Macrophagic and microglial responses after focal traumatic brain injury in the female rat

Background: after central nervous system injury,inflammatory macrophages (m1) predominate over anti-inflammatory macrophages (m2). the temporal profile of m1/m2 phenotypes in macrophages and microglia after traumatic brain injury (tbi) in rats is unknown. we subjected female rats to severe controlled cortical impact (cci) and examined the postinjury m1/m2 time course in their brains.methods: the motor cortex (2.5 mm left laterally and 1.0 mm anteriorly from the bregma) of anesthetized female wistar rats (ages 8 to 10 weeks; n = 72) underwent histologically moderate to severe cci with a 5-mm impactor tip. separate cohorts of rats had their brains dissociated into cells for flow cytometry,perfusion-fixed for immunohistochemistry (ihc) and ex vivo magnetic resonance imaging or flash-frozen for rna and protein analysis. for each analytical method used,separate postinjury times were included for 24 hours; 3 or 5 days; or 1,2,4 or 8 weeks.results: by ihc,we found that the macrophagic and microglial responses peaked at 5 to 7 days post-tbi with characteristics of mixed populations of m1 and m2 phenotypes. upon flow cytometry examination of immunological cells isolated from brain tissue,we observed that peak m2-associated staining occurred at 5 days post-tbi. chemokine analysis by multiplex assay showed statistically significant increases in macrophage inflammatory protein 1α and keratinocyte chemoattractant/growth-related oncogene on the ipsilateral side within the first 24 hours after injury relative to controls and to the contralateral side. quantitative rt-pcr analysis demonstrated expression of both m1- and m2-associated markers,which peaked at 5 days post-tbi.conclusions: the responses of macrophagic and microglial cells to histologically severe cci in the female rat are maximal between days 3 and 7 postinjury. the response to injury is a mixture of m1 and m2 phenotypes. © 2014 turtzo et al.; licensee biomed central ltd.