|dc.description.abstract||Microglia are the resident macrophages of the central nervous system (CNS) and, as
key immune effector cells, form the first line of defence. Microglial cells also provide
support for maintaining neuronal homeostasis and more generally normal brain
physiology and cognitive function. It has been speculated that in order to support
homeostasis, microglia adapt to a variety of brain microenvironments leading to
regional phenotypic heterogeneity. To date this hypothesis lacks convincing
empirical evidence, yet is critical to better understand microglial function in health
and age-related neurodegenerative disease. In 2010 it was estimated that in the UK
approximately 10 million people are over the age of 65, which is expected to double
by 2050. Ageing is one of the strongest risk factors for neurodegenerative diseases
such as Alzheimer’s and Parkinson‘s disease and growing evidence implicates
neuroinflammatory mechansims that may involve microglial dysfunction in disease
aetiology. The majority of age-related neurodegenerative diseases develop in a
region-specific manner but the reasons are poorly understood. Accordingly, the
work described in this thesis sought to determine the extent and nature of regional
transcriptional heterogeneity of microglia and how this is affected by ageing.
To examine the function and phenotype of these cells a technique for isolating pure
microglia from the adult mouse brain was established. Microglia were consistently
extracted by density-gradient and immunomagnetic cell separation. In vitro assays
showed purified microglia retained key functional properties including
phagocytosis, polarisation and production of pro-inflammatory cytokines in
response to exogenous stimulation. Thus, freshly isolated microglia are not altered
or dysfunctional during the extraction process and are likely to adequately
represent the 'real' in vivo state.
Genome-wide transcriptional network analysis of young adult mouse microglia
from four discrete regions of the brain (cerebellum, cerebral cortex, hippocampus
and striatum) uncovered regional heterogeneity in the microglial transcriptome
driven particularly by bioenergetic and immunoregulatory functions.
Transcriptional profiles of cerebellar and hippocampal microglia suggest a higher
immune vigilance and alertness, which was supported by functional differences in
the capability of microglia to phagocytose and control replication of bacteria.
Region-dependent heterogeneity of microglia was largely consistent throughout the
ageing process; however the region-specific phenotypes were more pronounced as
age increased indicating region-dependent kinetics of microglial ageing.
Collectively, the outcome of this study implies that microglia adapt to region-specific
demands of brain tissue under steady-state conditions and are susceptible to
ageing. Region was found to have a greater impact on microglial diversity than age.
Overall, these findings will generate a substantial advance in our understanding of
microglial function in the healthy brain and in age-related neurodegeneration.||en
|dc.relation.hasversion||Sauter, K. A., Pridans, C., Sehgal, A., Bain, C. C., Scott, C. C., Moffat, L., Rojo, R., Stutchfield, B. M., Davies, C. L., Donaldson, D. S., Renault, K., McColl, B. W., Mowat, A. M., Serrels, A., Frame, M. C., Mabbott, N. A., Hume, D. A. (2014): The MacBlue Binary Transgene (csf1r-gal4VP16/UAS-ECFP) Provides a Novel Marker for Visualization of Subsets of Monocytes, Macrophages and Dendritic Cells and Responsiveness to CSF1 Administration. PLoS One, Vol.9, No. 8, DOI: 10.1371/journal.pone.0105429||en