Defining molecular pathways of regulatory T cell-mediated oligodendrocyte differentiation and remyelination

The purpose of this project is to study how a natural regenerative process in the Central Nervous System (CNS) is influenced by the immune system and uncover changes that happen inside cells to accomplish this. Myelin is a fatty substance that wraps around long projections (axons) of nerves to allow rapid conduction of nerve signals and also plays a protective role for axons. Recent exciting discoveries have also shown that myelin 'feeds' nerves with metabolites that nerves use to make energy and this explains why disruption to myelin in disease or with age, can have such profound consequences for neurological functions such as memory, movement and sensation. Myelination, the process of sheathing axons with myelin, is a very active process early in life but continues well into later life. Cells called oligodendrocytes make this myelin in the CNS. Remyelination is a natural regenerative process that replaces damaged myelin but ageing impairs the efficiency of remyelination in the CNS which can lead to neurological impairment with age.
Traditionally it was thought that immune cells usually only entered the CNS during disease. However, in recent years we have learned a great deal about how the immune system supports a wide range of basic CNS functions. In particular, immune cells called T cells have been shown to support neurological functions such as learning, memory and CNS repair. Other immune cells have also been shown to support remyelination, however, little is known about the role of T cells in this process. There has been one study that showed that deficiency of T cells impairs remyelination. However, T cells comprise a wide range of different subsets, each of which exert different, and often opposing, effects. We have recently made exciting discoveries that one of these subsets called regulatory T cells (Treg) specifically boosts remyelination and this is accomplished in part by secreting factors that act on cells in the CNS called oligodendrocyte progenitor cells (OPC). These cells are similar to late stage stem cells - these cells are committed to becoming oligodendrocytes but are not yet capable of doing so. Our findings show that regulatory T cells can provide the signals to help these cells mature and wrap myelin around nerves.
However, we do not understand what changes Tregs trigger in OPCs to cause maturation. The goal of this study is to investigate what genes are switched on/off in OPCs and what messages are relayed inside OPC when Tregs communicate with OPCs. We will determine this by molecular profiling of OPCs that have been treated with Tregs compared to control OPCs. Once we have a shortlist of changes that Treg cause in OPC we will test the candidates in experimental models of remyelination to determine exactly which changes are responsible for the remyelination-enhancing effect of Tregs. These validation experiments will first be done in a new 3-D model of CNS remyelination consisting of thin slices of brain tissue in a dish that we have developed. Candidates validated in this model will then be tested in living mice undergoing remyelination. Using the model of brain tissue in a dish means we minimise the number of experiments on live animals
The outcomes of this study will include new knowledge of how the immune system, and Tregs in particular, influence remyelination in the CNS. We will learn about how Tregs and OPC interact and communicate with one another, an area of biology that is completely unknown. Another outcome of this study will be further development of our new model of immune cell- neural cell communication which can be adopted by a multitude of scientists study a range of topics in neuroscience and immunology. Knowledge from this project may be taken forward to identify strategies to preserve remyelination, and thus neurological function, during ageing and as such, this project holds potential to impact a very large proportion of society.

In the Central Nervous System myelin insulates axons and provides metabolic support and protection. Myelin is produced by oligodendrocytes and is regenerated (remyelination) by these cells throughout life. Mature oligodendrocytes cells arise from a pool of oligodendrocyte progenitor cells that require cues to differentiate and produce myelin. Recently, an emerging role of immune signaling in promoting remyelination has gained significant attention. We have discovered that regulatory T cells promote remyelination by enhancing OPC differentiation to oligodendrocytes revealing a completely new role for Treg in the CNS and a novel source of differentiation cues for OPC. However, we have no knowledge of the intracellular signaling in OPC that is triggered by Treg to induce differentiation. This proposal seeks to address this gap in knowledge which will be accomplished through 4 specific aims: 1) transcriptomic profiling of Treg-primed OPC by microarray 2) molecular signaling analysis of Treg-primed OPC by phosphoflow and proteome profiler analysis 3) investigation of identified candidate molecular mediators during Treg-enhanced remyelination of organotypic brain slice cultures and 4) validation of the importance of novel molecular mediators of Treg-induced remyelination in vivo. These studies will uncover the molecular mechanisms underlying Treg-induced remyelination and provide new knowledge of neuroimmunological crosstalk in the CNS in health and disease.

This research will impact a wide range of beneficiaries in academia, industry and the greater public.
My group frequently hosts visiting scientists from around the world and maintaining our research at the cutting-edge through this programme will ensure we can continue to attract such world experts to the UK and QUB. We also host visits by the public, patient support groups and school/university students to provide an insight to the workings of a research laboratory. This impacts the public's perception of research and serves to bolster support for public spending on research.
Age-related physiological decline is increasing in our ageing society, thus, it is imperative that we identify underlying causes of such decline if we are to minimise this deterioration and promote healthy ageing. This study is focused on the central nervous system and so, this work holds potential to impact people that will develop age-associated neurological impairment which can range from relatively minor impairments to severely debilitating motor, autonomic and cognitive impairments. As CNS remyelination declines with age we need identify strategies that can minimise such decline to main neurological function and preservation of a healthy functioning immune system may be one such strategy. Findings from this work may also inform future translational studies in neurological conditions of younger individuals also including patients with MS, ALS, depression and schizophrenia given recent discoveries of myelin dysfunction in these conditions.
While this is a project investigating a fundamental biological relationship between the immune and neural cells, new knowledge we generate may inform optimal immune status to promote and maintain efficient remyelination. If this is the case, our discoveries will contribute to informing policy, lifestyle and life-long treatment of individuals to maximise CNS-relevant immune function with advancing age. As such, this work may impact a large sector of the ageing population.
This work will also impact research scientists primarily in the fields of neuroscience, immunology and regenerative biology. The technology we have developed can be exploited by these and other fields. Our novel image analysis software already has, and will continue to be shared with the scientific community through publication and may be exploited by others for quantification of colocalisation of ambiguous structures in 3D. Our work will also impact researchers around the world through our 'Free to share software' page on our website where we make our novel image analysis plugins freely available.
The work also holds potential to impact industry through development of academic-industry partnership with IP generated. The University will also benefit in publicising the discovery research it will host in this work and through commercial exploitation. Indeed commercial exploitation of discoveries in this project holds potential to generate income and employment in the UK. In the immediate term, this project will direct employ 2 part time scientists and one full-time PDRA who will benefit greatly in terms of career development as well as support the experimental work of a PhD student that will be funded by the University. This project will also strengthen my group's collaboration with key opinion leaders in neuroscience nationally and internationally and grow our relationship with commercial entities. Enhancing the research training environment of my team will supply new graduates and postdoctoral fellows to expand the knowledge and skills of businesses, academia and organisations in Northern Ireland and further afield.
Finally, this research programme will provide stability, longevity and productivity to my consolidating laboratory and will reinforce the cutting-edge, collaborative neuroimmunology and regenerative research programmes we are developing in Northern Ireland.