Mechanisms of leukocyte migration across the blood-retina barrier

Peptide-based hydrogel co-assembled with antibody-drug for enhanced retinal cell uptake and attenuated experimental autoimmune uveitis

Effective treatment of chronic posterior ocular diseases such as uveitis, diabetic retinopathy, and age-related macular degeneration requires improvements in targeted drug delivery strategies. This study introduces a novel injectable drug delivery system co-assembled with a peptide-based hydrogel and secukinumab (SEK), an IL-17A neutralising monoclonal antibody, targeting retinal pigmented epithelium (RPE) cells. Compared to a SEK solution, the SEK loaded hydrogel significantly enhanced the protein uptake (3.7 times higher) by RPE cells in an inflammatory state after 24 hours of treatment and increased the drug concentration in retinal tissues during 20 days of treatment. A single intravitreal injection of the SEK loaded hydrogel effectively suppressed inflammation in a uveitis model. It also reduced the immunoreactivity of microglia and T helper 17 cells, preserved the integrity of the blood-retina barrier, mitigated retinal cell apoptosis, and facilitated the recovery of the retinal function. This delivery system comprising an antibody-drug co-assembled with a peptide-based hydrogel shows promising potential for targeting the retina and treating complex chronic posterior ocular diseases.

Characterizing Bruch's membrane: State-of-the-art imaging, computational segmentation, and biologic models in retinal disease and health

The Bruch's membrane (BM) is an acellular, extracellular matrix that lies between the choroid and retinal pigment epithelium (RPE). The BM plays a critical role in retinal health, performing various functions including biomolecule diffusion and RPE support. The BM is also involved in many retinal diseases, and insights into BM dysfunction allow for further understanding of the pathophysiology of various chorioretinal pathologies. Thus, characterization of the BM serves as an important area of research to further understand its involvement in retinal disease. In this article, we provide a review of various advancements in characterizing and visualizing the BM. We provide an overview of the BM in retinal health, as well as changes observed in aging and disease. We then describe current state-of-the-art imaging modalities and advances to further visualize the BM including various types of optical coherence tomography imaging, near-infrared reflectance (NIR), and autofluorescence imaging and tissue matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS). Following advances in imaging of the BM, we describe animal, cellular, and synthetic models that have been developed to further visualize the BM. Following this section, we provide an overview of deep learning in retinal imaging and describe advances in computational and artificial intelligence (AI) techniques to provide automated segmentation of the BM and BM opening. We conclude this section considering the clinical implications of these segmentation techniques. Ultimately, the diverse advances aimed to further characterize the BM may allow for deeper insights into the involvement of this critical structure in retinal health and disease.

Palmitic acid exacerbates experimental autoimmune uveitis by activating T helper 17 cells via regulating STING signaling

Recent studies found that palmitic acid (PA), the most abundant fatty acid in human body, was increased in uveitis patients. However, its exact effect on uveitis has not been clarified. In this study, experimental autoimmune uveitis (EAU), an animal model of human uveitis, was successfully induced with interphotoreceptor retinoid-binding protein (IRBP) 651-670 and pertussis toxin. The immunized mice were treated with daily intragastric PA or vehicle from day 1-14. The results showed that PA could aggravate EAU activities and increase the proportion of T helper (Th) 17 cells as well as mRNA expression level of Il17a. There were no significant changes in Th1/Treg cell responses between these two groups. In vitro experiments showed that PA treatment could promote IRBP-specific Th17 cell response in association with increased proportion of Th17 cells as well as up-regulated expression of IL-17A. Proteomics showed an increased expression of stimulator of interferon genes protein (STING) in PA-treated mice as compared to vehicle-treated mice. H-151, a potent antagonist of STING, attenuated the activities of EAU and Th17 cell responses induced by PA. Moreover, NF-κB/IL-6 signaling pathway was found to be downregulated after H-151 treatment. Collectively, PA could exacerbate EAU severity possibly through the activation of Th17 cells mediated by up-regulating STING.

Photoreceptor loss does not recruit neutrophils despite strong microglial activation

In response to central nervous system (CNS) injury, tissue resident immune cells such as microglia and circulating systemic neutrophils are often first responders. The degree to which these cells interact in response to CNS damage is poorly understood, and even less so, in the neural retina which poses a challenge for high resolution imaging in vivo. In this study, we deploy fluorescence adaptive optics scanning light ophthalmoscopy (AOSLO) to study fluorescent microglia and neutrophils in mice. We simultaneously track immune cell dynamics using label-free phase-contrast AOSLO at micron-level resolution. Retinal lesions were induced with 488 nm light focused onto photoreceptor (PR) outer segments. These lesions focally ablated PRs, with minimal collateral damage to cells above and below the plane of focus. We used in vivo (AOSLO, SLO and OCT) imaging to reveal the natural history of the microglial and neutrophil response from minutes-to-months after injury. While microglia showed dynamic and progressive immune response with cells migrating into the injury locus within 1-day after injury, neutrophils were not recruited despite close proximity to vessels carrying neutrophils only microns away. Post-mortem confocal microscopy confirmed in vivo findings. This work illustrates that microglial activation does not recruit neutrophils in response to acute, focal loss of PRs, a condition encountered in many retinal diseases.

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.

The impact of circadian rhythms on retinal immunity

The eye is an immune-protected organ, which is driven by factors such as cytokines, chemicals, light, and mechanical stimuli. The circadian clock is an intrinsic timing mechanism that influences the immune activities, such as immune cell count and activity, as well as inflammatory responses. Recent studies have demonstrated that the eye also possesses an intrinsic circadian rhythm, and this rhythmic regulation participates in ocular immune modulation. In this review, we discuss the immunoregulatory mechanisms of the circadian clock within the eye, and reveal new perspectives for the prevention and treatment of ocular diseases.

Ketogenic diet modulates immune cell transcriptional landscape and ameliorates experimental autoimmune uveitis in mice

BACKGROUND

Uveitis manifests as immune-mediated inflammatory disorders within the eye, posing a serious threat to vision. The ketogenic diet (KD) has emerged as a promising dietary intervention, yet its impact on the immune microenvironments and role in uveitis remains unclear.

METHODS

Utilizing single-cell RNA sequencing (scRNA-seq) data from lymph node and retina of mice, we conduct a comprehensive investigation into the effects of KD on immune microenvironments. Flow cytometry is conducted to verify the potential mechanisms.

RESULTS

This study demonstrates that KD alters the composition and function of immune profiles. Specifically, KD promotes the differentiation of Treg cells and elevates its proportion in heathy mice. In response to experimental autoimmune uveitis challenges, KD alleviates the inflammatory symptoms, lowers CD4+ T cell pathogenicity, and corrects the Th17/Treg imbalance. Additionally, KD decreases the proportion of Th17 cell and increases Treg cells in the retina. Analysis of combined retinal and CDLN immune cells reveals that retinal immune cells, particularly CD4+ T cells, exhibit heightened inflammatory responses, which KD partially reverses.

CONCLUSIONS

The KD induces inhibitory structural and functional alterations in immune cells from lymph nodes to retina, suggesting its potential as a therapy for uveitis.

Chlorogenic acid ameliorates non-proliferative diabetic retinopathy via alleviating retinal inflammation through targeting TNFR1 in retinal endothelial cells

As a prominent complication of diabetes mellitus (DM) affecting microvasculature, diabetic retinopathy (DR) originates from blood-retinal barrier (BRB) damage. Natural polyphenolic compound chlorogenic acid (CGA) has already been reported to alleviate DR. This study delves into the concrete mechanism of the CGA-supplied protection against DR and elucidates its key target in retinal endothelial cells. DM in mice was induced using streptozotocin (STZ). CGA mitigated BRB dysfunction, leukocytes adhesion and the formation of acellular vessels in vivo. CGA suppressed retinal inflammation and the release of tumor necrosis factor-α (TNFα) by inhibiting nuclear factor kappa-B (NFκB). Furthermore, CGA reduced the TNFα-initiated adhesion of peripheral blood mononuclear cell (PBMC) to human retinal endothelial cell (HREC). CGA obviously decreased the TNFα-upregulated expression of vascular cell adhesion molecule-1 (VCAM1) and intercellular adhesion molecule-1 (ICAM1), and abrogated the TNFα-induced NFκB activation in HRECs. All these phenomena were reversed by overexpressing type 1 TNF receptor (TNFR1) in HRECs. The CGA-provided improvement on leukocytes adhesion and retinal inflammation was disappeared in mice injected with an endothelial-specific TNFR1 overexpression adeno-associated virus (AAV). CGA reduced the interaction between TNFα and TNFR1 through binding to TNFR1 in retinal endothelial cells. In summary, excepting reducing TNFα expression via inhibiting retinal inflammation, CGA also reduced the adhesion of leukocytes to retinal vessels through decreasing VCAM1 and ICAM1 expression via blocking the TNFα-initiated NFκB activation by targeting TNFR1 in retinal endothelial cells. All of those mitigated retinal inflammation, ultimately alleviating BRB breakdown in DR.

Exploring dysfunctional barrier phenotypes associated with glaucoma using a human pluripotent stem cell-based model of the neurovascular unit

Glaucoma is a neurodegenerative disease that results in the degeneration of retinal ganglion cells (RGCs) and subsequent loss of vision. While RGCs are the primary cell type affected in glaucoma, neighboring cell types selectively modulate RGCs to maintain overall homeostasis. Among these neighboring cell types, astrocytes, microvascular endothelial cells (MVECs), and pericytes coordinate with neurons to form the neurovascular unit that provides a physical barrier to limit the passage of toxic materials from the blood into neural tissue. Previous studies have demonstrated that these barrier properties may be compromised in the progression of glaucoma, yet mechanisms by which this happens have remained incompletely understood. Thus, the goals of this study were to adapt a human pluripotent stem cell (hPSC)-based model of the neurovascular unit to the study of barrier integrity relevant to glaucoma. To achieve this, hPSCs were differentiated into the cell types that contribute to this barrier, including RGCs, astrocytes, and MVECs, then assembled into an established Transwell®-insert model. The ability of these cell types to contribute to an in vitro barrier model was tested for their ability to recapitulate characteristic barrier properties. Results revealed that barrier properties of MVECs were enhanced when cultured in the presence of RGCs and astrocytes compared to MVECs cultured alone. Conversely, the versatility of this system to model aspects of barrier dysfunction relevant to glaucoma was tested using an hPSC line with a glaucoma-specific Optineurin (E50K) mutation as well as a paired isogenic control, where MVECs then exhibited reduced barrier integrity. To identify factors that could result in barrier dysfunction, results revealed an increased expression of TGFβ2 in glaucoma-associated OPTN(E50K) astrocytes, indicating a potential role for TGFβ2 in disease manifestation. To test this hypothesis, we explored the ability to modulate exogenous TGFβ2 in both isogenic control and OPTN(E50K) experimental conditions. Collectively, the results of this study indicated that the repurposing of this in vitro barrier model for glaucoma reliably mimicked some aspects of barrier dysfunction, and may serve as a platform for drug discovery, as well as a powerful in vitro model to test the consequences of barrier dysfunction upon RGCs in glaucoma.

Exposure to Silicone Oil Endotamponades Induces VEGF Antibody Aggregation and Loss of Functionality

Purpose

To investigate the interaction of a common monoclonal antibody (bevacizumab) with silicone oils and vitreous substitute hydrogels.

Methods

Protein content (spectrophotometry) and bioactivity (ELISA) of bevacizumab were assessed after direct contact to silicone oil and vitreous substitute hydrogels up to 24 hours. To detect antibody aggregation, particle size was determined by dynamic light scattering. Changes in secondary protein structure were assessed using circular dichroism. Experiments were translated to another antibody, trastuzumab, because its bioactivity can be additionally quantified by its binding to the membrane of HER2-positive cells.

Results

The functionality of bevacizumab gradually decreased during exposure to silicone oils with only 30% of activity remaining after 24 hours. Although circular dichroism did not reveal structural changes, the particle size increased drastically, indicating antibody aggregation for both antibodies. Exposure to silicone oil strongly reduced binding of trastuzumab to HER2-positive cells. The addition of polysorbate, a common stabilizer for antibody formulations, dose-dependently prevented aggregation, with 62% aggregation observed at 0.04% polysorbate compared to only 10% aggregation at 0.5% polysorbate. No aggregation occurred after exposure to vitreous body replacement hydrogels.

Conclusions

Contact to silicone oils induces a major loss of functionality of bevacizumab and trastuzumab. This limits clinical use during silicone oil tamponade. The beneficial effect of adding polysorbate suggests that loss of solubilizer is a likely cause of aggregation. Hydrogels, alternatives for vitreous body replacement, do not impair antibody functionality.

MENISCUS MICROPYON: An Ophthalmoscopic Sign Possibly Associated With Epiretinal Proliferation After Retinal Surgery With Gas Tamponade

PURPOSE

To describe an ophthalmoscopic sign, termed a meniscus micropyon, and its possible association with proliferative vitreoretinopathy/epiretinal membrane (ERM) formation after retinal surgery with gas tamponade.

METHODS

Patients with intravitreal gas were examined postoperatively by one of six vitreoretinal surgeons from four institutions. A micropyon was defined as a white-yellow, solid-appearing consolidation along the meniscus (i.e., the fluid-gas interface).

RESULTS

A micropyon was visualized and photographed in 49 patients who received intravitreal gas. Preoperatively, retinal breaks were present in all 49 eyes and rhegmatogenous retinal detachment in 45 (92%). Postoperatively, 39 eyes (80%) developed epiretinal proliferation: 16 eyes (33%) developed recurrent rhegmatogenous retinal detachment from proliferative vitreoretinopathy, 6 eyes (12%) re-detached without frank proliferative vitreoretinopathy, 9 eyes (18%) developed postoperative ERM/worsening, and 8 eyes (16%) had postoperative ERM but no preoperative optical coherence tomography to determine if the postoperative ERM was new or worsening. The single-operation anatomical success in eyes with a micropyon was 51%, which was lower than that of a contemporaneous rhegmatogenous retinal detachment control group (91%) in which no micropyon was detected. In two patients, micropyons were biopsied during pars plana vitrectomy and examined histopathologically; they consist predominantly of white blood cells.

CONCLUSION

The meniscus micropyon is an ophthalmoscopic sign that can occur after retinal surgery with gas tamponade. Features that distinguish a micropyon from postvitrectomy fibrin/fibrinoid syndrome include delayed appearance, hyperautofluorescence, absence of translucent strands or sheets in the anterior chamber or vitreous cavity, and the histopathologic identification of white blood cells. A clinically detectable micropyon may be a biomarker of proliferative vitreoretinopathy/ERM formation.

The gut-retina axis: Uncovering the role of autoimmunity in glaucoma development

Glaucoma, a leading cause of irreversible blindness worldwide, is characterized by progressive loss of retinal ganglion cells (RGCs) and optic nerve damage. While elevated intraocular pressure (IOP) is the only known modifiable risk factor, normal-tension glaucoma (NTG) challenges this notion, suggesting other mechanisms beyond IOP may contribute to its development. Emerging evidence support the hypothesis that glaucoma may be an autoimmune disease. This review summarizes evidence for this hypothesis, focusing on the gut-retina axis. We discuss how antigens of gut bacterial prime peripheral T cells to breach the blood-retina barrier (BRB) and initiate cross-reactivity with ocular tissues via molecular mimicry, resulting in autoimmune RGC damage. Understanding these mechanisms may uncover new diagnostic biomarkers and therapeutic strategies targeting immune pathways alongside conventional IOP-lowering treatments.

Inhibition of soluble epoxide hydrolase as a therapeutic approach for blood-brain barrier dysfunction

The blood-brain barrier (BBB) is a protective semi-permeable structure that regulates the exchange of biomolecules between the peripheral blood and the central nervous system (CNS). Due to its specialized tight junctions and low vesicle trafficking, the BBB strictly limits the paracellular passage and transcellular transport of molecules to maintain the physiological condition of brain tissues. BBB breakdown is associated with many CNS disorders. Soluble epoxide hydrolase (sEH) is a hydrolase enzyme that converts epoxy-fatty acids (EpFAs) to their corresponding diols and is involved in the onset and progression of multiple diseases. EpFAs play a protective role in the central nervous system via preventing neuroinflammation, making sEH a potential therapeutic target for CNS diseases. Recent studies showed that sEH inhibition prevented BBB impairment caused by stroke, hemorrhage, traumatic brain injury, hyperglycemia and sepsis via regulating the expression of tight junctions. In this review, the protective actions of sEH inhibition on BBB and potential mechanisms are summarized, and some important questions that remain to be resolved are also addressed.

Intravitreal therapeutic nanoparticles for age-related macular degeneration: Design principles, progress and opportunities

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly. The current standard treatment for AMD involves frequent intravitreal administrations of therapeutic agents. While effective, this approach presents challenges, including patient discomfort, inconvenience, and the risk of adverse complications. Nanoparticle-based intravitreal drug delivery platforms offer a promising solution to overcome these limitations. These platforms are engineered to target the retina specifically and control drug release, which enhances drug retention, improves drug concentration and bioavailability at the retinal site, and reduces the frequency of injections. This review aims to uncover the design principles guiding the development of highly effective nanoparticle-based intravitreal drug delivery platforms for AMD treatment. By gaining a deeper understanding of the physiology of ocular barriers and the physicochemical properties of nanoparticles, we establish a basis for designing intravitreal nanoparticles to optimize drug delivery and drug retention in the retina. Furthermore, we review recent nanoparticle-based intravitreal therapeutic strategies to highlight their potential in improving AMD treatment efficiency. Lastly, we address the challenges and opportunities in this field, providing insights into the future of nanoparticle-based drug delivery to improve therapeutic outcomes for AMD patients.

Risk Factors Associated with Cystoid Macular Edema among Patients Undergoing Primary Repair of Rhegmatogenous Retinal Detachment

PURPOSE

To investigate predictors of the development and resolution of cystoid macular edema (CME) after rhegmatogenous retinal detachment (RRD) repair.

DESIGN

Retrospective cross sectional study.

SUBJECTS

Patients who underwent primary repair of uncomplicated RRD.

METHODS

Demographics, ophthalmic history, visual acuity, RRD features, time to development/resolution of CME, OCT characteristics of CME/epiretinal membrane (ERM), type of surgery, and treatments were collected. Logistic regressions were used to identify predictors of CME development and resolution.

MAIN OUTCOME MEASURES

Predictors of CME development and resolution.

RESULTS

A total of 708 eyes were included, of which 55 (7.8%) developed CME. Factors associated with an increased risk of CME development included total number of retinal detachment surgeries (odds ratio [OR] 1.66 [1.24-2.23], P < 0.001), prior intraocular surgery (OR 4.43 [1.19-16.51], P = 0.03), and presence of ERM after surgery (OR 4.49 [2.30-8.74], P < 0.001). Patients undergoing pars plana vitrectomy (PPV) were more likely to develop CME compared with patients undergoing scleral buckling (SB; OR 3.09 [1.18-8.10], P = 0.02). A longer average time to CME detection was associated with lower CME resolution (OR 0.94 [0.89-0.998], P = 0.04). In patients who developed an ERM postsurgically, those who developed CME after ERM had a lower rate of resolution compared with those who developed CME before ERM (P = 0.03).

CONCLUSIONS

Cystoid macular edema may be more likely to develop in patients undergoing PPV than SB, those who underwent more surgeries for RRD repair, those who had prior intraocular surgery, or those who developed an ERM after RRD repair. Resolution of CME may be affected by the time to detection of CME and ERM development.

FINANCIAL DISCLOSURE(S)

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

Elevated tumor necrosis factor alpha and vascular endothelial growth factor in intermediate age-related macular degeneration and geographic atrophy

Introduction

Tumor necrosis factor alpha (TNF-α) is an inflammatory cytokine implicated in pathological changes to the retinal pigment epithelium that are similar to changes in geographic atrophy (GA), an advanced form of age related macular degeneration (AMD). TNF-α also modulates expression of other cytokines including vascular endothelial growth factor (VEGF), leading to choroidal atrophy in models of AMD. The purpose of this study was to investigate systemic TNF-α and VEGF in patients with GA and intermediate AMD (iAMD) compared to controls without AMD.

Methods

We examined plasma levels of TNF-α and VEGF in patients with GA, iAMD, and controls without AMD from the University of Colorado AMD registry (2014 to 2021). Cases and controls were characterized by multimodal imaging. TNF-α and VEGF were measured via multiplex immunoassay and data were analyzed using a non-parametric rank based linear regression model fit to plasma biomarkers.

Results

There were 97 GA, 199 iAMD patients and 139 controls. TNF-α was significantly increased in GA (Median:9.9pg/ml, IQR:7.3-11.8) compared to iAMD (Median:7.4, IQR:5.3-9.1) and in both GA and iAMD compared to controls (Median:6.4, IQR:5.3-7.8), p<0.01 for all comparisons. VEGF was significantly increased in iAMD (Median:8.9, IQR:4.8-14.3) compared to controls (Median:7.7, IQR:4.6-11.1), p<0.01. There was a significant positive correlation between TNF-α and VEGF in GA (0.46, p<0.01), and iAMD (0.20, p=0.01) with no significant interaction between TNF-α and VEGF in any group.

Discussion

These findings suggest TNF-α and VEGF may contribute to systemic inflammatory processes associated with iAMD and GA. TNF-α and VEGF may function as systemic biomarkers for disease development.

In a novel autoimmune and high-pressure glaucoma model a complex immune response is induced

Background

The neurodegenerative processes leading to glaucoma are complex. In addition to elevated intraocular pressure (IOP), an involvement of immunological mechanisms is most likely. In the new multifactorial glaucoma model, a combination of high IOP and optic nerve antigen (ONA) immunization leads to an enhanced loss of retinal ganglion cells accompanied by a higher number of microglia/macrophages in the inner retina. Here, we aimed to evaluate the immune response in this new model, especially the complement activation and the number of T-cells, for the first time. Further, the microglia/macrophage response was examined in more detail.

Methods

Six-week-old wildtype (WT+ONA) and βB1-connective tissue growth factor high-pressure mice (CTGF+ONA) were immunized with 1 mg ONA. A wildtype control (WT) and a CTGF group (CTGF) received NaCl instead. Six weeks after immunization, retinae from all four groups were processed for immunohistology, RT-qPCR, and flow cytometry, while serum was used for microarray analyses.

Results

We noticed elevated numbers of C1q+ cells (classical complement pathway) in CTGF and CTGF+ONA retinae as well as an upregulation of C1qa, C1qb, and C1qc mRNA levels in these groups. While the complement C3 was only increased in CTGF and CTGF+ONA retinae, enhanced numbers of the terminal membrane attack complex were noted in all three glaucoma groups. Flow cytometry and RT-qPCR analyses revealed an enhancement of different microglia/macrophages markers, including CD11b, especially in CTGF and CTGF+ONA retinae. Interestingly, increased retinal mRNA as well as serum levels of the tumor necrosis factor α were found throughout the different glaucoma groups. Lastly, more T-cells could be observed in the ganglion cell layer of the new CTGF+ONA model.

Conclusion

These results emphasize an involvement of the complement system, microglia/macrophages, and T-cells in glaucomatous disease. Moreover, in the new multifactorial glaucoma model, increased IOP in combination with autoimmune processes seem to enforce an additional T-cell response, leading to a more persistent pathology. Hence, this new model mimics the pathomechanisms occurring in human glaucoma more accurately and could therefore be a helpful tool to find new therapeutic approaches for patients in the future.

Mechanisms of blood-retinal barrier disruption related to intraocular inflammation and malignancy

Blood-retinal barrier (BRB) disruption is a common accompaniment of intermediate, posterior and panuveitis causing leakage into the retina and macular oedema resulting in vision loss. It is much less common in anterior uveitis or in patients with intraocular lymphoma who may have marked signs of intraocular inflammation. New drugs used for chemotherapy (cytarabine, immune checkpoint inhibitors, BRAF inhibitors, EGFR inhibitors, bispecific anti-EGFR inhibitors, MET receptor inhibitors and Bruton tyrosine kinase inhibitors) can also cause different types of uveitis and BRB disruption. As malignant disease itself can cause uveitis, particularly from breast, lung and gastrointestinal tract cancers, it can be clinically difficult to sort out the cause of BRB disruption. Immunosuppression due to malignant disease and/or chemotherapy can lead to infection which can also cause BRB disruption and intraocular infection. In this paper we address the pathophysiology of BRB disruption related to intraocular inflammation and malignancy, methods for estimating the extent and effect of the disruption and examine why some types of intraocular inflammation and malignancy cause BRB disruption and others do not. Understanding this may help sort and manage these patients, as well as devise future therapeutic approaches.

Th1 cells contribute to retinal ganglion cell loss in glaucoma in a VCAM-1-dependent manner

Glaucoma is a complex neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and optic nerve axons, leading to irreversible visual impairment. Despite its clinical significance, the underlying mechanisms of glaucoma pathogenesis remain poorly understood. In this study, we aimed to unravel the multifaceted nature of glaucoma by investigating the interaction between T cells and retinas. By utilizing clinical samples, murine glaucoma models, and T cell transfer models, we made several key findings. Firstly, we observed that CD4+ T cells from glaucoma patients displayed enhanced activation and a bias towards T helper (Th) 1 responses, which correlated with visual impairment. Secondly, we identified the infiltration of Th1 cells into the retina, where they targeted RGC and integrated into the pro-inflammatory glial network, contributing to progressive RGC loss. Thirdly, we discovered that circulating Th1 cells upregulated vascular cell adhesion protein 1 (VCAM-1) on retinal microvessels, facilitating their entry into the neural retina. Lastly, we found that Th1 cells underwent functional reprogramming before reaching the retina, acquiring a phenotype associated with lymphocyte migration and neurodegenerative diseases. Our study provides novel insights into the role of peripheral CD4+ T cells in glaucoma pathogenesis, shedding light on the mechanisms underlying their infiltration into the retina and offering potential avenues for innovative therapeutic interventions in this sight-threatening disease.

Differential Proteins Expression Distinguished Between Patients With Infectious and Noninfectious Uveitis

PURPOSE

We investigated the aqueous humor proteome and associated plasma proteome in patients with infectious or noninfectious uveitis.

METHODS

AH and plasma were obtained from 28 patients with infectious uveitis (IU), 29 patients with noninfectious uveitis (NIU) and 35 healthy controls undergoing cataract surgery. The proteins profile was analyzed by SomaScan technology.

RESULTS

We found 1844 and 2484 proteins up-regulated and 124 and 161 proteins down-regulated in the AH from IU and NIU groups, respectively. In the plasma, three proteins were up-regulated in NIU patients, and one and five proteins were down-regulated in the IU and NIU patients, respectively. The results of pathway enrichment analysis for both IU and NIU groups were related mostly to inflammatory and regulatory processes.

CONCLUSION

SomaScan was able to detect novel AH and plasma protein biomarkers in IU and NIU patients. Also, the unique proteins found in both AH and plasma suggest a protein signature that could distinguish between infectious and noninfectious uveitis.

Assessing the role of T cells in response to retinal injury to uncover new therapeutic targets for the treatment of retinal degeneration

BACKGROUND

Retinal degeneration is a disease affecting the eye, which is an immune-privileged site because of its anatomical and physiological properties. Alterations in retinal homeostasis-because of injury, disease, or aging-initiate inflammatory cascades, where peripheral leukocytes (PL) infiltrate the parenchyma, leading to retinal degeneration. So far, research on PL's role in retinal degeneration was limited to observing a few cell types at specific times or sectioning the tissue. This restricted our understanding of immune cell interactions and response duration.

METHODS

In vivo microscopy in preclinical mouse models can overcome these limitations enabling the spatio-temporal characterization of PL dynamics. Through in vivo imaging, we assessed structural and fluorescence changes in response to a focal injury at a defined location over time. We also utilized minimally invasive techniques, pharmacological interventions, and knockout (KO) mice to determine the role of PL in local inflammation. Furthermore, we investigated PL abundance and localization during retinal degeneration in human eyes by histological analysis to assess to which extent our preclinical study translates to human retinal degeneration.

RESULTS

We demonstrate that PL, especially T cells, play a detrimental role during retinal injury response. In mice, we observed the recruitment of helper and cytotoxic T cells in the parenchyma post-injury, and T cells also resided in the macula and peripheral retina in pathological conditions in humans. Additionally, we found that the pharmacological PL reduction and genetic depletion of T-cells reduced injured areas in murine retinas and rescued the blood-retina barrier (BRB) integrity. Both conditions promoted morphological changes of Cx3cr1+ cells, including microglial cells, toward an amoeboid phenotype during injury response. Interestingly, selective depletion of CD8+ T cells accelerated recovery of the BRB compared to broader depletions. After anti-CD8 treatment, the retinal function improved, concomitant to a beneficial immune response.

CONCLUSIONS

Our data provide novel insights into the adaptive immune response to retinal injury in mice and human retinal degeneration. Such information is fundamental to understanding retinal disorders and developing therapeutics to modulate immune responses to retinal degeneration safely.

Bergenin alleviates Diabetic Retinopathy in STZ-induced rats

Diabetic retinopathy (DR) is the key cause of blindness and visual impairment in diabetes patients around the world. The high levels of oxidative stress in diabetes patients cause diabetic retinopathy. In addition to being an antioxidant, Bergenin also works as an immunosuppressant, an anti-inflammatory, and anticarcinogenic against hepatocarcinoma. This study examined the effects of Bergenin on diabetic retinopathy rats, using Streptozotocin (STZ) intraperitoneally to induce diabetes in rats. The animals were divided into four groups (n = 6), including a normal control (Group I), diabetic control (Group II), Bergenin (25 mg/kg) (Group III), and metformin (350 mg/kg) (Group IV). As previously mentioned, each animal received treatment for 60 days. To induce DR, rats were administered STZ (60 mg/kg) intraperitoneally for 60 days. Standard methods were utilized to measure the body weight of rats, blood glucose levels. We measured lipid profiles (Triglycerides, cholesterol, LDL, and HDL), inflammatory markers, and antioxidant levels with their respective kits. Analysis of retinal tissue morphometry and MMP-9, VEGF, and MCP-1 levels in serum was performed. Our research examined the expression levels of target genes (TNF-α, IL-1β, and IL-6) using RT-PCR analysis. STZ-induced animals that were treated with Bergenin had less food intake, lower blood glucose, and improved body weight. Bergenin significantly suppressed levels of pro-inflammatory cytokines, cholesterol, TG, LDL, AI, MMP-9, VEGF, and MCP-1 and increased the level of HDL and antioxidant enzymes in STZ-induced DR rats. As well as increasing antioxidant levels, reducing retinal thickness, and increasing cell numbers, Bergenin also lessened DR remarkably. The results of this study demonstrated that Bergenin effectively inhibited STZ-induced DR in rats.

Endogenous and Exogenous Regulation of Redox Homeostasis in Retinal Pigment Epithelium Cells: An Updated Antioxidant Perspective

The retinal pigment epithelium (RPE) performs a range of necessary functions within the neural layers of the retina and helps ensure vision. The regulation of pro-oxidative and antioxidant processes is the basis for maintaining RPE homeostasis and preventing retinal degenerative processes. Long-term stable changes in the redox balance under the influence of endogenous or exogenous factors can lead to oxidative stress (OS) and the development of a number of retinal pathologies associated with RPE dysfunction, and can eventually lead to vision loss. Reparative autophagy, ubiquitin-proteasome utilization, the repair of damaged proteins, and the maintenance of their conformational structure are important interrelated mechanisms of the endogenous defense system that protects against oxidative damage. Antioxidant protection of RPE cells is realized as a result of the activity of specific transcription factors, a large group of enzymes, chaperone proteins, etc., which form many signaling pathways in the RPE and the retina. Here, we discuss the role of the key components of the antioxidant defense system (ADS) in the cellular response of the RPE against OS. Understanding the role and interactions of OS mediators and the components of the ADS contributes to the formation of ideas about the subtle mechanisms in the regulation of RPE cellular functions and prospects for experimental approaches to restore RPE functions.

Evaluation of Topical and Subconjunctival Injection of Hyaluronic Acid-Coated Nanoparticles for Drug Delivery to Posterior Eye

Posterior eye diseases, such as age-related macular degeneration and diabetic retinopathy, are difficult to treat due to ineffective drug delivery to affected areas. Intravitreal injection is the primary method for posterior eye drug delivery; however, it is usually accompanied by complications. Therefore, an effective and non-invasive method is required. Self-assembling nanoparticles (NPs) made from gelatin-epigallocatechin gallate (EGCG) were synthesized (GE) and surface-decorated with hyaluronic acid (HA) for drug delivery to the retinal/choroidal area. Different HA concentrations were used to prepare NPs with negative (GEH-) or positive (GEH+) surface charges. The size/zeta potential and morphology of the NPs were characterized by a dynamic light scattering (DLS) system and transmission electron microscope (TEM). The size/zeta potential of GEH+ NPs was 253.4 nm and 9.2 mV. The GEH- NPs were 390.0 nm and -35.9 mV, respectively. The cytotoxicity was tested by adult human retinal pigment epithelial cells (ARPE-19), with the results revealing that variant NPs were non-toxicity at 0.2-50 µg/mL of EGCG, and that the highest amount of GEH+ NPs was accumulated in cells examined by flowcytometry. Topical delivery (eye drops) and subconjunctival injection (SCI) methods were used to evaluate the efficiency of NP delivery to the posterior eyes in a mouse model. Whole eyeball cryosections were used to trace the location of fluorescent NPs in the eyes. The area of fluorescent signal obtained in the posterior eyes treated with GEH+ NPs in both methods (eye drops: 6.89% and SCI: 14.55%) was the greatest when compared with other groups, especially higher than free dye solution (2.79%). In summary, GEH+ NPs can be transported to the retina by eye drops and SCI; in particular, eye drops are a noninvasive method. Furthermore, GEH+ NPs, characterized by a positive surface and HA decoration, could facilitate drug delivery to the posterior eye as a useful drug carrier.

Single subcutaneous injection of the minocycline nanocomposite-loaded thermosensitive hydrogel for the effective attenuation of experimental autoimmune uveitis

Autoimmune uveitis induces a serious pathological and inflammatory response in the retina/choroid and results in vision impairment and blindness. Here, we report a minocycline (Mino) nanocomposite-loaded hydrogel offering a high drug payload and sustained drug release for the effective control of ocular inflammation via a single subcutaneous injection. In the presence of divalent cations (i.e., Ca²⁺), Mino was found to co-assemble with a phosphorylated peptide (i.e., NapGFFpY) via electrostatic interaction and consequently generating Mino nanocomposite. The drug entrapment efficiency (EE) of the Mino nanocomposite varied from 29.93±0.76% to 67.90±6.57%, depending on different component concentrations. After incorporation into 30 wt% poly (D,L-lactide)-b-poly (ethylene glycol)-b-poly (D,L-lactide) (PDLLA-PEG-PDLLA) thermosensitive hydrogel, the resulting Mino nanocomposite-loaded hydrogel provided a sustained drug release over 21 days. In the experimental autoimmune uveitis (EAU) rat model, a single subcutaneous injection of the Mino nanocomposite-loaded hydrogel effectively alleviated ocular inflammation in a dose-dependent manner. As indicated by optical coherence tomography (OCT) and electroretinogram (ERG) measurements, the Mino nanocomposite-loaded hydrogel treatment not only remarkably reduced destruction of the retina by EAU, but also greatly rescued retinal functions. Moreover, the proposed Mino nanocomposite-loaded hydrogel exerted its therapeutic effect on EAU primarily through a significant reduction of the influx of leukocytes and Th17 cells as well as suppression of microglia activation and apoptosis in the retina. Overall, the proposed Mino nanocomposite-loaded hydrogel might be a promising strategy for the clinical management of EAU.

Association between high immune activity and worse prognosis in uveal melanoma and low-grade glioma in TCGA transcriptomic data

BACKGROUND

Immune status in the tumor microenvironment is an important determinant of cancer progression and patient prognosis. Although a higher immune activity is often associated with a better prognosis, this trend is not absolute and differs across cancer types. We aimed to give insights into why some cancers do not show better survival despite higher immunity by assessing the relationship between different biological factors, including cytotoxicity, and patient prognosis in various cancer types using RNA-seq data collected by The Cancer Genome Atlas.

RESULTS

Results showed that a higher immune activity was associated with worse overall survival in patients with uveal melanoma and low-grade glioma, which are cancers of immune-privileged sites. In these cancers, epithelial or endothelial mesenchymal transition and inflammatory state as well as immune activation had a notable negative correlation with patient survival. Further analysis using additional single-cell data of uveal melanoma and glioma revealed that epithelial or endothelial mesenchymal transition was mainly induced in retinal pigment cells or endothelial cells that comprise the blood-retinal and blood-brain barriers, which are unique structures of the eye and central nervous system, respectively. Inflammation was mainly promoted by macrophages, and their infiltration increased significantly in response to immune activation. Furthermore, we found the expression of inflammatory chemokines, particularly CCL5, was strongly correlated with immune activity and associated with poor survival, particularly in these cancers, suggesting that these inflammatory mediators are potential molecular targets for therapeutics.

CONCLUSIONS

In uveal melanoma and low-grade glioma, inflammation from macrophages and epithelial or endothelial mesenchymal transition are particularly associated with a poor prognosis. This implies that they loosen the structures of the blood barrier and impair homeostasis and further recruit immune cells, which could result in a feedback loop of additional inflammatory effects leading to runaway conditions.

Role of Inner Ear Macrophages and Autoimmune/Autoinflammatory Mechanisms in the Pathophysiology of Inner Ear Disease

Macrophages play important roles in tissue homeostasis and inflammation. Recent studies have revealed that macrophages are dispersed in the inner ear and may play essential roles in eliciting an immune response. Autoinflammatory diseases comprise a family of immune-mediated diseases, some of which involve sensorineural hearing loss, indicating that similar mechanisms may underlie the pathogenesis of immune-mediated hearing loss. Autoimmune inner ear disease (AIED) is an idiopathic disorder characterized by unexpected hearing loss. Tissue macrophages in the inner ear represent a potential target for modulation of the local immune response in patients with AIED/autoinflammatory diseases. In this review, we describe the relationship between cochlear macrophages and the pathophysiology of AIED/autoinflammatory disease.

T Cell-Mediated Autoimmunity in Glaucoma Neurodegeneration

Glaucoma as the leading neurodegenerative disease leads to blindness in 3.6 million people aged 50 years and older worldwide. For many decades, glaucoma therapy has primarily focused on controlling intraocular pressure (IOP) and sound evidence supports its role in delaying the progress of retinal ganglial cell (RGC) damage and protecting patients from vision loss. Meanwhile, accumulating data point to the immune-mediated attack of the neural retina as the underlying pathological process behind glaucoma that may come independent of raised IOP. Recently, some scholars have suggested autoimmune aspects in glaucoma, with autoreactive T cells mediating the chief pathogenic process. This autoimmune process, as well as the pathological features of glaucoma, largely overlaps with other neurodegenerative diseases in the central nervous system (CNS), including Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis. In addition, immune modulation therapy, which is regarded as a potential solution for glaucoma, has been boosted in trials in some CNS neurodegenerative diseases. Thus, novel insights into the T cell-mediated immunity and treatment in CNS neurodegenerative diseases may serve as valuable inspirations for ophthalmologists. This review focuses on the role of T cell-mediated immunity in the pathogenesis of glaucoma and discusses potential applications of relevant findings of CNS neurodegenerative diseases in future glaucoma research.

Atopobiosis and Dysbiosis in Ocular Diseases: Is Fecal Microbiota Transplant and Probiotics a Promising Solution?

PURPOSE

To highlight the role of atopobiosis and dysbiosis in the pathomechanism of autoimmune uveitis, therefore supporting fecal microbiota transplant (FMT) and probiotics as potential targeted-treatment for uveitis.

METHODS

This review synthesized literatures upon the relation between gut microbiota, autoimmune uveitis, FMT, and probiotics, published from January 2001 to March 2021 and indexed in PubMed, Google Scholar, CrossRef.

RESULTS

The basis of the gut-eye axis revolves around occurrences of molecular mimicry, increase in pro-inflammatory cytokines, gut epithelial barrier disruption, and translocation of microbes to distant sites. In patients with autoimmune uveitis, an increase of gut Fusobacterium and Enterobacterium were found. With current knowledge of aforementioned mechanisms, studies modifying the gut microbiome and restoring the physiologic gut barrier has been the main focus for pathomechanism-based therapy. In mice models, FMT and probiotics targeting repopulation of gut microbiota has shown significant improvement in clinical manifestations of uveitis. Consequently, a better understanding in the homeostasis of gut microbiome along with their role in the gut-eye axis is needed to develop practical targeted treatment.

CONCLUSION

Current preliminary studies are promising in establishing a causative gut-eye axis relationship and the possibility of conducting FMT and probiotics as targeted treatment to mitigate autoimmune uveitis, to shorten disease duration, and to prevent further complications.

Characterizing the cellular immune response to subretinal AAV gene therapy in the murine retina

Although adeno-associated viral (AAV) vector-mediated retinal gene therapies have demonstrated efficacy, the mechanisms underlying dose-dependent retinal inflammation remain poorly understood. Here, we present a quantitative analysis of cellular immune response to subretinal AAV gene therapy in mice using multicolor flow cytometry with a panel of key immune cell markers. A significant increase in CD45+ retinal leukocytes was detected from day 14 post-subretinal injection of an AAV8 vector (1 × 109 genome copies) encoding green fluorescent protein (GFP) driven by a ubiquitous promoter. These predominantly consisted of infiltrating peripheral leukocytes including macrophages, natural killer cells, CD4 and CD8 T cells, and natural killer T cells; no significant change in resident microglia population was detected. This cellular response was persistent at 28 days and suggestive of type 1 cell-mediated effector immunity. High levels (80%) of GFP fluorescence were found in the microglia, implicating their role in viral antigen presentation and peripheral leukocyte recruitment. When compared against AAV.GFP in paired eyes, an equivalent dose of an otherwise identical vector encoding the human therapeutic transgene Rab-escort protein 1 (REP1) elicited a significantly diminished cellular immune response (4.2-fold; p = 0.0221). However, the distribution of immune cell populations remained similar, indicating a common mechanism of AAV-induced immune activation.

Attenuation of Experimental Autoimmune Uveitis in Lewis Rats by Betaine

Experimental autoimmune uveitis (EAU) is an animal model of human autoimmune uveitis that is characterized by the infiltration of autoimmune T cells with concurrent increases in pro-inflammatory cytokines and reactive oxygen species. This study aimed to assess whether betaine regulates the progression of EAU in Lewis rats. EAU was induced via immunization with the interphotoreceptor retinoid-binding protein (IRBP) and oral administration of either a vehicle or betaine (100 mg/kg) for 9 consecutive days. Spleens, blood, and retinas were sampled from the experimental rats at the time of sacrifice and used for the T cell proliferation assay, serological analysis, real-time polymerase chain reaction, and immunohistochemistry. The T cell proliferation assay revealed that betaine had little effect on the proliferation of splenic T cells against the IRBP antigen in an in vitro assay on day 9 post-immunization. The serological analysis showed that the level of serum superoxide dismutase increased in the betaine-treated group compared with that in the vehicle-treated group. The anti-inflammatory effect of betaine was confirmed by the downregulation of pro-inflammation-related molecules, including vascular cell adhesion molecule 1 and interleukin-1β in the retinas of rats with EAU. The histopathological findings agreed with those of ionized calcium-binding adaptor molecule 1 immunohistochemistry, further verifying that inflammation in the retina and ciliary bodies was significantly suppressed in the betaine-treated group compared with the vehicle-treated group. Results of the present study suggest that betaine is involved in mitigating EAU through anti-oxidation and anti-inflammatory activities.

The Chx10-Traf3 Knockout Mouse as a Viable Model to Study Neuronal Immune Regulation

Uncontrolled inflammation is associated with neurodegenerative conditions in central nervous system tissues, including the retina and brain. We previously found that the neural retina (NR) plays an important role in retinal immunity. Tumor necrosis factor Receptor-Associated Factor 3 (TRAF3) is a known immune regulator expressed in the retina; however, whether TRAF3 regulates retinal immunity is unknown. We have generated the first conditional NR-Traf3 knockout mouse model (Chx10-Cre/Traf3^f/f) to enable studies of neuronal TRAF3 function. Here, we evaluated NR-Traf3 depletion effects on whole retinal TRAF3 protein expression, visual acuity, and retinal structure and function. Additionally, to determine if NR-Traf3 plays a role in retinal immune regulation, we used flow cytometry to assess immune cell infiltration following acute local lipopolysaccharide (LPS) administration. Our results show that TRAF3 protein is highly expressed in the NR and establish that NR-Traf3 depletion does not affect basal retinal structure or function. Importantly, NR-Traf3 promoted LPS-stimulated retinal immune infiltration. Thus, our findings propose NR-Traf3 as a positive regulator of retinal immunity. Further, the NR-Traf3 mouse provides a tool for investigations of neuronal TRAF3 as a novel potential target for therapeutic interventions aimed at suppressing retinal inflammatory disease and may also inform treatment approaches for inflammatory neurodegenerative brain conditions.

Myeloid Cells in the Mouse Retina and Uveal Tract Respond Differently to Systemic Inflammatory Stimuli

Purpose

In spite of clear differences in tissue function and significance to ocular disease, little is known about how immune responses differ between the retina and uveal tract. To this end we compared the effects of acute systemic inflammation on myeloid cells within the mouse retina, iris-ciliary body, and choroid.

Methods

Systemic inflammation was induced in Cx3cr1gfp/gfp and CD11c-eYFP Crb1wt/wtmice by intraperitoneal lipopolysaccharide (LPS). In vivo fundus imaging was performed at two, 24, and 48 hours after LPS, and ocular tissue wholemounts were immunostained and studied by confocal microscopy. Flow cytometry was used to investigate the expression of activation markers (MHC class II, CD80, CD86) on myeloid cell populations at 24 hours. For functional studies, retinal microglia were isolated from LPS-exposed mice and cocultured with naïve OT-II CD4+ T-cells and ovalbumin peptide. T-cell proliferation was measured by flow cytometry and cytokine assays.

Results

Systemic LPS altered the density and morphology of retinal microglia; however, retinal microglia did not upregulate antigen presentation markers and failed to stimulate naïve CD4+ T-cell proliferation in vitro. In contrast, uveal tract myeloid cells displayed a phenotype consistent with late-activated antigen-presenting cells at 24 hours. Systemic LPS induced remodeling of myeloid populations within the uveal tract, particularly in the choroid, where dendritic cells were partially displaced by macrophages at 24 hours.

Conclusions

The disparate myeloid cell responses in the retina and uveal tract after systemic LPS highlight differential regulation of innate immunity within these tissue environments, observations that underpin and advance our understanding of ocular immune privilege.

Longitudinal Evaluation of Hyper-Reflective Foci in the Retina Following Subretinal Delivery of Adeno-Associated Virus in Non-Human Primates

Purpose

The purpose of this study was to evaluate whether clinical grade recombinant adeno-associated virus serotype 8 (rAAV8) leads to increased appearance of hyper-reflective foci (HRF) in the retina of non-human primates (NHPs) following subretinal gene therapy injection.

Methods

Different doses of rAAV8 vector (rAAV8. human phosphodiesterase 6A subunit (hPDE6A) at low dose: 1 × 1011 vector genomes (vg), medium dose: 5 × 1011 vg, or high dose: 1 × 1012 vg) were injected subretinally into the left eyes of NHPs in a formal toxicology study in preparation of a clinical trial. Right eyes received sham-injection. After 3 months of in vivo, follow-up retinal sections were obtained and analyzed. The number of HRF on spectral domain-optical coherence tomography (SD-OCT) volume scans were counted from both eyes at 30 and 90 days.

Results

Animals from the high-dose group showed more HRF than in the low (P = 0.03) and medium (P = 0.01) dose groups at 90 days. There was a significant increase in the mean number of HRF in rAAV8-treated eyes compared with sham-treated eyes at 90 days (P = 0.02). Sham-treated eyes demonstrated a nonsignificant reduction of HRF numbers over time. In contrast, a significant increase over time was observed in the rAAV8-treated eyes of the high dose group (P = 0.001). The presence of infiltrating B- and T-cells and microglia activation were detected in rAAV8-treated eyes.

Conclusions

Some HRF in the retina appear to be related to the surgical trauma of subretinal injection. Although HRF in sham-treated retina tends to become less frequent over time, they accumulate in the high-dose rAAV8-treated eyes. This may suggest a sustained immunogenicity when subretinal injections of higher doses of rAAV8 vectors are applied, but it has lower impact when using more clinically relevant doses (low and medium groups).

Translational Relevance

An increase or persistence of HRFs following retinal gene therapy may indicate the need for immunomodulatory treatment.

An interplay of microglia and matrix metalloproteinase MMP9 under hypoxic stress regulates the opticin expression in retina

Inflammation plays a key role in the pathogenesis of retinal vascular diseases. We have shown earlier an increase in the activity of matrix metalloproteinases in the vitreous and tears of preterm born babies with retinopathy of prematurity (ROP) compared to those with no-ROP leading to a shift in the balance of angiogenic (vascular endothelial growth factor [VEGF], matrix metalloproteinase [MMPs], complement component [C3]) and anti-angiogenic (opticin, thrombospondin) in ROP eyes. We now confirmed that tear MMP levels in premature infants perfectly correlates with disease severity. Next, we demonstrated that a reduced opticin levels in ROP vitreous are regulated by MMPs secreted by activated microglia. Upon exposing the human microglia cell line (CHME3) to hypoxia, an increased expression of inflammatory proteins (MMP9, VEGF) was noticed while opticin reduced significantly (p = 0.005). Further, the reduced opticin’s expression by microglial cells under hypoxia could be rescued by inhibiting the MMP activity using doxycycline and EDTA. The inhibition of MMP activity altered the expression of other key signaling molecules under hypoxia. Our study clearly explains that increased activity of MMPs under hypoxia regulates the expression of opticin as seen in the vitreous humor of ROP and could serve as a potential target for ROP management.

Small-molecule antagonist of VLA-4 (GW559090) attenuated neuro-inflammation by targeting Th17 cell trafficking across the blood-retinal barrier in experimental autoimmune uveitis

Background

The integrin VLA-4 (α4β1) plays an important role in leukocyte trafficking. This study investigated the efficacy of a novel topical α4β1 integrin inhibitor (GW559090, GW) in a mouse model for non-infectious posterior uveitis (experimental autoimmune uveitis; EAU) and its effect on intraocular leukocyte subsets.

Methods

Mice (female; B10.RIII or C57Bl/6; aged 6–8 weeks) were immunized with specific interphotoreceptor retinoid-binding protein (IRBP) peptides to induce EAU. Topically administered GW (3, 10, and 30 mg/ml) were given twice daily either therapeutically once disease was evident, or prophylactically, and compared with vehicle-treated (Veh) and 0.1% dexamethasone-treated (Dex) controls. Mice were sacrificed at peak disease. The retinal T cell subsets were investigated by immunohistochemistry and immunofluorescence staining. The immune cells within the retina, blood, and draining lymph nodes (dLNs) were phenotyped by flow cytometry. The effect of GW559090 on non-adherent, adherent, and migrated CD4⁺ T cell subsets across a central nervous system (CNS) endothelium was further assayed in vitro and quantitated by flow cytometry.

Results

There was a significant reduction in clinical and histological scores in GW₁₀- and Dex-treated groups as compared to controls either administered therapeutically or prophylactically. There were fewer CD45⁺ leukocytes infiltrating the retinae and vitreous fluids in the treated GW₁₀ group (P < 0.05). Immunofluorescence staining and flow cytometry data identified decreased levels of retinal Th17 cells (P ≤ 0.001) in the GW₁₀-treated eyes, leaving systemic T cell subsets unaffected. In addition, fewer Ly6C⁺ inflammatory monocyte/macrophages (P = 0.002) and dendritic cells (P = 0.017) crossed the BRB following GW₁₀ treatment. In vitro migration assays confirmed that Th17 cells were selectively suppressed by GW559090 in adhering to endothelial monolayers.

Conclusions

This α4β1 integrin inhibitor may exert a modulatory effect in EAU progression by selectively blocking Th17 cell migration across the blood-retinal barrier without affecting systemic CD4⁺ T cell subsets. Local α4β1 integrin-directed inhibition could be clinically relevant in treating a Th17-dominant form of uveitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02080-8.

Bleeding tendency and ascorbic acid requirements: systematic review and meta-analysis of clinical trials

CONTEXT

The World Health Organization set the recommended daily vitamin C intake, henceforth referred to as ascorbic acid (AA), on the basis of scurvy prevention. Double-blind AA depletion-repletion studies suggest that this recommended AA dose may be too low to prevent microvascular fragility.

OBJECTIVES

(1) To conduct a systematic review and meta-analysis of controlled clinical trials on whether AA supplementation leads to a reduced gingival bleeding tendency, a manifestation of microvascular fragility; and (2) to relate AA plasma levels to retinal hemorrhaging, another manifestation of microvascular fragility.

DATA SOURCES

Data were reviewed from 15 trials conducted in 6 countries with 1140 predominantly healthy participants with measures of gingival bleeding tendency, and from the National Health and Nutrition Examination Survey (NHANES) III of 8210 US residents with measures of retinal hemorrhaging.

RESULTS

In clinical trials, AA supplementation reduced gingival bleeding tendency when estimated baseline AA plasma levels were < 28 μmol/L (standardized mean difference [SMD], -0.83; 95%CI, -1.16 to -0.49; P < 0.002). Supplementation with AA did not unequivocally reduce gingival bleeding tendency when baseline estimated AA plasma levels were >48  μmol/L or unknown (respective standardized mean differences: -0.23, 95%CI, -0.45 to -0.01, P < 0.05; and -0.56; 95%CI: -1.19 to 0.06, P < 0.08). In NHANES III, prevalence of both retinal hemorrhaging and gingival bleeding tendency increased when AA plasma levels were within the range that protects against scurvy (11-28 μmol/L; respective prevalence ratios adjusted for age and sex: 1.47; 95%CI: 1.22-1.77; and 1.64; 95%CI: 1.32-2.03; P < 0.001 for both).

CONCLUSION

Consistent evidence from controlled clinical trials indicates that setting human AA requirements based on scurvy prevention leads to AA plasma levels that may be too low to prevent an increased gingival bleeding tendency. Gingival bleeding tendency and retinal hemorrhaging coincide with low AA plasma levels and thus may be reflective of a systemic microvascular pathology that is reversible with an increased daily AA intake.

The Impact of Oxidative Stress on Blood-Retinal Barrier Physiology in Age-Related Macular Degeneration

The blood retinal barrier (BRB) is a fundamental eye component, whose function is to select the flow of molecules from the blood to the retina and vice-versa, and its integrity allows the maintenance of a finely regulated microenvironment. The outer BRB, composed by the choriocapillaris, the Bruch's membrane, and the retinal pigment epithelium, undergoes structural and functional changes in age-related macular degeneration (AMD), the leading cause of blindness worldwide. BRB alterations lead to retinal dysfunction and neurodegeneration. Several risk factors have been associated with AMD onset in the past decades and oxidative stress is widely recognized as a key factor, even if the exact AMD pathophysiology has not been exactly elucidated yet. The present review describes the BRB physiology, the BRB changes occurring in AMD, the role of oxidative stress in AMD with a focus on the outer BRB structures. Moreover, we propose the use of cerium oxide nanoparticles as a new powerful anti-oxidant agent to combat AMD, based on the relevant existing data which demonstrated their beneficial effects in protecting the outer BRB in animal models of AMD.

The Chemokine Receptors Ccr5 and Cxcr6 Enhance Migration of Mesenchymal Stem Cells into the Degenerating Retina

Cell therapy approaches hold great potential for treating retinopathies, which are currently incurable. This study addresses the problem of inadequate migration and integration of transplanted cells into the host retina. To this end, we have identified the chemokines that were most upregulated during retinal degeneration and that could chemoattract mesenchymal stem cells (MSCs). The results were observed using a pharmacological model of ganglion/amacrine cell degeneration and a genetic model of retinitis pigmentosa, from both mice and human retinae. Remarkably, MSCs overexpressing Ccr5 and Cxcr6, which are receptors bound by a subset of the identified chemokines, displayed improved migration after transplantation in the degenerating retina. They also led to enhanced rescue of cell death and to preservation of electrophysiological function. Overall, we show that chemokines released from the degenerating retinae can drive migration of transplanted stem cells, and that overexpression of chemokine receptors can improve cell therapy-based regenerative approaches.

Lipidomics of the brain, retina, and biofluids: from the biological landscape to potential clinical application in schizophrenia

Schizophrenia is a serious neuropsychiatric disorder, yet a clear pathophysiology has not been identified. To date, neither the objective biomarkers for diagnosis nor specific medications for the treatment of schizophrenia are clinically satisfactory. It is well accepted that lipids are essential to maintain the normal structure and function of neurons in the brain and that abnormalities in neuronal lipids are associated with abnormal neurodevelopment in schizophrenia. However, lipids and lipid-like molecules have been largely unexplored in contrast to proteins and their genes in schizophrenia. Compared with the gene- and protein-centric approaches, lipidomics is a recently emerged and rapidly evolving research field with particular importance for the study of neuropsychiatric disorders such as schizophrenia, in which even subtle aberrant alterations in the lipid composition and concentration of the neurons may disrupt brain functioning. In this review, we aimed to highlight the lipidomics of the brain, retina, and biofluids in both human and animal studies, discuss aberrant lipid alterations in correlation with schizophrenia, and propose future directions from the biological landscape towards potential clinical applications in schizophrenia. Recent studies are in support of the concept that aberrations in some lipid species [e.g. phospholipids, polyunsaturated fatty acids (PUFAs)] lead to structural alterations and, in turn, impairments in the biological function of membrane-bound proteins, the disruption of cell signaling molecule accessibility, and the dysfunction of neurotransmitter systems. In addition, abnormal lipidome alterations in biofluids are linked to schizophrenia, and thus they hold promise in the discovery of biomarkers for the diagnosis of schizophrenia.

Small molecules targeting RORγt inhibit autoimmune disease by suppressing Th17 cell differentiation

Th17 cells, a lymphocyte subpopulation that is characterized by the expression of the transcription factor "retinoic acid receptor-related orphan receptor gamma-t" (RORγt), plays an important role in the pathogenesis of autoimmune disease. The current study was set up to discover novel and non-steroidal small-molecule inverse agonists of RORγt and to determine their effects on autoimmune disease. Structure-based virtual screening (SBVS) was used to find compounds targeting RORγt. Flow cytometry was used to detect the Th17 cell differentiation. Inverse agonists were intraperitoneally administered to mice undergoing experimental autoimmune uveitis (EAU), experimental autoimmune encephalomyelitis (EAE) or type 1 diabetes. The effects of the inverse agonists were evaluated by clinical or histopathological scoring. Among 1.3 million compounds screened, CQMU151 and CQMU152 were found to inhibit Th17 cell differentiation without affecting the differentiation of Th1 and Treg lineages (both P = 0.001). These compounds also reduced the severity of EAU (P = 0.01 and 0.013) and functional studies showed that they reduced the number of Th17 cell and the expression of IL-17(Th17), but not IFN-γ(Th1) and TGF-β(Treg) in mouse retinas. Further studies showed that these compounds may reduce the expression of p-STAT3 by reducing the positive feedback loop of IL-17/IL-6/STAT3. These compounds also reduced the impaired blood-retinal barrier function by upregulating the expression of tight junction proteins. These compounds were also found to reduce the severity of EAE and type 1 diabetes. Our results showed that RORγt inverse agonists may inhibit the development of autoimmune diseases and may provide new clues for the treatment of Th17-mediated immune diseases.

Circulating Leukocyte Alterations and the Development/Progression of Diabetic Retinopathy in Type 1 Diabetic Patients - A Pilot Study

BACKGROUND/AIMS

The aim of this study was to investigate the relationship between alterations in circulating leukocytes and the initiation and progression of DR in people with type 1 diabetes (T1D).

METHODS

Forty-one patients with T1D [13 mild non-proliferative DR (mNPDR), 14 active proliferative DR (aPDR) and 14 inactive PDR (iPDR)], and 13 age- and gender-matched healthy controls were recruited prospectively. Circulating leukocytes, including CD4⁺ and CD8⁺ T-cells, CD14⁺CD16^-, CD14^-CD16⁺ and CD14⁺CD16⁺ monocytes; CD16⁺HLA-DR^- neutrophils, CD19⁺ B-cells and CD56⁺ natural killer cells and their cell surface adhesion molecules and chemokine receptors (HLA-DR, CD62L, CCR2, CCR5, CD66a, CD157 and CD305) were examined by flow cytometry.

RESULTS

In DR patients, compared to healthy controls, increased proportions of neutrophils (p = .0152); reduced proportions of lymphocytes (p = .0002), HLA-DR⁺ leukocytes (p = .0406) and non-classical monocytes (p = .0204); and reduced expression of CD66a (p = .0048) and CD157 (p = .0007) on CD4⁺ T cells were observed. Compared to healthy controls, CD19⁺ B cells were reduced at the mNPDR but not aPDR patients. Total lymphocytes, CD4⁺ T cells and CD8⁺ T cells progressively decreased whereas neutrophils, the neutrophil/lymphocyte ratio and the neutrophil/CD4⁺ ratio progressively increased from early to late stages of DR, reaching statistical significance at the aPDR stage. Longer diabetes duration was associated with a reduced proportion of CD8⁺ T cells (p = .002) and increased neutrophil/CD8⁺ ratio (p = .033).

CONCLUSIONS

In this pilot study, DR is associated with increased innate cellular immunity especially neutrophils and reduced adaptive cellular immunity particularly lymphocytes. Impaired B-cell immunity may play a role in the initiation of DR; whereas impaired T-cell immunity with increased neutrophil response may contribute to progression of DR from non-proliferative to proliferative stages in T1D patients. Large multicenter studies are needed to further understand the immune dysregulation in DR initiation and progression.

The Role of Immune Checkpoint Blockade in Uveal Melanoma

Uveal melanoma (UM) represents the most common intraocular malignancy in adults and accounts for about 5% of all melanomas. Primary disease can be effectively controlled by several local therapy options, but UM has a high potential for metastatic spread, especially to the liver. Despite its clinical and genetic heterogeneity, therapy of metastatic UM has largely been adopted from cutaneous melanoma (CM) with discouraging results until now. The introduction of antibodies targeting CTLA-4 and PD-1 for immune checkpoint blockade (ICB) has revolutionized the field of cancer therapy and has achieved pioneering results in metastatic CM. Thus, expectations were high that patients with metastatic UM would also benefit from these new therapy options. This review provides a comprehensive and up-to-date overview on the role of ICB in UM. We give a summary of UM biology, its clinical features, and how it differs from CM. The results of several studies that have been investigating ICB in metastatic UM are presented. We discuss possible reasons for the lack of efficacy of ICB in UM compared to CM, highlight the pitfalls of ICB in this cancer entity, and explain why other immune-modulating therapies could still be an option for future UM therapies.

Prospective study of aflibercept for the treatment of persistent macular oedema secondary to retinal vein occlusions in eyes not responsive to long-term treatment with bevacizumab or ranibizumab

IMPORTANCE

To examine the effect of switching from intravitreal bevacizumab or ranibizumab to aflibercept in eyes with persistent macular oedema due to retinal vein occlusion (RVO).

BACKGROUND

We report the results of a prospective interventional study on the effect of aflibercept 2 mg in eyes with persistent macular oedema after long-term treatment with bevacizumab or ranibizumab.

DESIGN

Non-randomized, prospective clinical trial.

PARTICIPANTS

Eighteen eyes of eighteen patients were included.

METHODS

Eyes with persistent macular oedema despite a minimum of four previous intravitreal bevacizumab/ranibizumab injections were recruited into this 48-week trial. Three loading doses of intravitreal aflibercept were administered every 4-weeks, thereafter every 8-weeks until week 48.

MAIN OUTCOME MEASURES

Mean change from baseline in best corrected visual acuity (BCVA) as measured by early treatment diabetic retinopathy score (ETDRS) and central macular thickness (CMT) as measured by spectral domain optical coherence tomography (SD-OCT) at 48 weeks.

RESULTS

Patients had received a mean of 40.0 ± 17.8 bevacizumab/ranibizumab intravitreal injections prior to switching to aflibercept. The mean number of previous injections administered in the 12-months preceding entry into the study was 10.2 ± 2.4. Mean vision change at week 48 was +21.1 ± 5.1 ETDRS letters in the BRVO group and +18.8 ± 5.9 letters at in the CRVO group (P < .001 for both groups). Mean decrease in CMT was 87.6 ± 48.8 μm and 191.0 ± 128.3 μm, in the BRVO and CRVO groups, respectively (P < .001). Using linear regression analyses, a higher number of previous intravitreal ranibizumab/bevacizumab injections and thicker pre-switch CMT were correlated with greater visual gains.

CONCLUSION AND RELEVANCE

Switching to aflibercept from bevacizumab or ranibizumab in eyes with persistent macular oedema due to RVO can lead to functional and anatomical improvement. This effect was more obvious in eyes with a greater CMT prior to the switch.

Insights into the pathogenesis of cystoid macular edema: leukostasis and related cytokines

Cystoid macular edema (CME) is the abnormal collection of intraretinal fluid in the macular region, especially in the inner nuclear and outer plexiform layers. CME leads to severe visual impairment in patients with various retinal diseases, such as diabetic retinopathy, retinal vascular occlusion, choroidal neovascularization, and uveitis. Although various retinal conditions lead to CME, a shared pathogenesis of CME is involved in these diseases. Accordingly, the pathogenesis of CME based on vasogenic mechanisms is first discussed in this review, including vascular hyperpermeability, leukostasis, and inflammation. We then describe cytotoxic mechanisms based on retinal Müller cell dysfunction. This comprehensive review will provide an understanding of the pathogenesis of CME for potential therapeutic strategies.

The Anti-Inflammatory Effects of CXCR5 in the Mice Retina following Ischemia-Reperfusion Injury

Object

Retinal ischemia-reperfusion (I/R) injury is a common pathological process in many ophthalmic diseases; there are no effective therapeutic approaches available currently. Increasing evidence indicates that microglia mediated neuroinflammation plays an important role in the retinal I/R injury. In this study, we aimed to investigate the roles of chemokine receptor CXCR5 in the pathological process of retinal I/R injury model.

Method

Retinal I/R injury model was established in CXCR5 knockout and wild mice by the acute elevation of intraocular pressure (AOH) for 60 minutes, and the eyes were harvested for further analyses. The cellular location of CXCR5 was detected by immunofluorescence staining; the expressions of CXCR5 and CXCL13 after I/R injury were analyzed by quantitative RT-PCR. The retinal microglia were detected as stained for Iba1 (+). Leakage of inflammatory cells was observed on the H&E stained cryosections. The protein expression and quantification of zonula occludens (ZO-1) were determined by Western blotting and densitometry. Capillary degeneration was identified on the intact retinal vasculatures prepared by trypsin digestion.

Results

The number of activated microglia marked by Iba1 antibody in the retina was increased after retinal I/R injury in both KO and WT mice, more significant in KO mice. The leakage of inflammatory cells was observed largely at 2 days after injury, but there was no or little leakage at 7 days. The number of inflammatory cells (mainly neutrophils) was greater in CXCR5 KO mice than in WT mice, mainly located under internal limiting membrane. CXCR5 deficiency led to more ZO-1 degradation in CXCR5 KO mice compared to C57BL6 WT mice 2 days after reperfusion. The cellular capillaries were also significantly increased in the KO mice compared to the WT mice.

Conclusion

Our findings suggest that the chemokine receptor CXCR5 may protect retina from ischemia-reperfusion injury by its anti-inflammatory effects. Thus, CXCR5 may be a promising therapeutic target for the treatment of retinal I/R injury.

Organ-On-A-Chip Technologies for Advanced Blood-Retinal Barrier Models

The blood-retinal barrier (BRB) protects the retina by maintaining an adequate microenvironment for neuronal function. Alterations of the junctional complex of the BRB and consequent BRB breakdown in disease contribute to a loss of neuronal signaling and vision loss. As new therapeutics are being developed to prevent or restore barrier function, it is critical to implement physiologically relevant in vitro models that recapitulate the important features of barrier biology to improve disease modeling, target validation, and toxicity assessment. New directions in organ-on-a-chip technology are enabling more sophisticated 3-dimensional models with flow, multicellularity, and control over microenvironmental properties. By capturing additional biological complexity, organs-on-chip can help approach actual tissue organization and function and offer additional tools to model and study disease compared with traditional 2-dimensional cell culture. This review describes the current state of barrier biology and barrier function in ocular diseases, describes recent advances in organ-on-a-chip design for modeling the BRB, and discusses the potential of such models for ophthalmic drug discovery and development.

Retinal microglia initiate neuroinflammation in ocular autoimmunity

Autoimmune uveitis is a sight-threatening ocular inflammatory condition in which the retina and uveal tissues become a target of autoreactive immune cells. While microglia have been studied extensively in autoimmune uveitis, their exact function remains uncertain. The objective of the current study was to determine whether resident microglia are necessary and sufficient to initiate and amplify retinal inflammation in autoimmune uveitis. In this study, we clearly demonstrate that microglia are essential for initiating infiltration of immune cells utilizing a murine model of experimental autoimmune uveoretinitis (EAU) and the recently identified microglia-specific marker P2ry12. Initiating disease is the primary function of microglia in EAU, since eliminating microglia during the later stages of EAU had little effect, indicating that the function of circulating leukocytes is to amplify and sustain destructive inflammation once microglia have triggered disease. In the absence of microglia, uveitis does not develop, since leukocytes cannot gain entry through the blood-retinal barrier, illustrating that microglia play a critical role in regulating infiltration of inflammatory cells into the retina.

Photopic light-mediated down-regulation of local α1A-adrenergic signaling protects blood-retina barrier in experimental autoimmune uveoretinitis

We have reported the gateway reflex, which describes specific neural activations that regulate immune cell gateways at specific blood vessels in the central nervous system (CNS). Four types of gateway reflexes exist, all of which induce alterations in endothelial cells at specific vessels of the blood-brain barrier followed by inflammation in the CNS in the presence of CNS-autoreactive T cells. Here we report a new gateway reflex that suppresses the development of retinal inflammation by using an autoreactive T cell-mediated ocular inflammation model. Exposure to photopic light down-regulated the adrenoceptor pathway to attenuate ocular inflammation by suppressing breaching of the blood-retina barrier. Mechanistic analysis showed that exposure to photopic light down-regulates the expression of α_1A-adrenoceptor (α_1AAR) due to high levels of norepinephrine and epinephrine, subsequently suppressing inflammation. Surgical ablation of the superior cervical ganglion (SCG) did not negate the protective effect of photopic light, suggesting the involvement of retinal noradrenergic neurons rather than sympathetic neurons from the SCG. Blockade of α_1AAR signaling under mesopic light recapitulated the protective effect of photopic light. Thus, targeting regional adrenoceptor signaling might represent a novel therapeutic strategy for autoimmune diseases including those that affect organs separated by barriers such as the CNS and eyes.

Low molecular-weight hyaluronan as a cryoprotectant for the storage of microencapsulated cells

The low-temperature storage of therapeutic cell-based products plays a crucial role in their clinical translation for the treatment of diverse diseases. Although dimethylsulfoxide (DMSO) is the most successful cryoprotectant in slow freezing of microencapsulated cells, it has shown adverse effects after cryopreserved cell-based products implantation. Therefore, the search of alternative non-toxic cryoprotectants for encapsulated cells is continuously investigated to move from bench to the clinic. In this work, we investigated the low molecular-weight hyaluronan (low MW-HA), a natural non-toxic and non-sulfated glycosaminoglycan, as an alternative non-permeant cryoprotectant for the slow freezing cryopreservation of encapsulated cells. Cryopreservation with low MW-HA provided similar metabolic activity, cell dead and early apoptotic cell percentage and membrane integrity after thawing, than encapsulated cells stored with either DMSO 10% or Cryostor 10. However, the beneficial outcomes with low MW-HA were not comparable to DMSO with some encapsulated cell types, such as the human insulin secreting cell line, 1.1B4, maybe explained by the different expression of the CD44 surface receptor. Altogether, we can conclude that low MW-HA represents a non-toxic natural alternative cryoprotectant to DMSO for the cryopreservation of encapsulated cells.