Molecular MRI of early thrombus formation using a bimodal alpha2-antiplasmin-based contrast agent

JACC Cardiovasc Imaging. 2009 Aug;2(8):987-96. doi: 10.1016/j.jcmg.2009.03.015.


Objectives: We aimed to investigate whether early thrombus formation can be visualized with in vivo magnetic resonance imaging (MRI) by the use of a novel bimodal alpha(2)-antiplasmin-based contrast agent (CA).

Background: Thrombus formation plays a central role in several vascular diseases. During the early phases of thrombus formation, activated factor XIII (FXIIIa) covalently cross-links alpha(2)-antiplasmin to fibrin, indicating the potential of alpha(2)-antiplasmin-based CAs in the detection of early thrombus formation.

Methods: A bimodal CA was synthesized by coupling gadolinium-diethylene triamine pentaacetic acid and rhodamine to an alpha(2)-antiplasmin-based peptide. For the control CA, a glutamine residue essential for cross-linking was replaced by alanine. In vitro-generated thrombi were exposed to both CAs and imaged by MRI and 2-photon laser-scanning microscopy. Immunohistochemistry was performed on human pulmonary thromboemboli sections to determine the presence of alpha(2)-antiplasmin and FXIII in different thrombus remodeling phases. In vivo feasibility of the CA in detecting early thrombus formation specifically was investigated with MRI.

Results: In vitro-generated thrombi exposed to the alpha(2)-antiplasmin-based CA showed hyperintense magnetic resonance signal intensities at the thrombus edge. No hyperintense signal was observed when we used the alpha(2)-antiplasmin-based CA in the presence of FXIII inhibitor dansylcadaverine nor when we used the control CA. Two-photon laser-scanning microscopy demonstrated that the alpha(2)-antiplasmin-based CA bound to fibrin. Immunohistochemistry demonstrated substantial alpha(2)-antiplasmin staining in fresh compared with lytic and organized thrombi. The administration of CA in vivo within seconds after inducing thrombus formation increased contrast-to-noise ratios (CNRs 2.28 +/- 0.39, n=6) at the site of thrombus formation compared with the control CA (CNRs -0.14 +/- 0.55, p = 0.003, n = 6) and alpha(2)-antiplasmin-based CA administration 24 to 48 h after thrombus formation (CNRs 0.11 +/- 0.23, p = 0.006, n = 6).

Conclusions: A bimodal CA was developed, characterized, and validated. Our results showed that this bimodal CA enabled noninvasive in vivo magnetic resonance visualization of early thrombus formation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Animals
  • Cadaverine / analogs & derivatives
  • Cadaverine / pharmacology
  • Contrast Media*
  • Disease Models, Animal
  • Factor XIII / metabolism
  • Factor XIIIa / metabolism
  • Feasibility Studies
  • Fibrin / metabolism
  • Gadolinium DTPA* / analogs & derivatives
  • Gadolinium DTPA* / pharmacokinetics
  • Humans
  • Immunohistochemistry
  • Magnetic Resonance Imaging*
  • Mice
  • Microscopy, Fluorescence, Multiphoton
  • Predictive Value of Tests
  • Pulmonary Embolism / blood
  • Pulmonary Embolism / diagnosis*
  • Pulmonary Embolism / pathology
  • Reproducibility of Results
  • Rhodamines* / pharmacokinetics
  • Thrombosis / blood
  • Thrombosis / diagnosis*
  • Thrombosis / pathology
  • alpha-2-Antiplasmin* / analogs & derivatives
  • alpha-2-Antiplasmin* / pharmacology


  • Contrast Media
  • Rhodamines
  • alpha-2-Antiplasmin
  • Fibrin
  • Factor XIII
  • Factor XIIIa
  • monodansylcadaverine
  • Gadolinium DTPA
  • Cadaverine