title: Thrombospondin-1: a unique marker to identify in vitro platelet activation when monitoring in vivo processes.
abstract: BACKGROUND
  Measuring platelet activation in patients has become a potent method to investigate pathophysiological processes. However, the commonly applied markers are sensitive to detrimental influences by in vitro platelet activation during blood analysis.
  
  
  OBJECTIVE
  Protein isoforms of platelet-derived thrombospondin-1 (TSP-1) were investigated for their potential to identify in vitro platelet activation when monitoring in vivo processes.
  
  
  METHODS
  TSP-1 was determined in plasma, serum or supernatant of purified platelets by ELISA and immunoblotting and was compared with standard markers of platelet activation. A collective of 20 healthy individuals and 30 cancer patients was analyzed.
  
  
  RESULTS
  While in vitro platelet degranulation led to a selective increase in the 200-kDa full-length molecule, an in vivo process involving platelet activation such as wound healing resulted in the predominant rise of the 140-kDa TSP-1 protein. The physiological ratio of circulating TSP-1 variants was determined and a cut-off level at 1.0 was defined to identify plasma samples with artificial in vitro platelet activation exceeding the cut-off level. In contrast, cancer patients known to frequently exhibit increased in vivo activation of platelets presented with a significantly decreased ratio of TSP-1 variants as compared with healthy volunteers.
  
  
  CONCLUSIONS
  In comparison to standard platelet markers, TSP-1 constitutes a sensitive and stable parameter suited to monitor in vitro platelet activation. The analysis of TSP-1 protein isoforms further offers a valuable tool to reliably discriminate between in vitro and in vivo effects, to exclude variability introduced during blood processing and improve clinical monitoring.
authors.affiliation: Department of Surgery, General Hospital Institute of Physiology, Medical University of Vienna, Vienna, Austria.
authors.forename: P
authors.initials: P
authors.lastname: Starlinger
authors.forename: H P
authors.initials: HP
authors.lastname: Moll
authors.forename: A
authors.initials: A
authors.lastname: Assinger
authors.forename: C
authors.initials: C
authors.lastname: Nemeth
authors.forename: K
authors.initials: K
authors.lastname: Hoetzenecker
authors.forename: B
authors.initials: B
authors.lastname: Gruenberger
authors.forename: T
authors.initials: T
authors.lastname: Gruenberger
authors.forename: I
authors.initials: I
authors.lastname: Kuehrer
authors.forename: S F
authors.initials: SF
authors.lastname: Schoppmann
authors.forename: M
authors.initials: M
authors.lastname: Gnant
authors.forename: C
authors.initials: C
authors.lastname: Brostjan
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000097:blood; D015539:Platelet Activation; D020033:Protein Isoforms; D011994:Recombinant Proteins / Q000737:chemistry; D013696:Temperature; D019700:Thrombospondin 1 / Q000097:blood* / Q000737:chemistry; D013997:Time Factors; D014945:Wound Healing
chemical_list: D020033:Protein Isoforms; D011994:Recombinant Proteins; D019700:Thrombospondin 1