Vitreous and aqueous concentrations of proangiogenic, antiangiogenic factors and other cytokines in diabetic retinopathy patients with macular edema: Implications for structural differences in macular profiles

Role of inflammation in diabetic macular edema and neovascular age-related macular degeneration

Diabetic macular edema (DME) and neovascular age-related macular degeneration (nAMD) are multifactorial disorders that affect the macula and cause significant vision loss. Although inflammation and neoangiogenesis are hallmarks of DME and nAMD, respectively, they share some biochemical mediators. While inflammation is a trigger for the processes that lead to the development of DME, in nAMD inflammation seems to be the consequence of retinal pigment epithelium and Bruch membrane alterations. These pathophysiologic differences may be the key issue that justifies the difference in treatment strategies. Vascular endothelial growth factor inhibitors have changed the treatment of both diseases, however, many patients with DME fail to achieve the established therapeutic goals. From a clinical perspective, targeting inflammatory pathways with intravitreal corticosteroids has been proven to be effective in patients with DME. On the contrary, the clinical relevance of addressing inflammation in patients with nAMD has not been proven yet. We explore the role and implication of inflammation in the development of nAMD and DME and its therapeutical relevance.

Ocular Vascular Diseases: From Retinal Immune Privilege to Inflammation

The eye is an immune privileged tissue that insulates the visual system from local and systemic immune provocation to preserve homeostatic functions of highly specialized retinal neural cells. If immune privilege is breached, immune stimuli will invade the eye and subsequently trigger acute inflammatory responses. Local resident microglia become active and release numerous immunological factors to protect the integrity of retinal neural cells. Although acute inflammatory responses are necessary to control and eradicate insults to the eye, chronic inflammation can cause retinal tissue damage and cell dysfunction, leading to ocular disease and vision loss. In this review, we summarized features of immune privilege in the retina and the key inflammatory responses, factors, and intracellular pathways activated when retinal immune privilege fails, as well as a highlight of the recent clinical and research advances in ocular immunity and ocular vascular diseases including retinopathy of prematurity, age-related macular degeneration, and diabetic retinopathy.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Bioengineering approaches for modelling retinal pathologies of the outer blood-retinal barrier

Alterations of the junctional complex of the outer blood-retinal barrier (oBRB), which is integrated by the close interaction of the retinal pigment epithelium, the Bruch's membrane, and the choriocapillaris, contribute to the loss of neuronal signalling and subsequent vision impairment in several retinal inflammatory disorders such as age-related macular degeneration and diabetic retinopathy. Reductionist approaches into the mechanisms that underlie such diseases have been hindered by the absence of adequate in vitro models using human cells to provide the 3D dynamic architecture that enables expression of the in vivo phenotype of the oBRB. Conventional in vitro cell models are based on 2D monolayer cellular cultures, unable to properly recapitulate the complexity of living systems. The main drawbacks of conventional oBRB models also emerge from the cell sourcing, the lack of an appropriate Bruch's membrane analogue, and the lack of choroidal microvasculature with flow. In the last years, the advent of organ-on-a-chip, bioengineering, and stem cell technologies is providing more advanced 3D models with flow, multicellularity, and external control over microenvironmental properties. By incorporating additional biological complexity, organ-on-a-chip devices can mirror physiologically relevant properties of the native tissue while offering additional set ups to model and study disease. In this review we first examine the current understanding of oBRB biology as a functional unit, highlighting the coordinated contribution of the different components to barrier function in health and disease. Then we describe recent advances in the use of pluripotent stem cells-derived retinal cells, Bruch's membrane analogues, and co-culture techniques to recapitulate the oBRB. We finally discuss current advances and challenges of oBRB-on-a-chip technologies for disease modelling.

Changes in aqueous and vitreous inflammatory cytokine levels in proliferative diabetic retinopathy: a systematic review and meta-analysis

BACKGROUND

Diabetic retinopathy is a major complication of diabetes mellitus, where in its most advanced form ischemic changes lead to the development of retinal neovascularization, termed proliferative diabetic retinopathy (PDR). While the development of PDR is often associated with angiogenic and inflammatory cytokines, studies differ on which cytokines are implicated in disease pathogenesis and on the strength of these associations. We therefore conducted a systematic review and meta-analysis to quantitatively assess the existing body of data on intraocular cytokines as biomarkers in PDR.

METHODS

A comprehensive search of the literature without year limitation was conducted to January 18, 2021, which identified 341 studies assessing vitreous or aqueous cytokine levels in PDR, accounting for 10379 eyes with PDR and 6269 eyes from healthy controls. Effect sizes were calculated as standardized mean differences (SMD) of cytokine concentrations between PDR and control patients.

RESULTS

Concentrations (SMD, 95% confidence interval, and p-value) of aqueous IL-1β, IL-6, IL-8, MCP-1, TNF-α, and VEGF, and vitreous IL-2, IL-4, IL-6, IL-8, angiopoietin-2, eotaxin, erythropoietin, GM-CSF, GRO, HMGB-1, IFN-γ, IGF, IP-10, MCP-1, MIP-1, MMP-9, PDGF-AA, PlGF, sCD40L, SDF-1, sICAM-1, sVEGFR, TIMP, TNF-α, and VEGF were significantly higher in patients with PDR when compared to healthy nondiabetic controls. For all other cytokines no differences, failed sensitivity analyses or insufficient data were found.

CONCLUSIONS

This extensive list of cytokines speaks to the complexity of PDR pathogenesis, and informs future investigations into disease pathogenesis, prognosis, and management.

Pigment epithelium-derived factor engineered to increase glycosaminoglycan affinity while maintaining bioactivity

Pigment epithelium-derived factor (PEDF) is a secreted protein that is essential in tissue homeostasis and is involved in multiple functions in the eye, such as antiangiogenesis and neuroprotection. However, short retention in the retinal microenvironment can limit its therapeutic effects. In this study, we modified the amino acid sequence of PEDF to increase its affinity for heparin and hyaluronic acid (HA), which are negatively charged extracellular matrix (ECM) molecules. HA is the major component of the vitreous humor. We selectively converted neutral or anionic residues into cationic residues to obtain engineered PEDF (ePEDF). Using in vitro binding assays, we demonstrate that ePEDF had higher affinity for heparin and HA than wild-type PEDF (wtPEDF). ePEDF exhibited antiangiogenic and retinal survival bioactivities. It inhibited endothelial cell proliferation and tube formation in vitro. In an ex vivo model mimicking retinal degeneration, ePEDF protected photoreceptors from cell death. The findings suggest that protein engineering is an approach to develop active PEDF with higher ECM affinity to potentially improve its retention in the retina microenvironment and in turn make it a more efficient therapeutic drug for retinal diseases.

Changes in aqueous and vitreous inflammatory cytokine levels in diabetic macular oedema: a systematic review and meta-analysis

Diabetic macular oedema (DME) is considered a chronic inflammatory disease associated with aberrations in many intraocular cytokines. Studies assessing the role of these cytokines as biomarkers in the diagnosis and management of DME have demonstrated inconsistent findings. We quantitatively summarized data related to 116 candidate aqueous and vitreous inflammatory cytokines as biomarkers in DME. A systematic search without year limitation was performed up to 19 October 2020. Studies were included if they provided data on aqueous or vitreous cytokine concentrations in patients with DME. Effect sizes were generated as standardized mean differences (SMDs) of cytokine concentrations between patients with DME and controls. Data were extracted from 128 studies that included 4163 study eyes with DME and 1281 control eyes. Concentrations (standard mean difference, 95% confidence interval and p-value) of aqueous IL-6 (1.28, 0.57-2.00, p = 0.004), IL-8 (1.06, 0.74-1.39, p < 0.00001), MCP-1 (1.36, 0.57-2.16, p = 0.0008) and VEGF (1.31, 1.01-1.62, p < 0.00001) and vitreous VEGF (2.27, 1.55-2.99, p < 0.00001) were significantly higher in patients with DME (n = 4163) compared to healthy controls (n = 1281). No differences, failed sensitivity analyses or insufficient data were found between patients with DME and healthy controls for the concentrations of the remaining cytokines. This analysis implicates multiple cytokine biomarker candidates other than VEGF in DME and clarifies previously reported inconsistent associations. As the therapeutic options for DME expand to include multiple agents with multiple targets, it will be critical to manage the treatment burden with tailored therapy that optimizes outcomes and minimizes treatment burden. Intraocular cytokines have the promise of providing a robust individualized assessment of disease status and response to therapy. We have identified key candidate cytokines that may serve as biomarkers in individualized treatment algorithms.

The Vitreous Ecosystem in Diabetic Retinopathy: Insight into the Patho-Mechanisms of Disease

Diabetic retinopathy is one of the leading causes of blindness in the world with the incidence of disease ever-increasing worldwide. The vitreous humor represents an extensive and complex interactive arena for cytokines in the diabetic eye. In recent decades, there has been significant progress in understanding this environment and its implications in disease pathophysiology. In this review, we investigate the vitreous ecosystem in diabetic retinopathy at the molecular level. Areas of concentration include: the current level of knowledge of growth factors, cytokine and chemokine mediators, and lipid-derived metabolites in the vitreous. We discuss the molecular patho-mechanisms of diabetic retinopathy based upon current vitreous research.

Delivery Systems of Retinoprotective Proteins in the Retina

Retinoprotective proteins play important roles for retinal tissue integrity. They can directly affect the function and the survival of photoreceptors, and/or indirectly target the retinal pigment epithelium (RPE) and endothelial cells that support these tissues. Retinoprotective proteins are used in basic, translational and in clinical studies to prevent and treat human retinal degenerative disorders. In this review, we provide an overview of proteins that protect the retina and focus on pigment epithelium-derived factor (PEDF), and its effects on photoreceptors, RPE cells, and endothelial cells. We also discuss delivery systems such as pharmacologic and genetic administration of proteins to achieve photoreceptor survival and retinal tissue integrity.

Reproducing diabetic retinopathy features using newly developed human induced-pluripotent stem cell-derived retinal Müller glial cells

Muller glial cells (MGCs) are responsible for the homeostatic and metabolic support of the retina. Despite the importance of MGCs in retinal disorders, reliable and accessible human cell sources to be used to model MGC-associated diseases are lacking. Although primary human MGCs (pMGCs) can be purified from post-mortem retinal tissues, the donor scarcity limits their use. To overcome this problem, we developed a protocol to generate and bank human induced pluripotent stem cell-derived MGCs (hiMGCs). Using a transcriptome analysis, we showed that the three genetically independent hiMGCs generated were homogeneous and showed phenotypic characteristics and transcriptomic profile of pMGCs. These cells expressed key MGC markers, including Vimentin, CLU, DKK3, SOX9, SOX2, S100A16, ITGB1, and CD44 and could be cultured up to passage 8. Under our culture conditions, hiMGCs and pMGCs expressed low transcript levels of RLPB1, AQP4, KCNJ1, KCJN10, and SLC1A3. Using a disease modeling approach, we showed that hiMGCs could be used to model the features of diabetic retinopathy (DR)-associated dyslipidemia. Indeed, palmitate, a major free fatty acid with elevated plasma levels in diabetic patients, induced the expression of inflammatory cytokines found in the ocular fluid of DR patients such as CXCL8 (IL-8) and ANGPTL4. Moreover, the analysis of palmitate-treated hiMGC secretome showed an upregulation of proangiogenic factors strongly related to DR, including ANG2, Endoglin, IL-1β, CXCL8, MMP-9, PDGF-AA, and VEGF. Thus, hiMGCs could be an alternative to pMGCs and an extremely valuable tool to help to understand and model glial cell involvement in retinal disorders, including DR.

Expression of Neovascular Associated Factors PEDF and αB-crystallin in Human Lens Epithelial Cells

Objective: To investigate the expression of pigment epithelium-derived factor (PEDF) and αB-crystallin in human lens epithelial cells (LEC) and explore their relationships with diabetes. Methods: Lens anterior capsules attached with LEC were collected from cataract surgeries in patients with or without diabetes, and grouped as following: non-diabetes mellitus (NDM) group, no diabetic retinopathy (NDR) group, non-proliferative diabetic retinopathy (NPDR) group and proliferative diabetic retinopathy (PDR) group. The expression of PEDF and αB-crystallin in all groups was determined by Western blot and immunofluorescence assay. Results: PEDF and αB-crystallin protein were both detected in LEC. PEDF was mainly distributed in the cytoplasm, whereas αB-crystallin was present in both cytoplasm and nucleus. The levels of PEDF protein and αB-crystallin protein in LEC were significantly increased with the appearance and aggravation of diabetic retinopathy (DR) (p < .01). Conclusion: The expression of PEDF and αB-crystallin protein is both positively correlated with the progression of DR, which may contribute to the regulation of iris neovascularization.

The Effects of the CXCR4 Antagonist, AMD3465, on Human Retinal Vascular Endothelial Cells (hRVECs) in a High Glucose Model of Diabetic Retinopathy

BACKGROUND High blood glucose levels in diabetes result in retinal angiogenesis, which is the key feature of diabetic retinopathy. This study aimed to investigate the effects of the CXCR4 antagonist, AMD3465, on human retinal vascular endothelial cells (hRVECs) [i]in vitro[/i]. MATERIAL AND METHODS Cell viability and the protein expression levels of CXCR4 and stromal cell-derived factor 1 (SDF-1) were evaluated in high glucose (HG)-treated human retinal vascular endothelial cells (hRVECs). The cell counting kit 8 (CCK-8) assay, the colony formation assay, immunofluorescence, and Western blot were used to investigate the effects of AMD3465 on hRVEC cell viability, colony formation, cell proliferation, and expression of CXCR4 and SDF-1. Cell apoptosis and angiogenesis were assessed by flow cytometry and Western blot. RESULTS Treatment with high glucose reduced the viability of hRVECs and increased the protein expression levels of CXCR4 and SDF-1. Following treatment with AMD3465, the colony formation capacity and cell proliferation in hRVECs increased, and there was a significant reduction in apoptosis rate compared with the untreated cells. AMD3465 significantly reduced the expression of angiogenesis-associated proteins, including ICAM1, VCAM1, VEGF, and AngII. AMD3465 significantly reduced the protein expression levels of TNF-α, IL-1β, NF-κB, and p-p65. CONCLUSIONS The CXCR4 antagonist, AMD3465, reduced apoptosis of HG-treated hRVECs in an [i]in vitro[/i] model of diabetic retinopathy.

Role of oxidative stress, inflammation, hypoxia and angiogenesis in the development of diabetic retinopathy

Diabetic retinopathy (DR) is a retinal disease which is one of the most severe complications occuring due to diabetes mellitus and is a major cause of blindness. Patients who have diabetes mellitus for number of years develop characteristic group of lesions in the retina which leads to Diabetic retinopathy. It is a multifactorial condition occuring due to complex cellular interactions between biochemical and metabolic abnormalities taking place in all retinal cells. Considerable research efforts in the past 20 years have suggested that the microvasculature of the retina responds to hyperglycemia through a number of biochemical changes, which includes polyol pathway, protein kinase C activation, upregulation of advanced glycation end products formation and renin angiotensin system activation. Various previous studies had suggest that interaction of these biochemical changes may cause a cascade of events, such as apoptosis, oxidative stress, inflammation and angiogenesis which can lead to the damage of a diabetic retina, causing DR. This highlights that oxidative stress, inflammation, angiogenesis-related factors triggers the occurrence of retinal complication in diabetes are highlighted.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Retinal vascular calibre changes after intravitreal bevacizumab or dexamethasone implant treatment for diabetic macular oedema

PURPOSE

To compare changes in retinal vascular calibre after 2 years of treatment with intravitreal bevacizumab (BVZ) or dexamethasone implant (DEX) in patients with centre-involving diabetic macular oedema (DMO).

METHODS

At baseline, 88 eyes of 61 patients with DMO were recruited in a prospective, multicentre, randomised, single-masked clinical trial. Of these subjects, 22 BVZ-treated (52%) and 22 DEX-treated (48%) eyes of 34 patients (56%) had gradable retinal photographs at both the baseline and 24-month visits. Retinal vascular calibre was measured from digital fundus photographs and summarised as central retinal artery (CRAE) and vein (CRVE) equivalents in all gradable eyes at baseline and 24 months.

RESULTS

At 24 months, 40.9% of BVZ and 45.5% of DEX eyes gained 10 or more letters (p=0.77). There was concurrent reduction in mean central macular thickness, -157.7 μm in BVZ and -192.5 μm in DEX-treated eyes (p=0.40). DEX-treated eyes showed a statistically significant reduction in CRVE compared with BVZ-treated eyes, with a mean change from baseline of -31.78 to +4.34 µm, respectively (p<0.001). CRAE showed a non-statistically significant trend towards reduction over time in DEX-treated eyes compared with BVZ-treated eyes, with a mean change from baseline of -6.09 and +1.66, respectively (p=0.077).

CONCLUSIONS

DEX had a significant narrowing effect on venular diameter in eyes with DMO not seen with BVZ. The changes in retinal vascular calibre suggest that these agents have a differing actions effects retinal vasculature and thereby suggest a potentially different mechanism of action on reducing DMO.

TRIAL REGISTRATION NUMBER

NCT01298076.

Biomarkers of Diabetic Retinopathy

Diabetic retinopathy (DR), a leading cause of acquired vision loss, is a microvascular complication of diabetes. While traditional risk factors for diabetic retinopathy including longer duration of diabetes, poor blood glucose control, and dyslipidemia are helpful in stratifying patient's risk for developing retinopathy, many patients without these traditional risk factors develop DR; furthermore, there are persons with long diabetes duration who do not develop DR. Thus, identifying biomarkers to predict DR or to determine therapeutic response is important. A biomarker can be defined as a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. Incorporation of biomarkers into risk stratification of persons with diabetes would likely aid in early diagnosis and guide treatment methods for those with DR or with worsening DR. Systemic biomarkers of DR include serum measures including genomic, proteomic, and metabolomics biomarkers. Ocular biomarkers including tears and vitreous and retinal vascular structural changes have also been studied extensively to prognosticate the risk of DR development. The current studies on biomarkers are limited by the need for larger sample sizes, cross-validation in different populations and ethnic groups, and time-efficient and cost-effective analytical techniques. Future research is important to explore novel DR biomarkers that are non-invasive, rapid, economical, and accurate to help reduce the incidence and progression of DR in people with diabetes.

The Effect of Age on Dexamethasone Intravitreal Implant (Ozurdex®) Response in Macular Edema Secondary to Branch Retinal Vein Occlusion

PURPOSE

To investigate the effect of age on dexamethasone intravitreal implant (Ozurdex®) response in macular edema secondary to branch retinal vein occlusion (BRVO).

METHODS

Seventy-three eyes of 73 patients with macular edema secondary to BRVO were recruited in the study. The patients in the study were divided into the following four groups according to their ages: group 1 (<60 years), group 2 (60-69 years), group 3 (70-79 years), and group 4 (≥80 years). Single-dose Ozurdex injection was applied to all patients. The effectiveness of Ozurdex treatment on macular edema is evaluated via optical coherence tomography (OCT) according to the age groups.

RESULTS

Two months after Ozurdex injection, mean reduction of central retinal thickness in groups 1, 2, 3, and 4 were -466.4 ± 149.6, -379.7 ± 238.7, -280.1 ± 233.0, and -180.5 ± 81.4 µm, respectively. This reduction of central retinal thickness decreased with aging (p = 0.001). Also, ages of patients were negatively correlated with the mean reduction of central retinal thickness for the whole study group (r = -0.439, p < 0.001).

CONCLUSION

Our study revealed that the effectiveness of Ozurdex treatment decreases with aging.

Evaluation of foveal photoreceptor layer in eyes with macular edema associated with branch retinal vein occlusion after ozurdex treatment

The aim of this study was to evaluate the central retinal thickness (CRT), outer nuclear layer thickness (ONLT), photoreceptor layer thickness (PLT), photoreceptor layer integrity, and the correlation between visual acuity and PLT in eyes with branch retinal vein occlusion (BRVO) 2 months after treatment with intravitreal dexamethasone implant (Ozurdex; Allergan, Inc, Irvine, CA). In this prospective study, 32 eyes of 32 patients were enrolled. A single injection of Ozurdex was administered to all the patients. CRT, ONLT, and PLT were measured using spectral-domain optical coherence tomography before and 2 months after the injection. Best-corrected visual acuity (BCVA [logMAR]) and photoreceptor cell integrity were also evaluated. The average CRT, ONLT, PLT, and BCVA values for the sample group before the treatment were as follows: 707 ± 261, 608 ± 288, 70 ± 25, and 0.96 ± 0.22 µm, respectively. The average CRT, ONLT, PLT, and BCVA values for the sample group 2 months after the Ozurdex injection were as follows: 299 ± 149, 211 ± 138, 77 ± 20, and 0.63 ± 0.30 µm, respectively (p < 0.05). Two months after the Ozurdex injection, BCVA correlated with ONLT and PLT (r = 0.365, p = 0.048 and r = -0.488, p = 0.021, respectively), whereas BCVA was not correlated with CRT (r = 0.239, p = 0.189). Photoreceptor layer is associated with the visual function of eyes with macular edema secondary to BRVO. Also, ONLT seems to be more closely related to visual acuity improvement than CRT decrement.

The potentialities proteomic analysis of ocular fluids and tissues in different ophthamic disordeers

The article presents a review of current researches in using the proteomic analysis for different eye diseases diagnosis. Special attention is paid to tear fluid and aqueous humor mass-spectrometry results in primary open-angle glaucoma, and to the possibility of using this method for diagnosis at disease early stages.

Proteome analysis of retinal glia cells-related inflammatory cytokines in the aqueous humour of diabetic patients

PURPOSE

Retinal glia cells (RGC) activation and release of inflammatory cytokines have been associated with development of diabetic retinopathy (DR). In this study, we evaluated by protein array the presence of aqueous humour (AH) cytokines secreted by RGC in patients with diabetes without DR and with mild DR.

METHODS

This is a cross-sectional, case-control study. Thirty-five subjects (diabetics and controls) underwent full ophthalmic examination and AH samples collection before cataract surgery at the Department of Ophthalmology University of Padova. AH samples were analysed for total protein concentration (Bradford method) and RGC-related inflammatory cytokines using glass chip protein arrays.

RESULTS

Twelve diabetic patients without DR, 11 diabetic patients with mild DR and 12 non-diabetic controls were included. There was no significant difference in total protein concentration among the 3 groups. Interleukin IL-1β, IL-3, interferon gamma (IFN-ɣ), (IFN-ɣ)-induced protein (IP)-10 and monocyte chemotactic protein (MCP)-2 were significantly increased in diabetics versus controls. IFN-ɣ, IL-1α, IL-3 and MCP-2 were significantly increased in diabetics without DR versus controls, whereas granulocyte-macrophage colony-stimulating factor (GM-CSF), IFN-ɣ, IL-10, IP-10, regulated and normal T cell expressed and secreted (RANTES), and soluble tumour necrosis factor receptor (sTNF-R)II were significantly increased in diabetics with mild DR versus controls. Macrophage inflammatory protein (MIP-1β), GMCSF, RANTES and sTNF-RII were significantly increased in diabetics with mild DR versus diabetics without DR (p < 0.05 at least for all).

CONCLUSIONS

Differences in expression profile of AH cytokines between diabetics, without and with mild DR, and controls have been documented. Retinal neuroinflammatory biomarkers of RGC activation evaluated in AH by protein array analysis could guide in detecting specific phenotypes with potential for personalized management.

The role of pharmacogenetics and advances in gene therapy in the treatment of diabetic retinopathy

Diabetic retinopathy (DR) and its complications such as diabetic macular edema continue to remain a major cause for legal blindness in the developed world. While the introduction of anti-tVEGF agents has significantly improved visual outcomes of patients with DR, unpredictable response, largely due to genetic polymorphisms, appears to be a challenge with this therapy. With advances in identification of various genetic biomarkers, novel therapeutic strategies consisting of gene transfer are being developed and tested for patients with DR. Application of pharmacogenetic principles appears to be a promising futuristic strategy to attenuate diabetes-mediated retinal vasculopathy. In this comprehensive review, data from recent studies in the field of pharmacogenomics for the treatment of DR have been provided.

Regulatory SNPs Alter the Gene Expression of Diabetic Retinopathy Associated Secretary Factors

OBJECTIVES

Diabetic retinopathy (DR) is a common microvascular complication in both type I and type II diabetes. Several previous reports indicated the serum centration of some secretary factors were highly associated with DR. Therefore, we hypothesis regulatory SNPs (rSNPs) genotype in secretary factors may alter these gene expression and lead to DR.

METHODS

At first, pyrosequencing were applying to screen the SNPs which present allele frequency different in DR and DNR. Then individual genotyping was processed by Taqman assays in Taiwanese DR and DNR patients. To evaluate the effect of SNP allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs.

RESULTS

We found the frequencies of the CC, CG, and GG genotype of the rs2010963 polymorphism were 15.09%, 47.14%, and 37.74% in DR and 12.90%, 19.35%, and 67.74% in DNR, respectively (p = 0.0205). The prevalence of DR was higher (p = 0.00793) in patients with the CC or CG genotype (62.26% and 32.26% for DR and DNR, respectively) compared with the patients with the GG genotype. To evaluate the effect of rs2010963-C allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs. The rs2010963-C reporter showed 1.6 to 2-fold higher luciferase activity than rs2010963-G in 3 cell lines.

CONCLUSION

Our data proposed rs2010963-C altered the expression level of VEGFA in different tissues. We suggested small increase but long term exposure to VEGFA may lead to DR finally.

Disruption of Fractalkine Signaling Leads to Microglial Activation and Neuronal Damage in the Diabetic Retina

Fractalkine (CX3CL1 or FKN) is a membrane-bound chemokine expressed on neuronal membranes and is proteolytically cleaved to shed a soluble chemoattractant domain. FKN signals via its unique receptor CX3CR1 expressed on microglia and other peripheral leukocytes. The aim of this study is to determine the role of CX3CR1 in inflammatory-mediated damage to retinal neurons using a model of diabetic retinopathy. For this, we compared neuronal, microglial, and astroglial densities and inflammatory response in nondiabetic and diabetic (Ins2^Akita) CX3CR1-wild-type and CX3CR1-deficient mice at 10 and 20 weeks of age. Our results show that Ins2^Akita CX3CR1-knockout mice exhibited (a) decreased neuronal cell counts in the retinal ganglion cell layer, (b) increased microglial cell numbers, and (c) decreased astrocyte responses comparable with Ins2^Akita CX3CR1-Wild-type mice at 20 weeks of age. Analyses of the inflammatory response using PCR arrays showed several inflammatory genes differentially regulated in diabetic tissues. From those, the response in Ins2^Akita CX3CR1-deficient mice at 10 weeks of age revealed a significant upregulation of IL-1β at the transcript level that was confirmed by enzyme-linked immunosorbent assay in soluble retinal extracts. Overall, IL-1β, VEGF, and nitrite levels as a read out of nitric oxide production were abundant in Ins2^Akita CX3CR1-deficient retina. Notably, double immunofluorescence staining shows that astrocytes act as a source of IL-1β in the Ins2^Akita retina, and CX3CR1-deficient microglia potentiate the inflammatory response via IL-1β release. Collectively, these data demonstrate that dysregulated microglial responses in absence of CX3CR1 contribute to inflammatory-mediated damage of neurons in the diabetic retina.

Enhanced Production of Nitric Oxide Leads to ATP Collapse in the Retinas of Otsuka Long-Evans Tokushima Fatty Rats, a Model of Human Diabetes

PURPOSE

We determined nitric oxide (NO) production via inducible NO synthase (iNOS) by hyperglycemia using the retina of Otsuka Long-Evans Tokushima Fatty rats (OLETF rats), and investigated the relationship between ATP contents and NO production in the retinas of OLETF rats.

METHODS

Long-Evans Tokushima Otsuka rats (LETO rats, normal rats) and OLETF rats (model rat for diabetes mellitus) aged 60 weeks of age were used. Plasma glucose (Glu) levels were determined using an Accutrend GCT System, and NO levels were measured by the microdialysis method as nitrite ([Formula: see text]). Cytochrome c oxidase (CCO) activity was measured using a Mitochondrial Isolation Kit and Cytochrome c Oxidase Assay Kit, and ATP levels were determined using a Sigma ATP Bioluminescent Assay Kit and a luminometer AB-2200.

RESULTS

[Formula: see text] levels in the retinas of OLETF rats were significantly higher than in LETO rats, and the [Formula: see text] levels in the retinas of 60-week-old OLETF rats increased with increasing Glu. CCO activity in the retinas of OLETF rats showed no significant difference from that in LETO rats; however, ATP levels in the retinas of OLETF rats were significantly lower than those in LETO rats. The oral administration of aminoguanidine or disulfiram, an iNOS inhibitor, attenuated the decrease in ATP levels in the retinas of 60-week-old OELTF rats.

CONCLUSION

The present study demonstrates that NO production via iNOS in the retinas of 60-week-old OLETF rats is caused by hyperglycemia, and that NO causes a decrease in ATP contents in the retinas of 60-week-old OELTF rats. It is possible that the low ATP contents caused by NO may affect the normal functioning of the retina in OLETF rats.

The effects of topical everolimus and sunitinib on corneal neovascularization

PURPOSE

To evaluate the effects of topical everolimus and sunitinib on corneal neovascularization (CNV).

METHODS

CNV was induced by application of silver nitrate to the cornea for all groups. Rats were divided into four groups of 10 rats each, and two corneas were obtained from each rat. Group I received 1 mg/ml everolimus, Group II received 0.5 mg/ml sunitinib, Group IV received no treatment (control group) and Group IV received 1% Dimethylsulfoxide (DMSO). All treatments were administrated twice daily for 2 weeks. The right corneas were used for extracellular signal-regulated kinase 1/2 (ERK 1/2) protein analysis by western blot analysis and the left corneas were used for ERK 1/2 and vascular endothelial growth factor-receptor (VEGFR-2) gene expression analysis by quantitative real-time PCR.

RESULTS

VEGFR-2 mRNA expression levels (ΔCt, median, min-max) were reduced in the everolimus 1.0 (0.25-1.81) and sunitinib 1.06 (0.24-2.68) treated groups compared with the control 4.74 (1.02-14.74) and DMSO groups 7.41 (0.72-13.10). The expression of ERK 1/2 protein and mRNA levels were reduced in everolimus group compared with the control group (p < 0.05). These differences were not seen between the sunitinib and control groups.

CONCLUSION

Topical administration of both everolimus and sunitinib reduced VEGFR-2 levels and inhibited CNV. In additon, everolimus reduced ERK 1/2 levels and seems to be more effective than sunitinib on CNV.

Increased Serum Chemerin Levels in Diabetic Retinopathy of Type 2 Diabetic Patients

PURPOSE

To compare serum levels of chemerin in type 2 diabetes mellitus (T2DM) with or without retinopathy, and to investigate the relationship between serum chemerin levels and diabetes retinopathy.

MATERIALS AND METHODS

A total of 60 T2DM patients and 20 healthy subjects (control group) were enrolled in this study. Of the T2DM patients, 15 had proliferative diabetic retinopathy (PDR group), 20 had non-proliferative retinopathy (NPDR group) and 25 had no retinopathy (T2DM group). Their serum samples were collected for testing the levels of chemerin, vascular endothelial growth factor (VEGF), C-reactive protein (CRP) and so on. The values were analyzed to compare the differences among the groups. Simple linear regression analysis and multiple stepwise linear regression analysis were used to determine the correlations between variables and chemerin. Trend chi-square was used to determine the correlations between chemerin and the severity of diabetic retinopathy (DR).

RESULTS

Chemerin levels in group PDR, NPDR and no DR were 147.56 ± 35.98 μg/l, 128.09 ± 16.33 μg/l and 113.19 ± 19.89 μg/l, with the significant difference across the three groups (p < 0.05). But there was no difference between control group (109.55 ± 20.98 μg/l) and T2DM group. Simple linear regression show that serum chemerin was correlated with duration of diabetes, body mass index (BMI), serum triglycerides, total-cholesterol, CRP and VEGF, and not correlated with age, systolic and diastolic blood pressure in T2DM patients. Stepwise regression analysis showed that BMI, CRP and VEGF were significantly associated with serum chemerin (p = 0.006, p = 0.011 and p = 0.036, respectively). In addition, the more severity of DR as the chemerin levels increased (χ(2) = 16.07, p < 0.001).

CONCLUSIONS

Serum levels of chemerin were significantly increased in the NPDR and PDR group. Elevated serum level of chemerin and its positive correlation with BMI, CRP and VEGF suggested that chemerin was associated with obesity, inflammation and neovascularization and might be involved in the development of DR.

Expression of cytokines on the iris of patients with neovascular glaucoma

PURPOSE

To determine the expression levels of cytokines, including growth factors, inflammatory cytokines, and cell migration associated factors on the iris from subjects with neovascular glaucoma (NVG).

METHODS

After receiving formal consent from 12 subjects with NVG secondary to proliferative diabetic retinopathy and 12 subjects with primary open angle glaucoma (POAG), trabeculectomy was performed and iris specimens were collected during the surgery. Each subject with NVG received intravitreal injection of bevacizumab 1 week prior to the surgery. The mRNA level of vascular endothelial growth factor, basic fibroblastic growth factor, placental-induced growth factor, interleukin-2, interleukin 6, tumour necrosis factor α, intercellular adhesion molecule 1 (ICAM-1) and integrin subunit αV were determined by real-time polymerase chain reaction. The mRNA levels were compared between the two groups.

RESULTS

The mRNA levels of all inflammatory cytokines and integrin subunit αV were significantly increased in the NVG group compared with POAG controls. However, the mRNA level of growth factors and ICAM-1 did not show any difference between the two groups.

CONCLUSIONS

Inflammatory process maybe an important cause of iris neovascularization in subjects with NVG in addition to growth factors alone. Further studies should focus on the effect of growth factors in different phases in the pathogenesis of NVG.

Vitreous humor in the pathologic scope: insights from proteomic approaches

The vitreous humor (VH) is the largest component of the eye. It is a colorless, gelatinous, highly hydrated matrix that fills the posterior segment of the eye between the lens and retina in vertebrates. In VH, a diversity of proteins that can influence retinal physiology is present, including growth factors, hormones, proteins with transporter activity, and enzymes. More importantly, the protein composition of VH has been described as being altered in a number of disease states. Therefore, attempts aiming at establishing a map of VH proteins and detecting putative biomarkers for ocular illness or protein fluctuations with putative physiologic significance were conducted over the last two decades, using proteomic approaches. Proteomic strategies often involve gel-based or LC techniques as sample fractioning approaches, subsequently coupled with MS procedures. This set of studies resulted in the proteomic characterization of a range of ocular disease samples, with particular incidence on diabetic retinopathy. However, practical therapeutic applications arising from these studies are scarce at the moment. A pertinent example of therapeutic targets arising from VH proteomics has emerged concerning vasoproliferative factors present in the vitreous, which should be involved in neovascularization and subsequent fibrovascular proliferation of the retina, in ocular disease context. Therefore, this review attempts to sum up the information acquired from the proteomic approaches to ocular disease conducted in VH samples, highlighting its clinical potential for disclosing ocular disease mechanisms and engendering pharmacological therapeutic treatments.

Elevation of serum apelin-13 associated with proliferative diabetic retinopathy in type 2 diabetic patients

AIM

To compare apelin-13, a ligand of G-protein-coupled receptor which has been shown to be involved in retinal angiogenesis, and vascular endothelial growth factor (VEGF) serum levels in type 2 diabetes mellitus (T2DM) with or without retinopathy, and to investigate the relationship between the serum concentration of apelin-13 and diabetes retinopathy.

METHODS

Sixty-nine patients with T2DM were enrolled. Of the 69 patients, 16 had proliferative diabetic retinopathy (PDR group), 23 had non-PDR (NPDR group) and 30 had no retinopathy (T2DM group). Subjects' information, including demographics, medical history, and use of medications were recorded. Their serum samples were collected for measuring the levels of C-reactive protein (CRP), serum lipid and glycosylated hemoglobin. Apelin-13 and VEGF serum levels were measured by enzyme-linked immunosorbent assay. Kruskal-Wallis test and one-way ANOVA were used to compare the differences among these groups. Chi-square test was used to assess categorical variables. Correlations between variables were investigated by Spearman rho correlation test and stepwise regression analysis. All statistical analyses were performed through SPSS 17.0 software.

RESULTS

Sex, age, body mass index (BMI), blood pressure, CRP, hemoglobin A1c (HbA1c) have no significantly difference in the three groups. Serum level of apelin-13 was significantly elevated in PDR group as compared with T2DM group (P=0.041). Differences of VEGF serum concentration in the three groups were statistically significant (P=0.007, P=0.007 and P<0.001, respectively). Spearman rho correlation test showed that serum apelin-13 was positively correlated with BMI, serum triglycerides, VEGF, but not with age, duration of diabetes, blood pressure, CRP, HbA1c and total-cholesterol. Stepwise regression analysis showed that BMI also significantly associated with serum apelin-13 (P=0.002), while VEGF and serum triglycerides were irrelevant.

CONCLUSION

This study elucidated a positive association of apelin-13 serum level with PDR, but not with VEGF. Apelin-13 may influence the promotion of PDR but unrelated with VEGF.

Effectiveness of the Dexamethasone Intravitreal Implant for Treatment of Patients with Diabetic Macular Oedema

Diabetic macular oedema (DMO) is a leading cause of vision loss in the working-age population worldwide. Corticosteroid drugs have been demonstrated to inhibit the expression of both the vascular endothelial growth factor (VEGF) gene and other anti-inflammatory mediators, such as prostaglandins. Triamcinolone, fluocinolone and dexamethasone are the main steroids that have been studied for the treatment of macular oedema. Over the last few years, several studies have suggested an important role for dexamethasone in the management of DMO. The dexamethasone intravitreal implant (DEX implant) (Ozurdex®; Allergan, Inc., Irvine, CA) is a novel approach approved by the US Food and Drug Administration (FDA) and by the EU for the intravitreal treatment of macular oedema after branch or central retinal vein occlusion, and for the treatment of non-infectious uveitis affecting the posterior segment of the eye. We reviewed manuscripts that had investigated the pharmacokinetics, efficacy and safety of the DEX implant regarding DMO treatment.

Effects of intravitreal injection of bevacizumab on inflammatory cytokines in the vitreous with proliferative diabetic retinopathy

BACKGROUND

To investigate the effects of preoperative intravitreal injection of bevacizumab (IVB) on the levels of 27 inflammatory cytokines, including interleukins (ILs) and vascular endothelial growth factor.

METHODS

From among 200 patients who had proliferative diabetic retinopathy and underwent vitrectomy in our department from September 2009 to October 2010, 8 study subjects met the enrollment criteria in which both eyes at nearly equivalent stages underwent vitrectomy. The first vitrectomy for each patient was performed without IVB (control group), whereas the second vitrectomy on the contralateral eye was performed with IVB treatment (1.25 mg/0.05 mL) 3 days before surgery (IVB group). Undiluted vitreous fluid was collected at the start of each vitrectomy. A multiplex assay was used to simultaneously determine the levels of 27 inflammatory cytokines and growth factors.

RESULTS

Mean vascular endothelial growth factor levels were significantly lower in the IVB group (519.69 pg/mL) than in the control group (11,807.44 pg/mL) (P = 0.012, Wilcoxon signed rank test). Moreover, the mean levels (IVB/control, pg/mL) of IL-1RA (38.50/62.31, P = 0.036), IL-5 (27.75/34.00, P = 0.018), IL-10 (433.63/1,995.94, P = 0.012), IL-12 (246.69/1,033.69, P = 0.012), IL-13 (707.50/1,450.38, P = 0.012), and interferon γ (71.13/84.69, P = 0.036) were significantly lower in the IVB group. No other significant differences were observed in the levels of the other 20 cytokines and growth factors between the 2 groups.

CONCLUSION

Preoperative IVB reduced not only the intravitreal vascular endothelial growth factor level but also the intravitreal levels of other inflammatory cytokines, including IL-1RA, IL-5, IL-10, IL-12, IL-13, and interferon γ. These results indicate the interaction of some cytokines in the vitreous fluid of proliferative diabetic retinopathy patients and suggest the possibility that preoperative IVB may not only reduce vascular proliferation by its direct antivascular endothelial growth factor effect but also modulate the inflammatory response through putative cytokine networks. None of the other cytokines examined were elevated after IVB.

Diabetic retinopathy: loss of neuroretinal adaptation to the diabetic metabolic environment

Diabetic retinopathy (DR) impairs vision of patients with type 1 and type 2 diabetes, associated with vascular dysfunction and occlusion, retinal edema, hemorrhage, and inappropriate growth of new blood vessels. The recent success of biologic treatments targeting vascular endothelial growth factor (VEGF) demonstrates that treating the vascular aspects in the later stages of the disease can preserve vision in many patients. It would also be highly desirable to prevent the onset of the disease or arrest its progression at a stage preceding the appearance of overt microvascular pathologies. The progression of DR is not necessarily linear but may follow a series of steps that evolve over the course of multiple years. Abundant data suggest that diabetes affects the entire neurovascular unit of the retina, with an early loss of neurovascular coupling, gradual neurodegeneration, gliosis, and neuroinflammation occurring before observable vascular pathologies. In this article, we consider the pathology of DR from the point of view that diabetes causes measurable dysfunctions in the complex integral network of cell types that produce and maintain human vision.

The role of O-GlcNAc signaling in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is a leading cause of blindness worldwide. Despite laser and surgical treatments, antiangiogenic and other therapies, and strict metabolic control, many patients progress to visual impairment and blindness. New insights are needed into the pathophysiology of diabetic retinopathy in order to develop new methods to improve the detection and treatment of disease and the prevention of blindness. Hyperglycemia and diabetes result in increased flux through the hexosamine biosynthetic pathway, which, in turn, results in increased PTM of Ser/Thr residues of proteins by O-linked β-N-acetylglucosamine (O-GlcNAc). O-GlcNAcylation is involved in regulation of many nuclear and cytoplasmic proteins in a manner similar to protein phosphorylation. Altered O-GlcNAc signaling has been implicated in the pathogenesis of diabetes and may play an important role in the pathogenesis of diabetic retinopathy. The goal of this review is to summarize the biology of the hexosamine biosynthesis pathway and O-GlcNAc signaling, to present the current evidence for the role of O-GlcNAc signaling in diabetes and diabetic retinopathy, and to discuss future directions for research on O-GlcNAc in the pathogenesis of diabetic retinopathy.

Intravitreal vascular endothelial growth factor

PURPOSE

To evaluate whether a specific pre-analytical stabilization regimen is needed for naïve vitreous taps to detect true values of intrinsic VEGF levels.

METHODS

Fourteen consecutive patients with different vitreomacular pathologies without blood-retina-barrier breakdown were scheduled for standard 23-gauge three-port pars plana vitrectomy, and naïve vitreous taps were sampled at the beginning of each procedure. The extracted vitreous specimen was split; one half was immediately stored in a -20 °C freezer (unstabilized samples) and the other half was instantly stabilized with albumin (2.5 % final conc.), followed by arginine stabilization (1.25 M final conc.) and consecutively stored in a -20 °C freezer (stabilized samples).

RESULTS

Intravitreal VEGF was detected in all 14 analyzed samples (100 %). VEGF levels were shown to be 46.5 pg/ml  ±  62.3 pg/ml (MV ± SD; range: 5.99-232.3 pg/ml) in unstabilized, and 120.4 pg/ml ± 94.4 pg/ml (range: 42.9 pg/ml-289.6 pg/ml) in stabilized vitreous samples. Intravitreal VEGF levels in stabilized vitreous samples were on average 2.6-fold, and thus significantly higher than in unstabilized taps of same eyes (p = 0.001, Wilcoxon test). VEGF levels in stabilized vitreous samples can be up to 8.5 times higher than in corresponding unstabilized vitreous taps of same eyes (bootstrap analysis). Intravitreal VEGF levels in unstabilized samples correlate with those in stabilized vitreous taps (r = 0.594; p = 0.025; Pearson).

CONCLUSIONS

An adequate pre-analytic stabilization regimen is needed to evaluate the most accurate intravitreal VEGF levels. This in turn will result in a better understanding of the physiological as well as pathological role of VEGF within the eye. Furthermore, knowing the true value of intravitreal VEGF levels will help to calculate the dosage of intravitrealy applied anti-VEGF drugs.

Neuropeptides, trophic factors, and other substances providing morphofunctional and metabolic protection in experimental models of diabetic retinopathy

Vision is the most important sensory modality for many species, including humans. Damage to the retina results in vision loss or even blindness. One of the most serious complications of diabetes, a disease that has seen a worldwide increase in prevalence, is diabetic retinopathy. This condition stems from consequences of pathological metabolism and develops in 75% of patients with type 1 and 50% with type 2 diabetes. The development of novel protective drugs is essential. In this review we provide a description of the disease and conclude that type 1 diabetes and type 2 diabetes lead to the same retinopathy. We evaluate existing experimental models and recent developments in finding effective compounds against this disorder. In our opinion, the best models are the long-term streptozotocin-induced diabetes and Otsuka Long-Evans Tokushima Fatty and spontaneously diabetic Torii rats, while the most promising substances are topically administered somatostatin and pigment epithelium-derived factor analogs, antivasculogenic substances, and systemic antioxidants. Future drug development should focus on these.

Intravitreal bevacizumab (Avastin) versus triamcinolone (Volon A) for treatment of diabetic macular edema: one-year results

PURPOSE

The objective was to compare retinal morphology and function following intravitreal injections of bevacizumab (Avastin) or triamcinolone (Volon A) in patients with early diabetic macular edema (DME).

PATIENTS AND METHODS

The study was planned as a randomized, prospective, interventional clinical trial. A total of 30 diabetic patients with treatment-naïve, clinically significant macular edema were included in this study and randomized to two equal groups. One group initially received three injections of 2.5 mg bevacizumab in monthly intervals. The second group received a single injection of 8 mg triamcinolone, followed by two sham interventions. Functional and anatomic results were evaluated monthly using ETDRS vision charts and spectral-domain optical coherence tomography. According to the study protocol, retreatment after 3 months was dependent on functional and anatomic outcome in a PRN regimen.

RESULTS

Baseline best corrected visual acuity (BCVA) was 0.30 logMAR and central retinal subfield thickness (CSRT) was 505 μm in the bevacizumab group and 0.32 logMAR and 490 μm CSRT in the triamcinolone group. After 3 months, BCVA improved to 0.23 logMAR (bevacizumab) and 358 μm CRST and 0.26 logMAR (triamcinolone) and 308 μm CSRT. After 12 months, BCVA further recovered in the bevacizumab group (0.18 logMAR) but slightly decreased in the triamcinolone group (0.36 logMAR).

CONCLUSION

Intravitreal bevacizumab and triamcinolone are both equally effective in reducing CSRT in early DME. After 6 months, rehabilitation of vision was comparable in both treatment arms, whereas at the final follow-up at month 12, BCVA was superior in the bevacizumab than in the triamcinolone sample. This may be related to cataract development following steroid treatment, as well as to substance-specific mechanisms within the angiogenic versus the inflammatory cascade.

Effects of soluble CD14 and cytokine levels on diabetic macular edema and visual acuity

PURPOSE

The pathogenesis of diabetic retinopathy has been suggested to be associated with ocular inflammation. Macrophages and monocytes that infiltrate the eye are known to express CD14. After shedding from the membrane-bound CD14, soluble CD14 (sCD14) is released, which could potentially activate inflammatory signaling. In this study, the authors investigated ocular fluid and serum levels of vascular endothelial growth factor (VEGF), sCD14, and other inflammatory cytokines in patients with diabetic macular edema (DME). Furthermore, the authors determined any potential correlation between these factors and visual acuity.

METHODS

Vitreous fluid, aqueous humor, and serum samples from 14 eyes with DME and 24 control eyes were investigated. Soluble CD14, interleukin 8, interferon-inducible protein 10, monocyte chemotactic protein 1, monokine induced by interferon γ, and VEGF were measured simultaneously by FACSCalibur flow cytometer. Visual acuity was measured in all patients with DME before surgery, with the assessors being blinded to the patients' diagnoses.

RESULTS

All factors were significantly elevated in vitreous fluid of DME eyes. Soluble CD14 and VEGF levels in vitreous fluid and aqueous humor were significantly higher in patients with DME than in nondiabetic controls (P < 0.05). In patients with DME, vitreous and aqueous humor concentrations of sCD14 correlated significantly. In these patients, vitreous fluid concentration of sCD14 correlated significantly with that of VEGF or interleukin 8 or monocyte chemotactic protein 1. In addition, there was a significant positive correlation between preoperative visual acuity and intraocular sCD14 concentrations.

CONCLUSION

Soluble CD14 may act as key regulator of VEGF production and contribute to the pathogenesis of diabetic retinopathy.

Apelin in epiretinal fibrovascular membranes of patients with retinopathy of prematurity and the changes after intravitreal bevacizumab

PURPOSE

Apelin, a novel cytokine, was reported to regulate angiogenesis. The aim of this study was to investigate the correlation between apelin and retinopathy of prematurity (ROP), between apelin and the other known angiogenic cytokines including vascular endothelial growth factor (VEGF) and hypoxia-induced factor-1a (HIF-1a).

METHODS

The study included 36 ROP patients who underwent vitrectomy. Previous intravitreal bevacizumab (IVB) was performed in 18 patients (IVB group). The other ROP eyes belonged to non-IVB group. Surgical removed membranes from 10 patients who underwent vitrectomy for idiopathic preretinal membranes or macular hole served as control. The expression of apelin and angiotensin-1-like receptor (APJ) in the excised membranes was examined by fluorescence immunostaining. Quantitative reverse transcription polymerase chain reaction was used to examine the expression of apelin, VEGF, and HIF-1a mRNA.

RESULTS

The density of neovascularization in fibrovascular membranes was significantly correlated with the age and postconception age of ROP patients (r = -0.94, P < 0.01; r = -0.83, P = 0.04). In the non-IVB group, colocalization of the endothelial marker CD31 with the marker for apelin and colocalization of CD31 and APJ were observed. In the IVB group, staining of apelin and APJ were positive, whereas the staining of CD31 was negative. Expression of apelin mRNA, HIF-1a mRNA, and VEGF mRNA were significantly higher in ROP membranes than idiopathic epiretinal membranes. Expression of apelin mRNA and VEGF mRNA significantly correlate with HIF-1a mRNA (r = 0.64, P = 0.04; and r = 0.96, P < 0.01, respectively), but the expression of apelin mRNA did not significantly correlate with VEGF mRNA (r = 0.491, P = 0.15).

CONCLUSION

The apelin/APJ system may be involved in the development of retinal neovascularization of ROP. The present results showed that the effect of apelin was related to HIF-1a but independent with VEGF.

Intraocular activation of angiogenic and inflammatory pathways in uveal melanoma

PURPOSE

To identify and quantify angiogenic and inflammatory cytokines in aqueous and vitreous humor in eyes with untreated uveal melanoma and to analyze clinicopathologic correlations.

METHODS

Intraocular fluid samples of patients (uveal melanoma aqueous n = 21, vitreous n = 34) and controls (cataract aqueous n = 41, vitreomacular traction aqueous n = 35, vitreous n = 36) were taken intraoperatively and analyzed using Luminex xMAP suspension array technology. Beadlyte kits were used for detection of 28 different cytokines.

RESULTS

Flt-3 ligand, interleukin (IL) 1α, IL-6, IL-8, interferon-γ inducible protein (IP)-10, monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein 1α, platelet-derived growth factor AA, and vascular endothelial growth factor were significantly elevated in aqueous and vitreous of melanoma eyes when compared with controls. Eotaxin was significantly elevated in aqueous, and IL-7 and RANTES were significantly elevated in vitreous samples of melanoma eyes. Interferon-γ inducible protein 10, macrophage inflammatory protein 1α (aqueous and vitreous), Flt-3 ligand, IL-6, IL-8, and MCP-1 (vitreous) correlated with tumor dimensions. Further correlations were found between infiltration of Bruch membrane and Flt-3 ligand, MCP-1 (aqueous and vitreous), IL-8, interferon-γ inducible protein 10, macrophage inflammatory protein 1α, and platelet-derived growth factor AA (vitreous). Analyzing 16 paired aqueous and vitreous melanoma samples, Flt-3 ligand, IL-7, interferon-γ inducible protein 10, MCP-1, and platelet-derived growth factor AA were significantly elevated in vitreous, and IL-1α and vascular endothelial growth factor in aqueous samples.

CONCLUSION

A range of significantly elevated angiogenic, inflammatory, and chemotactic cytokines in eyes with uveal melanoma supports the link between inflammation and tumorigenesis.