Assessment of biomarkers using multiplex assays in aqueous humor of patients with diabetic retinopathy

Multifunctional nano-in-micro delivery systems for targeted therapy in fundus neovascularization diseases

Fundus neovascularization diseases are a series of blinding eye diseases that seriously impair vision worldwide. Currently, the means of treating these diseases in clinical practice are continuously evolving and have rapidly revolutionized treatment opinions. However, key issues such as inadequate treatment effectiveness, high rates of recurrence, and poor patient compliance still need to be urgently addressed. Multifunctional nanomedicine can specifically respond to both endogenous and exogenous microenvironments, effectively deliver drugs to specific targets and participate in activities such as biological imaging and the detection of small molecules. Nano-in-micro (NIM) delivery systems such as metal, metal oxide and up-conversion nanoparticles (NPs), quantum dots, and carbon materials, have shown certain advantages in overcoming the presence of physiological barriers within the eyeball and are widely used in the treatment of ophthalmic diseases. Few studies, however, have evaluated the efficacy of NIM delivery systems in treating fundus neovascular diseases (FNDs). The present study describes the main clinical treatment strategies and the adverse events associated with the treatment of FNDs with NIM delivery systems and summarizes the anatomical obstacles that must be overcome. In this review, we wish to highlight the principle of intraocular microenvironment normalization, aiming to provide a more rational approach for designing new NIM delivery systems to treat specific FNDs.

Immune-Mediated Ocular Surface Disease in Diabetes Mellitus-Clinical Perspectives and Treatment: A Narrative Review

Diabetes mellitus (DM) is a chronic metabolic disorder marked by hyperglycemia due to defects in insulin secretion, action, or both, with a global prevalence that has tripled in recent decades. This condition poses significant public health challenges, affecting individuals, healthcare systems, and economies worldwide. Among its numerous complications, ocular surface disease (OSD) is a significant concern, yet understanding its pathophysiology, diagnosis, and management remains challenging. This review aims to explore the epidemiology, pathophysiology, clinical manifestations, diagnostic approaches, and management strategies of diabetes-related OSD. The ocular surface, including the cornea, conjunctiva, and associated structures, is vital for maintaining eye health, with the lacrimal functional unit (LFU) playing a crucial role in tear film regulation. In DM, changes in glycosaminoglycan metabolism, collagen synthesis, oxygen consumption, and LFU dysfunction contribute to ocular complications. Persistent hyperglycemia leads to the expression of cytokines, chemokines, and cell adhesion molecules, resulting in neuropathy, tear film abnormalities, and epithelial lesions. Recent advances in molecular research and therapeutic modalities, such as gene and stem cell therapies, show promise for managing diabetic ocular complications. Future research should focus on pathogenetically oriented therapies for diabetic neuropathy and keratopathy, transitioning from animal models to clinical trials to improve patient outcomes.

Chemokines in diabetic eye disease

BACKGROUND

Diabetic eye disease is a common micro-vascular complication of diabetes and a leading cause of decreased vision and blindness in people of working age worldwide.Although previous studies have shown that chemokines system may be a player in pathogenesis of diabetic eye disease, it is unclear which chemokines play the most important role.To date, there is no meta-analysis which has investigated the role of chemokines in diabetic eye disease.We hope this study will contribute to a better understanding of both the signaling pathways of the chemokines in the pathophysiological process, and more reliable therapeutic targets for diabetic eye disease.

METHODS

Embase, PubMed, Web of Science and Cochrane Library systematically searched for relevant studies from inception to Sep 1, 2023. A random-effect model was used and standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated to summarize the associated measure between chemokines concentrations and diabetic eye disease. Network meta-analysis to rank chemokines-effect values according to ranked probabilities.

RESULTS

A total of 33 different chemokines involving 11,465 subjects (6559 cases and 4906 controls) were included in the meta-analysis. Results of the meta-analysis showed that concentrations of CC and CXC chemokines in the diabetic eye disease patients were significantly higher than those in the controls. Moreover, network meta-analysis showed that the effect of CCL8, CCL2, CXCL8 and CXCL10 were ranked highest in terms of probabilities. Concentrations of CCL8, CCL2, CXCL8 and CXCL10 may be associated with diabetic eye disease, especially in diabetic retinopathy and diabetic macular edema.

CONCLUSION

Our study suggests that CCL2 and CXCL8 may play key roles in pathogenesis of diabetic eye disease. Future research should explore putative mechanisms underlying these links, with the commitment to develop novel prophylactic and therapeutic for diabetic eye disease.

Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

Modulation of CXCL10 activity as a therapeutic target of ocular toxoplasmosis in diabetic mice

Ocular toxoplasmosis is likely the most common cause of infectious posterior uveitis worldwide. CXCL10 chemokine has an important role in the maintenance of the T-cell response and the control of Toxoplasma gondii in the eye during chronic infection. Drugs that can modulate the chemokine activity could be effective against the parasite. In this work, CXCL10 local retinal expression was investigated in a diabetic mouse model with ocular toxoplasmosis for the first time. In addition, the efficacy of naphthoquinones and quinolones was compared to spiramycin (SP) in treating the infection and modulating the chemokine expression. Our results revealed that chloroquine (CQ) achieved the best results regarding the reduction of cerebral cyst burden (84.36%), improving the retinal histopathological changes, cellular infiltrates, and vasculitis significantly (P < 0.005), and balancing the strong CXCL10 expression caused by the infection. Buparvaquone-treated mice showed a significant percentage of reduction of brain cysts (76.25%), moderate improvement of histopathology, and mild to moderate CXCL10 expression. While SP showed the least efficacy against the parasite in the eye in the form of mild improvement of histopathological changes and downregulation of retinal chemokine expression with the least reduction rate of cerebral parasitic burden (57%). In conclusion, Optimal control of pathogens probably needs a balanced immune response with an optimum expression of chemokines. So, targeting the modulation of retinal CXCL10 may eventually be beneficial in the management of ocular toxoplasmosis plus its potential to act as a marker for predictive local immunological response during the infection.

Anterior chamber cytokine production and postoperative macular edema in patients with diabetes undergoing FLACS

PURPOSE

To evaluate the effect of femtosecond laser-assisted cataract surgery (FLACS) and manual cataract surgery (MCS) on proinflammatory cytokine expression in patients with diabetes vs nondiabetic patients.

SETTING

Outpatient surgical center in Vaughan, Ontario, Canada.

DESIGN

Prospective cohort study.

METHODS

Patients with diabetes and nondiabetic patients undergoing noncomplicated MCS or FLACS were assigned into 4 cohorts: MCS nondiabetic (n = 30), FLACS nondiabetic (n = 42), MCS diabetic (n = 40), and FLACS diabetic (n = 40). Aqueous humor inflammatory mediator concentrations were evaluated at MCS onset and after femtosecond laser treatment. The presence of cystoid macular edema, anterior chamber (AC) inflammation, central retinal thickness, macular volume, and retinal microvascular changes (through optical coherence tomography angiography) were evaluated preoperatively and on postoperative day 1, week 1, month 1 (POM1), and month 3 (POM3).

RESULTS

Patients with diabetes receiving FLACS had a higher concentration of interleukin (IL)-7, IL-13, and interferon-induced protein-10 than MCS diabetic patients; they also demonstrated higher levels of vascular endothelial growth factor and lower levels of interferon (IFN)-γ, granulocyte colony-stimulating factor, and IFN-α2 compared with MCS nondiabetic patients. Macular volume appeared to be significantly higher in MCS diabetic vs MCS non-diabetic patients at POM1 and between FLACS diabetic vs FLACS nondiabetic patients at POM3. There were no other significant differences between the cohorts for any parameter.

CONCLUSIONS

FLACS use in patients with diabetes demonstrated some differences in AC cytokine expression compared with non-diabetic FLACS or diabetic patients undergoing MCS; however, there was no increase in clinical inflammatory biomarkers. FLACS seems to be a safe technique to use in patients with diabetes.

Blockade of interleukin-6 trans-signaling prevents mitochondrial dysfunction and cellular senescence in retinal endothelial cells

Interleukin-6 (IL-6) is a multifaceted cytokine implicated in the pathogenesis of diabetic retinopathy (DR). Its activity extends through cis- and trans-signaling (TS) pathways, with cis-signaling limited to specific cell types possessing the membrane-bound IL-6 receptor, while trans-signaling broadly activates various cells without the membrane bound IL-6 receptor, including retinal endothelial cells. In this study, we determined the effects of interleukin-6 trans-signaling on mitochondrial dysfunction and cellular senescence in human retinal endothelial cells (HRECs). HRECs were cultured and treated with IL-6 + soluble IL-6R or Hyper IL-6 to activate trans-signaling, along with sgp130Fc for inhibition. RT-PCR was used to analyze gene expression changes associated with inflammation and senescence. Cellular senescence was assessed using SA β-gal staining. Mitochondrial function was evaluated using Seahorse XFe24 Bioanalyzer. IL-6 trans-signaling induced inflammatory gene expression as indicated by the upregulation of ICAM1, MCP1, and SERPINA3 levels. Additionally, it reduced mitochondrial respiration and oxidative phosphorylation, and these effects were counteracted by sgp130Fc. Moreover, IL-6 trans-signaling led to altered expression of apoptosis-associated genes, including downregulation of FIS1, BCL2, and MCL1, while promoting cellular senescence, a phenomenon mitigated by sgp130Fc. These results not only deepen our understanding of IL-6 in DR but also carry broader implications for age-related diseases and the aging process itself. This study underscores the potential therapeutic value of targeting IL-6 trans-signaling with sgp130Fc as a promising anti-inflammatory approach for DR and potentially other inflammatory conditions. Further in-vivo investigations are warranted to elucidate the function of IL-6 trans-signaling in aging-related pathologies and overall organismal health.

Study of aqueous humour inflammatory mediators' levels in a cohort of Egyptian patients with diabetic macular oedema

BACKGROUND

The aim was to study aqueous humour inflammatory mediators' levels in a cohort of Egyptian patients with diabetic macular oedema (DMO).

METHODS

This was a case-control prospective study conducted on 2 groups: 25 eyes of 22 (11 females) patients seeking treatment for DMO as patients group, and 10 eyes of 10 (4 females) cataract patients as a control group. Aqueous humour was aspirated before intravitreal injection (patients' group) or cataract surgery (control group). Inflammatory mediators in aqueous humour were measured using a multiplex bead immunoassay kit of 27 pre-mixed cytokines.

RESULTS

Eotaxin, interferon gamma-induced protein 10 (IP-10), monocyte chemoattractant protein-1 (MCP-1/CCL2) and interleukin-8 (IL-8/CXCL8) were found significantly higher in patients' group compared to control group (p = 0.043, 0.037, 0.001, 0.015 respectively). On the contrary, interferon-gamma (IFN-gamma) and granulocyte colony-stimulating factor (G-CSF) were found significantly higher in control group than patients' group (p = 0.003, 0.019 respectively). Basic fibroblast growth factor (Basic-FGF/FGF-2) and interleukin-1 receptor antagonist (IL-1ra) were found higher (but not statistically significant) in controls (p = 0.100 and 0.070 respectively). Additionally, a negative and significant correlation was found between Eotaxin level in aqueous humour and central macular thickness.

CONCLUSIONS

Some mediators might be implicated in the pathogenesis of DMO either augmenting or suppressing role. Eotaxin, IP-10, MCP-1 and IL-8 might have a role in cases not responding to standard anti-vascular endothelial growth factor (VEGF) therapy. IL-1ra might have a protective role; therefore, the effectiveness of intravitreal injection of IL-1ra homologue needs to be studied in future clinical trials.

Agonism of GPR120 Prevented High Glucose-Induced Apoptosis of Retinal Endothelial Cells through Inhibiting NLRP3 Inflammasome

PURPOSE

GPR120 has been reported to ameliorate inflammation in diabetes and diabetic complications. In this study, GW9508, the GPR120 agonist, was utilized in human retinal microvascular endothelial cells (HRMECs) exposed to high glucose (HG) to investigate the involvement of GPR120 in cellular viability and apoptosis as well as the association with the NLRP3 inflammasome.

METHODS

The expression of GPR120 in HRMECs cultured under HG was firstly detected by Western blotting. HRMECs were then assigned to the normal control, GW9508, HG, and HG + GW9508 groups. The expression of the NLRP3 inflammasome consists of NLRP3, ASC, and caspase-1 and was detected by Western blotting and the downstream IL-1β and IL-18 by ELISA. The cellular viability and apoptosis of HRMECs were detected by CCK-8 and flow cytometry, respectively. The expressions of apoptosis-related proteins Bax and Bcl-2 were detected by Western blotting. Finally, nonspecific siRNA (NS) or GPR120 siRNA (siGPR120) was transfected to the cells, followed by stimulation with or without GW9508 or HG, and the expression of NLRP3, ASC, and caspase-1 were detected by Western blotting in these groups.

RESULTS

GPR120 is expressed in HRMECs, and HG can reduce its expression in a time-dependent manner. GW9508 can attenuate inflammation by reducing the expression of NLRP3, ASC, caspase-1, IL-1β, and IL-18 under HG. GW9508 rescues the viability of HRMCs and reduces cell apoptosis by preventing an increase in Bax expression and the reduction in Bcl-2 expression. Additionally, knockdown of GPR120 by siRNA weakened the effects of GW9508 on NLRP3 inflammasome expression.

CONCLUSIONS

Activation of GPR120 protects retinal vascular endothelial cells from HG through inhibiting NLRP3 inflammasome. Thus, GPR120 might be a potential therapeutic target to reduce retinal endothelial damage in diabetic retinopathy.

Serum Cytokines and Growth Factors in Subjects with Type 1 Diabetes: Associations with Time in Ranges and Glucose Variability

The detrimental effect of hyperglycemia and glucose variability (GV) on target organs in diabetes can be implemented through a wide network of regulatory peptides. In this study, we assessed a broad panel of serum cytokines and growth factors in subjects with type 1 diabetes (T1D) and estimated associations between concentrations of these molecules with time in ranges (TIRs) and GV. One hundred and thirty subjects with T1D and twenty-seven individuals with normal glucose tolerance (control) were included. Serum levels of 44 cytokines and growth factors were measured using a multiplex bead array assay. TIRs and GV parameters were derived from continuous glucose monitoring. Subjects with T1D compared to control demonstrated an increase in concentrations of IL-1β, IL-1Ra, IL-2Rα, IL-3, IL-6, IL-7, IL-12 p40, IL-16, IL-17A, LIF, M-CSF, IFN-α2, IFN-γ, MCP-1, MCP-3, and TNF-α. Patients with TIR ≤ 70% had higher levels of IL-1α, IL-1β, IL-6, IL-12 p70, IL-16, LIF, M-CSF, MCP-1, MCP-3, RANTES, TNF-α, TNF-β, and b-NGF, and lower levels of IL-1α, IL-4, IL-10, GM-CSF, and MIF than those with TIR > 70%. Serum IL-1β, IL-10, IL-12 p70, MCP-1, MCP-3, RANTES, SCF, and TNF-α correlated with TIR and time above range. IL-1β, IL-8, IL-10, IL-12 p70, MCP-1, RANTES, MIF, and SDF-1α were related to at least one amplitude-dependent GV metric. In logistic regression models, IL-1β, IL-4, IL-10, IL-12 p70, GM-CSF, HGF, MCP-3, and TNF-α were associated with TIR ≤ 70%, and MIF and PDGF-BB demonstrated associations with coefficient of variation values ≥ 36%. These results provide further insight into the pathophysiological effects of hyperglycemia and GV in people with diabetes.

Variability of Replicates of Intraocular Inflammatory Biomarkers in Ocular Fluid Samples Analyzed with Multiplex Assays

Purpose

Certain factors such as instrumental and sample processing errors may contribute to variability of ocular biofluid samples when they are run as replicates with multiplex assays. There is a paucity of literature on the variability of replicates in multiplex assays. This study aims to evaluate whether there is significant variability in replicate analyses of multiplex assays.

Methods

A total of 152 human ocular biofluid samples (51 aqueous humor and 101 vitreous) were collected and assayed for 27 cytokine biomarker concentrations (pg/mL). Samples were evaluated as replicates (duplicate analysis) at four different time points. Statistical methods including paired samples t-test, 3-way ANOVA, intraclass correlation coefficient (ICC; <0.5-0.75=poor-moderate, 0.75->0.90 =good-excellent reliability), and coefficients of variation (CV) were employed to evaluate for statistical significance, with Bonferroni corrected P=0.002.

Results

Among the 4104 biomarker replicate assays for aqueous humor and vitreous, two analytes (PDGF-BB and IL-7) had a statistically significant difference between the sampled concentrations of the replicates in vitreous samples (mean (diff)=2.05, P<0.001, mean (diff)=1.56, P<0.001, respectively). Majority of the ICC values fell within the good-excellent range (86% of samples) with a minority falling in the poor-moderate range (14% of samples). More variability was noted in the vitreous humour, with five analytes (IL-2, IL-10, IL-12(p70), IL-13, IL-17) demonstrating an average ICC of less than 0.5. The CV calculated for each set of replicates suggested that 93% of replicates had an acceptable level of quantitative assay variability (CV<20%).

Conclusion

This study demonstrates that the analysis of most biomarkers in ocular fluids may not require the use of replicates. However, certain analytes such as PDGF-BB and IL-7 may require the use of replicates to ensure reliable results. Caution should be taken when applying these findings to other laboratory settings as our study was conducted by an experienced technician using a standardized protocol. In less standardized settings, replicates may be required in order to ensure accuracy of results. These findings may guide researchers with the design of their studies on ophthalmic biomarker analysis.

Clinical Characteristics of Patients with Intraocular Lens Calcification after Pars Plana Vitrectomy

AIM

To determine the clinical risk factors that may increase the occurrence of intraocular lens (IOL) calcification in patients who had undergone pars plana vitrectomy (PPV).

METHODS

The medical records of 14 patients who underwent IOL explantation due to clinically significant IOL opacification after PPV were reviewed. The date of primary cataract surgery, technique and implanted IOL characteristics; the time, cause and technique of PPV; tamponade used; additional surgeries; the time of IOL calcification and explantation; and IOL explantation technique were investigated.

RESULTS

PPV had been performed as a combined procedure with cataract surgery in eight eyes and solely in six pseudophakic eyes. The IOL material was hydrophilic in six eyes, hydrophilic with a hydrophobic surface in seven eyes and undetermined in one eye. The endotamponades used during primary PPV were C2F6 in eight eyes, C3F8 in one eye, air in two eyes and silicone oil in three eyes. Two of three eyes underwent subsequent silicone oil removal and gas tamponade exchange. Gas in the anterior chamber was detected in six eyes after PPV or silicone oil removal. The mean interval between PPV and IOL opacification was 20.5 ± 18.6 months. The mean BCVA in logMAR was 0.43 ± 0.42 after PPV, which significantly decreased to 0.67 ± 0.68 before IOL explantation for IOL opacification (p = 0.007) and increased to 0.48 ± 0.59 after the IOL exchange (p = 0.015).

CONCLUSIONS

PPV with endotamponades in pseudophakic eyes, particularly gas, seems to increase the risk for secondary IOL calcification, especially in hydrophilic IOLs. IOL exchange seems to solve this problem when clinically significant vision loss occurs.

Diabetic Retinopathy: Soluble and Imaging Ocular Biomarkers

Diabetic retinopathy (DR), the most common microvascular complication of diabetes mellitus, represents the leading cause of acquired blindness in the working-age population. Due to the potential absence of symptoms in the early stages of the disease, the identification of clinical biomarkers can have a crucial role in the early diagnosis of DR as well as for the detection of prognostic factors. In particular, imaging techniques are fundamental tools for screening, diagnosis, classification, monitoring, treatment planning and prognostic assessment in DR. In this context, the identification of ocular and systemic biomarkers is crucial to facilitate the risk stratification of diabetic patients; moreover, reliable biomarkers could provide prognostic information on disease progression as well as assist in predicting a patient's response to therapy. In this context, this review aimed to provide an updated and comprehensive overview of the soluble and anatomical biomarkers associated with DR.

Impact of obstructive sleep apnea on the expression of inflammatory mediators in diabetic macular edema

PURPOSE

To determine differences in inflammatory markers expressed in diabetic macular edema (DME) patients with and without obstructive sleep apnea (OSA).

METHODS

This was a prospective, cross-sectional study. Patients with treatment naive DME were enrolled in the study. They were stratified into 2 groups based on Apnea Hypopnea Index (AHI) from overnight polysomnography: OSA + (AHI ≥ 15) and OSA - (AHI<15). Multiplex immunoassay was performed for aqueous and serum cytokines including VEGF, placental growth factor (PGF), ICAM, IL2, IL3, IL6, IL8, IL10, IL17, vascular cell adhesion molecule-1 (VCAM1), monocyte attractant protein-1 (MCP1), epidermal growth factor (EGF) and platelet derived growth factor (PDGF). Statistical significance was defined as p < 0.004 using Bonferroni correction.

RESULTS

32 DME positive patients were enrolled in the study; of which 17 patients were OSA + and 15 OSA-. The OSA + cohort had significantly higher levels of serum EGF (p = 0.003), and trended towards higher levels of most serum cytokines including ICAM and IL6. OSA- cohort had significantly higher levels of aqueous IL17 compared to the OSA + cohort (2.97 ± 1.7 vs. 1.4 ± 0.46 pg/mL, p = 0.004). There were no significant differences in other aqueous cytokines.

CONCLUSIONS

OSA + group trended towards higher levels of most serum inflammatory markers, suggesting a greater pro-inflammatory state. However, they did not have significantly greater level of aqueous cytokines.

Small extracellular vesicle-loaded bevacizumab reduces the frequency of intravitreal injection required for diabetic retinopathy

Diabetic retinopathy (DR) is associated with retinal neovascularization, hard exudates, inflammation, oxidative stress and cell death, leading to vision loss. Anti-vascular endothelial growth factor (Anti-VEGF) therapy through repeated intravitreal injections is an established treatment for reducing VEGF levels in the retina for inhibiting neovascularization and leakage of hard exudates to prevent vision loss. Although anti-VEGF therapy has several clinical benefits, its monthly injection potentially causes devastating ocular complications, including trauma, intraocular hemorrhage, retinal detachment, endophthalmitis, etc. Methods: As mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (MSC-EVs) demonstrated safety in clinical studies, we have tested the efficacy of MSC-derived small EVs (MSC-sEVs) loaded anti-VEGF drug bevacizumab in a rat model of DR. Results: The study identified a clinically significant finding that sEV loaded with bevacizumab reduces the frequency of intravitreal injection required for treating diabetic retinopathy. The sustained effect is observed from the reduced levels of VEGF, exudates and leukostasis for more than two months following intravitreal injection of sEV loaded with bevacizumab, while bevacizumab alone could maintain reduced levels for about one month. Furthermore, retinal cell death was consistently lower in this period than only bevacizumab. Conclusion: This study provided significant evidence for the prolonged benefits of sEVs as a drug delivery system. Also, EV-mediated drug delivery systems could be considered for clinical application of retinal diseases as they maintain vitreous clarity in the light path due to their composition being similar to cells.

Exploring the angiographic-biologic phenotype in the IMAGINE study: quantitative UWFA and cytokine expression

BACKGROUND

This study investigates the association of intraocular cytokine expression and ultrawide-field fluorescein angiography (UWFA) quantitative imaging biomarkers and their association with angiographical feature response after antivascular endothelial growth factor (VEGF) therapy in diabetic macular oedema (DME).

METHODS

The IMAGINE DME study is a post hoc imaging biomarker and intraocular cytokine assessment from the DAVE study, a prospective DME clinical trial that included aqueous humour sampling and UWFA imaging. Fifty-four cytokines associated with inflammation and angiogenesis were evaluated through multiplex arrays. UWFA parameters were assessed using an automated feature analysis platform to determine ischaemic and leakage indices and microaneurysm (MA) count. Eyes were classified into UWFA responder or non-responder groups based on longitudinal quantitative UWFA parameter improvement. Cytokine expression was correlated with UWFA metrics and evaluated in the context of therapeutic response.

RESULTS

Twenty-one eyes were included with a mean age of 55±10 years. Increased panretinal leakage index correlated with VEGF (r=0.70, p=0.0005), angiopoietin-like 4 (r=0.77, p=4.6E-5) and interleukin (IL)-6 (r=0.64, p=0.002). Panretinal ischaemic index was associated with tissue inhibitor of metalloproteinases 1 (TIMP-1, r=0.49, p=0.03) and peripheral ischaemia correlated with VEGF (r=0.45, p=0.05). MA count correlated with increased monocyte chemotactic protein-4 (MCP-4, r=0.60, p=0.004) and platelet and endothelial cell adhesion molecule 1 (PECAM-1, r=0.58, p=0.005). Longitudinal MA reduction was associated with decreased baseline VEGF and urokinase receptor (uPAR) (p<0.05). High baseline VEGF and IL-6 were associated with dramatic reduction in macular leakage (p<0.05).

CONCLUSIONS

Baseline and longitudinal quantitative UWFA imaging parameters correlated with multiple aqueous humour cytokine concentrations, including VEGF and IL-6. Further research is needed to assess the possible implications of using these findings for evaluating treatment response.

Immunomodulation of MiRNA-223-based nanoplatform for targeted therapy in retinopathy of prematurity

Retinopathy of prematurity (ROP) is characterized by pathological angiogenesis and associated inflammation in the retina and is the leading cause of childhood blindness. MiRNA-223 (miR-223) drives microglial polarization toward the anti-inflammatory phenotype and offers a therapeutic approach to suppress inflammation and consequently pathological neovascularization. However, miRNA-based therapy is hindered by the low stability and non-specific cell-targeting ability of delivery systems. In the present study, we developed folic acid-chitosan (FA-CS)-modified mesoporous silica nanoparticles (PMSN) loaded with miR-223 to regulate retinal microglial polarization. The FA-CS/PMSN/miR-223 nanoparticles exhibited high stability and loading efficiency, achieved targeted delivery, and successfully escaped from lysosomes. In cultured microglial cells, treatment with FA-CS/PMSN/miR-223 nanoparticles upregulated the anti-inflammatory gene YM1/2 and IL-4RA, and downregulated the proinflammatory genes iNOS, IL-1β, and IL-6. Notably, in a mouse oxygen-induced retinopathy model of ROP, intravitreally injected FA-CS/PMSN/miR-223 nanoparticles (1 μg) decreased the retinal neovascular area by 52.6%. This protective effect was associated with the reduced and increased levels of pro-inflammatory (M1) and anti-inflammatory (M2) cytokines, respectively. Collectively, these findings demonstrate that FA-CS/PMSN/miR-223 nanoparticles provide an effective therapeutic strategy for the treatment of ROP by modulating the miR-223-mediated microglial polarization to the M2 phenotype.

Assessment of tear inflammatory cytokines concentration in patients with diabetes with varying severity of involvement

Diabetic retinopathy (DR), as one of the most important causes of blindness in Western societies, is a common micro-vasculopathy associated with diabetes. There is growing evidence of the role of inflammation in its development. This study was designed to measure cytokines in patients with diabetes with different stages of retinopathy .In this study, tear concentrations of three types of cytokines with different angiogenic properties including IL-1RA, IL-8, and TNF-α were measured in patients with diabetes without retinopathy, with non-proliferative retinopathy, with proliferative retinopathy, and in a healthy control group. The results showed that concentrations of TNF-α and IL-8 were higher in the tear sample of diabetics than in the control group and the concentrations of these cytokines were higher in patients with more advanced stages of diabetes, while the tear level of IL-1RA was significantly lower in diabetics. Based on these findings, it can be concluded that diabetes and its progression of severity affects the tear levels of IL-1RA, IL-8, and TNF-α inflammatory cytokines.

Aqueous Humor Cytokines in Non-Proliferative Diabetic Retinopathy

Background and Objectives: Cytokines are cell-signaling proteins whose identification may serve as inflammatory markers or early indicators for progressive disease. The aim of our study was to quantify several cytokines in aqueous humor (AH) and their correlations with biochemical parameters in diabetic eyes with non-proliferative diabetic retinopathy (NPDR). Materials and Methods: A total of 62 eyes from 62 patients were included in the study: 37 eyes from nondiabetic patients (group 1), 13 diabetic eyes with no retinopathy changes (group 2) and 12 diabetic eyes with early and moderate NPDR (group 3). AH samples were collected during uneventful cataract surgery. The cytokines IL-1β, IL-6, IL-8, IL-10, IL-12, IP-10, MCP-1, TNF-α and VEGF were quantified using multiplex bead-based immunoassay. Due to unreliable results, IL-1β, TNF-α, IL-10 and IL-12 were excluded. Concentrations were compared between groups. Biochemical parameters (fasting blood sugar, glycated hemoglobin, C-reactive protein) and the duration of diabetes were recorded. Results: VEGF levels were significantly different between groups (p = 0.001), while levels of IL-6, IL-8, IP-10 and MCP-1 were comparable across all groups (p > 0.05). IL-6 concentration correlated with VEGF in group 1 (rho = 0.651, p = 0.003) and group 3 (rho = 0.857, p = 0.007); no correlation could be proved between IL-6, IL-8, IP-10, MCP-1 or VEGF and biochemical parameters. Duration of diabetes was not correlated with the cytokine levels in groups 2 and 3. The receiver operating characteristic (ROC) curve revealed that VEGF concentrations could discriminate early and moderate NPDR from diabetes, with an area under the curve (AUC) of 0.897 (p = 0.001, 95% CI = 0.74−1.0). Conclusions: Diabetes mellitus induces significant intraocular changes in the VEGF expression in diabetic patients vs. normal subjects, even before proliferative complications appear. VEGF was increasingly expressed once the diabetes progressed from no retinopathy to early or moderate retinopathy.

The Diagnostic Value of Circulating VEGF in Diabetic Retinopathy in Asia: A Systematic Review and Meta-analysis

PURPOSE

Vascular endothelial growth factor (VEGF) has obvious clinical value in diabetes, but the conclusions on the diagnostic value of diabetic retinopathy (DR) are not consistent. This study aims to comprehensively evaluate the accuracy of circulating VEGF in the diagnosis of DR in the Asian population by a method of meta-analysis.

METHODS

PubMed, Cochrane Library, Embase, Web of Science, China National Knowledge Infrastructure (CNKI), and China Wanfang Databases were searched for relevant studies on the diagnostic value of VEGF for DR in Asia up to November 2021. The pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and areas under the curve (AUC) were calculated by Stata 15.0 software.

RESULTS

After screening, eight eligible studies were enrolled, including 547 patients with DR. The results of the meta-analysis showed that the pooled DOR, sensitivity, specificity, PLR, and NLR were 31.67 (95%CI: 13.55 ~ 74.05), 0.86 (95%CI: 0.74 ~ 0.93), 0.84 (95%CI: 0.80 ~ 0.87), 5.33 (95%CI: 4.09 ~ 6.93), 0.17 (95%CI: 0.09 ~ 0.32), respectively. The AUC was 0.86 (95%CI: 0.82 ~ 0.89).

CONCLUSION

Circulating VEGF has a good diagnostic value in DR in the Asian population, with the potential to be an early diagnostic marker for DR.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Lab-on-a-chip technologies for minimally invasive molecular sensing of diabetic retinopathy

Diabetic retinopathy (DR) is the most common diabetic eye disease and the worldwide leading cause of vision loss in working-age adults. It progresses from mild to severe non-proliferative or proliferative DR based on several pathological features including the magnitude of blood-retinal barrier breakdown and neovascularization. Available pharmacological and retinal laser photocoagulation interventions are mostly applied in the advanced stages of DR and are inefficient in halting disease progression in a significantly high percentage of patients. Yet, recent evidence has shown that some therapies could potentially limit DR progression if applied at early stages, highlighting the importance of early disease diagnostics. In the past few decades, different imaging modalities have proved their utility for examining retinal and optic nerve changes in patients with retinal diseases. However, imaging based-methodologies solely rely on morphological examination of the retinal vascularization and are not suitable for recurrent and personalized patient evaluation. This raises the need for new technologies to enable accurate and early diagnosis of DR. In this review, we critically discuss the potential clinical benefit of minimally-invasive molecular biomarker identification and profiling of diabetic patients who are at risk of developing DR. We provide a comparative overview of conventional and recently developed lab-on-a-chip technologies for quantitative assessment of potential DR molecular biomarkers and discuss their advantages, current limitations and challenges for future practical implementation and continuous patient monitoring at the point-of-care.

Perspectives on diabetic retinopathy from advanced retinal vascular imaging

Diabetic retinopathy (DR) is a microvascular complication of diabetes and the most common cause of acquired vision loss in adults worldwide. DR is associated with long-term chronic hyperglycaemia and its detrimental effects on the neurovascular structure and function of the retina. Direct imaging of the retinal vasculature and staging of DR has been traditionally based on fundoscopy and fluorescein angiography, which provide only 2D views of the retina, and in the case of fluorescein angiography, requires an invasive dye injection. In contrast, advanced retinal imaging modalities like optical coherence tomography angiography (OCTA) and adaptive optics (AO) are non-invasive and provide depth-resolved, 3D visualization of retinal vessel structure as well as blood flow. Recent studies utilizing these imaging techniques have shown promise in evaluating quantitative vascular parameters that correlate tightly to clinical DR staging, elucidating functional changes in early diabetes, and monitoring DR treatment response. In this article, we discuss and synthesize the results of advanced retinal imaging studies in DR and their implications for our clinical and pathophysiologic understanding of the disease. Based on the recent literature, we also propose a model to describe the differential changes in vascular structure and flow that have been described on advanced retinal imaging as DR progresses. Future studies of these imaging modalities in larger and more diverse populations, as well as corroboration with histological and functional studies, will be important to further our understanding of DR.

Reduction of choroidal neovascularization via cleavable VEGF antibodies conjugated to exosomes derived from regulatory T cells

Choroidal neovascularization induced by age-related macular degeneration and retinal neovascularization induced by diabetic retinopathy-two leading causes of blindness-are often treated using antibodies targeting vascular endothelial growth factor (VEGF). Here we report a strong association between inflammation and high VEGF expression in aqueous humour samples from patients with choroidal or retinal neovascularization, and show that intravitreally injected exosomes derived from regulatory T cells and conjugated with an anti-VEGF antibody via a peptide linker that is cleavable by matrix metalloproteinases markedly suppressed ocular neovascularization in mouse and non-human primate models of choroidal neovascularization. The engineered exosomes, which selectively accumulate in the neovascularization lesions, could be adapted for other combination therapies of therapeutic antibodies and anti-inflammatory cargo.

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.

Intraocular fluid biomarkers (liquid biopsy) in human diabetic retinopathy

Purpose

This article aims to review the impact of detecting and quantifying intraocular biomarkers (liquid biopsy) in both aqueous and vitreous humor in eyes of people affected by diabetes mellitus.

Methods

This is a detailed review about aqueous and/or vitreous humor sampling in human diabetic eyes for proteomic and/or metabolomic analysis contributing to the understanding of the pathophysiology and treatment effects of diabetic retinopathy.

Results

Aqueous and vitreous humor molecular biomarkers proved to be directly correlated to each other and valuable to study retinal conditions. Moreover, proteomic and metabolomic analysis showed that the biomarkers of neuroinflammation, neurodegeneration, and vasculopathy are detectable in intraocular fluids and that their concentration changes in different stages of disease, and in response to treatment of all diabetic retinopathy aspects, mainly diabetic macular edema and proliferative retinopathy.

Conclusions

Liquid biopsy offers the possibility to improve our knowledge of intraocular eye disease induced by diabetes mellitus. The exact quantification of intraocular biomarkers contributes to the precision medicine approach even in the diabetic retinopathy scenario. The diffusion of this approach should be encouraged to have quantifiable information directly from the human model, which may be coupled with imaging data.

Chemokines in Prediabetes and Type 2 Diabetes: A Meta-Analysis

Background

A growing number of studies found inconsistent results on the role of chemokines in the progression of type 2 diabetes (T2DM) and prediabetes (PDM). The purpose of this meta-analysis was to summarize the results of previous studies on the association between the chemokines system and T2DM/PDM.

Methods

We searched in the databases, PubMed, Web of Science, Embase and Cochrane Library, for eligible studies published not later than March 1, 2020. Data extraction was performed independently by 2 reviewers, on a standardized, prepiloted form. Group differences in chemokines concentrations were summarized using the standardized mean difference (SMD) with a 95% confidence interval (CI), calculated by performing a meta-analysis using the random-effects model.

Results

We identified 98 relevant studies that investigated the association between 32 different chemokines and T2DM/PDM. Altogether, these studies involved 14,708 patients and 14,574 controls. Results showed that the concentrations of CCL1, CCL2, CCL4, CCL5, CCL11, CXCL8, CXCL10 and CX3CL1 in the T2DM patients were significantly higher than that in the controls, while no difference in these concentrations was found between the PDM patients and controls.

Conclusion

Progression of T2DM may be associated with elevated concentrations of chemokines.

Meta-Analysis Registration

PROSPERO, identifier CRD42019148305.

A dynamic nomogram for predicting diabetic macular edema in type 2 diabetes patients based on plasma cytokines

OBJECTIVE

This study investigated changes of plasma cytokines and aimed to build a dynamic nomogram for diabetic macular edema (DME) in type 2 diabetes mellitus (T2DM).

METHODS

In a pilot cohort, plasma samples were selected from 9 T2DM patients and 9 DME patients to screen for cytokine differences. The screening cytokines were then validated by enzyme-linked immunoassay in a cohort, which contained 100 DME (DME group) and 100 T2DM patients without DME (T2DM group). A dynamic nomogram for predicting DME was developed, based on the plasma cytokines.

RESULTS

In the pilot cohort, 11 plasma cytokines were significantly increased in the DME group. In the validation cohort, platelet-derived growth factor (PDGF)-BB, tissue inhibitors of metalloproteinase (TIMP)-1, angiopoietin (ANG-1), and vascular endothelial cell growth factor receptor (VEGFR)-2 were confirmed to be significantly elevated in the DME group. The dynamic nomogram demonstrated good calibration and discrimination, with an area under the receiver operating characteristic curve (AUC) of 0.88. In the test set, sensitivity, specificity, and AUC were 73.3%, 80.0%, and 0.84, respectively.

CONCLUSION

Plasma cytokines were closely associated with DME. A novel dynamic monogram including ANG-1, PDGF-BB, TIMP-1, and VEGFR2 was a novel tool for predicting DME.

Aqueous Cytokine Expression and Higher Order OCT Biomarkers: Assessment of the Anatomic-Biologic Bridge in the IMAGINE DME Study

PURPOSE

To identify biomarkers for predicting response to anti-vascular endothelial growth factor (VEGF) therapy in diabetic macular edema (DME) and evaluate any links between cytokine expression and optical coherence tomography (OCT) phenotype.

DESIGN

The IMAGINE is a post hoc image analysis and cytokine expression assessment of the Efficacy & Safety Trial of Intravitreal Injections Combined With PRP for CSME Secondary to Diabetes Mellitus (DAVE) randomized clinical trial.

METHODS

Subjects were categorized as anatomical responders or nonresponders, and within the responder group as rebounders and non-rebounders based on quantitative, longitudinal OCT criteria. Retinal layer and fluid features were extracted using an OCT machine-learning augmented segmentation platform. Responders were further sub-classified by rapidity of response. Aqueous concentrations of 54 cytokines were measured at multiple timepoints. Expression was compared between responder groups and correlated with OCT imaging biomarkers.

RESULTS

Of the 24 eyes studied, 79% were anatomical responders with 38% super responders, 17% early responders, and 25% slow responders. Twenty-one percent were nonresponders. Super responders had increased baseline vascular endothelial growth factor (VEGF) (880.0 pg/mL vs 245.4 pg/mL; P = .012) and decreased monocyte chemotactic protein-1 (MCP-1) (513.3 pg/mL vs 809.5 pg/mL; P = .0.042) concentrations compared with nonresponders. Interleukin-6 (-24.9 pg/mL vs 442.8 pg/mL; P = .032) concentrations increased among nonresponders during therapy. VEGF concentrations correlated with central subfield thickness (r = 0.49; P = .01). Panmacular retinal volume correlated with increased interleuckin-6 (r = 0.47; P = .02) and decreased MCP-1 (r = -0.45; P = .03). Matrix metallopeptidase-1 correlated with subretinal fluid volume (r = 0.50; P = .01).

CONCLUSIONS

OCT imaging biomarkers correlated with both intraocular cytokines and responsiveness to anti-VEGF therapy, which indicated a possible link to underlying pathways and their relevance to DME prognosis. Baseline concentrations of VEGF and MCP-1 are associated with anatomic response to anti-VEGF therapy.

RNA-Seq analysis reveals gene expression changes induced by IL-6 trans-signaling activation in retinal endothelial cells

BACKGROUND

Increasing evidence suggests that interleukin-6 (IL-6) trans-signaling plays a critical role in the pathogenesis of diabetic retinopathy (DR). We have previously shown that activation of IL-6 trans-signaling induces barrier dysfunction in human retinal endothelial cells (HRECs). However, the molecular mechanisms underlying these effects are not clear. The purpose of this study was to discover global gene expression changes in HRECs following activation of IL-6 trans-signaling.

METHODS

HRECs were treated with IL-6 and soluble IL-6R to activate IL-6 trans-signaling, and sgp130Fc treatment was used for IL-6 trans-signaling inhibition. RNA-Seq analyses were performed for global gene expression profiling. Differential expression was determined using DESeq2, and bioinformatic analyses were performed to associate the differentially expressed genes with biological functions and pathways.

RESULTS

Our analyses revealed 445 differentially expressed genes (318 upregulated and 127 downregulated) in HRECs after IL-6 trans-signaling activation. We identified several novel genes not previously associated with IL-6 signaling or endothelial dysfunction. Leukocyte adhesion, diapedesis and chemokine signaling pathways are highly enriched in differentially expressed genes. Inhibition of IL-6 trans-signaling with sgp130Fc abrogated these changes, thus highlighting the therapeutic potential of this drug.

CONCLUSIONS

This study identified significant gene expression changes caused by IL-6 trans-signaling activation in HRECs. Identification of such changes has the potential to uncover the precise molecular mechanisms of IL-6 trans-signaling mediated effects in the pathology of DR.

Microglia and Inflammatory Responses in Diabetic Retinopathy

Diabetic retinopathy is a vision-threatening disease affecting neurons and microvasculature of the retina. The development of this disease is associated with the action of inflammatory factors that are connected to the activation of microglial cells, the resident tissue macrophages of the CNS. In the quiescent state, microglial cells help maintain tissue homeostasis in the retina through phagocytosis and control of low-grade inflammation. However, prolonged tissue stress due to hyperglycemia primes microglia to become overly reactive with the concomitant production of pro-inflammatory cytokines and chemokines causing chronic inflammation. In this review, we provide evidence of microglial cell activation and pro-inflammatory molecules associated with the development and progression of diabetic retinopathy. We further highlight innovative animal models that can mimic the disease in humans and discuss strategies in modulating microglial-mediated inflammation as potential therapeutic approaches in managing the disease.

The role of IL-6-174 G/C polymorphism and intraocular IL-6 levels in the pathogenesis of ocular diseases: a systematic review and meta-analysis

Interleukin-6 (IL-6) is one of the key regulators behind the inflammatory and pathological process associated with ophthalmic diseases. The role of IL-6-174 G/C polymorphism as well as intraocular IL-6 levels among various eye disease patients differ across studies and has not been systematically reviewed. Thus, this study aims to provide a summary to understand the relationship between IL-6 and ophthalmic disease. In total, 8,252 and 11,014 subjects for IL-6-174 G/C and intraocular levels of IL-6, respectively, were retrieved from PubMed, Scopus and Web of Science. No association was found between IL-6-174 G/C polymorphisms with ocular diseases. Subgroup analyses revealed a suggestive association between the GC genotype of IL-6-174 G/C with proliferative diabetic retinopathy (PDR). Further, the level of intraocular IL-6 among ocular disease patients in general was found to be higher than the control group [standardized mean difference (SMD) = 1.41, 95% confidence interval (CI) 1.24-1.58, P < 0.00001]. Closer examination through subgroup analyses yielded similar results in several ocular diseases. This study thus indicates that the IL-6-174 G/C polymorphism does not predispose patients to ocular disease, although the GC genotype is likely to be a genetic biomarker for PDR. Moreover, intraocular IL-6 concentrations are related to the specific manifestations of the ophthalmic diseases. Further studies with larger sample sizes are warranted to confirm this conclusion.

Inflammation and diabetic retinopathy

Purpose

To investigate the relationship between inflammation in the vitreous and diabetic retinopathy.

Methods

Vitreous samples from 21 patients with proliferative diabetic retinopathy (PDR), 21 patients with nonproliferative diabetic retinopathy (NPDR), and 21 nondiabetic patients with idiopathic epiretinal membranes (control) were studied. The interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase (MMP)-2, MMP-9, and adiponectin levels in the vitreous were detected in all samples with enzyme-linked immunosorbent assay (ELISA). Samples were stored at -80 °C until analyzed.

Results

The TNF-α levels in the vitreous were not statistically significant between all groups (p>0.005). The mean IFN-γ levels were statistically significantly higher in patients with PDR (70.98 pg/ml) and patients with NPDR (46.61 pg/ml) than in nondiabetic patients (22.02 pg/ml). There was a difference in the IFN-γ levels in the vitreous between patients with PDR and patients with NPDR (p<0.005). The MMP-2 and MMP-9 concentrations in the vitreous were not different between all groups (p>0.05). There was a correlation between the IFN-γ and TNF-α levels. We investigated the statistically significantly decreased levels of adiponectin in the proliferative (p<0.05) and nonproliferative (p<0.05) diabetic eyes compared to the nondiabetic eyes.

Conclusions

Increased levels of IFN-γ and TNF-α in the vitreous were found in patients with diabetes compared to nondiabetic patients. Decreased levels of adiponectin in the vitreous were found in patients with diabetes compared to nondiabetic patients. The data support the hypothesis that inflammation is associated with diabetic retinopathy.

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

Diabetic retinopathy is one of the leading causes of visual impairment and morbidity worldwide, being the number one cause of blindness in people between 27 and 75 years old. It is estimated that ~191 million people will be diagnosed with this microvascular complication by 2030. Its pathogenesis is due to alterations in the retinal microvasculature as a result of a high concentration of glucose in the blood for a long time which generates numerous molecular changes like oxidative stress. Therefore, this narrative review aims to approach various biomarkers associated with the development of diabetic retinopathy. Focusing on the molecules showing promise as detection tools, among them we consider markers of oxidative stress (TAC, LPO, MDA, 4-HNE, SOD, GPx, and catalase), inflammation (IL-6, IL-1ß, IL-8, IL-10, IL-17A, TNF-α, and MMPs), apoptosis (NF-kB, cyt-c, and caspases), and recently those that have to do with epigenetic modifications, their measurement in different biological matrices obtained from the eye, including importance, obtaining process, handling, and storage of these matrices in order to have the ability to detect the disease in its early stages.

Inflammatory and angiogenic biomarkers in diabetic retinopathy

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes mellitus (DM) and a leading cause of blindness in working-age adults in developed countries. Numerous investigations have recognised inflammation and angiogenesis as important factors in the development of this complication of diabetes. Current methods of DR treatment are predominantly used at advanced stages of the disease and could be associated with serious side effects. Therefore, new diagnostic methods are needed in order to identify the initial stages of DR as well as monitoring the effects of applied therapy. Biochemical biomarkers are molecules found in blood or other biological fluid and tissue that indicate the existence of an abnormal condition or disease. They could be a valuable tool in detecting early stages of DR, identifying patients most susceptible to retinopathy progression and monitoring treatment outcomes. Biomarkers related to DR can be measured in the blood, retina, vitreous, aqueous humour and recently in tears. As the retina represents a small part of total body mass, a circulating biomarker for DR needs to be highly specific. Local biomarkers are more reliable as indicators of the retinal pathology; however, obtaining a sample of aqueous humour, vitreous or retina is an invasive procedure with potential serious complications. As a non-invasive novel method, tear analysis offers a promising direction in further research for DR biomarker detection. The aim of this paper is to review systemic and local inflammatory and angiogenic biomarkers relevant to this sight threatening diabetic complication.

Comparison of inflammatory cytokines levels in the aqueous humor with diabetic retinopathy

PURPOSE

Evidence has accumulated suggesting that various inflammatory cytokines are involved in the progress of diabetic retinopathy (DR), but there are few studies concerning the relationship between individual cytokines levels in the aqueous humor (AH) and the severity of DR. This study aimed to explore the differences of interleukin (IL)-23, IL-17, IL-10 and transforming growth factor (TGF)-β in AH form patients with different proliferative stages of DR.

METHODS

From June 2016 to June 2019, patients for senile cataract surgery were enrolled with the informed consent. All cases were graded into 4 groups: the control group (patients without diabetes), non-retinopathy (NDR) group (diabetic patients without retinopathy), non-proliferative diabetic retinopathy (NPDR) group, and proliferative diabetic retinopathy (PDR) group. The concentrations of IL-23, IL-17, IL-10, and TGF-β in AH were measured using ELISA and compared them within four groups by ANOVA.

RESULTS

In this study, 20 (28.57%), 18 (25.71%), 17 (24.29%), and 15 (21.43%) patients were included in the control, NDR, NPDR, and PDR groups, respectively. There had no significant differences in demographic characteristics (P > 0.05). Comparison of these cytokines within four groups revealed: the IL-23 level was increased in NDR group initially and raised along with the progression of DR (P < 0.01). The IL-17 level was significantly higher in NPDR and PDR groups compared to NDR and the control groups, and positively correlated with more-severe DR (P < 0.01). By contrast, The IL-10 level was significantly lower in diabetic patients than in non-diabetic controls, and decreased as the severity of DR increased (P < 0.05). In addition, TGF-β was also elevated in diabetic patients, but showed no differences based on the presence or severity of DR (P > 0.05).

CONCLUSIONS

The over-expression of IL-23 and IL-17 in AH might have a synergistic effect on the pathogenesis well before the proliferative stage, and was typical positively correlated with the severity of DR. These results offer a novel early therapeutic target for DR.

Concentrations of Selected Cytokines and Vascular Endothelial Growth Factor in Aqueous Humor and Serum of Diabetic Patients

Purpose: To investigate the aqueous humor and serum levels of selected cytokines and vascular endothelial growth factor (VEGF) in diabetic patients, implicating their role in the pathogenesis of diabetic eye complications.Materials and methods:   Atotal of 65 patients (27 males and 38 females) who underwent cataract surgery were recruited into the study. The study group consisted of 30 cataract patients with type 2 diabetes mellitus, and this group was divided into two subgroups: 14 patients with diabetic retinopathy (DR group) and 16 patients without DR (NDR group). The control group consisted of 35 non-diabetic cataract subjects.Results: Patients in the DR group had significantly higher aqueous humor concentrations of interleukin (IL)-1β, IL-6, IL-8, IL-10, monocyte chemotactic protein (MCP-1) and VEGF. Likewise, serum concentrations of IL-1β, IL-6, IL-8, IL-12, TNF-α and IFN-γ were significantly higher in the DR group as compared to the controls. Aqueous humor concentrations of IL-1β, IL-8, MCP-1 and VEGF were significantly higher in the DR group as compared with the NDR group.Conclusion: Our findings support the hypothesis that chronic inflammation and a disturbance of the immune system play important roles in the pathogenesis of diabetic cataract and DR.

Dysregulation of trophic factors contributes to diabetic retinopathy in the Ins2Akita mouse

Diabetic retinopathy (DR) is considered as a diabetes-related complication that can lead to severe visual impairments. By 2030, it is expected that 1 in 5 adults will suffer from the disease. Suitable animal models for chronic DR are essential for a better understanding of the pathophysiology and to further develop new treatments. The Ins2^Akita mouse is a type 1 diabetes model that shows signs of both early and late stages of DR, including pericyte loss, increased vascular permeability, increased acellular capillaries and neovascularization. To further characterize DR in the Ins2^Akita mouse model, we have evaluated the protein levels of the angiogenesis inducers vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) and the angiogenesis inhibitor pigment epithelium-derived factor (PEDF). Additionally, we have analyzed the protein expression profile of the glial markers ionized calcium binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) as well as of the chemokine monocyte chemoattractant protein 1 (MCP-1). In this study we demonstrate that, with disease progression, there is the development of an inflammatory response and an unbalanced expression of pro- and antiangiogenic factors in the neural retina and in the retinal pigment epithelium (RPE) of Ins2^Akita mice. Therefore, our data provide support for the diabetic retinopathy features detected in the Ins2^Akita retina, reflecting what is observed in the human pathology.

Endocannabinoids in aqueous humour of patients with or without diabetes

Objective

The primary aim was to determine endocannabinoid (EC) concentrations of 2-arachidonoylglycerol (2-AG), oleoylethanolamine (OEA), palmitoylethanolamine (PEA) and anandamide (AEA) in the aqueous humour of patients, and to investigate any differences in gender and diabetic or ocular disease status.

Methods and Analysis

Adult participants (age >18 years) listed for a routine cataract surgery were recruited. For patients with diabetes, results from their most recent retinopathy grading were recorded. A sample of aqueous humour was removed from the anterior chamber of the patients and snap-frozen in liquid nitrogen. Levels of 2-AG, PEA, OEA and AEA were measured by liquid chromatography-tandem mass spectrometry.

Results

Aqueous humour samples were taken from 93 patients (female:male=58:35), with a mean age±SD of 72.7±9.5 years. Following gender-specific analysis, the mean aqueous concentration of AEA in female patients without diabetes was significantly higher than in female patients with diabetes (0.20±0.03 nM vs 0.07±0.02 nM, p=0.001). Among female patients with diabetes, the aqueous concentration of 2-AG was higher in those with diabetic retinopathy compared with those with no retinopathy (0.30+0.16 nM vs 0.04±0.01 nM, p=0.0025). The aqueous level of the sum of EC was higher in those with ocular comorbidity (2.49±0.73 vs 1.44±0.17, p=0.0002).

Conclusion

There were gender, diabetes status and comorbidity differences in aqueous humour EC levels. Since EC receptors are present in ocular tissues, including the retina (neurons, glia and endothelial cells), differential levels of ECs in the aqueous humour of patients with and without diabetes may provide a novel therapeutic target for diabetic retinopathy.

Endothelial Dysfunction in Diabetic Retinopathy

Diabetic retinopathy (DR) is a diabetic complication which affects retinal function and results in severe loss of vision and relevant retinal diseases. Retinal vascular dysfunction caused by multifactors, such as advanced glycosylation end products and receptors, pro-inflammatory cytokines and chemokines, proliferator-activated receptor-γ disruption, growth factors, oxidative stress, and microRNA. These factors promote retinal endothelial dysfunction, which results in the development of DR. In this review, we summarize the contributors in the pathophysiology of DR for a better understanding of the molecular and cellular mechanism in the development of DR with a special emphasis on retinal endothelial dysfunction.

Corneal alteration and pathogenesis in diabetes mellitus

The incidence of diabetes mellitus (DM) and its complications have increased considerably worldwide. Diabetic keratopathy is the major complication of the cornea characterized by delayed corneal wound healing, decreasing corneal epithelial sensitivity, and recurrent corneal ulcers. There is accumulating evidence that diabetic keratopathy is correlated with the hyperglycemic state. Different corneal components may produce different alterations under hyperglycemia. In addition, diabetic nerve alteration may become a novel biomarker of early-stage DM. Abnormalities of the corneal nerve plexus have been associated with diabetic inflammatory states. There is rapidly growing evidence based on investigations of diabetic corneal nerves through in vivo confocal microscopy. Understanding the molecular pathogenesis caused by hyperglycemia may assist in the identification of novel biomarkers, as well as therapeutic targets for early treatment. This review mainly summarizes recent findings on corneal alteration and pathogenesis in DM.

Aqueous Humor Mediator and Cytokine Aberrations in Diabetic Retinopathy and Diabetic Macular Edema: A Systematic Review and Meta-Analysis

Purpose

To evaluate the relationship between the aqueous humor levels of VEGF, TNF-α, IL-10, IL-6, IL-12, MCP-1, and IP-10 with DR/DME.

Methods

PubMed, Web of Science, Embase, China National Knowledge Infrastructure (CNKI), and Wanfang databases were searched up to October 2018. Systematic review and meta-analysis were conducted.

Results

18 studies comprising 362 cases with DR (100 with DME) and 620 controls without DR were included in this meta-analysis. There was a significant association between VEGF levels in the aqueous humor and DR (standardized mean difference (SMD) 1.94 (95% CI 1.05-2.83)) and DME (1.07 (0.71, 1.42)). Furthermore, a significant correlation was observed between levels of IL-6 and DR (3.53 (0.37, 6.69)), and similarly correlation with DME (1.26 (0.30, 2.21)). The relationship between MCP-1 and DR and DME was significant, in which the SMD was (0.49 (0.09, 0.89)) and (1.49 (0.78, 2.20)), respectively. However, IL-12, IP-10, and TNF-α had no correlation with DR and DME, whereas there was a significant relationship between IL-8 and DME (1.68 (0.97, 2.40)).

Conclusion

Elevated levels of VEGF, IL-6, and MCP-1 in the aqueous humor were associated with the risk for the presence of DR, and levels of VEGF, IL-6, IL-8, and MCP-1 were associated with the risk of DME. Furthermore, these biomarkers may be used as potential predictors or therapeutic targets for DR/DME.

Usefulness of Liquid Biopsy Biomarkers from Aqueous Humor in Predicting Anti-VEGF Response in Diabetic Macular Edema: Results of a Pilot Study

The objective was to investigate the usefulness of the "liquid biopsy" of aqueous humor (AH) to predict the clinical response after intravitreal injections (IVT) of anti-VEGF agents for treating diabetic macular edema (DME). For this purpose, AH samples obtained during the first anti-VEGF IVT from 31 type two diabetic patients were analyzed. Patients were classified into three groups according to their anti-VEGF response: rapid responders (n = 11), slow responders (n = 11), and non-responders (n = 9). In addition, patients (n = 7) who showed good response to corticosteroids but a delayed or no response to anti-VEGF therapy were analyzed. Levels of 17 different cytokines, chemokines, and growth factors in AH were measured using a multiplex immunoassay. We found higher concentrations of VEGF in rapid responders to anti-VEGF therapy compared to non-responders. In addition, slow responders to anti-VEGF treatment showed higher levels of inflammatory markers than rapid responders, but did not reach statistical significance. Finally, those patients who responded to corticosteroids but not to anti-VEGF therapy showed significantly lower levels of VEGF than patients with rapid response (p = 0.01). In conclusion, "liquid biopsy" of AH could be useful to determine whether the predominant pathogenic event is primarily angiogenic or inflammatory in nature. This approach would allow physicians to select a more rational and cost-effective treatment. Further studies to validate these preliminary results are warranted.

Intraocular Biopsy and ImmunoMolecular Pathology for "Unmasking" Intraocular Inflammatory Diseases

Intraocular inflammation can hide a variety of eye pathologies. In 33% of cases, to obtain a correct diagnosis, investigation of the intraocular sample is necessary. The combined analyses of the intraocular biopsy, using immuno-pathology and molecular biology, point to resolve the diagnostic dilemmas in those cases where history, clinical tests, and ophthalmic and systemic examinations are inconclusive. In such situations, the teamwork between the ophthalmologist and the molecular pathologist is critically important to discriminate between autoimmune diseases, infections, and intraocular tumors, including lymphoma and metastases, especially in those clinical settings known as masquerade syndromes. This comprehensive review focuses on the diagnostic use of intraocular biopsy and highlights its potential to enhance research in the field. It describes the different surgical techniques of obtaining the biopsy, risks, and complication rates. The review is organized according to the anatomical site of the sample: I. anterior chamber containing aqueous humor, II. iris and ciliary body, III. vitreous, and IV. choroid and retina. We have excluded the literature concerning biopsy for choroidal melanoma and retinoblastoma, as this is a specialized area more relevant to ocular oncology.

Imaging and Biomarkers in Diabetic Macular Edema and Diabetic Retinopathy

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is the leading cause of acquired vision loss in adults across the globe. Early identification and treatment of patients with DR is paramount for vision preservation. The aim of this review paper is to outline current and new imaging techniques and biomarkers that are valuable for clinical diagnosis and management of DR.

RECENT FINDINGS

Ultrawide field imaging and automated deep learning algorithms are recent advancements on traditional fundus photography and fluorescein angiography. Optical coherence tomography (OCT) and OCT angiography are techniques that image retinal anatomy and vasculature and OCT is routinely used to monitor response to treatment. Many circulating, vitreous, and genetic biomarkers have been studied to facilitate disease detection and development of new treatments. Recent advancements in retinal imaging and identification of promising new biomarkers for DR have the potential to increase detection, risk stratification, and treatment for patients with DR.

Comprehensive analysis of vitreous humor chemokines in type 2 diabetic patients with and without diabetic retinopathy

AIMS

To compare the vitreous levels of chemokines in diabetic patients with and without retinopathy. To find the relationship between stages of diabetic retinopathy (DR) and levels of vitreous chemokines.

METHODS

The study involved 20 non-diabetic and 20 diabetic patients without clinical signs of DR (NDR) and 40 diabetic patients with proliferative diabetic retinopathy (PDR). The vitreous humor was collected and the levels of 40 chemokines were measured using magnetic color-bead-based multiplex assay.

RESULTS

The control group, NDR group, PDR with vitreous hemorrhage (VH) group, and PDR with tractional retinal detachment group comprised 20, 20, 21, and 19 eyes, respectively. Only the concentration of CCL3 was significantly higher in the NDR group compared with the controls (p = 0.038). Twenty-five types of chemokines were statistically higher in the PDR with VH group in comparison to NDR group (all p < 0.05). All chemokines were statistically higher in the PDR with TRD group in comparison to NDR group (all p < 0.05) apart from 3 chemokines: GM-CSF, MIF, and CCL3(p = 0.086, p = 0.109, p = 0.094, respectively). The concentration of CCL21, CCL15 in PDR with TRD group was significantly higher compared with PDR with VH group, while other 36 chemokines were not significantly different between PDR with VH group and PDR with TRD group.

CONCLUSIONS

The inflammation gradually worsen with the progression of DR. CCL3 may be associated with the onset of early diabetic retinal damage, and CCL15 and CCL21 may be closely related to the formation of fibrovascular membrane and the progression of the end stage of DR.

Interleukin-6 and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Interleukin-6 (IL-6) is produced by a variety of cells involved in inflammation and acts as local intensification signals in pathological processes associated with chronic eye inflammation. This meta-analysis was performed to provide a better understanding of the relationship between IL-6 and diabetic retinopathy.

METHODS

The study was started with systematic search for literatures by using the PubMed, Web of Science and Embase online databases. The standard mean difference (SMD) and its 95% confidence intervals (CIs) were was included and then pooled with a random effects model.

RESULTS

Thirty-one articles, containing1099 DR patients and 1010 controls, were included in this meta-analysis. The level of IL-6 in the DR group was found to be higher than that in the control group (SMD: 2.12, 95% CI: 1.53-2.70, p < 0.00001).Obvious heterogeneity existed between the studies (p < 0.00001, I² = 96%). So a subgroup analysis and sensitivity analysis were performed. Removing the sensitivity studies, the stability of the overall treatment effect was good. Subgroup analysis showed that the levels of IL-6 in case group were observed to be higher than those in the control group; and the IL-6 levels in the proliferative diabetic retinopathy (PDR) group were also higher than those in the non-proliferative diabetic retinopathy (NPDR) group. (SMD: 0.78, 95% CI: 0.26-1.31, p=  0.003) Conclusion: The results from this current meta-analysis indicated that increased level of IL-6 generally exist in DR patients. And it may associated with the severity of DR. However, large-scale and high-quality studies in future are required to confirm the present findings.