Immunohistologic study of epiretinal membranes in proliferative vitreoretinopathy

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

Purpose

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

Methods

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

Results

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

Conclusions

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

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.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Quantitative proteomics analysis of human vitreous in rhegmatogenous retinal detachment associated with choroidal detachment by data-independent acquisition mass spectrometry

The prognosis of rhegmatogenous retinal detachment (RRD) with choroidal detachment (RRDCD) is often poor and complicated. This study focused on the identification of the characteristic proteins and signal pathways associated with the etiology of RRDCD and to provide guidance for diagnosis and treatment of RRDCD. In this study, vitreous humor samples were obtained from 16 RRDCD patients, 14 with RRD, 12 with idiopathic epiretinal macular membrane (IEMM), and 5 healthy controls from donated corpse eyes. Data-independent acquisition mass spectrometry and bioinformatics analysis were employed to identify differentially expressed proteins (DEPs). In the vitreous humor, 14,842 peptides were identified. Patients with RRDCD had 249 DEPs (93 upregulated and 156 downregulated), with 89 in patients with RRD and 61 in patients with IEMM. Enrichment analysis of the GO and Kyoto Encyclopedia of Genes and Genomes DEP databases indicated functional clusters related to inflammation and immunity, protein degradation and absorption, cell adhesion molecules (CAMs), the hedgehog signaling pathway, and lipid metabolism. Weighted gene co-expression network analysis showed that DEPs with positive co-expression of RRDCD participated in immune-related pathways led by the complement and coagulation cascade, whereas DEPs with negative co-expression of RRDCD participated in protein degradation and absorption, CAMs, and the hedgehog signaling pathway. In summary, our study provides important clues and the theoretical basis for exploring the pathogenesis, progression, and prognosis of ocular fundus disease.

Myo/Nog cells expressing muscle proteins are present in preretinal membranes from patients with proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a complication of rhegmatogenous retinal detachment and ocular trauma. The disease is characterized by development of membranes that may apply traction to the retina and cause redetachment. Membrane contractions are attributed to myofibroblasts arising from retinal pigment epithelial cells, glia and fibroblasts. The progenitors of myofibrobasts in the lens are Myo/Nog cells that express the skeletal muscle transcription factor MyoD and bone morphogenetic protein inhibitor Noggin. The retina and choroid also contain Myo/Nog cells that respond to stress. We examined preretinal PVR membranes from three ocular trauma patients with retinal detachment for Myo/Nog cells and their expression of muscle proteins. Myo/Nog cells were identified by co-localization of antibodies to the G8 antigen and Noggin. Greater than 80% of all cells in sections from two of three patients expressed both G8 and Noggin. Myo/Nog cells lacked pigment. Alpha smooth muscle actin (α-SMA) and striated myosin II heavy chain were present in the majority of Myo/Nog cells in these two patients. Differentiation of Myo/Nog cells was paralleled by low levels of MyoD. Membrane sections from the third patient consisted mostly of connective tissue with very few cells. A small subpopulation in these sections expressed both G8 and Noggin, and muscle proteins were detected in only a minority of G8-positive (+) cells. In all three patients, greater than 99% of cells with MyoD, α-SMA and striated muscle myosin co-expressed G8. These findings suggest that contractile myofibroblasts in PVR membranes may be derived from differentiating Myo/Nog cells.

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.

Mononuclear Phagocytes in Proliferative Vitreoretinopathy (PVR). A Specific Role of Microglial Cells in Non-Traumatic Disease?

Mononuclear phagocytes have been a focus of attention in the cellular biology of proliferative vitreoretinopathy (PVR) for more than ten years. The pattern of phagocyte participation in periretinal traction membrane formation in PVR depends on the etiology, i.e. trauma, rhegmatogenous retinal detachment, previous therapy, i.e. multiple surgical interventions, and the clinical stage of the disease. We have recently identified microglial cells as a distinct cellular population, in membranes from patients with non-traumatic PVR. Current evidence of mononuclear phagocyte function in PVR suggests a role for resident phagocytes of the vitreous and retina in PVR subsequent to rhegmatogenous detachment, and a role for blood-derived monocytes in post-traumatic PVR. The cellular biology of PVR may be much more heterogeneous than previously assumed.

STAINING-ASSISTED REMOVAL OF SILICONE OIL FOR THE IDENTIFICATION OF SUBCLINICAL PROLIFERATIVE VITREORETINOPATHY

PURPOSE

Retinal detachment is a frequent complication after removal of silicone oil (ROSO). A retrospective study was conducted to determine whether staining-assisted removal of silicone oil (st-ROSO) allowed better identification and removal of proliferative vitreoretinopathy (PVR) processes compared with a conventional removal of silicone oil technique.

METHODS

All individuals underwent pars plana vitrectomy (PPV) and silicone oil fill-in for complicated retinal detachments. In conventional removal of silicone oil (Group 1), no staining was used. In staining-assisted removal of silicone oil (Group 2), a mixture of trypan blue and brilliant blue G dyes was used to identify proliferative vitreoretinopathy and subclinical epiretinal membrane.

RESULTS

After the first 3-month follow-up, 15.9% of patients (N = 608) developed a retinal detachment. Retinal detachment occurred in 22.8% of patients in Group 1 (n = 284) and 9.8% of patients in Group 2 (n = 324; P < 0.001). In Group 2, proliferative vitreoretinopathy removal was performed in 153 eyes (47.2%).

CONCLUSION

The incidence of retinal redetachment was significantly lower after staining-assisted removal of silicone oil compared with a conventional technique. Staining-assisted removal of silicone oil allowed better identification and removal of proliferative vitreoretinopathy processes.

Identification of Potential Biomarkers for Rhegmatogenous Retinal Detachment Associated with Choroidal Detachment by Vitreous iTRAQ-Based Proteomic Profiling

Rhegmatogenous retinal detachment associated with choroidal detachment (RRDCD) is a complicated and serious type of rhegmatogenous retinal detachment (RRD). In this study, we identified differentially expressed proteins in the vitreous humors of RRDCD and RRD using isobaric tags for relative and absolute quantitation (iTRAQ) combined with nano-liquid chromatography-electrospray ion trap-mass spectrometry-mass spectrometry (nano-LC-ESI-MS/MS) and bioinformatic analysis. Our result shows that 103 differentially expressed proteins, including 54 up-regulated and 49 down-regulated proteins were identified in RRDCD. Gene ontology (GO) analysis suggested that most of the differentially expressed proteins were extracellular．The Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis suggested that proteins related to complement and coagulation cascades were significantly enriched. iTRAQ-based proteomic profiling reveals that complement and coagulation cascades and inflammation may play important roles in the pathogenesis of RRDCD. This study may provide novel insights into the pathogenesis of RRDCD and offer potential opportunities for the diagnosis and treatment of RRDCD.

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.

Is neutralizing vitreal growth factors a viable strategy to prevent proliferative vitreoretinopathy?

Proliferative vitreoretinopathy (PVR) is a blinding disorder that occurs in eyes with rhegmatogenous retinal detachment and in eyes that have recently undergone retinal detachment surgery. There are presently no treatment strategies to reduce the risk of developing PVR in eyes with retinal detachment, and surgical intervention is the only option for eyes with retinal detachment and established PVR. Given the poor visual outcome associated with the surgical treatment of PVR, considerable work has been done to identify pharmacologic agents that could antagonize the PVR process. Intensive efforts to identify molecular determinants of PVR implicate vitreal growth factors. A surprise that emerged in the course of testing the 'growth factor hypothesis' of PVR was the existence of a functional relationship amongst growth factors that engage platelet-derived growth factor (PDGF) receptor α (PDGFRα), a receptor tyrosine kinase that is key to pathogenesis of experimental PVR. Vascular endothelial cell growth factor A (VEGF), which is best known for its ability to activate VEGF receptors (VEGFRs) and induce permeability and/or angiogenesis, enables activation of PDGFRα by a wide spectrum of vitreal growth factors outside of the PDGF family (non-PDGFs) in a way that triggers signaling events that potently enhance the viability of cells displaced into vitreous. Targeting these growth factors or signaling events effectively neutralizes the bioactivity of PVR vitreous and prevents PVR in a number of preclinical models. In this review, we discuss recent conceptual advances in understanding the role of growth factors in PVR, and consider the tangible treatment strategies for clinical application.

A novel function of p53: a gatekeeper of retinal detachment

Proliferative vitreoretinopathy (PVR) is a blinding disease associated with rhegmatogenous retinal detachment, for which there is no satisfactory treatment. Surgery helps in many cases, but, to our knowledge, there are no pharmacological approaches to reduce PVR risk. We report that suppressing expression of p53 was a required event in two assays of PVR (namely, platelet-derived growth factor receptor α-mediated contraction of cells in a collagen gel and retinal detachment in an animal model of PVR). Furthermore, preventing the decline in the level of p53 with agents such as Nutlin-3 protected from retinal detachment, which is the most vision-compromising component of PVR. Finally, Nutlin-3 may be effective in the clinical setting because it prevented human PVR vitreous-induced contraction of cells isolated from a patient PVR membrane. These studies identify Nutlin-3 as a potential PVR prophylaxis.

Platelet-derived growth factor induced alpha-smooth muscle actin expression by human retinal pigment epithelium cell

PURPOSES

(1) To evaluate the association between expression of α-smooth muscle actin (α-SMA) in proliferative vitreoretinopathy (PVR) and the pathological grading of PVR, and the effect of platelet-derived growth factor (PDGF) on the expression of α-SMA by human retinal pigment epithelial (RPE) cells. (2) To investigate the potential induction of PDGF on the proliferation and migration of human RPE cells as well as the signaling pathways responsible.

METHODS

We immunohistochemically investigated the expression of α-SMA in PVR. To further investigate the effect of PDGF and the downstream signaling, exogenous PDGF-BB and signaling inhibitors were added to cultured human RPE cells. The MTT method was performed to detected cell proliferation, while cell migration was also measured.

RESULTS

α-SMA expression was positively correlated with the pathological grading of PVR. PDGF-BB could stimulate the proliferation and migration of cultured RPE cells through the participation of mitogen-activated protein kinase. In addition, PDGF induced α-SMA expression. The promotion of proliferate/migration and α-SMA expression by PDGF-BB was enhanced by the presence of serum.

CONCLUSIONS

PDGF and α-SMA are 2 potential therapeutic targets for the treatment of PVR.

Assessment of the innate and adaptive immune system in proliferative vitreoretinopathy

PURPOSE

Proliferative vitreoretinopathy (PVR) is the leading cause of failure of surgery for rhegmatogenous retinal detachment. Although indirect evidence suggests that this disease might be autoimmune in nature, direct proof for this hypothesis is lacking. The purpose of this study was to determine in a murine model whether PVR can develop in the absence of T- or B-cell immunity.

METHODS

Four- to six-week-old Rag-1 gene knockout (KO) and congenic wild-type mice (WT) on the C57.Bl/6 background were studied. PVR was induced by intravitreal injection of 3 μl dispase at the concentration of 0.2 U/μl. PVR development was monitored by electroretinograms, the macroscopic observation of hemorrhage, cataract, retinal folds, and of an uneven iris, as well as the histological detection of epiretinal membranes on haematoxylin-eosin stained tissue. Additionally, immunofluorescence analysis was performed. These manifestations of PVR were assessed 1, 2, 4, 6, and 8 weeks after the intravitreal injection.

RESULTS

The data showed that the immune-deficient Rag-1 KO mice developed PVR with similar kinetics and severity as did the fully immune competent congenic WT mice. Carboxyfluorescein diacetate succinimidyl ester-labeled T cells that are specific for ovalbumin were detected in the inflamed vitreous and retina showing that T cells that are not specific for autoantigens present in the eye can migrate to PVR lesions. Therefore, the mere presence of T cells in PVR lesions does not imply an autoimmune pathogenesis.

CONCLUSION

This study suggests that T- and B-cell immunity is not essential for the induction of PVR.

Contrary effects of cytokines on mRNAs of cell cycle- and ECM-related proteins in hRPE cells in vitro

PURPOSE

Retinal pigment epithelial (RPE) cells play a pivotal role in the pathogenesis of proliferative vitreoretinopathy (PVR). As a result of a breakdown of the blood-retina barrier, growth factors obtain access to the subretinal space and stimulate several retinal cell types. The aim of the present study was to analyze the effect of several growth factors on the proliferation of human (h)RPE cells, and on the mRNA expression of transcription factors, cell cycle proteins, and extracellular matrix (ECM) proteins.

METHODS

hRPE cells were incubated in the presence of TGF-beta1, TGF-beta2, PDGF, VEGF, or bFGF for 24-72 h. Cell proliferation was assessed by determinating BrdU incorporation. Changes in mRNA expression of c-fos, c-myc, PCNA, FEN1, Ki67, collagen III, and collagen IV were investigated by ribonuclease protection assay (RPA).

RESULTS

RPE cell proliferation was significantly increased by exposure to PDGF and bFGF for 48 h, and was decreased by application of TGF-beta1 and TGF-beta2 for 48 and 72 h. All the tested growth factors significantly elevated the amounts of c-fos mRNA (after 1 h) and of c-myc mRNA (after 24 h). PDGF and bFGF up-regulated the expression of Ki67 mRNA, and down-regulated that of collagen III and collagen IV mRNA after 24 h. TGF-beta1 and TGF-beta2 decreased the expression of Ki67 mRNA, and increased that of collagen III and collagen IV mRNA.

CONCLUSION

Our results show that distinct cytokines may induce contrary effects with respect to proliferation of, and ECM formation by, hRPE cells in vitro. This knowledge may be useful for the development of improved therapeutic approaches.

Growth factors outside the PDGF family drive experimental PVR

PURPOSE

Proliferative vitreoretinopathy (PVR) is a recurring and problematic disease for which there is no pharmacologic treatment. Platelet-derived growth factor (PDGF) in the vitreous is associated with experimental and clinical PVR. Furthermore, PDGF receptors (PDGFRs) are present and activated in epiretinal membranes of patient donors, and they are essential for experimental PVR. These observations suggest that PVR arises at least in part from PDGF/PDGFR-driven events. The goal of this study was to determine whether PDGFs were a potential therapeutic target for PVR.

METHODS

Experimental PVR was induced in rabbits by injecting fibroblasts. Vitreous specimens were collected from experimental rabbits or from patients undergoing vitrectomy to repair retinal detachment. A neutralizing PDGF antibody and a PDGF Trap were tested for their ability to prevent experimental PVR. Activation of PDGFR was monitored by antiphosphotyrosine Western blot analysis of immunoprecipitated PDGFRs. Contraction of collagen gels was monitored in vitro.

RESULTS

Neutralizing vitreal PDGFs did not effectively attenuate PVR, even though the reagents used potently blocked PDGF-dependent activation of the PDGF alpha receptor (PDGFRalpha). Vitreal growth factors outside the PDGF family modestly activated PDGFRalpha and appeared to do so without engaging the ligand-binding domain of PDGFRalpha. This indirect route to activate PDGFRalpha had profound functional consequences. It promoted the contraction of collagen gels and appeared sufficient to drive experimental PVR.

CONCLUSIONS

Although PDGF appears to be a poor therapeutic target, PDGFRalpha is particularly attractive because it can be activated by a much larger spectrum of vitreal growth factors than previously appreciated.

Vitreous proteomic analysis of proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is the most common cause of anatomic failure in retinal detachment surgery. To understand the molecular mechanisms, vitreous proteomes of patients with PVR were investigated by two-dimensional-nano-liquid chromatography coupled with tandem mass spectrometry. Vitreous samples of moderate PVR (grade B), and severe PVR (grade C or D) were aspirated during pars plana vitrectomy before infusion. In the current study, 129, 97 and 137 proteins were identified in vitreous of normal control, moderate and severe PVR, respectively. In PVR vitreous samples, complement components, serine proteinase inhibitors, and extracellular proteins were up-regulated or appeared, while normal cytoskeleton and metabolism proteins were down-regulated or disappeared. It was noteworthy that the proteins involved in transcription and translation regulation increased in vitreous with PVR. Among 102 PVR-specific proteins, kininogen 1 was specifically detected in both vitreous and the corresponding serum. Therefore, it can be concluded that PVR is a complicated pathology process with great amount of proteins involved in metabolism dysfunction, immune reactions, and cytoskeleton remolding. Kininogen 1 may be a candidate biomarker of PVR. Further investigations of these special proteins will provide additional targets for treatment or prevention of ocular proliferative diseases.

Immunopathology of intraocular silicone oil: retina and epiretinal membranes

AIMS

To determine the inflammatory response in retina and epiretinal membranes after intraocular silicone oil tamponade.

METHODS

14 proliferative vitreoretinopathy (PVR) epiretinal membranes, 33 retro-oil epiretinal membranes, 19 retinectomies, 14 retro-oil retinectomies and 37 idiopathic epiretinal membranes (controls) underwent immunohistochemical analysis using the avidin-biotin complex technique and a panel of monoclonal and polyclonal antibodies. The number of positive cells counted in five 0.5 mm diameter fields of immunohistochemical sections was graded on a score of 1-4.

RESULTS

Macrophage cell counts were significantly greater in membranes with a history of exposure to silicone oil (p<0.001). An inflammatory response could be observed within 1 month of silicone oil exchange, and the intensity seemed to be unrelated to the duration of exposure. Macrophages were confined to epiretinal membranes on the surface of retinectomy specimens in 10 of 14 cases and intraretinal macrophages were observed only in specimens with gliotic retina. T and B lymphocytes were rarely seen in the specimens examined. Marked glial cell up regulation was observed in 11 of 16 retinectomy specimens and in 8 of 11 retro-oil retinectomies. Glial cell content was variable in the membranes, but there was a trend of increased presence after exposure to silicone oil.

CONCLUSION

This study has shown that the use of silicone oil is accompanied by an inflammatory reaction, primarily mediated by bloodborne macrophages. This response can be observed within 1 month of silicone oil injection and continues after silicone oil removal. Retinal surgeons should be aware of the potential secondary effects of intraocular silicone oil when they are considering its use (and removal) in vitreoretinal surgery.

Intérêt de la microscopie confocale in vitro dans l’étude des membranes épirétiniennes et des membranes limitantes internes après chirurgie maculaire

PURPOSE

To study specimens obtained from epiretinal membrane (ERM) and macular hole surgery with confocal microscopy and to evaluate its advantages in understanding their pathophysiology.

MATERIAL AND METHODS

This retrospective study included 50 patients undergoing surgery for epiretinal membrane (40 patients) or idiopathic macular hole (10 patients). Infracyanine green was used in 45 cases. Immunohistological examination of the excised tissues was undertaken using confocal microscopy after labeling with antibodies to glial fibrillary acidic protein (GFAP) and vimentin.

RESULTS

Confocal microscopic analysis of epiretinal membranes identified three types of tissues: 13 ERMs, which appeared thick and rich in cells, 20 internal limiting membranes (ILMs), which appeared thin, wrinkled and poor in cells, and seven composite tissues, where ERM and ILM were removed at the same time. The analysis of ten specimens obtained from macular hole surgery revealed nine ILMs and one composite tissue that were quite similar to those removed in epiretinal membrane surgery. In all, 27 specimens (10 ERMs, 12 ILMs and five composite tissues) contained GFAP-positive glial cells.

CONCLUSION

The confocal microscope provided a fast, three-dimensional analysis of ERMs and ILMs. An immunohistological study identified cells that take part in the genesis of the membranes. Glial cells were found both in ERM and ILM specimens. Our findings suggest that Müller's cells may contribute to the pathogenesis of ERM and macular hole development.

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.

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.

Proliferative vitreoretinopathy: an overview

Proliferative vitreoretinopathy (PVR) is still the most common cause of failure of surgery for rhegmatogenous retinal detachment, despite the substantial effort that has been devoted to better understanding and managing this condition during the past 25 years. Basic research has indicated that PVR represents scarring, the end stage of the wound-healing process that occurs after retinal detachment surgery. Medical treatment has been directed toward preventing inflammation, the first phase of the wound healing process, and inhibiting cell proliferation, the second phase. The 1983 Retina Society classification was modified in 1989 by the Silicone Study Group, whose classification differentiates between posterior and anterior forms of PVR and recognizes three patterns of proliferation: diffuse, focal, and subretinal. The anterior form has a worse prognosis than the posterior form, and its treatment requires more complex surgical procedures. In this review, risk factors and pathobiology of PVR are discussed, and management of PVR of various degrees of severity are considered.

Gelatinase B in proliferative vitreoretinal disorders

PURPOSE

To investigate whether gelatinases A and B are involved in the pathogenesis of proliferative vitreoretinal disorders.

METHODS

In a prospective study of 101 consecutive patients, vitreous and paired serum samples were obtained from 38 patients with rhegmatogenous retinal detachment complicated by proliferative vitreoretinopathy, 25 patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy, and 38 patients with proliferative diabetic retinopathy. Gelatinase activities were determined by quantitative zymography.

RESULTS

All vitreous samples contained comparable levels of the constitutive gelatinase A. Inducible gelatinase B was detected in eight (32%) of 25 vitreous samples from patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy (mean +/- SD, 319.5 +/- 521.0 scanning units), in 17 (44.7%) of 38 vitreous samples from patients with proliferative vitreoretinopathy (560.6 +/- 718.9 scanning units), and in 34 (89.5%) of 38 vitreous samples from patients with proliferative diabetic retinopathy (1,707.2 +/- 1,220.3 scanning units). The incidence of detection of gelatinase B in proliferative diabetic retinopathy cases was significantly higher than it was in rhegmatogenous retinal detachment with no proliferative vitreoretinopathy and proliferative vitreoretinopathy cases (P < .001). Gelatinase B levels in the vitreous samples of patients with proliferative diabetic retinopathy were higher than the levels found in patients with rhegmatogenous retinal detachment with no proliferative vitreoretinopathy and in patients with proliferative vitreoretinopathy (P = .0152). Gelatinase A was detected in all the tested sera, whereas none of the tested paired serum samples contained detectable gelatinase B activity.

CONCLUSIONS

Gelatinase B may play an important role in extracellular matrix degradation associated with neovascularization in proliferative diabetic retinopathy.

Risk factors for proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is one of the major causes of failure in retinal detachment surgery. To prevent PVR, it is necessary to determine factors predisposing its development. In primary PVR, large retinal tears, long duration of retinal detachment, vitreous hemorrhages, aphakia and choroidal detachment were demonstrated as clinical risk factors for PVR. In postoperative PVR, it was revealed that large breaks, pre- and postoperative choroidal detachment, minor intra- or postoperative hemorrhages, signs of uveitis, extensive retinal detachment, vitrectomy, cryopexy, air injection and preoperative PVR were risk factors for PVR by multivariate analysis. Almost all risk factors for PVR are associated with intravitreal dispersion of retinal pigment epithelial (RPE) cells or breakdown of the blood-ocular barrier which are prerequisite to development of PVR.

Monocyte chemotactic protein-1 in proliferative vitreoretinal disorders

PURPOSE

To investigate whether the chemokines monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) are involved in the pathogenesis of proliferative vitreoretinal disorders and to study their possible interaction with IL-6.

METHODS

In a prospective study of 125 consecutive patients (125 eyes), vitreous and paired serum samples were obtained and were assayed for MCP-1 and IL-8. Levels of IL-6 were determined by proliferation of the IL-6-dependent hybridoma cell line 7TD1.

RESULTS

Monocyte chemotactic protein-1 was detected in 13 (48%) of 27 vitreous samples from patients with retinal detachment, in five (63%) of eight samples from patients with macular pucker, in 31 (72%) of 43 samples from patients with proliferative vitreoretinopathy, and in 32 (76%) of 42 samples from patients with proliferative diabetic retinopathy, but not in samples from five patients with idiopathic epiretinal membrane. There was a significant (P = .049) correlation between the incidence of MCP-1 detection in retinal detachment, macular pucker, and proliferative vitreoretinopathy groups and the severity of proliferation. Interleukin-8 was detected in two vitreous samples from eyes with retinal detachment, in two samples from eyes with proliferative vitreoretinopathy, and in three samples from eyes with proliferative diabetic retinopathy. Monocyte chemotactic protein-1 levels in the vitreous samples were positively correlated with IL-6 levels (r = .31, P = .01). Interleukin-6 levels were significantly (P = .0097) greater in vitreous samples with than without detectable levels of MCP-1.

CONCLUSION

Monocyte chemotactic protein-1 is present in a substantial percent of vitreous samples from eyes with proliferative vitreoretinal disorders and may help in stimulating the infiltration of monocytes and macrophages into eyes with these disorders.

Non-vascular vitreoretinopathy: the cells and the cellular basis of contraction

BACKGROUND

We consider epiretinal membrane in terms of the two repair processes of gliosis and fibrosis and look at the cellular basis of contraction.

METHODS

Pathological material removed at surgery was examined by a range of morphological procedures. Cultures of fibroblasts, retinal pigment epithelium cells and retinal glia were subjected to bioassays which relate to behavioural activities in scar formation.

RESULTS AND CONCLUSIONS

Our findings highlight the importance of activities such as migration and adhesion in the formation of epiretinal membranes, and also show that these activities are central to our understanding of contraction.

Conjunctiva and subconjunctival tissue in primary open-angle glaucoma after long-term topical treatment: an immunohistochemical and ultrastructural study

BACKGROUND

Primary open-angle glaucoma is commonly treated with long-term hypotensive medical therapy. When this approach becomes inadequate, therapy proceeds with surgery. The present study investigates morphological changes in the conjunctival and subconjunctival tissues induced by short- and long-term topical medical therapy of primary open-angle glaucoma.

METHODS

Comparisons were made between biopsy specimens from glaucomatous patients, who received specific eyedrop therapy (timolol and pilocarpine) for various periods of time, and control patients with no conjunctival pathology or topical treatment. Histological, immunohistochemical and ultrastructural parameters were investigated.

RESULTS

The morphometric analysis of histological sections and immunohistochemistry (anti-fibronectin antibody) in medium- and long-term therapy patients showed: (a) significant increases in the thickness and number of epithelial cell layers; (b) significant increases in the fibroblast density in both subepithelial and deep connective tissue; and (c) a more compact connective tissue, richer in collagen fibers arranged in whirls, with some inflammatory elements. These findings were confirmed by the ultrastructural analysis. In the same patients, the other immunohistochemical parameters investigated (anti-HLA-DR, anti-CD1a, anti-CD4, anti-CD8, anti-IL2 and C3b antibodies) revealed a tendency to chronic inflammation. Following specific surgery, this tendency manifested itself in a diffuse immune response, especially in those patients who underwent medium- and long-term medical therapy.

CONCLUSION

According to these results, antiglaucomatous surgery should be rehabilitated and considered as an alternative to long-term medical therapy in the first-instance treatment of primary open-angle glaucoma.

Effect of leukopenia on experimental post-traumatic retinal detachment

Macrophages are invariably present in the intraocular membranes of patients with traumatic proliferative vitreoretinopathy (PVR). There are two sources from which these macrophages could be recruited: adjacent tissues and the systemic circulation. In the study described herein, the role of circulating white blood cells and monocytes in experimental, traumatic PVR was studied. The circulating white blood cells of 20 rabbits were depleted by intravenous injection of strontium-89. Posterior perforating eye injury with subsequent intravitreal injection of autologous whole blood or autologous activated macrophages was then performed on these leukopenic animals. The experiments demonstrated that severe bone marrow depression reduced significantly the incidence of retinal detachments in eyes receiving whole blood, and reduced the severity of retinal detachments in eyes injected with activated macrophages. An association between the degree of leukopenia, monocytopenia, and protection from retinal detachment was demonstrated. These results support the hypothesis that macrophage infiltration is an important component of intraocular cellular proliferation, but does not exclude the role of other types of white blood cells in the pathogenesis of PVR.

Proliferative vitreoretinopathy: an examination of the involvement of lymphocytes, adhesion molecules and HLA-DR antigens

This paper addresses the molecular basis of interactions between leucocytes, other cells in the vitreoretinal environment and extracellular matrix that may underlie the pathogenesis of proliferative vitreoretinopathy. In this study we report the expression of adhesion molecules (CD11a, CD11c, CD18 and ICAM-1), lymphocyte surface markers (CD3, CD4, CD8 and CD22) and HLA-DR molecules in 25 epiretinal membranes obtained from eyes undergoing vitrectomy for the treatment of retinal detachment complicated by epiretinal membrane formation. Retinas from normal cadaveric eyes were used as controls. The results showed that cells expressing the adhesion molecules CD11a, CD11c and CD18 were present in 5 of 25, 17 of 25 and 11 of 23 membranes, respectively. Cells stained with antibodies against intracellular adhesion molecule 1 (ICAM-1) were observed in 24 of 25 membranes, whilst HLA-DR positive cells were seen in all membranes investigated. Immunohistochemical staining revealed that the molecules ICAM-1 or HLA-DR were not only expressed on inflammatory cells but also distributed within the extracellular matrix in several specimens. Lymphocytes expressing CD3 markers were present in 12 of 25 membranes, whilst T lymphocytes expressing CD4 and CD8 markers were observed in 5 of 18 and 12 of 24 membranes, respectively. In contrast, B lymphocytes expressing CD22 molecules were not found in any of the membranes. Leucocyte surface molecules were not expressed in control cadaveric retinas, although occasional cells expressing ICAM-1 were identified in the inner plexiform layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Inflammatory cells in proliferative vitreoretinopathy subretinal membranes

BACKGROUND

The inflammatory cell content of subretinal membranes occurring in proliferative vitreoretinopathy (PVR) has not yet been well characterized. This study was undertaken to investigate the inflammatory cells present in PVR subretinal membranes.

METHODS

Eight subretinal membranes obtained surgically from eyes with PVR complicating rhegmatogenous retinal detachment were studied immunohistochemically using the avidin-biotin complex technique and a panel of monoclonal and polyclonal antibodies.

RESULTS

T lymphocytes were found in five of the eight subretinal membranes. CD4+ T cells were demonstrated in four and CD8+ T cells in one of the membranes. T cells bearing the interleukin 2 receptor were found in two of four membranes studied. Macrophages were found in four membranes. No B lymphocytes or neutrophils were demonstrated, and there were no significant deposits of complement or immunoglobulins. Expression of the MHC class II antigen HLA DR was consistently found in frozen specimens. Glial cells and retinal pigment epithelial cells also were present in the membranes, often adjacent to T cells, although overall no obvious relationship was found between glial or retinal epithelial cells and T cells.

CONCLUSION

The findings indicate that T lymphocytes are present in PVR subretinal membranes and have the potential to interact with other cell types in the pathogenesis of this condition.

Traction retinal detachment. XLIX Edward Jackson Memorial Lecture

This review had two main objectives. The first goal was to attempt to define a final common pathway for traction retinal detachment. To illustrate this, I considered the following three common clinical entities: penetrating ocular trauma, proliferative vitreoretinopathy, and proliferative diabetic retinopathy. My second goal was to emphasize the role of research in developing a rational approach to treatment. To illustrate the second goal, I reviewed the contributions from three realms of research--laboratory, animal, and clinical research--examining their interactions and considering their roles in our current understanding and management of these clinical entities.

Immunopathological findings in conjunctival cells using immunofluorescence staining of impression cytology specimens

The conventional technique of impression cytology provides a non-invasive method for the evaluation of conjunctival epithelium alterations. Using indirect immunofluorescence procedures two inflammatory markers, class II MHC antigens HLA DR and the receptor to IgE (CD23), were sought in impression cytology specimens obtained from 80 patients. In normal subjects conjunctival epithelial cells did not show any reactivity. Only scattered dendritic cells were found to express class II antigens but not the receptor to IgE. In contrast patients with chronic conjunctivitis of various aetiologies, mainly infectious or allergic, had 40-100% of brightly positive conjunctival cells for one or both antigens. In these cases epithelial cells and goblet cells reacted similarly. Twenty four eyes in 12 patients with idiopathic dry eye syndrome disclosed results similar to those from normal conjunctival specimens. However 18 other specimens from patients suffering from idiopathic tear deficiency but undergoing multiple substitutive treatments for dry eye had moderate to strong positivity for HLA DR and/or the receptor to IgE (20-100% of cells). As these results were independent of the degree of squamous metaplasia the expression of these membrane markers may reflect local inflammation in addition to tear deficiency, possibly due to sensitisation to the eye drops used. These immunocytological techniques thus provide useful methods of investigating conjunctival inflammation and allergy. They may constitute valuable aid in the diagnosis and appropriate treatment of ocular surface disorders.

Proliferative vitreoretinopathy. Lymphocytes in epiretinal membranes

BACKGROUND

To investigate the potential contribution of inflammatory and immune-mediated processes contributing to the pathogenesis of proliferative vitreoretinopathy (PVR), an immunohistochemical study was undertaken to characterize the infiltrating inflammatory cells in epiretinal membranes surgically removed from the eyes of patients with PVR.

METHODS

Twenty-one epiretinal membranes obtained surgically from eyes with PVR complicating rhegmatogenous retinal detachment were studied immunohistochemically using the ABC technique and a panel of monoclonal and polyclonal antibodies.

RESULTS

T lymphocytes were found in 18 of the 21 specimens and generally constituted a small percentage of the total cell number. CD4+ T cells were found in 14 of the 18 membranes containing T cells. Three of six frozen membranes contained T cells that were positive for the interleukin-2 receptor. In 5 of 16 membranes studied, cells positive for the macrophage/monocyte marker were found. No B lymphocytes or neutrophils were identified, and there were no deposits of complement or immunoglobulins. Positive staining for the class II MHC antigen HLA-DR was found in 7 of the 21 membranes, a result that was more consistent in frozen than in fixed tissues.

CONCLUSION

The study suggests that T lymphocytes are present in PVR epiretinal membranes and may be activated. These cells have the potential to play a role in the pathobiology of PVR.