Localization of vascular endothelial growth factor in human retina and choroid

Expression of placental growth factor, neuropilin-1, and neuropilin-2 in primary pterygium tissue

PURPOSE

The aim of this study was to evaluate the expression of placental growth factor (PLGF), neuropilin-1 (NP-1), and neuropilin-2 (NP-2) molecules in primary pterygium tissue compared with normal conjunctival tissue.

METHODS

The records of 42 patients who underwent excision surgery with autografts for primary pterygium (pterygium group) and 20 patients who underwent conjunctival nevus excision surgery (control group) in the same period were reviewed retrospectively. The samples obtained from the pterygium tissues in the pterygium group and the clean conjunctival tissues adjacent to the nevus in the control group were collected from the archive. Immunohistochemical stains of the primary antibodies-1/100 diluted PLGF, NP-1, and NP-2 (Abcam Cambridge Science Park, UK)-were applied to all groups. Staining intensities and the percentage of positive cells in epithelial, endothelial, stromal, and inflammatory cells were analyzed by an experienced pathologist.

RESULTS

The positivity rates of PLGF and NP-2 expression in epithelial, endothelial, stromal, and inflammatory cells were found to be higher in the pterygium group than in the control group (PLGF: p < 0.001, p < 0.001, p = 0.001, and p < 0.001, respectively; NP-2: p < 0.001 for all). Staining intensities for PLGF and NP-2 were higher in the pterygium group than in the control group (PLGF: p < 0.001, p < 0.001, p = 0.005, and p < 0.001, respectively; NP-2: p < 0.001, p < 0.001, p = 0.001, and p < 0.001, respectively). However, no significant differences were found in any cell type in terms of NP-1 expression positivity rates (p = 0.730, p = 0.121, p = 0.524, and p = 0.624, respectively) or staining intensity (p = 0.716, p = 0.147, p = 0.147, and p = 0.780, respectively).

CONCLUSION

PLGF and NP-2 levels were found to be higher in pterygium tissue, while there was no difference in NP-1. These results indicate the possible roles of NP-2 and PLGF in primary pterygium.

PIK3CA regulates development of diabetes retinopathy through the PI3K/Akt/mTOR pathway

OBJECTIVE

To explore their association with the development of diabetes retinopathy (DR), single nucleotide polymorphism (SNP) mutations were screened out by high-throughput sequencing and validated in patients diagnosed with DR. To understand the role of PIK3CA in the pathogenesis of DR and explore the relationship between PIK3CA,phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR),and DR, the effect of PIK3CA.rs17849079 mutation was investigated in a DR cell model.

METHODS

Twelve patients diagnosed with DR at the Qinghai Provincial People's Hospital from September 2020 to June 2021 were randomly selected as the case group, while 12 healthy subjects of similar age and gender who underwent physical examination in Qinghai Provincial People's Hospital physical examination center during the same period were randomly selected as the control group. Blood samples (2 mL) were collected from both groups using EDTA anticoagulant blood collection vessels and frozen at -20°C for future analysis. SNP mutations were detected by high-throughput sequencing, and the shortlisted candidates were subjected by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. The detected SNP candidates were verified by expanding the sample size (first validation: 56 patients in the case group and 58 controls; second validation: 157 patients in the case group and 96 controls). A lentivirus vector carrying mutated or wild-type PIK3CA.rs17849079 was constructed. ARPE-19 cells were cultured in a medium supplemented with 10% fetal bovine serum (FBS) to establish a DR cell model. PIRES2-PIK3CA-MT and PIRES2-PIK3CA-WT vectors were transfected into DR model cells, which were categorized into control, mannitol, model, empty vector, PIK3CA wild-type, and PIK3CA mutant-type groups. Cell activity was detected by the cell counting kit (CCK)-8 assay, and cellular apoptosis was evaluated by flow cytometry. Glucose concentration and levels of cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-1β were detected using enzyme-linked immunosorbent assay kits. The expression of PIK3CA, AKT1, mTOR, and VEGF genes was detected by real-time quantitative polymerase chain reaction (RT-qPCR), while the expression of PI3K, p-PI3K, AKT1, p-AKT1, mTOR, p-mTOR, and VEGF proteins was detected by western blotting.

RESULTS

The mutated SNPs were mainly enriched in the PI3K/AKT pathway, calcium ion pathway, and glutamatergic synaptic and cholinergic synaptic signaling pathways. Seven SNPs, including PRKCE.rs1533476, DNAH11.rs10485983, ERAP1.rs149481, KLHL1.rs1318761, APOBEC3C.rs1969643, FYN.rs11963612, and KCTD1.rs7240205, were not related to the development of DR. PIK3CA.rs17849079 was prone to C/T mutation. The risk of DR increased with the presence of the C allele and decreased in the presence of the T allele. High glucose induced the expression of PIK3CA and VEGF mRNAs as well as the expression of PI3K, p-PI3K, p-AKT1, p-mTOR, and VEGF proteins in ARPE-19 cells, which led to secretion of inflammatory factors TNF-αand IL-1, cell apoptosis, and inhibition of cell proliferation. The PIK3CA.rs17849079 C allele accelerated the progression of DR. These biological effects were inhibited when the C allele of PIK3CA.rs17849079 was mutated to T allele.

CONCLUSION

The mutated SNP sites in patients with DR were mainly enriched in PI3K/AKT, calcium ion, and glutamatergic synaptic and cholinergic synaptic signaling pathways. The rs17849079 allele of PIK3CA is prone to C/T mutation where the C allele increases the risk of DR. High glucose activates the expression of PIK3CA and promotes the phosphorylation of PI3K, which leads to the phosphorylation of AKT and mTOR. These effects consequently increase VEGF expression and accelerate the development of DR. The C to T allele mutation in PIK3CA.rs17849079 can play a protective role and reduce the risk of DR.

Macular changes following cataract surgery in eyes with early diabetic retinopathy: an OCT and OCT angiography study

Background

To evaluate changes in macular status and choroidal thickness (CT) following phacoemulsification in patients with mild to moderate nonproliferative diabetic retinopathy (NPDR) using optical coherence tomography.

Methods

In this prospective study, all of the patients underwent uncomplicated phacoemulsification. Retinal superficial capillary plexus vascular density (SCP-VD), macular thickness (MT), and CT were measured pre- and postoperatively.

Results

Twenty-two eyes of 22 cataract patients with mild to moderate NPDR without diabetic macular edema (DME) and 22 controls were enrolled. BCVA increased in two groups at 3 months postoperatively. At 1 and 3 months postoperatively, SCP-VD in the diabetic retinopathy (DR) group significantly increased; changes in SCP-VD in parafovea were significantly greater in the DR group than in the control group. MT and CT in the DR group significantly increased at all visits postoperatively in the fovea and perifovea. Changes in parafoveal MT were significantly greater in the DR group than in the control group at all visits postoperatively. Changes in CT and MT in the fovea were significantly greater in patients with DR than in the controls 1 and 3 months postoperatively.

Conclusion

Uncomplicated phacoemulsification resulted in greater increases in SCP-VD, MT and CT in patients with early DR without preoperative DME than in controls.

Choroidal vascularity profile in diabetic eyes using wide field optical coherence tomography

PURPOSE

To report the wide-field choroidal vascularity up to the mid-equator area in diabetic retinopathy (DR) subjects using wide-field optical coherence tomography (WF-OCT).

DESIGN

Prospective, Cross-sectional study.

PARTICIPANTS

Forty-seven eyes of 25 DR subjects.

METHODS

WF-OCT images (55 degrees) were obtained using Spectralis HRA + OCT (Heidelberg Engineering, Germany) in extremes of gazes in all quadrants and manual montages were created to obtain wide field images up to mid equator. A previously reported semi-automated algorithm was used to calculate choroidal vascularity profile (CVI). Regression analysis was performed to identify the factors influencing CVI.

RESULTS

Forty-seven eyes from 25 patients were enrolled in the study. The mean age was 68.4 ± 10.6 years. The refractive error (spherical equivalent) ranged from -2.25 to +3.75 diopters. Most common DR grade among study subjects was moderate NPDR (29.41%) and 74.5% eyes had diabetic macular edema (DME). The mean CVI in the macular area (58.29 ± 3.63) was significantly lower than in any of the other fundus areas (all p ˂ 0.01). The maximum CVI was seen in the nasal region (66.60 ± 5.61), followed by temporal (65.69 ± 3.81), superior (65.01 ± 4.87), and inferior (63.80 ± 5.42). The vertical macular area had the least coefficient of variation (CV) of CVI (0.06) while the inferior quadrant had the highest CV (0.08).

CONCLUSION

The current study describes the CVI profile on WF-OCT in DR eyes up to mid-equator. The significant increase of the CVI compared to healthy subjects and its significant regional variations introduce this novel quantitative parameter as a reliable biomarker of the diabetes-induced choroidal microangiopathy.

Effects of long-term high-altitude exposure on retinal and choroidal microcirculation

PURPOSE

To quantify the effect of long-term high-altitude (HA) exposure on retinal and choroidal microcirculation and to relate these changes to high-altitude polycythemia (HAPC), as a proxy for etiopathogenesis of high-altitude related retinopathy (HAR).

METHODS

Fifty-one HAPC patients, 50 healthy HA residents, and 43 low altitude (LA) residents were recruited in this study. Optical coherence tomography angiography (OCTA) and enhanced depth imaging (EDI)-OCT images were analyzed. Retinal microvascular metrics included vessel density (VD), skeleton density (SD), fractal dimension (FD), and foveal avascular zone (FAZ). Choroidal microvascular metrics included subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI). All metrics were calculated by ImageJ software and compared among HAPC group, healthy HA group, and LA group.

RESULTS

In HAPC group, VD (30.62 ± 3.67%), SD (13.25 ± 1.64%), FD (1.79 ± 0.04), and the CVI (63.01 ± 1.42%) were significant lower and SFCT (403.25 ± 94.3 μm) was significant thicker than healthy HA group (all P < 0.001). FAZ area was comparable between two groups (0.42 ± 0.1 vs. 0.4 ± 0.11 mm², P = 0.411). However, these metrics were not different between healthy HA group and LA group (all P > 0.05) except for FD was lower in HA group (P < 0.001). Pearson's correlation analyses revealed HGB was negatively related with VD (r =  - 0.562, P < 0.001) and positively related with SFCT (r = 0.505, P < 0.001) in healthy HA group; however, no associations between HGB and vascular metrics in HAPC group were detected (all P > 0.05).

CONCLUSIONS

Long-term exposure to HA environment induces retinal and choroidal microcirculation disturbance in HAPC patients. However, these changes were not evident in healthy HA residents because of adaptation.

Diabetic Retinopathy: From Animal Models to Cellular Signaling

Diabetic retinopathy (DR) is an ocular complication of diabetes mellitus (DM), a metabolic disorder characterized by elevation in blood glucose level. The pathogenesis of DR includes vascular, neuronal, and inflammatory components leading to activation of complex cellular molecular signaling. If untreated, the disease can culminate in vision loss that eventually leads to blindness. Animal models mimicking different aspects of DM complications have been developed to study the development and progression of DR. Despite the significant contribution of the developed DR models to discovering the mechanisms of DR and the recent achievements in the research field, the sequence of cellular events in diabetic retinas is still under investigation. Partially, this is due to the complexity of molecular mechanisms, although the lack of availability of models that adequately mimic all the neurovascular pathobiological features observed in patients has also contributed to the delay in determining a precise molecular trigger. In this review, we provide an update on the status of animal models of DR to help investigators choose an appropriate system to validate their hypothesis. We also discuss the key cellular and physiological events of DR in these models.

Diabetic macular ischaemia- a new therapeutic target?

Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

A 60% Edible Ethanolic Extract of Ulmus davidiana Inhibits Vascular Endothelial Growth Factor-Induced Angiogenesis

As abnormal angiogenesis is associated with exacerbation of various diseases, precise control over angiogenesis is imperative. Vascular endothelial growth factor (VEGF), the most well-known angiogenic factor, binds to VEGF receptor (VEGFR), activates various signaling pathways, and mediates angiogenesis. Therefore, blocking the VEGF-induced angiogenic response-related signaling pathways may alleviate various disease symptoms through inhibition of angiogenesis. Ulmus davidiana is a safe natural product that has been traditionally consumed, but its effects on endothelial cells (ECs) and the underlying mechanism of action are unclear. In the present study, we focused on the effect of a 60% edible ethanolic extract of U. davidiana (U60E) on angiogenesis. U60E inhibited the VEGF-mediated proliferation, tube formation, and migration ability of ECs. Mechanistically, U60E inhibited endothelial nitric oxide synthase activation and nitric oxide production by blocking the protein kinase B signaling pathway activated by VEGF and consequently inhibiting proliferation, tube formation, and migration of ECs. These results suggest that U60E could be a potential and safe therapeutic agent capable of suppressing proangiogenic diseases by inhibiting VEGF-induced angiogenesis.

Exploring the Pharmacological Mechanism of Liuwei Dihuang Decoction for Diabetic Retinopathy: A Systematic Biological Strategy-Based Research

OBJECTIVE

To explore the pharmacological mechanism of Liuwei Dihuang decoction (LDD) for diabetic retinopathy (DR).

METHODS

The potential targets of LDD were predicted by PharmMapper. GeneCards and other databases were used to collect DR genes. Cytoscape was used to construct and analyze network DR and LDD's network, and DAVID was used for Gene Ontology (GO) and pathway enrichment analysis. Finally, animal experiments were carried out to verify the results of systematic pharmacology.

RESULTS

Five networks were constructed and analyzed: (1) diabetic retinopathy genes' PPI network; (2) compound-compound target network of LDD; (3) LDD-DR PPI network; (4) compound-known target network of LDD; (5) LDD known target-DR PPI network. Several DR and treatment-related targets, clusters, signaling pathways, and biological processes were found. Animal experiments found that LDD can improve the histopathological changes of the retina. LDD can also increase erythrocyte filtration rate and decrease the platelet adhesion rate (P < 0.05) and decrease MDA and TXB2 (P < 0.05). Compared with the model group, the retinal VEGF and HIF-1α expression in the LDD group decreased significantly (P < 0.05).

CONCLUSION

The therapeutic effect of LDD on DR may be achieved by interfering with the biological processes (such as response to insulin, glucose homeostasis, and regulation of angiogenesis) and signaling pathways (such as insulin, VEGF, HIF-1, and ErbB signaling pathway) related to the development of DR that was found in this research.

Regulation of blood-retinal barrier cell-junctions in diabetic retinopathy

Loss of the blood-retinal barrier (BRB) integrity and subsequent damage to the neurovascular unit in the retina are the underlying reasons for diabetic retinopathy (DR). Damage to BRB eventually leads to severe visual impairment in the absence of prompt intervention. Diabetic macular edema and proliferative DR are the advanced stages of the disease where BRB integrity is altered. Primary mechanisms contributing to BRB dysfunction include loss of cell-cell barrier junctions, vascular endothelial growth factor, advanced glycation end products-induced damage, and oxidative stress. Although much is known about the involvement of adherens and tight-junction proteins in the regulation of vascular permeability in various diseases, there is a significant gap in our knowledge on the junctional proteins expressed in the BRB and how BRB function is modulated in the diabetic retina. In this review article, we present our current understanding of the molecular composition of BRB, the changes in the BRB junctional protein turnover in DR, and how BRB functional modulation affects vascular permeability and macular edema in the diabetic retina.

Choroidal Structural Changes Assessed with Swept-Source Optical Coherence Tomography after Cataract Surgery in Eyes with Diabetic Retinopathy

Objective

To determine the influence of phacoemulsification on choroidal vasculature in patients with diabetic retinopathy (DR) undergoing cataract surgery using swept-source optical coherence tomography (SS-OCT).

Methods

The study was conducted in 23 eyes of 23 cataract patients with mild/moderate nonproliferative diabetic retinopathy (NPDR) without diabetic macular edema (DME) and 23 age-matched controls. Choroidal thickness (CT) and choroidal vascularity index (CVI) were measured at baseline and 1 week, 1 month, and 3 months after surgery.

Results

The baseline CVI in the DR group was significantly lower than that in the control group (P=0.001). CVI in DR patients after surgery significantly increased compared with preoperative values (all P < 0.001 for 1 week, 1 month, and 3 months after surgery). Postoperative increase of CVI and CT in the DR group was more than in the control group, and the difference was significant 1 month and 3 months after surgery (all P < 0.05).

Conclusion

Patients with mild/moderate NPDR have reduced CVI compared with nondiabetic patients at baseline; diabetic cataract surgery tended to induce more increase in CVI and CT as compared with nondiabetic patients. This trial is registered with NCT04499768.

Visual field defects and changes in central retinal artery occlusion

Objectives

To investigate the characteristics and temporal changes in visual field defects (VFDs) in eyes with acute central retinal artery occlusion (CRAO).

Design

Retrospective, observational case series

Methods

A total of 119 patients diagnosed with acute non-arteritic CRAO through examination with Goldmann perimetry were included among the patients who visited Seoul National University Bundang Hospital between January 2009 and December 2016. They were treated with either conservative treatments or intra-arterial thrombolysis (IAT). The baseline features and temporal changes of visual field examination results and the association with clinical parameters including visual acuity, optical coherence tomography (OCT) findings, and the CRAO stages.

Results

All of the 119 patients showed visual field defect and suffered unilateral acute CRAO. We observed five characteristic VFDs: peripheral constriction only (8%), paracentral scotoma (3%), central and cecocentral scotoma (19%), temporal island (59%), and no visual field (10%). Severe VFDs were associated with severe CRAO stages, poor baseline BCVA, delayed retinal arterial perfusion, and severe retinal morphologic changes on OCT. We found improvements in the visual field in 39% of all cases during the follow-up periods. Mild CRAO stages, good baseline BCVA, mild retinal morphologic changes, and mild initial VFDs were significantly associated with visual field improvement.

Conclusions

The five characteristic types of VFDs and their improvement in eyes with CRAO are associated with baseline features related to the severity of retinal ischemia. We suggest that the underlying mechanisms of VFDs involve the balance between the retinal arterial perfusion and the ischemic vulnerability of each retinal area.

Epistatic Interaction Between 5-HT1A and Vascular Endothelial Growth Factor Gene Polymorphisms in the Northern Chinese Han Population With Major Depressive Disorder

Aims: Serotonin 1A receptor (5-HT1A) and vascular endothelial growth factor (VEGF) are widely expressed in the neurons of the hippocampus and have significant roles in the pathophysiological processes of major depressive disorders (MDDs). The present study was designed to examine 5-HT1A and VEGF gene polymorphisms and whether the gene-gene interaction of 5-HT1A and VEGF gene variants was associated with MDD. Methods: A total of 264 MDD patients and 264 healthy controls were included in the present genetic study. The rs6295, rs1364043, and rs878567 single-nucleotide polymorphisms (SNPs) in the 5-HT1A gene and the rs699947, rs833061, and rs2010963 SNPs in the VEGF gene were selected for genotypic analyses. The generalized multifactor dimensionality reduction method was employed to assess their interactions. Results: The genotype distributions of the two genes' respective SNPs were significantly different between patients and controls for 5-HT1A rs6295 (p = 0.041) and VEGF rs2010963 (p = 0.035); however, no significant allelic variation in 5-HT1A (rs6295, rs1364043, and rs878567) and VEGF (rs699947, rs833061, and rs2010963) was found. The interactions between 5-HT1A (rs6295, rs1364043, and rs878567) and VEGF (rs699947, rs833061, and rs2010963) had a cross-validation (CV) consistency of 10/10 and a p value of 0.0107, which was considered as the best generalized multifactor dimensionality reduction (GMDR) model. Conclusions: The interactions between 5-HT1A and VEGF gene polymorphisms may play a key role in the development of MDD in the Northern Chinese Han population.

Ocular Histopathology and Immunohistochemical Analysis in the Oldest Known Individual with Autosomal Dominant Vitreoretinochoroidopathy

PURPOSE

To assess the immunohistochemical and histopathological changes in a subject with Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC).

DESIGN

Case study.

PARTICIPANT

Ninety two year-old Caucasian male with ADVIRC.

METHODS

The subject was documented clinically for 54 Years. The retina/choroid complex of the right eye was evaluated with cryosections stained with hematoxylin and eosin or periodic acid schiff reagent. Cryosections were also evaluated with immunofluorescence or alkaline phosphatase immunohistochemistry (IHC) using primary antibodies against bestrophin1, GFAP, PEDF, RPE65, TGFβ, VEGF, and vimentin. The left retina and choroid were evaluated as flat mounts using immunofluorescence. UEA lectin was used to stain viable vasculature.

MAIN OUTCOME MEASURES

The immunohistochemical and histopathological changes in retina and choroid from a subject with ADVIRC.

RESULTS

The subject had a heterozygous c.248G>A variant in exon 4 of the BEST1 gene. There was widespread chorioretinal degeneration and atrophy except for an island of spared RPE monolayer in the perimacula/macula OU. In this region, some photoreceptors were present, choriocapillaris was spared, and retinal pigment epithelial cells were in their normal disposition. There was a Muller cell periretinal membrane throughout much of the fundus. Bestrophin-1 was not detected or only minimally present by IHC in the ADVIRC RPE, even in the spared RPE area. Beyond the island of retained RPE monolayer on Bruch's membrane (BrMb), there was migration of RPE into the neuro-retina, often ensheathing blood vessels and producing excessive matrix within their perivascular aggregations.

CONCLUSIONS

The primary defect in ADVIRC is in RPE, the only cells in the eye that express the BEST1 gene. The dysfunctional RPE cells may go through epithelial/mesenchymal transition as they migrate from BrMb to form papillary aggregations in the neuro-retina, often ensheathing blood vessels. This may be the reason for retinal blood vessel nonperfusion. Migration of RPE from BrMb was also associated with attenuation of the choriocapillaris.

Choroidal Thickness Change in Patients With Diabetic Macular Edema

BACKGROUND AND OBJECTIVE

To evaluate subfoveal choroidal thickness (SFCT) in diabetic macular edema (DME) and its relationships.

PATIENTS AND METHODS

One hundred and six eyes were included in this prospective, nonrandomized case control study. They were divided into 37 cases of healthy, normal subjects and 69 cases of nonproliferative diabetic retinopathy (NPDR) with DME. Spectral-domain optical coherence tomography was done for all cases and analyzed to measure SFCT and central foveal thickness (CFT).

RESULTS

The SFCT was significantly thinner in the DME group (193.4 μm) than in the control group (282.6 μm) (P = .001). In the DME group, SFCT was significantly related to CFT and vision (P < .05). The cutoff point for the relationship between SFCT and vision was 228 μm below the point at which vision is affected.

CONCLUSIONS

DME is associated with a significant decrease in SFCT. SFCT is directly related to vision and foveal thickness, but it is inversely correlated to age. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:970-977.].

Diabetic choroidopathy

Early histopathological studies of diabetic choroids demonstrated loss of choriocapillaris (CC), tortuous blood vessels, microaneurysms, drusenoid deposits on Bruchs membrane, and choroidal neovascularization. The preponderance of histopathological changes were at and beyond equator. Studies from my lab suggest that diabetic choroidopathy is an inflammatory disease in that leukocyte adhesion molecules are elevated in the choroidal vasculature and polymorphonuclear neutrophils are often associated with sites of vascular loss. Modern imaging techniques demonstrate that blood flow is reduced in subfoveal choroidal vasculature. Angiography has shown areas of hypofluorescence and late filling that probably represent areas of vascular loss and/or compromise. Perhaps, as a result of vascular insufficiency, the choroid appears to thin in DC unless macular edema is present. Enhanced depth imaging (EDI-SD) OCT and swept source (SS) OCT have documented the tortuosity and loss in intermediate and large blood vessels in Sattler's and Haller's layer seen previously with histological techniques. The risk factors for DC include diabetic retinopathy, degree of diabetic control, and the treatment regimen. In the future, OCT angiography could be used to document loss of CC. Because most of the measurement and imaging are in the posterior pole, the severity of DC may be underappreciated in the published accounts of DC assessed with imaging techniques. However, it is now possible to document DC and quantify these changes clinically. This suggests that DC should be evaluated in future clinical trials of drugs targeting DR because vascular changes similar to those in DR are occurring in DC.

In Vivo Assessment of Choroid in Diabetic Retinopathy by Enhanced Depth Imaging in Spectral Domain Optical Coherence Tomography

PURPOSE

The aim of this study was to measure the largest hyporeflective (LHR) lumen in the choroid and subfoveal choroidal thickness (SFCT) in patients with diabetic retinopathy (DR) and in control subjects using enhanced depth imaging (EDI) spectral domain optical coherence tomography (SD-OCT).

DESIGN

This was a prospective, cross-sectional study.

METHODS

This was a study of 240 eyes of DR patients (n = 120) and control subjects (n = 120) matched for age, sex, and refractive error. The LHR lumens of the choroidal vessels and SFCT were measured by EDI SD-OCT. Further intergroup classification into nonproliferative and proliferative DR, with or without macular edema, was done.

RESULTS

The mean diameter of the LHR lumen in DR patients (139.24 ± 35.53 μm) was significantly smaller (P < 0.01) than in control subjects (186.37 ± 26.43 μm). The mean SFCT was also significantly less (P < 0.01) in patients with diabetes (277.15 ± 32.24 μm) as compared with control subjects (313.68 ± 25.13 μm). There was no significant intergroup variation.

CONCLUSIONS

Patients with DR showed smaller LHR lumen and SFCT as compared with control eyes. In vivo assessment of the choroid in DR is possible using EDI SD-OCT.

Increased Vitreous Chemerin Levels Are Associated with Proliferative Diabetic Retinopathy

PURPOSE

To investigate chemerin in the vitreous bodies of patients with proliferative diabetic retinopathy (PDR) and determine the correlation between the levels of vitreous chemerin and vascular endothelial growth factor (VEGF).

METHODS

This study included 17 patients suffering from PDR and vitreous hemorrhage (VH) (group A), 21 patients with PDR and tractional retinal detachment (TRD) (group B) and 25 patients with idiopathic macular holes or preretinal membranes (control group). All vitreous samples were obtained through pars plana vitrectomy. Enzyme-linked immunosorbent assay and Western blot analysis were performed to evaluate the levels of vitreous chemerin and VEGF.

RESULTS

Vitreous concentrations of chemerin were significantly higher in PDR patients with VH and TRD than those in the controls [4.82 ng/ml (3.91-6.13) vs. 5.03 ng/ml (4.01-6.15) vs. 2.53 ng/ml (1.53-5.66), p = 0.025]. The ratio of vitreous chemerin to plasma chemerin concentration significantly differed between groups A and B and the control group [4.93% (4.69-5.34) vs. 4.98% (4.63-5.19) vs. 2.58% (1.78-4.58), p < 0.001]. Western blot results indicated that the levels of vitreous chemerin protein in PDR patients significantly increased compared with those in the controls. Spearman correlation analysis further showed that vitreous chemerin levels in patients with PDR were positively correlated with vitreous VEGF levels (r = -0.542, p < 0.001).

CONCLUSIONS

Increased vitreous chemerin levels are associated with the development of PDR.

Role of Serum Levels of Vascular Endothelial Growth Factor and Its Receptor in Retinopathy of Prematurity

Background:

Retinopathy of prematurity (ROP) is a disorder of developing retina of low birth weight preterm infants which can lead to blindness. One theory attributes the fibrosis seen in ROP to deregulation of vascularization in the retina. Vascular endothelial growth factor (VEGF) is one of the important mediators involved in vascularization.

Objectives:

This study was carried out to assess the role of VEGF and its receptor in retinopathy of prematurity.

Patients and Methods:

Around 200 preterm infants born in SSK hospital were screened at 33 - 34 weeks. These babies were followed up according to the international classification of retinopathy of prematurity (ICROP) criteria. Those infants who developed ROP at 38 - 40 weeks were enrolled in group A while an equal number of infants who did not develop ROP were included in group B. Each group comprised of 30 subjects each. Venous sampling was carried out twice, once at 33 - 34 weeks and then again at 38 - 40 weeks. VEGF and VEGF-R2 were estimated by commercially available ELISA kits.

Results:

There was no statistically significant difference between the levels of VEGF and VEGF-R2 in both groups at first visit as well as the follow up visit. However, the intra-group difference was significant between the first and the final visit in VEGF and VEGF-R2 levels in the cases with ROP. In the control population, the VEGF levels were significantly lower in the follow up visit as compared to the initial visit.

Conclusions:

Our study demonstrates that a significant difference is seen in the serum VEGF and VRGF-R2 in the second visit of the infants with ROP demonstrating that VEGF might be responsible for the initiation and aggravation of ROP.

Current knowledge on diabetic retinopathy from human donor tissues

According to the American Diabetes Association, diabetes was the seventh leading cause of death, and diabetic retinopathy the leading cause of blindness in working age adults in the United States in 2010. Diabetes is characterized by hyperglycemia associated with either hypoinsulinemia or insulin resistance, and over time, this chronic metabolic condition may lead to various complications including kidney failure, heart attacks, and retinal degeneration. In order to better understand the molecular basis of this disease and its complications, animal models have been the primary approach used to investigate the effects of diabetes on various tissues or cell types of the body, including the retina. However, inherent to these animal models are critical limitations that make the insight gained from these models challenging to apply to the human pathology. These difficulties in translating the knowledge obtained from animal studies have led a growing number of research groups to explore the diabetes complications, especially diabetic retinopathy, on tissues from human donors. This review summarizes the data collected from diabetic patients at various stages of diabetic retinopathy and classifies the data based upon their relevance to the main aspects of diabetic retinopathy: retinal vasculature dysfunction, inflammation, and neurodegeneration. This review discusses the importance of those studies to discriminate and establish the relevance of the findings obtained from animal models but also the limitations of such approaches.

Presumed primary ocular lymphangiosarcoma with metastasis in a miniature horse

A 7-year-old, 153.0-kg American Miniature mare presented for evaluation of keratoconjunctivitis of the right eye (OD). A superior palpebral conjunctival mass and stromal keratitis were diagnosed. The incisional biopsy diagnosis was a presumptive corneal hemangiosarcoma. Transpalpebral enucleation was performed, and histopathologic evaluation confirmed angiosarcoma of the conjunctiva, cornea, and extraocular muscles. The horse developed progressive epistaxis and orbital swelling following surgery. A systemic workup was performed 3 months after enucleation, revealing regrowth within the orbit and marked cranial cervical lymphomegaly, suggestive of metastasis. Humane euthanasia was performed, and necropsy confirmed a locally invasive periorbital tumor with metastasis to the submandibular tissue, submandibular lymph node, and thoracic inlet. Histopathologic evaluation of necropsy specimens revealed polygonal to spindle neoplastic cells lining neoplastic vascular channels lacking erythrocytes. Immunohistochemically, the neoplastic cells labeled strongly positive for PROX-1, vimentin, CD-31, VEGF, weakly positive for factor VIII-related antigen, and negative for collagen IV. Based on the clinical, histological, and immunohistochemical features of this tumor, a primary ocular lymphangiosarcoma with metastasis was diagnosed.

Diabetic Retinopathy: Vascular and Inflammatory Disease

Diabetic retinopathy (DR) is the leading cause of visual impairment in the working-age population of the Western world. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. Inflammation mediates structural and molecular alterations associated with DR. However, the molecular mechanisms underlying the inflammatory pathways associated with DR are not completely characterized. Previous studies indicate that tissue hypoxia and dysregulation of immune responses associated with diabetes mellitus can induce increased expression of numerous vitreous mediators responsible for DR development. Thus, analysis of vitreous humor obtained from diabetic patients has made it possible to identify some of the mediators (cytokines, chemokines, and other factors) responsible for DR pathogenesis. Further studies are needed to better understand the relationship between inflammation and DR. Herein the main vitreous-related factors triggering the occurrence of retinal complication in diabetes are highlighted.

Caffeic acid phenethyl ester: its protective role against certain major eye diseases

As an effective compound found mainly in the honeybee product propolis, caffeic acid phenethyl ester (CAPE) has been commonly utilized as a medicine and remedial agent, in a number of countries. Specifically, it might inhibit nuclear factor kappa B at micromolar concentrations and demonstrate antioxidant, antineoplastic, antiproliferative, cytostatic, antiviral, antibacterial, antifungal, and anti-inflammatory features. This review article summarizes the recent progress regarding the favorable effects of CAPE on a number of eye disease models, including cataract and posterior capsule opacification, corneal diseases, retina and optic nerve-related diseases, ischemia/reperfusion injury of retina, inflammation and infection-related diseases. CAPE has been found to exhibit promising efficacy, with minimal adverse effects, in animal and cell culture studies of several eye diseases.

Plasma levels of IL-17, VEGF, and adrenomedullin and S-cone dysfunction of the retina in children and adolescents without signs of retinopathy and with varied duration of diabetes

The study objective was to assess chosen biochemical parameters of blood and bioelectric function of the retina in patients with T1DM. The study group consisted of 41 patients with T1DM with no signs of diabetic retinopathy. The control group included 21 pediatric patients. We performed (1) S-cone ERG testing with retina response stimulation in both eyes at the luminance of 0.1, 0.2, and 0.5 (cd × s/m²) with the 440 nm blue flash and light application of the amber background (300 ph cd/m², 495 nm wavelength), (2) anthropometric measurements, (3) biochemical investigations: IL-17, VEGF, and ADM by the ELISA method. A comparison of the ERG results with biochemical investigations indicates a likely correlation between the worsening of retinal bioelectric function and VEGF levels growing with diabetes duration. We showed a negative correlation between ADM and HbA1c and described possible causes of ADM reduction observed in subgroup I. We demonstrated the presence of bioelectric retinal dysfunction already before the diagnosis of diabetic retinopathy, which provides new possibilities in the diagnosis of preclinical chronic complications of diabetes. The changes observed in the levels of IL-17, ADM, and VEGF suggest their involvement in the diabetic pathogenesis of eye diseases.

Comparison of choroidal thickness in patients with diabetes by spectral-domain optical coherence tomography

Purpose

To evaluate choroidal thickness in diabetes patients using spectral-domain optical coherence tomography.

Methods

We examined 203 eyes of 203 diabetic participants and 48 eyes of 48 healthy controls. The choroidal thickness at the foveal lesion was measured by enhanced-depth imaging optical coherence tomography. The participants were grouped according to diabetic retinopathy grade: no diabetic change, mild-to-moderate or severe non-proliferative, or proliferative diabetic retinopathy. The study parameters included history, age, axial length, intraocular pressure, central retinal thickness, fasting glucose, and blood pressure.

Results

The subfoveal choroidal thickness was thinner in eyes with non-proliferative or proliferative diabetic retinopathy than in normal eyes (p < 0.01). However, there was no difference between eyes with non-proliferative and proliferative diabetic retinopathy or between eyes with no diabetic change and the controls. Eyes exhibiting macular edema showed no significant difference in choroidal thickness compared with eyes having normal macular contours.

Conclusions

The central choroid is thinner when eyes show diabetic changes on the retina. However, the presence of diabetic macular edema or proliferative change is not associated with more pronounced choroidal thinning.

Vascular endothelial growth factor gene (VEGFA) polymorphisms may serve as prognostic factors for recurrent depressive disorder development

Recurrent depressive disorder (rDD) is a multifactorial disease. Vascular endothelial growth factor (VEGF) is one of the factors that have been suggested to play a role in the etiology and/or development of this disease. Limited information related to the role of VEGFA gene polymorphism in depressive disorder is available. The aim of the study was to analyze the association between VEGFA gene polymorphisms (+405G/C; rs2010963, +936C/T; rs 3025039), VEGFA gene expression, and its serum protein levels in rDD in the Caucasian population. In the current study, 268 patients and 200 healthy controls of the Caucasian origin were involved. Genotyping and gene expression were performed using polymerase chain reaction (PCR)-based methods. Enzyme-linked immunosorbent assay (ELISA) was used for detection of circulating serum VEGF levels. The distribution of VEGFA polymorphism +405G/C differed significantly between rDD patients and healthy subjects. The results of this study indicated that the C allele and CC genotype of VEGFA are risk factors for rDD. Haplotypes CC and TG are the important factors for depression development. Further, VEGFA mRNA expression and VEGF levels were higher in rDD patients than in controls. The VEGFA gene polymorphism may serve as a prognostic factor for rDD development. Our study showed higher levels of both VEGFA mRNA in the peripheral blood cells and serum VEGF in patients diagnosed with rDD than in healthy controls. The obtained results suggest VEGF and the gene encoding the molecule play a role in the etiology of the disease and should be further investigated.

Vascular endothelial growth factor gene polymorphisms and renal cell carcinoma: A systematic review and meta-analysis

Renal cell carcinoma (RCC) accounts for 3% of all cancer-related mortalities in adults. The risk factors for the development of RCC remain under investigation. Vascular endothelial growth factor (VEGF) is a key mediator of angiogenesis and is crucial for the development and metastasis of tumors, including RCC. VEGF gene polymorphisms may alter VEGF protein concentrations, affect the process of angiogenesis and may be involved in inter-individual variation in carcinogenesis. In the present study, a systematic review and meta-analysis were performed based on published case-control studies in order to estimate the association between VEGF gene polymorphisms and the susceptibility to RCC. A total of five studies that involved eight polymorphisms and were published between January 2000 and December 2012 were identified from PubMed. The results of this systematic review and meta-analysis indicate that the VEGF 936C/T, 1612G/A, −1154G/A, −2549I/D, −460T/C and 405G/C gene polymorphisms are not associated with the risk of RCC. There was no polymorphism in 702C/T and RCC and the −2578C/A gene polymorphism may be associated with an increased risk of RCC. However, due to the limitations of the present study, further high quality case-control studies are warranted to confirm these findings.

Attenuation of choroidal neovascularization by β(2)-adrenoreceptor antagonism

OBJECTIVES

To determine whether β-adrenergic blockade inhibits choroidal neovascularization (CNV) in a mouse model of laser-induced CNV and to investigate the mechanism by which β-adrenoreceptor antagonism blunts CNV.

DESIGN

Mice were subjected to laser burns, inducing CNV, and were treated with daily intraperitoneal injections of propranolol hydrochloride. Neovascularization was measured on choroidal-scleral flat mounts using intercellular adhesion molecule 2 immunofluorescence staining. The effect of β-adrenoreceptor signaling on expression of vascular endothelial growth factor (VEGF) was investigated using primary mouse choroidal endothelial cells (ChECs) and retinal pigment epithelial (RPE) cells. These cells were incubated with β-adrenoreceptor agonists and/or antagonists and assayed for Vegf messenger RNA and protein levels.

SETTING

University of Wisconsin School of Medicine and Public Health.

PARTICIPANTS

Wild-type 6-week-old female C57BL/6j mice.

MAIN OUTCOME MEASURES

Inhibition of CNV after propranolol treatment and Vegf messenger RNA and protein expression after treatment with β-adrenoreceptor agonists and antagonists.

RESULTS

Propranolol-treated mice demonstrated a 50% reduction in laser-induced CNV. Treatment with norepinephrine bitartrate stimulated Vegf messenger RNA expression and protein secretion in ChECs and RPE cells. This effect was blocked by β2-adrenoreceptor antagonism and mimicked by β2-adrenoreceptor agonists.

CONCLUSIONS

Attenuation of CNV is achieved by β-adrenergic blockade. The β2-adrenoreceptors regulate VEGF expression in ChECs and RPE cells.

CLINICAL RELEVANCE

Antagonists of β-adrenoreceptors are safe and well tolerated in patients with glaucoma and cardiovascular disease. Thus, blockade of β-adrenoreceptors may provide a new avenue to inhibit VEGF expression in CNV.

Therapeutic efficacy of melatonin in reducing retinal damage in an experimental model of early type 2 diabetes in rats

Diabetic retinopathy (DR) is a leading cause of acquired blindness in adults, mostly affected by type 2 diabetes mellitus (T2DM). We have developed an experimental model of early T2DM in adult rats which mimics some features of human T2DM at its initial stages and provokes significant retinal alterations. The aim of this work was to analyze the effect of melatonin on retinal changes induced by the moderate metabolic derangement. For this purpose, adult male Wistar rats received a control diet or 30% sucrose in the drinking water. Three weeks after this treatment, animals were injected with vehicle or streptozotocin (STZ, 25 mg/kg). One day or 3 wk after vehicle or STZ injection, animals were subcutaneously implanted with a pellet of melatonin. Fasting and postprandial glycemia, and glucose, and insulin tolerance tests were analyzed. At 12 wk of treatment, animals which received a sucrose-enriched diet and STZ showed significant differences in metabolic tests, as compared with control groups. Melatonin, which did not affect glucose metabolism in control or diabetic rats, prevented the decrease in the electroretinogram a-wave, b-wave, and oscillatory potential amplitude, and the increase in retinal lipid peroxidation, NOS activity, TNFα, Müller cells glial fibrillary acidic protein, and vascular endothelial growth factor levels. In addition, melatonin prevented the decrease in retinal catalase activity. These results indicate that melatonin protected the retina from the alterations observed in an experimental model of DR associated with type 2 diabetes.

Role of the retinal vascular endothelial cell in ocular disease

Retinal endothelial cells line the arborizing microvasculature that supplies and drains the neural retina. The anatomical and physiological characteristics of these endothelial cells are consistent with nutritional requirements and protection of a tissue critical to vision. On the one hand, the endothelium must ensure the supply of oxygen and other nutrients to the metabolically active retina, and allow access to circulating cells that maintain the vasculature or survey the retina for the presence of potential pathogens. On the other hand, the endothelium contributes to the blood-retinal barrier that protects the retina by excluding circulating molecular toxins, microorganisms, and pro-inflammatory leukocytes. Features required to fulfill these functions may also predispose to disease processes, such as retinal vascular leakage and neovascularization, and trafficking of microbes and inflammatory cells. Thus, the retinal endothelial cell is a key participant in retinal ischemic vasculopathies that include diabetic retinopathy and retinopathy of prematurity, and retinal inflammation or infection, as occurs in posterior uveitis. Using gene expression and proteomic profiling, it has been possible to explore the molecular phenotype of the human retinal endothelial cell and contribute to understanding of the pathogenesis of these diseases. In addition to providing support for the involvement of well-characterized endothelial molecules, profiling has the power to identify new players in retinal pathologies. Findings may have implications for the design of new biological therapies. Additional progress in this field is anticipated as other technologies, including epigenetic profiling methods, whole transcriptome shotgun sequencing, and metabolomics, are used to study the human retinal endothelial cell.

Animal models of diabetic retinopathy: summary and comparison

Diabetic retinopathy (DR) is a microvascular complication associated with chronic exposure to hyperglycemia and is a major cause of blindness worldwide. Although clinical assessment and retinal autopsy of diabetic patients provide information on the features and progression of DR, its underlying pathophysiological mechanism cannot be deduced. In order to have a better understanding of the development of DR at the molecular and cellular levels, a variety of animal models have been developed. They include pharmacological induction of hyperglycemia and spontaneous diabetic rodents as well as models of angiogenesis without diabetes (to compensate for the absence of proliferative DR symptoms). In this review, we summarize the existing protocols to induce diabetes using STZ. We also describe and compare the pathological presentations, in both morphological and functional aspects, of the currently available DR animal models. The advantages and disadvantages of using different animals, ranging from zebrafish, rodents to other higher-order mammals, are also discussed. Until now, there is no single model that displays all the clinical features of DR as seen in human. Yet, with the understanding of the pathological findings in these animal models, researchers can select the most suitable models for mechanistic studies or drug screening.

Ischemic conditioning protects the rat retina in an experimental model of early type 2 diabetes

Diabetic retinopathy is a leading cause of acquired blindness in adults, mostly affected by type 2 diabetes mellitus (T2DM). We have developed an experimental model of early T2DM in adult rats which mimics some features of human T2DM at its initial stages, and provokes significant retinal alterations. We investigated the effect of ischemic conditioning on retinal changes induced by the moderate metabolic derangement. For this purpose, adult male Wistar rats received a control diet or 30% sucrose in the drinking water, and 3 weeks after this treatment, animals were injected with vehicle or streptozotocin (STZ, 25mg/kg). Retinal ischemia was induced by increasing intraocular pressure to 120 mm Hg for 5 min; this maneuver started 3 weeks after vehicle or STZ injection and was weekly repeated in one eye, while control eyes were submitted to a sham procedure. Fasting and postprandial glycemia, and glucose, and insulin tolerance tests were analyzed. At 12 weeks of treatment, animals which received a sucrose-enriched diet and STZ showed significant differences in metabolic tests, as compared with control groups. Brief ischemia pulses in one eye and a sham procedure in the contralateral eye did not affect glucose metabolism in control or diabetic rats. Ischemic pulses reduced the decrease in the electroretinogram a-wave, b-wave, and oscillatory potential amplitude, and the increase in retinal lipid peroxidation, NOS activity, TNFα, Müller cells glial fibrillary acidic protein, and vascular endothelial growth factor levels observed in diabetic animals. In addition, ischemic conditioning prevented the decrease in retinal catalase activity induced by T2DM. These results indicate that induction of ischemic tolerance could constitute a fertile avenue for the development of new therapeutic strategies to treat diabetic retinopathy associated with T2DM.

Aberrant angiogenesis: The gateway to diabetic complications

Diabetes Mellitus is a metabolic cum vascular syndrome with resultant abnormalities in both micro- and macrovasculature. The adverse long-term effects of diabetes mellitus have been described to involve many organ systems. Apart from hyperglycemia, abnormalities of angiogenesis may cause or contribute toward many of the clinical manifestations of diabetes. These are implicated in the pathogenesis of vascular abnormalities of the retina, kidneys, and fetus, impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. The current article hereby reviews the molecular mechanisms including abnormalities in growth factors, cytokines, and metabolic derangements, clinical implications, and therapeutic options of dealing with abnormal angiogenesis in diabetes.

Imbalanced levels of angiogenic and angiostatic factors in vitreous, plasma and postmortem retinal tissue of patients with proliferative diabetic retinopathy

A role for vascular endothelial growth factor (VEGF) has been clearly implicated in the pathogenesis of proliferative diabetic retinopathy (PDR). However, other molecules and mechanisms may be operating independently, or in conjunction with VEGF in the pathogenesis of this disease. Therefore, we made an attempt to comparatively investigate the levels of angiogenic and angiostatic factors in vitreous, plasma and postmortem retinal tissue of subjects with Proliferative Diabetic Retinopathy (PDR) compared to control subjects. The vitreous and plasma concentrations of VEGF, EPO (Erythropoietin) and PEDF (Pigment Epithelium Derived Factor) were measured using Enzyme Linked Immunosorbent Assay (ELISA) and the postmortem retinal tissue was subjected to Western blot analysis. The mean vitreous and plasma levels of VEGF and EPO in patients with PDR were significantly (p<0.001) higher than those in subjects without diabetes. Conversely, the vitreous and plasma levels of PEDF were significantly (p<0.001) lower in the PDR patients compared to control subjects. Multivariate logistic-regression analyses indicated that EPO was more strongly associated with PDR than VEGF. The protein expression of the VEGF and EPO in the retinal tissue was significantly higher in PDR and diabetes without complication groups compared to controls. Compared to controls, the protein expression of PEDF was significantly lower in retinal tissues from diabetes patients without complications and in patients with PDR. The fact that the vitreous and plasma levels and the retinal tissue protein expression of EPO were strongly associated with PDR implies a definite role of 'hypererythropoietinemia' in neovascularization processes.

Structural and functional changes of the human macula during acute exposure to high altitude

Background

This study aimed to quantify structural and functional changes at the macula during acute exposure to high altitude and to assess their structure/function relationship. This work is related to the Tuebingen High Altitude Ophthalmology (THAO) study.

Methodology/Principal Findings

Spectral domain optical coherence tomography and microperimetry were used to quantify changes of central retinal structure and function in 14 healthy subjects during acute exposure to high altitude (4559 m). High-resolution volume scans and fundus-controlled microperimetry of the posterior pole were performed in addition to best-corrected visual acuity (BCVA) measurements and assessment of acute mountain sickness. Analysis of measurements at altitude vs. baseline revealed increased total retinal thickness (TRT) in all four outer ETDRS grid subfields during acute altitude exposure (TRT_outer = 2.80±1.00 μm; mean change±95%CI). This change was inverted towards the inner four subfields (TRT_inner = −1.89±0.97 μm) with significant reduction of TRT in the fovea (TRT_foveal = −6.62±0.90 μm) at altitude. BCVA revealed no significant difference compared to baseline (0.06±0.08 logMAR). Microperimetry showed stable mean sensitivity in all but the foveal subfield (MS_foveal = −1.12±0.68 dB). At baseline recordings before and >2 weeks after high altitude exposure, all subjects showed equal levels with no sign of persisting structural or functional sequels.

Conclusions/Significance

During acute exposure to high altitude central retinal thickness is subject to minor, yet statistically significant changes. These alterations describe a function of eccentricity with an increase in regions with relatively higher retinal nerve fiber content and vascular arcades. However, these changes did not correlate with measures of central retinal function or acute mountain sickness. For the first time a quantitative approach has been used to assess these changes during acute, non-acclimatized high altitude exposure.

Retinal changes in an experimental model of early type 2 diabetes in rats characterized by non-fasting hyperglycemia

Diabetic retinopathy is a leading cause of acquired blindness in young, but also in elder adults, mostly affected by type 2 diabetes mellitus (T2DM). The aim of this work was to develop an experimental model of early human T2DM in adult rats, and to analyze retinal functional, morphological, and biochemical changes arising during the early stages of the moderate metabolic derangement. For this purpose, animals were divided in four groups: adult male Wistar rats receiving: tap water and citrate buffer i.p. (group 1), tap water with 30% sucrose and citrate buffer i.p. (group 2), tap water and 25mg/kg i.p streptozotocin (STZ, group 3), or 30% sucrose and STZ (group 4). Fasting and postprandial glycemia, fructosamine and serum insulin levels were assessed. In addition, i.p. glucose and insulin tolerance tests were performed. Retinal function (electroretinogram, ERG) and morphology (optical microscopy), retinal nitric oxide synthase (NOS) activity (using (3)H-arginine), lipid peroxidation (thiobarbituric acid reactive substances, TBARS), and TNFα levels (ELISA) were evaluated. At 6 and 12 weeks of treatment, animals which received a sucrose-enriched diet and STZ showed significant differences in most metabolic tests, as compared with the other groups. At 12 weeks of treatment, a significant decrease in the ERG a- and b- wave and oscillatory potential amplitudes, and a significant increase in retinal NOS activity, TBARS, TNFα, glial fibrillary acidic protein in Müller cells, and vascular endothelial growth factor levels were observed. These results indicate that the combination of diet-induced insulin resistance and a slight secretory impairment resulting from a low-dose STZ treatment mimics some features of human T2DM at its initial stages, and provokes significant retinal alterations.

The role of angiogenesis in the development of proliferative diabetic retinopathy: impact of intravitreal anti-VEGF treatment

Although cellular and molecular bases of proliferative diabetic retinopathy are only partially understood, it is evident that this complication of diabetes is characterized by the formation of new vessels inside the retina showing abnormal architecture and permeability. This process, if not controlled by selective laser photocoagulation, leads to irreversible retinal damages and loss of vision. Angiogenesis, that is, the condition characterized by the growth of new blood vessels originated from preexisting ones, was shown to have a major role in the pathogenesis of proliferative retinopathy and, as a consequence, intravitreal antiangiogenic injection was suggested as a feasible treatment for this disease. Here, we describe the different antiangiogenic approaches used to treat this disease along with the respective advantages and limitations when compared to laser treatment. Altogether, even though further and longer studies are still needed to clarify the best possible therapeutic protocol, the antiangiogenic treatment will reasonably have a future role in the therapy and prevention of proliferative diabetic retinopathy.

Lasting controversy on ranibizumab and bevacizumab

Vascular endothelial growth factor (VEGF), an important angiogenic factor that is able to stimulate the proliferation and migration of endothelial cells, is the best-studied hallmark of angiogenesis. Neovascularization is a major cause of age-related macular degeneration (AMD) which is a leading cause of blindness in the elderly population. Specific molecular inhibitors of VEGF have been proved to be useful in the treatment of AMD. Ranibizumab and Bevacizumab are structurally similar to anti-VEGF drugs in the treatment of AMD. Many studies have indicated that Ranibizumab and Bevacizumab are of roughly equal short-term efficacy and safety, Bevacizumab is an attractive alternative to Ranibizumab due to its lower cost. However, only Ranibizumab has received Food and Drug Administration (FDA) approval for the treatment of macular degeneration. More multicenter clinical trials are required to compare the relative efficacy and safety of these two drugs and some progress has been achieved. This review discusses the clinical effectiveness, safety, cost and other practical implications of Ranibizumab and Bevacizumab.

Possibility of enhanced risk of retinal neovascularization in repeated blood donors: blood donation and retinal alteration

Repeated blood donors manifest clinical, subclinical, and biochemical signs of iron deficiency anemia, have significantly higher erythropoietin and vascular endothelial growth factor (VEGF) concentrations, and decreased tissue oxygen saturation, oxygenated tissue hemoglobin, and regional cerebral oxygen saturation. Erythropoietin and VEGF are potent retinal angiogenic factors which may initiate and promote the retinal angiogenesis process independently or simultaneously. Increases in circulating levels of erythropoietin and VEGF are proportionate to the levels of hematocrit, hypoxemia, and tissue hypoxia. It is suggested that higher erythropoietin production following iron deficiency anemia-induced chronic hypoxemia/ hypoxia may, hypothetically, enhance the risk of retinal angiogenesis and/or neovascularization, possibly by inducing hypoxia inducible factor-1 alpha, which consequently upregulates genes stimulating angiogenesis, resulting in formation of a new vasculature, possibly by modulation of signal transducer and activator of transcription 3 signaling in the retina. Implications of this hypothesis cover erythropoietin doping, chronic hypoxia, and hypoxemic situations, such as angiogenesis-related cardiac and pulmonary diseases.

Alterations to the blood-retinal barrier in diabetes: cytokines and reactive oxygen species

Diabetic retinopathy (DR) is a leading cause of blindness in Western society. Since the prevalence of diabetes continues to increase dramatically, the impact of DR will only worsen unless new therapeutic options are developed. Recent data demonstrate that oxidative stress contributes to the pathology of DR and inhibition of oxidative stress reduces retinal vascular permeability. However, direct mechanisms by which oxidative stress alters the blood-retinal barrier (BRB) and increases vascular permeability remain to be elucidated. A large body of evidence demonstrates a clear role for altered expression of cytokines and growth factors in DR, resulting in increased vascular permeability, and the molecular mechanisms for these processes are beginning to emerge. The pathology of DR is likely a result of metabolic dysregulation contributing to both oxidative stress and cytokine production. This review will examine the evidence for oxidative stress, growth factors, and other cytokines in tight junction regulation and vascular permeability in DR.

Induction of ischemic tolerance protects the retina from diabetic retinopathy

Diabetic retinopathy is a leading cause of acquired blindness. Available treatments are not very effective. We investigated the effect of a weekly application of retinal ischemia pulses (ischemic conditioning) on retinal damage induced by experimental diabetes. Diabetes was induced by an intraperitoneal injection of streptozotocin. Retinal ischemia was induced by increasing intraocular pressure to 120 mmHg for 5 minutes; this maneuver started 3 days after streptozotocin injection and was weekly repeated in one eye, whereas the contralateral eye was submitted to a sham procedure. Diabetic retinopathy was evaluated in terms of i) retinal function (electroretinogram and oscillatory potentials), ii) integrity of blood-retinal barrier (by albumin-Evans blue complex leakage and astrocyte glial fibrillary acidic protein IHC), iii) optical and electron microscopy histopathologic studies, and iv) vascular endothelial growth factor levels (using Western blot analysis and IHC). Brief ischemia pulses significantly preserved electroretinogram a- and b-wave and oscillatory potentials, avoided albumin-Evans blue leakage, prevented the decrease in astrocyte glial fibrillary acidic protein levels, reduced the appearance of retinal edemas, and prevented the increase in vascular endothelial growth factor levels induced by experimental diabetes. When the application of ischemia pulses started 6 weeks after diabetes onset, retinal function was significantly preserved. These results indicate that induction of ischemic tolerance could constitute a fertile avenue for the development of new therapeutic strategies for diabetic retinopathy treatment.