title: Triggering Receptor Expressed on Myeloid Cells 2 Deficiency Alters Acute Macrophage Distribution and Improves Recovery after Traumatic Brain Injury.
abstract: Traumatic brain injury (TBI) affects 1.7 million persons annually in the United States (Centers for Disease Control and Prevention). There is increasing evidence that persons exposed to TBI have increased risk of the development of multiple neurodegenerative conditions, including Alzheimer disease (AD). TBI triggers a strong neuroinflammatory response characterized by astrogliosis, activation of microglia, and infiltration of peripheral monocytes. Recent evidence suggests that alterations in innate immunity promote neurodegeneration. This includes genetic studies demonstrating that mutations in triggering receptor expressed on myeloid cells 2 (TREM2) is associated with a higher risk for not only AD but also multiple neurodegenerative diseases. To examine whether TREM2 deficiency affects pathological outcomes of TBI, Trem2 knockout (Trem2-/-) and C57BL/6J (B6) mice were given a lateral fluid percussion injury (FPI) and sacrificed at 3 and 120 days post-injury (DPI) to look at both acute and chronic consequences of TREM2 deficiency. Notably, at 3 DPI, B6 mice exposed to TBI exhibited increased expression of TREM2 in the brain. Further, Trem2-/-mice exposed to TBI exhibited enhanced macrophage activation near the lesion, but significantly less macrophage activation away from the lesion when compared with B6 mice exposed to TBI. In addition, at 120 DPI, Trem2-/-mice exposed to TBI demonstrated reduced hippocampal atrophy and rescue of TBI-induced behavioral changes when compared with B6 mice exposed to TBI. Taken together, this study suggests that TREM2 deficiency influences both acute and chronic responses to TBI, leading to an altered macrophage response at early time points, and improved pathological and functional outcomes at later time points.
authors.affiliation: 1 Department of Neurosciences, Cleveland Clinic , Cleveland, Ohio.|2 Department of Molecular Medicine, Case Western Reserve University , Cleveland, Ohio.
authors.forename: Maha
authors.initials: M
authors.lastname: Saber
authors.affiliation: 4 Stark Neurosciences Research Institute , Indianapolis, Indiana.
authors.forename: Olga
authors.initials: O
authors.lastname: Kokiko-Cochran
authors.affiliation: 4 Stark Neurosciences Research Institute , Indianapolis, Indiana.
authors.forename: Shweta S
authors.initials: SS
authors.lastname: Puntambekar
authors.affiliation: 3 Department of Cellular Molecular Medicine, Cleveland Clinic , Cleveland, Ohio.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Lathia
authors.affiliation: 1 Department of Neurosciences, Cleveland Clinic , Cleveland, Ohio.|4 Stark Neurosciences Research Institute , Indianapolis, Indiana.
authors.forename: Bruce T
authors.initials: BT
authors.lastname: Lamb
mesh_terms: D000818:Animals; D000070642:Brain Injuries, Traumatic / Q000378:metabolism* / Q000473:pathology; D005260:Female; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D008297:Male; D018782:Maze Learning / Q000502:physiology; D008562:Membrane Glycoproteins / Q000172:deficiency*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D022423:Myeloid Cells / Q000378:metabolism / Q000473:pathology; D011971:Receptors, Immunologic / Q000172:deficiency*; D020127:Recovery of Function / Q000502:physiology*
chemical_list: D008562:Membrane Glycoproteins; D011971:Receptors, Immunologic; C498716:Trem2 protein, mouse
keywords: behavior; immunohistochemistry; inflammation; neurodegenerative disorders; traumatic brain injury