title: Early monitoring and quantitative evaluation of macrophage infiltration after experimental traumatic brain injury: A magnetic resonance imaging and flow cytometric analysis.
abstract: The inflammatory response following traumatic brain injury (TBI) is regulated by phagocytic cells. These cells comprising resident microglia and infiltrating macrophages play a pivotal role in the interface between early detrimental and delayed beneficial effects of inflammation. The aim of the present study was to monitor the early effect of monocyte/phagocytic accumulation and further to explore its kinetics in TBI mice. Localized macrophage population was monitored using ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle enhanced in vivo serial magnetic resonance imaging (MRI). Flow cytometry based gating study was performed to discriminate between resident microglia (Ly6G-CD11b+CD45low) and infiltrating macrophages (Ly6G-CD11b+CD45high) at the injury site. The T2* relaxation analysis revealed that maximum macrophage infiltration occurs between 66 and 72h post injury (42-48h post administration of USPIO) at the site of inflammation. This imaging data was well supported by iron oxide specific Prussian blue staining and macrophage specific F4/80 immunohistochemistry (IHC) analysis. Quantitative real-time PCR analysis found significant expression of monocyte chemoattractant protein-1 (MCP-1) at 72h post injury. Also, we found that flow cytometric analysis demonstrated a 7-fold increase in infiltrating macrophages around 72h post injuries as compared to control. The MR imaging in combination with flow cytometric analysis enabled the dynamic measurement of macrophage infiltration at the injury site. This study may help in setting an optimal time window to intervene and prevent damage due to inflammation and to increase the therapeutic efficacy.
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India; Division of Stem Cell and Gene Therapy Research, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India.
authors.forename: Sushanta Kumar
authors.initials: SK
authors.lastname: Mishra
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India.
authors.forename: B S Hemanth
authors.initials: BS
authors.lastname: Kumar
authors.affiliation: NMR Research Centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India. Electronic address: skhushu@yahoo.com.
authors.forename: Subash
authors.initials: S
authors.lastname: Khushu
authors.affiliation: Division of Radiation Biosciences, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India.
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Singh
authors.affiliation: Division of Stem Cell and Gene Therapy Research, Institute of Nuclear Medicine and Allied Sciences (INMAS), DRDO, Delhi-54, India. Electronic address: gugdutta@rediffmail.com.
authors.forename: Gurudutta
authors.initials: G
authors.lastname: Gangenahalli
mesh_terms: D000818:Animals; D000070642:Brain Injuries, Traumatic / Q000000981:diagnostic imaging / Q000276:immunology / Q000473:pathology*; D002465:Cell Movement; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C
keywords: Flow cytometry; Macrophages; Magnetic resonance imaging; Microglia; Neuroinflammation; Traumatic brain injury; USPIO