1 is reduced in those RPE cells under certain conditions, we analyzed the effects of interferon-gamma and hypoxia, each of which represses the expression of HO-1 mRNA in other types of human cells. Expression levels of HO-1 mRNA were reduced by interferon-gamma in two human RPE cell lines, D407 and ARPE-19, which was consistently associated with the induction of mRNA for Bach1, a transcriptional repressor for the HO-1 gene. On the other hand, HO-1 and Bach1 mRNAs were induced by hypoxia in D407 cells but remained unchanged in ARPE-19 cells, suggesting that Bach1 is not a sole regulator for HO-1 expression. The hypoxia-mediated induction of HO-1 mRNA in D407 cells depends on gene transcription and protein synthesis, as judged by the effects of their inhibitors. The half-life of HO-1 mRNA did not change during hypoxia. Thus, hypoxia may increase transcription of the HO-1 gene through a certain protein factor in RPE cells. These results indicate that RPE cells maintain retinal homeostasis by repressing or inducing the expression of HO-1, depending on the microenvironment.

Nestin positive cells in adult human retina and in epiretinal membranes

BACKGROUND/AIM

Nestin is an intermediate filament marker for neural progenitor cells. The authors aimed to identify nestin positive cells in adult human retina and within surgically removed epiretinal membranes.

METHODS

Adult human retina and epiretinal membranes were studied. Tissue was fixed and processed for semithin sections or whole mount preparations for immunohistochemical detection of nestin and glial fibrillary acidic protein (GFAP) expression.

RESULTS

Nestin positive cells are most prominent at the ora serrata, possess fibrillary processes, small amounts of perinuclear cytoplasm, and are arranged radially within or superficially on the retina. In the posterior retina, speckled cytoplasmic nestin staining is seen around the nuclei of neurons. In the peripapillary retina most of the cells in the retinal ganglion cell layer are nestin positive. These cells appear to represent nestin positive neurons. Speckled cells are also seen in the myelinated portion of the optic nerve. In epiretinal membranes patches of elongated nestin positive cells were found. These cells were also positive for GFAP.

CONCLUSIONS

Some neurons and glia in the adult human retina are nestin positive. Their pattern in anterior retina suggests an analogy with the ciliary marginal zone found in many other species. The role of these cells in pathological responses to retinal disease is suggested by the presence of large numbers of ectopic nestin positive cells in epiretinal membranes. The authors hypothesise that nestin positive cells represent a population of progenitor cells from normal adult human retina that differentiate to make up retinal scar tissue.

Adrenomedullin in the eye

Adrenomedullin (AM) is a multifunctional regulatory peptide that is produced and secreted by various types of cells. We showed the presence of high concentrations of adrenomedullin-immunoreactivity in the vitreous fluid, and the levels were elevated in patients with proliferative vitreoretinopathy. Furthermore, adrenomedullin mRNA expression levels were elevated in the tissues of intraocular tumors and orbital tumors. Adrenomedullin is produced and secreted by cultured human retinal pigment epithelial (RPE) cells. Inflammatory cytokines and hypoxia are strong stimulators for the adrenomedullin expression in retinal pigment epithelial cells. Adrenomedullin stimulated the proliferation of retinal pigment epithelial cells both under normoxia and hypoxia. Dexamethasone (DEX) increased the adrenomedullin expression in two cultured cell lines of human retinal pigment epithelial cells; ARPE-19 cells and D407 cells, while it had no noticeable effects on the cytokine-induced adrenomedullin expression. These findings suggest that adrenomedullin is involved in the pathophysiology of inflammatory and neoplastic eye diseases as an autocrine or paracrine growth stimulator. The findings on glucocorticoid-induced AM expression raise the possibility that it may be related to the pathogenesis of some eye diseases, such as central serous chorioretinopathy and multifocal posterior pigment epitheliopathy, which are frequently seen in patients treated with high doses of glucocorticoids.

Differential expression of matrix metalloproteinases 2 and 9 by glial Müller cells: response to soluble and extracellular matrix-bound tumor necrosis factor-alpha

Glial Müller cells are known to undergo functional and morphological changes during retinal proliferative disorders, but very little is known of the contribution of these cells to extracellular matrix deposition during retinal wound healing and gliosis. This study constitutes the first demonstration that retinal Müller cells express two major matrix metalloproteinases (MMPs), gelatinase A (MMP-2) and gelatinase B (MMP-9), implicated in cell migration and matrix degradation. Although mRNA and gelatinolytic activity of MMP-2 remained unchanged in cultured Müller cells, basal levels of MMP-9 mRNA observed after subculture at 24 hours, markedly declined after 48 or 72 hours. This correlated with the expression of MMP-9 gelatinolytic activity that peaked at 24 hours, but gradually decreased at 48 and 72 hours. Tumor necrosis factor-alpha, in both a soluble form or bound to collagen and fibronectin, increased MMP-9 mRNA and gelatinolytic activity, but not MMP-2 expression, and its effect could be blocked by anti-tumor necrosis factor-alpha antibodies. The results suggest that Müller cells may aid in the local control of extracellular matrix deposition during retinal proliferative disorders, and that interaction of these cells with matrix-bound cytokine may influence their pathological behavior. Control of Müller cell production of MMP-9 may constitute an important target for the design of new therapeutic approaches to treat and prevent retinal proliferative disease.

Safety of intravitreous fomivirsen for treatment of cytomegalovirus retinitis in patients with AIDS

PURPOSE

To report data regarding the safety of intravitreous fomivirsen for treatment of cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS).

DESIGN

Critical review of safety data from three randomized controlled clinical trials with supplemental information from an expanded drug access program.

METHODS

Adverse ocular events reported by clinician investigators were listed using terms modified from the COSTART dictionary. Data for two doses (165-microg/injection [35 eyes, 30 patients] and 330-microg/injection [153 eyes, 120 patients]) and two 330-microg/injection dose schedules of different intensity were pooled to calculate incidence rates for each event. Rates were calculated as "events/patient-year" (based on total cumulative reported events and duration of treatment) for events that could recur during treatment. Rates were calculated as "patients with events/person-year" for the following events: retinal detachment, cataract, visual field disturbance, and retinal pigment epitheliopathy. To assess the ability to manage events, we reviewed treatments given for two events (anterior chamber inflammation, increased intraocular pressure) in one trial. We also report an analysis comparing the proportion of eyes that developed one or more key events to the cumulative number of injections.

RESULTS

Incidence rates were dose and schedule dependent (165 microg/injection, 4.06 events/patient-year; 330 microg/injection, 6.58 events/patient-year [less intense regimen] and 8.35 events/patient-year [more intense regimen]). The most frequently reported events were anterior chamber inflammation and increased intraocular pressure. We found no evidence that the proportion of patients with events increased as the number of injections increased.

CONCLUSIONS

Intravitreous fomivirsen is well tolerated with an acceptable safety profile. Adverse ocular events associated with doses and schedules used clinically can be managed successfully with medical therapy.

Intravitreal invading cells contribute to vitreal cytokine milieu in proliferative vitreoretinopathy

AIM

To examine the contribution of infiltrating cells in the local production of cytokines within the vitreous of patients with proliferative vitreoretinopathy (PVR).

METHODS

The presence of mRNA coding for IL-6, IL-8, IL-1beta, IL-1alpha, TNFalpha, IFNgamma, IL-12, and HPRT was investigated in 25 vitreous samples from patients with PVR, 11 vitreous samples from patients with retinal detachment (RD) not complicated by PVR, and 10 vitreous samples from patients with macular hole (MH). A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) using an internal competitor was used to investigate these samples. From these samples, 15 PVR, 8 RD, and 8 MH were analysed for the protein levels of the same cytokines using enzyme linked immunosorbent assay (ELISA). Spearman correlation was used to test any association between mRNA and cytokine protein levels, as an indicator of the contribution these cells make to the intravitreal cytokine milieu.

RESULTS

A strong correlation was found between mRNA and their respective cytokine levels (protein products) for IL-6, IL-8, IL-1beta, IL-1alpha, TNFalpha, IFNgamma (Spearman r = 0.83, 0.73, 0.67, 0.91, 0.73, and 0.73 respectively), but not for IL-12. The median levels of IL-6, IL-8, IL-1beta, and IFNgamma mRNA and their respective cytokines were significantly higher (p <0.05) in patients with PVR than in those with macular hole. There was no statistically significant difference in the median levels of IL-1alpha mRNA between PVR and MH but the cytokine IL-1alpha was detected at a significantly higher level in PVR compared with MH patients. Between PVR and RD patients, there was no statistically significant difference in mRNA levels for all the investigated cytokines (p >0.05) except for IL-6 where there was a statistical significance (p= 0.038). In contrast, the median levels of IL-6, IL-8, and IL-1beta cytokines were significantly higher (p <0.05) in patients with PVR than in those with RD, whereas for IL-1alpha and IFNgamma no significant statistical difference was detected between PVR and RD patients (p >0.05). When results of RD and MH patients were compared, a statistical difference was only detected in mRNA levels of INFgamma (p = 0.008). However, no difference was detected for INFgamma (protein product) or for any of the other cytokines between RD and MH patients.

CONCLUSION

Levels of both protein and mRNA encoding IL-6, IL-8, IL-1beta, and IFNgamma is significantly increased in vitreous samples from patients with PVR. The strong correlation between ELISA detectable cytokines (protein products) and their respective mRNA levels suggest that intravitreal, invasive cells are the major source of these cytokines, with the exception of IL-12. Cells invading the vitreous do not appear to locally produce IL-12 mRNA. This would appear to implicate cells peripheral to the vitreal mass as the major source of this cytokine.

Vitreous levels of vascular cell adhesion molecule and vascular endothelial growth factor in patients with proliferative diabetic retinopathy: a case-control study

OBJECTIVE

To evaluate the intravitreous concentration of vascular cell adhesion molecule (VCAM)-1 in diabetic patients with proliferative diabetic retinopathy (PDR) and the relationship of VCAM-1 with vascular endothelial growth factor (VEGF).

RESEARCH DESIGN AND METHODS

Serum and vitreous fluid samples were obtained simultaneously at the onset of vitrectomy from 20 diabetic patients with PDR and 20 nondiabetic control subjects with nonproliferative ocular disease. Both groups were matched by serum levels of VCGM-1 and VEGF. VCAM-1 and VEGF were determined by enzyme-linked immunosorbent assay. Statistics were determined using the Mann-Whitney U test and Spearman's rank correlation test.

RESULTS

The intravitreous concentration of VCAM-1 was signifcantly elevated in diabetic patients with PDR compared with control subjects (26 ng/ml [19-118] vs. 22 ng/ml [20-47], P < 0.05). A direct correlation between VCAM-1 and total vitreous proteins was detected in diabetic patients (r = 0.64, P = 0.003), but not in control subjects. After adjusting for total intravitreous proteins, VCAM-1 was significantly lower in diabetic patients with PDR than in control subjects (8.2 ng/ml [4-31.4] vs. 43.1 ng/ml [9.7-100], P < 0.001). Intravitreous VEGF concentrations were higher in patients with PDR than in control subjects in absolute terms (1.34 ng/ml [0.16-6.22] vs. 0.009 ng/ml [0.009-0.044], P < 0.0001) and after correcting for total vitreal proteins (0.33 ng/ml [0.01-2.3] vs. 0.013 ng/ml [0.003-0.035], P = 0.0001). Finally, the vitreous ratio of VCAM-1 to proteins correlated with the vitreous ratio of VEGF to proteins in both diabetic patients (r = 0.74, P = 0.001) and control subjects (r = 0.84, P = 0.005).

CONCLUSIONS

The low proportion of VCAM-1 in relation to total vitreal proteins observed in diabetic patients with PDR suggests that VCAM-1 is quenched by diabetic retina. In addition, the direct correlation detected between VCAM-1 and VEGF suggests that cellular adhesion and neovascularization may be linked processes.

Macrophage migration inhibitory factor levels in the vitreous of patients with proliferative diabetic retinopathy

AIMS

To assess the potential role of macrophage migration inhibitory factor (MIF) in the pathogenesis of proliferative diabetic retinopathy (PDR).

METHODS

MIF levels were assayed in the vitreous and paired serum samples of 73 consecutive patients with PDR (32 eyes) and macular hole or idiopathic epiretinal membrane (controls, 41 eyes). An enzyme linked immunosorbent assay technique was used to determine the concentrations of MIF.

RESULTS

The median vitreous level of MIF was 11.93 ng/ml (range 4.16-103.85) in the patients with PDR, and 1.79 ng/ml (undetectable-8.93) in the controls. Vitreous levels in eyes with PDR were significantly greater than those in the controls (p<0.0001). Vitreous levels were significantly higher than serum levels in eyes with PDR (p=0.0026). MIF levels were significantly higher in the vitreous of PDR patients with severe fibrous proliferation than in those with slight proliferation (p<0.05).

CONCLUSION

The results indicate increased levels of MIF in the vitreous of patients with PDR and a significant association between MIF levels and grades of fibrous proliferation, suggesting the possibility that MIF may play a part in the development of the proliferative phase of PDR.

Detection of cytokine mRNA production in infiltrating cells in proliferative vitreoretinopathy using reverse transcription polymerase chain reaction

AIMS

To determine whether the infiltrating cells in the vitreous and subretinal fluid of patients with proliferative vitreoretinopathy (PVR) express messenger RNA for various cytokines found in this condition.

METHODS

The presence of mRNA coding for HPRT, IL-6, IL-1beta, IL-8, and TNFalpha was investigated in 20 vitreous and subretinal fluid (SRF) samples from patients with PVR by reverse transcriptase polymerase chain reaction (RT-PCR). 16 samples from patients with retinal detachment and macular holes were used as controls.

RESULTS

HPRT was detected in all samples of PVR and in 11 (69%) control cases. Patients with PVR demonstrated mRNA for the cytokines tested more often than controls. The difference was statistically significant.

CONCLUSION

The presence of mRNA encoding for IL-6, IL-1beta, IL-8, and TNFalpha is significantly detected by RT-PCR in vitreous and SRF samples of patients with PVR, indicating local production of these cytokines by vitreous and SRF cells.

Cell adhesion molecules in subretinal fluid: soluble forms of VCAM-1 (vascular cell adhesion molecule-1) and L-selectin

PURPOSE

In this study we investigated the presence of soluble VCAM-1 and soluble L-selectin-1 in subretinal fluids (SRF) of patients suffering from rhegmatogenous retinal detachment .

METHOD

Subretinal fluids were collected from drainage sclerotomies during surgery from 27 patients with rhegmatogenous retinal detachment complicated by proliferative vitreoretinopathy (PVR) or uncomplicated retinal detachment. Levels of sVCAM-1 and sL-selectin-1 were quantified with ELISA.

RESULTS

The mean +/- SEM values of sVCAM-1 and sL-selectin-1 were 222.2 +/- 81 ng/ml and 171.7 +/- 42.1 ng/ml, respectively. The concentrations of sVCAM-1 in patients with Grade C PVR (498.2 +/- 1703 ng/ml) were significantly different from those with Grade B PVR (45.6 +/- 16.5 ng/ml) and uncomplicated retinal detachments (19.4 +/- 12.3 ng/ml). SVCAM-1 concentration in detachments which had been present for more than 8 weeks was 738.8 +/- 431 ng/ml, significantly higher than the levels in detachments of shorter duration (132.4 +/- 47.7 ng/ml). sL-selectin-1 level in Grade C PVR (291.6 +/- 92.8 ng/ml) was higher than in uncomplicated retinal detachments (72.8 +/- 13.5 ng/ml). Significantly elevated levels of sL-selectin-1 were observed in detachments lasting more than 8 weeks (605 +/- 151.1 ng/ml) compared to those of shorter duration (96.3 +/- 13.1 ng/ml).

CONCLUSION

The present study supports growing evidence that these cell adhesion molecules are involved in the inflammatory process during the development and progression of PVR.

Vitreous levels of intercellular adhesion molecule 1 (ICAM-1) as a risk indicator of proliferative vitreoretinopathy

AIM

To investigate whether high vitreous levels of the soluble intercellular adhesion molecule 1 (sICAM-1) may be related to clinical risk factors of proliferative vitreoretinopathy (PVR) and whether their measurement may serve as an additional risk indicator of this complication in eyes with rhegmatogenous retinal detachment (RRD).

METHODS

Levels of sICAM-1 were measured by enzyme linked immunosorbent assays (ELISA) in vitreous from 36 eyes with RRD clinically considered to be at high risk of developing PVR (large retinal breaks, vitreous haemorrhage, long standing RRD, and previous vitreoretinal surgery). Levels of sICAM-1 in this group were compared with those in vitreous from 31 eyes with RRD without clinical risk factors for PVR, 32 eyes with established PVR and 10 eyes with macular holes.

RESULTS

Vitreous from eyes with RRD at high risk of developing PVR contained significantly higher levels of sICAM-1 (range 6.1-97.7 ng/ml; Mann-Whitney test, p=0.0002) than those from eyes with RRD at low risk of developing this complication (range 4.8-17.7 ng/ml). Vitreous sICAM-1 levels in eyes with RRD at high risk of developing PVR were significantly lower than in eyes with established PVR (p=0.037), but higher than in eyes with macular holes (p <0.0001). Levels of sICAM-1 >/=15 ng/ml (3 x median of the levels present in control eyes) provide a useful cut off point for a highly specific test (96.7%) with high positive (91.6%) and negative (96.7%) predictive values, despite a relatively low sensitivity (30. 5%).

CONCLUSIONS

The present findings suggest that laboratory measurement of sICAM-1 levels in vitreous from eyes with RRD may constitute an additional factor for identifying patients at high risk of PVR. Hence, determination of sICAM-1 levels may aid in the monitoring of patients likely to develop this complication and in the identification of patients who may benefit from adjuvant anti-inflammatory therapy.

Dexamethasone reduces oxygen induced retinopathy in a mouse model

Dexamethasone is widely used in the postnatal period. Its impact on retinopathy of prematurity (ROP) is extremely controversial; published studies have found a detrimental, protective, or no effect on ROP. The goal of this study was to test the hypothesis that use of dexamethasone during the injury phase (oxygen exposure) reduces the severity of oxygen-induced retinopathy (OIR) in a mouse model. C57BL6 mice pups were exposed to either room air or hyperoxia (75% FiO2) from postnatal d 7 through 12 (PN7-12) with or without dexamethasone (0.5 mg/kg/d s.c.) and killed on PN17-21. Retinopathy was assessed by a scoring system of retinal flat mount preparations and periodic acid-Schiff (PAS) staining of retinal sections. Pups exposed to dexamethasone and oxygen had a lower median retinopathy score of 5 (4, 6) [median (25th, 75th quartile)] compared with animals exposed to oxygen alone with median score of 9 (6, 10) with p < 0.001. PAS staining for extra retinal neovascularization in the dexamethasone and oxygen treated animals showed a significant reduction in number of nuclei extending beyond the inner limiting membrane when compared with oxygen exposed alone (p = 0.04). Animals treated with dexamethasone had decreased weight gain compared with control animals. Dexamethasone did not appear to affect the normal development of retinal vasculature as assessed by the scoring system when compared with control animals. Thus, dexamethasone decreases severity of OIR without having an adverse effect on normal retinal vascular development in the mouse model. We speculate that dexamethasone decreases the injury response that occurs during the hyperoxic phase, thus protecting the developing vasculature and improving the subsequent retinopathy.