Molecular basis of the inner blood-retinal barrier and its breakdown in diabetic macular edema and other pathological conditions

The adaptive immune system in the retina of diabetics

As the prevalence of diabetes mellitus increases each year, its most common microvascular complication, diabetic retinopathy (DR), is also on the rise. DR is now regarded as an inflammatory disease in which innate immunity plays a crucial role, and a large number of innate immune cells with associated cytokines are involved in the pathologic process of DR. The role of adaptive immunity in DR is seldom mentioned, probably due to the general perception of the immune privileged environment of the retina; however, in recent years there has been a gradual increase in research on the role of adaptive immunity in DR, and with the discovery of the retinal lymphatic system, it seems that the role of adaptive immunity can no longer be ignored. Here, we discuss the immunosuppressive environment of the retina, the phenomenon and potential mechanisms of lymphocyte infiltration in DR, and the role of the adaptive immune system in the diabetic retina, which may point the way for future research.

Investigating the impact of empagliflozin on the retina of diabetic mice

BACKGROUND

Diabetic retinopathy (DR) frequently results in compromised visual function, with hyperglycemia-induced disruption of the blood-retinal barrier (BRB) through various pathways as a critical mechanism. Existing DR treatments fail to address early and potentially reversible microvascular alterations. This study examined the effects of empagliflozin (EMPA), a selective Sodium-glucose transporter 2 (SGLT2) inhibitor, on the retina of db/db mice. The objective of this study is to investigate the potential role of EMPA in the prevention and delay of DR.

METHODS

db/db mice were randomly assigned to either the EMPA treatment group (db/db + Emp) or the model group (db/db), while C57 mice served as the normal control group (C57). Mice in the db/db + Emp group received EMPA for eight weeks. Body weight, fasting blood glucose (FBG), and blood VEGF were subsequently measured in all mice, along with the detection of specific inflammatory factors and BRB proteins in the retina. Retinal SGLT2 protein expression was compared using immunohistochemical analysis, and BRB structural changes were observed via electron microscopy.

RESULTS

EMPA reduced FBG, blood VEGF, and retinal inflammatory factors TNF-α, IL-6, and VEGF levels in the eye tissues of db/db mice. EMPA also increased Claudin-1, Occludin-1, and ZO-1 levels while decreasing ICAM-1 and Fibronectin, thereby preserving BRB function in db/db mice. Immunohistochemistry revealed that EMPA reduced SGLT2 expression in the retina of diabetic mice, and electron microscopy demonstrated that EMPA diminished tight junction damage between retinal vascular endothelial cells and prevented retinal vascular basement membrane thickening in diabetic mice.

CONCLUSION

EMPA mitigates inflammation and preserves BRB structure and function, suggesting that it may prevent DR or serve as an effective early treatment for DR.

Applications and latest research progress of liposomes in the treatment of ocular diseases

The special structure of eyes and the existence of various physiological barriers make ocular drug delivery one of the most difficult problems in the pharmaceutical field. Considering the problems of patient compliance, local administration remains the preferred method of drug administration in the anterior part of eyes. However, local administration suffers from poor bioavailability, need for frequent administration, and systemic toxicity. Administration in the posterior part of the eye is more difficult, and intravitreal injection is often used. But intravitreal injection faces the problems of poor patient compliance and likely side effects after multiple injections. The development of nanocarrier technology provides an effective way to solve these problems. Among them, liposomes, as the most widely used carrier in clinical application, have the characteristics of amphiphilic nanostructure, easy surface modification, extended release time, good biocompatibility, etc. The liposomes are expected to overcome obstacles and effectively deliver drugs to the target site to improve ocular drug bioavailability. This review summarized the various controllable properties of liposomes for ocular delivery as well as the application and research progress of liposomes in various ocular diseases. In addition, we summarized the physiological barriers and routes of administration contained in eyes, as well as the prospects of liposomes in the treatment of ocular diseases.

Interplay between Netrin-1 and Norrin controls arteriovenous zonation of blood-retina barrier integrity

The integrity of the blood-retina barrier (BRB) is crucial for phototransduction and vision, by tightly restricting transport of molecules between the blood and surrounding neuronal cells. Breakdown of the BRB leads to the development of retinal diseases. Here, we show that Netrin-1/Unc5b and Norrin/Lrp5 signaling establish a zonated endothelial cell gene expression program that controls BRB integrity. Using single-cell RNA sequencing (scRNA-seq) of postnatal BRB-competent mouse retina endothelial cells (ECs), we identify >100 BRB genes encoding Wnt signaling components, tight junction proteins, and ion and nutrient transporters. We find that BRB gene expression is zonated across arteries, capillaries, and veins and regulated by opposing gradients of the Netrin-1 receptor Unc5b and Lrp5-β-catenin signaling between retinal arterioles and venules. Mice deficient for Ntn1 or Unc5b display more BRB leakage at the arterial end of the vasculature, while Lrp5 loss of function causes predominantly venular BRB leakage. ScRNA-seq of Ntn1 and Unc5b mutant ECs reveals down-regulated β-catenin signaling and BRB gene expression that is rescued by Ctnnb1 overactivation, along with BRB integrity. Mechanistically, we demonstrate that Netrin-1 and Norrin additively enhance β-catenin transcriptional activity and Lrp5 phosphorylation via the Discs large homologue 1 (Dlg1) scaffolding protein, and endothelial Lrp5-Unc5b function converges in protection of capillary BRB integrity. These findings explain how arteriovenous zonation is established and maintained in the BRB and reveal that BRB gene expression is regulated at the level of endothelial subtypes.

Serum inflammation biomarkers level in cystoid and diffuse diabetic macular edema

OBJECTIVE

To assess serum inflammatory biomarker levels in patients with different subtypes of diabetic macular edema (DME).

METHODS

We retrospectively analyzed 50 eyes from 37 treatment-naïve DME patients who underwent intravitreal injection therapy between June and December 2023. Based on the morphological characteristics of macular edema in optical coherence tomography (OCT), the eyes were categorized into the cystoid macular edema (CME) group (n = 25) and diffuse retinal thickening (DRT) group (n = 25). Additionally, 25 eyes with diabetes retinopathy but without DME served as the control group. Comprehensive clinical data were reviewed, including best-corrected visual acuity (BCVA), central macular thickness (CMT), macular cube volume (VOL) and hematological examination. The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII) were calculated.

RESULTS

NLR and SII levels were significantly higher in the CME group compared to the DRT group and control group (all P < 0.01). The optimal ROC cutoff value of NLR for CME was 2.27, with 88.0% sensitivity and 68.0% specificity. The optimal ROC cutoff value of SII for CME was 447.33, with 84.0% sensitivity and 60.0% specificity. After initial intravitreal injection therapy, BCVA and VOL significantly improved in each group (all P < 0.01). However, no significant correlation was found between systemic inflammatory marker levels and postoperative changes in BCVA, CMT and VOL (all P > 0.05).

CONCLUSION

Our study suggests that elevated NLR and SII levels are significantly associated with CME. Elevated serum inflammatory biomarkers may indicate a higher incidence of CME in these patients.

Hyperglycemia-induced oxidative stress exacerbates mitochondrial apoptosis damage to cochlear stria vascularis pericytes via the ROS-mediated Bcl-2/CytC/AIF pathway

OBJECTIVES

Diabetes is closely linked to hearing loss, yet the exact mechanisms remain unclear. Cochlear stria vascularis and pericytes (PCs) are crucial for hearing. This study investigates whether high glucose induces apoptosis in the cochlear stria vascularis and pericytes via elevated ROS levels due to oxidative stress, impacting hearing loss.

METHODS

We established a type II diabetes model in C57BL/6J mice and used auditory brainstem response (ABR), Evans blue staining, HE staining, immunohistochemistry, and immunofluorescence to observe changes in hearing, blood-labyrinth barrier (BLB) permeability, stria vascularis morphology, and apoptosis protein expression. Primary cultured stria vascularis pericytes were subjected to high glucose, and apoptosis levels were assessed using flow cytometry, Annexin V-FITC, Hoechst 33342 staining, Western blot, Mitosox, and JC-1 probes.

RESULTS

Diabetic mice showed decreased hearing thresholds, reduced stria vascularis density, increased oxidative stress, cell apoptosis, and decreased antioxidant levels. High glucose exposure increased apoptosis and ROS content in pericytes, while mitochondrial membrane potential decreased, with AIF and cytochrome C (CytC) released from mitochondria to the cytoplasm. Adding oxidative scavengers reduced AIF and CytC release, decreasing pericyte apoptosis.

DISCUSSION

Hyperglycemia may induce mitochondrial apoptosis of cochlear stria vascularis pericytes through oxidative stress.

20(R)-ginsenoside Rg3 alleviates diabetic retinal injury in T2DM mice by attenuating ROS-mediated ER stress through the activation of the Nrf2/HO-1 axis

BACKGROUND

Although our previous work confirmed 20(R)-ginsenoside Rg3 (R-Rg3), which is an active ingredient in the Panax Ginseng C.A. Meyer, to have good anti-diabetic activity, its beneficial effect on diabetic retinal injury was found to be limited.

PURPOSE

This study aims to investigate the protective effects of R-Rg3 on diabetes-induced retinal injury and the associated molecular mechanisms of action.

METHODS

Diabetic retinal injury was induced in mice using a combination of a high-fat diet (HFD) and intraperitoneal injection of streptozotocin (STZ). R-Rg3 (10 and 20 mg/kg) was subsequently administered for 6 weeks. The human retinal endothelial cells (HRECs) were subjected to high glucose (HG)-induced injury for the in vitro analysis and treated with R-Rg3 (4, 8, 16 μM), antioxidant N-Acetylcysteine (NAC, 1 mM) and Nrf2 inhibitor ML385 (5 μM). The mice retinas then underwent functional and histopathological analysis. Expression levels of proteins related to the Nrf2/HO-1 axis, tight junction proteins, endoplasmic reticulum (ER) stress and the apoptosis in retinal tissue and HRECs were determined by western blot. Expressions of ZO-1 and Nrf2 in the retina and HRECs were assessed by immunofluorescence. Additional evaluations included measuring body weights, fasting blood glucose (FBG), lipid levels and oxidative markers.

RESULTS

The results showed 6 weeks of R-Rg3 treatment significantly restored the functional changes and redox system imbalance that was induced by HFD/STZ in mice. R-Rg3 was also found to significantly reduce retinal barrier damage and thickness changes resulting from hyperglycaemia exposure. At the same time, R-Rg3 also protected HRECs from HG-induced damage. R-Rg3 could also activate Nrf2/HO-1 axis and inhibit endoplasmic reticulum stress as a means of alleviating retinal endothelial cells apoptosis. The molecular docking results also demonstrated that R-Rg3 had a good binding ability with Nrf2.

CONCLUSION

Our study suggested Nrf2/HO-1 axis might be crucial for the ability of R-Rg3 to prevent diabetic retinal injury.

Determination of osteopontin in monitoring retinal damage in metabolic syndrome

Metabolic syndrome (MetS) is becoming an increasing public health challenge. Many of the individual components of MetS are associated with ocular changes, but it is not yet clear what the association is. It is known that MetS can lead to diabetes and hence its consequences such as retinopathy. Osteopontin (OPN) is a phosphoglycoprotein that appears to be implicated in diabetic retinopathy. Given the involvement of OPN in retinal damage, the aim of this research was to evaluate OPN expression and its variation over time in a model of MetS induced by 30% fructose consumption for 1, 2 and 3 months. The weight of the animals and the consumption of food and fructose/water were evaluated during the experiment. The results showed a time-dependent increase in weight and liquid consumption in animals treated with fructose, while there was no significant difference in food consumption. Subsequently, the biochemical parameters confirmed that the animals treated with fructose, over time, underwent alterations like those found in patients with MetS. We then moved on to the evaluation of OPN and microglia. In both cases, we observed a time-dependent increase in OPN and Iba-1 in fructose consumption. Furthermore, the results showed a gradual loss of ZO-1 and occludin levels over time. Thus identification of OPN in patients with MetS could be used as an early marker of retinal damage, and this could help to prevent the complications related to the progression of this pathology.

Deciphering the Connection Between Microvascular Damage and Neurodegeneration in Early Diabetic Retinopathy

Diabetic retinopathy (DR), a common diabetes complication leading to vision loss, presents early clinical signs linked to retinal vasculature damage, affecting the neural retina at advanced stages. However, vascular changes and potential effects on neural cells before clinical diagnosis of DR are less well understood. To study the earliest stages of DR, we performed histological phenotyping and quantitative analysis on postmortem retinas from 10 donors with diabetes and without signs of DR (e.g., microaneurysms, hemorrhages), plus three control eyes and one donor eye with DR. We focused on capillary loss in the deeper vascular plexus (DVP) and superficial vascular plexus (SVP), and on neural retina effects. The eye with advanced DR had profound vascular and neural damage, whereas those of the 10 randomly selected donors with diabetes appeared superficially normal. The SVP was indistinguishable from those of the control eyes. In contrast, more than half of the retinas from donors with diabetes had capillary dropout in the DVP and increased capillary diameter. However, we could not detect any localized neural cell loss in the vicinity of dropout capillaries. Instead, we observed a subtle pan-retinal loss of inner nuclear layer cells in all diabetes cases (P < 0.05), independent of microvascular damage. In conclusion, our findings demonstrate a novel histological biomarker for early-stage diabetes-related damage in the human postmortem retina; the biomarker is common in people with diabetes before clinical DR diagnosis. Furthermore, the mismatch between capillary dropout and neural loss leads us to question the notion of microvascular loss directly causing neurodegeneration at the earliest stages of DR, so diabetes may affect the two readouts independently.

ARTICLE HIGHLIGHTS

Senescent endothelial cells: a potential target for diabetic retinopathy

Diabetic retinopathy (DR) is a diabetic complication that results in visual impairment and relevant retinal diseases. Current therapeutic strategies on DR primarily focus on antiangiogenic therapies, which particularly target vascular endothelial growth factor and its related signaling transduction. However, these therapies still have limitations due to the intricate pathogenesis of DR. Emerging studies have shown that premature senescence of endothelial cells (ECs) in a hyperglycemic environment is involved in the disease process of DR and plays multiple roles at different stages. Moreover, these surprising discoveries have driven the development of senotherapeutics and strategies targeting senescent endothelial cells (SECs), which present challenging but promising prospects in DR treatment. In this review, we focus on the inducers and mechanisms of EC senescence in the pathogenesis of DR and summarize the current research advances in the development of senotherapeutics and strategies that target SECs for DR treatment. Herein, we highlight the role played by key factors at different stages of EC senescence, which will be critical for facilitating the development of future innovative treatment strategies that target the different stages of senescence in DR.

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

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

Association between renal function and the Treatment of Diabetic Macular Edema in Long-Term Cohort Study

To determine the correlation between the severity of chronic kidney disease (CKD) and treatment of diabetic macular edema (DME). The retrospective 2-year cohort study included eyes with DME confirmed using spectral-domain optical coherence tomography in Taipei Veterans General Hospital, Taiwan, between 2010 and 2020. All the eyes were treated with an intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) during regular follow-up around 2 years. They were categorized into 3 different groups: an estimated glomerular filtration rate ≥ 60 (mL/min per 1.73 m2) (group A), < 60 (group B), and patients undergoing hemodialysis (group C). The main outcome measures were (1) visual improvement, (2) structural improvement, and (3) the injection frequency of anti-VEGF in the different groups. In this study, 167 eyes from 120 patients were enrolled. Compared with groups B and C, the eyes in group A experienced the only significant visual improvement at month 3, month 6, and month 12 (P = 0.0001, 0.0002, 0.0013, respectively). The presence of subretinal fluid and intraretinal cysts was significantly decreased in groups A and B. In the treatment frequency analysis, the number of injections was the highest in group A and lowest in group C during the study period (P = 0.04). The severity of CKD had an impact on the DME treatment. The less severe CKD was, the greater the visual improvement that could be achieved. In addition, relatively poor renal function required a lower anti-VEGF injection frequency. The active prevention of the progression of CKD may play a key role in DME treatment.

The mRNA Stability of PIEZO1, Regulated by Methyltransferase-Like 3 via N6-Methylation of Adenosine Modification in a YTH Domain Family 2-Dependent Manner, Facilitates the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is the major ocular complication of diabetes caused by chronic hyperglycemia, which leads to incurable blindness. Currently, the effectiveness of therapeutic interventions is limited. This study aimed to investigate the function of piezo-type mechanosensitive ion channel component 1 (PIEZO1) and its potential regulatory mechanism in DR progression. The results showed that PIEZO1 expression was up-regulated in the retinal tissues of streptozotocin-induced diabetic mice and high-glucose (HG)-triggered Müller cells. Functionally, the knockdown of PIEZO1 improves the abnormal retinal function of diabetic mice and impedes inflammatory cytokine secretion and gliosis of Müller cells under HG conditions. Mechanistic investigations using RNA immunoprecipitation-real-time quantitative PCR, methylation RNA immunoprecipitation-real-time quantitative PCR, and luciferase reporter assays demonstrated that PIEZO1 was a downstream target of methyltransferase-like 3 (METTL3). These studies revealed that METTL3-mediated N6-methyladenosine (m6A) modification within the coding sequence of PIEZO1 mRNA significantly shortened its half-life. In HG-stimulated cells, there was a negative regulatory relationship between PIEZO1 and YTH domain family 2 (YTHDF2), a recognized m6A reader. The loss of YTHDF2 resulted in an extended half-life of PIEZO1 in cells with overexpression of METTL3, indicating that the effect of METTL3 on the mRNA stability of PIEZO1 was dependent on YTHDF2. Taken together, this study demonstrated the protective role of the PIEZO1 silencing in DR development, and the degradation of PIEZO1 mRNA is accelerated by METTL3/YTHDF2-mediated m6A modification.

Molecular Mechanisms of Glaucoma Pathogenesis with Implications to Caveolin Adaptor Protein and Caveolin-Shp2 Axis

Glaucoma is a common retinal disorder characterized by progressive optic nerve damage, resulting in visual impairment and potential blindness. Elevated intraocular pressure (IOP) is a major risk factor, but some patients still experience disease progression despite IOP-lowering treatments. Genome-wide association studies have linked variations in the Caveolin1/2 (CAV-1/2) gene loci to glaucoma risk. Cav-1, a key protein in caveolae membrane invaginations, is involved in signaling pathways and its absence impairs retinal function. Recent research suggests that Cav-1 is implicated in modulating the BDNF/TrkB signaling pathway in retinal ganglion cells, which plays a critical role in retinal ganglion cell (RGC) health and protection against apoptosis. Understanding the interplay between these proteins could shed light on glaucoma pathogenesis and provide potential therapeutic targets.

Jagged1-Notch1 Signaling Pathway Induces M1 Microglia to Disrupt the Barrier Function of Retinal Microvascular Endothelial Cells

PURPOSE

Microglia-related inflammation is closely linked to the pathogenesis of retinal diseases. The primary objective of this research was to investigate the impact and mechanism of M1 phenotype microglia on the barrier function of retina microvascular endothelial cells.

METHODS

Quantitative polymerase chain reactions and western blot techniques were utilized to analysis the mRNA and protein expressions of M1 and M2 markers of human microglial clone 3 cell line (HMC3), as well as the levels of Notch ligands and receptors under the intervention of lipopolysaccharide (LPS) or interleukin (IL)-4. ELISA was utilized to detect the pro-inflammatory and anti-inflammatory cytokines from HMC3 cells. The cellular tight junction and apoptosis of human retinal microvascular endothelial cells (HRMECs) were assessed by western blot and fluorescein isothiocyanate-dextran permeability assay. The inhibitors of Notch1 and RNA interference (RNAi) targeting Jagged1 were used to assess their contribution to the barrier function of vascular endothelial cells.

RESULTS

Inducible nitric oxide synthase (iNOS) and IL-1β were considerably elevated in LPS-treated HMC3, while CD206 and Arg-1 markedly elevated under IL-4 stimulation. The conditioned medium derived from LPS-treated HMC3 cells promoted permeability, diminished the expression of zonula occludens-1 and Occludin, and elevated the expression of Cleaved caspase-3 in HRMECs. RNAi targeting Jagged1 or Notch1 inhibitor could block M1 HMC3 polarization and maintain barrier function of HRMECs.

CONCLUSION

Our findings suggest that Jagged1-Notch1 signaling pathway induces M1 microglial cells to disrupt the barrier function of HRMECs, which may lead to retinal diseases.

Remote ischemic conditioning slows blood-retinal barrier damage in type 1 diabetic rats

Diabetic retinopathy (DR) is one of the major complications of diabetes and can cause severe visual impairment. Blood-retina barrier (BRB) destruction resulted from chronic hyperglycemia underlines its major pathological process. However, current treatments have limited efficacy and may even cause serious complications. Remote ischemic conditioning (RIC), through repeated transient mechanical occlusion of limb blood vessels, has been confirmed to promote blood-brain barrier integrity after stroke, but its role in BRB disruption has not been elucidated. This study aimed to investigate the protective effects of RIC on the BRB in diabetic rats and its potential mechanisms. 48 Sprague-Dawley rats were randomly assigned to the Sham group, Sham + RIC group, diabetes mellitus (DM) group and DM+RIC group. The diabetic model was successfully induced by intraperitoneal injection of streptozotocin. RIC treatment was administered daily and lasted for 9 weeks. In functional analysis, RIC improved the retinal function based on electroretinogram data and reduced the leakage of BRB in diabetic rats. In proteomic analysis, tight junction pathway was enriched after RIC treatment, in which Patj gene was significantly increased. We also found that RIC increased mRNA levels of Patj, claudin-1 and zonula occludens (ZO)-1, protein expression of claudin-1 when compared with diabetic models. In conclusion, RIC slowed BRB damage in diabetic rats, which may be related to the preservation of tight junction proteins. RIC may be a promising protective strategy for the treatment of DR.

Optical coherence tomography angiography for microaneurysms in anti-vascular endothelial growth factor treated diabetic macular edema

BACKGROUND

We aimed to evaluate microaneurysms (MAs) after treatment with anti-vascular endothelial growth factor (anti-VEGF) therapy to understand causes of chronic edema and anti-VEGF resistance.

METHODS

Patients with non-proliferative diabetic retinopathy, with or without macular edema were recruited. Optical coherence tomography angiography (OCTA) MAs-related parameters were observed, including the maximum diameter of overall dimensions, material presence, and flow signal within the lumen. OCTA parameters also included central macular thickness (CMT), foveal avascular zone, superficial and deep capillary plexuses, and non-flow area measurements on the superficial retinal slab.

RESULTS

Overall, 48 eyes from 43 patients were evaluated. CMT differed significantly between the diabetic macular edema (DME ) and non-DME (NDME) groups at 1st, 2nd, 3rd, and 6th months of follow-up (P < 0.001; <0.001; 0.003; <0.001, respectively). A total of 55 and 59 MAs were observed in the DME (mean = 99.40 ± 3.18 μm) and NDME (mean maximum diameter = 74.70 ± 2.86 μm) groups at baseline, respectively (significant between-group difference: P < 0.001). Blood flow signal was measurable for 46 (83.6%) and 34 (59.3%) eyes in the DME and NDME groups, respectively (significant between-group difference: P < 0.001).

CONCLUSIONS

Compared to the NDME group, the DME group had larger MAs and a higher blood-flow signal ratio. Following anti-VEGF therapy, changes in the diameter of MAs were observed before changes in CMT thickness.

Artificial intelligence-based extraction of quantitative ultra-widefield fluorescein angiography parameters in retinal vein occlusion

OBJECTIVE

To examine the association between quantitative vascular parameters extracted from intravenous fluorescein angiography (IVFA) and baseline clinical characteristics of patients with retinal vein occlusion (RVO).

METHODS

Our prospective single-centre study in Toronto, Canada, recruited patients with a diagnosis of macular edema secondary to RVO presenting with a central macular thickness (CMT) ≥310 μm from 2017 to 2023. IVFA images were captured using an ultra-widefield scanning laser ophthalmoscope and processed using the artificial intelligence-based RETICAD system to extract quantitative measurements of blood flow, perfusion, and blood-retinal barrier (BRB) permeability. Univariable and multivariable regression models were used to investigate associations between quantitative IVFA parameters and baseline best-corrected visual acuity (BCVA), CMT, and macular volume.

RESULTS

The study included 41 eyes from 41 RVO patients. In the multivariable analysis, BRB permeability was significantly associated with both CMT (p < 0.001) and macular volume (p = 0.005). Subgroup analyses revealed that in central RVO patients, central BRB permeability remained significantly associated with CMT (p = 0.022) and macular volume (p = 0.010); however, there was no association with BCVA (p = 0.921). In branch RVO patients, central BRB permeability was significantly associated with BCVA (p = 0.006) and CMT (p = 0.009), but not with macular volume (p = 0.723). Additionally, both central and peripheral BRB permeability were significantly higher in patients with RVO compared to healthy controls (p < 0.001).

CONCLUSIONS

Our investigation reveals novel associations between baseline clinical characteristics and quantitative IVFA parameters in RVO patients, which may serve as clinically relevant biomarkers. Future studies should explore these associations in diverse RVO patient populations with extended follow-up.

Suppression of inner blood-retinal barrier breakdown and pathogenic Müller glia activation in ischemia retinopathy by myeloid cell depletion

Ischemic retinopathies including diabetic retinopathy are major causes of vision loss. Inner blood-retinal barrier (BRB) breakdown with retinal vascular hyperpermeability results in macular edema. Although dysfunction of the neurovascular unit including neurons, glia, and vascular cells is now understood to underlie this process, there is a need for fuller elucidation of the underlying events in BRB dysfunction in ischemic disease, including a systematic analysis of myeloid cells and exploration of cellular cross-talk. We used an approach for microglia depletion with the CSF-1R inhibitor PLX5622 (PLX) in the retinal ischemia-reperfusion (IR) model. Under non-IR conditions, PLX treatment successfully depleted microglia in the retina. PLX suppressed the microglial activation response following IR as well as infiltration of monocyte-derived macrophages. This occurred in association with reduction of retinal expression of chemokines including CCL2 and the inflammatory adhesion molecule ICAM-1. In addition, there was a marked suppression of retinal neuroinflammation with reduction in expression of IL-1b, IL-6, Ptgs2, TNF-a, and Angpt2, a protein that regulates BRB permeability. PLX treatment significantly suppressed inner BRB breakdown following IR, without an appreciable effect on neuronal dysfunction. A translatomic analysis of Müller glial-specific gene expression in vivo using the Ribotag approach demonstrated a strong suppression of Müller cell expression of multiple pro-inflammatory genes following PLX treatment. Co-culture studies of Müller cells and microglia demonstrated that activated microglia directly upregulates Müller cell-expression of these inflammatory genes, indicating Müller cells as a downstream effector of myeloid cells in retinal IR. Co-culture studies of these two cell types with endothelial cells demonstrated the ability of both activated microglia and Müller cells to compromise EC barrier function. Interestingly, quiescent Müller cells enhanced EC barrier function in this co-culture system. Together this demonstrates a pivotal role for myeloid cells in inner BRB breakdown in the setting of ischemia-associated disease and indicates that myeloid cells play a major role in iBRB dysregulation, through direct and indirect effects, while Müller glia participate in amplifying the neuroinflammatory effect of myeloid cells.

Changes in Macular Pigment Optical Density after Intravitreal Faricimab in Neovascular Age-Related Macular Degeneration: A Pilot Study

Background: This study aimed to evaluate the effects of faricimab intravitreal injections in patients with exudative age macular degeneration (nAMD) after the loading dose using spectral domain optical coherence tomography (SD-OCT) and macular pigment optical density (MPOD). Methods: In this observational prospective study, we enlisted a total of 12 consecutive eyes of 12 patients (six females, six males; mean age 70.47 ± 2.46 years) affected by nAMD who consecutively presented to the Eye Clinic of the University of Naples "Federico II" and Monaldi Hospital of Naples, from June 2023 to December 2023. All patients received four once-monthly intravitreal injections of faricimab (6 mg/0.05 mL) (loading phase). At baseline and 1 month after the fourth faricimab monthly injection, all patients underwent assessment of best correct visual acuity (BCVA) and ophthalmic examination, including slit-lamp biomicroscopy, intraocular pressure (IOP), fundus biomicroscopy, SD-OCT, and MPOD. Results: A total of 12 eyes of 12 patients (six women, six men; mean age 70.47 ± 2.46 years) were included in this study. A statistically significant raise in BCVA and MOPD parameters was shown between baseline and after the loading phase (p < 0.001). Conclusions: Intravitreal injections of faricimab led in the short term to a significant functional and MPOD improvement along with a decrease in central macular thickness (CMT) and thus appears to be an effective treatment option without relevant adverse effects. MOPD may be considered as a prognostic factor associated with a good visual prognosis after intravitreal injections treatment.

Postmortem biochemistry of GFAP, NSE and S100B in cerebrospinal fluid and in vitreous humor for estimation of postmortem interval: a pilot study

Postmortem interval (PMI) is a challenging issue in forensic practice. Although postmortem biomarkers of traumatic brain injury (TBI) are recognised as an emerging resource for PMI estimation, their role remains controversial. This study aims to evaluate postmortem concentrations of three TBI biomarkers (GFAP, NSE and S100B) in two matrices (cerebrospinal fluid and vitreous humor), in order to find out if these markers could be adopted in PMI estimation. Thirty-five deceased individuals with known PMI who underwent forensic autopsy at the University of Parma were examined. Matrices were collected during autopsy, then biomarker concentrations were determined through the enzyme-linked immunosorbent assay. Statistical significance of the data in relation to PMI was studied. The correlation of biomarkers with PMI, examined with samples divided into six groups according to the number of days elapsed since death, was not statistically significant, although S100B in cerebrospinal fluid showed an increasing trend in cases from 1 to 5 days of PMI. Comparison between cases with 1 day of PMI and those with 2 or more days of PMI showed a statistically significant correlation for GFAP and NSE in cerebrospinal fluid. GFAP and NSE in cerebrospinal fluid represent appropriate biomarkers in PMI estimation to distinguish cases with one day of PMI from those with two or more days of PMI. The current study was limited by the scarcity of the cohort and the narrow spectrum of cases. Further research is needed to confirm these observations.

A Glucose-Responsive Hydrogel Inhibits Primary and Secondary BRB Injury for Retinal Microenvironment Remodeling in Diabetic Retinopathy

Current diabetic retinopathy (DR) treatment involves blood glucose regulation combined with laser photocoagulation or intravitreal injection of vascular endothelial growth factor (VEGF) antibodies. However, due to the complex pathogenesis and cross-interference of multiple biochemical pathways, these interventions cannot block disease progression. Recognizing the critical role of the retinal microenvironment (RME) in DR, it is hypothesized that reshaping the RME by simultaneously inhibiting primary and secondary blood-retinal barrier (BRB) injury can attenuate DR. For this, a glucose-responsive hydrogel named Cu-PEI/siMyD88@GEMA-Con A (CSGC) is developed that effectively delivers Cu-PEI/siMyD88 nanoparticles (NPs) to the retinal pigment epithelium (RPE). The Cu-PEI NPs act as antioxidant enzymes, scavenging ROS and inhibiting RPE pyroptosis, ultimately blocking primary BRB injury by reducing microglial activation and Th1 differentiation. Simultaneously, MyD88 expression silence in combination with the Cu-PEI NPs decreases IL-18 production, synergistically reduces VEGF levels, and enhances tight junction proteins expression, thus blocking secondary BRB injury. In summary, via remodeling the RME, the CSGC hydrogel has the potential to disrupt the detrimental cycle of cross-interference between primary and secondary BRB injury, providing a promising therapeutic strategy for DR.

Long-term visual outcomes and fluid compartment changes in limited-early versus early response to anti-VEGF treatment for diabetic macular edema

OBJECTIVE

This study assessed best visual acuity (BVA) and central subfield thickness (CST) outcomes for LER (limited early responder) and ER (early responder) patients at 24 and 36 months.

DESIGN

Retrospective chart review PARTICIPANTS: One-hundred and twelve patients characterized at 3 months after their first anti-VEGF injections as either LER if they met the anatomic criteria (aLER = CST reductions ≤ 10%), visual criteria (vLER = ETDRS letter gains < 5 letter), or both (cLER). All other patients were classified as ER (aER/vER/cER).

METHODS

Variables collected include CST and ETDRS letters at baseline, 3, 24, and 36 months following injections, comorbidities, smoking status, demographics, baseline systemic factors, and the type and quantity of anti-VEGF injections. Analyses were performed using Welch's t-test, multivariable linear and multivariable logistic regression.

RESULTS

BVA changes from 3 months were significant between cLER versus cER and vLER versus vER groups (p < 0.05). There was a greater decrease in mean BVA from 3 months to 36 months in the cER group compared to the cLER group. Alternatively, mean BVA decreased in the vER cohort, while the vLER cohort slightly increased. CST changes from 3 months were statistically significant (p < 0.01) between all LER and ER groups with LER groups showing greater reductions compared to ER counterparts. BVA and CST changes from baseline to 24 and 36 months were not significant after controlling for baseline differences between LER and ER groups.

CONCLUSION

Results highlight the value of long-term anti-VEGF treatment and the need to further explore options that may lead to continued BVA improvements beyond 3 months.

Alisol A, the Eye-Entering Ingredient of Alisma orientale, Relieves Macular Edema Through TNF-α as Revealed by UPLC-Triple-TOF/MS, Network Pharmacology, and Zebrafish Verification

Purpose

Alisma orientale (AO, Alisma orientale (Sam). Juzep) has been widely employed for the treatment of macular edema (ME) in traditional Chinese medicine due to its renowned water-relief properties. Nonetheless, the comprehensive investigation of AO in alleviating ME remained unexplored. This study aims to identify the active components of AO that target the eye and investigate its pharmacological effects and mechanisms on ME.

Methods

The study commenced with UPLC-Triple-TOF/MS analysis to identify the primary constituents of AO. Zebrafish eye tissues were then analyzed after a five-day administration of AO to detect absorbed components and metabolites. Subsequently, network pharmacology, molecular docking, and molecular dynamics simulations were employed to predict the mechanisms of ME treatment via biological target pathways. In vivo experiments were conducted to corroborate the pharmacological actions and mechanisms.

Results

A total of 7 compounds, consisting of 2 prototype ingredients and 5 metabolites (including isomers), were found to traverse the blood-eye barrier and localized within eye tissues. Network pharmacology results showed that AO played a role in the treatment of ME mainly by regulating the pathway network of PI3K-AKT and MAPK with TNF-α centered. Computational analyses suggested that 11-dehydro-16-oxo-24-deoxy-alisol A, a metabolite of alisol A, mitigates edema through TNF-α inhibition. Furthermore, zebrafish fundus confocal experiments and HE staining of eyes confirmed the attenuating effects of alisol A on fundus angiogenesis and ocular edema, representing the first report of AO's ME-inhibitory effects.

Conclusion

In this study, computational analyses with experimental validation were used to understand the biological activity and mechanism of alisol A in the treatment of ME. The findings shed light on the bioactive constituents and pharmacological actions of AO, offering valuable insights and a theoretical foundation for its clinical application in managing ME.

Natural plant medications for the treatment of retinal diseases: The blood-retinal barrier as a clue

BACKGROUND

Retinal diseases significantly contribute to the global burden of visual impairment and blindness. The occurrence of retinal diseases is often accompanied by destruction of the blood‒retinal barrier, a vital physiological structure responsible for maintaining the stability of the retinal microenvironment. However, detailed summaries of the factors damage the blood‒retinal barrier and treatment methods involving natural plant medications are lacking.

PURPOSE

To comprehensively summarize and analyze the protective effects of active substances in natural plant medications on damage to the blood-retina barrier that occurs when retinal illnesses, particularly diabetic retinopathy, and examine their medicinal value and future development prospects.

METHODS

In this study, we searched for studies published in the ScienceDirect, PubMed, and Web of Science databases. The keywords used included natural plant medications, plants, natural herbs, blood retinal barrier, retinal diseases, diabetic retinopathy, age-related macular degeneration, and uveitis. Chinese herbal compound articles, non-English articles, warning journals, and duplicates were excluded from the analysis.

RESULTS

The blood‒retinal barrier is susceptible to high glucose, aging, immune responses, and other factors that destroy retinal homeostasis, resulting in pathological changes such as apoptosis and increased vascular permeability. Existing studies have shown that the active compounds or extracts of many natural plants have the effect of repairing blood-retinal barrier dysfunction. Notably, berberine, puerarin, and Lycium barbarum polysaccharides exhibited remarkable therapeutic effects. Additionally, curcumin, astragaloside IV, hesperidin, resveratrol, ginsenoside Rb1, luteolin, and Panax notoginseng saponins can effectively protect the blood‒retinal barrier by interfering with distinct pathways. The active ingredients found in natural plant medications primarily repair the blood‒retinal barrier by modulating pathological factors such as oxidative stress, inflammation, pyroptosis, and autophagy, thereby alleviating retinal diseases.

CONCLUSION

This review summarizes a series of plant extracts and plant active compounds that can treat retinal diseases by preventing and treating blood‒retinal barrier damage and provides reference for the research of new drugs for treating retinal diseases.

Microvascular destabilization and intricated network of the cytokines in diabetic retinopathy: from the perspective of cellular and molecular components

Microvascular destabilization is the primary cause of the inner blood-retinal barrier (iBRB) breakdown and increased vascular leakage in diabetic retinopathy (DR). Microvascular destabilization results from the combinational effects of increased levels of growth factors and cytokines, involvement of inflammation, and the changed cell-to-cell interactions, especially the loss of endothelial cells and pericytes, due to hyperglycemia and hypoxia. As the manifestation of microvascular destabilization, the fluid transports via paracellular and transcellular routes increase due to the disruption of endothelial intercellular junctional complexes and/or the altered caveolar transcellular transport across the retinal vascular endothelium. With diabetes progression, the functional and the structural changes of the iBRB components, including the cellular and noncellular components, further facilitate and aggravate microvascular destabilization, resulting in macular edema, the neuroretinal damage and the dysfunction of retinal inner neurovascular unit (iNVU). Although there have been considerable recent advances towards a better understanding of the complex cellular and molecular network underlying the microvascular destabilization, some still remain to be fully elucidated. Recent data indicate that targeting the intricate signaling pathways may allow to against the microvascular destabilization. Therefore, efforts have been made to better clarify the cellular and molecular mechanisms that are involved in the microvascular destabilization in DR. In this review, we discuss: (1) the brief introduction of DR and microvascular destabilization; (2) the cellular and molecular components of iBRB and iNVU, and the breakdown of iBRB; (3) the matrix and cell-to-cell contacts to maintain microvascular stabilization, including the endothelial glycocalyx, basement membrane, and various cell-cell interactions; (4) the molecular mechanisms mediated cell-cell contacts and vascular cell death; (5) the altered cytokines and signaling pathways as well as the intricate network of the cytokines involved in microvascular destabilization. This comprehensive review aimed to provide the insights for microvascular destabilization by targeting the key molecules or specific iBRB cells, thus restoring the function and structure of iBRB and iNVU, to treat DR.

Intravitreal Injection of Conbercept Combined with Dexamethasone for Macular Edema Following Central Retinal Vein Occlusion

Background

To compare the efficacy of intravitreal injections of Conbercept combined with dexamethasone (DEX) for macular edema (ME) following central retinal vein occlusion (CRVO).

Methods

This was a prospective, single-masked, randomised, controlled clinical trial. Patients with ME following CRVO were randomised into groups to receive intravitreal injections of 0.5 mg Conbercept plus 0.2 mg DEX or 0.5 mg Conbercept alone on day 0 followed by repeat injections as indicated. The primary outcome measure was the change in best-corrected visual acuity (BCVA) from baseline to month 12. Secondary outcome measures included decrease in central retinal thickness (CRT), injection frequency and interval and percentage of patients who gained more than 15 ETDRS letters or achieved a CRT of < 250 μm at month 12.

Results

33 males (51%) and 32 females (49%) were initially recruited with an average age of 56.64 ± 13.88 years. Patients in the Conbercept and Conbercept + DEX groups gained an average of 14.55 ± 19.19 and 14.88 ± 17.68 ETDRS letters, respectively, at months 12 (t = 4.221, P = 0.000; and t = 4.834, P = 0.000) with no significant difference between the two groups (t = 0.071, P = 0.943). In the Conbercept group, the mean reduction in CRT from baseline to month 12 was 435.26 ± 293.37 μm (t = 8.261, P = 0.000) compared to 431.36 ± 294.55 (t = 8.413, P = 0.000) in the Conbercept + DEX group. There was no significant difference between the two groups (t = 0.053, P = 0.958). The Conbercept + DEX group received fewer intravitreal injections. No major complications occurred.

Conclusion

Conbercept, alone or with DEX, can improve BCVA and reduce CRT in ME following CRVO without serious adverse events. The treatment interval was longer in the Conbercept + DEX group.

Trial Registration

The study was registered with the Chinese Clinical Trial Registry at 5 July 2017. (http://www.chictr.org.cn, 05/07/2017 Registration Number: ChiCTR-INR-17011877).

Nuclear proteins and diabetic retinopathy: a review

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

Global research trends and future directions in diabetic macular edema research: A bibliometric and visualized analysis

BACKGROUND

Diabetic Macular Edema (DME) significantly impairs vision in diabetics, with varied patient responses to current treatments like anti-vascular endothelial growth factor (VEGF) therapy underscoring the necessity for continued research into more effective strategies. This study aims to evaluate global research trends and identify emerging frontiers in DME to guide future research and clinical management.

METHODS

A qualitative and quantitative analysis of publications related to diabetic macular edema retrieved from the Web of Science Core Collection (WoSCC) between its inception and September 4, 2023, was conducted. Microsoft Excel, CiteSpace, VOSviewer, Bibliometrix Package, and Tableau were used for the bibliometric analysis and visualization. This encompasses an examination of the overall distribution of annual output, major countries, regions, institutions, authors, core journals, co-cited references, and keyword analyses.

RESULTS

Overall, 5624 publications were analyzed, indicating an increasing trend in DME research. The United States was identified as the leading country in DME research, with the highest h-index of 135 and 91,841 citations. Francesco Bandello emerged as the most prolific author with 97 publications. Neil M. Bressler has the highest h-index and highest total citation count of 46 and 9692, respectively. The journals "Retina - the Journal of Retinal and Vitreous Diseases" and "Ophthalmology" were highlighted as the most prominent in this field. "Retina" leads with 354 publications, a citation count of 11,872, and an h-index of 59. Meanwhile, "Ophthalmology" stands out with the highest overall citation count of 31,558 and the highest h-index of 90. The primary research focal points in diabetic macular edema included "prevalence and risk factors," "pathological mechanisms," "imaging modalities," "treatment strategies," and "clinical trials." Emerging research areas encompassed "deep learning and artificial intelligence," "novel treatment modalities," and "biomarkers."

CONCLUSION

Our bibliometric analysis delineates the leading role of the United States in DME research. We identified current research hotspots, including epidemiological studies, pathophysiological mechanisms, imaging advancements, and treatment innovations. Emerging trends, such as the integration of artificial intelligence and novel therapeutic approaches, highlight future directions. These insights underscore the importance of collaborative and interdisciplinary approaches in advancing DME research and clinical management.

Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/β-catenin signaling

Interactions among neuronal, glial, and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Although synaptic dysfunction precedes vascular abnormalities in many retinal pathologies, how neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA sequencing (scRNA-seq), and functional validation, we show that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1-/- retinas where neurons fail to release glutamate. By contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1-/- retinas, where constitutively depolarized rods release excessive glutamate. Norrin expression and endothelial Norrin/β-catenin signaling are downregulated in Vglut1-/- retinas and upregulated in Gnat1-/- retinas. Pharmacological activation of endothelial Norrin/β-catenin signaling in Vglut1-/- retinas rescues defects in deep plexus angiogenesis and paracellular BRB maturation. Our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating endothelial Norrin/β-catenin signaling.

The Association of Systemic Endothelial Dysfunction With Diffuse Diabetic Macular Edema

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

Clinical Pharmacology Perspective on Development of Adeno-Associated Virus Vector-Based Retina Gene Therapy

Adeno-associated virus (AAV) vector-based gene therapy is an innovative modality being increasingly investigated to treat diseases by modifying or replacing defective genes or expressing therapeutic entities. With its unique anatomic and physiological characteristics, the eye constitutes a very attractive target for gene therapy. Specifically, the ocular space is easily accessible and is generally considered "immune-privileged" with a low risk of systemic side effects following local drug administration. As retina cells have limited cellular turnover, a one-time gene delivery has the potential to provide long-term transgene expression. Despite the initial success with voretigene neparvovec (Luxturna), the first approved retina gene therapy, there are still challenges to be overcome for successful clinical development of these products and scientific questions to be answered. The current review paper aims to integrate published experience learned thus far for AAV-based retina gene therapy related to preclinical to clinical translation; first-in-human dose selection; relevant bioanalytical assays and strategies; clinical development considerations including trial design, biodistribution and vector shedding, immunogenicity, transgene expression, and pediatric populations; opportunities for model-informed drug development; and regulatory perspectives. The information presented herein is intended to serve as a guide to inform the clinical development strategy for retina gene therapy with a focus on clinical pharmacology.

The structure and function of the human choroid

In this manuscript, the structure of the human choroid is reviewed with emphasis of the macro- and microscopic anatomy including Bruch's membrane, choriocapillaris, Sattler's and Haller's layer, and the suprachoroid. We here discuss the development of the choroid, as well as the question of choroidal lymphatics, and further the neuronal control of this tissue, as well as the pathologic angiogenesis. Wherever possible, functional aspects of the various structures are included and reviewed.

Pericyte in retinal vascular diseases: A multifunctional regulator and potential therapeutic target

Retinal vascular diseases (RVDs), in particular diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity, are leading contributors to blindness. The pathogenesis of RVD involves vessel dilatation, leakage, and occlusion; however, the specific underlying mechanisms remain unclear. Recent findings have indicated that pericytes (PCs), as critical members of the vascular mural cells, significantly contribute to the progression of RVDs, including detachment from microvessels, alteration of contractile and secretory properties, and excessive production of the extracellular matrix. Moreover, PCs are believed to have mesenchymal stem properties and, therefore, might contribute to regenerative therapy. Here, we review novel ideas concerning PC characteristics and functions in RVDs and discuss potential therapeutic strategies based on PCs, including the targeting of pathological signals and cell-based regenerative treatments.

Effect of High-Sucrose Diet on the Occurrence and Progression of Diabetic Retinopathy and Dietary Modification Strategies

As the most serious of the many worse new pathological changes caused by diabetes, there are many risk factors for the occurrence and development of diabetic retinopathy (DR). They mainly include hyperglycemia, hypertension, hyperlipidemia and so on. Among them, hyperglycemia is the most critical cause, and plays a vital role in the pathological changes of DR. High-sucrose diets (HSDs) lead to elevated blood glucose levels in vivo, which, through oxidative stress, inflammation, the production of advanced glycation end products (AGEs) and vascular endothelial growth factor (VEGF), cause plenty of pathological damages to the retina and ultimately bring about loss of vision. The existing therapies for DR primarily target the terminal stage of the disease, when irreversible visual impairment has appeared. Therefore, early prevention is particularly critical. The early prevention of DR-related vision loss requires adjustments to dietary habits, mainly by reducing sugar intake. This article primarily discusses the risk factors, pathophysiological processes and molecular mechanisms associated with the development of DR caused by HSDs. It aims to raise awareness of the crucial role of diet in the occurrence and progression of DR, promote timely changes in dietary habits, prevent vision loss and improve the quality of life. The aim is to make people aware of the importance of diet in the occurrence and progression of DR. According to the dietary modification strategies that we give, patients can change their poor eating habits in a timely manner to avoid theoretically avoidable retinopathy and obtain an excellent prognosis.

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.

Incidence and risk factors of age-related macular degeneration in patients with Parkinson's disease: a population-based study

Background and objective

The association between age-related macular degeneration (AMD) and Parkinson' disease (PD) remains unclear. The aim of the present study was to assess the incidence of AMD in patients with PD, elucidate differences by age and sex, and investigate potential risk factors for AMD.

Methods

Data were extracted from the Korean National Health Insurance System database, which covers 97% of the Korean population (2002 through 2019). We calculated the incidence of newly diagnosed AMD in patients with PD and used Cox proportional-hazards models to estimate risk factors for AMD, presenting adjusted hazard ratios (aHR) with 95% confidence intervals (CI).

Results

Of 172,726 patients with PD, 15,800 were newly diagnosed with AMD during the follow-up, including 5,624 men and 10,176 women. The overall incidence of AMD in patients with PD was 13.59 per 1,000 person-years. Stratified by age group and sex, the incidence was higher in women aged 40-69, and conversely higher in men aged 70-89. Risk of AMD was high in older age groups (aHR = 4.36, 95% CI: 3.74-5.09 in the 70 s), female sex (aHR = 1.07, 95% CI: 1.04-1.11), patients with diabetes mellitus (DM) (aHR = 1.14, 95% CI: 1.10-1.18), and patients with hyperlipidemia (aHR = 1.17, 95% CI: 1.13-1.21).

Conclusion

Our findings suggest that the AMD incidence is higher in patients with PD than in the general population, with varying patterns of sex differences across age groups. Particularly, old age, female sex, presence of DM, and hyperlipidemia are potential risk factors. Therefore, clinicians should pay greater attention to AMD in patients with PD.

Optical coherence tomography biomarkers indicating visual enhancement in diabetic macular edema resolved through anti-VEGF therapy: OCT biomarkers in resolved DME

PURPOSE

to investigate the structural features and extended visual results in eyes affected by diabetic retinopathy (DR) and diabetic macular edema (DME) that have been successfully treated with anti-vascular endothelial growth factor (VEGF) therapy.

METHODS

Individuals (39 eyes of 39 patients) who had undergone long-term follow-up and demonstrated evidence of resolved DME after at least 2 years of follow-up following the initiation of anti-VEGF therapy were included. During the ""study visit"", structural OCT scans were examined to assess qualitative features indicative of neuroretina or retinal pigment epithelium distress. Additionally, a quantitative assessment of the inner and outer retinal thicknesses was conducted for topographical analysis.

RESULTS

The most robust qualitative association observed with BCVA at the "study visit" was linked to the presence of DRIL (p = 0.043) and the appearance of the ELM. (p = 0.045). Regarding quantitative parameters, a strong correlation was noted between the visual acuity during the "study visit" and the foveal and parafoveal thicknesses of both the inner and outer retina (p < 0.001).

CONCLUSIONS

Changes in the status of ELM, the presence of DRIL, and the thicknesses of the foveal and parafoveal regions can act as OCT biomarkers, signifying prolonged visual improvements in eyes that have experienced resolved DME after undergoing anti-VEGF therapy.

Maculopathy in a 52-Year-Old Patient With Diabetes

A 52-year-old woman with severe nonproliferative diabetic retinopathy had decreased vision and macular edema in both eyes that was not responding to treatment. What would you do next?

Bibliometric and visualized analysis of DME from 2012 to 2022

BACKGROUND

Diabetic macular edema (DME) is the main cause of irreversible vision loss in patients with diabetes mellitus (DM), resulting in a certain burden to patients and society. With the increasing incidence of DME, more and more researchers are focusing on it.

METHODS

The papers related to DME between 2012 and 2022 from the Web of Science core Collection were searched in this study. Based on CiteSpace and VOS viewer, these publications were analyzed in terms of spatiotemporal distribution, author distribution, subject classification, topic distribution, and citations.

RESULTS

A total of 5165 publications on DME were included. The results showed that the research on DME is on a steady growth trend. The country with the highest number of published documents was the US. Wong Tien Yin from Tsinghua University was the author with the most published articles. The journal of Retina, the Journal of Retinal and Vitreous Diseases had a large number of publications. The article "Mechanisms of macular edema: Beyond the surface" was the highly cited literature and "Aflibercept, bevacizumab, or ranibizumab for diabetic macular edema" had the highest co-citation frequency. The treatment, diagnosis, pathogenesis, as well as etiology and epidemiological investigation of DME, have been the current research direction. Deep learning has been widely used in the medical field for its strong feature representation ability.

CONCLUSIONS

The study revealed the important authoritative literature, journals, institutions, scholars, countries, research hotspots, and development trends in in the field of DME. This indicates that communication and cooperation between disciplines, universities, and countries are crucial. It can advance research in DME and even ophthalmology.

Comparing the efficacy of glucocorticoids and anti-VEGF in treating diabetic macular edema: systematic review and comprehensive analysis

Introduction

The aim of this study was to better understand the efficacy of various drugs, such as glucocorticoids and anti-vascular endothelial growth factors (VEGF), in the treatment of diabetic macular edema (DME), and to evaluate various clinical treatment regimens consisting of different therapeutic measures.

Methods

This study included randomized controlled trials up to February 2023 comparing the efficacy of corticosteroid-related therapy and anti-VEGF therapy. PubMed, the Cochrane Library, and Embase were searched, and the quality of the studies was carefully assessed. Finally, 39 studies were included.

Results

Results at 3-month followup showed that intravitreal injection of bevacizumab (IVB) + triamcinolone acetonide (TA) was the most beneficial in improving best-corrected visual acuity and reducing the thickness of macular edema in the center of the retina in patients with DME. Results at 6-month follow-up showed that intravitreal dexamethasone (DEX) was the most effective in improving patients' bestcorrected visual acuity and reducing the thickness of central macular edema.

Discussion

Overall, IVB+TA was beneficial in improving best-corrected visual acuity and reducing central macular edema thickness over a 3-month follow-up period, while DEX implants had a better therapeutic effect than anti-VEGF agents at 6 months, especially the patients with severe macular edema and visual acuity impaired.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=397100, identifier CRD42023397100.

Glucose transport, transporters and metabolism in diabetic retinopathy

Diabetic retinopathy (DR) is the most common reason for blindness in working-age individuals globally. Prolonged high blood glucose is a main causative factor for DR development, and glucose transport is prerequisite for the disturbances in DR caused by hyperglycemia. Glucose transport is mediated by its transporters, including the facilitated transporters (glucose transporter, GLUTs), the "active" glucose transporters (sodium-dependent glucose transporters, SGLTs), and the SLC50 family of uniporters (sugars will eventually be exported transporters, SWEETs). Glucose transport across the blood-retinal barrier (BRB) is crucial for nourishing the neuronal retina in the context of retinal physiology. This physiological process primarily relies on GLUTs and SGLTs, which mediate the glucose transportation across both the cell membrane of retinal capillary endothelial cells and the retinal pigment epithelium (RPE). Under diabetic conditions, increased accumulation of extracellular glucose enhances the retinal cellular glucose uptake and metabolism via both glycolysis and glycolytic side branches, which activates several biochemical pathways, including the protein kinase C (PKC), advanced glycation end-products (AGEs), polyol pathway and hexosamine biosynthetic pathway (HBP). These activated biochemical pathways further increase the production of reactive oxygen species (ROS), leading to oxidative stress and activation of Poly (ADP-ribose) polymerase (PARP). The activated PARP further affects all the cellular components in the retina, and finally resulting in microangiopathy, neurodegeneration and low-to-moderate grade inflammation in DR. This review aims to discuss the changes of glucose transport, glucose transporters, as well as its metabolism in DR, which influences the retinal neurovascular unit (NVU) and implies the possible therapeutic strategies for treating DR.

The Treatment of Diabetic Retinal Edema with Intravitreal Steroids: How and When

Diabetic macular edema (DME) is a common complication of diabetes mellitus and a leading cause of visual impairment worldwide. It is defined as the diabetes-related accumulation of fluid, proteins, and lipids, with retinal thickening, within the macular area. DME affects a significant proportion of individuals with diabetes, with the prevalence increasing with disease duration and severity. It is estimated that approximately 25-30% of diabetic patients will develop DME during their lifetime. Poor glycemic control, hypertension, hyperlipidemia, diabetes duration, and genetic predisposition are recognized as risk factors for the development and progression of DME. Although the exact pathophysiology is still not completely understood, it has been demonstrated that chronic hyperglycemia triggers a cascade of biochemical processes, including increased oxidative stress, inflammation, activation of vascular endothelial growth factor (VEGF), cellular dysfunction, and apoptosis, with breakdown of the blood-retinal barriers and fluid accumulation within the macular area. Early diagnosis and appropriate management of DME are crucial for improving visual outcomes. Although the control of systemic risk factors still remains the most important strategy in DME treatment, intravitreal pharmacotherapy with anti-VEGF molecules or steroids is currently considered the first-line approach in DME patients, whereas macular laser photocoagulation and pars plana vitrectomy may be useful in selected cases. Available intravitreal steroids, including triamcinolone acetonide injections and dexamethasone and fluocinolone acetonide implants, exert their therapeutic effect by reducing inflammation, inhibiting VEGF expression, stabilizing the blood-retinal barrier and thus reducing vascular permeability. They have been demonstrated to be effective in reducing macular edema and improving visual outcomes in DME patients but are associated with a high risk of intraocular pressure elevation and cataract development, so their use requires an accurate patient selection. This manuscript aims to provide a comprehensive overview of the pathology, epidemiology, risk factors, physiopathology, clinical features, treatment mechanisms of actions, treatment options, prognosis, and ongoing clinical studies related to the treatment of DME, with particular consideration of intravitreal steroids therapy.

Modeling early pathophysiological phenotypes of diabetic retinopathy in a human inner blood-retinal barrier-on-a-chip

Diabetic retinopathy (DR) is a microvascular disorder characterized by inner blood-retinal barrier (iBRB) breakdown and irreversible vision loss. While the symptoms of DR are known, disease mechanisms including basement membrane thickening, pericyte dropout and capillary damage remain poorly understood and interventions to repair diseased iBRB microvascular networks have not been developed. In addition, current approaches using animal models and in vitro systems lack translatability and predictivity to finding new target pathways. Here, we develop a diabetic iBRB-on-a-chip that produces pathophysiological phenotypes and disease pathways in vitro that are representative of clinical diagnoses. We show that diabetic stimulation of the iBRB-on-a-chip mirrors DR features, including pericyte loss, vascular regression, ghost vessels, and production of pro-inflammatory factors. We also report transcriptomic data from diabetic iBRB microvascular networks that may reveal drug targets, and examine pericyte-endothelial cell stabilizing strategies. In summary, our model recapitulates key features of disease, and may inform future therapies for DR.

How the immune response to the structural proteins of SARS-CoV-2 affects the retinal vascular endothelial cells: an immune thrombotic and/or endotheliopathy process with in silico modeling

Thrombotic events associated with SARS-CoV-2 at the vascular endothelium still remains unclear. The aim of the current study is to determine the relationship between cellular proteins on the (ocular) vascular endothelial surface and the immune thrombotic and/or endotheliopathy process elicited by SARS-CoV-2 using an in-silico modeling. The structural S (spike glycoprotein), N (nucleocapsid protein), M (membrane protein), and E (envelope protein) proteins, an accessory protein (ORF1ab) of SARS-CoV-2 and 158 cellular proteins associated with retinal vascular endothelial cell surface or structure were included in this study for comparison of three-dimensional (3D) structure and sequence. Sixty-nine of the retinal proteins were obtained from the Uniprot database. Remaining proteins not included in the database were included in the study after they were converted into 3D structures using the RaptorX web tool. Sequence and three-dimensional structure of SARS-COV-2 S, N, M, E, ORF1ab proteins and retinal vascular endothelial proteins were compared with mTM-align server. Proteins with significant similarity (score above 0.5) were validated with the TM-align web server. Immune and thrombosis-related protein-receptor interactions of similar proteins was checked with CABS-dock. We detected a high level of structural similarity between E protein and ACE, ACE2, LAT1, and TM9SF4 endothelial proteins. In addition, PECAM-1 was found to be structurally similar to ORF1ab and S protein. When we evaluated the likelihood/potential to stimulate an immune responses/a cytokine release, TLR-2 and TLR-3, which are highly susceptible to SARS-CoV2, showed a potential receptor-protein interaction with retinal vascular endothelial proteins. Our study demonstrates that SARS-CoV-2 proteins may have structural similarities with vascular endothelial proteins, and therefore, as immunological target sites, the counterpart proteins on the endothelial surface of many organs may also be secondarily affected by any immune response against SARS-CoV-2 structural proteins.

Proteomic analysis of aqueous humor reveals novel regulators of diabetic macular edema

Diabetic macular edema (DME) is the most common cause of blindness in patients with diabetic retinopathy. To investigate the proteomic profiles of the aqueous humor (AH) of individuals with diabetic macular edema (DME), AH samples were collected from patients with non-diabetes mellitus (NDM), DM, nonproliferative diabetic retinopathy (NPDR), and DME. We performed comparative proteomic analyses using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and bioinformatics analyses. We identified 425 proteins in these AH samples, of which 113 showed changes in expression in DME compared with NDM, 95 showed changes in expression in DME vs. DM, and 84 showed changes in expression in DME compared with NPDR. The bioinformatics analysis suggested that DME is closely associated with platelet degranulation, oxidative stress-related pathway, and vascular-related pathways. Upregulation of haptoglobin (HP) and downregulation of fibrillin 1 (FBN1) were validated by ELISA. Receiver operating characteristic (ROC) analysis showed that HP and FBN1 could distinguish DME from NPDR with areas under the curve of 0.987 (p = 0.00608) and 0.791 (p = 0.00629), respectively. The findings provide potential clues for further analysis of the molecular mechanisms and the development of new treatments for DME. HP and FBN1 may be potential key proteins and therapeutic targets in human DME. The proteomics dataset generated has been deposited to the ProteomeXchange/iProX Consortium with Identifier: PXD033404/IPX0004353001.

The supplementation of a high dose of fish oil during pregnancy and lactation led to an elevation in Mfsd2a expression without any changes in docosahexaenoic acid levels in the retina of healthy 2-month-old mouse offspring

Introduction

During fetal development, the proper development of neural and visual systems relies on the maternal supplementation of omega-3 fatty acids through placental transfer. Pregnant women are strongly advised to augment their diet with additional sources of omega-3, such as fish oil (FO). This supplementation has been linked to a reduced risk of preterm birth, pre-eclampsia, and perinatal depression. Recently, higher doses of omega-3 supplementation have been recommended for pregnant women. Considering that omega-3 fatty acids, particularly docosahexaenoic acid (DHA), play a crucial role in maintaining the delicate homeostasis required for the proper functioning of the retina and photoreceptors the effects of high-dose fish oil (FO) supplementation during pregnancy and lactation on the retina and retinal pigmented epithelium (RPE) in healthy offspring warrant better understanding.

Methods

The fatty acid content and the changes in the expression of the genes regulating cholesterol homeostasis and DHA transport in the retina and RPE were evaluated following the high-dose FO supplementation.

Results

Our study demonstrated that despite the high-dose FO treatment during pregnancy and lactation, the rigorous DHA homeostasis in the retina and RPE of the two-month-old offspring remained balanced. Another significant finding of this study is the increase in the expression levels of major facilitator superfamily domain-containing protein (Mfsd2a), a primary DHA transporter. Mfsd2a also serves as a major regulator of transcytosis during development, and a reduction in Mfsd2a levels poses a major risk for the development of leaky blood vessels.

Conclusion

Impairment of the blood-retinal barrier (BRB) is associated with the development of numerous ocular diseases, and a better understanding of how to manipulate transcytosis in the BRB during development can enhance drug delivery through the BRB or contribute to the repair of central nervous system (CNS) barriers.

Glutamatergic neuronal activity regulates angiogenesis and blood-retinal barrier maturation via Norrin/β-catenin signaling

Interactions among neuronal, glial and vascular components are crucial for retinal angiogenesis and blood-retinal barrier (BRB) maturation. Although synaptic dysfunction precedes vascular abnormalities in many retinal pathologies, how neuronal activity, specifically glutamatergic activity, regulates retinal angiogenesis and BRB maturation remains unclear. Using in vivo genetic studies in mice, single-cell RNA-sequencing and functional validation, we show that deep plexus angiogenesis and paracellular BRB maturation are delayed in Vglut1 -/- retinas where neurons fail to release glutamate. In contrast, deep plexus angiogenesis and paracellular BRB maturation are accelerated in Gnat1 -/- retinas where constitutively depolarized rods release excessive glutamate. Norrin expression and endothelial Norrin/β-catenin signaling are downregulated in Vglut1 -/- retinas, and upregulated in Gnat1 -/- retinas. Pharmacological activation of endothelial Norrin/β-catenin signaling in Vglut1 -/- retinas rescued defects in deep plexus angiogenesis and paracellular BRB maturation. Our findings demonstrate that glutamatergic neuronal activity regulates retinal angiogenesis and BRB maturation by modulating endothelial Norrin/β-catenin signaling.

Relationship between Biochemical Pathways and Non-Coding RNAs Involved in the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is a progressive blinding disease, which affects the vision and quality of life of patients, and it severely impacts the society. This complication, caused by abnormal glucose metabolism, leads to structural, functional, molecular, and biochemical abnormalities in the retina. Oxidative stress and inflammation also play pivotal roles in the pathogenic process of DR, leading to mitochondrial damage and a decrease in mitochondrial function. DR causes retinal degeneration in glial and neural cells, while the disappearance of pericytes in retinal blood vessels leads to alterations in vascular regulation and stability. Clinical changes include dilatation and blood flow changes in response to the decrease in retinal perfusion in retinal blood vessels, leading to vascular leakage, neovascularization, and neurodegeneration. The loss of vascular cells in the retina results in capillary occlusion and ischemia. Thus, DR is a highly complex disease with various biological factors, which contribute to its pathogenesis. The interplay between biochemical pathways and non-coding RNAs (ncRNAs) is essential for understanding the development and progression of DR. Abnormal expression of ncRNAs has been confirmed to promote the development of DR, suggesting that ncRNAs such as miRNAs, lncRNAs, and circRNAs have potential as diagnostic biomarkers and theranostic targets in DR. This review provides an overview of the interactions between abnormal biochemical pathways and dysregulated expression of ncRNAs under the influence of hyperglycemic environment in DR.

Acrizanib as a Novel Therapeutic Agent for Fundus Neovascularization via Inhibitory Phosphorylation of VEGFR2

Purpose

The present study aimed to evaluate the effect of acrizanib, a small molecule inhibitor targeting vascular endothelial growth factor receptor 2 (VEGFR2), on physiological angiogenesis and pathological neovascularization in the eye and to explore the underlying molecular mechanisms.

Methods

We investigated the potential role of acrizanib in physiological angiogenesis using C57BL/6J newborn mice, and pathological angiogenesis using the mouse oxygen-induced retinopathy (OIR) and laser-induced choroidal neovascularization (CNV) models. Moreover, vascular endothelial growth factor (VEGF)-treated human umbilical vein endothelial cells (HUVECs) were used as an in vitro model for studying the molecular mechanism underlying acrizanib's antiangiogenic effects.

Results

The intravitreal injection of acrizanib did not show a considerable impact on physiological angiogenesis and retinal thickness, indicating a potentially favorable safety profile. In the mouse models of OIR and CNV, acrizanib showed promising results in reducing pathological neovascularization, inflammation, and vascular leakage, indicating its potential efficacy against pathological angiogenesis. Consistent with in vivo results, acrizanib blunted angiogenic events in VEGF-treated HUVECs such as proliferation, migration, and tube formation. Furthermore, acrizanib inhibited the multisite phosphorylation of VEGFR2 to varying degrees and the activation of its downstream signal pathways in VEGF-treated HUVECs.

Conclusions

This study suggested the potential efficacy and safety of acrizanib in suppressing fundus neovascularization. Acrizanib functioned through inhibiting multiple phosphorylation sites of VEGFR2 in endothelial cells to different degrees.

Translational Relevance

These results indicated that acrizanib might hold promise as a potential candidate for the treatment of ocular vascular diseases.