title: Characterization of microparticles after hepatic ischemia-reperfusion injury.
abstract: BACKGROUND
  Hepatic ischemia-reperfusion (I/R) is a well-studied model of liver injury and has demonstrated a biphasic injury followed by recovery and regeneration. Microparticles (MPs) are a developing field of study and these small membrane bound vesicles have been shown to have effector function in other physiologic and pathologic states. This study was designed to quantify the levels of MPs from various cell origins-platelets, neutrophils, and endolethial cells-following hepatic ischemia-reperfusion injury.
  
  
  METHODS
  A murine model was used with mice undergoing 90 minutes of partial hepatic ischemia followed by various times of reperfusion. Following reperfusion, plasma samples were taken and MPs of various cell origins were labeled and levels were measured using flow cytometry. Additionally, cell specific MPs were further assessed by Annexin V, which stains for the presence of phosphatidylserine, a cell surface marker linked to apoptosis. Statistical analysis was performed using one-way analysis of variance with subsequent Student-Newman-Keuls test with data presented as the mean and standard error of the mean.
  
  
  RESULTS
  MPs from varying sources show an increase in circulating levels following hepatic I/R injury. However, the timing of the appearance of different MP subtypes differs for each cell type. Platelet and neutrophil-derived MP levels demonstrated an acute elevation following injury whereas endothelial-derived MP levels demonstrated a delayed elevation.
  
  
  CONCLUSIONS
  This is the first study to characterize circulating levels of cell-specific MPs after hepatic I/R injury and suggests that MPs derived from platelets and neutrophils serve as markers of inflammatory injury and may be active participants in this process. In contrast, MPs derived from endothelial cells increase after the injury response during the reparative phase and may be important in angiogenesis that occurs in the regenerating liver.
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Freeman
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Ralph C
authors.initials: RC
authors.lastname: Quillin
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Wilson
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nojima
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Bobby L
authors.initials: BL
authors.lastname: Johnson
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Sutton
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Schuster
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Blanchard
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Edwards
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Charles C
authors.initials: CC
authors.lastname: Caldwell
authors.affiliation: Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
authors.forename: Alex B
authors.initials: AB
authors.lastname: Lentsch
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000473:pathology; D055252:Cell-Derived Microparticles / Q000473:pathology*; D042783:Endothelial Cells / Q000473:pathology; D008099:Liver / Q000293:injuries* / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D051379:Mice; D009504:Neutrophils / Q000473:pathology; D012038:Regeneration; D015427:Reperfusion Injury / Q000473:pathology* / Q000503:physiopathology