Ventricular and pulmonary vascular remodeling induced by pulmonary overflow in a chronic model of pretricuspid shunt

Right versus left ventricular remodeling in heart failure due to chronic volume overload

Mechanisms of right ventricular (RV) dysfunction in heart failure (HF) are poorly understood. RV response to volume overload (VO), a common contributing factor to HF, is rarely studied. The goal was to identify interventricular differences in response to chronic VO. Rats underwent aorto-caval fistula (ACF)/sham operation to induce VO. After 24 weeks, RV and left ventricular (LV) functions, gene expression and proteomics were studied. ACF led to biventricular dilatation, systolic dysfunction and hypertrophy affecting relatively more RV. Increased RV afterload contributed to larger RV stroke work increment compared to LV. Both ACF ventricles displayed upregulation of genes of myocardial stress and metabolism. Most proteins reacted to VO in a similar direction in both ventricles, yet the expression changes were more pronounced in RV (p_slope: < 0.001). The most upregulated were extracellular matrix (POSTN, NRAP, TGM2, CKAP4), cell adhesion (NCAM, NRAP, XIRP2) and cytoskeletal proteins (FHL1, CSRP3) and enzymes of carbohydrate (PKM) or norepinephrine (MAOA) metabolism. Downregulated were MYH6 and FAO enzymes. Therefore, when exposed to identical VO, both ventricles display similar upregulation of stress and metabolic markers. Relatively larger response of ACF RV compared to the LV may be caused by concomitant pulmonary hypertension. No evidence supports RV chamber-specific regulation of protein expression in response to VO.

TMEM16A Regulates Pulmonary Arterial Smooth Muscle Cells Proliferation via p38MAPK/ERK Pathway in High Pulmonary Blood Flow-Induced Pulmonary Arterial Hypertension

OBJECTIVE

Pulmonary arterial hypertension (PAH) is a complex disease of the small pulmonary arteries that is mainly characterized by vascular remodeling. It has been demonstrated that excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs) plays a pivotal role in vascular remodeling during PAH. The present study was undertaken to explore the role of TMEM16A in regulating PASMCs proliferation in high pulmonary blood flow-induced PAH.

METHODS

Aortocaval shunt surgery was undertaken to establish an animal model. Pulmonary artery pressure and pulmonary vascular structure remodeling (PVSR) were tested. Immunohistochemical staining and Western blot were performed to investigate the expression of TMEM16A. The proliferation of PASMCs was tested by the MTT assay. After treating PASMCs with TMEM16A-siRNA, the expression of proliferating cell nuclear antigen (PCNA), phosphorylated p38 mitogen-activated protein kinase (p-p38MAPK), and phosphorylated extracellular signal-regulated kinase (p-ERK) signaling in PASMCs were tested.

RESULTS

PAH and PVSR developed 11 weeks postoperation. Elevated expression of TMEM16A accompanied by high expression of PCNA in pulmonary arteries of the shunt group was observed. The increased proliferation of PASMCs and increased expression of TMEM16A and PCNA, along with activated p-p38MAPK and p-ERK signaling in PASMCs of the shunt group, were all attenuated by siRNA-specific TMEM16A knockdown.

CONCLUSION

TMEM16A regulates PASMCs proliferation in high pulmonary blood flow-induced PAH, and the p38MAPK/ERK signaling pathway is probably involved.

Characteristics of Pulmonary Vascular Remodeling in a Porcine Model of Shunt-Associated Pulmonary Arterial Hypertension

Lung biopsy is the gold standard for evaluating pathological changes in the pulmonary vascular bed. Knowing the distribution characteristics of pulmonary vascular lesions can improve the accuracy of lung biopsy. To investigate the distribution characteristics of pulmonary vascular remodeling, a reliable porcine model of shunt-associated pulmonary arterial hypertension (PAH) was established. Twenty piglets were randomly divided into the experimental group (n = 10) and the control group (n = 10). A modified Blalock-Taussig shunt (MBTS, left innominate artery to main pulmonary artery) was created surgically in the experimental group. Three months later, an invasive catheter was used to obtain hemodynamic parameters, and lung biopsy was performed to assess the remodeling of pulmonary vascular bed. MBTS was successfully implemented in six piglets. There's no significant difference in hemodynamic parameters of the two groups before the shunt. However, these parameters and right ventricular hypertrophy index of the experimental group were significantly increased after three months shunting. Pathological changes in the experimental group, including thickening of pulmonary artery media, intimal fibrosis, and right ventricular hypertrophy, were observed. Furthermore, the percentage of media thickness and medial area of the experimental group were significantly higher than control group. Histopathology showed that vascular remodeling of the lung was inhomogeneous and that the lateral lesion was more severe than other segments. These results indicated that MBTS could be used to establish a reliable porcine model of shunt-associated PAH and that multisite detection with different segments should be applied to assess the severity of pulmonary vascular remodeling.

Surgical and physiological challenges in the development of left and right heart failure in rat models

Rodent surgical animal models of heart failure (HF) are critically important for understanding the proof of principle of the cellular alterations underlying the development of the disease as well as evaluating therapeutics. Robust, reproducible rodent models are a prerequisite to the development of pharmacological and molecular strategies for the treatment of HF in patients. Due to the absence of standardized guidelines regarding surgical technique and clear criteria for HF progression in rats, objectivity is compromised. Scientific publications in rats rarely fully disclose the actual surgical details, and technical and physiological challenges. This lack of reporting is one of the main reasons that the outcomes specified in similar studies are highly variable and associated with unnecessary loss of animals, compromising scientific assessment. This review details rat circulatory and coronary arteries anatomy, the surgical details of rat models that recreate the HF phenotype of myocardial infarction, ischemia/reperfusion, left and right ventricular pressure, and volume overload states, and summarizes the technical and physiological challenges of creating HF. The purpose of this article is to help investigators understand the underlying issues of current HF models in order to reduce variable results and ensure successful, reproducible models of HF.

The Left Pneumonectomy Combined with Monocrotaline or Sugen as a Model of Pulmonary Hypertension in Rats

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats with the additional administration of monocrotaline (MCT) or SU5416 (Sugen). We also compare these two models to other PAH models commonly used in research. In the last few years, the focus of animal PAH models has moved towards studying the mechanism of angioproliferation of plexiform lesions, in which the role of increased pulmonary blood flow is considered as an important trigger in the development of severe pulmonary vascular remodeling. One of the most promising rodent models of increased pulmonary flow is the unilateral left pneumonectomy combined with a "second hit" of MCT or Sugen. The removal of the left lung leads to increased and turbulent pulmonary blood flow and vascular remodeling. Currently, there is no detailed procedure of the pneumonectomy surgery in rats. This article details a step-by-step protocol of the pneumonectomy surgical procedure and post-operative care in male Sprague-Dawley rats. Briefly, the animal is anesthetized and the chest is opened. Once the left pulmonary artery, pulmonary vein, and bronchus are visualized, they are ligated and the left lung is removed. The chest then closed and the animal recovered. Blood is forced to circulate only on the right lung. This increased vascular pressure leads to a progressive remodeling and occlusion of small pulmonary arteries. The second hit of MCT or Sugen is used one week post-surgery to induce endothelial dysfunction. The combination of increased blood flow in the lung and endothelial dysfunction produces severe PAH. The primary limitation of this procedure is that it requires general surgical skills.

A rabbit model of progressive chronic right ventricular pressure overload

OBJECTIVES

Right ventricular (RV) failure from increased pressure loading is a frequent consequence of acquired and congenital heart diseases. However, the mechanisms involved in their pathophysiology are still unclear, and few data exist on RV pressure-loading models and early versus late effects on RV and left ventricular responses. We characterized a rabbit model of chronic RV pressure overload and early-late effects on biventricular function.

METHODS

Twenty-one New Zealand white rabbits were randomized into 3 groups: (i) sham, (ii) pulmonary artery (PA) banding (PAB) for 3 weeks (PAB3W) and (iii) PAB for 6 weeks (PAB6W). Progressive RV pressure overload was created by serial band inflation using an adjustable device. Molecular, echocardiographic and haemodynamic studies were performed.

RESULTS

RV pressure overload was achieved with clinical manifestations of RV failure. Heart and liver weights were significantly higher after PAB. PAB-induced echocardiographic ventricular remodelling increased wall thickness and stress and ventricular dilation. Cardiac output (ml/min) (sham 172.4 ± 42.86 vs PAB3W 103.1 ± 23.14 vs PAB6W 144 ± 60.9, P = 0.0027) and systolic and diastolic functions decreased; with increased RV end-systolic and end-diastolic pressures (mmHg) (sham 1.6 ± 0.66 vs PAB3W 3.9 ± 1.8 vs PAB6W 5.2 ± 2.2, P = 0.0103), despite increased contractility [end-systolic pressure-volume relationship (mmHg/ml), sham 3.76 ± 1.76 vs PAB3W 12.21 ± 3.44 vs PAB6W 19.4 ± 6.88, P < 0.0001]. Functional parameters further worsened after PAB6W versus PAB3W. LV contractility increased in both the PAB groups, despite worsening of other invasive measures of systolic and diastolic functions.

CONCLUSIONS

We describe a novel, unique model of chronic RV pressure overload leading to early biventricular dysfunction and fibrosis with further progression at 6 weeks. These findings can aid in guiding management.

Characteristics of Pulmonary Vascular Remodeling in a Novel Model of Shunt-Associated Pulmonary Arterial Hypertension

BACKGROUND Establishing a shunt-induced pulmonary arterial hypertension (PAH) model in mice would be of great scientific value, but no such models have been reported to date. Here, we established a shunt-associated PAH in mice to investigate the characteristics of pulmonary vascular remodeling, which provides a new platform for the in-depth study of PAH associated with congenital heart disease (CHD). MATERIAL AND METHODS Eighty mice were randomly divided into the heavy shunt group (n=32), the small shunt group (n=32), the sham operation group (n=8), and the control group (n=8). The septum of the abdominal aorta and inferior vena cava was cut directly to create a heavy abdominal aortocaval shunt. Pulmonary artery pressure, right ventricular hypertrophy index, and lung tissue morphology were evaluated in the 4th, 6th, 8th, and 12th weeks in the shunt groups. RESULTS Shunt-associated PAH by abdominal aortocaval shunt in mice was successfully established. The shunt patency rate was significantly higher in the heavy shunt group. Significant differences were observed between the heavy shunt group and other groups in terms of pulmonary artery pressure and the right ventricular hypertrophy index. Tissue sections revealed a thickened pulmonary intimal layer and muscular layer and stenosis of the lumen in the shunt groups. Immunofluorescent assay results showed significant proliferations of PAH smooth muscle cells and endothelial cells, consistent with the clinical pulmonary vascular remodeling seen in human patients with severe PAH. CONCLUSIONS Shunt-associated PAH established by directly cutting the septum between the abdominal aorta and inferior vena cava is a stable and reliable model for research on PAH associated with CHD.

Noninvasive evaluation of left ventricular elastance according to pressure-volume curves modeling in arterial hypertension

End-systolic left ventricular (LV) elastance (E_es) has been previously calculated and validated invasively using LV pressure-volume (P-V) loops. Noninvasive methods have been proposed, but clinical application remains complex. The aims of the present study were to 1) estimate E_es according to modeling of the LV P-V curve during ejection ("ejection P-V curve" method) and validate our method with existing published LV P-V loop data and 2) test the clinical applicability of noninvasively detecting a difference in E_es between normotensive and hypertensive subjects. On the basis of the ejection P-V curve and a linear relationship between elastance and time during ejection, we used a nonlinear least-squares method to fit the pressure waveform. We then computed the slope and intercept of time-varying elastance as well as the volume intercept (V₀). As a validation, 22 P-V loops obtained from previous invasive studies were digitized and analyzed using the ejection P-V curve method. To test clinical applicability, ejection P-V curves were obtained from 33 hypertensive subjects and 32 normotensive subjects with carotid tonometry and real-time three-dimensional echocardiography during the same procedure. A good univariate relationship (r² = 0.92, P < 0.005) and good limits of agreement were found between the invasive calculation of E_es and our new proposed ejection P-V curve method. In hypertensive patients, an increase in arterial elastance (E_a) was compensated by a parallel increase in E_es without change in E_a/E_es In addition, the clinical reproducibility of our method was similar to that of another noninvasive method. In conclusion, E_es and V₀ can be estimated noninvasively from modeling of the P-V curve during ejection. This approach was found to be reproducible and sensitive enough to detect an expected increase in LV contractility in hypertensive patients. Because of its noninvasive nature, this methodology may have clinical implications in various disease states.NEW & NOTEWORTHY The use of real-time three-dimensional echocardiography-derived left ventricular volumes in conjunction with carotid tonometry was found to be reproducible and sensitive enough to detect expected differences in left ventricular elastance in arterial hypertension. Because of its noninvasive nature, this methodology may have clinical implications in various disease states.

Cardiovascular imaging: what have we learned from animal models?

Cardiovascular imaging has become an indispensable tool for patient diagnosis and follow up. Probably the wide clinical applications of imaging are due to the possibility of a detailed and high quality description and quantification of cardiovascular system structure and function. Also phenomena that involve complex physiological mechanisms and biochemical pathways, such as inflammation and ischemia, can be visualized in a non-destructive way. The widespread use and evolution of imaging would not have been possible without animal studies. Animal models have allowed for instance, (i) the technical development of different imaging tools, (ii) to test hypothesis generated from human studies and finally, (iii) to evaluate the translational relevance assessment of in vitro and ex-vivo results. In this review, we will critically describe the contribution of animal models to the use of biomedical imaging in cardiovascular medicine. We will discuss the characteristics of the most frequent models used in/for imaging studies. We will cover the major findings of animal studies focused in the cardiovascular use of the repeatedly used imaging techniques in clinical practice and experimental studies. We will also describe the physiological findings and/or learning processes for imaging applications coming from models of the most common cardiovascular diseases. In these diseases, imaging research using animals has allowed the study of aspects such as: ventricular size, shape, global function, and wall thickening, local myocardial function, myocardial perfusion, metabolism and energetic assessment, infarct quantification, vascular lesion characterization, myocardial fiber structure, and myocardial calcium uptake. Finally we will discuss the limitations and future of imaging research with animal models.