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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.

Purpose: Uncontrolled coagulation reactions contribute to pathological fibroproliferation in several organs, and yet their role in proliferative vitreoretinopathy (PVR) remains to be elucidated. In this study, we evaluated the profibrotic effects of FXa in RPE cells and in a mouse model of PVR., Methods: FXa levels in the eyes of traumatic PVR patients and rabbit models of mechanical ocular trauma was measured by ELISA and immunohistochemistry. FXa-induced RPE EMT was assessed by examining cell proliferation, migration, tight junction changes, and expression of fibrotic markers. For in vivo study, FXa was injected into dispase-injured eyes, then intraocular fibrosis was evaluated by histological analysis and Western blotting. The therapeutic effect of FXa inhibitor was also examined in PVR mouse models., Results: Vitreous FXa were higher in patients with traumatic PVR compared to patients with macular hole. Moreover, expressions of FXa and PAR1 were found in the epiretinal membranes from traumatic PVR patients. Vitreous FXa were markedly increased after mechanical ocular trauma in rabbits. In vitro, FXa stimulated RPE EMT characterized as ZO-1 disruption, compromised cell polarity, and increased fibronectin expressions. Co-injection of FXa and dispase in mice induced more severely damaged retinal structures, and increased α-SMA expressions than FXa or dispase treatment alone. Oral FXa or thrombin inhibitors significantly blocked intraocular fibrosis in PVR mouse models. FXa promoted phospho-activation of p38 in ARPE19 cells, which was dependent on PAR1. Moreover, TGF-βR inhibitor also significantly alleviated FXa-induced intraocular fibrosis in mice., Conclusions: FXa promotes intraocular fibrosis in mice via mechanisms involving RPE activation.

Purpose: The purpose of this study was to develop a method for isolating, culturing, and characterizing cells from patient-derived membranes in proliferative vitreoretinopathy (PVR) to be used for drug testing., Methods: PVR membranes were obtained from six patients with grade C PVR. Membrane fragments were analyzed by gross evaluation, fixed for immunohistologic studies to establish cell identity, or digested with collagenase II to obtain single cell suspensions for culture. PVR-derived primary cultures were used to examine the effects of methotrexate (MTX) on proliferation, migration, and cell death., Results: Gross analysis of PVR membranes showed presence of pigmented cells, indicative of retinal pigment epithelial cells. Immunohistochemistry identified cells expressing α-smooth muscle actin, glial fibrillary acidic protein, Bestrophin-1, and F4/80, suggesting the presence of multiple cell types in PVR. Robust PVR primary cultures (C-PVR) were successfully obtained from human membranes, and these cells retained the expression of cell identity markers in culture. C-PVR cultures formed membranes and band-like structures in culture reminiscent of the human condition. MTX significantly reduced the proliferation and band formation of C-PVR, whereas it had no significant effect on cell migration. MTX also induced regulated cell death within C-PVR as assessed by increased expression of caspase-3/7., Conclusions: PVR cells obtained from human membranes can be successfully isolated, cultured, and profiled in vitro. Using these primary cultures, we identified MTX as capable of significantly reducing growth and inducing cell death of PVR cells in vitro.

Purpose: Retinal vascular occlusions in sickle cell anemia patients cause tissue ischemia and the release of angiogenic mediators that promote the development of retinal neovascularization, initiating proliferative sickle retinopathy (PSR). Laser photocoagulation (LPC) has emerged as the most common treatment for PSR. Nonetheless, only two randomized controlled clinical trials have evaluated the use of LPC for PSR, and both failed to definitively demonstrate efficacy of this approach. This may be due to a lack of knowledge regarding the appropriate location for placement of laser coagulations in PSR eyes. To help address this question, we examined the expression of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) in PSR eyes., Methods: The expression pattern of HIF-1α and VEGF in PSR (n = 5) and control (n = 3) eyes was examined by immunohistochemistry in different retinal regions defined by the presence or absence of retinal vessels., Results: Hypoxia-inducible factor 1α and VEGF were expressed in the inner retina of 5/5 untreated PSR eyes adjacent to retinal neovascularization; expression of HIF-1α was not detected (and VEGF only lightly detected) in normal retinal and choroidal vasculature of 3/3 control eyes. Hypoxia-inducible factor 1α and VEGF were strongly expressed in retinal cells within avascular (nonperfused) retina, anterior to the boundary between perfused and nonperfused retina, as well as in posterior ischemic retina in the presence or absence of neovascular sea fans., Conclusions: If the goal of LPC in PSR is to quench the expression of HIF-1-driven angiogenic mediators, our results support broad application of peripheral laser for its treatment.

Purpose: Previous studies have shown that vitreous stimulates degradation of the tumor suppressor protein p53 and that knockdown of phosphatidylinositol 5-phosphate 4-kinases (PI5P4Kα and -β) abrogates proliferation of p53-deficient cells. The purpose of this study was to determine whether vitreous stimulated expression of PI5P4Kα and -β and whether suppression of PI5P4Kα and -β would inhibit vitreous-induced cellular responses and experimental proliferative vitreoretinopathy (PVR)., Methods: PI5P4Kα and -β encoded by PIP4K2A and 2B, respectively, in human ARPE-19 cells were knocked down by stably expressing short hairpin (sh)RNA directed at human PIP4K2A and -2B. In addition, we rescued expression of PI5P4Kα and -β by re-expressing mouse PIP4K2A and -2B in the PI5P4Kα and -β knocked-down ARPE-19 cells. Expression of PI5P4Kα and -β was determined by Western blot and immunofluorescence. The following cellular responses were monitored: cell proliferation, survival, migration, and contraction. Moreover, the cell potential of inducing PVR was examined in a rabbit model of PVR effected by intravitreal cell injection., Results: We found that vitreous enhanced expression of PI5P4Kα and -β in RPE cells and that knocking down PI5P4Kα and -β abrogated vitreous-stimulated cell proliferation, survival, migration, and contraction. Re-expression of mouse PIP4Kα and -β in the human PI5P4Kα and -β knocked-down cells recovered the loss of vitreous-induced cell contraction. Importantly, suppression of PI5P4Kα and -β abrogated the pathogenesis of PVR induced by intravitreal cell injection in rabbits. Moreover, we revealed that expression of PI5P4Kα and -β was abundant in epiretinal membranes from PVR grade C patients., Conclusions: The findings from this study indicate that PI5P4Kα and -β could be novel therapeutic targets for the treatment of PVR.

Purpose: To investigate the effect of thrombin on the proliferation of human Müller glial cells (MCs) and define the possible signaling mechanisms involved in this process., Methods: Protease-activated receptor (PARs 1-4) expression was analyzed using RT-PCR and Western blot in the MIO-M1 Müller cell line (MC). Müller cell proliferation was assessed by the MTS reduction method. Wound healing and immunoreactivity to Ki67 antigen were used to dissociate proliferation and migration. Cell migration was examined using transwell migration assays. The involvement of extracellular signal-regulated kinase (ERK1/2) phosphorylation/activation in thrombin-induced human MC proliferation was determined by Western blot. Intracellular pathways involved in ERK1/2 activation were analyzed by pharmacologic inhibition., Results: We first demonstrated that human MCs express PARs 1 to 4. Our results show that thrombin dose-dependently stimulates MC proliferation by 44%, with a calculated Ec50 of 0.86 nM. Müller cell maximal proliferation required sustained thrombin treatment for 72 hours, in contrast to our previous findings in RPE cells showing maximal thrombin-induced proliferation at 24-hour stimulation. We demonstrate that thrombin induces MC cell proliferation through the Ras-independent activation of the Raf/MEK/ERK cascade, under the control of protein kinase C (PKC)-ζ., Conclusions: The breakdown of blood-retina barrier (BRB) exposes MCs to thrombin contained in serum. Our findings further strengthen the critical involvement of thrombin in the development of proliferative retinopathies and may provide pharmacologic targets for the prevention or treatment of these diseases.

Purpose: To identify inflammatory cytokines significantly elevated and independent of VEGF levels in the vitreous of proliferative diabetic retinopathy (PDR) patients that may serve as novel diagnostic factors or therapeutic targets., Methods: Thirty-nine cytokines and chemokines were measured from the vitreous of 72 patients undergoing vitrectomy (29 controls and 43 PDR) via a magnetic bead-based immunoassay. Patient information, including sex, age, history of smoking, cancer diagnosis and treatment, and presence of diabetes and hypertension were also collected. Univariate and multivariate logistic regression analyses were performed to assess the association of cytokine concentrations and patient demographics with disease., Results: Nineteen cytokines were significantly elevated in the vitreous of PDR patients compared with controls, including five novel cytokines that have not previously been associated with PDR: sCD40L, GM-CSF, IFNα2, IL-12p40, and MCP-3. Sixteen cytokines were found to be statistically independent of VEGF. Of these, 14 show a statistically significant interaction with VEGF, while two do not. With regards to patient demographics, age and hypertension were statistically significant risk factors with the odds of disease decreasing with increasing age and increasing 3-fold for hypertensive patients., Conclusions: This is the first report of a comprehensive multiplex analysis to identify novel VEGF-independent cytokines associated with PDR. Of the 39 inflammatory cytokines tested, 16 are predictive of disease risk, independent of VEGF levels. These PDR-associated cytokines represent potential targets in the treatment of PDR, both in conjunction with anti-VEGF therapy, as well as for patients that are nonresponders to such therapy.

Purpose: To develop a large animal model of proliferative vitreoretinopathy (PVR) in the swine to eventually study disease pathophysiology, as well as novel therapies., Methods: PVR was induced in domestic swine by creation of a posterior vitreous detachment, creation of a retinal detachment by the injection of subretinal fluid, and intravitreal injection of green fluorescent protein-positive retinal pigment epithelial (GFP+ RPE) cells. Control eyes had the same surgical procedures without RPE cell injection. PVR was clinically graded on days 3, 7, and 14. Animals were euthanized on day 14, and enucleated eyes were analyzed by light microscopy and immunohistochemistry., Results: Injection of GFP+ RPE cells into the vitreous cavity produced localized, traction retinal detachments by day 14 in all eyes (14 of 14); in contrast, the retina spontaneously reattached by day 3 and remained attached in all control eyes (10 of 10). Contractile epiretinal membranes on the inner retinal surface that caused the traction retinal detachments consisted predominantly of GFP+ RPE cells. These cells stained positive for cytokeratin, confirming their epithelial origin, and also expressed α-SMA and fibronectin, markers for myofibroblasts and fibrosis, respectively., Conclusions: We established a swine PVR model that recapitulates key clinical features found in humans and, thus, can be used to study the pathophysiology of PVR, as well as new novel therapies. GFP+ RPE cells injected into the vitreous cavity formed contractile membranes on the inner retinal surface and caused localized traction retinal detachments.

Purpose: Interleukin (IL)-6, a multifunctional cytokine with regulatory functions in wound healing, and several chemokines have been implicated in the pathogenesis of proliferative vitreoretinopathy (PVR) after rhegmatogenous retinal detachment (RRD). The exact role of these chemokines, their correlation with IL-6 after primary RRD, and their association with the future development of PVR are not yet known., Methods: A multiplex immunoassay was used to determine levels of 15 different chemokines and IL-6 in subretinal fluid samples obtained during scleral buckling surgery for primary RRD. Samples from patients with preoperative uveitis, preoperative trauma, or preoperative vitreous hemorrhage were excluded. Patients who developed a redetachment due to postsurgical PVR within 2.5 months (n = 21) were compared with control subjects who had an uncomplicated retinal detachment during the overall follow-up period (n = 54). Control subjects were matched for sex, age, and storage time., Results: Levels of IL-6 (P = 0.001), MIF (P = 0.016), CCL2 (P = 0.041), CCL11 (P = 0.012), CCL17 (P = 0.003), CCL18 (P = 0.007), CCL19 (P < 0.001), CCL22 (P < 0.001), CXCL8 (P = 0.027), CXCL9 (P = 0.007), and CXCL10 (P = 0.002) were significantly higher in patients who developed postoperative PVR after primary RRD than in patients with uncomplicated retinal detachment. A significant positive correlation was observed between IL-6 and both CCL22 (r = 0.538; P < 0.0001) and CXCL8 (r = 0.645; P < 0.0001)., Conclusions: Various chemokines and IL-6 are upregulated in patients in whom fibrotic membranes develop after primary RRD repair and may therefore be involved in the future development of postoperative PVR.

Purpose: To explore the role of integrin alpha5beta1 in proliferative vitreoretinopathy (PVR) pathogenesis by evaluating the expression alpha5beta1 on ARPE-19 cells and patient proliferative membranes, quantifying the inhibitory effects of JSM6427 (a small molecule alpha5beta1 inhibitor) on ARPE-19 cell adhesion and migration, and assessing the therapeutic potential of JSM6427 in a rabbit retinal detachment model., Methods: Expression of alpha5beta1 was evaluated on activated ARPE-19 cells by flow cytometry and on PVR membranes by immunohistochemistry. ARPE-19 cells were used in fibronectin-dependent adhesion and migration assays with various concentrations of JSM6427; IC(50) was calculated. In the rabbit model, eyes were intravitreally injected with vehicle or JSM6427 on day 0 or 1 after retinal detachment; BrdU was administered intravitreally on day 3, and retinal tissues were harvested on day 3 (4 hours later) or 7. Retinal scarring, cellular proliferation, and inflammatory responses were quantified, and retinal morphology was analyzed in retinal sections., Results: Activated ARPE-19 cells and PVR membranes expressed high levels of alpha5beta1; expression was low in control eyes. JSM6427 provided a dose-dependent blockade of ARPE-19 cell adhesion to fibronectin (IC(50), 7.1 +/- 2.5 microM) and inhibition of migration (IC(50), 6.0 +/- 4.5 microM). In the rabbit model, intravitreal injection of JSM6427 provided significant inhibition of proliferation of retinal cells (Müller cells, microglia, and macrophages) on days 3 and 7 after detachment and inhibition of inflammatory response and retinal scarring on day 7 after detachment., Conclusions: JSM6427 is a promising treatment for PVR, with data suggesting that inhibition of alpha5beta1-fibronectin interactions addresses multiple pathways involving retinal pigment epithelial, glial, and inflammatory cells.

Purpose: Machine learning techniques were used to identify which of 14 algorithms best predicts the genetic risk for development of proliferative vitreoretinopathy (PVR) in patients who are experiencing primary rhegmatogenous retinal detachment (RD)., Method: Data from a total of 196 single nucleotide polymorphisms in 30 candidate genes were used. The genotypic profile of 138 patients with PVR following primary rhegmatogenous RD and 312 patients without PVR RD were analyzed. Machine learning techniques were used to develop statistical predictive models. Fourteen models were assessed. Their reproducibility was evaluated by an internal cross-validation method., Results: The three best predictive models were the lineal kernel based on the Support Vector Machine (SMV), the radial kernel based on the SVM, and the Random Forest. Accuracy values were 78.4%, 70.3%, and 69.3%, respectively. The more accurate, although complex, algorithm uses 42 SNPs, whereas the simpler one uses only two SNPs, which makes them more suitable for routine diagnostic work. The radial kernel based on SVM uses 10 SNPs. The best individually predictor marker was rs2229094 in the tumor necrosis factor locus., Conclusion: Genetic variables may be useful to predict the likelihood of the development of PVR. The predictive capabilities of these models are as good as those observed with clinical approaches. These results need external validation to estimate the true predictive capability and select the most appropriate ones for clinical use.

Purpose: Transforming growth factor (TGF)-beta2 and hepatocyte growth factor (HGF) have been implicated in the pathogenesis of proliferative vitreoretinopathy (PVR) after retinal detachment surgery. The exact role of these factors in the early events, immediately after primary retinal detachment, is not yet known, and determining their roles was therefore the purpose of this study., Methods: Subretinal fluids were collected prospectively from 144 patients during surgery for scleral buckling. TGF-beta2 and HGF were measured with commercially available ELISA kits. Thirty patients in whom a redetachment caused by postoperative PVR developed, were compared with 114 patients with an uncomplicated retinal detachment. The controls included 18 vitreous samples from patients with macular hole or pucker. Multivariate regression analysis was used to compare the relative roles of growth factors and clinical factors in the development of PVR., Results: The median amount of subretinal TGF-beta2 was approximately two times lower in patients with postoperative PVR (1.9 ng/mL) than in the uncomplicated detachment group (3.3 ng/mL; P=0.002). TGF-beta2 levels in the PVR-positive group were similar to control vitreous levels (1.8 ng/mL). Subretinal HGF concentrations were not significantly different between the two groups of patients (PVR positive: 8.8 ng/mL; PVR negative: 8.9 ng/mL), but were higher than control vitreous levels (4.6 ng/mL; P=0.01). Stepwise multivariate logistic regression analysis revealed that of all factors under study, decreased TGF-beta2 content was the exclusive predictor of postoperative PVR (P=0.01)., Conclusions: High TGF-beta2 levels in subretinal fluid at the time of primary retinal detachment may protect a patient against subsequent development of PVR.

Purpose: To determine whether syngeneic retinal cells injected in the vitreous cavity of the rat are able to initiate a proliferative process and whether the ocular inflammation induced in rats by lipopolysaccharide (LPS) promotes this proliferative vitreoretinopathy (PVR)., Methods: Primary cultured differentiated retinal Müller glial (RMG) and retinal pigmented epithelial (RPE) cells isolated from 8 to 12 postnatal Lewis rats were injected into the vitreous cavity of 8- to 10-week-old Lewis rats (10(5) cells/eye in 2 microlieter sterile saline), with or without the systemic injection of 150 microgram LPS to cause endotoxin-induced uveitis (EIU). Control groups received an intravitreal injection of 2 microliter saline. At 5, 15, and 28 days after cell injections, PVR was clinically quantified, and immunohistochemistry for OX42, ED1, vimentin (VIM), glial fibrillary acidic protein (GFAP), and cytokeratin was performed., Results: The injection of RMG cells, alone or in combination with RPE cells, induced the preretinal proliferation of a GFAP-positive tissue, that was enhanced by the systemic injection of LPS. Indeed, when EIU was induced at the time of RMG cell injection into the vitreous cavity, the proliferation led to retinal folds and localized tractional detachments. In contrast, PVR enhanced the infiltration of inflammatory cells in the anterior segment of the eye., Conclusions: In the rat, syngeneic retinal cells of glial origin induce PVR that is enhanced by the coinduction of EIU. In return, vitreoretinal glial proliferation enhanced the intensity and duration of EIU.

Purpose: The action of growth factors is thought to make a substantial contribution to the events leading to proliferative vitreoretinopathy (PVR). In this study, the importance of platelet-derived growth factor (PDGF) was tested in a rabbit model of PVR., Methods: The approach was to compare the extent of PVR induced by cells that do or do not express the receptors for PDGF and therefore differ in their ability to respond to PDGF., Results: Mouse embryo fibroblasts derived from PDGF receptor knock-out embryos that do not express either of the two PDGF receptors induced PVR poorly when injected into the eyes of rabbits that had previously undergone gas vitrectomy. Re-expression of the PDGF beta receptor in these cells did not improve the ability of the cells to cause PVR. In contrast, injection of cells expressing the PDGF alpha receptor resulted in stage 3 or higher PVR in 8 of 10 animals., Conclusions: These findings show that PDGF makes an important contribution to the development of PVR in this animal model. Furthermore, there is a marked difference between the two receptors for PDGF, and it is the PDGF alpha receptor that is capable of driving events that lead to PVR.

Purpose: Ablating and cutting vitreoretinal membranes using a 193-nm excimer laser-based microsurgical system., Methods: A 193-nm microsurgical system enables delivery of the beam into a fluid medium to cut preretinal and subretinal membranes. Two patients with proliferative diabetic retinopathy and one patient with proliferative vitreoretinopathy were treated with this new device., Results: Gentle ablation and cutting of the preretinal and subretinal membranes without exerting any traction on or apparent damage to the neighboring tissue was achieved., Conclusions: The technology is applicable to a variety of intraocular vitreoretinal surgical procedures.

Purpose: To measure vitreous levels of the soluble intercellular adhesion molecule (sICAM-1) in eyes with rhegmatogenous retinal detachment (RRD) complicated or uncomplicated by proliferative vitreoretinopathy (PVR) to investigate whether levels of this molecule related to history of previous retinal surgery or to the duration and severity of PVR., Methods: The authors measured vitreous sICAM-1 by enzyme-linked immunosorbent assay in 28 eyes with PVR and 35 eyes with uncomplicated RRD. Vitreous from 10 eyes with macular holes and from 12 cadaveric eye donors were used as control specimens., Results: Vitreous sICAM-1 levels were higher in the group with RRD complicated by PVR as a whole than in the group with RRD alone or in the control groups. In patients with no previous retinal surgery, there was no difference in vitreous sICAM-1 levels between the groups with RRD alone and RRD complicated by PVR. However, in patients who had undergone previous external surgery, those with PVR showed higher levels of vitreous sICAM-1 than those with RRD alone. In PVR, raised levels of sICAM-1 were associated preferentially with a history of previous vitrectomy as well as with a longer duration of the condition, although these levels were not related to the grade of PVR. In eyes with RRD alone, the levels of sICAM-1 were not enhanced with the duration of the detachment. Despite showing high vitreous levels of sICAM-1, patients with PVR did not exhibit increased serum levels of this adhesion molecule., Conclusions: The current observations suggest that those persons in whom PVR develops may have an impairment of the mechanisms that control the inflammatory response to retinal trauma. Persistently raised vitreous levels of sICAM-1 point to the continued operation of cytokine-mediated vascular reactions at the blood-retinal barrier.

Purpose: Integrin-mediated extracellular matrix (ECM) attachment plays an important role in vitreous contraction of retinal pigment epithelial (RPE) cells. Disintegrins, a group of Arg-Gly-Asp (RGD)-containing peptides from viper venom, are potential anti-adhesion agents that interfere with integrin-ECM binding. This study was performed to determine whether disintegrins were effective in inhibiting RPE cell-induced matrix attachment in vitro and tractional retinal detachment in a rabbit model in vivo., Methods: Two disintegrins, echistatin from viper Echis carinatus and flavoridin from Trimeresurus flavoviridis, were used. The expression of integrins on the surface of bovine and rabbit RPE cells was examined by indirect immunofluorescent stain with specific anti-integrin monoclonal antibodies. The inhibitory effect of disintegrins on RPE cell-mediated ECM attachment and vitreous contraction was evaluated with cell adhesion and vitreous contraction assays. In the in vivo model, rabbit eyes were injected intravitreously with either homologous rabbit RPE cells alone or together with disintegrins to induce tractional retinal detachment. The cytotoxic effect of disintegrins was examined with a cell proliferation assay using the alamar blue method. Retinal toxicity of disintegrins was evaluated with electroretinograms and histologic examination of the rabbit eyes., Results: Bovine and rabbit RPE cells showed the positive staining for the integrins alpha 2 beta 1 and alpha 5 beta 1 on cell surface. Disintegrins, echistatin, and flavoridin inhibited RPE cell attachment to the ECM. The potency of disintegrins was 150 to 300 times higher than that of Gly-Arg-Gly-Asp-Ser (GRGDS) peptide. The disintegrins also inhibited RPE cell-induced vitreous contraction in a dose-dependent manner, whereas the GRGDS peptide had no effect. In the in vivo experiment, echistatin (50 microgram/ml) or flavoridin (80 microgram/ml) significantly inhibited RPE cell-induced tractional retinal detachment compared with the control group at week 2 (P< 0.05) and week 4 (P< 0.01) after surgery. Disintegrins were nontoxic to RPE cells and rabbit retina as evaluated by cytotoxicity tests, electroretinograms, and histologic examinations., Conclusions: The disintegrins were effective in inhibiting RPE cell attachment to the ECM and vitreous contraction in vitro. They also were effective in suppressing RPE cell-induced tractional retinal detachment in the rabbit eyes. They were nontoxic. Disintegrins and their analogs might be potential anti-adhesion therapeutic agents in the treatment of proliferative vitreoretinopathy.

Purpose: Proliferative vitreoretinopathy occurs when cells migrate into the vitreous humor, where they proliferate and produce a membrane composed of extracellular matrix. Interleukin-1-beta (IL-1-beta) may be involved in these processes because it is chemotactic and mitogenic, and it stimulates metalloproteinase production. In the present study, the effects of intravitreally injected IL-1-beta on retinal membrane formation and the associated changes in metalloproteinase content of vitreous humor were examined., Methods: Rabbit eyes were injected with IL-1-beta in a buffer, with or without the prior creation of retinal holes. Control eyes received the buffer alone or no injection, with or without retinal holes. Animals were examined by slit lamp biomicroscopy and indirect ophthalmoscopy for 1 month. Zymography was performed on a portion of vitreous humor to assess collagenase content, and the remaining tissue was subjected to histologic analysis., Results: Intraocular IL-1-beta induced perilimbal vessel engorgement, keratic precipitates, synechiae, flare, lens deposits, optic disk hyperemia, and granulomatous formations that gradually subsided during the first week. Intravitreal injection of IL-1-beta in eyes with preexisting retinal holes additionally induced membrane formation. Zymographic analysis of vitreous humor from animals sacrificed 24 hours after IL-1-beta injection showed a 100-kd and a 65-kd gelatinase, whereas control vitreous humor contained predominantly a single gelatinase species of approximately 65 kd. Retinal holes did not affect IL-1-beta induction of the 100-kd gelatinase., Conclusions: IL-1-beta induces a 100-kd gelatinase in the vitreous humor and epiretinal membrane formation in eyes containing preexisting retinal holes. The presence of retinal holes and abnormal production of cytokines may lead to a cascade of events, including aberrant extracellular matrix remodeling, that result in proliferative diseases of the eye.