Accurate assessment of LV function using the first automated 2D-border detection algorithm for small animals - evaluation and application to models of LV dysfunction

Malonate given at reperfusion prevents post-myocardial infarction heart failure by decreasing ischemia/reperfusion injury

The mitochondrial metabolite succinate is a key driver of ischemia/reperfusion injury (IRI). Targeting succinate metabolism by inhibiting succinate dehydrogenase (SDH) upon reperfusion using malonate is an effective therapeutic strategy to achieve cardioprotection in the short term (< 24 h reperfusion) in mouse and pig in vivo myocardial infarction (MI) models. We aimed to assess whether inhibiting IRI with malonate given upon reperfusion could prevent post-MI heart failure (HF) assessed after 28 days. Male C57BL/6 J mice were subjected to 30 min left anterior coronary artery (LAD) occlusion, before reperfusion for 28 days. Malonate or without-malonate control was infused as a single dose upon reperfusion. Cardiac function was assessed by echocardiography and fibrosis by Masson's trichrome staining. Reperfusion without malonate significantly reduced ejection fraction (~ 47%), fractional shortening (~ 23%) and elevated collagen deposition 28 days post-MI. Malonate, administered as a single infusion (16 mg/kg/min for 10 min) upon reperfusion, gave a significant cardioprotective effect, with ejection fraction (~ 60%) and fractional shortening (~ 30%) preserved and less collagen deposition. Using an acidified malonate formulation, to enhance its uptake into cardiomyocytes via the monocarboxylate transporter 1, both 1.6 and 16 mg/kg/min 10 min infusion led to robust long-term cardioprotection with preserved ejection fraction (> 60%) and fractional shortening (~ 30%), as well as significantly less collagen deposition than control hearts. Malonate administration upon reperfusion prevents post-MI HF. Acidification of malonate enables lower doses of malonate to also achieve long-term cardioprotection post-MI. Therefore, the administration of acidified malonate upon reperfusion is a promising therapeutic strategy to prevent IRI and post-MI HF.

Female Alms1-deficient mice develop echocardiographic features of adult but not infantile Alström syndrome cardiomyopathy

Alström syndrome (AS), a multisystem disorder caused by biallelic ALMS1 mutations, features major early morbidity and mortality due to cardiac complications. The latter are biphasic, including infantile dilated cardiomyopathy and distinct adult-onset cardiomyopathy, and poorly understood. We assessed cardiac function of Alms1 knockout (KO) mice by echocardiography. Cardiac function was unaltered in Alms1 global KO mice of both sexes at postnatal day 15 (P15) and 8 weeks. At 23 weeks, female - but not male - KO mice showed increased left atrial area and decreased isovolumic relaxation time, consistent with early restrictive cardiomyopathy, as well as reduced ejection fraction. No histological or transcriptional changes were seen in myocardium of 23-week-old female Alms1 global KO mice. Female mice with Pdgfra-Cre-driven Alms1 deletion in cardiac fibroblasts and in a small proportion of cardiomyocytes did not recapitulate the phenotype of global KO at 23 weeks. In conclusion, only female Alms1-deficient adult mice show echocardiographic evidence of cardiac dysfunction, consistent with the cardiomyopathy of AS. The explanation for sexual dimorphism remains unclear but might involve metabolic or endocrine differences between sexes.

An eNAMPT-neutralizing mAb reduces post-infarct myocardial fibrosis and left ventricular dysfunction

Myocardial infarction (MI) triggers adverse ventricular remodeling (VR), cardiac fibrosis, and subsequent heart failure. Extracellular nicotinamide phosphoribosyltransferase (eNAMPT) is postulated to play a significant role in VR processing via activation of the TLR4 inflammatory pathway. We hypothesized that an eNAMPT specific monoclonal antibody (mAb) could target and neutralize overexpressed eNAMPT post-MI and attenuate chronic cardiac inflammation and fibrosis. We investigated humanized ALT-100 and ALT-300 mAb with high eNAMPT-neutralizing capacity in an infarct rat model to test our hypothesis. ALT-300 was 99mTc-labeled to generate 99mTc-ALT-300 for imaging myocardial eNAMPT expression at 2 hours, 1 week, and 4 weeks post-IRI. The eNAMPT-neutralizing ALT-100 mAb (0.4 mg/kg) or saline was administered intraperitoneally at 1 hour and 24 hours post-reperfusion and twice a week for 4 weeks. Cardiac function changes were determined by echocardiography at 3 days and 4 weeks post-IRI. 99mTc-ALT-300 uptake was initially localized to the ischemic area at risk (IAR) of the left ventricle (LV) and subsequently extended to adjacent non-ischemic areas 2 hours to 4 weeks post-IRI. Radioactive uptake (%ID/g) of 99mTc-ALT-300 in the IAR increased from 1 week to 4 weeks (0.54 ± 0.16 vs. 0.78 ± 0.13, P < 0.01). Rats receiving ALT-100 mAb exhibited significantly improved myocardial histopathology and cardiac function at 4 weeks, with a significant reduction in the collagen volume fraction (%LV) compared to controls (21.5 ± 6.1% vs. 29.5 ± 9.9%, P < 0.05). Neutralization of the eNAMPT/TLR4 inflammatory cascade is a promising therapeutic strategy for MI by reducing chronic inflammation, fibrosis, and preserving cardiac function.

Echo2Pheno: a deep-learning application to uncover echocardiographic phenotypes in conscious mice

Echocardiography, a rapid and cost-effective imaging technique, assesses cardiac function and structure. Despite its popularity in cardiovascular medicine and clinical research, image-derived phenotypic measurements are manually performed, requiring expert knowledge and training. Notwithstanding great progress in deep-learning applications in small animal echocardiography, the focus has so far only been on images of anesthetized rodents. We present here a new algorithm specifically designed for echocardiograms acquired in conscious mice called Echo2Pheno, an automatic statistical learning workflow for analyzing and interpreting high-throughput non-anesthetized transthoracic murine echocardiographic images in the presence of genetic knockouts. Echo2Pheno comprises a neural network module for echocardiographic image analysis and phenotypic measurements, including a statistical hypothesis-testing framework for assessing phenotypic differences between populations. Using 2159 images of 16 different knockout mouse strains of the German Mouse Clinic, Echo2Pheno accurately confirms known cardiovascular genotype-phenotype relationships (e.g., Dystrophin) and discovers novel genes (e.g., CCR4-NOT transcription complex subunit 6-like, Cnot6l, and synaptotagmin-like protein 4, Sytl4), which cause altered cardiovascular phenotypes, as verified by H&E-stained histological images. Echo2Pheno provides an important step toward automatic end-to-end learning for linking echocardiographic readouts to cardiovascular phenotypes of interest in conscious mice.

In-ovo echocardiography for application in cardiovascular research

Preclinical cardiovascular research relies heavily on non-invasive in-vivo echocardiography in mice and rats to assess cardiac function and morphology, since the complex interaction of heart, circulation, and peripheral organs are challenging to mimic ex-vivo. While n-numbers of annually used laboratory animals worldwide approach 200 million, increasing efforts are made by basic scientists aiming to reduce animal numbers in cardiovascular research according to the 3R's principle. The chicken egg is well-established as a physiological correlate and model for angiogenesis research but has barely been used to assess cardiac (patho-) physiology. Here, we tested whether the established in-ovo system of incubated chicken eggs interfaced with commercially available small animal echocardiography would be a suitable alternative test system in experimental cardiology. To this end, we defined a workflow to assess cardiac function in 8-13-day-old chicken embryos using a commercially available high resolution ultrasound system for small animals (Vevo 3100, Fujifilm Visualsonics Inc.) equipped with a high frequency probe (MX700; centre transmit: 50 MHz). We provide detailed standard operating procedures for sample preparation, image acquisition, data analysis, reference values for left and right ventricular function and dimensions, and inter-observer variabilities. Finally, we challenged incubated chicken eggs with two interventions well-known to affect cardiac physiology-metoprolol treatment and hypoxic exposure-to demonstrate the sensitivity of in-ovo echocardiography. In conclusion, in-ovo echocardiography is a feasible alternative tool for basic cardiovascular research, which can easily be implemented into the small animal research environment using existing infrastructure to replace mice and rat experiments, and thus, reduce use of laboratory animals according to the 3R principle.

Comparative assessment of coronary physiology using transthoracic pulsed-wave Doppler and myocardial contrast echocardiography in rats

BACKGROUND

Coronary physiology assessment in rodents by ultrasound is an excellent noninvasive and easy to perform technique, including pulsed-wave Doppler (PWD) and myocardial contrast echocardiography (MCE). Both techniques and the corresponding calculated parameters were investigated in this study at rest as well as their response to pharmacologically induced stress.

METHODS

Left ventricular myocardial function was assessed in eight anaesthetised rats using transthoracic echocardiography. Coronary physiology was assessed by both PWD of the left coronary artery and MCE using a bolus method. Measurements were performed at rest and under stimulation with adenosine and dobutamine. Effects of stimulation on the calculated parameters were evaluated and rated by effect size (η²).

RESULTS

Changes could be demonstrated by selected parameters of PWD and MCE. The clearest effect in PWD was found for diastolic peak velocity (η² = 0.58). It increased from 528 ± 110 mm/s (mean ± standard deviation) at rest to 839 ± 342 mm/s (p = 0.001) with adenosine and 1093 ± 302 mm/s with dobutamine (p = 0.001). The most distinct effect from MCE was found for the normalised wash-in rate (η² = 0.58). It increased from 1.95 ± 0.35% at rest to 3.87 ± 0.85% with adenosine (p = 0.001) and 3.72 ± 1.03% with dobutamine (p = 0.001).

CONCLUSION

Induced changes in coronary physiology by adenosine and dobutamine could successfully be monitored using MCE and PWD in anaesthetised rats. Due to the low invasiveness of the measurements, this protocol could be used for longitudinal animal studies.

Fully Automated Mouse Echocardiography Analysis Using Deep Convolutional Neural Networks

Echocardiography (echo) is a translationally relevant ultrasound imaging modality widely used to assess cardiac structure and function in preclinical models of heart failure (HF) during research and drug development. Though echo is a very valuable tool, the image analysis is a time consuming, resource demanding process, and is susceptible to inter-reader variability. Recent advancements in deep learning have enabled researchers to automate image processing and reduce analysis time and inter-reader variability in the field of medical imaging. In the present study, we developed a fully automated tool - Mouse Echo Neural Net (MENN) - for the analysis of both long axis brightness (B)-mode and short axis motion (M)-mode images of the left ventricle. MENN is a series of fully convolutional neural networks that were trained and validated using manually segmented B-mode and M-mode echo images of the left ventricle. The segmented images were then used to compute cardiac structural and functional metrics. The performance of MENN was further validated in two preclinical models of HF. MENN achieved excellent correlations (Pearson's r = 0.85 to 0.99) and good to excellent agreement between automated and manual analyses. Further inter-reader variability analysis showed that MENN has better agreements with an expert analyst than both a trained analyst and a novice. Notably, the use of MENN reduced manual analysis time by >92%. In conclusion, we developed an automated echocardiography analysis tool that allows for fast and accurate analysis of B-mode and M-mode mouse echo data and mitigates the issue of inter-reader variability in manual analysis.

Effects of irbesartan on myocardial injury in diabetic rats: The role of NLRP3/ASC/Caspase-1 pathway

To observe the mechanism of myocardial injury in diabetic rats after irbesartan intervention and analyze the role of nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammatory pathway. The experiment was divided into four groups: normal control group (CON), high glucose and high caloric diet group (HC), diabetes group (DM) and diabetes+irbesartan group (DM+Ir). Compared with CON group, in HC group, triglyceride, total cholesterol and fasting blood glucose levels were increased; however, there was no significant difference of the cardiac function, the degree of myocardial fibrosis, NLRP3, ASC, Caspase-1 mRNA and protein expressions and the releasing of inflammatory factors interleukin (IL)-1β and IL-18. Compared with HC group, in DM group, triglyceride, total cholesterol, fasting blood glucose, IL-1β and IL-18 levels, NLRP3, ASC, Caspase-1 mRNA and protein expressions and the degree of myocardial fibrosis were increased, but the cardiac function was decreased. Compared with DM group, there were no changes in total cholesterol and fasting blood glucose, the degree of myocardial fibrosis cardiac function was attenuated, NLRP3, ASC, Caspase-1 expressions, IL-1β and IL-18 levels were reduced in DM+Ir group. The results suggested that irbesartan may exert myocardial protection by inhibiting the expression of the NLRP3/ASC/Caspase-1 pathway in diabetic rats.

Changes of Necroptosis in Irbesartan Medicated Cardioprotection in Diabetic Rats

BACKGROUND

Diabetic cardiomyopathy (DCM) is strongly linked to microvascular disease, renin-angiotensin system (RAS) activation, cardiac inflammation and cell apoptosis. Irbesartan is an angiotensin II (Ang II) receptor antagonist in RAS system, which inhibited the conversion of Ang I into Ang II, while the specific mechanism is still obscure.

OBJECTIVE

This study aims to investigate the expressions necroptosis RIP1-RIP3-MLKL pathway in myocardium of diabetic rats, and the protective action of irbesartan on myocardial damage.

MATERIALS AND METHODS

In our study, 30 Sprague-Dawley rats were divided into 5 groups: CON4W, high glucose and high caloric (HC4W), diabetes mellitus 4 weeks (DM4W group), diabetes mellitus 8 weeks (DM8W group), and irbesartan diabetes 8 weeks (Ir DM8W group).

RESULTS

We discovered that as diabetes progresses, the rats gradually lost weight, the HW/BW ratio were increased gradually, and the cardiac function became worse accompanied with the aggravation of inflammatory injury. Meanwhile, the myocardial fibers and cells were disordered, and the expression of positive substances, RIP1 and RIP3 increased significantly. The mRNA and protein levels of myocardial RIP1, RIP3 and MLKL were all increased with the progression of DM. After the intervention of irbesartan in diabetic rats, the cardiac function was improved, whereas inflammatory injury and HW/BW ratio were decreased. Also, the myocardial fibrosis injury was attenuated, and the PAS positive substances, RIP1 and RIP3 were significantly decreased. The curative effect of irbesartan was related to decreased myocardial RIP1, RIP3 and MLKL mRNA and protein levels.

CONCLUSION

In conclusion, irbesartan has a cardioprotective effect on the diabetic rats, and its mechanism may be connected with inhibition of RIP1-RIP3-MLKL pathway.

From bedside to bench: lung ultrasound for the assessment of pulmonary edema in animal models

Traditionally, the lung has been excluded from the ultrasound organ repertoire and, hence, the application of lung ultrasound (LUS) was largely limited to a few enthusiastic clinicians. Yet, in the last decades, the recognition of the previously untapped diagnostic potential of LUS in intensive care medicine has fueled its widespread use as a rapid, non-invasive and radiation-free bedside approach with excellent diagnostic accuracy for many of the most common causes of acute respiratory failure, e.g., cardiogenic pulmonary edema, pneumonia, pleural effusion and pneumothorax. Its increased clinical use has also incited attention for the potential usefulness of LUS in preclinical studies with small animal models mimicking lung congestion and pulmonary edema formation. Application of LUS to small animal models of pulmonary edema may save time, is cost-effective, and may reduce the number of experimental animals due to the possibility of serial evaluations in the same animal as compared with traditional end-point measurements. This review provides an overview of the emerging field of LUS with a specific focus on its application in animal models and highlights future perspectives for LUS in preclinical research.