Assessing Functional Deficits at Optic Neuritis Onset in EAE Mice Using Manganese-Enhanced MRI (MEMRI) and Diffusion fMRI

Optic neuritis: ON) is frequently a first sign of multiple sclerosis: MS), which is an inflammatory demyelinative disease of the central nerve system: CNS), including brain, optic nerve, and spinal cord. Investigating ON provides an approach to improve MS diagnosis and treatment monitoring. Experimental autoimmune encephalomyelitis: EAE) is a widely used animal model of MS and exhibits pathologies similar to the human disease. Magnetic resonance imaging: MRI) is a non-invasive tool to detect disease progress and as a standard diagnose procedure for MS in the clinic. In biological samples, the hydrogen nuclei are used to produce the MR signal due to its abundance in water and fat. As a result of tissue microstructural differences, 1H nuclei exhibit tissue-specific and pathology-specific relaxation and diffusion properties, which are reflected in the resulting MR image contrast. Therefore, the pathologies of MS, such as inflammation, demyelination, and axonal injury can be detected using different MR-related tools, including T1- and T2-weighted imaging, diffusion-weighted imaging, and diffusion tensor imaging, and so on. Importantly, direct non-invasive assessment of functional deficits could be important for understanding pathology mechanisms or provide a useful bio-index to validate treatment strategies. In this dissertation, manganese-enhanced MRI: MEMRI) and diffusion fMRI were introduced to explore the functional deficits, including axonal transport disruption and axon-activity dysfunction, at optic neuritis onset in EAE mice

Assessing Optic Neuritis in a Mouse Model of Multiple Sclerosis with Diffusion MR Imaging

Optic neuritis (ON) is an early manifestation in patients of multiple sclerosis (MS), typically resulting in visual dysfunction. The inflammatory demyelination of the optic nerve in ON closely resembles pathologies of the rest of central nervous system (CNS) white matter in MS. Since accumulated axonal degeneration in MS was considered as the potential cause leading to permanent disability, correlating optic nerve pathology and visual function in ON could be a model system to investigate the relationship between functional outcome and neuropathology. It may also present a new way to reflect the disease progression in MS. Various MR techniques have been used to assess inflammation (inflammatory cell infiltration and vasogenic edema) of ON, but rarely demonstrated the ability to image cellularity changes non-invasively. Diffusion MRI measures the Brownian motion of water molecules in the microstructure of biological tissues. Diffusion tensor imaging (DTI) holds the promise to provide a specific biomarker of axonal injury and demyelination in CNS white matter by axial diffusivity (the diffusion parallel to white matter fibers) and radial diffusivity (the diffusion perpendicular to white matter fibers), respectively. However, DTI assumes a single diffusion tensor model and thus takes an average of varied diffusion components. In contrast, our recently developed diffusion basis spectrum imaging (DBSI) resolves the complex diffusion components and provides relatively accurate directional diffusivities and diffusion component fractions, relating to the detail and accurate pathological picture of the disease or injury. In the current work, in vivo 25-direction DBSI was applied to the optic nerve of mice with experimental autoimmune encephalomyelitis (EAE), an animal model of MS, with visual impairment at onset of ON. Our results demonstrate that inflammation correlated well with visual impairment in acute ON. DBSI successfully detected inflammatory cell infiltration and optic nerve white matter pathology in EAE that was consistent with histology, supporting the capability of DBSI to quantify increased cellularity, axonal injury and myelin damage in the optic nerve of EAE mice

Development of a novel model of optic neuritis to assess neuroprotective and repair strategies in multiple sclerosis

PhDMultiple sclerosis (MS) is a putative autoimmune disease of the central nervous system (CNS), which often affects the optic nerve pathway. Optic neuritis (ON) is a clinical feature of MS that can cause loss of vision due to conduction block and demyelination. Visual function may not recover due to axonal loss in the optic nerve and subsequent loss of retinal ganglion cells (RGC) in the retina. The visual system is the most accessible and best studied part of the CNS and provides an ideal target to monitor the efficacy of strategies aimed at neuroprotection and repair. A C57BL/6 mouse expressing a T cell receptor (TCR) transgene specific for 35-55 residues of myelin oligodendrocyte glycoprotein (MOG), which develops ON spontaneously (approximately 5%) was characterised and an immunising protocol developed with a combination of immune adjuvants (Pertussis toxin, MOG-specific Z12 monoclonal antibody) to give a high incidence of disease. ON is associated with extensive axonal loss in the optic nerve and RGC loss in the retina. These animals were crossed with C57BL/6.Thy1 CFP mice, which express cyan fluorescent protein (CFP) under control of a Thy1 promoter that limits expression of CFP to the RGC in the eye. The resultant MOGTCRxThy1CFP mice develop ON leading to neuronal loss that can be monitored longitudinally in “real-time” in the living animal using techniques that correlate with studies undertaken in humans (visually evoked potentials, scanning laser ophthalmoscopy and optical coherence tomography). These techniques were used in the MOGTCRxThy1CFP to study neuroprotective and repair therapies for their potential in human trials. This novel model of optic neuritis will be invaluable for the study of neuroprotective and repair strategies in autoimmune diseases and offers a refinement of previous models of MS, such as “classical” EAE

Optic neuritis

Acute optic neuritis is the most common optic neuropathy affecting young adults. Exciting developments have occurred over the past decade in understanding of optic neuritis pathophysiology, and these developments have been translated into treatment trials. In its typical form, optic neuritis presents as an inflammatory demyelinating disorder of the optic nerve, which can be associated with multiple sclerosis. Atypical forms of optic neuritis can occur, either in association with other inflammatory disorders or in isolation. Differential diagnosis includes various optic nerve and retinal disorders. Diagnostic investigations include MRI, visual evoked potentials, and CSF examination. Optical coherence tomography can show retinal axonal loss, which correlates with measures of persistent visual dysfunction. Treatment of typical forms with high-dose corticosteroids shortens the period of acute visual dysfunction but does not affect the final visual outcome. Atypical forms can necessitate prolonged immunosuppressive regimens. Optical coherence tomography and visual evoked potential measures are suitable for detection of neuroaxonal loss and myelin repair after optic neuritis. Clinical trials are underway to identify potential neuroprotective or remyelinating treatments for acutely symptomatic inflammatory demyelinating CNS lesions

Clinical phenotypes, radiological characterisation, therapeutic responses, and outcomes in myelin oligodendrocyte glycoprotein antibody-associated demyelination

Background: Myelin oligodendrocyte glycoprotein (MOG) is a putative candidate antigen in demyelination. Aims: We sought to identify the clinical phenotypes, radiological characteristics, treatment responses, and outcomes in MOG antibody-associated demyelination. Methods: We performed a flow cytometry live cell based assay to detect MOG antibodies in adults with demyelination; undertook blinded neuroradiological assessment on 50 patients with first episode optic neuritis (ON) due to multiple sclerosis (MS), MOG, or aquaporin-4 (AQP4) antibodies; and evaluated treatment responses and outcomes in 33 children and 26 adults with relapsing MOG antibody-associated demyelination. Results: MOG antibodies were strongly associated with recurrent and bilateral ON (BON) with optic disc swelling [9/23 adults with AQP4 antibody-negative neuromyelitis optica spectrum disorder v.0/52 controls (p<0.001)]. There were low rates of MOG antibody-positivity in Australian MS (1/76) and Japanese opticospinal MS (2/50). Radiologically, bilateral longitudinally extensive optic nerve involvement was more common in MOG and AQP4-ON than MS-ON. MOG-ON exhibited anterior and AQP4-ON exhibited posterior visual pathway involvement. ON was dominant at initial presentation [BON 32%, unilateral (UON) 22%] and throughout the clinical course (BON 19%, UON 34%) in relapsing MOG antibody-associated demyelination. Patients were steroid responsive but 70% of episodes relapsed, especially at prednisone doses <10 mg daily or within 2 months of cessation. Immunotherapy, including maintenance prednisone (P=0.0004), intravenous immunoglobulin, rituximab, and mycophenolate, all reduced annualised relapse rates. 59% of patients experienced residual disability, particularly with increasing relapses. Conclusions: MOG antibodies are strongly associated with ON. Relapsing disease is steroid responsive but vulnerable to relapse, responds to immunosuppression, and has the potential to result in sustained disability

Visual Outcomes of Adding Erythropoietin to Methylprednisolone for Treatment of Retrobulbar Optic Neuritis

Purpose: To compare the short-term visual function results and safety of erythropoietin as an add-on to the standard corticosteroid therapy in retrobulbar optic neuritis (RON). Methods: In this prospective pilot study, adult patients with isolated RON with less than 10 days of onset were enrolled. Patients were consecutively assigned to standard intravenous methylprednisolone treatment either in combination with intravenous erythropoietin (20,000 units/day for three days) (group-1) or alone (group-2). Primary outcome measure was best-corrected visual acuity (BCVA), which was assessed up to 120 days from the day the treatment was begun. Systemic evaluations were performed during and after treatment. Results: Sixty-two patients with RON (mean age = 26.6 ± 5.77 years; range = 18–40 years) were enrolled into the study (group-1, n = 35; group-2, n = 27). BCVA three months after the treatment was 0.19 ± 0.55 logMAR and 0.11 ± 0.32 logMAR in group-1 and group-2, respectively (95% CI: –0.61–0.16; P = 0.62). Change in BCVA after three months was 2.84 ± 3.49 logMAR in group-1 and 2.46 ± 1.40 logMAR in group-2 (95% CI: –0.93–1.91; P = 0.57). Pace of recovery was not significantly different between the groups. No complications were detected among patients. Conclusion: Intravenous erythropoietin as an add-on did not significantly improve the visual outcome in terms of visual acuity, visual field, and contrast sensitivity compared to traditional intravenous corticosteroid. This pilot study supports the safety profile of intravenous human recombinant erythropoietin, and it may help formulate future investigations with a larger sample size

Detecting retinal cell stress and apoptosis with DARC: Progression from lab to clinic

DARC (Detection of Apoptosing Retinal Cells) is a retinal imaging technology that has been developed within the last 2 decades from basic laboratory science to Phase 2 clinical trials. It uses ANX776 (fluorescently labelled Annexin A5) to identify stressed and apoptotic cells in the living eye. During its development, DARC has undergone biochemistry optimisation, scale-up and GMP manufacture and extensive preclinical evaluation. Initially tested in preclinical glaucoma and optic neuropathy models, it has also been investigated in Alzheimer, Parkinson's and Diabetic models, and used to assess efficacy of therapies. Progression to clinical trials has not been speedy. Intravenous ANX776 has to date been found to be safe and well-tolerated in 129 patients, including 16 from Phase 1 and 113 from Phase 2. Results on glaucoma and AMD patients have been recently published, and suggest DARC with an AI-aided algorithm can be used to predict disease activity. New analyses of DARC in GA prediction are reported here. Although further studies are needed to validate these findings, it appears there is potential of the technology to be used as a biomarker. Much larger clinical studies will be needed before it can be considered as a diagnostic, although the relatively non-invasive nature of the nasal as opposed to intravenous administration would widen its acceptability in the future as a screening tool. This review describes DARC development and its progression into Phase 2 clinical trials from lab-based research. It discusses hypotheses, potential challenges, and regulatory hurdles in translating technology