2Rs (Refining & reducing) of Animal Models of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the brain and spinal cord that results in nerve-damage and the accumulation of disability. Whilst some progress has been made in the treatment of relapsing disease, there are no treatments that control accumulation of progressive-disability. We aim to find useful treatments for this aspect of disease. The main animal-model of MS, used to assess the action of drugs prior to trials in humans, is an induced paralytic-disease called experimental autoimmune encephalomyelitis (EAE). Although we are not yet in a position to completely ?replace? animal use for identifying drugs to treat disease we can make these models better such that they can still detect drugs that stop the destructive actions of the white blood cells that drive nerve damage whilst limiting the suffering to the animals. This can be done by controlling the severity of disease and the length of time in procedure required to detect drug-effects. The optic nerve that links the eye to the brain is often damaged in MS and the visual pathway has been selected as an important system for testing new drugs for MS. Mice, do not use sight as a major sense and tolerate loss of vision.

We plan to develop a mouse system that models this optic nerve damage, using genetically-engineered mice, whose white blood cells are programmed to attack only the optic nerve, whilst leaving the rest of the nervous system unaffected. Therefore, paralysis no longer develops and thus limits the suffering of animals. Furthermore, cells in the retina at the back of the eye will be made to glow, due to further genetic-engineering, following observation with a special-type of microscope through the eye. As optic nerves are damaged their glowing, cell-bodies are lost, thus the survival and death of nerves can be easily monitored in the living animal. This generates a significant improvement over existing models, where detection of nerve content is time consuming and requires test-animals to be culled at each observation point. As this new model can be serially-monitored, fewer animals will need to be used in experiments. Furthermore we can monitor nerve impulse transmission of the optic nerve, so that we can serially detect damage and repair for the first time. This provides a number of advantages over existing models and thus may encourage others to replace the existing severe model with the milder system to be developed in this project.

Multiple sclerosis (MS) is an autoimmune-mediated, neurodegenerative disease of the central nervous system (CNS), where about 80% of people will be severely disabled within 25 years of diagnosis. Whilst some progress has been made in the treatment of relapsing disease, there are no treatments that control progressive neurodegeneration in MS. The chief animal model of MS is experimental autoimmune encephalomyelitis (EAE) in rodents and primates, which if used appropriately can recapitulate many of the features of MS. These features are not adequately modelled in vitro, such that animal models can be ?replaced? but models can be ?refined? that will facilitate a ?reduction? in animal use. Whilst EAE, is typically used to detect immune-influences there is an increasing need to detect neuroprotective effects. Disease in rodent EAE models results in periods of, subjectively-assessed, paralysis and the accumulation of neurological disability that often requires time-consuming, histology to assess. We aim to generate a model of MS, with reduced severity that can be used to assess neuroprotection and repair in wildtype and knockout C57BL/6 (EAE-low responder strain) animals.

The visual system is commonly affected in MS and optic neuritis is typical early feature of MS. This results in visual impairment that is reflected by optic nerve damage and retinal ganglion cell (RGC) loss. This occurs in MS even in the absence of optic neuritis. The visual system is the most accessible neural pathway of the human CNS, and this has been proposed to be an important target lesion for repair and neuroprotection studies in MS. However, the optic nerve is not always affected during EAE. We will produce mice that express transgenes coding for myelin specific-T cell receptors and cyan fluorescent protein expressed in the RGC. These mice spontaneously, or can be induced without the need for Freund?s adjuvant, to develop CNS autoimmunity in the optic nerve, in the absence of paralytic EAE, thus reducing the number of animals in substantial protocols. Damage in the optic nerve will be reflected by demyelination and loss of RGC that can be serially and rapidly quantitated using confocal scanning laser ophthalmoscopy and optical coherence tomography in the living animal. This when coupled with electrophysiology to detect demyelination and repair, can replicate proposed clinical studies and this will provide a valuable tool to detect, immunomodulatory, neuroprotective and repair agents that will reduce the number of substantial procedures and reduce the animals required to detect therapeutic effects.