title: In vivo imaging of thrombin activity in experimental thrombi with thrombin-sensitive near-infrared molecular probe.
abstract: OBJECTIVE
  Thrombin, a serine protease, plays an important role in thrombosis as well as other cellular and developmental processes. In this study, we investigated the ability of a novel thrombin-activatable molecular probe to provide in vivo images of thrombin activity in experimental thrombi.
  
  
  RESULTS
  The thrombin probe consists of a near-infrared (NIR) fluorochrome attached to a delivery vehicle via a thrombin-specific oligopeptide substrate. In human blood, endogenous thrombin activated the thrombin probe and increased the fluorescence signal by 18-fold (P=0.008). Hirudin, a specific thrombin inhibitor, suppressed probe activation by 82% (P=0.007). Imaging of in vivo thrombin activity was then investigated in acute experimental murine thrombosis models up to 12 hours. After systemic thrombin probe injection, focal NIR fluorescence signal enhancement was rapidly detected within acute and subacute thrombi. In contrast, no thrombosis signal enhancement was seen in similar experiments with a control NIR fluorochrome.
  
  
  CONCLUSIONS
  Thrombin activity can be imaged in vivo by using a novel thrombin-activatable and thrombin-specific NIR molecular probe. The thrombin probe could enhance the understanding of the role of thrombin in thrombogenesis and other homeostatic and pathological conditions.
authors.affiliation: Center for Molecular Imaging Research, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, USA. fjaffer@partners.org
authors.forename: Farouc A
authors.initials: FA
authors.lastname: Jaffer
authors.forename: Ching-Hsuan
authors.initials: CH
authors.lastname: Tung
authors.forename: Robert E
authors.initials: RE
authors.lastname: Gerszten
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
mesh_terms: D000328:Adult; D000818:Animals; D003952:Diagnostic Imaging / Q000379:methods*; D004195:Disease Models, Animal; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D015335:Molecular Probes / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013917:Thrombin / Q000378:metabolism*; D013927:Thrombosis / Q000378:metabolism*
chemical_list: D015335:Molecular Probes; D013917:Thrombin