title: Call Off the Dog(ma): M1/M2 Polarization Is Concurrent following Traumatic Brain Injury.
abstract: Following the primary mechanical impact, traumatic brain injury (TBI) induces the simultaneous production of a variety of pro- and anti-inflammatory molecular mediators. Given the variety of cell types and their requisite expression of cognate receptors this creates a highly complex inflammatory milieu. Increasingly in neurotrauma research there has been an effort to define injury-induced inflammatory responses within the context of in vitro defined macrophage polarization phenotypes, known as "M1" and "M2". Herein, we expand upon our previous work in a rodent model of TBI to show that the categorization of inflammatory response cannot be so easily delineated using this nomenclature. Specifically, we show that TBI elicited a wide spectrum of concurrent expression responses within both pro- and anti-inflammatory arms. Moreover, we show that the cells principally responsible for the production of these inflammatory mediators, microglia/macrophages, simultaneously express both "M1" and "M2" phenotypic markers. Overall, these data align with recent reports suggesting that microglia/macrophages cannot adequately switch to a polarized "M1-only" or "M2-only" phenotype, but display a mixed phenotype due to the complex signaling events surrounding them.
authors.affiliation: Brain and Spinal Injury Center, University of California San Francisco, San Francisco, CA, United States of America.|Departments of Physical Therapy and Rehabilitation Science, University of California San Francisco, San Francisco, CA, United States of America.
authors.forename: Josh M
authors.initials: JM
authors.lastname: Morganti
authors.affiliation: Brain and Spinal Injury Center, University of California San Francisco, San Francisco, CA, United States of America.|Departments of Physical Therapy and Rehabilitation Science, University of California San Francisco, San Francisco, CA, United States of America.
authors.forename: Lara-Kirstie
authors.initials: LK
authors.lastname: Riparip
authors.affiliation: Brain and Spinal Injury Center, University of California San Francisco, San Francisco, CA, United States of America.|Departments of Physical Therapy and Rehabilitation Science, University of California San Francisco, San Francisco, CA, United States of America.|Neurological Surgery, University of California San Francisco, San Francisco, CA, United States of America.
authors.forename: Susanna
authors.initials: S
authors.lastname: Rosi
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000276:immunology* / Q000503:physiopathology*; D007249:Inflammation / Q000209:etiology / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D051379:Mice; D015398:Signal Transduction