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Authors & Affiliations
Polina Bugaeva, Paul Fischer, Amelie Weber, Daniel Berchtold, Stefan Jordan, Leif Koschützke, Christian Hoffmann, Matthias Endres, Anna Malik, Steffen Jung, Daniel Lewandowski, Christoph Harms
Abstract
Clonal hematopoiesis, which refers to somatic mutations in hematopoietic stem cells (HSC), is recognized as a risk factor for stroke. Tet2 mutations exerted the greatest influence on complex cardiovascular endpoints in a study of incident strokes. The aim of this preclinical study was to explore if mutant HSC exhibit an aggressive phenotype, releasing pro-inflammatory cytokines and causing more damage to the penumbra area, heart, endothelial cells, and the blood-brain barrier (BBB). One-leg irradiated mice grafted into with WT or Tet2-/- (induced knockout) chimeric bone marrow were subjected to 30-minute middle cerebral artery occlusion (MCAO) after 18 months. We assessed lesion sizes 1 and 7 days after MCAO using T2-MRI. Functional recovery was investigated by means of a behavioral test panel. Peripheral blood, bone marrow, and brain underwent flow cytometry-based immunophenotyping to assess expansion and invasion of Tet2-deficient cells. There was no difference in stroke lesion sizes between mice harboring WT and Tet2-deficient immune cells. Mice with mutant bone marrow also displayed similar functional deficit or recovery. We have not identified clonal expansion of Tet2-deficient cells in peripheral blood. Flow cytometry of the brain tissue revealed higher invasion of host immune cells and higher number of host microglia in lesion area of Tet2-deficient mice. We observed some evidence of a pro-inflammatory state in mice harboring Tet2-deficient cells after stroke that corresponded with clinical findings. However, the next round of study will require model refinement including a raise of the frequency of Tet2-deficient cells and the analysis of younger animals.