title: Activated platelets in carotid artery thrombosis in mice can be selectively targeted with a radiolabeled single-chain antibody.
abstract: BACKGROUND
  Activated platelets can be found on the surface of inflamed, rupture-prone and ruptured plaques as well as in intravascular thrombosis. They are key players in thrombosis and atherosclerosis. In this study we describe the construction of a radiolabeled single-chain antibody targeting the LIBS-epitope of activated platelets to selectively depict platelet activation and wall-adherent non-occlusive thrombosis in a mouse model with nuclear imaging using in vitro and ex vivo autoradiography as well as small animal SPECT-CT for in vivo analysis.
  
  
  RESULTS
  LIBS as well as an unspecific control single-chain antibody were labeled with (111)Indium ((111)In) via bifunctional DTPA ( = (111)In-LIBS/(111)In-control). Autoradiography after incubation with (111)In-LIBS on activated platelets in vitro (mean 3866 ± 28 DLU/mm(2), 4010 ± 630 DLU/mm(2) and 4520 ± 293 DLU/mm(2)) produced a significantly higher ligand uptake compared to (111)In-control (2101 ± 76 DLU/mm(2), 1181 ± 96 DLU/mm(2) and 1866 ± 246 DLU/mm(2)) indicating a specific binding to activated platelets; P<0.05. Applying these findings to an ex vivo mouse model of carotid artery thrombosis revealed a significant increase in ligand uptake after injection of (111)In-LIBS in the presence of small thrombi compared to the non-injured side, as confirmed by histology (49630 ± 10650 DLU/mm(2) vs. 17390 ± 7470 DLU/mm(2); P<0.05). These findings could also be reproduced in vivo. SPECT-CT analysis of the injured carotid artery with (111)In-LIBS resulted in a significant increase of the target-to-background ratio compared to (111)In-control (1.99 ± 0.36 vs. 1.1 ± 0.24; P < 0.01).
  
  
  CONCLUSIONS
  Nuclear imaging with (111)In-LIBS allows the detection of platelet activation in vitro and ex vivo with high sensitivity. Using SPECT-CT, wall-adherent activated platelets in carotid arteries could be depicted in vivo. These results encourage further studies elucidating the role of activated platelets in plaque pathology and atherosclerosis and might be of interest for further developments towards clinical application.
authors.affiliation: Department of Cardiology and Angiology, University of Freiburg, Freiburg, Germany. timo.heidt@uniklinik-freiburg.de
authors.forename: Timo
authors.initials: T
authors.lastname: Heidt
authors.forename: Friederike
authors.initials: F
authors.lastname: Deininger
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Peter
authors.forename: Jürgen
authors.initials: J
authors.lastname: Goldschmidt
authors.forename: Annette
authors.initials: A
authors.lastname: Pethe
authors.forename: Christoph E
authors.initials: CE
authors.lastname: Hagemeyer
authors.forename: Irene
authors.initials: I
authors.lastname: Neudorfer
authors.forename: Andreas
authors.initials: A
authors.lastname: Zirlik
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Weber
authors.forename: Christoph
authors.initials: C
authors.lastname: Bode
authors.forename: Philipp T
authors.initials: PT
authors.lastname: Meyer
authors.forename: Martin
authors.initials: M
authors.lastname: Behe
authors.forename: Constantin
authors.initials: C
authors.lastname: von Zur Mühlen
mesh_terms: D000818:Animals; D001345:Autoradiography; D002341:Carotid Artery Thrombosis / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D000939:Epitopes / Q000276:immunology; D007205:Indium Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D051379:Mice; D015539:Platelet Activation / Q000502:physiology*; D011485:Protein Binding; D057127:Single-Chain Antibodies; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed
chemical_list: D000939:Epitopes; D007205:Indium Radioisotopes; D057127:Single-Chain Antibodies