Immunological mechanisms in the pathogenesis of diabetic retinopathy

Rationale of Basic and Cellular Mechanisms Considered in Updating the Staging System for Diabetic Retinal Disease

Purpose

Hyperglycemia is a major risk factor for early lesions of diabetic retinal disease (DRD). Updating the DRD staging system to incorporate relevant basic and cellular mechanisms pertinent to DRD is necessary to better address early disease, disease progression, the use of therapeutic interventions, and treatment effectiveness.

Design

We sought to review preclinical and clinical evidence on basic and cellular mechanisms potentially pertinent to DRD that might eventually be relevant to update the DRD staging system.

Participants

Not applicable.

Methods

The Basic and Cellular Mechanisms Working Group (BCM-WG) of the Mary Tyler Moore Vision Initiative carefully and extensively reviewed available preclinical and clinical evidence through multiple iterations and classified these.

Main Outcome Measures

Classification was made into evidence grids, level of supporting evidence, and anticipated future relevance to DRD.

Results

A total of 40 identified targets based on pathophysiology and other parameters for DRD were grouped into concepts or evaluated as specific candidates. VEGFA, peroxisome proliferator-activated receptor-alpha related pathways, plasma kallikrein, and angiopoietin 2 had strong agreement as promising for use as biomarkers in diagnostic, monitoring, predictive, prognostic, and pharmacodynamic responses as well as for susceptibility/risk biomarkers that could underlie new assessments and eventually be considered within an updated DRD staging system or treatment, based on the evidence and need for research that would fit within a 2-year timeline. The BCM-WG found there was strong reason also to pursue the following important concepts regarding scientific research of DRD acknowledging their regulation by hyperglycemia: inflammatory/cytokines, oxidative signaling, vasoprotection, neuroprotection, mitophagy, and nutrients/microbiome.

Conclusion

Promising targets that might eventually be considered within an updated DRD staging system or treatment were identified. Although the BCM-WG recognizes that at this stage little can be incorporated into a new DRD staging system, numerous potential targets and important concepts deserve continued support and research, as they may eventually serve as biomarkers and/or therapeutic targets with measurable benefits to patients with diabetes.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Nuclear proteins and diabetic retinopathy: a review

Diabetic retinopathy (DR) is an eye disease that causes blindness and vision loss in diabetic. Risk factors for DR include high blood glucose levels and some environmental factors. The pathogenesis is based on inflammation caused by interferon and other nuclear proteins. This review article provides an overview of DR and discusses the role of nuclear proteins in the pathogenesis of the disease. Some core proteins such as MAPK, transcription co-factors, transcription co-activators, and others are part of this review. In addition, some current advanced treatment resulting from the role of nuclear proteins will be analyzes, including epigenetic modifications, the use of methylation, acetylation, and histone modifications. Stem cell technology and the use of nanobiotechnology are proposed as promising approaches for a more effective treatment of DR.

The Association of Systemic Endothelial Dysfunction With Diffuse Diabetic Macular Edema

Our aim was to assess whether systemic endothelial dysfunction, evaluated non-invasively by flow mediated dilation (FMD), is associated with diabetic macular edema (DME) and to determine if it is further impaired in patients with diffuse-DME. Consecutive patients (n = 84) with type-2 diabetes mellitus (T2DM) and diabetic retinopathy were enrolled. DME was not present in 38 (non-DME) and present in 46 patients; 25 with focal and 21 with diffuse-DME. No differences were detected between DME and non-DME groups regarding the clinical and demographic characteristics, except for the age of T2DM initiation (lower in non-DME). FMD values were significantly impaired in DME compared with non-DME patients, even after adjustment for multiple covariates (3.56 ± 1.03 vs 4.57 ± 1.25%, P = .003). Among DME patients, no differences were found concerning the clinical and demographic data, while FMD levels were significantly lower in diffuse-DME patients, compared with the focal-DME ones, regardless of the impact several confounders (2.88 ± 0.65 vs 4.08 ± 0.95%, P = .002). It is noteworthy that FMD values of non-DME and focal-DME patients did not differ significantly (4.52 ± 1.24 vs 4.21 ± 1.06%, P = .307). Moreover, among DME patients, impaired FMD was an independent predictor of diffuse-DME (odds ratio: 0.06, 95% CI 0.01-0.47, P = .007).

Aqueous humour interleukin-6 and vision outcomes with anti-vascular endothelial growth factor therapy

BACKGROUND

This analysis evaluated aqueous humour (AH) interleukin (IL)-6 concentrations and the association between AH IL-6 and visual outcomes in patients with neovascular age-related macular degeneration (nAMD) or diabetic macular oedema (DMO) receiving anti-vascular endothelial growth factor (VEGF) monotherapy.

METHODS

Post hoc analysis of the multicentre, double-masked, randomised HARBOR (NCT00891735) and READ-3 (NCT01077401) trials. HARBOR enrolled treatment-naïve nAMD patients. READ-3 enrolled treatment-naïve/previously treated DMO patients. HARBOR patients received ranibizumab 0.5 or 2.0 mg monthly or as needed; AH samples were collected at month 2, after two previous intravitreal injections. READ-3 patients received ranibizumab 0.5 or 2.0 mg as needed; AH samples were collected at baseline and months 3, 6, 9, and 12.

MAIN OUTCOME MEASURE

association between AH IL-6 concentrations and month 24 best-corrected visual acuity (BCVA).

RESULTS

In both trials (HARBOR, N = 36; READ-3, N = 137), patients with higher AH IL-6 concentrations had worse visual outcomes. HARBOR patients with low AH IL-6 concentrations at month 2 had a mean (95% CI) BCVA change at month 24 of +2.9 (-2.6, 8.3) letters, whereas patients with high AH concentrations had a mean (95% CI) BCVA change of -9.0 (-22.7, 4.7) letters. READ-3 patients with low AH concentrations at baseline had a mean (95% CI) BCVA change at month 12 of +9.3 (7.4, 11.3) letters, whereas patients with high AH concentrations had a mean (95% CI) BCVA change of +5.6 (2.2, 9.1) letters.

CONCLUSIONS

Higher IL-6 AH concentrations may predict suboptimal visual responses to anti-VEGF monotherapy in patients with nAMD/DMO.

Protective Effect of Curcumin on the Tight Junction Integrity and Cellular Senescence in Human Retinal Pigment Epithelium of Early Diabetic Retinopathy

Diabetic retinopathy (DR) is a secondary complication of diabetes that can lead to visual impairment and blindness. The retinal pigment epithelium (RPE) is a monolayer of pigment cells that forms the blood-retinal barrier (BRB) via tight junction (TJ) proteins and plays a crucial role in the physiological function of the retina. Hyperglycemia induces RPE death and BRB breakdown, which accelerates the process of DR. Curcumin, an active extract of Curcuma longa , has anti-inflammatory, antioxidant, antiapoptotic, and neuroprotective properties. However, the effect of Curcumin on the BRB under high glucose conditions remains unknown. This study aimed to investigate the protective effects of Curcumin on RPE physiology in vitro and in vivo . Curcumin significantly alleviated cell viability inhibition under high glucose conditions. Moreover, high glucose reduced extracellular signal-regulated kinase and Akt pathways activation to diminish RPE cell growth but reversed by Curcumin treatment. Curcumin protected not only TJ integrity but also retinoid regeneration through TJ proteins and isomerase modulation in diabetic retina. Furthermore, Curcumin decreased the expression of angiogenic factor to inhibit retinal neovascularization. Finally, Curcumin treatment markedly reduced apoptosis during hyperglycemia. In conclusion, Curcumin can alleviate the progression of DR by promoting RPE survival, TJ integrity, retinoid isomerase activity, RPE senescence inhibition, and neovascularization. Therefore, Curcumin exhibits high potential for use as a therapeutic agent for early DR.

RAGE plays key role in diabetic retinopathy: a review

RAGE is a multiligand receptor for the immunoglobulin superfamily of cell surface molecules and is expressed in Müller cells, vascular endothelial cells, nerve cells and RPE cells of the retina. Diabetic retinopathy (DR) is a multifactorial disease associated with retinal inflammation and vascular abnormalities and is the leading cause of vision loss or impairment in older or working-age adults worldwide. Therapies aimed at reducing the inflammatory response and unnecessary angiogenesis can help slow the progression of DR, which in turn can save patients' vision. To maximize the efficacy and minimize the side effects, treatments that target key players in the pathophysiological process of DR need to be developed. The interaction between RAGE and its ligands is involved in a variety of cytopathological alterations in the retina, including secretion of inflammatory factors, regulation of angiogenesis, oxidative stress, structural and functional changes, and neurodegeneration. In this review, we will summarize the pathologic pathways mediated by RAGE and its ligand interactions and discuss its role in the progression of diabetic retinopathy to explore potential therapeutic targets that are effective and safe for DR.

Intravitreal Triamcinolone Acetonide for Diabetic Macular Edema and Macular Edema Secondary to Retinal Vein Occlusion: A Meta-Analysis

BACKGROUND

The comparative safety and efficacy of different doses of intravitreal triamcinolone acetonide (IVTA) for diabetic macular edema (DME) and macular edema (ME) secondary to retinal vein occlusion (RVO) is unclear.

OBJECTIVES

This meta-analysis aimed to compare the safety and efficacy of different doses of IVTA in this setting.

METHODS

A systematic literature search for randomized clinical trials (RCTs) was conducted on Cochrane Library, Ovid MEDLINE, and EMBASE from January 2005 to May 2022. Studies that reported on patients with DME or ME secondary to RVO that received treatment with different doses of IVTA were included. A random-effects meta-analysis was performed. Cochrane's Risk of Bias Tool 2 was used to assess the risk of bias, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) guidelines were used to assess certainty of evidence.

RESULTS

Five RCTs reporting on 1,041 eyes at baseline were included in this meta-analysis. In eyes with ME secondary to RVO, high-dose (4 mg) IVTA achieved a significantly better change in best-corrected visual acuity (WMD = -4.75 ETDRS letters, 95% CI = [-7.73, -1.78], p = 0.002) and reduction in retinal thickness (WMD = -93.02 μm, 95% CI = [-153.23, -32.82], p = 0.002) at months 4-6 compared to low-dose (1-2 mg) IVTA. However, high-dose IVTA had a higher risk of intraocular pressure-related adverse events (RR = 2.99, 95% CI = [1.05, 8.50], p = 0.04) and cataract surgery (RR = 5.67, 95% CI = [3.09, 10.41], p < 0.00001) than low-dose IVTA in eyes with ME secondary to RVO. These efficacy and safety differences in high-dose and low-dose IVTA were not observed in DME eyes.

CONCLUSIONS

The RCT evidence in this setting is limited. High-dose IVTA achieved greater improvements in visual acuity and reductions in retinal thickness than low-dose IVTA at months 4-6. However, high-dose IVTA had a less favorable safety profile than low-dose IVTA. The significance of these outcomes was based on patients with ME secondary to RVO, but not DME.

The Past and Present Lives of the Intraocular Transmembrane Protein CD36

Cluster of differentiation 36 (CD36) belongs to the B2 receptors of the scavenger receptor class B family, which is comprised of single-chain secondary transmembrane glycoproteins. It is present in a variety of cell types, including monocytes, macrophages, microvascular endothelial cells, adipocytes, hepatocytes, platelets, skeletal muscle cells, kidney cells, cardiomyocytes, taste bud cells, and a variety of other cell types. CD36 can be localized on the cell surface, mitochondria, endoplasmic reticulum, and endosomes, playing a role in lipid accumulation, oxidative stress injury, apoptosis, and inflammatory signaling. Recent studies have found that CD36 is expressed in a variety of ocular cells, including retinal pigment epithelium (RPE), retinal microvascular endothelial cells, retinal ganglion cells (RGC), Müller cells, and photoreceptor cells, playing an important role in eye diseases, such as age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma. Therefore, a comprehensive understanding of CD36 function and downstream signaling pathways is of great significance for the prevention and treatment of eye diseases. This article reviews the molecular characteristics, distribution, and function of scavenger receptor CD36 and its role in ophthalmology in order to deepen the understanding of CD36 in eye diseases and provide new ideas for treatment strategies.

Safety and Effectiveness of Intravitreal Dexamethasone Implant (Ozurdex®) for the Treatment of Refractory Cystoid Macular Oedema (CMO) in Galway University Hospital

Aim:

The aim of this study is to assess the real-life effectiveness and safety of intravitreal Ozurdex in an Irish setting.

Background:

Ozurdex is an intravitreal dexamethasone implant that is used for the treatment of macular oedema secondary to retinal vein occlusion and diabetic macular oedema.

Methods:

This was a retrospective observational study of adult patients in University Hospital Galway who received an intravitreal dexamethasone implant (Ozurdex) for the treatment of cystoid macular oedema secondary to diabetic eye disease or retinal vein occlusion. The main outcome was the mean change in best-corrected visual acuity 3-6 months after the treatment.

Results and Discussion:

36 patients were included in the study. Overall, there was a 1.66 mean letter gain (SD 11.8) 3-6 months post-treatment. The proportion of patients who gained >10 letters was 15.6%. The mean reduction in CST was 110.6um (SD 255.7), and in the linear regression analysis, no variables were found to be significantly associated with a change in visual acuity. In terms of adverse events, 14.3% of patients had significant cataract progression and 20.6% of patients had a significant rise in IOP following intravitreal Ozurdex implant.

Conclusion:

Intravitreal Ozurdex was found to be safe and effective, supporting it as an appropriate second-line treatment in patients with refractory macular oedema secondary to diabetic eye disease and retinal vein occlusion. Further studies should be carried out to evaluate the possible predictors of visual acuity outcome.

Possible Role of Wnt Signaling Pathway in Diabetic Retinopathy

The core of impaired vision in working people suffering from insulin-dependent and noninsulin- dependent diabetes mellitus is diabetic retinopathy (DR). The Wnt Protein Ligands family influences various processes; this ensures the cells are able to interact and co-ordinate various mobile functions, including cell growth, division, survival, apoptosis, migration, and cell destiny. The extracellular Wnt signal activates other signals. It is seen that Wnt pathways play an important role in inflammation, oxidative stress, and angiogenesis. It has been illustrated that the canonically preserved Wnt signaling system has a vital role in the homeostasis of adulthood. Developmental disorders in each of these stages will lead to serious eye problems and eventually blindness. There is, therefore, a need to specifically organize and regulate the growth of ocular tissues. In tissue specification and polarities, axonal exhaust, and maintenance of cells, especially in the central nervous system, Wnt/frizzled pathways play an important role. Thus, Wnt route antagonists may act as have been possible therapeutic options in DR by inhibiting aberrant Wnt signals. Elaborative and continued research in this area will help in the advancement of current knowledge in the field of DR, and eventually, this can lead to the development of new therapeutic approaches.

Diabetic Macular Edema: Current Understanding, Molecular Mechanisms and Therapeutic Implications

Diabetic retinopathy (DR), with increasing incidence, is the major cause of vision loss and blindness worldwide in working-age adults. Diabetic macular edema (DME) remains the main cause of vision impairment in diabetic patients, with its pathogenesis still not completely elucidated. Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of DR and DME. Currently, intravitreal injection of anti-VEGF agents remains as the first-line therapy in DME treatment due to the superior anatomic and functional outcomes. However, some patients do not respond satisfactorily to anti-VEGF injections. More than 30% patients still exist with persistent DME even after regular intravitreal injection for at least 4 injections within 24 weeks, suggesting other pathogenic factors, beyond VEGF, might contribute to the pathogenesis of DME. Recent advances showed nearly all the retinal cells are involved in DR and DME, including breakdown of blood-retinal barrier (BRB), drainage dysfunction of Müller glia and retinal pigment epithelium (RPE), involvement of inflammation, oxidative stress, and neurodegeneration, all complicating the pathogenesis of DME. The profound understanding of the changes in proteomics and metabolomics helps improve the elucidation of the pathogenesis of DR and DME and leads to the identification of novel targets, biomarkers and potential therapeutic strategies for DME treatment. The present review aimed to summarize the current understanding of DME, the involved molecular mechanisms, and the changes in proteomics and metabolomics, thus to propose the potential therapeutic recommendations for personalized treatment of DME.

ICAM-1 on the luminal surface of endothelial cells is induced to a greater extent in mouse retina than in other tissues in diabetes

AIMS/HYPOTHESIS

Induction of intercellular adhesion molecule-1 (ICAM-1) has been implicated in the development of macrovascular and microvascular diseases such as diabetic retinopathy. Lesions of diabetic retinopathy are unique to the retina but the reason for this is unclear, as all tissues are exposed to the same hyperglycaemic insult. We tested whether diabetes induces ICAM-1 on the luminal surface of endothelial cells to a greater extent in the retina than in other tissues and the role of vision itself in that induction.

METHODS

Experimental diabetes was induced in C57Bl/6J, P23H opsin mutant and Gnat1-/- × Gnat2-/- double knockout mice using streptozotocin. The relative abundance of ICAM-1 on the luminal surface of endothelial cells in retina and other tissues was determined by conjugating anti-ICAM-1 antibodies to fluorescent microspheres (2 μm), injecting them intravenously and allowing them to circulate for 30 min. After transcardial perfusion, quantification of microspheres adherent to the endothelium in tissues throughout the body was carried out by fluorescent microscopy or flow cytometry. Mice injected with lipopolysaccharide (LPS) were used as positive controls. The difference in leucostasis between retinal and non-retinal vasculature was evaluated.

RESULTS

Diabetes significantly increased ICAM-1-mediated adherence of microspheres to retinal microvessels by almost threefold, independent of sex. In contrast, diabetes had a much smaller effect on endothelial ICAM-1 in other tissues, and more tissues showed a significant induction of endothelial ICAM-1 with LPS than with diabetes. The diabetes-induced increase in endothelial ICAM-1 in retinal vasculature was inhibited by blocking phototransduction in photoreceptor cells. Diabetes significantly increased leucostasis in the retina by threefold compared with a non-ocular tissue (cremaster).

CONCLUSIONS/INTERPRETATION

The diabetes-induced upregulation of ICAM-1 on the luminal surface of the vascular endothelium varies considerably among tissues and is highest in the retina. Induction of ICAM-1 on retinal vascular endothelial cells in diabetes is influenced by vision-related processes in photoreceptor cells. The unique presence of photoreceptors in the retina might contribute to the greater susceptibility of this tissue to vascular disease in diabetes.

Airborne fine particulate matter (PM2.5) damages the inner blood-retinal barrier by inducing inflammation and ferroptosis in retinal vascular endothelial cells

This study was the first to explore the effect of airborne fine particulate matter (PM_2.5) exposure on the inner blood-retinal barrier (iBRB). In this study, retinal vascular permeability and diameter were enhanced in the PM_2.5-exposed animal model (1 mg/mL PM_2.5, 10 μL per eye, 4 times per day, 3 days), together with observable retinal edema and increased inflammation level in retina. PM_2.5-induced cell damage in human retinal microvascular endothelial cells (HRMECs) occurred in a time- and dose-dependent manner. Decreased cell viability, proliferation, migration, and angiogenesis, as well as increased apoptosis and inflammation, were observed. Iron overload and excessive lipid oxidation were also discovered after PM_2.5 exposure (25, 50, and 100 μg/mL PM_2.5 for 24 h), along with significantly altered expression of ferroptosis-related genes, such as prostaglandin-endoperoxide synthase 2, glutathione peroxidase 4, and ferritin heavy chain 1. Moreover, Ferrostatin-1, an inhibitor of ferroptosis, evidently alleviated the PM_2.5-induced cytotoxicity of HRMECs. The present study investigated the in vivo effects of PM_2.5 on retinas, revealing that PM_2.5 exposure induced retinal inflammation, vascular dilatation, and caused damage to the iBRB. The crucial role of ferroptosis was discovered during PM_2.5-induced HRMEC cytotoxicity and dysfunction, indicating a potential precautionary target in air pollution-associated retinal vascular diseases.

Time dependent effects of prolonged hyperglycemia in zebrafish brain and retina

Prolonged hyperglycemia causes long-term vision complications and an increased risk of cognitive deficits. High blood sugar also confers an osmotic load/stress to cells. We assessed behavioral and neurochemical changes in zebrafish brain and retina following prolonged hyperglycemia for 4-weeks or 8-weeks. At each time point, behavior was assessed using 3-chamber choice task and optomotor response; tissue was then collected and levels of inflammatory markers, tight junction proteins, and neurotransmitters determined using Western Blots. After 4-weeks, brain levels of v-rel reticuloendotheliosis viral oncogene homolog A (avian) (RelA; NF-kB subunit), IkB kinase (IKK), and glial fibrillary acidic protein (GFAP) were significantly elevated; differences in zonula occludens-1 (ZO-1), claudin-5, glutamic acid decarboxylase (GAD), and tyrosine hydroxylase (TH) were not significant. In retina, significant differences were observed only for TH (decreased), Rel A (increased), and GFAP (increased) levels. Glucose-specific differences in initial choice latency and discrimination ratios were also observed. After 8-weeks, RelA, GAD, and TH were significantly elevated in both tissues; IKK and GFAP levels were also elevated, though not significantly. ZO-1 and claudin-5 levels osmotically decreased in retina but displayed an increasing trend in glucose-treated brains. Differences in discrimination ratio were driven by osmotic load. OMRs increased in glucose-treated fish at both ages. In vivo analysis of retinal vasculature suggested thicker vessels after 4-weeks, but thinner vessels at 8-weeks. In vitro, glucose treatment reduced formation of nodes and meshes in 3B-11 endothelial cells, suggesting a reduced ability to form a vascular network. Overall, hyperglycemia triggered a strong inflammatory response causing initial trending changes in tight junction and neuronal markers. Most differences after 4-weeks of exposure were observed in glucose-treated fish suggesting effects on glucose metabolism independent of osmotic load. After 8-weeks, the inflammatory response remained and glucose-specific effects on neurotransmitter markers were observed. Osmotic differences impacted cognitive behavior and retinal protein levels; protein levels in brain displayed glucose-driven changes. Thus, we not only observed differential sensitivities of retina and brain to glucose-insult, but also different cellular responses, suggesting hyperglycemia causes complex effects at the cellular level and/or that zebrafish are able to compensate for the continued high blood glucose levels.

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.

Regulation of inflammation by VEGF/BDNF signaling in mouse retinal Müller glial cells exposed to high glucose

The inflammatory changes seem to play an important role in the development of diabetic retinopathy (DR). Anti-VEGF therapy has been testified to inhibit inflammation in animal models of diabetes, but the detailed mechanisms during this process are not yet clear. Müller glial cells (MGCs) in the mammalian retina are deeply involved in DR, while the BDNF overexpression reduces inflammation in diabetic mice. In this research, we aimed to explore the relationship between VEGF and BDNF in mouse retinal MGCs during inflammation of diabetes. We examined the expression of glutamine-synthetase (GS), glial fibrillary acidic protein (GFAP), vascular-endothelial growth factor (VEGF), interleukin-1beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) at different time points after mouse retinal MGCs exposed to high glucose (25 mM). We also explored changes in the expression of brain-derived neurotrophic factor (BDNF), nuclear factor kappa B (NF-κB), IL-1β, and TNF-α in MGCs after treatments with anti-VEGF, VEGF siRNA, BDNF siRNA, BDNF recombination protein, and NF-κB inhibitor. In mouse retinal MGCs exposed to high glucose, BDNF was increased after treatments with anti-VEGF or VEGF siRNA. BDNF was decreased in MGCs from VEGF overexpressed mice. Moreover, the expressions of NF-κB, IL-1β, and TNF-α changed with BDNF: NF-κB, IL-1β, and TNF-α were increased after treatments with BDNF siRNA; NF-κB, IL-1β, and TNF-α were decreased after treatments with BDNF recombination protein. VEGF may regulate cytokines (IL-1β and TNF-α) by BDNF/NF-κB signaling pathway. The regulation of the VEGF/BDNF/NF-κB signaling pathway may be a significant therapeutic strategy for DR.

Correlation of Complement Activation in Aqueous and Vitreous in Patients With Proliferative Diabetic Retinopathy

Purpose

A growing body of evidence suggests complement dysregulation is present in the vitreous of patients with diabetic eye disease. Further translational study could be simplified if aqueous-as opposed to vitreous-were used to sample the intraocular complement environment. Here, we analyze aqueous samples and assess whether a correlation exists between aqueous and vitreous complement levels.

Methods

We collected aqueous, vitreous, and plasma samples from patients with and without proliferative diabetic retinopathy (PDR) undergoing vitrectomy. We assessed correlation between complement levels in aqueous and vitreous samples after using a normalizing ratio to correct for vascular leakage. Spearman correlation coefficients were used to assess the correlation between complement levels in the aqueous and vitreous.

Results

Aqueous samples were obtained from 17 cases with PDR and 28 controls. In all patients, aqueous Ba, C3a, and albumin levels were strongly correlated with vitreous levels (Spearman correlation coefficient of 0.8 for Ba and C3a and 0.7 for albumin; all P values < 0.0001). In PDR eyes only, aqueous and vitreous C3a levels were significantly correlated (Spearman correlation coefficient 0.7; P = 0.002), whereas in control eyes, both Ba and C3a (Spearman correlation coefficients of 0.7; P < 0.0001) were significantly correlated.

Conclusions

A strong correlation exists between aqueous and vitreous complement levels in diabetic eye disease.

Translational Relevance

The results establish that accurate sampling of the intraocular complement can be done by analyzing aqueous specimens, allowing for the rapid and safe measurement of experimental complement targets and treatment response.

Association of metformin treatment with enhanced effect of anti-VEGF agents in diabetic macular edema patients

PURPOSE

To investigate the effect of metformin combined with anti-VEGF agents in patients with diabetic macular edema (DME).

METHODS

This study was a prospective, nonrandomized case-control study. Patients were included in with a diagnosis of DME who received anti-VEGF agents injection. Basic information, medical history, best-corrected visual acuity (BCVA), central macular thickness (CMT), the number of intravitreal injections, panretinal photocoagulation (PRP), and macular grid photocoagulation treatment during the 6-month follow-up, were recorded for each patient.

RESULTS

A total of 50 DME patients were collected (24 patients with a history of oral metformin ≥ 6 months and 26 patients who had not taken metformin). The BCVA and the CMT were significantly improved after anti-VEGF treatment in two groups (F1 = 19.35, F2 = 26.78; F1 = 65.45, F2 = 76.23; P < 0.05). The BCVA in the metformin group was better than that in non-metformin group at every point after treatment (F = 34.45, P < 0.05). The CMT in metformin group decreased much more than that in non-metformin group during the follow-up period (F = 87.05, P < 0.05). The injection numbers decreased in the metformin group compared with the non-metformin group (t = 5.14, P < 0.05). However, there was no difference in PRP and macular grid photocoagulation therapy between the two groups during the 6-month follow-up.

CONCLUSION

Metformin can enhance the therapeutic effect of anti-VEGF agents on DME patients to improve their visual acuity, improve the structure of the macular area, and reduce the number of intravitreal injections 90.

Do serum vitamin D levels correlate with Macular Edema or with Diabetic Retinopathy?

PURPOSE

To compare serum vitamin D (25(OH)D) levels according to the presence of diabetic macular edema (DME) in Diabetes Mellitus (DM) patients with different retinopathy conditions.

METHODS

The files of all DM patients presenting for examination at the ophthalmology clinic between October 2018 and March 2020 were retrospectively examined. Data was collected from the files and included a comprehensive ophthalmological examination, laboratory results from fasting blood tests, and the internal medicine outpatient clinic examination. Patients were divided into two groups according to the presence of DME, they were divided into three groups in terms of retinopathy and DME, and in terms of retinopathy severity and presence of DME, they were divided into five groups.

RESULT

Ninety one (51.1%) of the age-sex matched participants were female and 87 (48.9%) were male. There was a statistically significant difference in vitamin D levels between the group with DME and the group without DME (p ≤ 0.001). In the comparison made according to the presence of retinopathy and DME; a significant difference was found between the DME group and the group with retinopathy but no DME (p ≤ 0.001). When the severity of retinopathy and the presence of DME were evaluated, a significant difference was found between the proliferative diabetic retinopathy (PDR) group with DME and the PDR group without DME in terms of vitamin D levels (p = 0.004).

CONCLUSION

Our study shows that the presence of DME is associated with lower serum 25(OH)D levels.

VEGF-Trap Modulates Retinal Inflammation in the Murine Oxygen-Induced Retinopathy (OIR) Model

Anti-Vascular Endothelial Growth Factor (VEGF) agents are the first-line treatment for retinal neovascular diseases, which represent the most prevalent causes of acquired vision loss world-wide. VEGF-Trap (Aflibercept, AFL), a recombinant decoy receptor recognizing ligands of both VEGFR-1 and -2, was recently reported to be highly efficient in improving visual acuity and preserving retinal anatomy in individuals affected by diabetic macular edema. However, the precise molecular and cell biological mechanisms underlying the beneficial effects of this novel tool have yet to be elucidated. Using the mouse oxygen-induced retinopathy (OIR) model as a surrogate of retinopathies with sterile post-ischemic inflammation, such as late proliferative diabetic retinopathy (PDR), retinopathy of prematurity (ROP), and diabetic macular edema (DME), we provide evidence that AFL modulates inflammation in response to hypoxia by regulating the morphology of microglial cells, a parameter commonly used as a proxy for changes in their activation state. We show that AFL administration during the hypoxic period of OIR leads to an increased number of ramified Iba1⁺ microglial cells/macrophages while subsequently limiting the accumulation of these cells in particular retinal layers. Our results suggest that, beyond its well-documented beneficial effects on microvascular regeneration, AFL might exert important modulatory effects on post-ischemic retinal inflammation.

Inflammatory mediators in diabetic retinopathy: Deriving clinicopathological correlations for potential targeted therapy

The role of inflammation in diabetic retinopathy (DR) is well-established and dysregulation of a large number of inflammatory mediators is known. These include cytokines, chemokines, growth factors, mediators of proteogenesis, and pro-apoptotic molecules. This para-inflammation as a response is not directed to a particular pathogen or antigen but is rather directed toward the by-products of the diabetic milieu. The inflammatory mediators take part in cascades that result in cellular level responses like neurodegeneration, pericyte loss, leakage, capillary drop out, neovascularization, etc. There are multiple overlaps between the inflammatory pathways occurring within the diabetic retina due to a large number of mediators, their varied sources, and cross-interactions. This makes understanding the role of inflammation in clinical manifestations of DR difficult. Currently, mediator-based therapy for DR is being evaluated for interventions that target a specific step of the inflammatory cascade. We reviewed the role of inflammation in DR and derived a simplified clinicopathological correlation between the sources and stimuli of inflammation, the inflammatory mediators and pathways, and the clinical manifestations of DR. By doing so, we deliberate mediator-specific therapy for DR. The cross-interactions between inflammatory mediators and the molecular cycles influencing the inflammatory cascades are crucial challenges to such an approach. Future research should be directed to assess the feasibility of the pathology-based therapy for DR.

The role of concomitant immunosuppressants in impeding the progression of diabetic retinopathy: A pilot study

Purpose

Hallmark of Diabetic Retinopathy (DR) is blood-retinal barrier alteration. Vascular endothelial growth factor (VEGF) and inflammation are involved in the pathogenesis of DR. Anti-VEGFs and lasers are effective in treating DR but have numerous drawbacks, hence the need to develop alternative therapies that may delay the onset or progression of DR.

Methods

Fifteen patients were recruited in each group; the study group was on immunosuppressants for some other coexisting disease and the control group was not on them. Each subject underwent detailed history, ophthalmic examination, and glycosylated hemoglobin (HbA1c) and renal function tests at the time of recruitment and the end of one year. Primary outcome measure was to compare the progression of DR in diabetics on immunosuppressant versus those not on it.

Results

Median age in the study and control group was 57 years and 60 years, respectively (P = 0.6). Median duration of diabetes was 11 and 12 years in the study and control group, respectively (P = 0.7). HbA1c for the study and control group for first visit was 7.6% and 8.0%, respectively (P = 0.26) and for second visit was 7.5% and 8.1%, respectively (P = 0.11). Hypertensives in the study and control groups were 9 and 4, respectively (P = 0.065); renal disease in the study and control groups was 4 and 2, respectively (P = 0.361). The control group showed 33.3% progression of DR, and no progression was seen in the study group (P = 0.014).

Conclusion

Immunosuppressants seemed to delay the onset and progression of DR in the earlier stages.

Targeting the Angiopoietin/Tie Pathway: Prospects for Treatment of Retinal and Respiratory Disorders

Anti-angiogenic approaches have significantly advanced the treatment of vascular-related pathologies. The ephemeral outcome and known side effects of the current vascular endothelial growth factor (VEGF)-based anti-angiogenic treatments have intensified research on other growth factors. The angiopoietin/Tie (Ang/Tie) family has an established role in vascular physiology and regulates angiogenesis, vascular permeability, and inflammatory responses. The Ang/Tie family consists of angiopoietins 1-4, their receptors, tie1 and 2 and the vascular endothelial-protein tyrosine phosphatase (VE-PTP). Modulation of Tie2 activation has provided a promising outcome in preclinical models and has led to clinical trials of Ang/Tie-targeting drug candidates for retinal disorders. Although less is known about the role of Ang/Tie in pulmonary disorders, several studies have revealed great potential of the Ang/Tie family members as drug targets for pulmonary vascular disorders as well. In this review, we summarize the functions of the Ang/Tie pathway in retinal and pulmonary vascular physiology and relevant disorders and highlight promising drug candidates targeting this pathway currently being or expected to be under clinical evaluation for retinal and pulmonary vascular disorders.

Hydrogen Sulfide Is a Novel Protector of the Retinal Glycocalyx and Endothelial Permeability Barrier

Significantly reduced levels of the anti-inflammatory gaseous transmitter hydrogen sulfide (H₂S) are observed in diabetic patients and correlate with microvascular dysfunction. H₂S may protect the microvasculature by preventing loss of the endothelial glycocalyx. We tested the hypothesis that H₂S could prevent or treat retinal microvascular endothelial dysfunction in diabetes. Bovine retinal endothelial cells (BRECs) were exposed to normal (NG, 5.5 mmol/L) or high glucose (HG, 25 mmol/L) ± the slow-release H₂S donor NaGYY4137 in vitro. Glycocalyx coverage (stained with WGA-FITC) and calcein-labeled monocyte adherence were measured. In vivo, fundus fluorescein angiography (FFA) was performed in normal and streptozotocin-induced (STZ) diabetic rats. Animals received intraocular injection of NaGYY4137 (1 μM) or the mitochondrial-targeted H₂S donor AP39 (100 nM) simultaneously with STZ (prevention) or on day 6 after STZ (treatment), and the ratio of interstitial to vascular fluorescence was used to estimate apparent permeability. NaGYY4137 prevented HG-induced loss of BREC glycocalyx, increased monocyte binding to BRECs (p ≤ 0.001), and increased overall glycocalyx coverage (p ≤ 0.001). In rats, the STZ-induced increase in apparent retinal vascular permeability (p ≤ 0.01) was significantly prevented by pre-treatment with NaGYY4137 and AP39 (p < 0.05) and stabilized by their post-STZ administration. NaGYY4137 also reduced the number of acellular capillaries (collagen IV + /IB4-) in the diabetic retina in both groups (p ≤ 0.05). We conclude that NaGYY4137 and AP39 protected the retinal glycocalyx and endothelial permeability barrier from diabetes-associated loss of integrity and reduced the progression of diabetic retinopathy (DR). Hydrogen sulfide donors that target the glycocalyx may therefore be a therapeutic candidate for DR.

Assessment of iris vasculature abnormalities in dogs with diabetes mellitus

OBJECTIVE

To identify and characterize abnormalities of iris vasculature in dogs with diabetes mellitus, compared to clinically normal, age-matched control dogs, by means of anterior segment angiography.

ANIMALS

10 dogs with naturally occurring diabetes mellitus and 10 age-matched control dogs with no ocular or systemic disease.

PROCEDURES

The day before iris vasculature abnormality (IVA) assessment, all dogs underwent complete physical and ophthalmic examinations and baseline clinicopathologic analyses. For diabetic dogs, serum fructosamine concentration and a 12-hour blood glucose concentration curve were generated. The next day, all dogs were sedated and anterior segment angiography (following IV injection of indocyanine green [1 mg/kg] and subsequently sodium fluorescein [20 mg/kg]) was performed with a full-spectrum camera and camera adapter system. Group findings were compared, and multiple linear regression analysis was performed to identify potential factor associations with IVAs.

RESULTS

During anterior segment angiography, the arterial, capillary, and venous phases were identified in all dogs. Times to onset of all phases in diabetic dogs were significantly less than those in control dogs. Vascular disruptions within the peripupillary region (evident following sodium fluorescein administration) were common in diabetic dogs. Severity of dye leakage into the iris stroma and aqueous humor was significantly greater in diabetic dogs than in control dogs. Duration of disease, mean blood glucose concentration, and serum fructosamine concentration were significantly associated with IVAs.

CONCLUSIONS AND CLINICAL RELEVANCE

In diabetic dogs, anterior segment angiography revealed IVAs that were not evident in control dogs. The severity of those changes appeared to be associated with disease duration and blood glucose regulation.

Review of the management of sight-threatening diabetic retinopathy during pregnancy

Diabetes mellitus (DM) is a noncommunicable disease reaching epidemic proportions around the world. It affects younger individuals, including women of childbearing age. Diabetes can cause diabetic retinopathy (DR), which is potentially sight threatening when severe nonproliferative DR (NPDR), proliferative DR (PDR), or sight-threatening diabetic macular oedema (STDME) develops. Pregnancy is an independent risk factor for the progression of DR. Baseline DR at the onset of pregnancy is an important indicator of progression, with up to 10% of women with baseline NPDR progressing to PDR. Progression to sight-threatening DR (STDR) during pregnancy causes distress to the patient and often necessitates ocular treatment, which may have a systemic effect. Management includes prepregnancy counselling and, when possible, conventional treatment prior to pregnancy. During pregnancy, closer follow-up is required for those with a long duration of DM, poor baseline control of blood sugar and blood pressure, and worse DR, as these are risk factors for progression to STDR. Conventional treatment with anti-vascular endothelial growth factor agents for STDME can potentially lead to foetal loss. Treatment with laser photocoagulation may be preferred, and surgery under general anaesthesia should be avoided. This review provides a management plan for STDR from the perspective of practising ophthalmologists. A review of strategies for maintaining the eyesight of diabetic women with STDR with emphasis on prepregnancy counselling and planning, monitoring and safe treatment during pregnancy, and management of complications is presented.

Role of interferons in diabetic retinopathy

Diabetic retinopathy (DR) is one of the major causes of visual impairment and irreversible blindness in developed regions. Aside from abnormal angiogenesis, inflammation is the most specific and might be the initiating factor of DR. As a key participant in inflammation, interferon-gamma (IFN-γ) can be detected in different parts of the eye and is responsible for the breakdown of the blood-retina barrier and activation of inflammatory cells and other cytokines, which accelerate neovascularization and neuroglial degeneration. In addition, IFN-γ is involved in other vascular complications of diabetes mellitus and angiogenesis-dependent diseases, such as diabetic nephropathy, cerebral microbleeds, and age-related macular degeneration. Traditional treatments, such as anti-vascular endothelial growth factor agents, vitrectomy, and laser photocoagulation therapy, are more effective for angiogenesis and not tolerable for every patient. Many ongoing clinical trials are exploring effective drugs that target inflammation. For instance, IFN-α acts against viruses and angiogenesis and is commonly used to treat malignant tumors. Moreover, IFN-α has been shown to contribute to alleviating the progression of DR and other ocular diseases. In this review, we emphasize the roles that IFNs play in the pathogenesis of DR and discuss potential clinical applications of IFNs in DR, such as diagnosis, prognosis, and therapeutic treatment.

COMPARISON OF INTRAVITREAL DEXAMETHASONE IMPLANT AND AFLIBERCEPT IN PATIENTS WITH TREATMENT-NAIVE DIABETIC MACULAR EDEMA WITH SEROUS RETINAL DETACHMENT

PURPOSE

To compare the efficacy and safety of intravitreal dexamethasone (DEX) implant versus aflibercept in patients with treatment-naive diabetic macular edema with inflammatory biomarkers.

METHODS

Ninety-eight eyes of 62 treatment-naive patients with diabetic macular edema with serous retinal detachment and hyperreflective foci were enrolled. Each patient was randomized to receive either aflibercept or DEX implant treatment. The treatment protocol included 3 monthly injections of 2 mg of aflibercept as a loading phase in the anti-vascular endothelial growth factor group and 0.7 mg of DEX implant in the DEX group and then pro re nata treatment. Primary outcome measures were mean changes in visual acuity and central retinal thickness at the end of the 12-month follow-up.

RESULTS

Forty-eight eyes of 29 patients were received DEX implant, and 50 eyes of 33 patients received the aflibercept injection. Mean central retinal thickness decreased from 615.2 µm at baseline to 297.7 µm at 12 months in the DEX group (P < 0.001) and from 576.5 µm to 367.4 µm in the aflibercept group (P < 0.001). Except for the first month, mean central retinal thickness reduction was significantly higher in the DEX group (P < 0.05, Mann-Whitney U Test). Visual acuity improved significantly at the end of the follow-ups (46.3-52.7 Early Treatment Diabetic Retinopathy Study letters in the DEX group and 47.5-56.8 Early Treatment Diabetic Retinopathy Study letters in the aflibercept group at 12 months, P < 0.001, paired-sample t-test). Adjusting by baseline values, the increase in mean visual acuity during the 12-month follow-ups favored the aflibercept group (P < 0.01), 25% of the DEX-treated eyes and 42% of the aflibercept treated eyes experienced 10 or more Early Treatment Diabetic Retinopathy Study letters visual gain (P: 0.058). The DEX group received significantly fewer (2.6 vs. 7.2) injections (P: 0.001).

CONCLUSION

It was observed that the both of DEX implant and aflibercept were effective and safe in treatment-naive diabetic macular edema patients with inflammatory phenotype. Anatomical results were found to be better in the DEX group, and functional results were found to be better in the aflibercept group. In pseudophakic eyes, the functional superiority of aflibercept ceased to exist, and the low number of injections in the DEX implant group was seen as an advantage.

Short-Term Outcomes of Refractory Diabetic Macular Edema Switch From Ranibizumab to Dexamethasone Implant and the Influential Factors: A Retrospective Real World Experience

Introduction: To evaluate the effectiveness and safety of intravitreal dexamethasone (DEX) implants in refractory diabetic macular edema (DME) treated by intravitreal ranibizumab.

Materials and Methods: We retrospectively analyzed DME patients who received DEX implant treatment after being refractory to at least 3 monthly intravitreal ranibizumab injections. The main outcomes were best-corrected visual acuity (BCVA), central retinal thickness (CRT), and intraocular pressure (IOP).

Results: Twenty-nine eyes of 26 patients who had previously received an average of 8.1 ± 4.4 ranibizumab injections were included. Patients received between one and three DEX implants during 12.4 ± 7.4 months of follow-up. The mean final CRT significantly decreased from 384.4 ± 114.4 μm at baseline to 323.9 ± 77.7 μm (p = 0.0249). The mean final BCVA was 51.4 ± 21.3 letters, which was not significant compared to baseline (44.9 ± 30.2 letters, p = 0.1149). Mean IOP did not increase significantly. All patients tolerated the treatment well without serious adverse events. Higher baseline CRT and worse BCVA correlated with better therapeutic responses.

Conclusion: Switching to DEX implant is feasible and safe for treating patients of DME refractory to intravitreal ranibizumab in real world. Further larger-scale or multicenter studies would be conducted to explore different DEX treatment strategies for DME, such as first-line or early switch therapy, for better BCVA improvement.

Outcome of Single Dexamethasone Implant Injection in the Treatment of Persistent Diabetic Macular Edema After Anti-VEGF Treatment: Real-Life Data from a Tertiary Hospital in Jordan

Purpose

To analyze the real-life clinical outcome of a single dexamethasone implant (DEX) injection in the treatment of persistent diabetic macular edema (DME) after anti-vascular endothelial growth factor (anti-VEGF) agents in a sample of the Jordanian population.

Methods

An observational case study design that involved a retrospective chart review analysis in a tertiary hospital in Amman, Jordan. Patients who showed persistent DME after receiving at least six doses of anti-VEGF agents for DME treatment were included.

Results

The study population consisted of 72 participants (29 females, 43 males) having an average age of 66 years. All patients had best-corrected visual acuity (BCVA) less than 0.7 (6/9) and SD-OCT documented center-involved DME. The study results showed that the average baseline BCVA improved from 0.205±0.1 before DEX injection to 0.358±0.1 at 3 months post-injection (p<0.0001). The central mean thickness (CMT) showed significant improvement also (539.347±132.402 to 379.041±99.430, p<0.0001). There was a mean of 3 mmHg increase in intraocular pressure at 3 months post-injection (p<0.0001), however, only 4% of patients required medical treatment. Other inflammatory biomarkers in OCT, such as intraretinal hyper-reflective dots (HRD), showed significant improvement also (23.67±16 to 14.83±13, p<0.0001). No other significant safety concerns were noticed.

Conclusion

A single DEX injection showed significant clinical and anatomical improvement in DME cases that are persistent after anti-VEGF treatment in our sample, with an excellent safety profile. In case of supply shortage of intravitreal injections, which occurs frequently at our center, a single DEX injection may be utilized as an effective DME therapy. Further research is mandated to identify clinical response in a larger sample and more frequent injections.

The Role of Inflammatory Cytokines in Neovascularization of Chemical Ocular Injury

Aim: Chemical injuries can potentially lead to the necrosis anterior segment of the eye, and cornea in particular. Inflammatory cytokines are the first factors produced after chemical ocular injuries. Inflammation via promoting the angiogenesis factor tries to implement the wound healing mechanism in the epithelial and stromal layer of the cornea. Methods: Narrative review.Results: In our review, we described the patterns of chemical injuries in the cornea and their molecular mechanisms associated with the expression of inflammatory cytokines. Moreover, the effects of inflammation signals on angiogenesis factors and CNV were explained. Conclusion: The contribution of inflammation and angiogenesis causes de novo formation of blood vessels that is known as the corneal neovascularization (CNV). The new vascularity interrupts cornea clarity and visual acuity. Inflammation also depleted the Limbal stem cells (LSCs) in the limbus causing the failure of normal corneal epithelial healing and conjunctivalization of the cornea.

Sodium-glucose co-transporter 2 inhibitors and diabetic retinopathy: insights into preservation of sight and looking beyond

Sodium-glucose co-transporter 2 Inhibitors (SGLT2i) were initially developed as therapeutic options for patients with type 2 diabetes mellitus (T2DM). Recently, randomized clinical trials have investigated their effects in cardiorenal protection through major adverse cardiovascular event reduction and reductions in diabetic nephropathy. While multiple mechanisms are proposed for this protection, microvascular protection is the primary component of their efficacy. While not primarily emphasized in clinical trials, evidence in other studies suggests that SGLT2i may confer retinoprotective effects via some of the same mechanisms in the aforementioned cardiorenal trials. Diabetic patients are susceptible to vision loss with chronic hyperglycemia promoting inflammation, edema, and retinal pathological changes. Targeting these pathways via SGLT2i may represent opportunities for providers to decrease retinopathy in high-risk T2DM patients, reduce disease progression, and lower drug burden in diabetic retinopathy patients. Further comprehensive clinical trials investigating these associations are needed to establish the potential retinoprotective effects of SGLT2i.

Association of plasminogen activator inhibitor-1 4G5G Polymorphism with risk of diabetic nephropathy and retinopathy: a systematic review and meta-analysis

Background

The 4G5G polymorphism of Plasminogen activator inhibitor-1 (PAI-1) gene is reported to be associated with diabetes nephropathy and retinopathy (DNR) risk. However, the findings are conflicting. Herein, we conducted a case-control and meta-analysis study to explore the association of PAI-1 4G5G polymorphism with risk of DNR.

Methods

We retrieved PubMed, EMBASE, Web of Knowledge, and CNKI databases and screened eligible studies up to August 15, 2020. The strength of associations was assessed by odd ratio (OR) and the corresponding 95% confidence interval (95% CI).

Results

A total of 27 case-control studies including 16 studies with 1,825 cases case and 1,731 controls on DN and eleven studies with 1,397 cases and 1,545 controls on DR were selected. Pooled data showed that the PAI-1 4G5G polymorphism was significantly associated with DN (allele model: OR = 0.674, 95% CI 0.524-0.865, p = 0.002; homozygote model: OR = 0.536, 95% CI 0.351-0.817, p = 0.004; heterozygote model: OR = 0.621, 95% CI 0.427-0.903, p = 0.013; dominant model: OR = 0.575, 95% CI 0.399-0.831, p = 0.003; and recessive model: OR = 0.711, 95% CI 0.515-0.981, p = 0.038) and DR (homozygote model: OR = 0.770, 95% CI 0.621-0.955, p = 0.0.017) risk. Stratified analyses by ethnicity indicated that PAI-1 4G5G polymorphism was associated with DN and DR risk in Asians and Caucasians, respectively.

Conclusions

The present meta-analysis revealed that the PAI-1 4G5G polymorphism was associated with increased risk of DN and DR risk. However, well-designed large-scale clinical studies are required to further validate our results.

Topical Interferon Alpha 2b in the Treatment of Refractory Diabetic Macular Edema

Purpose

To report the efficacy of topical interferon alpha 2b in the treatment of refractory diabetic macular edema.

Methods

In this retrospective interventional case series, five eyes of three individuals with diabetic macular edema resistant to multiple intravitreal injections of anti-vascular endothelial growth factor drugs and macular photocoagulation were included.

Results

All studied eyes had undergone multiple intravitreal injections including bevacizumab, combination of bevacizumab and triamcinolone and aflibercept, and macular laser photocoagulation before being included in this study. Two intravitreal ranibizumab injections had also been performed in both eyes of one patient. Two eyes had undergone pars plana vitrectomy, one for diabetic macular edema and the other for rhegmatogenous retinal detachment. After a discussion regarding the experimental topical interferon alpha 2b treatment, all patients agreed to start interferon alpha 2b drops four times a day. One month after the treatment, optical coherence tomography demonstrated a significant improvement in macular structure and thickness which was stable or improved at the three-month follow-up visit. Visual acuity in all eyes was stable or improved throughout the three-month follow-up period. Conjunctival injection and follicular conjunctivitis were the side effects of topical interferon alpha 2b and were treated with lubrication and steroids.

Conclusion

This case series demonstrated the potential efficacy of interferon alpha 2b in the treatment of refractory diabetic macular edema. It might be an option in patients with contraindications for intravitreal injections.

Differential reperfusion patterns in retinal vascular plexuses following increase in intraocular pressure an OCT angiography study

To describe patterns of reperfusion in the superficial vascular plexus (SVP), deep capillary plexus (DCP) and choriocapillaris (CC) as detected on optical coherence tomography (OCTA) in cynomogulus macaque monkey model following increase in intraocular pressure by an intravitreal injection. Animal imaging study. Two cynomogulus macaque monkeys. A 100 µL intravitreal injection (IVI) of saline was given in one eye of each monkey. Serial OCTA using a Zeiss Plex Elite 9000 was used to evaluate reperfusion patterns within the SCP, DCP, and CC. OCTA evidence of perfusion. Pulsation of the central retinal artery was detected after the intraocular pressure was elevated to 98 and ≥ 99 mmHg from IVI. Episodic flow within the SVP arterioles and venules and poor visualization of flow in capillaries was noted during the initial phase of elevated pressure. As the pressure declined, the flow signal within the DCP appeared initially as dots, which progressed laterally to loops which form capillary vortex configuration. Recovery of flow within the SVP and CC appeared sooner than in the DCP. At 40 min after the injection, well after the intraocular pressure normalized, the retinal and choriocapillaris vascular perfusion showed focal defects in every layer. Compared with pre-injection images, vessel density in the DCP was 68.8% and 78.6% of baseline in monkey 1 and monkey 2, respectively. In contrast vessel density in the SVP recovered to 84.2% and 88.9% of baseline. Increases in intraocular pressure from IVI have the potential to affect every layer of blood flow in the fundus. After nominal return of intraocular pressure, focal defects in flow persisted, which may result in longer term damage to the retina.

Aflibercept ameliorates retinal pericyte loss and restores perfusion in streptozotocin-induced diabetic mice

INTRODUCTION

Anti-vascular endothelial growth factor (VEGF) agents are used worldwide for advanced-stage diabetic retinopathy (DR). In contrast, apart from blood glucose control, there are no specific treatments that can limit the progression of early-stage DR that starts with pericyte loss and the destruction of the blood-retinal barrier. Here, we examined the efficacy of aflibercept, a potent anti-VEGF agent, against early-DR pathologies in a murine model of streptozotocin (STZ)-induced DR.

RESEARCH DESIGN AND METHODS

STZ was intraperitoneally administered in 8-week-old C57BL/6N male mice. After 4 weeks, the mice were divided into aflibercept-treated and saline-treated groups. Eight weeks after the STZ injection, vascular permeability/leakage was measured with fluorescein angiography in live mice. At 4, 6, and 8 weeks after the STZ injection, the eyes were enucleated, flat-mounted, and stained for platelet-derived growth factor receptor-β to assess pericyte abundance, CD45 to assess leukocyte recruitment, and fluorescein isothiocyanate dextran to assess perfusion. VEGF levels were quantified in each group. The effects of aflibercept on pericyte number, perfusion status, and leukocyte recruitment/accumulation on mice with diabetes retina were evaluated.

RESULTS

Our murine model successfully replicated the salient pathologies of DR such as pericytes loss, hyperpermeability, and perfusion blockage. Interestingly, numerous leukocytes and leukocyte clumps were found in diabetic retinal capillaries, especially in the non-perfused border area of the retina, suggesting a possible mechanism for non-perfusion and related pericyte damage. Treatment with aflibercept in mice with diabetes inhibited the upregulation of VEGF and the associated adhesion molecules while reducing the defects in perfusion. Aflibercept also attenuated pericyte loss in the diabetic retina.

CONCLUSION

VEGF inhibition through aflibercept treatment decreased leukocyte recruitment and aggregation, perfusion blockage, retinal hypoperfusion, and hyperpermeability in mice with diabetes and ultimately attenuated pericyte loss. Our findings suggest that anti-VEGF strategies may prove useful as possible therapies for limiting the progression of early-stage DR.

Effects of TNF-α-308G/A Polymorphism on the Risk of Diabetic Nephropathy and Diabetic Retinopathy: An Updated Meta-Analysis

Diabetic nephropathy (DN) and diabetic retinopathy (DR) are the major factors of morbidity and mortality in the patients with diabetes mellitus (DM). Growing studies have investigated the relationship between the TNF-α-308G/A polymorphism and the susceptibility to DN and DR, without achieving consensus. Thus, we conducted this meta-analysis to reach more comprehensive conclusions for these issues. Eligible studies were retrieved through electronic databases such as PubMed, Embase, Web of Science and China National Knowledge Infrastructure. Summary of odds ratios (OR) and 95% confidence intervals (CIs) were generated to evaluate the intensity of the associations. Statistical analyses were performed by STATA 11.0 and RevMan 5.2. There are fourteen eligible publications involving nineteen studies in this meta-analysis. TNF-α-308G/A polymorphism was significantly related to increasing risk of DN under recessive model (OR=1.37, 95% CI=1.03-1.83) and homozygous model (OR=1.54, 95% CI=1.15-2.06). Moreover, the similar results were also obtained in Asian groups for DN (recessive: OR=1.69, 95% CI=1.18-2.42; homozygous: OR=1.99, 95% CI=1.38-2.86; respectively), and significant association was also detected between TNF-α-308G/A and DN susceptibility in type 2 DM in recessive model (OR=1.39, 95% CI=1.02-1.89). No significant association was observed between TNF-α-308G/A and DR susceptibility in total analyses and subgroup analyses by ethnicity and type of DM. TNF-α-308G/A polymorphism may enhance the susceptibility to diabetic nephropathy, especially in Asian population and in T2DM patients, but not diabetic retinopathy.

Complement Activation in the Vitreous of Patients With Proliferative Diabetic Retinopathy

Purpose

A growing body of evidence points to complement dysregulation in diabetes. Early studies have indicated the presence of complement components inside the eye in patients with diabetic retinopathy, but these data have been confounded by leakage of proteins from the systemic circulation into the vitreous cavity.

Methods

We took samples of plasma and vitreous from patients with and without proliferative diabetic retinopathy (PDR) and measured levels of 16 complement components as well as albumin. We employed a normalized ratio using local and systemic complement and albumin levels to control for vascular leakage into the vitreous cavity.

Results

Before normalizing, we found significantly higher levels of 16 complement components we measured in PDR eyes compared to controls. After normalizing, levels of C4, factor B, and C5 were decreased compared to controls, while C3a and Ba levels were elevated compared to controls. We also found higher ratios of C3a/C3, C5a/C5, and Ba/factor B in PDR eyes compared to controls.

Conclusions

We found evidence of local, intraocular activation of C3, C5, and factor B. The normalized data suggest involvement of the alternative complement pathway. By showing activation of specific complement components in PDR, this study identifies targets for diagnostic and therapeutic potential.

Emerging corticosteroid delivery platforms for treatment of diabetic macular edema

INTRODUCTION

Diabetic macular edema (DME) is a leading cause of vision impairment. Low-grade inflammation is thought to play a critical role in its pathogenesis. Although vascular endothelial growth factor inhibitors are used first-line, not all eyes with DME respond optimally and may respond better to corticosteroids. Currently corticosteroids for DME are given intravitreally and require regular monitoring. There is an unmet need for longer lasting therapies and/or effective noninvasive therapies such as those given via oral or topical routes.

AREAS COVERED

This review discusses emerging corticosteroid delivery platforms for DME treatment. A literature search of investigational novel therapeutic steroid delivery platform in DME was conducted. Results are presented from preclinical, phase 1,2 & 3 clinical trials of various drug delivery systems using new technologies such as Solubilizing Nanoparticle technology, Mucus Penetrating Particles technology and Particle Replication In Non-wetting Templates. These new platforms aim to deliver corticosteroids effectively via topical, episcleral, subtenon, oral, and intravitreal routes.

EXPERT OPINION

These novel drug delivery platforms have the potential to lead to noninvasive or minimally invasive therapies and may overcome the shortcomings of current pharmacotherapy. However, larger comparative trials are needed for these agents to be added to the current armamentarium in DME management.

Serum myostatin levels are positively associated with diabetic retinopathy in individuals with type 2 diabetes mellitus

AIM

To examine the relationship between serum myostatin levels and diabetic retinopathy in individuals with type 2 diabetes mellitus (DM).

METHODS

This cross-sectional study evaluated 246 individuals with type 2 DM. Analysis of covariance was performed after adjusting for confounders. A logistic regression model was used to evaluate the relationship between serum myostatin levels and diabetic retinopathy.

RESULTS

Serum myostatin levels were significantly higher in individuals with diabetic retinopathy than in those without. After adjusting for other covariates, the mean serum myostatin levels were significantly different according to the severity of retinopathy (without diabetic retinopathy, 2234 pg/mL; non-proliferative diabetic retinopathy, 2698 pg/mL; and proliferative diabetic retinopathy, 3076 pg/mL; p for trend = 0.004). The multivariate analysis showed that serum myostatin levels were significantly associated with diabetic retinopathy (odds ratio for every 1 standard deviation-increase in logarithmic value, 1.77; 95% confidence interval: 1.21-2.59; p = 0.003).

CONCLUSION

Serum myostatin levels were positively associated with diabetic retinopathy in individuals with type 2 DM.

Deletion of Thioredoxin-Interacting Protein (TXNIP) Abrogates High Fat Diet-induced Retinal Leukostasis, Barrier Dysfunction and Microvascular Degeneration in a Mouse Obesity Model

We have shown that a high fat diet (HFD) induces the activation of retinal NOD-like receptor protein (NLRP3)-inflammasome that is associated with enhanced expression and interaction with thioredoxin-interacting protein (TXNIP). Here, the specific contribution of TXNIP and the impact of HFD on retinal leukostasis, barrier dysfunction and microvascular degeneration were investigated. Wild-type (WT) and TXNIP knockout (TKO) mice were fed with normal diet or 60% HFD for 8–18 weeks. TXNIP was overexpressed or silenced in human retinal endothelial cells (REC). At 8 weeks, HFD significantly induced retinal leukostasis and breakdown of the blood–retina barrier in WT mice, but not in TKO mice. In parallel, HFD also induced retinal expression of adhesion molecules and cleaved IL-1β in WT mice, which were also abrogated in TKO mice. In culture, TXNIP overexpression induced NLRP3, IL-1β, and adhesion molecules expression, while TXNIP silencing inhibited them. Blocking the IL-1β receptor significantly suppressed TXNIP-induced expression of NLRP3-inflammasome and adhesion molecules in HREC. Ex-vivo assay showed that leukocytes isolated from WT-HFD, but not from TKO-HFD, induced leukostasis and cell death. At 18 weeks, HFD triggered development of degenerated (acellular) capillaries and decreased branching density in WT but not in TKO mice. Together, HFD-induced obesity triggered early retinal leukostasis and microvascular dysfunction at least in part via TXNIP-NLRP3-inflammasome activation.

Neuroinflammation and oxidative stress act in concert to promote neurodegeneration in the diabetic retina and optic nerve: galectin-3 participation

Diabetes is a lifelong disease characterized by glucose metabolic imbalance, in which low insulin levels or impaired insulin signaling lead to hyperglycemic state. Within 20 years of diabetes progression, 95% of patients will have diabetic retinopathy, the leading cause of visual defects in working-age people worldwide. Although diabetes is considered a microvascular disease, recent studies have shown that neurodegeneration precedes vascular changes within the diabetic visual system, albeit its mechanisms are still under investigation. Neuroinflammation and oxidative stress are intrinsically related phenomena, since macrophage/microglia and astrocytes are the main sources of reactive oxygen species during central nervous system chronic degenerative diseases, and both pathological processes are increased in the visual system during diabetes. The present review will focus on recent findings of the contribution of oxidative stress derived from neuroinflammation in the early neurodegenerative aspects of the diabetic visual system and their relationship with galectin-3.

A cross-sectional study of vitreous and serum high mobility group box-1 levels in proliferative diabetic retinopathy

PURPOSE

We determined vitreous and serum levels of high mobility group box-1 (HMGB-1) in patients with proliferative diabetic retinopathy (PDR) and elucidate their relationship with receptor for advanced glycation end products (RAGE), vascular endothelial growth factor (VEGF) and interleukin-1β (IL-1β).

METHODS

In this cross-sectional study, patients with PDR who underwent vitrectomy were enrolled, and the control group included non-diabetic eyes. Vitreous and serum samples were analysed for HMGB-1, RAGE, VEGF and IL-1β by ELISA. We investigated the correlation between serum and vitreous levels of each cytokine, and we analysed the influence of intravitreal anti-VEGF treatment prior to vitrectomy on the cytokine levels in PDR.

RESULTS

Of 78 eyes of 78 patients enrolled consecutively, there were 32 PDR eyes and 46 control eyes. The serum levels were higher in diabetic than in non-diabetic subjects for HMGB-1, RAGE, VEGF and IL-1β (all p < 0.001), respectively. Similarly, the vitreous levels were higher in diabetic than in non-diabetic subjects for HMGB-1 (p < 0.001), RAGE (p = 0.001), VEGF (p < 0.001) and IL-1β (p < 0.001), respectively. We found a positive correlation between serum and vitreous levels of HMGB-1 in patient with PDR (p = 0.047, R = 0.353). There was a negative correlation between serum and vitreous levels of VEGF in patient with PDR (p = 0.001, R = -0.546). For the subgroup analysis, we detected that the vitreous levels of RAGE were significantly lower in patients who underwent anti-VEGF injection prior to vitrectomy than those who did not (p < 0.001).

CONCLUSIONS

Our findings suggest that HMGB-1 is involved in PDR disorders, and it may be a novel therapeutic target to inhibit progression of PDR.

Ursodeoxycholic Acid Attenuates the Retinal Vascular Abnormalities in Anti-PDGFR-β Antibody-Induced Pericyte Depletion Mouse Models

As a clinical manifestations of diabetic retinopathy (DR), pericytes (PCs) loss from the capillary walls is thought to be an initial pathological change responsible for the breakdown of the blood-retinal barrier (BRB). This study was performed to investigate the effects of ursodeoxycholic acid (UDCA) in PC depletion mice by injection of an antibody against platelet-derived growth factor reception-β (PDGFR-β clone APB5). To assess the integrity of the retinal vessels, their density, diameters, vessel branching points, and number of acellular capillaries were evaluated. While all types of retinal vessels became enlarged in APB5-induced mice, treatment with UDCA rescued the vasculature; the vessel density, diameter of the veins and capillaries, and vessel branching points were significantly lower in mice treated with UDCA. Although APB5-induced mice displayed progressive exacerbation of retinal edema, whole retinal thickness upon treatment with UDCA was significantly decreased. Additionally, UDCA reduced the expression of F4/80⁺ macrophages in the APB5-induced retina according to immunofluorescent labeling. UDCA also reduced the increased expression of angiogenic factors and inflammatory mediators (vascular endothelial growth factor, intercellular adhesion molecule-1, and monocyte chemotactic protein-1). These findings suggest that UDCA can be used to prevent the progression of and treat DR.

[Ozurdex in the treatment of diabetic macular edema. When to prescribe?]

Retinal damage in diabetes is known to manifest in two main ways: diabetic retinopathy and diabetic macular edema. The most effective anti-inflammatory drugs today are glucocorticoids, a classic representative of which is dexamethasone. Two things that should be considered by ophthalmologists in the therapy of macular edema are the switching point to dexamethasone implant when the effectiveness of anti-vasoproliferative drugs is unsatisfactory, and the identification of the main predictors of diabetic macular edema that make glucocorticoids the drugs of first choice. The data from real clinical practice was used to develop the indications for intravitreal administration of a glucocorticoid as the therapy of first choice for diabetic macular edema. Glucocorticoids are prescribed to patients diagnosed with diabetic macular edema who has a history of acute cerebrovascular events, myocardial infarction or other cardiovascular and cerebrovascular diseases, as well as patients with a very high risk of a vascular catastrophe. Intravitreal glucocorticoids can be prescribed to patients who cannot follow the schedule of frequent visits and/or are not able to visit the hospital during the first 6 months after the administration of the drug. Considering the local character of its ophthalmic action, the method can be recommended for treating patients with pseudophakic eyes, persistent diabetic macular edema, or patients who underwent vitrectomy.

Aqueous Humor Cytokine Levels and Anatomic Response to Intravitreal Ranibizumab in Diabetic Macular Edema

Importance

Variability in response to anti-vascular endothelial growth factor (VEGF) treatment in diabetic macular edema (DME) remains a significant clinical challenge. Biomarkers could help anticipate responses to anti-VEGF therapy.

Objectives

To investigate aqueous humor cytokine level changes in response to intravitreal ranibizumab therapy for the management of DME, and to determine the association between baseline aqueous levels and anatomic response.

Design, Setting, and Participants

In this prospective multicenter cohort study, 49 participants with diabetes mellitus complicated by center-involving DME, with a central subfield thickness of 310 μm or greater on spectral-domain optical coherence tomography (SD-OCT), were recruited from December 22, 2011, to June 13, 2013 and statistical analysis were performed from March 1, 2017, to June 1, 2017. A total of 48 participants proceeded to follow-up.

Interventions

Participants received monthly injections of ranibizumab, 0.5 mg, for 3 months. Aqueous fluid for cytokine analysis was obtained at baseline and repeated at the 2-month visit. Multiplex immunoassay was carried out in duplicate for VEGF, placental growth factor, transforming growth factor beta 2, intercellular adhesion molecule 1 (ICAM-1), interleukin 6 (IL-6), IL-8, IL-10, vascular intercellular adhesion molecule, and monocyte chemoattractant protein 1.

Main Outcomes and Measures

Baseline and 2-month change in aqueous cytokine levels, 3-month change in SD-OCT central subfield thickness and macular volume (MV), and the statistical association between baseline aqueous cytokine levels and these measures of anatomic response to ranibizumab in center-involving DME.

Results

Among the 48 participants, the mean (SD) age was 61.9 (7.1) years and 36 participants (75.0%) were men. The following cytokines were lower at month 2 vs baseline: ICAM-1 (median change, -190.88; interquartile range [IQR], -634.20 to -26.54; P < .001), VEGF (median change, -639.45; IQR, -1040.61 to -502.61; P < .001), placental growth factor (median change, -1.31; IQR, -5.99 to -0.01; P < .001), IL-6 (median change, -38.61; IQR, -166.72 to -2.80; P < .001), and monocyte chemoattractant protein 1 (median change, -90.13; IQR, -382.74 to 109.47; P = .01). When controlling for age, foveal avascular zone size, and severity of retinopathy, multiple linear regression determined that increasing baseline aqueous ICAM-1 was associated with a favorable anatomic response, in terms of reduced SD-OCT MV at 3 months (every additional 100 pg/mL of baseline ICAM-1 was associated with a reduction of 0.0379 mm3; P = .01). Conversely, increasing baseline aqueous VEGF was associated with a less favorable SD-OCT MV response at 3 months (every additional 100 pg/mL of baseline VEGF was associated with an increase of 0.0731 mm3; P = .02) and was associated with lower odds of being a central subfield thickness responder (odds ratio, 0.868; 95% CI, 0.755-0.998).

Conclusions and Relevance

Elevated aqueous ICAM-1 and reduced VEGF levels at baseline are associated with a favorable anatomic response to ranibizumab in DME, although there is not always direct correlation between anatomic and visual acuity response.

Serum and vitreous resistin levels in patıents with proliferative diabetic retinopathy

AIM

The aim of the study was to investigate the serum and vitreous levels of resistin in patients with the proliferative diabetic retinopathy (PDR) and to compare those with age-matched control subjects.

METHODS

The study included 45 eyes with PDR (group 1) and a control group of 22 (group 2). All eyes underwent vitrectomy surgery. The lipid profile, fasting blood glucose (FBG), HbA1c and resistin levels were investigated in blood samples of all subjects. Complete ophthalmological examinations were evaluated. Vitreous samples were collected from both groups during vitrectomy surgery and resistin levels were investigated in those samples. The results were evaluated using SPSS 9.0 software.

RESULTS

The demographic characteristics of the diabetic group and the control group were similar (p > 0.05). There was no significant difference between the groups in respect of mean visual acuity (VA), body mass index (BMI) values, or lipid profiles (p ˃ 0.05). There was no measurable value of resistin in the vitreous samples of all the eyes. The mean blood resistin level was 367 ng/ml in the control group and 387 ng/ml in the study group and the difference was not statistically significant (p > 0.05).

CONCLUSIONS

In the light of the findings of this study, it can be assumed that resistin did not pass through the vitreous at measurable levels. However, the serum resistin levels of the diabetic patients were higher than those of the control group although not statistically significant. Therefore, it can be considered that resistin does not play a major role in retinal neovascularization.