Retinal Pigment Epithelial Proliferation Research Articles

Modulation of Transgene Expression in Retinal Gene Therapy by Selective Laser Treatment

To develop a method for modulation of transgene expression in retinal pigment epithelium (RPE) using scanning laser that spares neurosensory retina. Fifteen pigmented rabbits received subretinal injection of recombinant adeno-associated virus (rAAV-2) encoding green fluorescent protein (GFP). GFP expression was measured using confocal scanning laser ophthalmoscopy (cSLO) fluorescence imaging and immunohistochemistry. To reduce the total expression in RPE by half, 50% of the transfected RPE cells were selectively destroyed by microsecond exposures to scanning laser with 50% pattern density. The selectivity of RPE destruction and its migration and proliferation were monitored using fluorescein angiography, spectral-domain optical coherence tomography (SD-OCT), and light, transmission, and scanning electron microscopy. 5-Bromo-2'-dioxyuridine (BrdU) assay was performed to evaluate proliferation of RPE cells. RPE cells were selectively destroyed by the line scanning laser with 15 μs exposures, without damage to the photoreceptors or Bruch's membrane. RPE cells started migrating after the first day, and in 1 week there was complete restoration of RPE monolayer. Selective laser treatment decreased the GFP fluorescence by 54% as compared to control areas; this was further decreased by an additional 48% following a second treatment 1 month later. BrdU assay demonstrated proliferation in approximately half of the RPE cells in treatment areas. Microsecond exposures produced by scanning laser destroyed RPE cells selectively, without damage to neural retina. Continuity of RPE layer is restored within days by migration and proliferation, but transgene not integrated into the nucleus is not replicated. Therefore, gene expression can be modulated in a precise manner by controlling the laser pattern density and further adjusted using repeated applications.

Imaging Retinal Pigment Epithelial Proliferation Secondary to PASCAL Photocoagulation In Vivo by Polarization-sensitive Optical Coherence Tomography

PurposeTo image the retinal pigment epithelium (RPE) after macular laser and to monitor healing responses over time in vivo in patients with diabetic maculopathy using polarization-sensitive optical coherence tomography (OCT).DesignProspective, nonrandomized clinical trial.MethodsIn this single-center trial (Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria), 13 patients (13 eyes) underwent grid photocoagulation for diabetic maculopathy. Retinal healing processes were continuously followed over the course of 3 months. A polarization-sensitive OCT prototype was used, allowing detection and measurement of the RPE changes based on their specific polarization-scrambling qualities.ResultsAfter 1 day, the intraretinal photocoagulation lesions were sharply demarcated, whereas RPE changes were rather subtle. At 1 week, all lesions exhibited traction of the inner retinal layers toward the RPE and loss of photoreceptor cells. In tissue-sensitive polarization-sensitive OCT imaging, polarization-scrambling columns were found at the level of the RPE. During follow-up, different healing responses were seen in the polarization-scrambling RPE layer, ranging from hyperproliferation to focal atrophy.ConclusionBecause of the properties of the polarization state of backscattered light, polarization-sensitive OCT revealed specific morphologic changes in the RPE and outer retinal layers secondary to retinal laser treatment undetectable with intensity-based spectral-domain OCT. The increase in polarization-scrambling tissue over the course of 3 months indicates a more intense healing reaction and proliferation of RPE cells than previously characterized in rodent studies.

Fundus autofluorescence and spectral-domain optical coherence tomography findings suggesting tissue remodelling in retinal pigment epithelium tear

AimTo study tissue remodelling and wound healing after retinal pigment epithelium (RPE) tears due to age-related macular degeneration.MethodsRetrospective longitudinal study of 36 eyes (33 patients) with RPE tears. Imaging was...

Interaction between VEGF and Calcium-Independent Phospholipase A2 in Proliferation and Migration of Retinal Pigment Epithelium

Purpose: Inhibition of VEGF in the eye is an important treatment modality for reducing proliferation and migration of retinal pigment epithelium (RPE) in age-related macular degeneration (AMD). Additionally, previous studies suggest calcium-independent phospholipase A2 group VIA (iPLA2-VIA) to be a potential regulator of cell proliferation and migration, and evidence show abundant expression of iPLA2-VIA in RPE cells. The aim of the present study was to evaluate the potential role of iPLA2-VIA in VEGF-induced proliferation and migration of RPE cells.Materials and methods: The human RPE cell line, ARPE-19, was used in all assays. To explore the role of iPLA2-VIA in VEGF-induced RPE proliferation and migration, iPLA2-VIA inhibition by the iPLA2-VIA specific inhibitor, bromoenol lactone, was done. RPE cell proliferation and migration were evaluated by measurements of incorporated radioactive thymidine in DNA and by a Boyden chamber technique, respectively. A luciferase assay monitored the VEGF-induced iPLA2-VIA transcriptional activity. Western blot analysis and an activity assay were used to detect the protein levels and activity of iPLA2-VIA respectively after treatment with VEGF.Results: RPE cells treated with VEGF showed significant increased proliferation and migration. Furthermore, inhibition of iPLA2-VIA significantly reduced the spontaneous proliferation and migration as well as the VEGF-induced proliferation and migration. Finally, inhibition of iPLA2-VIA reduced the VEGF-induced iPLA2-VIA-activity, -protein level, and -promoter activity.Conclusions: A significant interaction between VEGF and iPLA2-VIA in the regulation of RPE cells appears to be relevant in elucidating the exact mechanisms of action in the proliferative and migratory phenotype of RPE cells in AMD.

Effect of suppression of platelet-derived growth factor-α receptor expression with antisense oligonucleotide on proliferation and apoptosis of retinal pigment epithelium cell

Background Retinal pigment epithelial(RPE) cells can secrete platelet-derived growth factor (PDGF) and PDGF receptor(PDGFR).Studies have shown that PDGF plays a key role in the formation of proliferative vitreous retinopathy(PVR). Objective This study was to investigate the proliferation and apoptosis changes of RPE after blockage of the PDGFR-α expression by antisense oligonucleotide ( ASODN ) in vitro. Methods Human RPE cells strain was cultured in low glucose DMEM with 10％ fetal bovine serum.Logarithmic phase cells were collected and incubated in 96-well plate at the density of 5 × 105 cells/hole.PDGFR-α ASODN was transfected into RPE cells at different concentrations for 48 hours.The cells of the blank control group were regularly cultured without any transfection.The changes of PDGFR-α expression were detected by reverse transcription-polymerase chain reaction(RT-PCR),and the proliferation of RPE was detected by MTT as the A490 value.Hoechst 33258 fluorescence staining was used to determine the apoptosis of RPE.Flow cytometry method (FCM) was applied to detect the change of cell cycle and apoptosis rate of RPE cells. Results The A490 values of RPE cells were 1.45±0.12,1.07±0.06,0.65±0.05 in blank control group,1.0 μmol/L Lipo-ASODN group and 2.0 μmol/L Lipo-ASODN group with the significant difference(P=0.00 ),and that of 1.0 μmol/L Lipo-ASODN group and 2.0 μ mol/L Lipo-ASODN group were significantly lower than the blank control group ( P =0.00,0.00).Hoechst 33258 staining showed that the apoptosis cells were obviously more in Lipo-ASODN group compared with blank control group.PDGFR-α ASODN transfection induced an increase of percentage of RPE cells in G0/G1 phase( F =206.70,P =0.00),and the apoptosis rates in 1.0 μmol/L Lipo-ASODN group and 2.0 μmol/L Lipo-ASODN group were significantly enhanced in comparison with blank control group ( 37.8 ± 1.3 vs 10.5 ± 0.1,61.2 ± 1.9 vs 10.5 ± 0.1 ) ( F =1808.90,P =0.00 ).Expression intensity of PDGFR-α mRNA in RPE cells in Lipo-ASODN groups was lower. Conclusions Blocking the PDGFR-α expression with ASODN technology can suppress proliferation and induce apoptosis of RPE cells.Intensity of PDGFR-α mRNA expression in RPE cells is ASODN dose-dependent.ASODN targeted to PDGFR-α offers an experimental basis of the gene therapy for PVR. Key words: Platelet-derived growth factor-α receptor; Antisense oligonucleotide; Retinal pigment epithelial cell; Proliferation; Apoptosis

Leukocoria and Vitreous Hemorrhage as the Initial Manifestation of Sickle Retinopathy in a 3-Year, 6-Month-Old Child With Sickle Trait (AS)

The authors present the youngest reported child with proliferative sickle retinopathy. A 3-year, 6-month-old boy presented with leukocoria in the left eye, left esotropia, and dense free-floating white vitreous cells obscuring the fundus, suspicious for endophytic retinoblastoma. Ultrasonography depicted dense debris in the vitreous with no distinct calcific echo or retinal mass. Transcorneal, transzonular fine-needle aspiration biopsy of the vitreous confirmed the presence of dehemoglobinized vitreous red blood cells without tumor. The opposite eye showed peripheral retinal pigment epithelial proliferation and fibrosis with angiographic peripheral ischemia. Hemoglobin electrophoresis disclosed sickle trait (AS). The findings were classified as proliferative sickle cell retinopathy with vitreous hemorrhage in the left eye and non-proliferative sickle cell retinopathy in the right eye. Leukocoria generally raises warnings for retinoblastoma, but can also reflect chronic vitreous hemorrhage.

Enhanced retinal pigment epithelium regeneration after injury in MRL/MpJ mice

Regenerative medicine holds the promise of restoring cells and tissues that are destroyed in human disease, including degenerative eye disorders. However, development of this approach in the eye has been limited by a lack of animal models that show robust regeneration of ocular tissue. Here, we test whether MRL/MpJ mice, which exhibit enhanced wound healing, can efficiently regenerate the retinal pigment epithelium (RPE) after an injury that mimics the loss of this tissue in age-related macular degeneration. The RPE of MRL/MpJ and control AKR/J mice was injured by retro-orbital injection of sodium iodate at 20 mg/kg body weight, which titration studies indicated was optimal for highlighting strain differences in the response to injury. Five days after sodium iodate injection at this dose, electroretinography of both strains revealed equivalent retinal responses that were significantly reduced compared to untreated mice. At one and two months post-injection, retinal responses were restored in MRL/MpJ but not AKR/J mice. Bright field and fluorescence microscopy of eyecup cryosections indicated an initial central loss of RPE cells and RPE65 immunostaining in MRL/MpJ and AKR/J mice, with preservation of peripheral RPE. Phalloidin staining of posterior eye whole mounts confirmed this pattern of RPE loss, and revealed a transition region characterized by RPE cell shedding and restructuring in both strains, suggesting a similar initial response to injury. At one month post-injection, central RPE cells, RPE65 immunostaining and phalloidin staining were restored in MRL/MpJ but not AKR/J mice. BrdU incorporation was observed throughout the RPE of MRL/MpJ but not AKR/J mice after one month of administration following sodium iodate treatment, consistent with RPE proliferation. These findings provide evidence for a dramatic regeneration of the RPE after injury in MRL/MpJ mice that supports full recovery of retinal function, which has not been observed previously in mammalian eyes. This model should prove useful for understanding molecular mechanisms that underlie regeneration, and for identifying factors that promote RPE regeneration in age-related macular degeneration and related diseases.

Snail Involves in the Transforming Growth Factor β1-Mediated Epithelial-Mesenchymal Transition of Retinal Pigment Epithelial Cells

BackgroundThe proliferation of retinal pigment epithelium (RPE) cells resulting from an epithelial-mesenchymal transition (EMT) plays a key role in proliferative vitreoretinopathy (PVR), which leads to complex retinal detachment and the loss of vision. Genes of Snail family encode the zinc finger transcription factors that have been reported to be essential in EMT during embryonic development and cancer metastasis. However, the function of Snail in RPE cells undergoing EMT is largely unknown.Principal FindingsTransforming growth factor beta(TGF-β)-1 resulted in EMT in human RPE cells (ARPE-19), which was characterized by the expected decrease in E-cadherin and Zona occludin-1(ZO-1) expression, and the increase in fibronectin and α-smooth muscle actin (α-SMA) expression, as well as the associated increase of Snail expression at both mRNA and protein levels. Furthermore, TGF-β1 treatment caused a significant change in ARPE-19 cells morphology, with transition from a typical epithelial morphology to mesenchymal spindle-shaped. More interestingly, Snail silencing significantly attenuated TGF-β1-induced EMT in ARPE-19 cells by decreasing the mesenchymal markers fibronectin and a-SMA and increasing the epithelial marker E-cadherin and ZO-1. Snail knockdown could effectively suppress ARPE-19 cell migration. Finally, Snail was activated in epiretinal membranes from PVR patients. Taken together, Snail plays very important roles in TGF-β-1-induced EMT in human RPE cells and may contribute to the development of PVR.SignificanceSnail transcription factor plays a critical role in TGF-β1-induced EMT in human RPE cells, which provides deep insight into the pathogenesis of human PVR disease. The specific inhibition of Snail may provide a new approach to treat and prevent PVR.

Mature Peripheral RPE Cells Have an Intrinsic Capacity to Proliferate; A Potential Regulatory Mechanism for Age-Related Cell Loss

BackgroundMammalian peripheral retinal pigmented epithelium (RPE) cells proliferate throughout life, while central cells are senescent. It is thought that some peripheral cells migrate centrally to correct age-related central RPE loss.Methodology/Principal FindingsWe ask whether this proliferative capacity is intrinsic to such cells and whether cells located centrally produce diffusible signals imposing senescence upon the former once migrated. We also ask whether there are regional differences in expression patterns of key genes involved in these features between the centre and the periphery in vivo and in vitro. Low density RPE cultures obtained from adult mice revealed significantly greater levels of proliferation when derived from peripheral compared to central tissue, but this significance declined with increasing culture density. Further, exposure to centrally conditioned media had no influence on proliferation in peripheral RPE cell cultures at the concentrations examined. Central cells expressed significantly higher levels of E-Cadherin revealing a tighter cell adhesion than in the peripheral regions. Fluorescence-labelled staining for E-Cadherin, F-actin and ZO-1 in vivo revealed different patterns with significantly increased expression on central RPE cells than those in the periphery or differences in junctional morphology. A range of other genes were investigated both in vivo and in vitro associated with RPE proliferation in order to identify gene expression differences between the centre and the periphery. Specifically, the cell cycle inhibitor p27Kip1 was significantly elevated in central senescent regions in vivo and mTOR, associated with RPE cell senescence, was significantly elevated in the centre in comparison to the periphery.ConclusionsThese data show that the proliferative capacity of peripheral RPE cells is intrinsic and cell-autonomous in adult mice. These differences between centre and periphery are reflected in distinct patterns in junctional markers. The regional proliferation differences may be inversely dependent to cell-cell contact.

ATTACHMENT AND PROLIFERATION OF RETINAL PIGMENT EPITHELIAL CELLS ON SMALL INTESTINE SUBMUCOSA POWDER IMPREGNATED POLY(L-LACTIDE-CO-GLYCOLIDE) FILM

The retinal pigment epithelium (RPE) closely interacts with photoreceptors in the maintenance of visual function. The native RPEs exist as a monolayer structure and have a mottled brown color due to the presence of melanin and other pigments including lipofuscin granules, which accumulate with age. In age-related macular degeneration (AMD), RPE's dysfunction and changes in Bruch's membrane occur. Thus, small intestine submucosa/poly(lactic-co-glycolic acid) (SIS/PLGA) film is a biomimetic transplant consisting of a layer of healthy RPE cells cultured on a support membrane. The goals of this study were to evaluate the effects of attachment and proliferation of RPEs on SIS/PLGA films. Porcine SIS is an acellular tissue and widely used as a biomaterial without immunorejection responses, whereas PLGA is a biodegradable synthetic polymer with acceptable mechanical strength and well-controlled degradation rate. We fabricated SIS/PLGA films using 20 wt% of SIS. We measured MTT to confirm cellular adhesion of cell number attached on film at 1, 3, 5, and 7 days. Morphology of cellular adhesion on films was confirmed by scanning electron microscopy at 1, 3, and 7 days. Further, reverse transcription polymerase chain reaction (RT-PCR) was conducted to confirm messenger RNA expression of RPE65 as RPE's marker and expression of cytokeratin, and RPE65 were determined by AEC immunocytochemical staining. These results suggest that SIS provides suitable surface to RPEs.

Spatial and Spectral Imaging of Retinal Laser Photocoagulation Burns

To correlate in vivo spatial and spectral morphologic changes of short- to long-pulse 532 nm Nd:YAG retinal laser lesions using Fourier-domain optical coherence tomography (FD OCT), autofluorescence (AF), fluorescein angiography (FA), and multispectral imaging. Ten eyes with treatment-naive preproliferative or proliferative diabetic retinopathy were studied. A titration grid of laser burns at 20, 100, and 200 milliseconds was applied to the nasal retina and laser fluence titrated to produce four grades of laser lesion visibility: subvisible (SV), barely visible (BV, light-gray), threshold (TH, gray-white), and suprathreshold (ST, white). The AF, FA, FD-OCT, and multispectral imaging were performed 1 week before laser, and 1 hour, 4 weeks, and 3 and 6 months post-laser. Multispectral imaging measured relative tissue oxygen concentration. Laser burn visibility and lesion size increased in a linear relationship according to fixed fluence levels. At fixed pulse durations, there was a semilogarithmic increase in lesion size over 6 months. At 20 milliseconds, all grades of laser lesion were reduced significantly in size after 6 months: SV, 51%; BV, 54%; TH, 49%; and ST, 50% (P < 0.001), with retinal pigment epithelial proliferation and photoreceptor infilling. At 20 milliseconds, there was healing of photoreceptor inner segment/outer segment junction layers compared with 100- and 200-millisecond lesions. Significant increases in mean tissue oxygenation (range, four to six units) within the laser titration area and in oxygen concentration across the laser lesions (P < 0.01) were detected at 6 months. For patients undergoing therapeutic laser, there may be improved tissue oxygenation, higher predictability of burn morphology, and more spatial localization of healing responses of burns at 20 milliseconds compared with longer pulse durations over time.

A Nanofibrillar Surface Promotes Superior Growth Characteristics in Cultured Human Retinal Pigment Epithelium

Background: To evaluate the influence of surface topography on the proliferation of the retinal pigment epithelium (RPE) by comparing nanofibrillar and smooth substrates. Methods: Electrospun polyamide nanofibers (EPN) are an engineered surface mimicking native basement membranes. Commonly used plastic (polystyrene, PS) and glass substrates have a smooth topography. All were analyzed by scanning electron microscopy. RPE cultures were established from fetal and adult donors. Growth curves were established on the above substrates. Cell cycle and growth fractions were analyzed with 5-ethynyl-2′-deoxyuridine (EdU) and 4′,6-diamidino-2-phenylindole (DAPI). Results: At a magnification of ×5,000, EPN showed randomly overlapping fibers and pores. The surface of glass was slightly studded yet regular, in contrast to ideally smooth PS. Polygonal cells grew on nanofibers in a colony-like distribution, while randomly spread spindle-shaped cell morphologies were seen on smooth surfaces. This was observed at all donor ages. Initial proliferation rates were higher on EPN, and similar final cell densities were reached in all age groups, compared to an age-related decline on PS. EdU/DAPI revealed faster cell cycles on EPN. Growth fractions were higher and maintained longer on EPN. Observed substrate differences in growth behavior were statistically significant. Conclusion: Surface topography appears to induce distinct RPE proliferation characteristics.

The tight junction associated signalling proteins ZO-1 and ZONAB regulate retinal pigment epithelium homeostasis in mice.

Cell-cell adhesion regulates the development and function of epithelia by providing mechanical support and by guiding cell proliferation and differentiation. The tight junction (TJ) protein zonula occludens (ZO)-1 regulates cell proliferation and gene expression by inhibiting the activity of the Y-box transcription factor ZONAB in cultured epithelial cells. We investigated the role of this TJ-associated signalling pathway in the retinal pigment epithelium (RPE) in vivo by lentivirally-mediated overexpression of ZONAB, and knockdown of its cellular inhibitor ZO-1. Both overexpression of ZONAB or knockdown of ZO-1 resulted in increased RPE proliferation, and induced ultrastructural changes of an epithelial-mesenchymal transition (EMT)-like phenotype. Electron microscopy analysis revealed that transduced RPE monolayers were disorganised with increased pyknosis and monolayer breaks, correlating with increased expression of several EMT markers. Moreover, fluorescein angiography analysis demonstrated that the increased proliferation and EMT-like phenotype induced by overexpression of ZONAB or downregulation of ZO-1 resulted in RPE dysfunction. These findings demonstrate that ZO-1 and ZONAB are critical for differentiation and homeostasis of the RPE monolayer and may be involved in RPE disorders such as proliferative vitroretinopathy and atrophic age-related macular degeneration.

Integrin-α5 Mediates Epidermal Growth Factor-Induced Retinal Pigment Epithelial Cell Proliferation and Migration

Proliferation and migration of retinal pigment epithelial (RPE) cells play a crucial role in proliferative vitreoretinopathy (PVR)-related pathology. Cytokines, including EGF, can result in RPE cell activation and cause PVR. In this study, integrin-α₅ expression was first studied in PVR membranes by immunofluorescence. Then the effect of EGF on integrin-α₅ expression was determined by flow cytometry, Western blot analysis and the reverse-transcription polymerase chain reaction (RT-PCR) in the ARPE-19 cell line. Proliferation and migration of ARPE-19 cells were measured by the methylthiazolyldiphenyl-tetrazolium bromide and Boyden chamber assays. We found that a higher level integrin-α₅ was present at the RPE cell surface in PVR compared with normal retina. EGF could dose dependently increase integrin-α₅ mRNA and protein levels in vitro. EGF promoted ARPE-19 cell proliferation and migration. Neutralizing integrin-α₅ by specific anti-integrin-α₅ antibody abolished most of the effects of EGF. The study provided evidence that EGF might influence PVR by promoting integrin-α₅ expression and subsequent proliferation and migration of RPE.

RETINAL PIGMENT EPITHELIAL CHANGES IN CHRONIC VOGT-KOYANAGI-HARADA DISEASE

The purpose of this study was to determine whether fundus autofluorescence (FAF) and spectral domain-optical coherence tomography (SD-OCT) imaging allow better assessment of retinal pigment epithelium and the outer retina in subjects with chronic Vogt-Koyanagi-Harada disease compared with examination and angiography alone. A cross-sectional analysis of a series of seven consecutive patients with chronic Vogt-Koyanagi-Harada disease undergoing FAF and SD-OCT was conducted. Chronic disease was defined as duration of intraocular inflammation >3 months. Color fundus photographs were correlated to FAF and SD-OCT images. The images were later correlated to fluorescein angiography and indocyanine green angiography. All patients had sunset glow fundus, which resulted in no apparent corresponding abnormality on FAF or SD-OCT. Lesions with decreased autofluorescence signal were observed in 11 eyes (85%), being associated with loss of the retinal pigment epithelium and involvement of the outer retina on SD-OCT. In 5 eyes (38%), some of these lesions were very subtle on clinical examination but easily detected by FAF. Lesions with increased autofluorescence signal were seen in 8 eyes (61.5%), showing variable involvement of the outer retina on SD-OCT and corresponding clinically to areas of retinal pigment epithelium proliferation and cystoid macular edema. Combined use of FAF and SD-OCT imaging allowed noninvasive delineation of retinal pigment epithelium/outer retina changes in patients with chronic Vogt-Koyanagi-Harada disease, which were consistent with previous histopathologic reports. Some of these changes were not apparent on clinical examination.

Selective retina therapy (SRT) in patients with geographic atrophy due to age-related macular degeneration

For geographic atrophy (GA) due to age-related macular degeneration (AMD) there is so far no approved treatment option. Usually, increased autofluorescence (AF) levels of different patterns adjacent to the atrophic area indicate lipofuscin-laden retinal pigment epithelium (RPE) cells at a high risk for apoptosis. Herein, SRT was used to selectively treat these cells to stimulate RPE proliferation, in order to reduce or ideally stop further growth of the atrophic area. Six eyes of six patients with bilateral equally pronounced GA were treated by SRT, while the fellow eye served as control. Irradiation was performed using a prototype SRT laser (Medical Laser Center Lübeck, Nd:YLF laser; 527 nm; 200 ns/1.7 micros pulse duration; 30 repetitive pulses at 100 Hz). Test lesions with increasing energies were applied at the lower vessel arcade to determine the individual angiographic and ophthalmoscopic threshold radiant exposures. Treatment was then performed in the area of increased AF adjacent to the GA using energies between both thresholds. The GA progression rates of treated and fellow eyes were evaluated. After a 1-year follow-up, a progression of the atrophic area was observed in the treated eyes (0.7-8.0 mm(2)/yr, mean 3.0 mm(2)/yr; 46%/yr) whereas the progression rates of the fellow eyes were insignificantly lower (0.46-4.04 mm(2)/yr, mean 1.9 mm(2)/yr; 30%/yr; p = 0.134). The progression rate in the treated eyes of two patients increased significantly, while in the other four patients, the progression rates were nearly the same between both eyes. Moreover, one of these two eyes showed an unexpected RPE reaction after treatment, since all laser lesions led to RPE atrophy and thus an accelerated enlargement of the GA occurred. SRT in the hyperautofluorescent areas of GA was not able to stop or slow down the progression of GA. However, modified treatment strategies might be more promising, e.g. placing the spots outside the hyperautofluorescent areas where RPE apoptosis is postulated. Moreover, SRT studies on GA might be more successfully performed on specific subgroups of GA, based on autofluorescence and other findings.

Sympathetic ophthalmia manifesting with conjunctival chemosis

A 13-year-old girl was referred to us with the complaints of severe headache and decreased visual acuity (VA) in the right eye, of 1 week duration. She had a history of penetrating ocular trauma in the left eye 1 month earlier. Her best-corrected VA was counting fingers in the right eye and no light perception in the left eye. External examination revealed a massive inferior conjunctival chemosis bilaterally (Fig. 1a). Slitlamp examination of the right eye showed 0.5? cells, no corneal precipitates, and mild vitritis. There were a cloud cornea and an iris distortion, and no posterior segment structures were visible in the traumatized eye. Fundus examination of the right eye revealed focal yellow–white lesions at the level of the retinal pigment epithelium (RPE), multifocal serous retinal detachment (SRD), and hyperemic optic disc (Fig. 1b). Fluorescein angiography showed multifocal leaks at the level of the RPE with pooling of dye in the area of SRD (Fig. 1c). Ultrasonography of the right eye showed marked, diffuse choroidal thickening (3 mm), and diffuse retroscleral edema with T-sign in the peripapillary region (Fig. 1d). In the traumatized eye, there was choroidal and ciliary body detachment. Optical coherence tomography of the right eye showed SRD with subretinal septa. A diagnosis of SO was made, and the patient was treated with intravenous methylprednisolone (1 g/day for 3 consecutive days) followed by oral administration of prednisone (1.5 mg/kg). Three days after presentation, intraocular inflammation had improved and conjunctival chemosis had completely resolved. One week later, the chemosis had recurred and the SRD became more extensive and bullous. Cyclosporin (5 mg/kg/day) and then infliximab (5 mg/kg/ 0–2–4–8 weeks) were added. After a follow-up of 3 months, conjunctival chemosis had disappeared (Fig. 2a) and VA was 20/200. SRD had resolved, and there were subretinal fibrosis with RPE proliferation (Fig. 2b). Ultrasonography showed resolution of choroidal thickening and retroscleral edema (Fig. 2c). S. Attia S. Jenzeri I. Chtioui B. Jelliti S. Zaouali S. B. Yahia M. Khairallah (&) Department of Ophthalmology, Fattouma Bourguiba University Hospital, 5019 Monastir, Tunisia e-mail: moncef.khairallah@rns.tn

Soluble EphB4 Inhibition of PDGF-Induced RPE Migration In Vitro

EphB4 receptor (EphB4) and its ligand (EphrinB2) play an important role in the regulation of cell adhesion, growth, and migration. The purpose of this study was to determine the effects of EphB4 blockade by soluble EphB4 (sEphB4) on retinal pigment epithelial (RPE) cell migration and proliferation, induced by platelet-derived growth factor-BB (PDGF), and to establish its relevance to proliferative vitreoretinopathy (PVR). The expression of EphB4 and EphrinB2 in early-passage human RPE cells and in human PVR membranes was evaluated by confocal microscopy. The effect of sEphB4 (0.1-3 microg/mL) on PDGF (20 ng/mL)-induced RPE migration and proliferation was evaluated using a modified Boyden chamber assay and an MTT assay, respectively. Attachment to basement membrane matrix and fibronectin was assayed by MTT. Phosphorylation of FAK and p42/44 mitogen-activated protein kinase (MAPK) in retinal pigment epithelium was determined by Western blot analysis after exposure to sEphB4. The effect of sEphB4 on the phosphorylation of EphB4/EphrinB2 was demonstrated with the use of immunoprecipitation assays. EphrinB2 and EphB4 were expressed on human RPE cells in vitro and in cells within human PVR membranes. sEphB4 blocked EphB4 and EphrinB2 phosphorylation in RPE cells in vitro. sEphB4 reduced RPE migration in response to PDGF stimulation (P < 0.01). Similarly, sEphB4 inhibited RPE attachment and proliferation in a dose-dependent manner (P < 0.05). PDGF-induced phosphorylation of FAK and MAPK was inhibited by sEphB4. EphB4 and EphrinB2 are expressed in RPE cells and PVR membranes. sEphB4 inhibits PDGF-induced RPE cell attachment, proliferation, and migration. This effect may result from the inhibition of FAK and MAPK phosphorylation.

Calcium-independent phospholipase A 2 regulates retinal pigment epithelium proliferation and may be important in the pathogenesis of retinal diseases

Calcium-independent phospholipase A 2, group VIA (iPLA 2-VIA) is involved in cell proliferation. This study aimed to evaluate the role of iPLA 2-VIA in retinal pigment epithelium (RPE) cell proliferation and in retinal diseases involving RPE proliferation. A human RPE cell line (ARPE-19) was used to explore this role in vitro. Proliferating ARPE-19 cells had increased expression and activity of iPLA 2-VIA. iPLA 2-VIA was found in the nuclei of proliferating ARPE-19 cells, whereas in confluent ARPE-19 cells, with limited proliferation, iPLA 2-VIA was primarily found in the cytosol. Inhibition of iPLA 2-VIA decreased the rate of proliferation, whereas over expression of iPLA 2-VIA increased the rate of proliferation. Using an experimental porcine model of RPE proliferation we demonstrated significant nuclear upregulation of iPLA 2-VIA in proliferating RPE cells in vivo. We furthermore evaluated the expression of iPLA 2-VIA in proliferative vitreoretinopathy (PVR). PVR membranes revealed nuclear expression of iPLA 2-VIA in the RPE cells which had migrated and participated in the formation of the membranes. Overall, the present results point to an important role of iPLA 2-VIA in the regulation of RPE proliferation suggesting that iPLA 2-VIA may be considered as a possible pharmaceutical target in retinal diseases involving RPE proliferation and migration.

Fundus autofluorescence and fate of glycoxidized particles injected into subretinal space in rabbit age-related macular degeneration model

Abnormal fundus autofluorescence (FAF) is associated with the incidence or progression of dry and wet age-related macular degeneration (AMD). We previously developed a rabbit AMD model with drusen and type-1 choroidal neovascularization (CNV) that mimics the accumulation of lipofuscin using artificial glycoxidized particles. The objective of the current study was to investigate in vitro effects of glycoxidized particles on retinal pigment epithelial (RPE) cells, and the FAF and fate of injected particles in this model. Glycoxidized particles were prepared by a 4-day incubation of water-in-oil emulsions of serum albumin and glycolaldehyde to allow glycoxidation and consequent cross-linking. After particles were added in the culture medium of confluent human RPE cells, cell viability, adhesion activity, and proliferation activity were assessed by cell counting. In anesthetized rabbits, 250 microg of glycoxidized particles were injected into the subretinal space to induce experimental AMD. FAF measurement and angiography with sodium fluorescein and indocyanine green were performed periodically using the Heidelberg Retina Angiograph 2 (HRA2). The eyes enucleated, and the lung and the spleen, excised at week 4 or 12, were histologically evaluated by light and fluorescence microscopy. Glycoxidized particles phagocytosed did not impair the cell viability, adhesion, and proliferation of RPE cells, as compared with RPE cells in controls. HRA2 showed different patterns of abnormal FAF in the area with the implanted glycoxidized particles, similar to pathological FAF patterns in aging human eyes with or without AMD. Histologic examination showed accumulated glycoxidized particles and large lipofuscin granules with green autofluorescence in and under the RPE and at the margins of or beneath drusen, possibly associated with abnormal FAF. In addition, some particles were detected in the lung and the spleen. Glycoxidized particles phagocytosed might stay in RPE cells without any acute biological reaction. Our rabbit model of AMD simulated abnormal FAF patterns observed in aging human eyes with or without AMD. Glycoxidized particles phagocytosed by RPE cells could be deposited on Bruch's membrane in rabbits, possibly excreted in part into choroidal circulation. This model may be useful for understanding various patterns of abnormal FAF histologically, and for elucidating the pathogenesis of AMD.