The continuum of microglial subpopulations to functional changes in multiple sclerosis

• Applicant: Privatdozentin Dr. Chotima Böttcher
• Subject Area: Molecular and Cellular Neurology and Neuropathology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 500300545

Rationale. Microglia are the resident phagocytes in the brain parenchyma, as such they are the first responders during disruption of central nervous system homeostasis as in neuroinflammation including multiple sclerosis (MS). Upon disruption of brain homeostasis, microglia typically undergo a set of changes in their protein expression, morphology, metabolism and proliferation. In progressive MS (PMS), using mass cytometry (CyTOF) and imaging CyTOF (IMC), we have characterized and compared white matter (WM) myeloid cells including microglia isolated from active lesion and normal-appearing (NA) WM. Our results showed phenotypic heterogeneity of macrophage/microglia in active lesions, ranging from protective to activated events including increase in phagocytic phenotype and expression of pro-inflammatory molecules which can lead to sustained neuroinflammation and eventually further contribute to neurodegeneration. However, it remains to be investigated whether this phenotypic heterogeneity correlates with diversity of local drivers or microglial functions towards pathological site (i.e. in the different lesion types of MS; cortical and slow expanding active lesions, as well as in the remyelinated area (a shadow plaque)). Aim and work plan. In this project, we aim to map the continuum of microglial phenotypes to functional/metabolomic changes in different lesion types of MS (i.e. cortical and slow expanding active lesions), compared to NAWM, NA grey matter (NAGM) and shadow plaques (n=10, 5 regions/donor). Brain tissues from donors without neuropathology and those with non-MS neuroinflammation will be used as controls (n = 10, grey and white matter). We will employ two state-of-the-art spatial technologies, which are imaging mass cytometry (IMC) and DESI-ion mobility-TOF mass spectrometry for in situ analysis of metabolites and lipids. The relationships between phenotypic, metabolomic and functional changes of microglia/macrophage in different lesion types compared to NAWM and NAGM as well as controls will be deciphered using state-of-the-art algorithms. Cell-cell interaction between different microglial/macrophage subsets and other CNS cells in different MS lesion types as well as NAWM, NAGM and shadow plaques will also be evaluated. Finally, the findings will be validated/compared with the relapsing-remitting EAE mouse model.Expected results. Our findings will provide new insights into the roles of microglia/macrophage and their responses to local cues in different lesion types towards MS neuropathological sites, which will lead to better understanding biology of human microglia and their roles in different MS stages, as well as how to manipulate them in different MS conditions. Furthermore, the results that will be obtained from the area with remyelination will additionally provide evidence for the role of microglia in regeneration process of MS, which will have an important impact on a future development of the treatment targeting microglia.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2395: Local and peripheral drivers of microglial diversity and function
• International Connection: United Kingdom
• Cooperation Partner: Professor Dr. Zoltan Takats, Ph.D.