Bifunctional staining for ex vivo determination of area at risk in rabbits with reperfused myocardial infarction

AIM: To develop a method for studying myocardial area at risk(AAR) in ischemic heart disease in correlation with cardiac magnetic resonance imaging(c MRI). METHODS: Nine rabbits were anesthetized, intubated and subjected to occlusion and reperfusion of the left circumflex coronary artery(LCx) to induce myocardial infarction(MI). ECG-triggered c MRI with delayed en-hancement was performed at 3.0 T. After euthanasia, the heart was excised with the LCx re-ligated. Bifunctional staining was performed by perfusing the aorta with a homemade red-iodized-oil(RIO) dye. The heart was then agar-embedded for ex vivo magnetic resonance imaging and sliced into 3 mm-sections. The AAR was defined by RIO-staining and digital radiography(DR). The perfusion density rate(PDR) was derived from DR for the AAR and normal myocardium. The MI was measured by in vivo delayed enhancement(i DE) and ex vivo delayed enhancement(e DE) c MRI. The AAR and MI were compared to validate the bifunctional straining for cardiac imaging research. Linear regression with Bland-Altman agreement, one way-ANOVA with Bonferroni's multiple comparison, and paired t tests were applied for statistics.RESULTS: All rabbits tolerated well the surgical procedure and subsequent c MRI sessions. The openchest occlusion and close-chest reperfusion of the LCx, double suture method and bifunctional staining were successfully applied in all animals. The percentage MI volumes globally(n = 6) and by slice(n = 25) were 36.59% ± 13.68% and 32.88% ± 12.38% on i DE, and 35.41% ± 12.25% and 32.40% ± 12.34% on e DE. There were no significant differences for MI determination with excellent linear regression correspondence(r global = 0.89; r slice = 0.9) between i DE and e DE. The percentage AAR volumes globally(n = 6) and by slice(n = 25) were 44.82% ± 15.18% and 40.04% ± 13.64% with RIO-staining, and 44.74% ± 15.98% and 40.48% ± 13.26% by DR showing high correlation in linear regression analysis(r global = 0.99; r slice = 1.0). The mean differences of the two AAR measurements on BlandAltman were almost zero, indicating RIO-staining and DR were essentially equivalent or inter-replaceable. The AAR was significantly larger than MI both globally and slice-by-slice(P < 0.01). After correction with the background and the blank heart without bifunctional staining(n = 3), the PDR for the AAR and normal myocardium was 32% ± 15% and 35.5% ± 35%, respectively,which is significantly different(P < 0.001), suggesting that blood perfusion to the AAR probably by collateral circulation was only less than 10% of that in the normal myocardium.CONCLUSION: The myocardial area at risk in ischemic heart disease could be accurately determined postmortem by this novel bifunctional staining, which may substantially contribute to translational cardiac imaging research.

Updated developments on molecular imaging and therapeutic strategies directed against necrosis

Cell death plays important roles in living organisms and is a hallmark of numerous disorders such as cardiovascular diseases, sepsis and acute pancreatitis. Moreover, cell death also plays a pivotal role in the treatment of certain diseases, for example, cancer. Noninvasive visualization of cell death contributes to gained insight into diseases, development of individualized treatment plans, evaluation of treatment responses, and prediction of patient prognosis. On the other hand, cell death can also be targeted for the treatment of diseases. Although there are many ways for a cell to die, only apoptosis and necrosis have been extensively studied in terms of cell death related theranostics. This review mainly focuses on molecular imaging and therapeutic strategies directed against necrosis. Necrosis shares common morphological characteristics including the rupture of cell membrane integrity and release of cellular contents, which provide potential biomarkers for visualization of necrosis and necrosis targeted therapy. In the present review, we summarize the updated joint efforts to develop molecular imaging probes and therapeutic strategies targeting the biomarkers exposed by necrotic cells. Moreover, we also discuss the challenges in developing necrosis imaging probes and propose several biomarkers of necrosis that deserve to be explored in future imaging and therapy research.

Evaluation of necrosis avidity of radioiodinated 5-hydroxytryptophan and its potential applications in myocardial infarction imaging

This study aimed to seek necrosis avid agents with high safety from DNA binding agents. The interaction of 5-hydroxytryptophan(5-HTP) with DNA was investigated by a series of spectroscopic studies. Then, 5-HTP was labeled with iodine-131([^(131)I]5-HTP) and the necrosis avidity of [^(131)I]5-HTP was evaluated by in vitro cell binding assays, in vivo biodistribution experiments and blocking experiment. Finally, the potential of [^(131)I]5-HTP to image necrotic myocardium was explored in rat models with myocardial infarction by SPECT/CT imaging. Results showed that 5-HTP bound to DNA in groove binding mode and the binding constant was 1.69×10~4 L/mol. [~(^(131))I]5-HTP showed specific affinity to necrotic A549 cells,which might be related to cell nucleus. Biodistribution and autoradiography results showed preferential accumulation of [^(131)I]5-HTP in necrotic muscle(necrotic/viable muscle ratio: 6.95 ? 0.68 at 3 h postinjection(p.i.)), which could be blocked by 5-HTP with 66.7% decline, indicating that [^(131)I]5-HTP might share the same necrotic targets with 5-HTP. On SPECT/CT images, a hotspot was clearly observed at 3h p.i.in the necrotic myocardium while not in the control myocardium. In conclusion, [^(131) I]5-HTP is a novel necrosis avid agent and can rapidly visualize necrotic myocardium at 3 h p.i. The necrosis avidity mechanism of [^(131) I]5-HTP may be attributed to its interactions with exposed DNA in the necrotic tissues.