Fibrin-Targeted Magnetic Resonance Imaging Allows In Vivo Quantification of Thrombus Fibrin Content and Identifies Thrombi Amenable for Thrombolysis

Abstract

Objective Deep venous thrombosis is a major health problem. Thrombolytic therapies are effective in recanalizing the veins and preventing post-thrombotic complications, but there is no consensus on selection criteria. The aim of this study was to investigate a fibrin-specific MRI contrast agent (EP-2104R) for the accurate quantification of thrombus’ fibrin content in vivo and for the identification of thrombus suitable for thrombolysis. Approach and Results Venous thrombosis was induced in the inferior vena cava of 8- to 10-week-old male BALB/C mice and MRI performed 2, 4, 7, 10, 14, and 21 days later. Eighteen mice were scanned at each time point pre and 2 hours post injection of EP-2104R (8.0 μmol/kg) with 12 mice at each time point used to correlate fibrin contrast uptake with thrombus’ histological stage and fibrin content. Six mice at each time point were immediately subjected to intravascular thrombolytic therapy (10 mg/kg of tissue-type plasminogen activator). Mice were imaged to assess response to lytic therapy 24 hours after thrombolytic treatment. Two mice at each time point were scanned post injection of 0.2 mmol/kg of Gd-DTPA (gadolinium with diethylenetriaminepentacetate, Magnevist, Schering AG, Berlin, Germany) for control purpose. Contrast uptake was correlated positively with the fibrin content of the thrombus measured by Western blotting (R2=0.889; P<0.001). Thrombus relaxation rate (R1) post contrast and the change in visualized thrombus size on late gadolinium enhancement inversion recovery MRI pre–EP-2104R and post–EP-2104R injection were the best predictors for successful thrombolysis (area under the curve, 0.989 [95% confidence interval, 0.97–1.00] and 0.994 [95% confidence interval, 0.98–1.00] respectively). Conclusions MRI with a fibrin-specific contrast agent accurately estimates thrombus fibrin content in vivo and identifies thrombi that are amenable for thrombolysis.

Noninvasive Imaging of Early Venous Thrombosis by 19 F Magnetic Resonance Imaging With Targeted Perfluorocarbon Nanoemulsions

“…To overcome this limitation, gadoliniumbased probes raised against fibrin within the thrombus have been developed (EP-2104R). [6][7][8][9][10][11] Another specific marker of developing thrombi is factor XIIIa (FXIIIa), which cross-links α2-antiplasmin with fibrin during the early phase of thrombus formation. 12,13 Probes based on α2-antiplasmin have been used for ex vivo or in vivo labeling of thrombi by near-infrared fluorescence, scintigraphy, or gadolinium-enhanced 1 H MRI.…”

From Molecular Imaging to Pathogenesis and Vice Versa…

“…Feasibility of thrombus detection with this nanoparticle has been demonstrated in >5 different animal models of arterial and venous thrombosis. [12][13][14][15][16][17] Also, clinical feasibility of thrombus imaging was recently shown in a small group of patients with thrombus in the left ventricle, left or right atrium, thoracic aorta, or carotid artery. 18 Similar to the present study, EP-2104R MRI was successfully used to predict the effect of tissue-type plasminogen activator in mice with inferior vena cava thrombi.…”

“…18 Similar to the present study, EP-2104R MRI was successfully used to predict the effect of tissue-type plasminogen activator in mice with inferior vena cava thrombi. 12 When compared with 64 Cu-FBP7, EP-2104R benefits from the high spatial resolution and lack of radiation burden associated with MRI. However, the use of EP-2104R requires a prescan and postscan, which could become a limitation in acute clinical situations.…”

“…This is especially relevant for detecting the older thrombi with lower fibrin content. 12 Besides fibrin, FXIIIa [19][20][21][22][23][24][25] and thrombin 26,27 have been evaluated as targets for thrombus imaging in the preclinical studies ( Figure). Thrombin and FXIIIa are important factors in the coagulation cascade, and probes targeting these molecules promise to be excellent research tools for elucidation of the temporal roles of these factors in vivo.…”

Fe₃O₄-based PLGA nanoparticles as MR contrast agents for the detection of thrombosis

“…[12][13][14][15][16][17] The fibrin-targeted MR molecular probe EP-2104R has entered clinical trials with encouraging results. 19 Comparatively Gd-DTPA, SPIO and USPIO have the advantages of long half-lives, high relaxation rates, and minimal side effects. 20,21 Most previous studies of thrombosis detection molecules have focused on their physicochemical properties in vitro and targeting abilities in vivo.…”