Towards Stratifying Ischemic Components by Cardiac MRI and Multifunctional Stainings in a Rabbit Model of Myocardial Infarction

Abstract

Objectives: We sought to identify critical components of myocardial infarction (MI) including area at risk (AAR), MI-core and salvageable zone (SZ) by using cardiac magnetic resonance imaging (cMRI) and multifunctional stainings in rabbits.Materials and Methods: Fifteen rabbits received 90-min coronary artery (CA) ligation and reopening to induce reperfused MI. First-pass perfusion weighted imaging (PWI90') was performed immediately before CA reperfusion. Necrosis avid dye Evans blue (EB) was intravenously injected for later MI-core detection. One-day later, cMRI with T2-weighted imaging (T2WI), PWI24h and delayed enhancement (DE) T1WI was performed at a 3.0T clinical scanner. The heart was excised and CA was re-ligated with aorta infused by red-iodized-oil (RIO). The heart was sliced into 3-mm sections for digital radiography (DR), histology and planimetry with myocardial salvage index (MSI) and perfusion density rate (PDR) calculated.Results: There was no significant difference between MI-cores defined by DE-T1WI and EB-staining (31.13±8.55% vs 29.80±7.97%; p=0.74). The AAR was defined similarly by PWI90' (39.93±9.51%), RIO (38.82±14.41%) and DR (38.17±15.98%), underestimated by PWI24h (36.44±5.31%), but overestimated (p<0.01) by T2WI (56.93±8.87%). Corresponding MSI turned out to be 24.17±9.5% (PWI90'), 21.97±9.41% (DR) and 22.68±9.65% (RIO), which were significantly (p<0.01) higher and lower than that with PWI24h (15.15±7.34%) and T2WI (45.52±7.5%) respectively. The PDR differed significantly (p<0.001) between normal myocardium (350.6±33.1%) and the AAR (31.2±15%), suggesting 11-times greater blood perfusion in normal myocardium over the AAR.Conclusion: The introduced rabbit platform and new staining techniques together with the use of a 3.0T clinical scanner for cMRI enabled visualization of MI components and may contribute to translational cardiac imaging research for improved theranostic management of ischemic heart disease.

Evans Blue Dye: A Revisit of Its Applications in Biomedicine

“…Many researchers used EB dye to discriminate among injured cells in various animal models, such as the zebrafish models of neuromuscular disease [ 14 ], mouse models of muscular dystrophy [ 90 ] and experimental injury and repair [ 91 ], rat models of stroke and cardiomyocyte injury [ 92 ], myocardial infarction core in a rabbit model [ 32 ] ( Figure 1 ), and reperfused partial liver infarction model in rats [ 33 ] ( Figure 2 ).…”

“… Evaluation of myocardial infarction core (MI-core), area at risk (AAR), and salvageable zone (SZ) in a rabbit with reperfused MI by in vivo and ex vivo imaging techniques and dynamic imaging quantification [ 32 ]. (a) Delayed, enhanced cardiac magnetic resonance imaging displays the MI-core as a transmural hyperenhanced area involving anterior papillary muscle; (b) T2-weighted imaging shows an extensive hyperintense region in the anterolateral wall; (c) digital radiograph of the red iodized oil-stained heart section shows a filling defect with few collateral vessels in the anterolateral wall in contrast to the rest of opaque left ventricle; (d) photograph of the heart section stained by multifunctional staining depicts the MI-core as an Evans blue dye-stained blue lesion simulating what is seen in (a) and shows the normal ventricular wall in red leaving the AAR (including the blue MI-core) unstained, which perfectly matches with the AAR in (c) and whitish zones which are suggestive of the SZ; (e) photomacroscopy of HE-stained heart slice views the MI-core as a hemorrhagic infarct similar in size to the blue lesion in (f); (f) photomicroscopy (×100) of HE-stained heart slice confirms the presence of the AAR (necrotic MI-core plus the viable but inflammatory SZ) and remote normal myocardium (NM) (reprinted and modified with permission from Feng Y, Chen F, Ma Z, Dekeyzer F, Yu J, Xie Y, Cona MM, Oyen R, Ni Y. Theranostics .…”

A multifunctional contrast dye for morphological research

“…Preclinical in vivo imaging research relies on postmortem verifications to gain insight and draw reliable conclusions (Feng, , 2013(Feng, , 2014Ni et al, 2009;Wu et al, 2009), which prompted us to develop RIO as a multifunctional contrast dye in the context. Indeed, implementation of RIO has further empowered our existing platform based on rabbit models for research in ischemic heart disease (Feng, 2013(Feng, , 2014(Feng, , 2014a.…”

“…Nowadays, LPD with its variable formulations has been not only extensively and intensively applied in many clinical interventional procedures (Id eea and Guiuba, 2013;Konno 1990;Konno et al, 1983;), but also used, after re-formulation into RIO, in preclinical imaging-based theragnostic research (Feng 2013(Feng , 2014(Feng , 2014a.…”

Monitoring reperfused myocardial infarction with delayed left ventricular systolic dysfunction in rabbits by longitudinal imaging

“…A medium sized rabbit heart has many similarities to the human heart in terms of cardiovascular anatomy, ventricular performance, cardiac metabolism, electrophysiology, coronary artery distribution, and collateralization after an acute event. In addition, with the lower phylogenetic scale, longer life span, strain-specific characteristics and low cost, the rabbit is a suitable species for cardiac research (13,25,26). Technically, the dimension of a rabbit heart is large enough to study with clinical imaging scanners and small enough to just fit in a standard glass slide for entire-heartslice histomorphologic studies, both of great translational significance.…”