Large animal model of chronic pulmonary hypertension

Animals in Respiratory Research

The respiratory barrier, a thin epithelial barrier that separates the interior of the human body from the environment, is easily damaged by toxicants, and chronic respiratory diseases are common. It also allows the permeation of drugs for topical treatment. Animal experimentation is used to train medical technicians, evaluate toxicants, and develop inhaled formulations. Species differences in the architecture of the respiratory tract explain why some species are better at predicting human toxicity than others. Some species are useful as disease models. This review describes the anatomical differences between the human and mammalian lungs and lists the characteristics of currently used mammalian models for the most relevant chronic respiratory diseases (asthma, chronic obstructive pulmonary disease, cystic fibrosis, pulmonary hypertension, pulmonary fibrosis, and tuberculosis). The generation of animal models is not easy because they do not develop these diseases spontaneously. Mouse models are common, but other species are more appropriate for some diseases. Zebrafish and fruit flies can help study immunological aspects. It is expected that combinations of in silico, in vitro, and in vivo (mammalian and invertebrate) models will be used in the future for drug development.

A Dynamic Sheep Model to Induce Pulmonary Hypertension and Right Ventricular Failure

Decompensated right ventricular failure (RVF) in pulmonary hypertension (PH) is fatal, with limited medical treatment options. Developing and testing novel therapeutics for PH requires a clinically relevant large animal model of increased pulmonary vascular resistance and RVF. This manuscript describes the method to induce an ovine PH-RVF model that utilizes left pulmonary artery (LPA) ligation, progressive main pulmonary artery (MPA) banding, and insertion of an RV pressure line for monitoring. The PA cuff and RV pressure tubing are connected to subcutaneous access ports. This model of PH-RVF is a versatile platform to control not only the disease severity, but also the RV's phenotypic response. Subjects undergo progressive PA band adjustments twice per week for approximately 9 weeks with sequential measures of RV pressure, PA cuff pressures, and mixed venous blood gas (SvO2). Subjects can further be exercised on a livestock treadmill while hemodynamic parameters are captured. At the initiation and endpoint of this model, ventricular function and dimensions are assessed using echocardiography. In this model, RV mean and systolic pressure increased to 28 ± 5 and 57 ± 7 mmHg at week 1, and further to 44 ± 7 and 93 ± 18 mmHg by week 9, respectively. Echocardiography demonstrates characteristic findings of PH-RVF, notably RV dilation, increased wall thickness, and septal bowing. The rate of PA banding has a significant impact on SvO2 and thus the model can be titrated to elicit varying RV phenotypes. When the PA cuff is tightened rapidly, it can lead to a precipitous decline in SvO2, leading to RV decompensation, whereas a slower, more paced strategy leads to an adaptive RV stress-load response that maintains physiologic SvO2. A faster rate of PA banding will also lead to more severe liver fibrosis. The addition of controlled exercise provides a useful platform for assessing the effects of physical exertion in a PH-RVF model. This chronic PH-RVF model provides a valuable tool for studying molecular mechanisms, developing diagnostic biomarkers, and evaluating mechanical circulatory support systems.

Progression Toward Decompensated Right Ventricular Failure in the Ovine Pulmonary Hypertension Model

Decompensated right ventricular failure (RVF) in patients with pulmonary hypertension (PH) is fatal, with limited treatment options. Novel mechanical circulatory support systems have therapeutic potential for RVF, but the development of these devices requires a large animal disease model that replicates the pathophysiology observed in humans. We previously reported an effective disease model of PH in sheep through ligation of the left pulmonary artery (PA) and progressive occlusion of the main PA. Herein, we report a case of acute decompensation with this model of chronic RVF. Gradual PA banding raised the RV pressure (maximum RV systolic/mean pressure = 95 mmHg/56 mmHg). Clinical findings and laboratory serum parameters suggested appropriate physiologic compensation for 7 weeks. However, mixed venous saturation declined precipitously on week 7, and creatinine increased markedly on week 9. By the 10th week, the animal developed dependent, subcutaneous edema. Subsequently, the animal expired during the induction of general anesthesia. Post-mortem evaluation revealed several liters of pleural effusion and ascites, RV dilatation, eccentric RV hypertrophy, and myocardial fibrosis. The presented case supports this model's relevance to the human pathophysiology of RVF secondary to PH and its value in the development of novel devices, therapeutics, and interventions.

Animal models of pulmonary hypertension: Getting to the heart of the problem

Despite recent therapeutic advances, pulmonary hypertension (PH) remains a fatal disease due to the development of right ventricular (RV) failure. At present, no treatments targeted at the right ventricle are available, and RV function is not widely considered in the preclinical assessment of new therapeutics. Several small animal models are used in the study of PH, including the classic models of exposure to either hypoxia or monocrotaline, newer combinational and genetic models, and pulmonary artery banding, a surgical model of pure RV pressure overload. These models reproduce selected features of the structural remodelling and functional decline seen in patients and have provided valuable insight into the pathophysiology of RV failure. However, significant reversal of remodelling and improvement in RV function remains a therapeutic obstacle. Emerging animal models will provide a deeper understanding of the mechanisms governing the transition from adaptive remodelling to a failing right ventricle, aiding the hunt for druggable molecular targets.

Left Pulmonary Artery Ligation and Chronic Pulmonary Artery Banding Model for Inducing Right Ventricular-Pulmonary Hypertension in Sheep

Pulmonary hypertension (PH) is a progressive disease that leads to cardiopulmonary dysfunction and right heart failure from pressure and volume overloading of the right ventricle (RV). Mechanical cardiopulmonary support has theoretical promise as a bridge to organ transplant or destination therapy for these patients. Solving the challenges of mechanical cardiopulmonary support for PH and RV failure requires its testing in a physiologically relevant animal model. Previous PH models in large animals have used pulmonary bead embolization, which elicits unpredictable inflammatory responses and has a high mortality rate. We describe a step-by-step guide for inducing pulmonary hypertension and right ventricular hypertrophy (PH-RVH) in sheep by left pulmonary artery (LPA) ligation combined with progressive main pulmonary artery (MPA) banding. This approach provides a controlled method to regulate RV afterload as tolerated by the animal to achieve PH-RVH, while reducing acute mortality. This animal model can facilitate evaluation of mechanical support devices for PH and RV failure.

Establishment of adult right ventricle failure in ovine using a graded, animal-specific pulmonary artery constriction model

BACKGROUND

Right ventricle failure (RVF) is associated with serious cardiac and pulmonary diseases that contribute significantly to the morbidity and mortality of patients. Currently, the mechanisms of RVF are not fully understood and it is partly due to the lack of large animal models in adult RVF. In this study, we aim to establish a model of RVF in adult ovine and examine the structure and function relations in the RV.

METHODS

RV pressure overload was induced in adult male sheep by revised pulmonary artery constriction (PAC). Briefly, an adjustable hydraulic occluder was placed around the main pulmonary artery trunk. Then, repeated saline injection was performed at weeks 0, 1, and 4, where the amount of saline was determined in an animal-specific manner. Healthy, age-matched male sheep were used as additional controls. Echocardiography was performed bi-weekly and on week 11 post-PAC, hemodynamic and biological measurements were obtained.

RESULTS

This PAC methodology resulted in a marked increase in RV systolic pressure and decreases in stroke volume and tricuspid annular plane systolic excursion, indicating signs of RVF. Significant increases in RV chamber size, wall thickness, and Fulton's index were observed. Cardiomyocyte hypertrophy and collagen accumulation (particularly type III collagen) were evident, and these structural changes were correlated with RV dysfunction.

CONCLUSION

In summary, the animal-specific, repeated PAC provided a robust approach to induce adult RVF, and this ovine model will offer a useful tool to study the progression and treatment of adult RVF that is translatable to human diseases.

The role of inflammation in a rat model of chronic thromboembolic pulmonary hypertension induced by carrageenan

Background

Chronic thromboembolic pulmonary hypertension (CTEPH) is a life-threatening condition arising from the thrombus and obstructive remodeling of the pulmonary arteries, which causes a significant morbidity and mortality. Although the modern treatment in CTEPH has been significant advanced both in surgical and medical treatment, none can claim to cure the disease, largely because of our limited understanding of the underlying pathogenesis of the disease and lack of a reliable CTEPH animal model to study for. Recently, inflammation has been accepted as a common pathway through which various risk factors trigger venous thrombo-embolism (VTE) formation, we describe a novel mouse model of CTEPH which reproduces a frequent trigger and resembles the time course, histological features, and clinical presentation of CTEPH in humans, to open a new horizons of inflammation in CTEPH.

Methods

By administering a pulmonary embolism (PE) protocol (comprising 3 sequential left jugular vein injections of autologous blood clots) to 8-week-old male Sprague Dawley (SD) rats using tranexamic acid (200 mg/kg^.d) to inhibit fibrinolysis and injecting additional carrageenan (20 mg/kg, once a week) to create perivascular inflammation, we successfully generated a CTEPH animal model. By monitoring the mean pulmonary artery pressure (mPAP) and the histopathological change to evaluate the CTEPH model. By detecting the RT-PCR, western blot, TUNEL, and immunohistochemistry in the sub-groups to find the potential mechanism of inflammation may work in the pulmonary vascular remolding.

Results

In this study, rats with CTEPH exhibited pronounced pulmonary vascular remolding with higher vessel wall area/total area (WA/TA) ratio in comparison to the control rats (85.41%±7.37% vs. 76.41%±5.97%, P<0.05), the mPAP (25.51±1.13 vs. 15.92±1.13 mmHg, P<0.05). Significant differences in mean pulmonary artery pressure (mPAP) values were observed between rats injected solely with clots and those injected with both clots and carrageenan (25.51±1.13 vs. 29.82±1.26 mmHg, P<0.05, respectively). Furthermore, following the third embolization, thrombi and intimal hyperplasia occurred in the pulmonary artery. In addition, repeated embolization elevated mRNA and protein levels of tumor necrosis factor-α (TNF-α), NF-κB/p65, and B-cell lymphoma-2 (BCL-2), but decreased BAX expression in a time-dependent manner.

Conclusions

Take advantage of the inflammation to trigger VTE formation, we successfully generated a CTEPH animal model. Inflammation may play a crucial role in the pathogenesis and progression of CTEPH by inhibiting endothelial cell apoptosis. Understanding the role of inflammation in CTEPH may not only help to determine the optimal treatment options but also may aid in the development of future preventative strategies, since current anticoagulation treatment regimens are not designed to inhibit inflammation.

Expression of tissue factor and forkhead box transcription factor O-1 in a rat model for chronic thromboembolic pulmonary hypertension

Few reports have examined tissue factor (TF) and forkhead box transcription factor O-1 (FoxO1) expression in chronic thromboembolic pulmonary hypertension (CTEPH) animal models. To investigate the role of TF and FoxO1 and their interactions during CTEPH pathogenesis in a rat model. Autologous blood clots were repeatedly injected into the pulmonary arteries through right jugular vein to induce a rat model of CTEPH. Hemodynamic parameters, histopathology, and TF and FoxO1expression levels were detected. The mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance and vessel wall area/total area (WA/TA) ratio in the experiment group increased significantly than sham group (P < 0.05). The cardiac output in the 1-, 2-, and 4-week groups decreased significantly (P < 0.05) when compared to sham group. TF mRNA expression levels in the experiment group increased significantly than sham group (P < 0.05). FoxO1 mRNA and protein expression levels were lower in the experiment group than sham group (P < 0.05). The mPAP had a positive correlation with WA/TA ratio (r = 0.45, P = 0.01). TF mRNA expression had a positive correlation with WA/TA ratio (r = 0.374, P = 0.035) and a positive correlation with mPAP (r = 0.48, P= 0.005). FoxO1 mRNA expression had a negative correlation trend with the WA/TA ratio (r = -0.297, P = 0.099) and a negative correlation trend with mPAP (r = -0.34, P = 0.057). TF mRNA expression had a negative correlation with FoxO1 mRNA expression (r = -0.62, P < 0.001). A rat model of CTEPH can be successfully established by the injection of autologous blood clots into the pulmonary artery. TF and FoxO1 may play a key role in vascular remodeling during CTEPH pathogenesis.

Challenges in the development of chronic pulmonary hypertension models in large animals

Pulmonary hypertension (PH) results in significant morbidity and mortality. Chronic PH animal models may advance the study of PH's mechanisms, evolution, and therapy. In this report, we describe the challenges and successes in developing three models of chronic PH in large animals: two models (one canine and one swine) utilized repeated infusions of ceramic microspheres into the pulmonary vascular bed, and the third model employed a surgical aorto-pulmonary shunt. In the canine model, seven dogs underwent microsphere infusions that resulted in progressive elevation of pulmonary arterial pressure over a few months. In this model, pulmonary endoarterial tissue was obtained for histology. In the aorto-pulmonary shunt swine model, 17 pigs developed systemic level pulmonary pressures after 2-3 months. In this model, pulmonary endoarterial tissue was sequentially obtained to assess for changes in gene and microRNA expression. In the swine microsphere infusion model, three pigs developed only a modest chronic increase in pulmonary arterial pressure, despite repeated infusions of microspheres (up to 40 in one animal). The main purpose of this model was for vasodilator testing, which was performed successfully immediately after acute microsphere infusions. Chronic PH in large animal models can be successfully created; however, a model's characteristics need to match the investigational goals.

Development of a Model of Pediatric Lung Failure Pathophysiology

A pediatric artificial lung (PAL) is under development as a bridge to transplantation or lung remodeling for children with end-stage lung failure (ESLF). To evaluate the efficiency of a PAL, a disease model mimicking the physiologic derangements of pediatric ESLF is needed. Our previous right pulmonary artery (rPA) ligation model (rPA-LM) achieved that goal, but caused immediate mortality in nearly half of the animals. In this study, we evaluated a new technique of gradual postoperative right pulmonary artery occlusion using a Rummel tourniquet (rPA-RT) in seven (25-40 kg) sheep. This technique created a stable model of ESLF pathophysiology, characterized by high alveolar dead space (58.0% ± 3.8%), pulmonary hypertension (38.4 ± 2.2 mm Hg), tachypnea (79 ± 20 breaths per minute), and intermittent supplemental oxygen requirement. This improvement to our technique provides the necessary physiologic derangements for testing a PAL, whereas avoiding the problem of high immediate perioperative mortality.

The role of tissue factor and autophagy in pulmonary vascular remodeling in a rat model for chronic thromboembolic pulmonary hypertension

Background

Few reports have examined tissue factor (TF) and autophagy expression in chronic pulmonary thromboembolic hypertension (CTEPH) animal models. Objectives: To investigate the role of tissue factor (TF), autophagy and their interactions during chronic thromboembolic pulmonary hypertension (CTEPH) pathogenesis in a rat model.

Methods

Autologous blood clots were repeatedly injected into the left jugular vein of rats with injecting endogenous fibrinolysis inhibitor tranexamic acid (TXA). Mean pulmonary arterial pressure (mPAP), histopathology and TF, Beclin-1 and microtubule-associated protein 1 light chain (LC3) expression levels were detected.

Results

The mPAP and vessel wall area/total area (WA/TA) ratio in the experiment group increased significantly (P < 0.05). TF mRNA and protein expression levels in the experiment group increased significantly (P < 0.05). Beclin-1 and LC3B mRNA and protein expression levels were lower in the experiment group (P < 0.05). The mPAP had a positive correlation with WA/TA ratio (r = 0.955, P < 0.05). Beclin-1 and LC3B protein expression had a negative correlation with the WA/TA ratio (r = -0.963, P < 0.05, r = -0.965, P < 0.05, respectively). TF protein expression had a negative correlation with both Beclin-1 and LC3B protein expression (r = -0.995, P <0.05, r = -0972, P < 0.05, respectively).

Conclusions

A rat model of CTEPH can be established by repeatedly introducing autologous blood clots into the pulmonary artery with injecting TXA. TF and autophagy may play a key role during CTEPH pathogenesis, especially in vascular remodeling.

Development and Characterization of an Inducible Rat Model of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is an entity of PH that not only limits patients quality of life but also causes significant morbidity and mortality. The treatment of choice is pulmonary endarterectomy. However numerous patients do not qualify for pulmonary endarterectomy or present with residual vasculopathy post pulmonary endarterectomy and require specific vasodilator treatment. Currently, there is no available specific small animal model of CTEPH that could serve as tool to identify targetable molecular pathways and to test new treatment options. Thus, we generated and standardized a rat model that not only resembles functional and histological features of CTEPH but also emulates thrombi fibrosis. The pulmonary embolism protocol consisted of 3 sequential tail vein injections of fibrinogen/collagen-covered polystyrene microspheres combined with thrombin and administered to 10-week-old male Wistar rats. After the third embolism, rats developed characteristic features of CTEPH including elevated right ventricular systolic pressure, right ventricular cardiomyocyte hypertrophy, pulmonary artery remodeling, increased serum brain natriuretic peptide levels, thrombi fibrosis, and formation of pulmonary cellular-fibrotic lesions. The current animal model seems suitable for detailed study of CTEPH pathophysiology and permits preclinical testing of new pharmacological therapies against CTEPH.

Combination proximal pulmonary artery coiling and distal embolization induces chronic elevations in pulmonary artery pressure in Swine

Pulmonary hypertension (PH) is associated with aberrant vascular remodeling and right ventricular (RV) dysfunction that contribute to early mortality. Large animal models that recapitulate human PH are essential for mechanistic studies and evaluating novel therapies; however, these models are not readily accessible to the field owing to the need for advanced surgical techniques or hypoxia. In this study, we present a novel swine model that develops cardiopulmonary hemodynamics and structural changes characteristic of chronic PH. This percutaneous model was created in swine (n=6) by combining distal embolization of dextran beads with selective coiling of the lobar pulmonary arteries (2 procedures per lung over 4 weeks). As controls, findings from this model were compared with those from a standard weekly distal embolization model (n=6) and sham animals (n=4). Survival with the combined embolization model was 100%. At 8 weeks after the index procedure, combined embolization procedure animals had increased mean pulmonary artery pressure (mPA) and pulmonary vascular resistance (PVR) compared to the controls with no effect on left heart or systemic pressures. RV remodeling and RV dysfunction were also present with a decrease in the RV ejection fraction, increase in the myocardial performance index, impaired longitudinal function, as well as cardiomyocyte hypertrophy, and interstitial fibrosis, which were not present in the controls. Pulmonary vascular remodeling occurred in both embolization models, although only the combination embolization model had a decrease in pulmonary capacitance. Taken together, these cardiopulmonary hemodynamic and structural findings identify the novel combination embolization swine model as a valuable tool for future studies of chronic PH.

Piglet model of chronic pulmonary hypertension

None of the animal models have been able to reproduce all aspects of CTEPH because of the rapid resolution of the thrombi in the pulmonary vasculature. The aim of this study was to develop an easily reproducible large-animal model of chronic pulmonary hypertension (PH) related to the development of a postobstructive and overflow vasculopathy. Chronic PH was induced in 5 piglets by ligation of the left pulmonary artery (PA) through a midline sternotomy followed by weekly transcatheter embolization of the right lower-lobe arteries. Sham-operated piglets (n = 5) served as controls. Hemodynamics, RV function, lung morphometry, and endothelin-1 (ET-1) pathway gene expression (ET-1 and its receptors ETA and ETB) were assessed after 5 weeks in the obstructed (left lung and right lower lobe) and unobstructed (right upper lobe) territories. All animals developed chronic PH within 5 weeks. Compared to controls, chronic-PH animals had higher mean PA pressure (28.5 ± 1.7 vs. 11.6 ± 1.8 mmHg, P = 0.0001) and total pulmonary resistance (784 ± 160 vs. 378 ± 51 dyn s(-1) cm(-5), P = 0.05). Echocardiography showed RV enlargement, RV wall thickening (56 ± 5 vs. 30 ± 4 mm, P = 0.0003), decreased tricuspid annular plane systolic excursion (11.3 ± 0.9 vs. 14.4 ± 0.4 mm, P = 0.01), and paradoxical septal motion. In obstructed territories, morphometry demonstrated increases in the number of bronchial arteries per bronchus (8.7 ± 0.9 vs. 2 ± 0.17, P < 0.0001) and in distal PA media thickness (60% ± 2.8% vs. 29% ± 0.9%, P < 0.0001), consistent with postobstructive vasculopathy. Distal PA media thickness was increased in unobstructed territories (70% ± 2.4% vs. 29% ± 0.9%, P < 0.0001). ET-1 was overexpressed in unobstructed territories, compared to controls and obstructed territories. In conclusion, the large-animal model described here is reproducible and led to the development of PH in a relatively short time frame.

Remodeling of mechanical junctions and of microtubule-associated proteins accompany cardiac connexin43 lateralization

BACKGROUND

Desmosomes and adherens junctions provide mechanical continuity between cardiac cells, whereas gap junctions allow for cell-cell electrical/metabolic coupling. These structures reside at the cardiac intercalated disc (ID). Also at the ID is the voltage-gated sodium channel (VGSC) complex. Functional interactions between desmosomes, gap junctions, and VGSC have been demonstrated. Separate studies show, under various conditions, reduced presence of gap junctions at the ID and redistribution of connexin43 (Cx43) to plaques oriented parallel to fiber direction (gap junction "lateralization").

OBJECTIVE

To determine the mechanisms of Cx43 lateralization, and the fate of desmosomal and sodium channel molecules in the setting of Cx43 remodeling.

METHODS

Adult sheep were subjected to right ventricular pressure overload (pulmonary hypertension). Tissue was analyzed by quantitative confocal microscopy and by transmission electron microscopy. Ionic currents were measured using conventional patch clamp.

RESULT

Quantitative confocal microscopy demonstrated lateralization of immunoreactive junctional molecules. Desmosomes and gap junctions in lateral membranes were demonstrable by electron microscopy. Cx43/desmosomal remodeling was accompanied by lateralization of 2 microtubule-associated proteins relevant for Cx43 trafficking: EB1 and kinesin protein Kif5b. In contrast, molecules of the VGSC failed to reorganize in plaques discernable by confocal microscopy. Patch-clamp studies demonstrated change in amplitude and kinetics of sodium current and a small reduction in electrical coupling between cells.

CONCLUSIONS

Cx43 lateralization is part of a complex remodeling that includes mechanical and gap junctions but may exclude components of the VGSC. We speculate that lateralization results from redirectionality of microtubule-mediated forward trafficking. Remodeling of junctional complexes may preserve electrical synchrony under conditions that disrupt ID integrity.

A pulmonary hypertension model induced by continuous pulmonary air embolization

BACKGROUND

Our goal was to create a clinically relevant large animal model of pulmonary hypertension to serve as a platform allowing preclinical risk/benefit assessment of innovative therapies including artificial lung prototypes.

METHODS

Small amounts of filtered air were continuously infused into the pulmonary circulation of sheep (n = 4) for 8 wk. Hemodynamics and blood gases were measured daily. After termination of air embolization, the sheep were observed for 1 additional wk to assess the constancy of the pulmonary artery pressure changes. At the end of wk 9, all sheep were sacrificed and necropsy was performed.

RESULTS

All animals survived the study and developed pulmonary hypertension by wk 5. Mean pulmonary artery pressures were elevated from 14 ± 1 at baseline to 35 ± 1 mmHg at wk 8 (P < 0.01) and remained unchanged throughout wk 9. A similar increase in pulmonary vascular resistance was observed. Systemic arterial pressure and PaO(2) dropped slightly compared with baselines but remained in safe ranges. Histologic evidence of severe pulmonary arterial remodeling and significant right ventricle hypertrophy was observed.

CONCLUSIONS

We conclude that our 8-wk model of continuous air embolization produces reliable, chronic pulmonary hypertension in sheep with sustained hemodynamic changes, significant pulmonary vascular remodeling, and right ventricle hypertrophy.

Ovine models for chronic heart failure

PURPOSE

Testing and optimizing of surgical therapies for chronic heart failure (CHF) requires large animal models. CHF has been induced in several large animal species. Sheep have modest body mass increase and demonstrate docile behavior and are therefore a preferred species in research on surgical therapies for CHF METHODS: A literature search for existing ovine CHF models was performed, using search terms "sheep" and "heart failure". Relevant secondary references were traced.

RESULTS

Rapid ventricular pacing produces rapid-onset CHFE Its severity ranges from moderate left ventricular failure to severe biventricular failure, depending on length and frequency of pacing. Its counterpart in human CHF is tachycardia-induced HF since it is reversible upon cessation of pacing. Myocardial damage models include CHF induced by cardiototoxic drugs and ischemia. Ischemia-based models include coronary microembolization, occlusion and ischemia/reperfusion models. The microembolization model is relevant to diabetic cardiomyopathy. Coronary occlusion models exhibit variable functional impairment, some with aneurysm formation, and some with mitral valve regurgitation, depending on occlusion localization. They are relevant to CHF following non-reperfused myocardial infarction. Coronary occlusion/reperfusion models are relevant to the occurrence of human ãã despite coronary artery recanalization. Pressure overload of left and right ventricle is induced by aortic and pulmonary artery banding, respectively. Hypertrophy precedes CHF as in patients with valve stenosis and hypertension. Volume overload is induced by valve damage or shunt creation. Atrioventricular valve regurgitation is the most important clinical counterpart.

CONCLUSION

Several ovine CHF models exist. Since they exhibit important cardiac pathology differences, the choice of model should be based on the specific experimental question.

A low mortality model of chronic pulmonary hypertension in sheep

BACKGROUND

Pulmonary hypertension and right ventricular failure are major contributors to morbidity and mortality in chronic lung disease. Therefore, large animal models of pulmonary hypertension and right ventricular hypertrophy are needed to study underlying disease mechanisms and test new treatment modalities. The objective of this study was to create a low-mortality model of chronic pulmonary hypertension and right ventricular hypertrophy in sheep.

METHODS

The vena cavae of nine sheep weighing 62 ± 2 (SEM) kg were injected with 0.375 g of dextran beads (sephadex) every day for 60 d. Pulmonary hemodynamics were assessed via pulmonary artery catheterization prior to the first injection and again on d 14, 28, 35, 42, 49, and 56. At the end of the experiment, the heart was removed, dissected, and weighed to determine the ratio of right ventricular mass to left ventricle plus septal mass (RV:LV+S).

RESULTS

All sheep survived to 60 d. The average pulmonary artery pressure rose from 17 ± 1 mmHg at baseline to 35 ± 3 mmHg on d 56 with no significant change in cardiac output (8.7 ± 0.7 to 9.8 ± 0.7 L/min, P = 0.89). The RV:LV+S was significantly higher (0.42 ± 0.01, P < 0.001) than a historic group of untreated normal animals (0.35 ± 0.01, n = 13).

CONCLUSION

This study provides a low-mortality large animal model of moderate chronic pulmonary hypertension and right ventricular hypertrophy.

Uso crônico de decanoato de nandrolona como fator de risco para hipertensão arterial pulmonar em ratos Wistar

INTRODUÇÃO: O uso indiscriminado de esteróides anabolizantes sintéticos, análogos à testosterona, implica aumento do risco cardiovascular e hipertrofia cardíaca. Assim, o aumento da massa ventricular direita corrigido pelo peso corporal (i.é., hipertrofia ventricular direita - HVD), poderia elevar o risco para o desenvolvimento de hipertensão arterial pulmonar (HAP). OBJETIVOS: Examinar os efeitos do tratamento em longo prazo com decanoato de nadrolona na HVD e sua relação com a HAP em ratos. MÉTODOS: 16 ratos Wistar com três meses de idade foram aleatoriamente divididos em dois grupos: 1) controle-sham (CONT, n = 8); 2) tratados com decanoato de nandrolona (DECA, n = 8). O tratamento consistiu na aplicação intramuscular de Deca-durabolin® 6.0mg.kg-1 de peso corporal durante quatro semanas. Após tratamento, os animais foram anestesiados com hidrato de cloral (4.0mL.kg-1, i.p.), submetidos à cateterização da artéria femoral para registro da pressão arterial media (PAM) e frequência cardíaca (FC). O coração, os rins e o fígado foram retirados, pesados e avaliados os índices de hipertrofia, os quais foram calculados pela razão da massa do órgão pelo peso corporal (mg.g-1). RESULTADOS: Os animais tratados com DECA apresentaram aumento (p < 0,01) do peso corporal (338 ± 6g) vs. CONT (315 ± 5g). Não houve alterações da PAM, embora houvesse (p < 0,01) bradicardia nos animais tratados com DECA (321 ± 13bpm) vs. CONT (368 ± 11bpm). Verificou-se significativa (p < 0,01) hipertrofia dos ventrículos e rins, mas não no fígado. A correlação entre a HVD e PAM no grupo DECA apresentou coeficiente de Pearson positivo e maior (r² = 0,4013) quando comparado com o controle (r² = 0,0003). CONCLUSÕES: Esses dados demonstram que o uso em longo prazo de decanoato de nandrolona induz importante bradicardia e HVD, o que sugere aumento do risco para HAP.

Right ventricular heart failure from pulmonary embolism: key distinctions from chronic pulmonary hypertension

BACKGROUND

The right ventricle normally operates as a low pressure, high-flow pump connected to a high-capacitance pulmonary vascular circuit. Morbidity and mortality in humans with pulmonary hypertension (PH) from any cause is increased in the presence of right ventricular (RV) dysfunction, but the differences in pathology of RV dysfunction in chronic versus acute occlusive PH are not widely recognized.

METHODS AND RESULTS

Chronic PH that develops over weeks to months leads to RV concentric hypertrophy without inflammation that may progress slowly to RV failure. In contrast, pulmonary embolism (PE) results in an abrupt vascular occlusion leading to increased pulmonary artery pressure within minutes to hours that causes immediate deformation of the RV. RV injury is secondary to mechanical stretch, shear force, and ischemia that together provoke a cytokine and chemokine-mediated inflammatory phenotype that amplifies injury.

CONCLUSIONS

This review will briefly describe causes of pulmonary embolism and chronic PH, models of experimental study, and pulmonary vascular changes, and will focus on mechanisms of right ventricular dysfunction, contrasting mechanisms of RV adaptation and injury in these 2 settings.