A comprehensive and longitudinal cardiac magnetic resonance imaging study of the impact of coronary ischemia duration on myocardial damage in a highly translatable animal model

Cardioprotection exerted by intravenous statin at index myocardial infarction event attenuates cardiac damage upon recurrent infarction

AIMS

Recurrent acute myocardial infarction (RE-AMI) is a frequent complication after STEMI, and its association with stent thrombosis can be life-threatening. Intravenous atorvastatin (IV-atorva) administration during AMI has been shown to limit infarct size and adverse cardiac remodelling. We determined by cardiac magnetic resonance (CMR) whether the cardioprotection exerted by IV-atorva at the index AMI event translates into a better prognosis upon RE-AMI in dyslipidemic pigs.

METHODS AND RESULTS

Hypercholesterolemic pigs underwent a first AMI (90-min coronary balloon occlusion). During ongoing ischaemia, animals received IV-atorva or vehicle. Forty days later, animals underwent RE-AMI and were sacrificed on Day 43. All animals remained on p.o. atorvastatin and a high-cholesterol diet from the first AMI until sacrifice. Serial CMR analysis was performed on Day 3 post-AMI, prior- (Day 40) and post-RE-AMI (Day 43). No differences were detected in oedema formation in both animal groups during AMI and RE-AMI. Gadolinium DE-CMR revealed smaller infarcts in IV-atorva-treated animals at index event at 3 and 40 days post-AMI compared to vehicle-administered pigs (P < 0.05). CMR analyses post-RE-AMI revealed smaller infarcts in the animals treated with IV-atorva at index event than in the vehicle-administered pigs. These IV-atorva at index event benefits were associated with higher left ventricular (LV) ejection fraction and normal LV wall motion in the jeopardized myocardium at RE-AMI (P < 0.05 vs. vehicle). The scar region of RE-AMI of animals treated with IV-atorva at index event showed reduced cardiac inflammatory infiltrate, apoptosis and senescence activation, and increased reparative fibrosis and neovessel formation vs. vehicle-administered pigs. Animals treated with IV-atorva at index event also showed lower C-reactive protein and higher interleukin-10 plasma levels in the setting of RE-AMI.

CONCLUSION

The cardioprotection afforded by IV-atorva administration during an index-AMI event shows a legacy effect attenuating myocardial damage and preserving cardiac contractile function upon RE-AMI. The potential benefits of this intravenous approach should be tested in the clinical setting.

Pigs as Models to Test Cardiovascular Devices

Pigs as laboratory animals are used in preclinical studies aimed at developing medical devices for cardiac surgery. The anatomy of the cardiovascular system of these animals has been well studied and acknowledged as suitable for use and the testing of new cardiovascular devices developed for humans. However, there are no morphometric characteristics of the aortic root and thoraco-abdominal part of porcine aorta. This can lead to difficulties in experimental surgery and even result in the death of experimental animals due to the mismatch in the size of the implantable devices. Thus, such information is essential to enhance the efficiency of surgical technologies used for eliminating aortic pathologies in their various sections. The purpose of our research is to study the anatomy of the aorta in mini pigs and to assess whether the size, age, and sex of the animals affect the size of the main structures in their aortas. In addition, we attempted to compare the results obtained by transesophageal echocardiography (TEE) and angiography. We studied 28 laboratory mini pigs, dividing them into three groups by body weight (40-70 kg, 71-90 kg, and 90 kg). We did not find any relationship between the external somatometric characteristics of the animals and the size of their aortas. Animals have individual anatomical variability in their cardiovascular systems, which means that they need to be examined in terms of preoperative planning by any available method-echocardiography, angiography, or multispiral computed tomography (CT).

Characterizing the immune response to myocardial infarction in pigs

Though myocardial infarction (MI) in pigs is a well-established translational large animal model, it has not yet been widely used for immunotherapy studies, and a comprehensive description of the immune response to MI in this species is lacking. We induced MI in Landrace pigs by balloon occlusion of the left anterior descending artery over 90 min. Within 14 days, the necrotic myocardium was progressively replaced by scar tissue with involvement of myofibroblasts. We characterized the immune response in the heart ex vivo by (immuno)histology, flow cytometry, and RNA sequencing of myocardial tissue on days 3, 7, and 14 after MI. Besides a clear predominance of myeloid cells among heart-infiltrating leukocytes, we detected activated T cells and an increasing proportion of CD4+ Foxp3+ regulatory T cells (Treg), especially in the infarct core-findings that closely mirror what has been observed in mice and humans after MI. Transcriptome data indicated inflammatory activity that was persistent but markedly changing in character over time and linked to extracellular matrix biology. Analysis of lymphocytes in heart-draining lymph nodes revealed significantly higher proliferation rates of T helper cell subsets, including Treg on day 7 after MI, compared to sham controls. Elevated frequencies of myeloid progenitors in the spleen suggest that it might be a site of emergency myelopoiesis after MI in pigs, as previously shown in mice. We thus provide a first description of the immune response to MI in pigs, and our results can aid future research using the species for preclinical immunotherapy studies.

Recombinant human soluble domain of CD39L3 and ticagrelor: cardioprotective effects in experimental myocardial infarction

BACKGROUND AND AIMS

The ecto-nucleoside triphosphate diphosphohydrolases of the CD39 family degrade ATP and ADP into AMP, which is converted into adenosine by the extracellular CD73/ecto-5-nucleotidase. This pathway has been explored in antithrombotic treatments but little in myocardial protection. We have investigated whether the administration of solCD39L3 (AZD3366) confers additional cardioprotection to that of ticagrelor alone in a pre-clinical model of myocardial infarction (MI).

METHODS

Ticagrelor-treated pigs underwent balloon-induced MI (90 min) and, before reperfusion, received intravenously either vehicle, 1 mg/kg AZD3366 or 3 mg/kg AZD3366. All animals received ticagrelor twice daily for 42 days. A non-treated MI group was run as a control. Serial cardiac magnetic resonance (baseline, Day 3 and Day 42 post-MI), light transmittance aggregometry, bleeding time, and histological and molecular analyses were performed.

RESULTS

Ticagrelor reduced oedema formation and infarct size at Day 3 post-MI vs. controls. A 3 mg/kg AZD3366 provided an additional 45% reduction in oedema and infarct size compared with ticagrelor and a 70% reduction vs. controls (P < .05). At Day 42, infarct size declined in all ticagrelor-administered pigs, particularly in 3 mg/kg AZD3366-treated pigs (P < .05). Left ventricular ejection fraction was diminished at Day 3 in placebo pigs and worsened at Day 42, whereas it remained unaltered in ticagrelor ± AZD3366-administered animals. Pigs administered with 3 mg/kg AZD3366 displayed higher left ventricular ejection fraction upon dobutamine stress at Day 3 and minimal dysfunctional segmental contraction at Day 42 (χ2P < .05 vs. all). Cardiac and systemic molecular readouts supported these benefits. Interestingly, AZD3366 abolished ADP-induced light transmittance aggregometry without affecting bleeding time.

CONCLUSIONS

Infusion of AZD3366 on top of ticagrelor leads to enhanced cardioprotection compared with ticagrelor alone.