title: Platelet-endothelial cell interactions in murine antigen-induced arthritis.
abstract: OBJECTIVE
  Growing evidence supports the substantial pathophysiological impact of platelets on the development of rheumatoid arthritis. At present there are no methods for studying these cellular mechanisms in vivo. The aim of this study was to visualize and investigate platelet-endothelial cell interaction in the knee joint of mice with antigen-induced arthritis (AiA) by means of intravital microscopy.
  
  
  METHODS
  In 14 mice (Balbc) intravital microscopic assessment was performed on day 8 after AiA induction in two groups (controls, AiA). The severity of AiA was assessed by measuring knee joint swelling and by histological scoring. Ex vivo fluorescently labelled rolling and adherent platelets and leucocyte-endothelium interactions were investigated by intravital fluorescence microscopy.
  
  
  RESULTS
  Swelling of the knee joint as well as histological score was significantly enhanced in arthritic animals compared with controls. In control mice intravital microscopy revealed low baseline rolling and sticking of leucocytes and fluorescently labelled platelets. AiA induced a significant increase in the fraction of rolling leucocytes (3 times) and rolling platelets (6 times) compared to the control group. Furthermore, AiA induction resulted in a significantly enhanced number of adherent leucocytes (3-fold) and adherent platelets (12-fold) in comparison with control animals.
  
  
  CONCLUSIONS
  Platelet kinetics were directly analysed using intravital microscopy in the arthritic microcirculation in vivo for the first time. We provide the first evidence that platelets accumulate in arthritic vessels, indicating platelet activation due to AiA. Platelet recruitment and subsequent activation might play an important role in the pathogenesis of rheumatoid arthritis.
authors.affiliation: Department of Orthopedics, Klinikum Grosshadern, Marchioninistr. 15, Ludwig-Maximilians-University, 81377 Munich, Germany. marcus.schmitt-sody@med.uni-muenchen.de
authors.forename: M
authors.initials: M
authors.lastname: Schmitt-Sody
authors.forename: A
authors.initials: A
authors.lastname: Klose
authors.forename: O
authors.initials: O
authors.lastname: Gottschalk
authors.forename: P
authors.initials: P
authors.lastname: Metz
authors.forename: H
authors.initials: H
authors.lastname: Gebhard
authors.forename: S
authors.initials: S
authors.lastname: Zysk
authors.forename: M E
authors.initials: ME
authors.lastname: Eichhorn
authors.forename: T M
authors.initials: TM
authors.lastname: Hernandez-Richter
authors.forename: V
authors.initials: V
authors.lastname: Jansson
authors.forename: A
authors.initials: A
authors.lastname: Veihelmann
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000097:blood* / Q000473:pathology; D001792:Blood Platelets / Q000502:physiology*; D002450:Cell Communication; D004730:Endothelium, Vascular / Q000473:pathology*; D005260:Female; D007962:Leukocytes / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008833:Microcirculation; D008856:Microscopy, Fluorescence; D015539:Platelet Activation; D010973:Platelet Adhesiveness