Dual Contrast Molecular Imaging Allows Noninvasive Characterization of Myocardial Ischemia/Reperfusion Injury After Coronary Vessel Occlusion in Mice by MRI

Background —Inflammation and myocardial necrosis play important roles in ischemia/reperfusion injury after coronary artery occlusion and recanalization. The detection of inflammatory activity and the extent of myocardial necrosis itself are of great clinical and prognostic interest. We developed a dual, non-invasive imaging approach using molecular magnetic resonance imaging (MRI) in an in vivo mouse model of myocardial ischemia and reperfusion. Methods and Results —Ischemia/reperfusion injury was induced in 10 week old C57BL/6N mice by temporary ligation of the “left anterior descending coronary artery“(LAD). Activated platelets were targeted with a contrast agent consisting of microparticles of iron oxide (MPIO) conjugated to a single-chain antibody directed against a ligand-induced binding site (LIBS) on activated glycoprotein (GP)IIb/IIIa (=LIBS-MPIO). After injection and imaging of LIBS-MPIO, late gadolinium enhancement (LGE) was used to depict myocardial necrosis; these imaging experiments were also performed in P2Y 12-/- mice. All imaging results were correlated to immunohistochemistry findings. Activated platelets were detectable by MRI via a significant signal effect caused by LIBS-MPIO in the area of LAD occlusion two hours after reperfusion. In parallel, LGE identified the extent of myocardial necrosis. Immunohistochemistry confirmed that LIBS-MPIO significantly bound to microthrombi in reperfused myocardium. Only background-binding was found in P2Y 12-/- mice. Conclusions —Dual molecular imaging of myocardial ischemia/reperfusion injury allows characterization of platelet-driven inflammation by LIBS-MPIO as well as myocardial necrosis by LGE. This non-invasive imaging strategy is of clinical interest for both diagnostic and prognostic purposes, and highlights the potential of molecular MRI for characterizing ischemia/reperfusion injury. glycoprotein (GP)IIb/IIIa (=LIBS-MPIO). After injection and imaging of LIBS--MPMPMPIOIOO,, lalaatetete gadolinium enhancement (LGE) was used to depict myocardial necrosis; these imaging experiments were also performed in P2Y 12-/- mice. All imaging results were correlated to mmmmumumunonohiiststtoococheemimiststryry finindidngngs.s. Acctivavteed plataeleleetetss werere ddetecttababable bby y MMRI viia a a signgnifiicicant iiignnnala effect cacauusseed bbbyyy LILILIBSBSBS-M-M-MPIPIIOO O ininn tthhe aareea offf LLLADDD oocccccluuusisionoon ttwowo hoouoursrss aaaftftererr reepepeerrfufuusisionoon.. In f papaararalllllell,, LGLGE E E ididenenentiififieeded thehe eeextxtxtenent ofofo mmmyyoyocacaardddiaial nneececrroossisis.s. IImmmmmuununoohistotochcheeemmimiststryryy ccononffirrmrmeedd tttha LIBSBS-MMPIPIOO sisigngifficicanatlyy bobounundd toto microroththrorombmbi i in rrepepererfufusesed d mymyococarardiiumum. OnOnlyl bbacakgkgrorounud-d-binding g wass fofofoununund dd ininin PPP2Y2Y2 12112-/--/-/- mmicicicee.