Use of optical coherence tomography and electroretinography to evaluate retinal pathology in a mouse model of autoimmune uveitis

Preclinical Retinal Disease Models: Applications in Drug Development and Translational Research

Retinal models play a pivotal role in translational drug development, bridging preclinical research and therapeutic applications for both ocular and systemic diseases. This review highlights the retina as an ideal organ for studying advanced therapies, thanks to its immune privilege, vascular and neuronal networks, accessibility, and advanced imaging capabilities. Preclinical retinal disease models offer unparalleled insights into inflammation, angiogenesis, fibrosis, and hypoxia, utilizing clinically translatable bioimaging tools like fundoscopy, optical coherence tomography, confocal scanning laser ophthalmoscopy, fluorescein angiography, optokinetic tracking, and electroretinography. These models have driven innovations in anti-inflammatory, anti-angiogenic, and neuroprotective strategies, with broader implications for systemic diseases such as rheumatoid arthritis, Alzheimer's, and fibrosis-related conditions. By emphasizing the integration of the 3Rs principles and novel imaging modalities, this review highlights how retinal research not only enhances therapeutic precision but also minimizes ethical concerns, paving the way for more predictive and human-relevant approaches in drug development.

Comparative models of uveitis

Several clinical subtypes of uveitis exist yet specific immunopathogenic mechanisms involved remain unclear. Ex vivo studies are limited by lack of fresh retinal biopsies and studies have relied on aqueous humour or peripheral blood, which may not directly reflect disease. The aim of this review is to compare the various in vivo models and review their contributions to our understanding of disease processes. These models, although unable to reflect all clinical signs, have provided insight into the contribution of genes and molecules, characterisation of effector T-cells, cell trafficking into retinal tissues, the contribution of tissue-resident myeloid cells and the mechanism(s) of action of several anti-inflammatory compounds. In vivo uveitis models have provided an excellent resource with which to study the molecular and cellular processes involved. Recent refinements in models, improved imaging, and the application of omics have greatly increased the number of readouts and translational opportunities. Future approaches with in vitro models will also be discussed.

Preclinical characterization of endotoxin-induced uveitis models using OCT, PET/CT and proteomics

Uveitis is a group of inflammatory ocular pathologies. Endotoxin-Induced Uveitis (EIU) model represent a well-known model induced by administration of Lipopolysaccharide (LPS). The aim is to characterize two models of EIU through two routes of administration with novel noninvasive imaging techniques. 29 rats underwent Intraocular Pressure (IOP) measurements, Optical Coherence Tomography (OCT), proteomic analysis, and Positron Emission Tomography and Computed Tomography (PET/CT). Groups included healthy controls (C), BSS administered controls (Ci), systemically induced EIU with LPS (LPSs), and intravitreally induced EIU with LPS (LPSi) for IOP, OCT, and proteomic studies. For 18F-FDG PET/CT study, animals were divided into FDG-C, FDG-LPSs and FDG-LPSi groups and scanned using a preclinical PET/CT system. LPSi animals exhibited higher IOP post-induction compared to C and LPSs groups. LPSi showed increased cellular infiltrate, fibrotic membranes, and iris inflammation. Proinflammatory proteins were more expressed in EIU models, especially LPSi. PET/CT indicated higher eye uptake in induced models compared to FDG-C. FDG-LPSi showed higher eye uptake than FDG-LPSs but systemic uptake was higher in FDG-LPSs due to generalized inflammation. OCT is valuable for anterior segment assessment in experimental models. 18F-FDG PET/CT shows promise as a noninvasive biomarker for ocular inflammatory diseases. Intravitreal induction leads to higher ocular inflammation. These findings offer insights for future inflammatory disease research and drug studies.

Comprehensive Grading System for Experimental Autoimmune Uveitis in Mice

Experimental autoimmune uveitis (EAU) is the most commonly used animal model to study the progression of chronic uveitis and to test various therapies to treat the disease. However, to accurately evaluate the effectiveness of such treatments, a grading system that combines the latest imaging techniques with definitive quantitative grading thresholds is required. This study aimed to develop a comprehensive grading system that objectively evaluates EAU progression in C57BL/6J mice. EAU was induced following immunisation with interphotoreceptor retinoid-binding protein (IRBP) and pertussis toxin. Weekly fundus and optical coherence tomography (OCT) images were acquired over 12 weeks using a Micron IV imaging system. Each mouse was graded (between 0 to 4) based on changes seen on both the fundus (optic disc, retinal blood vessels and retinal tissue) and OCT (vitreous and retinal layers) images. A total EAU response (with a maximum score of 48) was calculated for each mouse based on the sum of the individual scores each week. Analysis of the clinical scores depicted a gradual increase in inflammatory signs including optic disc and vascular swelling, leukocyte infiltration in the vitreous, lesions in the retina and formation of granulomas and hyper-reflective foci in the retinal layers in EAU mice, with most signs reaching a plateau towards the end of the study period. Development of these signs into sight-threatening complications such as optic disc atrophy, structural damage to the retina and subretinal oedema were noted in 80-90% of mice suggesting consistent disease induction. Overall, a comprehensive and objective grading system encompassing all pathologies occurring in EAU mice was developed to enhance the preclinical evaluation of novel uveitis treatments.

Induction of antigen-specific Treg cells in treating autoimmune uveitis via bystander suppressive pathways without compromising anti-tumor immunity

BACKGROUND

Induction of autoantigen-specific Treg cells that suppress tissue-specific autoimmunity without compromising beneficial immune responses is the holy-grail for immunotherapy to autoimmune diseases.

METHODS

In a model of experimental autoimmune uveitis (EAU) that mimics human uveitis, ocular inflammation was induced by immunization with retinal antigen interphotoreceptor retinoid-binding protein (IRBP). Mice were given intraperitoneal injection of αCD4 antibody (Ab) after the onset of disease, followed by administration of IRBP. EAU was evaluated clinically and functionally. Splenocytes, CD4⁺CD25^- and CD4⁺CD25⁺ T cells were sorted and cultured with IRBP or αCD3 Ab. T cell proliferation and cytokine production were assessed.

FINDINGS

The experimental approach resulted in remission of ocular inflammation and rescue of visual function in mice with established EAU. Mechanistically, the therapeutic effect was mediated by induction of antigen-specific Treg cells that inhibited IRBP-driven Th17 response in TGF-β and IL-10 dependent fashion. Importantly, the Ab-mediated immune tolerance could be achieved in EAU mice by administration of retinal autoantigens, arrestin but not limited to IRBP only, in an antigen-nonspecific bystander manner. Further, these EAU-suppressed tolerized mice did not compromise their anti-tumor T immunity in melanoma model.

INTERPRETATION

We successfully addressed a specific immunotherapy of EAU by in vivo induction of autoantigen-specific Treg cells without compromising host overall T cell immunity, which should have potential implication for patients with autoimmune uveitis.

FUNDING

This study was supported by the Natural Science Foundation of Guangdong Province and the Fundamental Research Fund of the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center.

Quantitative Assessment of Experimental Ocular Inflammatory Disease

Ocular inflammation imposes a high medical burden on patients and substantial costs on the health-care systems that mange these often chronic and debilitating diseases. Many clinical phenotypes are recognized and classifying the severity of inflammation in an eye with uveitis is an ongoing challenge. With the widespread application of optical coherence tomography in the clinic has come the impetus for more robust methods to compare disease between different patients and different treatment centers. Models can recapitulate many of the features seen in the clinic, but until recently the quality of imaging available has lagged that applied in humans. In the model experimental autoimmune uveitis (EAU), we highlight three linked clinical states that produce retinal vulnerability to inflammation, all different from healthy tissue, but distinct from each other. Deploying longitudinal, multimodal imaging approaches can be coupled to analysis in the tissue of changes in architecture, cell content and function. This can enrich our understanding of pathology, increase the sensitivity with which the impacts of therapeutic interventions are assessed and address questions of tissue regeneration and repair. Modern image processing, including the application of artificial intelligence, in the context of such models of disease can lay a foundation for new approaches to monitoring tissue health.

Licarin A as a Novel Drug for Inflammatory Eye Diseases

Purpose: This study investigated the safety and therapeutic efficacy of licarin A (LCA) in the treatment of intraocular inflammation. Methods: In vitro safety of LCA in retinal pigmented epithelial cells (ARPE-19) and human embryonic stem cell derived-retinal pigmented epithelial cells (hES-RPE) was evaluated using CellTiter-Blue^® kit. The chorioallantoic membrane (CAM) assay was used to investigate LCA safety and antiangiogenic activity. In vivo safety of intravitreal LCA was accomplished by clinical examination (including assessment of intraocular pressure), electroretinography (ERG), and histopathology. Uveitis was induced in rats by subcutaneous and intravitreal injection of bacillus Calmette-Guérin (BCG) antigen of Mycobacterium bovis. Intraocular inflammation was graded by slit-lamp and fundus examination, ERG, and histopathology. Results: LCA was safe to cells and to the CAM at concentration below 12.0 μM. LCA significantly reduced the percentage of blood vessels in the CAM. Retinal safety and anti-inflammatory efficacy of intravitreal injection of LCA 6.0 μM were confirmed through clinical, functional, and histopathological evaluation. Significant reduction of inflammatory cytokines (tumor necrosis factor-α and interleukin-6) was also found, when compared to untreated animals. Conclusion: The results suggest that LCA is a potential new drug for the treatment of inflammatory eye disease.

STAT3 deficiency in B cells exacerbates uveitis by promoting expansion of pathogenic lymphocytes and suppressing regulatory B cells (Bregs) and Tregs

STAT3 transcription factor induces differentiation of naïve T cells into Th17 cells and loss of STAT3 in T cell prevents development of CNS autoimmune diseases. However, function of STAT3 in the B lymphocyte subset is not well understood. In this study, we have generated mice lacking STAT3 in CD19⁺ B cells (CD19-STAT3KO) and investigated intrinsic and extrinsic functions of STAT3 in B cells and its potential role in resistance or pathogenesis of organ-specific autoimmune diseases. We show that STAT3 regulates metabolic mechanisms in B cells with implications for bioenergetic and metabolic pathways that control cellular homeostasis in B cells. Thus, loss of STAT3 in CD19-STAT3KO cells perturbed growth and apoptosis by inducing rapid entry of B cells into the S-phase of the cell cycle, decreasing expression of cyclin-dependent kinase inhibitors and upregulating pro-apoptotic proteins. We further show that the CD19-STAT3KO mice develop severe experimental autoimmune uveitis (EAU), an animal model of human uveitis. Exacerbated uveitis in CD19-STAT3KO mice derived in part from enhanced expression of costimulatory molecules on B cells, marked increase of Th17 responses and increased recruitment of granulocytes into the neuroretina. The enhanced autoimmunity upon deletion of STAT3 in B cells is also recapitulated in experimental autoimmune encephalitis, a mouse model of multiple sclerosis and thus support our conclusion that STAT3 deletion in B cells enhanced inflammation and the effects observed are not model specific. Our data further indicate that STAT3 pathway modulates interactions between B and T cells during EAU resulting in alteration of lymphocyte repertoire by increasing levels of autoreactive pathogenic T cells while suppressing development and/or expansion of immune-suppressive lymphocytes (Bregs and Tregs). Taken together, STAT3 exerts diametrically opposite effects in lymphocytes, with loss of STAT3 in B cells exacerbating uveitis whereas Stat3 deletion in T cells confers protection.

Spectral Domain Optical Coherence Tomography in Awake Rabbits Allows Identification of the Visual Streak, a Comparison with Histology

Purpose

To evaluate visual streak (VS) identification on spectral-domain optical coherence tomography (SD-OCT) scans in awake rabbits. To report thickness measurements in the VS and adjacent retina on OCT B-scans and histologic sections and to assess inter-method bias, precision and repeatability between OCT and histology.

Methods

Vertical SD-OCT B-scan images through the optic nerve head and VS were acquired from 16 awake, ophthalmologically healthy experimental rabbits. Scans were acquired from both eyes, which were later enucleated and processed for light microscopy. Inner retina, inner nuclear layer, outer nuclear layer, outer retina (OR) and photoreceptor outer segment (PROS) thickness were measured on OCT images and digitalized microscopy slides in- and outside of the VS, and compared using linear mixed effects models.

Results

Both SD-OCT and histology allowed retinal layer identification and measurement. On OCT, OR and PROS were thickest in the central VS and thinnest outside the VS. Histology mirrored OCT results for central outer retinal layers but shows discrepancies for other layers likely because of postmortem processing artifacts. The method comparison demonstrated better repeatability for OCT measurements compared with histology.

Conclusions

Increased OR and PROS thickness compared with the adjacent retina allowed identification of the VS on SD-OCT in awake rabbits. OCT allows measurements devoid of processing artifacts in contrast to histology.

Translational Relevance

SD-OCT is possible in awake rabbits. Easy and reliable identification of the VS may facilitate the positioning and use of rabbits as model species in human macular and generalized retinal disease research.

Model Systems for Studying Mechanisms of Ocular Toxoplasmosis

The most common human disease caused by infection with Toxoplasma gondii is ocular toxoplasmosis, which typically is manifest as recurrent attacks of necrotizing retinal inflammation with subsequent scarring. The multilayered retina contains specialized cell populations, including endothelial cells, epithelial cells, neurons and supporting cells, all of which may be involved in this condition. In vitro investigations of basic mechanisms operating in human ocular toxoplasmosis use cellular and molecular methods that are common to the study of many pathological processes, and the novel aspect of this research is the use of human retinal cell subsets. Most in vivo research on ocular toxoplasmosis is conducted in the laboratory mouse. Experimental models involve local or systemic inoculation of parasites to induce acute disease, or sequential systemic and local parasite inoculations to trigger recurrent disease. We present methods for in vitro and in vivo studies of ocular toxoplasmosis, including dissection of the human eye, and culture and infection of differentiated cell populations from the retina, as well as induction of mouse ocular toxoplasmosis by intraocular, or sequential systemic and intraocular, inoculations, and imaging of toxoplasmic retinal lesions.

AAV Mediated Delivery of Myxoma Virus M013 Gene Protects the Retina against Autoimmune Uveitis

Uveoretinitis is an ocular autoimmune disease caused by the activation of autoreactive T- cells targeting retinal antigens. The myxoma M013 gene is known to block NF-κB (Nuclear Factor kappa-light-chain-enhancer of activated B cells) and inflammasome activation, and its gene delivery has been demonstrated to protect the retina against lipopolysaccharide (LPS)-induced uveitis. In this report we tested the efficacy of M013 in an experimental autoimmune uveoretinitis (EAU) mouse model. B10RIII mice were injected intravitreally with AAV (adeno associated virus) vectors delivering either secreted GFP (sGFP) or sGFP-TatM013. Mice were immunized with interphotorecptor retinoid binding protein residues 161–180 (IRBP_161–180) peptide in complete Freund’s adjuvant a month later. Mice were evaluated by fundoscopy and spectral domain optical coherence tomography (SD-OCT) at 14 days post immunization. Eyes were evaluated by histology and retina gene expression changes were measured by reverse transcribed quantitative PCR (RT-qPCR). No significant difference in ERG or retina layer thickness was observed between sGFP and sGFP-TatM013 treated non-uveitic mice, indicating safety of the vector. In EAU mice, expression of sGFP-TatM013 strongly lowered the clinical score and number of infiltrative cells within the vitreous humor when compared to sGFP treated eyes. Retina structure was protected, and pro-inflammatory genes expression was significantly decreased. These results indicate that gene delivery of myxoma M013 could be of clinical benefit against autoimmune diseases.

Type I Interferon Therapy Limits CNS Autoimmunity by Inhibiting CXCR3-Mediated Trafficking of Pathogenic Effector T Cells

Type I interferons (IFNs) have therapeutic potential in CNS autoimmune diseases, such as uveitis, but the molecular mechanisms remain unclear. Using a T cell-transfer model of experimental autoimmune uveitis (EAU), we found that IFN-α/β treatment inhibited the migration of IFN-γ-producing pathogenic CD4+ T cells to effector sites. IFN-α/β upregulated the expression of the cognate ligands CXCL9, CXCL10, and CXCL11, causing ligand-mediated downregulation of CXCR3 expression and effector T cell retention in the spleen. Accordingly, type I IFN did not alter EAU progression in CXCR3-/- mice. In uveitis patients, disease exacerbations correlated with reduced serum IFN-α concentrations. IFN-α/β reduced CXCR3 expression and migration by human effector T cells, and these parameters were associated with the therapeutic efficacy of IFN-α in uveitis patients. Our findings provide insight into the molecular basis of type I IFN therapy for CNS autoimmune diseases and identify CXCR3 as a biomarker for effective type I IFN immunotherapy.

Clinical and Functional Evaluation of Ocular Inflammatory Disease Using the Model of Experimental Autoimmune Uveitis

Non-infections uveitis in humans is an autoimmune disease of the retina and uvea that can be blinding if untreated. Its laboratory equivalent is experimental autoimmune uveitis (EAU) induced in susceptible rodents by immunization with retinal antigens and described elsewhere in this series (Agarwal et al., Methods Mol Biol, 900:443-469, 2012). Evaluation and quantitation of the disease is usually performed by fundus examination and/or histopathology, which provide limited information on structural and no information on functional changes as disease progresses. Here, we describe methods for systematic evaluation of disease using noninvasive clinical assessments by fundus examination and photography, optical coherence tomography, and functional evaluation by electroretinography, which are then compared to histopathology. Using these methodologies, we demonstrate that clinical variants of disease can be accurately evaluated both clinically and functionally, facilitating longitudinal follow-up and providing information that cannot be obtained by fundoscopy and histology alone. These methodologies can be useful to obtain additional information and to evaluate effects of therapeutic modalities under investigation.

Acid Ceramidase Deficiency in Mice Leads to Severe Ocular Pathology and Visual Impairment

Farber disease (FD) is a debilitating lysosomal storage disorder characterized by severe inflammation and neurodegeneration. FD is caused by mutations in the ASAH1 gene, resulting in deficient acid ceramidase (ACDase) activity. Patients with ACDase deficiency exhibit a broad clinical spectrum. In classic cases, patients develop hepatosplenomegaly, nervous system involvement, and childhood mortality. Ocular manifestations include decreased vision, a grayish appearance to the retina with a cherry red spot, and nystagmus. That said, the full effect of ACDase deficiency on the visual system has not been studied in detail. We previously developed a mouse model that is orthologous for a known patient mutation in Asah1 that recapitulates human FD. Herein, we report evidence of a severe ocular pathology in Asah1^P361R/P361R mice. Asah1^P361R/P361R mice exhibit progressive retinal and optic nerve pathology. Through noninvasive ocular imaging and histopathological analyses of these Asah1^P361R/P361R animals, we revealed progressive inflammation, the presence of retinal dysplasia, and significant storage pathology in various cell types in both the retina and optic nerves. Lipidomic analyses of retinal tissues revealed an abnormal accumulation of ceramides and other sphingolipids. Electroretinograms and behavioral tests showed decreased retinal and visual responses. Taken together, these data suggest that ACDase deficiency leads to sphingolipid imbalance, inflammation, dysmorphic retinal and optic nerve pathology, and severe visual impairment.

Complement-Mediated Activation of the NLRP3 Inflammasome and Its Inhibition by AAV-Mediated Delivery of CD59 in a Model of Uveitis

Uveitis is an inflammatory disorder of the eye responsible for approximately 10%-15% of blindness in the US. In this study, we examined the role of the complement membrane attack complex (MAC) and the NLRP3 inflammasome in the pathogenesis of experimental autoimmune uveitis (EAU) in normal and C9^-/- mice that are incapable of assembling the MAC. We discovered that the MAC and the NLRP3 inflammasome and associated production of IL-1β are elevated in EAU mice and that MAC may be involved in regulation of Th1 and Th17 cell differentiation. In contrast, MAC and the NLRP3 inflammasome were not elevated in C9^-/- mice. However, EAU-associated pathophysiology including retinal structure and function were not rescued in C9^-/- mice. Unexpectedly, AAV-mediated delivery of sCD59, an inhibitor of C9 incorporation into the MAC, successfully attenuated activation of the NLRP3 inflammasome and EAU pathology as well as MAC. Our studies provide an improved understanding of the role of the MAC and the NLRP3 inflammasome in EAU as well as suggest a novel approach for the treatment of uveitis.

IL-12p35 induces expansion of IL-10 and IL-35-expressing regulatory B cells and ameliorates autoimmune disease

Interleukin 35 (IL-35) is a heterodimeric cytokine composed of IL-12p35 and Ebi3 subunits. IL-35 suppresses autoimmune diseases while preventing host defense to infection and promoting tumor growth and metastasis by converting resting B and T cells into IL-10-producing and IL-35-producing regulatory B (Breg) and T (Treg) cells. Despite sharing the IL-12p35 subunit, IL-12 (IL-12p35/IL-12p40) promotes inflammatory responses whereas IL-35 (IL-12p35/Ebi3) induces regulatory responses, suggesting that IL-12p35 may have unknown intrinsic immune-regulatory functions regulated by its heterodimeric partner. Here we show that the IL-12p35 subunit has immunoregulatory functions hitherto attributed to IL-35. IL-12p35 suppresses lymphocyte proliferation, induces expansion of IL-10-expressing and IL-35-expressing B cells and ameliorates autoimmune uveitis in mice by antagonizing pathogenic Th17 responses. Recapitulation of essential immunosuppressive activities of IL-35 indicates that IL-12p35 may be utilized for in vivo expansion of Breg cells and autologous Breg cell immunotherapy. Furthermore, our uveitis data suggest that intrinsic immunoregulatory activities of other single chain IL-12 subunits might be exploited to treat other autoimmune diseases.

IL-12p35 is common to IL-35 and IL-12, which have opposing effects on inflammation. Here the authors show that the IL-12p35 subunit induces regulatory B cells and can be used therapeutically to limit autoimmune uveitis in mice.

In Vivo Bioluminescence Imaging for Longitudinal Monitoring of Inflammation in Animal Models of Uveitis

Purpose

We develop a quantitative bioluminescence assay for in vivo longitudinal monitoring of inflammation in animal models of uveitis.

Methods

Three models of experimental uveitis were induced in C57BL/6 albino mice: primed mycobacterial uveitis (PMU), endotoxin-induced uveitis (EIU), and experimental autoimmune uveitis (EAU). Intraperitoneal injection of luminol sodium salt, which emits light when oxidized, provided the bioluminescence substrate. Bioluminescence images were captured by a PerkinElmer In Vivo Imaging System (IVIS) Spectrum and total bioluminescence was analyzed using Living Image software. Bioluminescence on day zero was compared to bioluminescence on the day of peak inflammation for each model. Longitudinal bioluminescence imaging was performed in EIU and EAU.

Results

In the presence of luminol, intraocular inflammation generates detectable bioluminescence in three mouse models of uveitis. Peak bioluminescence in inflamed PMU eyes (1.46 × 10⁵ photons/second [p/s]) was significantly increased over baseline (1.47 × 10⁴ p/s, P = 0.01). Peak bioluminescence in inflamed EIU eyes (3.18 × 10⁴ p/s) also was significantly increased over baseline (1.09 × 10⁴ p/s, P = 0.04), and returned to near baseline levels by 48 hours. In EAU, there was a nonsignificant increase in bioluminescence at peak inflammation.

Conclusions

In vivo bioluminescence may be used as a noninvasive, quantitative measure of intraocular inflammation in animal models of uveitis. Primed mycobacterial uveitis and EIU are both acute models with robust anterior inflammation and demonstrated significant changes in bioluminescence corresponding with peak inflammation. Experimental autoimmune uveitis is a more indolent posterior uveitis and generated a more modest bioluminescent signal. In vivo imaging system bioluminescence is a nonlethal, quantifiable assay that can be used for monitoring inflammation in animal models of uveitis.

DBA/2J mouse model for experimental glaucoma: pitfalls and problems

BACKGROUND

The DBA/2J mouse has been described as a model for congenital experimental glaucoma. It develops anterior segment anomalies with synechiae and pigment dispersion leading to raised intraocular pressure and glaucomatous damage. However, there are serious practical considerations when using this model in longitudinal studies.

METHODS

We followed 118 mice from 12-48 weeks of age in a pharmaceutical trial. Here we report on the findings in control animals (n = 37). Intraocular pressure was measured weekly, electrophysiology and optical coherence tomography every 6 weeks. A subset also had invasive intraocular pressure measurements performed prior to euthanasia.

RESULTS

Although intraocular pressure eventually rose by 9 months in most animals, tonometry was complicated by corneal calcification in the majority of animals rendering intraocular pressure measurement unreliable. Invasive intraocular pressure did not correlate with non-invasive measures. Loss of scotopic threshold response and thinning of inner retinal layers on optical coherence tomography was observed over time, suggesting glaucomatous damage, but this occurred in some animals without raised intraocular pressure. Poor pupil dilation significantly affected electrophysiology, optical coherence tomography and fundus imaging; 22% of animals developed major systemic complications leading to high dropout rate.

CONCLUSIONS

The DBA/2J experimental glaucoma model shows variability in expression, and its pathological changes cause major difficulties in assessing disease progression. From our experience, the model presents significant challenges for drug studies in glaucoma, as there are many confounding factors: difficulty with accurate intraocular pressure measurement, in vivo imaging, and electrophysiology recording and a high dropout rate. In addition, there may be an underlying neurodegenerative process independent of intraocular pressure.

Quantitative Assessment of Anterior Segment Inflammation in a Rat Model of Uveitis Using Spectral-Domain Optical Coherence Tomography

Purpose

To develop anterior segment spectral-domain optical coherence tomography (SD-OCT) and quantitative image analysis for use in experimental uveitis in rats.

Methods

Acute anterior uveitis was generated in Lewis rats. A spectral domain anterior segment OCT system was used to image the anterior chamber (AC) and ciliary body at baseline and during peak inflammation 2 days later. Customized MatLab image analysis algorithms were developed to segment the AC, count AC cells, calculate central corneal thickness (CCT), segment the ciliary body and zonules, and quantify the level of ciliary body inflammation with the ciliary body index (CBI). Images obtained at baseline and during peak inflammation were compared. Finally, longitudinal imaging and image analysis was performed over the 2-week course of inflammation.

Results

Spectral-domain optical coherence tomography identifies structural features of inflammation. Anterior chamber cell counts at peak inflammation obtained by automated image analysis and human grading were highly correlated (r = 0.961), and correlated well with the histologic score of inflammation (r = 0.895). Inflamed eyes showed a significant increase in average CCT (27 μm, P = 0.02) and an increase in average CBI (P < 0.0001). Longitudinal imaging and quantitative image analysis identified a significant change in AC cell and CBI on day 2 with spontaneous resolution of inflammation by day 14.

Conclusions

Spectral-domain optical coherence tomography provides high-resolution images of the structural changes associated with anterior uveitis in rats. Anterior chamber cell count and CBI determined by semi-automated image analysis strongly correlates with inflammation, and can be used to quantify inflammation longitudinally in single animals.

Anatomical and Gene Expression Changes in the Retinal Pigmented Epithelium Atrophy 1 (rpea1) Mouse: A Potential Model of Serous Retinal Detachment

Purpose

The purpose of this study was to examine the rpea1 mouse whose retina spontaneously detaches from the underlying RPE as a potential model for studying the cellular effects of serous retinal detachment (SRD).

Methods

Optical coherence tomography (OCT) was performed immediately prior to euthanasia; retinal tissue was subsequently prepared for Western blotting, microarray analysis, immunocytochemistry, and light and electron microscopy (LM, EM).

Results

By postnatal day (P) 30, OCT, LM, and EM revealed the presence of small shallow detachments that increased in number and size over time. By P60 in regions of detachment, there was a dramatic loss of PNA binding around cones in the interphotoreceptor matrix and a concomitant increase in labeling of the outer nuclear layer and rod synaptic terminals. Retinal pigment epithelium wholemounts revealed a patchy loss in immunolabeling for both ezrin and aquaporin 1. Anti-ezrin labeling was lost from small regions of the RPE apical surface underlying detachments at P30. Labeling for tight-junction proteins provided a regular array of profiles outlining the periphery of RPE cells in wild-type tissue, however, this pattern was disrupted in the mutant as early as P30. Microarray analysis revealed a broad range of changes in genes involved in metabolism, signaling, cell polarity, and tight-junction organization.

Conclusions

These data indicate changes in this mutant mouse that may provide clues to the underlying mechanisms of SRD in humans. Importantly, these changes include the production of multiple spontaneous detachments without the presence of a retinal tear or significant degeneration of outer segments, changes in the expression of proteins involved in adhesion and fluid transport, and a disrupted organization of RPE tight junctions that may contribute to the formation of focal detachments.

A novel bispecific molecule delivered by recombinant AAV2 suppresses ocular inflammation and choroidal neovascularization

Elevated vascular endothelial growth factor (VEGF) and complement activation are implicated in the pathogenesis of different ocular diseases. The objective of this study was to investigate the hypothesis that dual inhibition of both VEGF and complement activation would confer better protection against ocular inflammation and neovascularization. In this study, we engineered a secreted chimeric VEGF inhibitor domain (VID), a complement inhibitor domain (CID) and a dual inhibitor (ACVP1). Vectors expressing these three inhibitors were constructed and packaged into AAV2 (sextY-F) particles. The expression and secretion of the proteins were validated by Western blot. The effects of these inhibitors expressed from AAV2 vectors were examined in endotoxin-induced uveitis (EIU), experimental autoimmune uveoretinitis (EAU) and choroidal neovascularization (CNV) mouse models. The AAV2 vectors expressing the CID- and ACVP1-attenuated inflammation in EIU and EAU model, whereas the vector expressing VID showed improved retinal structure damaged by EAU, but not affect the infiltration of inflammatory cells in EAU or EIU eyes. Both VID and CID vectors improved laser-induced retinal and choroid/RPE injuries and CNV, whereas ACVP1 vector provided significantly better protection. Our results suggest that gene therapy targeting VEGF and complement components could provide an innovative and long-term strategy for ocular inflammatory and neovascular diseases.

OCT-Angiography for Non-Invasive Monitoring of Neuronal and Vascular Structure in Mouse Retina: Implication for Characterization of Retinal Neurovascular Coupling

PURPOSE

Optical coherence tomography angiography (OCT-A) is a newly developed technique to visualize retinal vasculature non-invasively based on interferometry. Although OCT-A has been used clinically, its applications in small animal studies have been limited. This study is designed to develop and demonstrate the feasibility of a protocol for the use of an en-face OCT-based method to visualize and quantify retinal microvasculature in mice that can be used for in vivo assessment of retina ischemia.

METHODS

A customized algorithm was developed to extract angiographic profiles of the mouse retina from en-face OCT using an unmodified Bioptigen Envisu R-Class OCT imaging system. En-face OCT images were collected in living animals and then compared to images acquired following termination of blood flow to the retina. The images were processed with ImageJ using the raw file importer. The vessel enhancement algorithm was developed based on a combination of local contrast enhancement, Laplacian of Gaussian peak detection and background subtraction methods. For comparison, fluorescein angiography (FA) was performed using Heidelberg Spectralis^® HRA+OCT imaging system.

RESULTS

By vessel enhancement algorithm, we successfully extracted retinal vasculature and quantified retinal vessel branch points, vascular area and vessel lengths with AngioTool. While the retinal neuronal structure could be simultaneously identified and quantified using B-scan and volumetric OCT run in the annular scanning model, the retinal vasculature in OCT-A was dramatically diminished after the animals were sacrificed, indicating en-face OCT-A signal is a measure of the blood flow.

CONCLUSIONS

These studies indicate that a novel approach to extract angiographs from en-face OCT images by utilizing local structure enhancement can be used to provide depth-resolved retinal vasculature distributions. Simultaneous non-invasive analysis of retinal vessels and neurons by OCT-A and OCT may provide a novel approach to characterize retinal ischemia accompanied by neurovascular coupling.

Longitudinal Intravital Imaging of the Retina Reveals Long-term Dynamics of Immune Infiltration and Its Effects on the Glial Network in Experimental Autoimmune Uveoretinitis, without Evident Signs of Neuronal Dysfunction in the Ganglion Cell Layer

A hallmark of autoimmune retinal inflammation is the infiltration of the retina with cells of the innate and adaptive immune system, leading to detachment of the retinal layers and even to complete loss of the retinal photoreceptor layer. As the only optical system in the organism, the eye enables non-invasive longitudinal imaging studies of these local autoimmune processes and of their effects on the target tissue. Moreover, as a window to the central nervous system (CNS), the eye also reflects general neuroinflammatory processes taking place at various sites within the CNS. Histological studies in murine neuroinflammatory models, such as experimental autoimmune uveoretinitis (EAU) and experimental autoimmune encephalomyelitis, indicate that immune infiltration is initialized by effector CD4⁺ T cells, with the innate compartment (neutrophils, macrophages, and monocytes) contributing crucially to tissue degeneration that occurs at later phases of the disease. However, how the immune attack is orchestrated by various immune cell subsets in the retina and how the latter interact with the target tissue under in vivo conditions is still poorly understood. Our study addresses this gap with a novel approach for intravital two-photon microscopy, which enabled us to repeatedly track CD4⁺ T cells and LysM phagocytes during the entire course of EAU and to identify a specific radial infiltration pattern of these cells within the inflamed retina, starting from the optic nerve head. In contrast, highly motile CX3CR1+ cells display an opposite radial motility pattern, toward the optic nerve head. These inflammatory processes induce modifications of the microglial network toward an activated morphology, especially around the optic nerve head and main retinal blood vessels, but do not affect the neurons within the ganglion cell layer. Thanks to the new technology, non-invasive correlation of clinical scores of CNS-related pathologies with immune infiltrate behavior and subsequent tissue dysfunction is now possible. Hence, the new approach paves the way for deeper insights into the pathology of neuroinflammatory processes on a cellular basis, over the entire disease course.

Mice Homozygous for a Deletion in the Glaucoma Susceptibility Locus INK4 Show Increased Vulnerability of Retinal Ganglion Cells to Elevated Intraocular Pressure

A genomic region located on chromosome 9p21 is associated with primary open-angle glaucoma and normal tension glaucoma in genome-wide association studies. The genomic region contains the gene for a long noncoding RNA called CDKN2B-AS, two genes that code for cyclin-dependent kinase inhibitors 2A and 2B (CDKN2A/p16(INK4A) and CDKN2B/p15(INK4B)) and an additional protein (p14(ARF)). We used a transgenic mouse model in which 70 kb of murine chromosome 4, syntenic to human chromosome 9p21, are deleted to study whether this deletion leads to a discernible phenotype in ocular structures implicated in glaucoma. Homozygous mice of this strain were previously reported to show persistent hyperplastic primary vitreous. Fundus photography and optical coherence tomography confirmed that finding but showed no abnormalities for heterozygous mice. Optokinetic response, eletroretinogram, and histology indicated that the heterozygous and mutant retinas were normal functionally and morphologically, whereas glial cells were activated in the retina and optic nerve head of mutant eyes. In quantitative PCR, CDKN2B expression was reduced by approximately 50% in the heterozygous mice and by 90% in the homozygous mice, which suggested that the CDKN2B knock down had no deleterious consequences for the retina under normal conditions. However, compared with wild-type and heterozygous animals, the homozygous mice are more vulnerable to retinal ganglion cell loss in response to elevated intraocular pressure.

Multimodal analysis of ocular inflammation using the endotoxin-induced uveitis mouse model

Endotoxin-induced uveitis (EIU) in rodents is a model of acute Toll-like receptor 4 (TLR4)-mediated organ inflammation, and has been used to model human anterior uveitis, examine leukocyte trafficking and test novel anti-inflammatory therapeutics. Wider adoption has been limited by the requirement for manual, non-specific, cell-count scoring of histological sections from each eye as a measure of disease severity. Here, we describe a comprehensive and efficient technique that uses ocular dissection and multimodal tissue analysis. This allows matched disease scoring by multicolour flow cytometric analysis of the inflammatory infiltrate, protein analysis on ocular supernatants and qPCR on remnant tissues of the same eye. Dynamic changes in cell populations could be identified and mapped to chemokine and cytokine changes over the course of the model. To validate the technique, dose-responsive suppression of leukocyte infiltration by recombinant interleukin-10 was demonstrated, as well as selective suppression of the monocyte (CD11b+Ly6C+) infiltrate, in mice deficient for eitherCcl2orCcr2 Optical coherence tomography (OCT) was used for the first time in this model to allowin vivoimaging of infiltrating vitreous cells, and correlated with CD11b+Ly6G+ counts to provide another unique measure of cell populations in the ocular tissue. Multimodal tissue analysis of EIU is proposed as a new standard to improve and broaden the application of this model.

Tertiary Lymphoid Tissue Forms in Retinas of Mice with Spontaneous Autoimmune Uveitis and Has Consequences on Visual Function

During chronic inflammation, tertiary lymphoid tissue (TLT) can form within an inflamed organ, including the CNS. However, little is known about TLT formation in the neuroretina. In a novel spontaneous autoimmune mouse model of uveitis (R161H), we identified well-organized lymphoid aggregates in the retina and examined them for TLT characteristics. Presence of immune cells, tissue-specific markers, and gene expression patterns typically associated with germinal centers and T follicular helper cells were examined using immunohistochemistry and gene analysis of laser capture microdissected retina. Our data revealed the retinal lymphoid structures contained CD4(+) T cells and B cells in well-defined zonal areas that expressed classic germinal center markers, peanut lectin (agglutinin) and GL-7. Gene expression analysis showed upregulation of T follicular helper cell markers, most notably CXCR5 and its ligand CXCL13, and immunohistochemical analysis confirmed CXCR5 expression, typically associated with CD4(+) T follicular helper cells. Highly organized stromal cell networks, a hallmark of organized lymphoid tissue, were also present. Positive staining for phospho-Zap70 in retina-specific T cells indicated CD4(+) T cells were being activated within these lymphoid structures. CD138(+)/B220(+) plasma cells were detected, suggesting the retinal lymphoid aggregates give rise to functional germinal centers, which produce Abs. Interestingly, eyes with lymphoid aggregates exhibited lower inflammatory scores by fundus examination and a slower initial rate of loss of visual function by electroretinography, compared with eyes without these structures. Our findings suggest that the lymphoid aggregates in the retina of R161H mice represent organized TLT, which impact the course of chronic uveitis.

Modulating of ocular inflammation with macrophage migration inhibitory factor is associated with notch signalling in experimental autoimmune uveitis

The aim of this study was to examine whether macrophage migration inhibitory factor (MIF) could exaggerate inflammatory response in a mouse model of experimental autoimmune uveitis (EAU) and to explore the underlying mechanism. Mutant serotype 8 adeno-associated virus (AAV8) (Y733F)-chicken β-actin (CBA)-MIF or AAV8 (Y733F)-CBA-enhanced green fluorescent protein (eGFP) vector was delivered subretinally into B10.RIII mice, respectively. Three weeks after vector delivery, EAU was induced with a subcutaneous injection of a mixture of interphotoreceptor retinoid binding protein (IRBP) peptide with CFA. The levels of proinflammatory cytokines were detected by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Retinal function was evaluated with electroretinography (ERG). We found that the expression of MIF and its two receptors CD74 and CD44 was increased in the EAU mouse retina. Compared to AAV8.CBA.eGFP-injected and untreated EAU mice, the level of proinflammatory cytokines, the expression of Notch1, Notch4, delta-like ligand 4 (Dll4), Notch receptor intracellular domain (NICD) and hairy enhancer of split-1 (Hes-1) increased, but the ERG a- and b-wave amplitudes decreased in AAV8.CBA.MIF-injected EAU mice. The Notch inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT) reduced the expression of NICD, Hes-1 and proinflammatory cytokines. Further, a MIF antagonist ISO-1 attenuated intraocular inflammation, and inhibited the differentiation of T helper type 1 (Th1) and Th17 in EAU mice. We demonstrated that over-expression of MIF exaggerated ocular inflammation, which was associated with the activation of the Notch signalling. The expression of both MIF and its receptors are elevated in EAU mice. Over-expression of MIF exaggerates ocular inflammation, and this exaggerated inflammation is associated with the activation of the Notch signalling and Notch pathway. Our data suggest that the MIF-Notch axis may play an important role in the pathogenesis of EAU. Both the MIF signalling pathways may be promising targets for developing novel therapeutic interventions for uveitis.

Wnt signaling in age-related macular degeneration: human macular tissue and mouse model

Background

The wingless-type MMTV integration site (Wnt) signaling is a group of signal transduction pathways. In canonical Wnt pathway, Wnt ligands bind to low-density lipoprotein receptor-related protein 5 or 6 (LRP5 or LRP6), resulting in phosphorylation and activation of the receptor. We hypothesize that canonical Wnt pathway plays a role in the retinal lesion of age-related macular degeneration (AMD), a leading cause of irreversible central visual loss in elderly.

Methods

We examined LRP6 phosphorylation and Wnt signaling cascade in human retinal sections and plasma kallistatin, an endogenous inhibitor of the Wnt pathway in AMD patients and non-AMD subjects. We also used the Ccl2^−/−/Cx3cr1^−/−/rd8 and Ccl2^−/−/Cx3cr1^gfp/gfp mouse models with AMD-like retinal degeneration to further explore the involvement of Wnt signaling activation in the retinal lesions in those models and to preclinically evaluate the role of Wnt signaling suppression as a potential therapeutic option for AMD.

Results

We found higher levels of LRP6 (a key Wnt signaling receptor) protein phosphorylation and transcripts of the Wnt pathway-targeted genes, as well as higher beta-catenin protein in AMD macula compared to controls. Kallistatin was decreased in the plasma of AMD patients. Retinal non-phosphorylated-β-catenin and phosphorylated-LRP6 were higher in Ccl2^−/−/Cx3cr1^−/−/rd8 mice than that in wild type. Intravitreal administration of an anti-LRP6 antibody slowed the progression of retinal lesions in Ccl2^−/−/Cx3cr1^−/−/rd8 and Ccl2^−/−/Cx3cr1^gfp/gfp mice. Electroretinography of treated eyes exhibited larger amplitudes compared to controls in both mouse models. A2E, a retinoid byproduct associated with AMD was lower in the treated eyes of Ccl2^−/−/Cx3cr1^−/−/rd8 mice. Anti-LRP6 also suppressed the expression of Tnf-α and Icam-1 in Ccl2^−/−/Cx3cr1^−/−/rd8 retinas.

Conclusions

Wnt signaling may be disturbed in AMD patients, which could contribute to the retinal inflammation and increased A2E levels found in AMD. Aberrant activation of canonical Wnt signaling might also contribute to the focal retinal degenerative lesions of mouse models with Ccl2 and Cx3cr1 deficiency, and intravitreal administration of anti-LRP6 antibody could be beneficial by deactivating the canonical Wnt pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0683-x) contains supplementary material, which is available to authorized users.

Complement anaphylatoxin receptors C3aR and C5aR are required in the pathogenesis of experimental autoimmune uveitis

Recent studies have suggested that reagents inhibiting complement activation could be effective in treating T cell mediated autoimmune diseases such as autoimmune uveitis. However, the precise role of the complement anaphylatoxin receptors (C3a and C5a receptors) in the pathogenesis of autoimmune uveitis remains elusive and controversial. We induced experimental autoimmune uveitis in mice deficient or sufficient in both C3a and C5a receptors and rigorously compared their retinal phenotype using various imaging techniques, including indirect ophthalmoscopy, confocal scanning laser ophthalmoscopy, spectral domain optical coherence tomography, topical endoscopic fundus imaging, and histopathological analysis. We also assessed retinal function using electroretinography. Moreover, we performed Ag-specific T cell recall assays and T cell adoptive transfer experiments to compare pathogenic T cell activity between wild-type and knockout mice with experimental autoimmune uveitis. These experiments showed that C3a receptor/C5a receptor-deficient mice developed much less severe uveitis than did control mice using all retinal examination methods and that these mice had reduced pathogenic T cell responses. Our data demonstrate that both complement anaphylatoxin receptors are important for the development of experimental autoimmune uveitis, suggesting that targeting these receptors could be a valid approach for treating patients with autoimmune uveitis.

Adoptive transfer of immune cells from glaucomatous mice provokes retinal ganglion cell loss in recipients

INTRODUCTION

Several studies have indicated that autoimmune and neuroinflammatory processes contribute to the neurodegeneration of retinal ganglion cells in human glaucoma patients and in animal models. To test the involvement of cellular immune processes in the pathophysiology of retinal ganglion cell degeneration in vivo, we carried out adoptive transfer experiments from two independent genetic mouse models of glaucoma into normal recipient mice.

RESULTS

Our findings indicate that transfer results in a progressive loss of retinal ganglion cells and their axons despite normal intraocular pressure in recipient mice. Signs of pan-retinal inflammation were not detected. Similar findings were obtained following transfer of isolated T-lymphocytes, but not after transfer of splenocytes from immune deficient glaucomatous mice. Transferred lymphocytes were detected integrated in the spleen and in the retinal ganglion cell layer of recipient animals, albeit at very low frequencies. Furthermore, we observed cell-cell interaction between transferred T-cells and recipient microglia along with focal microglial activation in recipient eyes.

CONCLUSION

This study demonstrates that the pathophysiology of glaucomatous degeneration in the tested animal models includes T-cell mediated events that are capable of causing loss of healthy retinal ganglion cells.

Dual Function of the IRF8 Transcription Factor in Autoimmune Uveitis: Loss of IRF8 in T Cells Exacerbates Uveitis, Whereas Irf8 Deletion in the Retina Confers Protection

IFN regulatory factor 8 (IRF8) is constitutively expressed in monocytes and B cells and plays a critical role in the functional maturation of microglia cells. It is induced in T cells following Ag stimulation, but its functions are less well understood. However, recent studies in mice with T cell-specific Irf8 disruption under direction of the Lck promoter (LCK-IRF8KO) suggest that IRF8 directs a silencing program for Th17 differentiation, and IL-17 production is markedly increased in IRF8-deficient T cells. Paradoxically, loss of IRF8 in T cells has no effect on the development or severity of experimental autoimmune encephalomyelitis (EAE), although exacerbating colitis in a mouse colitis model. In contrast, mice with a macrophage/microglia-specific Irf8 disruption are resistant to EAE, further confounding our understanding of the roles of IRF8 in host immunity and autoimmunity. To clarify the role of IRF8 in autoimmune diseases, we have generated two mouse strains with targeted deletion of Irf8 in retinal cells, including microglial cells and a third mouse strain with targeted Irf8 deletion in T cells under direction of the nonpromiscuous, CD4 promoter (CD4-IRF8KO). In contrast to the report that IRF8 deletion in T cells has no effect on EAE, experimental autoimmune uveitis is exacerbated in CD4-IRF8KO mice and disease enhancement correlates with significant expansion of Th17 cells and a reduction in T regulatory cells. In contrast to CD4-IRF8KO mice, Irf8 deletion in retinal cells confers protection from uveitis, underscoring divergent and tissue-specific roles of IRF8 in host immunity. These results raise a cautionary note in the context of therapeutic targeting of IRF8.

In vivo multi-modal imaging of experimental autoimmune uveoretinitis in transgenic reporter mice reveals the dynamic nature of inflammatory changes during disease progression

Background

Experimental autoimmune uveoretinitis (EAU) is a widely used experimental animal model of human endogenous posterior uveoretinitis. In the present study, we performed in vivo imaging of the retina in transgenic reporter mice to investigate dynamic changes in exogenous inflammatory cells and endogenous immune cells during the disease process.

Methods

Transgenic mice (C57Bl/6 J Cx₃cr1^GFP/+, C57Bl/6 N CD11c-eYFP, and C57Bl/6 J LysM-eGFP) were used to visualize the dynamic changes of myeloid-derived cells, putative dendritic cells and neutrophils during EAU. Transgenic mice were monitored with multi-modal fundus imaging camera over five time points following disease induction with the retinal auto-antigen, interphotoreceptor retinoid binding protein (IRBP_1–20). Disease severity was quantified with both clinical and histopathological grading.

Results

In the normal C57Bl/6 J Cx₃cr1^GFP/+ mouse Cx₃cr1-expressing microglia were evenly distributed in the retina. In C57Bl/6 N CD11c-eYFP mice clusters of CD11c-expressing cells were noted in the retina and in C57Bl/6 J LysM-eGFP mice very low numbers of LysM-expressing neutrophils were observed in the fundus. Following immunization with IRBP_1–20, fundus examination revealed accumulations of Cx₃cr1-GFP⁺ myeloid cells, CD11c-eYFP⁺ cells and LysM-eGFP⁺ myelomonocytic cells around the optic nerve head and along retinal vessels as early as day 14 post-immunization. CD11c-eYFP⁺ cells appear to resolve marginally earlier (day 21 post-immunization) than Cx₃cr1-GFP⁺ and LysM-eGFP⁺ cells. The clinical grading of EAU in transgenic mice correlated closely with histopathological grading.

Conclusions

These results illustrate that in vivo fundus imaging of transgenic reporter mice allows direct visualization of various exogenously and endogenously derived leukocyte types during EAU progression. This approach acts as a valuable adjunct to other methods of studying the clinical course of EAU.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0235-6) contains supplementary material, which is available to authorized users.

Optical coherence tomography based microangiography for quantitative monitoring of structural and vascular changes in a rat model of acute uveitis in vivo: a preliminary study

Uveitis models in rodents are important in the investigation of pathogenesis in human uveitis and the development of appropriate therapeutic strategies for treatment. Quantitative monitoring of ocular inflammation in small animal models provides an objective metric to assess uveitis progression and/or therapeutic effects. We present a new application of optical coherence tomography (OCT) and OCT-based microangiography (OMAG) to a rat model of acute anterior uveitis induced by intravitreal injection of a killed mycobacterial extract. OCT/OMAG is used to provide noninvasive three-dimensional imaging of the anterior segment of the eyes prior to injection (baseline) and two days post-injection (peak inflammation) in rats with and without steroid treatments. OCT imaging identifies characteristic structural and vascular changes in the anterior segment of the inflamed animals when compared to baseline images. Characteristics of inflammation identified include anterior chamber cells, corneal edema, pupillary membranes, and iris vasodilation. In contrast, no significant difference from the control is observed for the steroid-treated eye. These findings are compared with the histology assessment of the same eyes. In addition, quantitative measurements of central corneal thickness and iris vessel diameter are determined. This pilot study demonstrates that OCT-based microangiography promises to be a useful tool for the assessment and management of uveitis in vivo.

Mouse Models of Experimental Autoimmune Uveitis: Comparative Analysis of Adjuvant-Induced vs Spontaneous Models of Uveitis

Mouse models of experimental autoimmune uveitis (EAU) mimic unique features of human uveitis, and serve as a template for preclinical study. The "classical" EAU model is induced by active immunization of mice with the retinal protein IRBP in adjuvant, and has proved to be a useful tool to study basic mechanisms and novel therapy in human uveitis. Several spontaneous models of uveitis induced by autoreactive T cells targeting on IRBP have been recently developed in IRBP specific TCR transgenic mice (R161H) and in AIRE(-/-) mice. The "classical" immunization-induced EAU exhibits acute ocular inflammation with two distinct patterns: (i) severe monophasic form with extensive destruction of the retina and rapid loss of visual function, and (ii) lower grade form with an acute onset followed by a prolonged chronic phase of disease. The spontaneous models of uveitis in R161H and AIRE(-/-) mice have a gradual onset and develop chronic ocular inflammation that ultimately leads to retinal degeneration, along with a progressive decline of visual signal. The adjuvant-dependent model and adjuvant-free spontaneous models represent distinct aspects and/or various forms of human uveitis. This review will discuss and compare clinical manifestations, pathology as well as visual function of the retina in the different models of uveitis, as measured by fundus imaging and histology, optical coherence tomography (OCT) and electroretinography (ERG).

Oral delivery of ACE2/Ang-(1-7) bioencapsulated in plant cells protects against experimental uveitis and autoimmune uveoretinitis

Hyperactivity of the renin-angiotensin system (RAS) resulting in elevated Angiotensin II (Ang II) contributes to all stages of inflammatory responses including ocular inflammation. The discovery of angiotensin-converting enzyme 2 (ACE2) has established a protective axis of RAS involving ACE2/Ang-(1-7)/Mas that counteracts the proinflammatory and hypertrophic effects of the deleterious ACE/AngII/AT1R axis. Here we investigated the hypothesis that enhancing the systemic and local activity of the protective axis of the RAS by oral delivery of ACE2 and Ang-(1-7) bioencapsulated in plant cells would confer protection against ocular inflammation. Both ACE2 and Ang-(1-7), fused with the non-toxic cholera toxin subunit B (CTB) were expressed in plant chloroplasts. Increased levels of ACE2 and Ang-(1-7) were observed in circulation and retina after oral administration of CTB-ACE2 and Ang-(1-7) expressing plant cells. Oral feeding of mice with bioencapsulated ACE2/Ang-(1-7) significantly reduced endotoxin-induced uveitis (EIU) in mice. Treatment with bioencapsulated ACE2/Ang-(1-7) also dramatically decreased cellular infiltration, retinal vasculitis, damage and folding in experimental autoimmune uveoretinitis (EAU). Thus, enhancing the protective axis of RAS by oral delivery of ACE2/Ang-(1-7) bioencapsulated in plant cells provide an innovative, highly efficient and cost-effective therapeutic strategy for ocular inflammatory diseases.

Dose-dependent retinal changes following sodium iodate administration: application of spectral-domain optical coherence tomography for monitoring of retinal injury and endogenous regeneration

BACKGROUND

The purpose of this study was to demonstrate the progression of acute retinal injury by correlating histological sections with in vivo spectral-domain optical coherence tomography (SD-OCT) images.

METHODS

Male C57BL/6 mice were treated intravenously with two different sodium iodate (NaIO3) doses (35 mg/kg or 15 mg/kg). In vivo SD-OCT was performed up to 3 months post-injury. Ex vivo retinal histology, TUNEL and IsolectinB4 immunostaining were also conducted. Quantitative comparison of histopathological images and SD-OCT images was performed.

RESULTS

SD-OCT examination revealed that administration of 35 mg/kg NaIO3 was associated with progressive and irreversible retinal degeneration. On day 3 post-injury, we found numerous apoptotic cells in the outer nuclear layer (ONL) that strongly corresponded to hyper-reflective areas in the SD-OCT images. At 7 d post-injury, SD-OCT images showed irregular-shaped patterns of hyper-reflectivity in the retinal pigment epithelium (RPE) that corresponded with the accumulation of macrophages phagocytosing melanin granules and cell debris. Additionally, we documented hyper-reflective opacities in the vitreous that were most numerous at 7 d. At 3 months post-injury, the neurosensory retina was significantly thinner, predominantly due to progressive photoreceptor (PR) loss. In contrast, administration of 15 mg/kg NaIO3 did not induce hyper-reflectivity of ONL in SD-OCT images, which indicates a lack of massive PR cell death. At 3 months post-injury, SD-OCT images showed the complete restoration of outer retina lamination and restoration of hyper-reflective structural bands. Histological assessment of retinas acquired after the last SD-OCT imaging session revealed complete regeneration of the RPE and considerable improvement of PR architecture.

CONCLUSIONS

Our findings showed the high level of effectiveness of SD-OCT imaging for monitoring dynamic changes in retinal morphology following acute retinal injury. Moreover, we demonstrated for the first time that SD-OCT can be used to non-invasively detect regeneration in the damaged retina.

Evaluation of mouse experimental autoimmune uveoretinitis by spectral domain optical coherence tomography

AIMS

To evaluate the efficacy of spectral domain optical coherence tomography (SD-OCT) in monitoring the development of mouse experimental autoimmune uveoretinitis (EAU) as an animal model of endogenous uveitis, and to develop an OCT-based grading system for EAU severity.

METHODS

C57BL/6 mice were immunised with human interphotoreceptor retinoid-binding protein (amino acid sequence 1-20) peptide and complete Freund's adjuvant to induce EAU. The development of EAU was monitored by SD-OCT serially throughout the disease course, and the images were graded from 1 to 4 and compared with the clinical and histopathological grades.

RESULTS

SD-OCT images depicted retinal lamella structures including the inner segment/outer segment (IS/OS) line in normal mice. Retinal structural changes were observed on SD-OCT images in mice that developed EAU clinically scored as grade 1 or higher, which precisely corresponded to the pathological findings. The SD-OCT images of EAU were graded as follows: grade 1, a few infiltrating cells in the vitreous and retina; grade 2, increased vitreous cells, retinal vasculitis, and granulomatous lesion; grade 3, cell infiltration into the whole retina, disappearance of IS/OS line, and destruction of the retinal layer structure; and grade 4, disappearance of the outer retina. The SD-OCT grade of EAU based on these criteria correlated significantly with both the clinical grade (R(2)=0.282, p<0.005) and histopathological grade (R(2)=0.846, p<0.0001).

CONCLUSIONS

SD-OCT is useful for evaluating the development and severity of mouse EAU. The SD-OCT scoring system we developed accurately reflects clinical and histopathological changes.

Inflammatory demyelination induces glia alterations and ganglion cell loss in the retina of an experimental autoimmune encephalomyelitis model

Background

Multiple sclerosis (MS) is often accompanied by optic nerve inflammation. And some patients experience permanent vision loss. We examined if the grade of optic nerve infiltration and demyelination affects the severity of clinical signs in an experimental autoimmune encephalomyelitis (EAE) model. The loss of retinal ganglion cells (RGC) and alterations in glia activity were also investigated.

Methods

C57BL/6 mice were immunized with peptide MOG_35-55 in complete Freund’s adjuvant (CFA) and controls received PBS in CFA. Then 23 days post immunization eyes were prepared for flatmounts and stained with Nissl to evaluated neuronal density. Clinical EAE symptoms as well as cell infiltration and demyelination in the optic nerve were examined. Retinal sections were stained with hematoxylin and eosin and silver stain. Immunohistochemistry was used to label RGCs (Brn-3a), apoptotic cells (caspase 3), macroglia (glial fibrillary acidic protein (GFAP)), microglia (Iba1), macrophages (F 4/80) and interleukin-6 (IL-6) secretion.

Results

EAE symptoms started at day 8 and peaked at day 15. Cell infiltrations (P = 0.0047) and demyelination (P = 0.0018) of EAE nerves correlated with the clinical score (r > 0.8). EAE led to a significant loss of RGCs (P< 0.0001). Significantly more caspase 3⁺ cells were noted in these animals (P = 0.0222). They showed an increased expression of GFAP (P< 0.0002) and a higher number of microglial cells (P< 0.0001). Also more macrophages and IL-6 secretion were observed in EAE mice.

Conclusions

MOG immunization leads to optic neuritis and RGC loss. EAE severity is related to the severity of optic nerve inflammation and demyelination. EAE not only affects activation of apoptotic signals, but also causes a glial response in the retina.

Comparative analysis of induced vs. spontaneous models of autoimmune uveitis targeting the interphotoreceptor retinoid binding protein

Animal models of autoimmunity to the retina mimic specific features of human uveitis, but no model by itself reproduces the full spectrum of human disease. We compared three mouse models of uveitis that target the interphotoreceptor retinoid binding protein (IRBP): (i) the "classical" model of experimental autoimmune uveitis (EAU) induced by immunization with IRBP; (ii) spontaneous uveitis in IRBP T cell receptor transgenic mice (R161H) and (iii) spontaneous uveitis in Autoimmune Regulator (AIRE)(-/-) mice. Disease course and severity, pathology and changes in visual function were studied using fundus imaging and histological examinations, optical coherence tomography and electroretinography. All models were on the B10.RIII background. Unlike previously reported, IRBP-induced EAU in B10.RIII mice exhibited two distinct patterns of disease depending on clinical scores developed after onset: severe monophasic with extensive destruction of the retina and rapid loss of visual signal, or lower grade with a prolonged chronic phase culminating after several months in retinal degeneration and loss of vision. R161H and AIRE(-/-) mice spontaneously developed chronic progressive inflammation; visual function declined gradually as retinal degeneration developed. Spontaneous uveitis in R161H mice was characterized by persistent cellular infiltrates and lymphoid aggregation, whereas AIRE(-/-) mice characteristically developed multi-focal infiltrates and severe choroidal inflammation. These data demonstrate variability and unique distinguishing features in the different models of uveitis, suggesting that each one can represent distinct aspects of uveitis in humans.