Diabetic macular edema, retinopathy and age-related macular degeneration as inflammatory conditions

Adjusting for Glycemic Control in Assessing the Relationship Between Age-Related Macular Degeneration and Diabetic Retinopathy

Purpose Studies regarding the relationship between age-related macular degeneration (AMD) and diabetic retinopathy (DR) conflict: while some support that AMD is protective against DR, others find the opposite. The mechanism by which AMD may protect against DR is unclear. We sought to assess the association between AMD and DR when controlling for glycemic control in patients with diabetes mellitus (DM) type II. Methods We identified 461 unique patients over 55 years old with a diagnosis of DM type II seen in our academic retina clinic in Stony Brook, New York between 12/31/2019 and 12/31/2020. Data were manually extracted and the population was split based on the presence of AMD diagnosis. Multivariate regression analyses were then performed comparing the prevalence of DR between groups while controlling for A1c. Secondary endpoints included demographic differences and smoking status.  Results Among the 461 patients, 118 (25.6%) had a diagnosis of AMD. Compared to patients without AMD, patients with AMD were older (69 vs. 66; OR 1.05; p=0.005) and less likely to have DR (37.3% vs. 59.2%; OR 0.35; p<0.001). There was no difference in average A1c between groups. Conclusion This is the first reported study assessing the relationship between AMD and DR while controlling for A1c. In our population, diagnosis of AMD was associated with significantly reduced odds of having DR. As AMD and DR appear to be related even after holding A1c constant, researchers should use caution when using DR as a surrogate for diabetic control in the context of AMD.

The association in diabetic retinopathy and stroke finding from NHANES evidence

PURPOSE

Diabetic retinopathy and stroke are both vascular pathologies, and this study intends to investigate the relationship between diabetic retinopathy and stroke.

METHODS

The NHANES database was used to find the relationship between diabetic retinopathy and stroke with 1948 individuals aged 40 years or older. The sensitivity of the data was verified by multiple interpolation, further analysis was done by subgroup analyses, and possible links were investigated with mediation studies.

RESULTS

Diabetes retinopathy was found to be closely associated with stroke, with the PDR group having a higher stroke incidence than the NPDR group. After controlling for covariates, there were still substantial differences in the risk of stroke among patients with NPDR and PDR. Overall, subgroup analysis revealed DR group showed an important distinction, compared to the non-DR (OR = 1.76, 95% CI 1.15-2.64). The results of the mediation research indicated that the connection between DR and stroke was mediated by the frailty index and hypertension.

CONCLUSION

This study demonstrated a statistically significant correlation between DR and stroke, which persisted even after DR staging and was more prevalent in PDR patients than in NPDR patients. Stroke prevention may benefit from DR health management.

Retinal Hydration Assessment With Optical Coherence Tomography: Unraveling Its Significance in Retinal Fluid Dynamics, Macular Edema and Cell Viability

PURPOSE

The purpose of this study was to quantify retinal hydration (RH) levels with optical coherence tomography (OCT) and determine the extent of cellular damage resulting from intraretinal fluid alterations.

METHODS

We took 6.0 mm sections of the human sensory retina that were excised from 18 fresh (<24 hours) donor eyes. They were either exposed to various osmotic stresses between 90 and 305 mOsm or dehydrated under a laminar flow hood. Change in tissue weight was used to calculate the retinal water content (RWC). Image analyses were conducted on OCT between 0 and 180 minutes to assess retinal thickness (RT) and "optically empty areas" (OEAs) representing intraretinal fluid. Correlations were sought among RWC, OEA, RWC, and RT. The effect of RH on retinal cell viability (RCV) was assessed with the Live-Dead Assay.

RESULTS

RH demonstrated a stronger correlation with the OEA than plain RT measurements (r = 0.99, P < 0.001). RH-RCV interaction fits well to a bell-shaped curve. A significant proportion of retinal cells (>80%) remained viable despite the change in RH ranging between 0.87 and 1.42 times. This "safe zone" was found to be associated with a 22% increase in OEA (r = 0.99, P < 0.01).

CONCLUSIONS

OCT has been demonstrated as a valuable tool for assessing RH and can be used for intraretinal fluid content analysis. RH is a better indicator of RCV compared with RT. Computing RH may improve the determination of functional outcome of intravitreal pharmacotherapeutics used for diabetic macular edema and exudative age-related macular degeneration.

TRANSLATIONAL RELEVANCE

We link basic research and clinical care by assessing retinal hydration's impact on retinal fluid dynamics, macular edema, and cell viability.

GABNet: global attention block for retinal OCT disease classification

Introduction

The retina represents a critical ocular structure. Of the various ophthalmic afflictions, retinal pathologies have garnered considerable scientific interest, owing to their elevated prevalence and propensity to induce blindness. Among clinical evaluation techniques employed in ophthalmology, optical coherence tomography (OCT) is the most commonly utilized, as it permits non-invasive, rapid acquisition of high-resolution, cross-sectional images of the retina. Timely detection and intervention can significantly abate the risk of blindness and effectively mitigate the national incidence rate of visual impairments.

Methods

This study introduces a novel, efficient global attention block (GAB) for feed forward convolutional neural networks (CNNs). The GAB generates an attention map along three dimensions (height, width, and channel) for any intermediate feature map, which it then uses to compute adaptive feature weights by multiplying it with the input feature map. This GAB is a versatile module that can seamlessly integrate with any CNN, significantly improving its classification performance. Based on the GAB, we propose a lightweight classification network model, GABNet, which we develop on a UCSD general retinal OCT dataset comprising 108,312 OCT images from 4686 patients, including choroidal neovascularization (CNV), diabetic macular edema (DME), drusen, and normal cases.

Results

Notably, our approach improves the classification accuracy by 3.7% over the EfficientNetV2B3 network model. We further employ gradient-weighted class activation mapping (Grad-CAM) to highlight regions of interest on retinal OCT images for each class, enabling doctors to easily interpret model predictions and improve their efficiency in evaluating relevant models.

Discussion

With the increasing use and application of OCT technology in the clinical diagnosis of retinal images, our approach offers an additional diagnostic tool to enhance the diagnostic efficiency of clinical OCT retinal images.

Prospective, Observational, Multicenter, Real-World Study of the Efficacy, Safety, and Pattern of Use of the Dexamethasone Intravitreal Implant in Diabetic Macular Edema in France: Short-Term Outcomes of LOUVRE 3

INTRODUCTION

To evaluate real-world efficacy, safety, and treatment patterns with the dexamethasone intravitreal implant (DEX) in diabetic macular edema (DME) in France.

METHODS

In this prospective, multicenter, observational, noncomparative, post-reimbursement study, consecutively enrolled patients with DME had a baseline evaluation on day 0. Those treated with DEX on day 0 were to be reevaluated at week 6 and months 6, 12, 18, and 24. DEX retreatment and/or alternative therapies were allowed during follow-up. The primary outcome measure was the maximum best corrected visual acuity (BCVA) gain from baseline during follow-up. Secondary outcome measures included time to maximum BCVA gain, patients (%) with prespecified BCVA gains from baseline at each visit, maximum central retinal thickness (CRT) reduction from baseline, patients (%) with CRT reduction ≥ 20% from baseline at each visit, patients (%) with DME resolution (per investigator judgement), and adverse events (AEs).

RESULTS

Of 112 patients/eyes with DME for 3.5 years (mean) at baseline, 80 (including 86.1% previously treated) received DEX on day 0 and were analyzed for efficacy. Early study termination precluded collection of ≥ 12-month efficacy data. Patients received 1.4 DEX injections over 8.3 months (averages). The maximum BCVA gain from baseline was 3.6 letters, reached after 77.2 days (averages); 24.6% (week 6) and 15.0% (month 6) of patients experienced ≥ 10-letter BCVA gains from baseline. The mean maximum CRT reduction from baseline was -146.4 µm; 61.4% (week 6) and 36.0% (month 6) of patients had CRT reductions ≥ 20% from baseline, and 68.1% reported DME resolution at least once during follow-up. Ocular hypertension (n = 8, 12.1%) was the most frequent treatment-related AE.

CONCLUSIONS

LOUVRE 3 confirmed that DEX improves BCVA and CRT, even in a patient population that had predominantly received DEX before enrollment in the study, and showed that DME resolution was observed during follow-up. DEX tolerability was consistent with published data, supporting treatment benefits in DME.

CLINICALTRIALS

GOV IDENTIFIER

NCT03003416.

Association between glycemic status and age-related macular degeneration: A nationwide population-based cohort study

AIM

The risk of dry and wet age-related macular degeneration (AMD) based on fasting glucose levels and disease duration of type 2 diabetes was investigated.

METHODS

Using a health insurance claims database and the results of health examinations in South Korea, we conducted a retrospective, population-based cohort study of 2,103,604 adults ≥ 45 years of age who were AMD-free based on health checkups in 2009 and observed from January 1, 2011, to December 31, 2018. Glycemic status was classified into five groups: normal, impaired fasting glucose, new-onset diabetes (fasting glucose level ≥ 126 mg/dl but no diabetes diagnosis or diabetes medication), diabetes diagnosis < 5 years, and diabetes ≥ 5 years. According to the presence and absence of choroidal neovascularization, AMD was classified as wet AMD and dry AMD, respectively. Adjusted hazard ratios (HRs) of AMD occurrence were estimated in each category.

RESULTS

For dry AMD (n = 36,271, 1.72%), the HR was 1.192 (1.141-1.245) among subjects with diabetes < 5 years and 1.294 (1.242-1.349) among subjects with diabetes ≥ 5 years compared with subjects with normal glycemic status after adjusting for age, sex, body mass index, lifestyle, and medical history. For wet AMD (n = 12,912, 0.61%), the HR was 1.103 (1.011-1.203) among subjects with new-onset diabetes, 1.252 (1.167-1.344) among subjects with diabetes < 5 years, and 1.506 (1.413-1.605) among subjects with diabetes ≥ 5 years. The HR of AMD was significantly increased among participants ≤ 65 years old and those who did not have hypertension.

CONCLUSIONS

The incidence of dry and wet AMD increased among diabetes patients compared to the normal glycemic status group. These risks increased when the duration of diabetes was 5 years or more. The risk of wet AMD was increased among new-onset diabetes patients. These results suggest that high blood glucose levels without treatment might induce the vision-threatening condition of wet AMD, emphasizing the importance of early blood glucose management.

Orally Delivered Connexin43 Hemichannel Blocker, Tonabersat, Inhibits Vascular Breakdown and Inflammasome Activation in a Mouse Model of Diabetic Retinopathy

Diabetic retinopathy (DR), a microvascular complication of diabetes, is associated with pronounced inflammation arising from the activation of a nucleotide-binding and oligomerization domain-like receptor (NLR) protein 3 (NLRP3) inflammasome. Cell culture models have shown that a connexin43 hemichannel blocker can prevent inflammasome activation in DR. The aim of this study was to evaluate the ocular safety and efficacy of tonabersat, an orally bioavailable connexin43 hemichannel blocker, to protect against DR signs in an inflammatory non-obese diabetic (NOD) DR mouse model. For retina safety studies, tonabersat was applied to retinal pigment epithelial (ARPE-19) cells or given orally to control NOD mice in the absence of any other stimuli. For efficacy studies, either tonabersat or a vehicle was given orally to the inflammatory NOD mouse model two hours before an intravitreal injection of pro-inflammatory cytokines, interleukin-1 beta, and tumour necrosis factor-alpha. Fundus and optical coherence tomography images were acquired at the baseline as well as at 2- and 7-day timepoints to assess microvascular abnormalities and sub-retinal fluid accumulation. Retinal inflammation and inflammasome activation were also assessed using immunohistochemistry. Tonabersat did not have any effect on ARPE-19 cells or control NOD mouse retinas in the absence of other stimuli. However, the tonabersat treatment in the inflammatory NOD mice significantly reduced macrovascular abnormalities, hyperreflective foci, sub-retinal fluid accumulation, vascular leak, inflammation, and inflammasome activation. These findings suggest that tonabersat may be a safe and effective treatment for DR.

Oral administration of CU06-1004 attenuates vascular permeability and stabilizes neovascularization in retinal vascular diseases

Retinal vascular diseases are the leading cause of blindness worldwide. These diseases have common disease mechanisms including vascular endothelial growth factor (VEGF) signaling, hypoxia, and inflammation. Treatment of these diseases with laser therapy, anti-VEGF injections and/or steroids has significantly improved clinical outcomes. However, these strategies do not address the underlying cause of the pathology and may have harmful side effects. Pathological processes that damage retinal vessels result in vascular occlusion and impairment of the barrier properties of retinal endothelial cells, leading to excessive vascular leakage. Therefore, a new therapeutic approach is needed for the treatment of retinal vascular disease. We were able to confirm that oral administration of CU06-1004, an endothelial dysfunction blocker, inhibited retinal vascular leakage induced by vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang2). Interestingly, oral administration of CU06-1004 prevented excessive vascular leakage in the diabetic retinopathy model. In addition, CU06-1004 inhibited angiogenesis and confirmed vascular stabilization in the oxygen-induced retinopathy model and laser-induced CNV model. Taken together, CU06-1004 could be a potential therapeutic agent for the treatment of retinal vascular diseases.

Extracellular Vesicles as Biomarkers and Therapeutics for Inflammatory Eye Diseases

Extracellular vesicles (EVs) are a group of cell-derived membrane vesicles of varying sizes that can be secreted by most cells. Depending on the type of cell they are derived from, EVs may contain a variety of cargo including proteins, lipids, miRNA, and DNA. Functionally, EVs play important roles in physiological and pathological processes through intercellular communication. While there has already been significant literature on the involvement of EVs in neurological and cardiovascular disease as well as cancer, recent evidence suggests that EVs may also play a role in mediating inflammatory eye diseases. This paper summarizes current advancements in ocular EV research as well as new ways by which EVs may be utilized as novel biomarkers of or therapeutics for inflammatory eye diseases.

Etiology of Macular Edema Defined by Deep Learning in Optical Coherence Tomography Scans

Purpose

To develop an automated method based on deep learning (DL) to classify macular edema (ME) from the evaluation of optical coherence tomography (OCT) scans.

Methods

A total of 4230 images were obtained from data repositories of patients attended in an ophthalmology clinic in Colombia and two free open-access databases. They were annotated with four biomarkers (BMs) as intraretinal fluid, subretinal fluid, hyperreflective foci/tissue, and drusen. Then the scans were labeled as control or ocular disease among diabetic macular edema (DME), neovascular age-related macular degeneration (nAMD), and retinal vein occlusion (RVO) by two expert ophthalmologists. Our method was developed by following four consecutive phases: segmentation of BMs, the combination of BMs, feature extraction with convolutional neural networks to achieve binary classification for each disease, and, finally, multiclass classification of diseases and control images.

Results

The accuracy of our model for nAMD was 97%, and for DME, RVO, and control were 94%, 93%, and 93%, respectively. Area under curve values were 0.99, 0.98, 0.96, and 0.97, respectively. The mean Cohen's kappa coefficient for the multiclass classification task was 0.84.

Conclusions

The proposed DL model may identify OCT scans as normal and ME. In addition, it may classify its cause among three major exudative retinal diseases with high accuracy and reliability.

Translational Relevance

Our DL approach can optimize the efficiency and timeliness of appropriate etiological diagnosis of ME, thus improving patient access and clinical decision making. It could be useful in places with a shortage of specialists and for readers that evaluate OCT scans remotely.

Nuclear Receptor Atlases of Choroidal Tissues Reveal Candidate Receptors Associated with Age-Related Macular Degeneration

The choroid is a vulnerable tissue site in the eye, impacted in several blinding diseases including age related macular degeneration (AMD), which is the leading cause of central vision loss in the aging population. Choroidal thinning and choriocapillary dropout are features of the early form of AMD, and endothelial dysfunction and vascular changes are primary characteristics of the neovascular clinical sub-type of AMD. Given the importance, the choroidal endothelium and outer vasculature play in supporting visual function, a better understanding of baseline choroidal signaling pathways engaged in tissue and cellular homeostasis is needed. Nuclear receptors are a large family of transcription factors responsible for maintaining various cellular processes during development, aging and disease. Herein we developed a comprehensive nuclear receptor atlas of human choroidal endothelial cells and freshly isolated choroidal tissue by examining the expression levels of all members of this transcription family using quantitative real time PCR. Given the close relationship between the choroid and retinal pigment epithelium (RPE), this data was cross-referenced with the expression profile of nuclear receptors in human RPE cells, to discover potential overlap versus cell-specific nuclear receptor expression. Finally, to identify candidate receptors that may participate in the pathobiology of AMD, we cataloged nuclear receptor expression in a murine model of wet AMD, from which we discovered a subset of nuclear receptors differentially regulated following neovascularization. Overall, these databases serve as useful resources establishing the influence of nuclear receptor signaling pathways on the outer vascular tissue of the eye, while providing a list of receptors, for more focused investigations in the future, to determine their suitability as potential therapeutic targets for diseases, in which the choroid is affected.

Thymoquinone in Ocular Neurodegeneration: Modulation of Pathological Mechanisms via Multiple Pathways

Thymoquinone is a naturally occurring compound and is the major component of Nigella sativa, also known as black seed or black cumin. For centuries thymoquinone has been used especially in the Middle East traditionally to treat wounds, asthma, allergies, fever, headache, cough, hypertension, and diabetes. Studies have suggested beneficial effects of thymoquinone to be attributed to its antioxidant, antibacterial, anti-oxidative stress, anti-inflammatory, and neuroprotective properties. Recently, there has been a surge of interest in thymoquinone as a treatment for neurodegeneration in the brain, such as that seen in Alzheimer’s (AD) and Parkinson’s diseases (PD). In vitro and in vivo studies on animal models of AD and PD suggest the main neuroprotective mechanisms are based on the anti-inflammatory and anti-oxidative properties of thymoquinone. Neurodegenerative conditions of the eye, such as Age-related Macular Degeneration (AMD) and glaucoma share at least in part similar mechanisms of neuronal cell death with those occurring in AD and PD. This review aims to summarize and critically analyze the evidence to date of the effects and potential neuroprotective actions of thymoquinone in the eye and ocular neurodegenerations.

Chitosan-Coated PLGA Nanoparticles Encapsulating Triamcinolone Acetonide as a Potential Candidate for Sustained Ocular Drug Delivery

The current treatment for the acquired retinal vasculopathies involves lifelong repeated intravitreal injections of either anti-vascular endothelial growth factor (VEGF) therapy or modulation of inflammation with steroids. Consequently, any treatment modification that decreases this treatment burden for patients and doctors alike would be a welcome intervention. To that end, this research aims to develop a topically applied nanoparticulate system encapsulating a corticosteroid for extended drug release. Poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) supports the controlled release of the encapsulated drug, while surface modification of these NPs with chitosan might prolong the mucoadhesion ability leading to improved bioavailability of the drug. Triamcinolone acetonide (TA)-loaded chitosan-coated PLGA NPs were fabricated using the oil-in-water emulsion technique. The optimized surface-modified NPs obtained using Box-Behnken response surface statistical design were reproducible with a particle diameter of 334 ± 67.95 to 386 ± 15.14 nm and PDI between 0.09 and 0.15. These NPs encapsulated 55-57% of TA and displayed a controlled release of the drug reaching a plateau in 27 h. Fourier-transform infrared spectroscopic (FTIR) analysis demonstrated characteristic peaks for chitosan (C-H, CONH2 and C-O at 2935, 1631 and 1087 cm-1, respectively) in chitosan-coated PLGA NPs. This result data, coupled with positive zeta potential values (ranged between +26 and +33 mV), suggests the successful coating of chitosan onto PLGA NPs. Upon coating of the NPs, the thermal stability of the drug, polymer, surfactant and PLGA NPs have been enhanced. The characteristics of the surface-modified NPs supports their use as potential candidates for topical ocular drug delivery for acquired retinal vasculopathies.

2-IPMA Ameliorates PM2.5-Induced Inflammation by Promoting Primary Ciliogenesis in RPE Cells

Primary cilia mediate the interactions between cells and external stresses. Thus, dysregulation of primary cilia is implicated in various ciliopathies, e.g., degeneration of the retina caused by dysregulation of the photoreceptor primary cilium. Particulate matter (PM) can cause epithelium injury and endothelial dysfunction by increasing oxidative stress and inflammatory responses. Previously, we showed that PM disrupts the formation of primary cilia in retinal pigment epithelium (RPE) cells. In the present study, we identified 2-isopropylmalic acid (2-IPMA) as a novel inducer of primary ciliogenesis from a metabolite library screening. Both ciliated cells and primary cilium length were increased in 2-IPMA-treated RPE cells. Notably, 2-IPMA strongly promoted primary ciliogenesis and restored PM2.5-induced dysgenesis of primary cilia in RPE cells. Both excessive reactive oxygen species (ROS) generation and activation of a stress kinase, JNK, by PM2.5 were reduced by 2-IPMA. Moreover, 2-IPMA inhibited proinflammatory cytokine production, i.e., IL-6 and TNF-α, induced by PM2.5 in RPE cells. Taken together, our data suggest that 2-IPMA ameliorates PM2.5-induced inflammation by promoting primary ciliogenesis in RPE cells.

Metformin, A Potential Role in Age-Related Macular Degeneration: A Systematic Review and Meta-Analysis

BACKGROUND

Currently, no generally approved medical treatment can delay the onset of age-related macular degeneration (AMD) or slow the progression of degenerative changes. Repurposing drugs with beneficial effects on AMD pathophysiology offers a route to new treatments which is faster, cost-effective, and safer for patients. Recent studies indicate a potential role for metformin in delaying AMD development and progression. In this context, we conducted a systematic review and meta-analysis to look for beneficial associations between metformin and AMD.

METHODS

We systematically searched Medline and Embase (via Ovid), Web of Science, and ClinicalTrials.gov databases for clinical studies in humans that examined the associations between metformin treatment and AMD published from inception to February 2021. We calculated pooled odds ratio (OR) with 95% confidence interval (CI) considering a random effect model in the meta-analysis.

RESULTS

Five retrospective studies met the inclusion criteria. There are no prospective studies that have reported the effect of metformin in AMD. The meta-analysis showed that people taking metformin were less likely to have AMD although statistical significance was not met (pooled adjusted OR = 0.80, 95% CI 0.54-1.05, I2 = 98.8%). Subgroup analysis of the association between metformin and early and late AMD could not be performed since the data was not available from the included studies.

CONCLUSIONS

Analysis of retrospective data suggests a signal that metformin may be associated with decreased risk of any AMD. It should be interpreted with caution because of the failure to meet statistical significance, the small number of studies, and the limitation of routine record data. However prospective studies are warranted in generalizable populations without diabetes, of varied ethnicities, and AMD stages. Clinical trials are needed to determine if metformin has efficacy in treating early and late-stage AMD.

EVALUATION OF THE EFFECT OF TOPICAL INTERFERON α2b AS A COMPLEMENTARY TREATMENT OF MACULAR EDEMA OF PATIENTS WITH DIABETIC RETINOPATHY: A Double-Blind Placebo-Controlled Randomized Clinical Trial Study

PURPOSE

The objective of this study is to evaluate the effect of the topical interferon α2b (IFNα2b) as an adjunctive therapy in the treatment of diabetic macular edema.

METHOD

This was a randomized controlled clinical trial performed on patients with diabetic macular edema. Fifty eyes of 50 patients (one eye/patient) who were receiving treatment for diabetic macular edema were randomly assigned to get topical IFNα2b 1 MU/mL or artificial tear eye drop as an adjunctive therapy. The primary measure outcomes were best-corrected visual acuity and central macular thickness; the secondary goals were to assess the effect of topical IFNα2b on the intraocular pressure and its potential side effects.

RESULTS

Baseline demographic data of the two groups were similar. The improvement in visual acuity of patients on IFN was more than the patients on artificial tear by the end of the fourth week (6.85 and 1.45 Early Treatment Diabetic Retinopathy Study letters, respectively, P = 0.001) and the eighth week (6.75 and 1.05 Early Treatment Diabetic Retinopathy Study letters, respectively, P = 0.005). The central macular thickness was also decreased correspondingly by the end of fourth week (53.1 ± 153 µm for patients on IFN and 26.6 ± 119.1 µm for patients on artificial tear, P = 0.497) and eighth week (27.9 ± 67.7 for patients on IFN and 29.2 ± 98 µm for patients on artificial tear, P = 0.957), but it was not statistically significant. Intraocular pressure was decreased on the fourth week in IFN group for 1.7 mmHg ±3 and increased for 0.1 mmHg ±2.3 in the artificial tear group (P = 0.018). No significant side effect was detected with topical IFN drop.

CONCLUSION

This study evaluated the short-term effects of topical IFNα2b 1 MU/mL. The drug was well tolerated and may have an effect on improvement of best-corrected visual acuity in patients with diabetic macular edema. It also had an intraocular pressure lowering effect on the studied eyes. However, further studies are needed to confirm this finding.

Ophthalmic Magnetic Resonance Imaging: Where Are We (Heading To)?

Magnetic resonance imaging of the eye and orbit (MReye) is a cross-domain research field, combining (bio)physics, (bio)engineering, physiology, data sciences and ophthalmology. A growing number of reports document technical innovations of MReye and promote their application in preclinical research and clinical science. Realizing the progress and promises, this review outlines current trends in MReye. Examples of MReye strategies and their clinical relevance are demonstrated. Frontier applications in ocular oncology, refractive surgery, ocular muscle disorders and orbital inflammation are presented and their implications for explorations into ophthalmic diseases are provided. Substantial progress in anatomically detailed, high-spatial resolution MReye of the eye, orbit and optic nerve is demonstrated. Recent developments in MReye of ocular tumors are explored, and its value for personalized eye models derived from machine learning in the treatment planning of uveal melanoma and evaluation of retinoblastoma is highlighted. The potential of MReye for monitoring drug distribution and for improving treatment management and the assessment of individual responses is discussed. To open a window into the eye and into (patho)physiological processes that in the past have been largely inaccessible, advances in MReye at ultrahigh magnetic field strengths are discussed. A concluding section ventures a glance beyond the horizon and explores future directions of MReye across multiple scales, including in vivo electrolyte mapping of sodium and other nuclei. This review underscores the need for the (bio)medical imaging and ophthalmic communities to expand efforts to find solutions to the remaining unsolved problems and technical obstacles of MReye, with the objective to transfer methodological advancements driven by MR physics into genuine clinical value.

Antioxidative activity of probiotics

Probiotics are defined as live microorganisms that have a beneficial effect on health by exhibiting quantitative and qualitative effects on intestinal microflora and/or modification of the immune system. A strain is considered probiotic if it demonstrates a series of clinically proven health benefits. In recent years, the number of studies related to the antioxidant properties of probiotics has significantly increased. Antioxidants are substances that inhibit the degree of oxidation of molecules and cause the transformation of radicals into inactive derivatives. The incorrect or inefficient antioxidant mechanisms results in oxidative stress and may occur in the course of many diseases such as diabetes, atherosclerosis, inflammatory bowel disease or damage to the heart, brain or transplanted organs. Correct functioning of antioxidant mechanisms seems to be crucial for the proper functioning of our body; therefore, probiotics should be carefully investigated for potential antioxidant properties.

THREE-YEAR OUTCOMES IN A RANDOMIZED SINGLE-BLIND CONTROLLED TRIAL OF INTRAVITREAL RANIBIZUMAB AND ORAL SUPPLEMENTATION WITH DOCOSAHEXAENOIC ACID AND ANTIOXIDANTS FOR DIABETIC MACULAR EDEMA

The decrease in macular thickness observed at 24 months was maintained at Month 36 in patients with diabetic macular edema treated with a combination of intravitreal ranibizumab and oral supplementation with high-dose docosahexaenoic acid and antioxidants.

Purpose:

To report 3-year results of a randomized single-blind controlled trial of intravitreal ranibizumab combined with oral docosahexaenoic acid (DHA) supplementation versus ranibizumab alone in patients with diabetic macular edema.

Methods:

There were 26 patients (31 eyes) in the DHA group and 29 (38 eyes) in the control group. Ranibizumab (0.5 mg) was administered monthly for the first 4 months followed by a pro re nata (PRN) regimen. In the experimental group, patients received oral DHA supplementation (1,050 mg/day) (Brudyretina 1.5 g).

Results:

At 36 months, mean decrease of central subfield macular thickness was higher in the DHA-supplementation group than in controls (275 ± 50 μm vs. 310 ± 97 μm) with significant differences at Months 25, 30, 33, and 34. Between-group differences in best-corrected visual acuity were not found, but the percentages of ETRDS gains >5 and >10 letters were higher in the DHA-supplementation group. Differences serum HbA1c, plasma total antioxidant capacity values, erythrocyte DHA content, and serum IL-6 levels were all significant in favor of the DHA-supplementation group.

Conclusion:

The addition of a high-rich DHA dietary supplement to intravitreal ranibizumab was effective to achieve better sustained improvement of central subfield macular thickness outcomes after 3 years of follow-up as compared with intravitreal ranibizumab alone.

Intravitreal hydrogels for sustained release of therapeutic proteins

This review highlights how hydrogel formulations can improve intravitreal protein delivery to the posterior segment of the eye in order to increase therapeutic outcome and patient compliance. Several therapeutic proteins have shown excellent clinical successes for the treatment of various intraocular diseases. However, drug delivery to the posterior segment of the eye faces significant challenges due to multiple physiological barriers preventing drugs from reaching the retina, among which intravitreal protein instability and rapid clearance from the site of injection. Hence, frequent injections are required to maintain therapeutic levels. Moreover, because the world population ages, the number of patients suffering from ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) is increasing and causing increased health care costs. Therefore, there is a growing need for suitable delivery systems able to tackle the current limitations in retinal protein delivery, which also may reduce costs. Hydrogels have shown to be promising delivery systems capable of sustaining release of therapeutic proteins and thus extending their local presence. Here, an extensive overview of preclinically developed intravitreal hydrogels is provided with attention to the rational design of clinically useful intravitreal systems. The currently used polymers, crosslinking mechanisms, in vitro/in vivo models and advancements are discussed together with the limitations and future perspective of these biomaterials.

Suppression of Ocular Vascular Inflammation through Peptide-Mediated Activation of Angiopoietin-Tie2 Signaling

Persistent inflammation is a complication associated with many ocular diseases. Changes in ocular vessels can amplify disease responses and contribute to vision loss by influencing the delivery of leukocytes to the eye, vascular leakage, and perfusion. Here, we report the anti-inflammatory activity for AXT107, a non-RGD, 20-mer αvβ3 and α5β1 integrin-binding peptide that blocks vascular endothelial growth factor (VEGF)-signaling and activates tyrosine kinase with immunoglobulin and EGF-like domains 2 (Tie2) using the normally inhibitory ligand angiopoietin 2 (Ang2). Tumor necrosis factor α (TNFα), a central inflammation mediator, induces Ang2 release from endothelial cells to enhance its stimulation of inflammation and vascular leakage. AXT107 resolves TNFα-induced vascular inflammation in endothelial cells by converting the endogenously released Ang2 into an agonist of Tie2 signaling, thereby disrupting both the synergism between TNFα and Ang2 while also preventing inhibitor of nuclear factor-κB α (IκBα) degradation directly through Tie2 signaling. This recovery of IκBα prevents nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) nuclear localization, thereby blocking NF-κB-induced inflammatory responses, including the production of VCAM-1 and ICAM-1, leukostasis, and vascular leakage in cell and mouse models. AXT107 also decreased the levels of pro-inflammatory TNF receptor 1 (TNFR1) without affecting levels of the more protective TNFR2. These data suggest that AXT107 may provide multiple benefits in the treatment of retinal/choroidal and other vascular diseases by suppressing inflammation and promoting vascular stabilization.

Benefits of micronutrient supplementation for reducing the risk of wet age-related macular disease and diabetic retinopathy

Age-related macular disease and diabetic retinopathy are chronic degenerative diseases characterised by progressive visual impairment. In Europe, age-related macular disease accounts for over 15% of blindness in adults over 50 years of age, and although the burden of diabetic retinopathy in terms of vision impairment is lower, vision loss associated with diabetic retinopathy is increasing with the rising prevalence of diabetes mellitus and the ageing of the population. Late-stage age-related macular disease can be subdivided into dry (non-neovascular) or wet (neovascular or exudative) forms. The large Age-Related Eye Disease Study 2 showed that supplementation with antioxidant nutrients reduces choroids neovascularisation and reduces the risk of progression of neovascular age-related macular disease. Antioxidant micronutrient supplements have also shown promising results in preventing the pathogenesis of retinopathy in animal models of diabetes. Age-related macular disease and diabetic retinopathy are understood to share some common pathophysiological characteristics, suggesting that micronutrients have an important role in ocular health in both conditions. This article will review the current evidence for the utility of micronutrients in preventing the development and progression of neovascular age-related macular disease and diabetic retinopathy.

Risuteganib-a novel integrin inhibitor for the treatment of non-exudative (dry) age-related macular degeneration and diabetic macular edema

INTRODUCTION

Non-exudative (dry) age-related macular degeneration (AMD) and diabetic macular edema (DME) are leading causes of vision loss worldwide. Besides age-related eye disease study (AREDS) vitamin supplements, there are no efficacious pharmaceutical interventions for dry AMD available. While numerous pharmacologics are available to treat diabetic macular edema (DME), many patients respond suboptimally to existing therapies. Risuteganib is a novel anti-integrin peptide that targets the multiple integrin heterodimers involved in the pathophysiology of dry AMD and DME. Inhibiting these selected integrin heterodimers may benefit patients with these conditions.

AREAS COVERED

This article offers a brief overview of current pharmaceuticals available for dry AMD and DME. The proposed role of integrins in AMD and DME is reviewed and later, risuteganib, a novel anti-integrin peptide is introduced. The data from initial Phase 1 and Phase 2 risuteganib clinical trials are discussed in the latter part of the paper.

EXPERT OPINION

While there are currently limited treatment options for dry AMD, more data are needed before we can truly evaluate the benefits of adopting risuteganib into the clinic. Conversely, several effective treatment options exist for DME; hence, risuteganib must show that it can add to these results, especially in those with refractory disease, before retina specialists adopt risuteganib into their treatment regimens.

Apigenin and Ethaverine Hydrochloride Enhance Retinal Vascular Barrier In Vitro and In Vivo

Purpose

This study aims to develop an impedance-based drug screening platform that will help identify drugs that can enhance the vascular barrier function by stabilizing vascular endothelial cell junctions.

Methods

Changes in permeability of cultured human retinal microvascular endothelial cells (HRMECs) monolayer were monitored in real-time with the xCELLigence RTCA system. Using this platform, we performed a primary screen of 2100 known drugs and confirmed hits using two additional secondary permeability assays: the transwell permeability assay and the XPerT assay. The cellular and molecular mechanisms of action and in vivo therapeutic efficacy were also assessed.

Results

Eleven compounds blocked interleukin 1 beta (IL-1β) induced hyperpermeability in the primary screen. Two of 11 compounds, apigenin and ethaverine hydrochloride, reproducibly blocked multiple cytokines induced hyperpermeability. In addition to HRMEC monolayers, the two compounds stabilized three other types of primary vascular endothelial cell monolayers. Preliminary mechanistic studies suggest that the two compounds stabilize the endothelium by blocking ADP-ribosylation factor 6 (ARF6) activation, which results in enhanced VE-cadherin membrane localization. The two compounds showed in vivo efficacy in an animal model of retinal permeability.

Conclusions

We developed an impedance-based cellular phenotypic drug screening platform that can identify drugs that enhance vascular barrier function. We found apigenin and ethaverine hydrochloride stabilize endothelial cell junctions and enhance the vascular barrier by blocking ARF6 activation and increasing VE-cadherin membrane localization.

Translational Relevance

The drugs identified from the phenotypic screen would have potential therapeutic efficacy in retinal vascular diseases regardless of the underlying mechanisms that promote vascular leak.

Age-Related Dysfunctions: Evidence and Relationship with Some Risk Factors and Protective Drugs

The theories interpreting senescence as a phenomenon favored by natural selection require the existence of specific, genetically determined and regulated mechanisms that cause a progressive age-related increase in mortality. The mechanisms defined in the subtelomere-telomere theory suggest that progressive slackening of cell turnover and decline in cellular functions are determined by the subtelomere-telomere-telomerase system, which causes a progressive "atrophic syndrome" in all organs and tissues. If the mechanisms underlying aging-related dysfunctions are similar and having the same origin, it could be hypothesized that equal interventions could produce similar effects. This article reviews the consequences of some factors (diabetes, obesity/dyslipidemia, hypertension, smoking, moderate use and abuse of alcohol) and classes of drugs [statins, angiotensin-converting enzyme (ACE) inhibitors, sartans] in accelerating and anticipating or in counteracting the process of aging. The evidence is compatible with the programmed aging paradigm and the mechanisms defined by the subtelomere-telomere theory but it has no obvious discriminating value against the theories of non-programmed aging paradigm. However, the existence of mechanisms, determined by the subtelomere-telomere-telomerase system and causing a progressive age-related decline in fitness through gradual cell senescence and cell senescence, is not justifiable without an evolutionary motivation. Their existence is expected by the programmed aging paradigm, while is incompatible with the opposite paradigm.

Quality of life of patients with central serous chorioretinopathy - a major cause of vision threat among middle-aged individuals

INTRODUCTION

The 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25) was designed to measure the vision-related quality of life (QoL). We aimed to assess the effect of disease duration, disease type (i.e., acute vs. chronic and unilateral vs. bilateral), and selected sociodemographic data on the QoL of patients with central serous chorioretinopathy (CSC).

MATERIAL AND METHODS

The study included 79 patients diagnosed with CSC. The QoL was assessed using the NEI VFQ-25. The statistical analysis was performed using IBM SPSS Statistics 24.

RESULTS

A significant positive correlation was found between deterioration in peripheral vision as assessed by the NEI VFQ-25 and duration of CSC (r = -0.22, p = 0.046). Compared with women, men obtained higher scores on the scales assessing general health, mental health, ocular pain and role limitations (p = 0.018, p = 0.027, p = 0.009 and p = 0.007, respectively). Patients with acute CSC reported higher levels of social functioning as compared with those with chronic CSC (p = 0.04). There were no differences in any of the scales between patients with unilateral and bilateral CSC. Elderly patients obtained lower scores on 9 of the 12 analyzed scales, as compared with younger patients (p < 0.05).

CONCLUSIONS

Patients with CSC do not assess their QoL in negative terms, which may be related to the fact that the disease presents with transient symptoms. However, the QoL deteriorated with longer disease duration. Men with CSC have better vision-related QoL than women.

Differentiation of Underlying Pathologies of Macular Edema Using Spectral Domain Optical Coherence Tomography (SD-OCT)

Purpose: To describe the morphological characteristics of macular edema (ME) of different origins using spectral domain optical coherence tomography (SD-OCT). Methods: This article summarizes and highlights key morphologic findings, based on published articles, describing the characteristic presentations of ME of different origins using SD-OCT. The following pathologies were included: uveitic macular edema, pseudophakic cystoid macular edema (PCME), diabetic macular edema (DME), macular edema secondary to central or branch retinal vein occlusion (CRVO/BRVO), microcystic macular edema (MME), ME associated with epiretinal membrane (ERM), and retinitis pigmentosa (RP). Conclusions: Macular edema of different origins show characteristic patterns that are often indicative of the underlying cause and pathology. Thus, trained algorithms may in the future be able to automatically differentiate underlying causes and support clinical diagnosis. Knowledge of different appearances support the clinical diagnosis and can lead to improved and more targeted treatment of ME.

Association between Metformin and a Lower Risk of Age-Related Macular Degeneration in Patients with Type 2 Diabetes

Purpose

This population-based, retrospective cohort study was to investigate whether metformin is associated with a lower risk of subsequent age-related macular degeneration (AMD) in patients with type 2 diabetes.

Methods

Using the Taiwan National Health Insurance Research Database from 2001 to 2013, 68205 subjects with type 2 diabetes were enrolled in the study cohort. Among them, 45524 were metformin users and 22681 were nonusers. The metformin and nonmetformin groups were followed until the end of 2013. Cox regression analyses were used to estimate hazard ratios (HRs) for AMD development associated with metformin use. Confounders included for adjustment were age, sex, and comorbidities (hypertension, hyperlipidemia, coronary artery disease, obesity, diabetic retinopathy, chronic kidney disease, and insulin treatment). Furthermore, propensity score (PS) matching method was used to choose the matched sample, and PS-adjusted Cox regression was performed. Finally, how HRs changed according to metformin treatment duration and dose was also evaluated in the metformin group.

Results

After adjusting for confounders, the metformin group had a significantly lower risk of AMD (adjusted HR = 0.54; 95% confidence interval [CI], 0.50–0.58). In the PS-matched sample, the significance remained (adjusted HR = 0.57; 95% CI, 0.52–0.63). In the metformin group, the adjusted HRs for the second (1.5–4 years) and third (≥4 years) tertiles of metformin treatment duration were 0.52 and 0.14, respectively, compared with the first tertile (<1.5 years). We also found significant trends of lower HRs (all p-value for trend <0.05) with increasing total and average doses.

Conclusions

Among patients with type 2 diabetes, those who use metformin are at a significantly lower risk of developing AMD relative to individuals who do not use metformin. Also, the trend of a significantly lower AMD risk was found with a higher dose of metformin.

Classification of diabetes-related retinal diseases using a deep learning approach in optical coherence tomography

BACKGROUND AND OBJECTIVES

Spectral Domain Optical Coherence Tomography (SD-OCT) is a volumetric imaging technique that allows measuring patterns between layers such as small amounts of fluid. Since 2012, automatic medical image analysis performance has steadily increased through the use of deep learning models that automatically learn relevant features for specific tasks, instead of designing visual features manually. Nevertheless, providing insights and interpretation of the predictions made by the model is still a challenge. This paper describes a deep learning model able to detect medically interpretable information in relevant images from a volume to classify diabetes-related retinal diseases.

METHODS

This article presents a new deep learning model, OCT-NET, which is a customized convolutional neural network for processing scans extracted from optical coherence tomography volumes. OCT-NET is applied to the classification of three conditions seen in SD-OCT volumes. Additionally, the proposed model includes a feedback stage that highlights the areas of the scans to support the interpretation of the results. This information is potentially useful for a medical specialist while assessing the prediction produced by the model.

RESULTS

The proposed model was tested on the public SERI-CUHK and A2A SD-OCT data sets containing healthy, diabetic retinopathy, diabetic macular edema and age-related macular degeneration. The experimental evaluation shows that the proposed method outperforms conventional convolutional deep learning models from the state of the art reported on the SERI+CUHK and A2A SD-OCT data sets with a precision of 93% and an area under the ROC curve (AUC) of 0.99 respectively.

CONCLUSIONS

The proposed method is able to classify the three studied retinal diseases with high accuracy. One advantage of the method is its ability to produce interpretable clinical information in the form of highlighting the regions of the image that most contribute to the classifier decision.

Role of ω3 polyunsaturated fatty acids in diabetic retinopathy: a morphological and metabolically cross talk among blood retina barriers damage, autoimmunity and chronic inflammation

Vision disorders are one of the most serious complications of diabetes mellitus (DM) affecting the quality of life of patients and eventually cause blindness. The ocular lesions in diabetes mellitus are located mainly in the blood vessels and retina layers. Different retina lesions could be grouped under the umbrella term of diabetic retinopathies (DMRP).

We propose that one of the main causes in the etiopathogenesis of the DMRP consists of a progressive loss of the selective permeability of blood retinal barriers (BRB). The loss of selective permeability of blood retinal barriers will cause a progressive autoimmune process. Prolonged autoimmune injures in the retinal territory will triggers and maintains a low-grade chronic inflammation process, microvascular alterations, glial proliferation and subsequent fibrosis and worse, progressive apoptosis of the photoreceptor neurons.

Patients with long-standing DM disturbances in retinal BRBs suffer of alterations in the enzymatic pathways of polyunsaturated fatty acids (PUFAs), increase release of free radicals and pro-inflammatory molecules and subsequently incremented levels of vascular endothelial growth factor. These facts can produce retinal edema and photoreceptor apoptosis.

Experimental, clinical and epidemiological evidences showing that adequate metabolic and alimentary controls and constant practices of healthy life may avoid, retard or make less severe the appearance of DMRP. Considering the high demand for PUFAs ω3 by photoreceptor complexes of the retina, it seems advisable to take fish oil supplements (2 g per day). The cellular, subcellular and molecular basis of the propositions exposed above is developed in this article.

Synthesizer drawings the most relevant findings of the ultrastructural pathology, as well as the main metabolic pathways of the PUFAs involved in balance and disbalanced conditions are provided.

Vitreous concentrations of vascular endothelial growth factor as a potential biomarker for postoperative complications following pars plana vitrectomy

INTRODUCTION

The aim of the study was to investigate the effects of vascular endothelial growth factor (VEGF) concentration in vitreous on postoperative complications after pars plana vitrectomy (PPV).

MATERIAL AND METHODS

Ninety subjects were surgically treated with PPV and followed up for 12 months at the Clinical Centre University Sarajevo, Clinic for Eye Disease. Exclusion criteria were presence of other eye diseases, systemic acute/chronic inflammatory conditions, or malignant neoplasms; previously performed PPV surgery; previously received intravitreal or systemic anti-VEGF therapy. A vitreous sample was obtained while performing the PPV procedure, using the Quantikine ELISA test to determine VEGF level, as a risk factor. Outcome measures were intraoperative and postoperative complications reported using categorical data: blunt and sharp dissection of membranes, intraoperative hemorrhage stopped by increasing infusion pressure, pressing with blunt instrument, or using diathermy. The following postoperative complications were assessed on the first day and at the 12-month follow-up visit: vitreous hemorrhage, fibrovascular proliferation (FVP), rubeosis iridis, and neovascular glaucoma (NVG).

RESULTS

Levels of vitreous VEGF at the time of PPV were significantly higher in eyes with: vitreous hemorrhage on the first day after PPV (p = 0.003); FVP on the first day and 12 months after PPV (p = 0.002 and p < 0.001, respectively); iris rubeosis on the first day and 12 months after PPV surgery (p < 0.001, and p = 0.001, respectively); NVG on the first day and 12 months after PPV surgery (p = 0.043 and p = 0.011, respectively), compared to the eyes without complications.

CONCLUSIONS

Preoperative levels of VEGF in vitreous can be a useful biomarker and predictor of the postoperative outcome in terms of intraoperative and postoperative complications.

Pleiotropic Effects of Risk Factors in Age-Related Macular Degeneration and Seemingly Unrelated Complex Diseases

Age-related macular degeneration (AMD) is a complex disease with both environmental and genetic factors influencing disease risk. Genome-wide case-control association studies, candidate gene analyses, and epidemiological studies reinforced the notion that AMD is predominantly a disease of an impaired complement system and an altered high-density lipoprotein (HDL) metabolism. Recent reports demonstrated the pleiotropic role of the complement system and HDL in complex diseases such as cardiovascular disease, autoimmune disorders, cancer, and Alzheimer's disease. In light of these findings, we explore current evidence for a shared genetic and environmental risk of AMD and unrelated complex diseases based on epidemiological studies. Shared risk factors may indicate common pathways in disease pathology and thus may have implications for novel treatment options of AMD pathology.

Efficacy of a Fatty Acids Dietary Supplement in a Polyethylene Glycol-Induced Mouse Model of Retinal Degeneration

Current knowledge of the benefits of nutrition supplements for eye pathologies is based largely on the use of appropriate animal models, together with defined dietary supplementation. Here, C57BL6 mice were subretinally injected with polyethylene glycol (PEG)-400, an established model of retinal degeneration with a dry age-related macular degeneration (AMD)-like phenotype, an eye pathology that lacks treatment. In response to PEG-400, markers of the complement system, angiogenesis, inflammation, gliosis, and macrophage infiltration were upregulated in both retinas and retinal pigment epithelium (RPE)/choroids, whereas dietary supplementation with a mixture based on fatty acids counteracted their upregulation. Major effects include a reduction of inflammation, in both retinas and RPE/choroids, and an inhibition of macrophage infiltration in the choroid, yet not in the retina, suggesting a targeted action through the choroidal vasculature. Histological analysis revealed a thinning of the outer nuclear layer (ONL), together with dysregulation of the epithelium layer in response to PEG-400. In addition, immunohistofluorescence demonstrated Müller cell gliosis and macrophage infiltration into subretinal tissues supporting the molecular findings. Reduced ONL thickness, gliosis, and macrophage infiltration were counteracted by the diet supplement. The present data suggest that fatty acids may represent a useful form of diet supplementation to prevent or limit the progression of dry AMD.

Cellular Reparative Mechanisms of Mesenchymal Stem Cells for Retinal Diseases

The use of multipotent mesenchymal stem cells (MSCs) has been reported as promising for the treatment of numerous degenerative disorders including the eye. In retinal degenerative diseases, MSCs exhibit the potential to regenerate into retinal neurons and retinal pigmented epithelial cells in both in vitro and in vivo studies. Delivery of MSCs was found to improve retinal morphology and function and delay retinal degeneration. In this review, we revisit the therapeutic role of MSCs in the diseased eye. Furthermore, we reveal the possible cellular mechanisms and identify the associated signaling pathways of MSCs in reversing the pathological conditions of various ocular disorders such as age-related macular degeneration (AMD), retinitis pigmentosa, diabetic retinopathy, and glaucoma. Current stem cell treatment can be dispensed as an independent cell treatment format or with the combination of other approaches. Hence, the improvement of the treatment strategy is largely subjected by our understanding of MSCs mechanism of action.

Retinal pigment epithelium-secretome: A diabetic retinopathy perspective

Diabetic retinopathy is a major complication of diabetes mellitus that can lead to retinal vascular abnormalities and visual impairment. While retinal endothelial pathology is well studied, retinal pigment epithelium (RPE) layer modifications and the patho-physiological regulations are not widely understood. The RPE is a highly specialized pigmented layer regulating not only physiological functions such as transport of nutrients, ions, absorption of light, phagocytosis of photoreceptor membranes, but also secretion of a number of cytokines, chemokines, angiogenic and anti-angiogenic factors. The RPE secretome, though crucial in health and disease, remains elusive in diabetic retinopathy. A knowledge of these secreted factors would help explain and correlate the clinical phase of the disease aiding in improved disease management. A comprehensive knowledge of the secreted factors of the RPE is a potential tool for understanding the differential treatment regime of early diabetic retinopathy, diabetic proliferative retinopathy and diabetic macular edema. In this review, we have delineated the importance of factors secreted by the retinal pigment epithelium and its regulation in the pathogenesis of diabetic retinopathy.