title: Macrophages are comprised of resident brain microglia not infiltrating peripheral monocytes acutely after neonatal stroke.
abstract: Macrophages can be both beneficial and detrimental after CNS injury. We previously showed rapid accumulation of macrophages in injured immature brain acutely after ischemia-reperfusion. To determine whether these macrophages are microglia or invading monocytes, we subjected post-natal day 7 (P7) rats to transient 3 h middle cerebral artery (MCA) occlusion and used flow cytometry at 24 and 48 h post-reperfusion to distinguish invading monocytes (CD45high/CD11b+) from microglia (CD45low/medium/CD11b+). Inflammatory cytokines and chemokines were determined in plasma, injured and contralateral tissue 1-24 h post-reperfusion using ELISA-based cytokine multiplex assays. At 24 h, the number of CD45+/CD11b+ cells increased 3-fold in injured compared to uninjured brain tissue and CD45 expression shifted from low to medium with less than 10% of the population expressing CD45high. MCA occlusion induced rapid and transient asynchronous increases in the pro-inflammatory cytokine IL-beta and chemokines cytokine-induced neutrophil chemoattractant protein 1 (CINC-1) and monocyte-chemoattractant protein 1 (MCP-1), first in systemic circulation and then in injured brain. Double immunofluorescence with cell-type specific markers showed that multiple cell types in the injured brain produce MCP-1. Our findings show that despite profound increases in MCP-1 in injured regions, monocyte infiltration is low and the majority of macrophages in acutely injured regions are microglia.
authors.affiliation: Department of Neurology, University of California San Francisco, San Francisco, CA 94143-0663, USA.
authors.forename: Sheryl P
authors.initials: SP
authors.lastname: Denker
authors.forename: Shaoquan
authors.initials: S
authors.lastname: Ji
authors.forename: Andra
authors.initials: A
authors.lastname: Dingman
authors.forename: Sarah Y
authors.initials: SY
authors.lastname: Lee
authors.forename: Nikita
authors.initials: N
authors.lastname: Derugin
authors.forename: Michael F
authors.initials: MF
authors.lastname: Wendland
authors.forename: Zinaida S
authors.initials: ZS
authors.lastname: Vexler
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D039481:CD11b Antigen / Q000378:metabolism; D018925:Chemokines / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D007150:Immunohistochemistry; D037102:Lectins / Q000378:metabolism; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008262:Macrophage Activation / Q000502:physiology; D008264:Macrophages / Q000502:physiology*; D017628:Microglia / Q000378:metabolism / Q000502:physiology*; D009000:Monocytes / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury; D020521:Stroke / Q000473:pathology* / Q000503:physiopathology*; D013997:Time Factors
chemical_list: D039481:CD11b Antigen; D018925:Chemokines; D016207:Cytokines; D005904:Glial Fibrillary Acidic Protein; D037102:Lectins; D017493:Leukocyte Common Antigens