Oliver W. Gramlich

Retinal optical coherence tomography (OCT) in rodent models has been used to longitudinally image retinal changes, to define end points for more costly or time-consuming experiments, and to better understand the pathophysiology underlying OCT findings in human diseases. No standardization of rodent OCT reporting currently exists. Here, we aim to establish consensus recommendation for reporting results from retinal OCT studies in rodents. Initial recommendations were developed based on the APOSTEL criteria for quantitative OCT reporting in humans by a core team. Using a modified Delphi process, an expert panel of rodent OCT researchers (N = 31) and the wider scientific community discussed, refined, and voted on these initial recommendations. The list of recommendations was then revised and approved by the expert panel. The final 7-point checklist includes reporting recommendations regarding the study protocol, OCT device, acquisition settings and modifications, scanning protocol, funduscopic imaging, postacquisition data selection and image data analyses, and qualitative and quantitative results. With a median agreement score of 3 or 4 out of 4, the scientific community agreed with these recommendations. After revisions, the expert panel accepted the final recommendations. The Advised Protocol for OCT Study Terminology and Elements for reporting OCT studies in rodents (APOSTEL-R) originates from an expert consensus. They will provide guidance throughout the experimental process and will contribute to the standardization and quality improvement of preclinical OCT studies.

Optic neuritis (ON), or inflammation of the optic nerve, is a common presenting symptom of demyelinating neuroinflammatory conditions that result in significant, subacute vision loss. Given its association with visual impairment and varying extent of visual recovery, ON has been recognized as a significant health burden with a need for new therapeutic strategies to improve long-term visual outcomes. Among the resources utilized to study ON, animal models have emerged as powerful tools to examine the underlying pathophysiology and the effectiveness of proposed therapies. In the current review, we discuss the functional and structural phenotypes related to ON in currently used mouse models, and summarize how the pathophysiology and visual phenotype of the myelin oligodendrocyte glycoprotein 35–55 (MOG_{35 − 55}) experimental autoimmune encephalomyelitis (EAE) mouse model recapitulates clinical features of multiple sclerosis (MS), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), and neuromyelitis optica spectrum disorder (NMOSD). The location of ON and the amount of visual recovery in the EAE model most closely resembles MS and NMOSD. However, we propose that the MOG_{35 − 55}-induced EAE model of ON is primarily a MOGAD model given its similarity in pathophysiology, spinal cord demyelination pattern, and the degree of vision loss, retinal nerve fiber layer (RNFL) swelling, and disc edema. Overall, the MOG_{35 − 55}-induced EAE animal model demonstrates overlapping features of autoimmune demyelinating conditions and serves as a comprehensive tool to further our understanding of visual impairment in all three conditions.

Purpose: Experimental autoimmune encephalomyelitis (EAE) scoring, the most commonly used primary outcome metric for an in vivo model of multiple sclerosis (MS), is highly variable and subjective. Here we explored the use of visual biomarkers in EAE as more objective and clinically relevant primary outcomes. Methods: Motor impairment in myelin oligodendrocyte glycoprotein-immunized C57BL/6J mice was quantified using a five-point EAE grading scale. Pattern electroretinography (pERG) and retinal ganglion cell/inner plexiform layer (RGC/IPL) complex thickness were measured 60 days after induction. Optic nerve histopathology was analyzed at endpoint. Results: EAE mice displayed motor impairments ranging from mild to severe. Significant correlations were seen between pERG amplitude and last EAE score, mean EAE score, and cumulative EAE score. Optical coherence tomography (OCT) analysis demonstrated a significant correlation between thinning of the RGC/IPL complex and both EAE score and pERG amplitude. Optic nerve histopathology showed significant correlations between demyelination and cumulative EAE score, pERG amplitude, and RGC/IPL complex thickness, as well as between immune cell infiltration and cumulative EAE score, pERG amplitude, and RGC/IPL complex thickness in EAE mice. Conclusions: Unlike EAE scoring, pERG and OCT show direct measurement of retinal structure and function. Therefore we conclude that visual outcomes are well suited as a direct assessment of optic nerve involvement in this EAE model of MS while also being indicative of motor impairment. Translational Relevance: Standardizing directly translatable measurements as primary outcome parameters in the murine EAE model could lead to more rapid and relevant testing of new therapeutic approaches for mitigating MS.

Experimental autoimmune encephalomyelitis (EAE) scoring, the most commonly used primary outcome metric for an in vivo model of multiple sclerosis (MS), is highly variable and subjective. Here, we explored the use of visual biomarkers in EAE as more objective and clinically relevant primary outcomes. Motor-sensory impairment in myelin oligodendrocyte glycoprotein-immunized C57BL/6J mice was quantified using a 5-point EAE scoring scheme. Pattern electroretinography (pERG) and retinal ganglion cell / inner plexiform layer (RGC/IPL) complex thickness were measured 60 days after induction. Optic nerve histopathology was analyzed at endpoint. EAE mice displayed motor-sensory impairments ranging from mild to severe. Significant correlations were seen between pERG amplitude and last EAE score, mean EAE score, and cumulative EAE score. Optical coherence tomography (OCT) analysis demonstrated a significant correlation between thinning of the RGC/IPL complex and both the cumulative EAE score and the pERG amplitude. Optic nerve histopathology showed significant correlations between demyelination and cumulative EAE score, pERG amplitude, and RGC/IPL complex thickness, as well as between immune cell infiltration and cumulative EAE score, pERG amplitude, and RGC/IPL complex thickness in EAE mice. Unlike EAE scoring, pERG and OCT show direct measurement of retinal structure and function. Therefore, we conclude that visual outcomes are well-suited as a direct assessment of optic nerve involvement in this EAE model of MS, while also being indicative of motor-sensory impairment. Standardizing parameters could lead to a more rapid and robust model for testing new therapeutic approaches for mitigating MS by utilizing deep learning and artificial intelligence.

Introduction: Optic neuritis (ON) is often an early sign of multiple sclerosis (MS), and recent studies show a link between HIF-1 pathway activation and inflammation. This study aimed to determine if inhibition of the HIF-1 pathway using the HIF-1a antagonist acriflavine (ACF) can reduce clinical progression and rescue the ocular phenotype in an experimental autoimmune encephalomyelitis (EAE) ON model.Methods: EAE-related ON was induced in 60 female C57BL/6J mice by immunization with MOG33-55, and 20 EAE mice received daily systemic injections of ACF at 5 mg/kg. Changes in the visual function and structure of ACF-treated EAE mice were compared to those of placebo-injected EAE mice and naïve control mice.Results: ACF treatment improved motor–sensory impairment along with preserving visual acuity and optic nerve function. Analysis of retinal ganglion cell complex alsoshowed preserved thickness correlating with increased survival of retinal ganglion cells and their axons. Optic nerve cell infiltration and magnitude of demyelination were decreased in ACF-treated EAE mice. Subsequent in vitro studies revealed improvements not only attributed to the inhibition of HIF-1 butalso to previously unappreciated interaction with the eIF2a/ATF4 axis in the unfolded protein response pathway.Discussion: This study suggests that ACF treatment is effective in an animal model of MS via its pleiotropic effects on the inhibition of HIF-1 and UPR signaling, and it may be a viable approach to promote rehabilitation in MS.

Acute optic neuritis (ON) is a common cause of vision loss and is often associated with multiple sclerosis (MS). Cholesterol recycling has been identified as a key limiting factor in recovery after demyelination events. Thus, the purpose of our study was to determine if the augmentation of cholesterol transport by gentisic acid (GA) benefits retinal ganglion cell (RGC) development and myelination in organoid systems and enables the recovery of the ocular phenotype upon systemic GA treatment in a MOG-induced experimental autoimmune encephalomyelitis (EAE) ON model. The retinal organoids treated with GA demonstrate an accelerated maturation when compared to the conventionally derived organoids, which was evidenced by the improved organization of Brn3a-GFP⁺RGC and increased synaptogenesis. A GA supplementation in brain organoids leads to a 10-fold increase in NG2 and Olig2 expression. Weekly GA injections of EAE mice significantly lessened motor-sensory impairment, protected amplitudes in pattern electroretinogram recordings, and preserved visual acuity over the study period of 56 days. Furthermore, GA-treated EAE mice revealed diminished GCL/IPL complex thinning when compared to the untreated EAE mice. An optic nerve histopathology revealed less severe grades of demyelination in the GA-treated EAE cohort and fewer infiltrating cells were observed. Interventions to improve cholesterol homeostasis may be a viable approach to promoting the rehabilitation of MS patients.

Neuroinflammation significantly contributes to the pathophysiology of several neurodegenerative diseases. This is also the case in glaucoma and may be a reason why many patients suffer from progressive vision loss despite maximal reduction in intraocular pressure. Pioglitazone is an agonist of the peroxisome proliferator-activated receptor gamma (PPARγ) whose pleiotrophic activities include modulation of cellular energy metabolism and reduction in inflammation. In this study we employed the DBA2/J mouse model of glaucoma with chronically elevated intraocular pressure to investigate whether oral low-dose pioglitazone treatment preserves retinal ganglion cell (RGC) survival. We then used an inducible glaucoma model in C57BL/6J mice to determine visual function, pattern electroretinographs, and tracking of optokinetic reflex. Our findings demonstrate that pioglitazone treatment does significantly protect RGCs and prevents axonal degeneration in the glaucomatous retina. Furthermore, treatment preserves and partially reverses vision loss in spite of continuously elevated intraocular pressure. These data suggest that pioglitazone may provide treatment benefits for those glaucoma patients experiencing continued vision loss.

Glaucoma is a multifactorial disease resulting in progressive vision loss due to retinal ganglion cell (RGC) dysfunction and death. Early events in the pathobiology of the disease include oxidative, metabolic, or mechanical stress that acts upon RGC, causing these to rapidly release danger signals, including extracellular ATP, resulting in micro- and macroglial activation and neuroinflammation. Danger signaling also leads to the formation of inflammasomes in the retina that enable maturation of proinflammatory cytokines such IL-1β and IL-18. Chronic neuroinflammation can have directly damaging effects on RGC, but it also creates a proinflammatory environment and compromises the immune privilege of the retina. In particular, continuous synthesis of proinflammatory mediators such as TNFα, IL-1β, and anaphylatoxins weakens the blood–retina barrier and recruits or activates T-cells. Recent data have demonstrated that adaptive immune responses strongly exacerbate RGC loss in animal models of the disease as T-cells appear to target heat shock proteins displayed on the surface of stressed RGC to cause their apoptotic death. It is possible that dysregulation of these immune responses contributes to the continued loss of RGC in some patients.

Glaucoma is a leading cause of irreversible blindness worldwide, and increased intraocular pressure (IOP) is a major risk factor. We aimed to determine if early functional and molecular differences in the glaucomatous retina manifest before significant retinal ganglion cell (RGC) loss is apparent. Adenoviral vectors expressing a pathogenic form of myocilin (Ad5.MYOC) were used to induce IOP elevation in C57BL/6 mice. IOP and pattern electroretinograms (pERG) were recorded, and retinas were prepared for RNA sequencing, immunohistochemistry, or to determine RGC loss. Ocular injection of Ad5.MYOC leads to reliable IOP elevation, resulting in significant loss of RGC after nine weeks. A significant decrease in the pERG amplitude was evident in eyes three weeks after IOP elevation. Retinal gene expression analysis revealed increased expression for 291 genes related to complement cascade, inflammation, and antigen presentation in hypertensive eyes. Decreased expression was found for 378 genes associated with the γ-aminobutyric acid (GABA)ergic and glutamatergic systems and axon guidance. These data suggest that early functional changes in RGC might be due to reduced GABA_A receptor signaling and neuroinflammation that precedes RGC loss in this glaucoma model. These initial changes may offer new targets for early detection of glaucoma and the development of new interventions.

Purpose: The purpose of this study was to determine mesenchymal stem cell (MSC) therapy efficacy on rescuing the visual system in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS) and to provide new mechanistic insights. Methods: EAE was induced in female C57BL6 mice by immunization with myelin oligodendrocyte glycoprotein (MOG)_35–55, complete Freund's adjuvant, and pertussis toxin. The findings were compared to sham-immunized mice. Half of the EAE mice received intraperitoneally delivered stem cells (EAE + MSC). Clinical progression was monitored according to a five-point EAE scoring scheme. Pattern electroretinogram (PERG) and retinal nerve fiber layer (RNFL) thickness were measured 32 days after induction. Retinas were harvested to determine retinal ganglion cell (RGC) density and prepared for RNA-sequencing. Results: EAE animals that received MSC treatment seven days after EAE induction showed significantly lower motor-sensory impairment, improvement in the PERG amplitude, and preserved RNFL. Analysis of RNA-sequencing data demonstrated statistically significant differences in gene expression in the retina of MSC-treated EAE mice. Differentially expressed genes were enriched for pathways involved in endoplasmic reticulum stress, endothelial cell differentiation, HIF-1 signaling, and cholesterol transport in the MSC-treated EAE group. Conclusions: Systemic MSC treatment positively affects RGC function and survival in EAE mice. Better cholesterol handling by increased expression of Abca1, the cholesterol efflux regulatory protein, paired with the resolution of HIF-1 signaling activation might explain the improvements seen in PERG of EAE animals after MSC treatment. Translational Relevance: Using MSC therapy in a mouse model of MS, we discovered previously unappreciated biochemical pathways associated with RGC neuroprotection, which have the potential to be pharmacologically targeted as a new treatment regimen.