title: Temporal Characterization of Microglia/Macrophage Phenotypes in a Mouse Model of Neonatal Hypoxic-Ischemic Brain Injury.
abstract: Immune cells display a high degree of phenotypic plasticity, which may facilitate their participation in both the progression and resolution of injury-induced inflammation. The purpose of this study was to investigate the temporal expression of genes associated with classical and alternative polarization phenotypes described for macrophages and to identify related cell populations in the brain following neonatal hypoxia-ischemia (HI). HI was induced in 9-day old mice and brain tissue was collected up to 7 days post-insult to investigate expression of genes associated with macrophage activation. Using cell-markers, CD86 (classic activation) and CD206 (alternative activation), we assessed temporal changes of CD11b+cell populations in the brain and studied the protein expression of the immunomodulatory factor galectin-3 in these cells. HI induced a rapid regulation (6 h) of genes associated with both classical and alternative polarization phenotypes in the injured hemisphere. FACS analysis showed a marked increase in the number of CD11b+CD86+cells at 24 h after HI (+3667%), which was coupled with a relative suppression of CD11b+CD206+cells and cells that did not express neither CD86 nor CD206. The CD11b+CD206+population was mixed with some cells also expressing CD86. Confocal microscopy confirmed that a subset of cells expressed both CD86 and CD206, particularly in injured gray and white matter. Protein concentration of galectin-3 was markedly increased mainly in the cell population lacking CD86 or CD206 in the injured hemisphere. These cells were predominantly resident microglia as very few galectin-3 positive cells co-localized with infiltrating myeloid cells inLys-EGFP-kimice after HI. In summary, HI was characterized by an early mixed gene response, but with a large expansion of mainly the CD86 positive population during the first day. However, the injured hemisphere also contained a subset of cells expressing both CD86 and CD206 and a large population that expressed neither activation marker CD86 nor CD206. Interestingly, these cells expressed the highest levels of galectin-3 and were found to be predominantly resident microglia. Galectin-3 is a protein involved in chemotaxis and macrophage polarization suggesting a novel role in cell infiltration and immunomodulation for this cell population after neonatal injury.
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Nina
authors.initials: N
authors.lastname: Hellström Erkenstam
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Peter L P
authors.initials: PL
authors.lastname: Smith
authors.affiliation: Centre for the Developing Brain, Perinatal Imaging and Health, King's College London, St. Thomas' HospitalLondon, UK; PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris CitéParis, France.
authors.forename: Bobbi
authors.initials: B
authors.lastname: Fleiss
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Syam
authors.initials: S
authors.lastname: Nair
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Pernilla
authors.initials: P
authors.lastname: Svedin
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska AcademyGothenburg, Sweden; Department of Pediatrics, Institute of Clinical Sciences, University of Gothenburg, Sahlgrenska AcademyGothenburg, Sweden.
authors.forename: Martina
authors.initials: M
authors.lastname: Boström
authors.affiliation: Centre for the Developing Brain, Perinatal Imaging and Health, King's College London, St. Thomas' HospitalLondon, UK; PROTECT, INSERM, Université Paris Diderot, Sorbonne Paris CitéParis, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Gressens
authors.affiliation: Centre for the Developing Brain, Perinatal Imaging and Health, King's College London, St. Thomas' HospitalLondon, UK; Department of Obstetrics and Gynecology, Perinatal Center, Institute of Clinical Sciences, University of Gothenburg, Sahlgrenska AcademyGothenburg, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Hagberg
authors.affiliation: Department of Pediatrics, University of British Columbia and the Child and Family Research Institute Vancouver, BC, Canada.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Brown
authors.affiliation: Department of Obstetrics and Gynecology, Perinatal Center, Institute of Clinical Sciences, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Sävman
authors.affiliation: Institute of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska Academy Gothenburg, Sweden.
authors.forename: Carina
authors.initials: C
authors.lastname: Mallard
keywords: galectin-3; microglia; neuroinflammation; perinatal brain injury