Retinal pigment epithelium rescues vascular endothelium from retinoic acid-induced apoptosis

PURPOSE: To determine whether retinoids are capable of inducing vascular endothelial cell apoptosis and whether the presence of an intact RPE monolayer can block retinoid-induced vascular endothelial cell death. METHODS: Confluent fetal bovine aortic endothelial (FBAE) cells were incubated with various concentrations of all-trans or 9-cis retinoic acid (an analogue of 11-cis retinoic acid). Apoptosis rates were determined at 24 hours, and the effect of inhibition of protein synthesis and activation of protein kinase C on apoptosis was investigated by supplying culture medium with 0.1 mg/mL cycloheximide and 10 nM phorbol myristate acetate. To investigate the impact of RPE on retinoid-induced apoptosis, confluent FBAE cells were cultured with a confluent layer of RPE in inserts where retinoids were added to the upper compartment. A confluent bovine corneal endothelium monolayer was used as the control. The permeabilities of the RPE and bovine corneal endothelium monolayers to fluorescein (20 microg/mL) and 9-cis retinoic acid (3 x 10(-4) M) were also determined. RESULTS: 9-cis Retinoic acid induced higher rates of apoptosis in FBAE cells than did all-trans retinoic acid and the control (P = 0.004). This effect was dose-dependent, with an ED(50) of 1.4 microM (r = 0.99, P = 0.004). Cycloheximide did not inhibit 9-cis retinoic acid-induced apoptosis, but phorbol myristate acetate significantly decreased the apoptosis rate (P = 0.005). The presence of a confluent RPE monolayer reduced the 9-cis retinoic acid-induced apoptosis rate (P = 0.002), but the presence of a bovine corneal endothelial monolayer did not (P > 0.05). Both cell types established a similar diffusion barrier against fluorescein and 9-cis retinoic acid. CONCLUSIONS: 9-cis Retinoic acid is an important mediator of vascular endothelial apoptosis. A confluent monolayer of RPE can prevent endothelial cell apoptosis, and this effect is not due simply to establishment of a diffusion barrier by the RPE.     

视网膜色素上皮与新生血管的形成

新生血管的形成是许多眼底疾病的一个共同环节。视网膜色素上皮（ＲＰＥ）与新生血管的发生有着密切的关系。通过阐述视网膜色素上皮对新生血管发生的４个步骤，即血管外膜的降解、血管内皮细胞的迁移、血管内皮细胞的增生及新生血管成熟等的影响，回顾了视网膜色素上皮在眼底新生血管发生中的作用。阐明其在何种情况下促进新生血管的发生，或何种情况抑制新生血管的发生，以期为眼底新生血管疾病的治疗寻找出路     

Retinal pigment epithelium tears after intravitreal bevacizumab in pigment epithelium detachment

PURPOSE: To evaluate pigment epithelium detachment (PED) secondary to exudative age-related macular degeneration (AMD) treated with intravitreal injection of bevacizumab with regard to incidence of retinal pigment epithelium tears (RIPs). DESIGN: Retrospective, interventional case series. METHODS: Institutional study of 31 eyes with PED in exudative AMD receiving intravitreal bevacizumab. Main outcome measures were Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity, PED vascularization and size measured by angiography and optical coherence tomography (OCT) imaging, and incidence of RIP. RESULTS: Vision improved in six eyes and remained stable in 22 eyes (follow-up, 12.3 +/- 10.3 weeks). Twenty-eight eyes showed a vascularized PED. Four eyes (12.9%) experienced an RIP without vision loss. All RIP cases were vascularized in more than 50% of total lesion size. CONCLUSIONS: In short-term follow-up, the risk for RIP after bevacizumab injection in eyes with PED seems to be moderately, but not statistically significantly, increased in PED lesions vascularized more than 50%.     

Lycium barbarum polysaccharides protected human retinal pigment epithelial cells against oxidative stress-induced apoptosis

AIM: To investigate the protective effect and its mechanism of lycium barbarum polysaccharides (LBP) against oxidative stress-induced apoptosis in human retinal pigment epithelial cells. METHODS: ARPE-19 cells, a human retinal pigment epithelial cell lines, were exposed to different concentrations of H2O2 for 24h, then cell viability was measured by Cell Counting Kit-8 (CCK-8) assay to get the properly concentration of H2O2 which can induce half apoptosis of APRE-19. With different concentrations of LBP pretreatment, the ARPE-19 cells were then exposed to appropriate concentration of H2O2, cell apoptosis was detected by flow cytometric analysis. Expression levels of Bcl-2 and Bax were measured by real time quantitative polymerase chain reaction (RT-PCR) technique. RSULTS: LBP significantly reduced the H2O2-induced ARPE-19 cells’ apoptosis. LBP inhibited the H2O2-induced down-regulation of Bcl-2 and up-regulation of Bax. CONCLUSION: LBP could protect ARPE-19 cells from H2O2-induced apoptosis. The Bcl-2 family had relationship with the protective effects of LBP.     

Retinal pigment epithelium tears following intravitreal ranibizumab therapy

Two patients with choroidal neovascularization secondary to age-related macular degeneration (AMD) developed a retinal pigment epithelial (RPE) tear following intravitreal injection of ranibizumab. One patient developed the RPE tear within 2 weeks of the injection, the other within 6 weeks of a second injection. Both patients presented with vision loss of one line at diagnosis of the RPE tear. During long-term follow-up, visual acuity improved in one patient by one line and deteriorated in the second patient by three lines. RPE tears may occur after intravitreal injection of ranibizumab in patients with neovascular AMD, probably because of the rapid regression of the fibrovascular membrane.     

Retinal light damage reduces autofluorescent pigment deposition in the retinal pigment epithelium

Lipofuscin in the retinal pigment epithelium (RPE) is thought to be derived from phagocytosed photoreceptor outer segment disc membranes. Based on this hypothesis, one would predict that the rate of lipofuscin deposition in the RPE would be proportional to the density of photoreceptor cells in the retina. In previous studies it was demonstrated that specific loss of photoreceptor cells due to a genetic defect resulted in a substantial decrease in the rate of age-related lipofuscin accumulation in the RPE. In order to confirm that this decreased RPE lipofuscin deposition was directly related to reduced photoreceptor cell density, experiments were conducted to determine whether light-induced photoreceptor cell destruction affected RPE lipofuscin content. The effects of retinal light damage on RPE autofluorescent pigment accumulation resulting from both normal aging and vitamin E deficiency were examined. Starting immediately after weaning, albino Fisher 344 rats were fed diets either containing or lacking vitamin E. All animals were maintained on a 12 hr/12 hr light/dark cycle. During the light phases of the cycles, the cage illuminance for one-half the animals in each dietary group was 750 lux, while the remaining rats were exposed to a light level of 15 lux. Illumination was provided by 40 watt cool-white fluorescent lamps. After 17 weeks, rats in both dietary groups that were maintained under the higher light intensity had substantially reduced photoreceptor cell densities relative to animals in the same dietary group maintained under dim light conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Retinal pigment epithelium dystrophy in central serous detachment/of sensory epithelium

The incidence of central serous neuro-epithelial detachment in the population living in the health district Prague-10 was found to be one in 22.000 inhabitants a year. The cases were classified into three types:A. Inkblot diffusion 60%; B. upward diffusion 25%; C. congregation type 15%. The site of leakage was usually in the upper part of the detached retina or slightly below the horizontal line.Relapses were observed in 16 out of 79 patients, 20%, usually stemming from the original leak. The average re-attachment time was 98 days. In 10% a chronic course led to extensive dystrophy of the pigment epithelium.     

Retinal pigment epithelium decompensation. II. Laser treatment

Forty-one of 97 eyes with retinal pigment epithelium decompensation (RPED) were treated with monochromatic green argon laser photocoagulation to the focal area of RPE staining detected in the late fluorescein transit. Nineteen eyes were treated because of progressive visual deterioration. The other 22 eyes already had visual acuities of 20/50 or worse. Vision stabilized or improved in 34 eyes (82.9%) after an average of 1.6 years following treatment, compared with improvement in only 5 of 56 untreated eyes after an average follow-up period of 2.1 years. After an average follow-up of 7.1 years, 12 of 97 eyes with RPED developed choroidal neovascularization (9 spontaneously and 3 after photocoagulation) in the area where late RPE staining had been observed.     

Retinal pigment epithelium produces matrix metalloproteinases after laser treatment

PURPOSE: To evaluate production of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) after panretinal photocoagulation (PRP) of human retinal pigment epithelium (RPE) explants. METHODS: Treated explants were subjected to substrate zymography to differentiate MMP-2 from MMP-9 and dot immunoblot analysis to quantify MMP-3 and TIMP activity. Tritiated thymidine uptake by RPE cells was measured to document evidence of cellular division in the laser-treated versus control explants. RESULTS: We detected MMP-2, MMP-3, and TIMP-1. MMP-2 and MMP-3 secretion increased to twice the control values. TIMP decreased until day 4 and then increased by day 6. Tritiated thymidine uptake increased 2.5-fold until day 6, returning to baseline by day 8. CONCLUSION: PRP disturbs MMP/TIMP balance, inhibiting the initiation and maintenance required for active neovascularization. The efficacy of PRP may be due to changes in the expression pattern of metalloproteinases and inhibitors. This model elucidates the possible contribution of PRP to neovascularization regression by demonstrating the effect of laser on TIMP/MMP balance. The effects of PRP may be much more complex than currently understood and most likely involve more than vascular endothelial growth factor and other ischemia-related factors.     

Retinal stimuli can be restored after autologous transplant of retinal pigment epithelium and choroid in pigment epithelium tears

Purpose: To evaluate the functional and anatomical outcome of patients undergoing autologous transplant of retinal pigment epithelium (RPE) and choroid after RPE tear secondary to age‐related macular degeneration (AMD). Methods: Data from nine eyes of nine patients were analysed retrospectively. Examinations included fluorescein and indocyanine green angiography, fundus autofluorescence imaging, optical coherence tomography, microperimetry and determination of visual acuity (far and reading ability). Data regarding intraoperative and postoperative complications were recorded. Mean follow‐up time was 18 months (range 4 months to 5 years). Results: After surgery, far visual acuity improved or remained stable (±3 lines) in three of nine eyes and for the near visual acuity in three of nine eyes. Visual acuity decreased postoperatively at the last follow‐up in four eyes mainly because of postoperative complications, i.e. retinal detachment due to proliferative vitreoretinopathy, retinal artery occlusion, pucker and fibrosis of the graft. In one case, retinal stimuli were restored over the scotoma as seen in microperimetry. Conclusion: Autologous transplant of RPE and choroid is a therapy option for RPE tears. Retinal stimuli can be restored in selected cases. Numerous intra‐ and postoperative complications compromise the functional prognosis and outcome.     

Retinal pigment epithelium possesses both LDL and scavenger receptor activity

The lipid metabolism of photoreceptors depends in part on the retinal pigment epithelium (RPE). One aspect of cholesterol homeostasis in cultured bovine RPE was evaluated by measuring low-density lipoprotein (LDL) and scavenger receptor activity with [125I]-LDL and [125I]Ac-LDL, respectively. Incubation of RPE cells in the presence of increasing concentrations of LDL or Ac-LDL resulted in down-regulation of the LDL receptor but not the scavenger receptor, patterns consistent with the presence of both receptors on these cells. This receptor profile distinguishes the RPE cell from fibroblasts and indicates its similarity to macrophages and arterial endothelial cells.     

Retinal pigment epithelium wound healing in human Bruch's membrane explants

PURPOSE: To compare retinal pigment epithelium (RPE) resurfacing on the RPE basement membrane and inner collagenous layer (ICL) in human submacular Bruch's membrane explants. METHODS: Debridements were created in RPE-choroid-sclera explants (mean donor age 71.91 +/- 7.76 years) to create defects exposing the RPE basement membrane (RPEbm(+) defects), the ICL immediately below the RPE basement membrane (superficial ICL, [SICL]) or deeper layers of the ICL (DICL). Eleven pairs of eyes--four pairs with one eye having an RPEbm(+) defect and the fellow eye having an SICL defect and seven pairs with corresponding RPEbm(+) and DICL defects--were observed for 10 days by visualizing RPE ingrowth with 4',6'-diamino-2-phenylindole (DAPI) filters. At day 10, specimens were processed for scanning electron microscopy. RESULTS: Resurfacing of localized RPE defects occurred to some degree in all 11 pairs of eyes. No significant difference in the percentage of resurfacing of RPEbm(+) defects (67.35% +/- 18.82%) and SICL defects (64.26% +/- 16.07%) was observed although healing of the SICL showed more variability in the morphology of RPE cells migrating into the defect. Significant differences in healing were observed between pairs with RPEbm(+) defects versus DICL defects (84.07% +/- 15.35% and 54.00% +/- 14.54% resurfacing, respectively). RPE ingrowth into DICL defects exhibited the greatest morphologic variability. CONCLUSIONS: RPE basement membrane supports RPE resurfacing of localized RPE defects. The deeper portion of the ICL of aged submacular human Bruch's membrane does not support RPE resurfacing to the same extent as does the RPE basement membrane. The poor RPE resurfacing observed in DICL defects mimics the histopathological findings in patients with age-related macular degeneration after excision of choroidal new vessels.     

Retinal pigment epithelium cells can influence endothelial cell plasminogen activators

Endothelial cells from both human retinal microvessels (HME) and fetal bovine aortic endothelium (FBAE) were grown in aggregate cultures alone, or with either retinal pigment epithelium (RPE) cells or fibroblasts. The levels of plasminogen activator (PA) and plasminogen activator inhibitor (PAI) in the conditioned media of the various aggregate types were measured. High PA levels were detected in the conditioned medium of pure endothelial cell aggregates (equal to 140% and 124% of urokinase control for HME and FBAE, respectively), and high PAI levels were associated with pure RPE aggregates (inhibiting 93% of the urokinase control). The conditioned medium of pure fibroblast aggregates had very low levels of either PA or PAI. When RPE cells were aggregated with FBAE or HME cells into mixed (heterogenous) aggregates, the PA measured in the conditioned medium was equal to 22% and 30% of the urokinase control, respectively. The PA level in the conditioned medium of mixed fibroblast-FBAE cell aggregates was higher, 104% of the control, and the difference was statistically significant (P less than 0.001). Co-incubation of pure RPE aggregates with pure FBAE aggregates or with pure HME aggregates resulted in PA activity in the conditioned medium that was equal to 110% and 96% of the control, respectively. The PA level found when pure FBAE cell aggregates were co-incubated with pure fibroblast aggregates was higher, 134% of the control, and the difference was statistically significant (P less than 0.001). Our results indicate that RPE cells can reduce endothelial cell PA, probably through both direct contact between the cells and PAI production. Fibroblasts did not have this influence on endothelial cell PA.