Magnetic resonance imaging in experimental Chagas disease: a brief review of the utility of the method for monitoring right ventricular chamber dilatation

Web-Based Application for Biomedical Image Registry, Analysis, and Translation (BiRAT)

Imaging has become an invaluable tool in preclinical research for its capability to non-invasively detect and monitor disease and assess treatment response. With the increased use of preclinical imaging, large volumes of image data are being generated requiring critical data management tools. Due to proprietary issues and continuous technology development, preclinical images, unlike DICOM-based images, are often stored in an unstructured data file in company-specific proprietary formats. This limits the available DICOM-based image management database to be effectively used for preclinical applications. A centralized image registry and management tool is essential for advances in preclinical imaging research. Specifically, such tools may have a high impact in generating large image datasets for the evolving artificial intelligence applications and performing retrospective analyses of previously acquired images. In this study, a web-based server application is developed to address some of these issues. The application is designed to reflect the actual experimentation workflow maintaining detailed records of both individual images and experimental data relevant to specific studies and/or projects. The application also includes a web-based 3D/4D image viewer to easily and quickly view and evaluate images. This paper briefly describes the initial implementation of the web-based application.

Animal models of Chagas disease and their translational value to drug development

INTRODUCTION

American trypanosomiasis, better known as Chagas disease, is a global public health issue. Current treatments targeting the causative parasite, Trypanosoma cruzi, are limited to two old nitroheterocyclic compounds; new, safer drugs are needed. New tools to identify compounds suitable for parasitological cure in humans have emerged through efforts in drug discovery.

AREAS COVERED

Animal disease models are an integral part of the drug discovery process. There are numerous experimental models of Chagas disease described and in use; rather than going through each of these and their specific features, the authors focus on developments in recent years, in particular the imaging technologies that have dramatically changed the Chagas R&D landscape, and provide a critical view on their value and limitations for moving compounds forward into further development.

EXPERT OPINION

The application of new technological advances to the field of drug development for Chagas disease has led to the implementation of new and robust/standardized in vivo models that contributed to a better understanding of host/parasite interactions. These new models should also build confidence in their translational value for moving compounds forward into clinical development.

Cell therapies for Chagas disease

In this review of cell therapies in Chagas disease, we cover aspects related to the disease, its treatment and world demographics, before proceeding to describe the preclinical and clinical trials performed using cell therapies in the search for an alternative therapy for the most severe and lethal form of this disease, chronic chagasic cardiomyopathy.

Pentoxifylline reverses chronic experimental Chagasic cardiomyopathy in association with repositioning of abnormal CD8+ T-cell response

Background

Chronic chagasic cardiomyopathy (CCC), the main clinical sign of Chagas disease, is associated with systemic CD8⁺ T-cell abnormalities and CD8-enriched myocarditis occurring in an inflammatory milieu. Pentoxifylline (PTX), a phosphodiesterase inhibitor, has immunoregulatory and cardioprotective properties. Here, we tested PTX effects on CD8⁺ T-cell abnormalities and cardiac alterations using a model of experimental Chagas’ heart disease.

Methodology/Principal Findings

C57BL/6 mice chronically infected by the Colombian Trypanosoma cruzi strain and presenting signs of CCC were treated with PTX. The downmodulation of T-cell receptors on CD8⁺ cells induced by T. cruzi infection was rescued by PTX therapy. Also, PTX reduced the frequency of CD8⁺ T-cells expressing activation and migration markers in the spleen and the activation of blood vessel endothelial cells and the intensity of inflammation in the heart tissue. Although preserved interferon-gamma production systemically and in the cardiac tissue, PTX therapy reduced the number of perforin⁺ cells invading this tissue. PTX did not alter parasite load, but hampered the progression of heart injury, improving connexin 43 expression and decreasing fibronectin overdeposition. Further, PTX reversed electrical abnormalities as bradycardia and prolonged PR, QTc and QRS intervals in chronically infected mice. Moreover, PTX therapy improved heart remodeling since reduced left ventricular (LV) hypertrophy and restored the decreased LV ejection fraction.

Conclusions/Significance

PTX therapy ameliorates critical aspects of CCC and repositioned CD8⁺ T-cell response towards homeostasis, reinforcing that immunological abnormalities are crucially linked, as cause or effect, to CCC. Therefore, PTX emerges as a candidate to treat the non-beneficial immune deregulation associated with chronic Chagas' heart disease and to improve prognosis.

Chronic chagasic cardiomyopathy (CCC) is the main clinical manifestation of Chagas disease (CD), a neglected illness caused by the protozoan parasite Trypanosoma cruzi. More than hundred years after its discovery, CD continues to be a public health problem and millions of chronically infected people wait for an effective treatment. Chagasic cardiomyopathy is associated with CD8⁺ T-cell-enriched myocarditis, fibrosis and cardiac electrical and structural abnormalities, frequently progressing to heart failure. Presently, the available therapies only mitigate symptoms of CCC. Abnormalities in CD8⁺ T-cell compartment are present in CCC patients. Recently, we described the importance of CD8⁺ T-cells in the pathogenesis of CCC. Therefore, our proposal was to interfere with abnormalities of CD8⁺ T-cells glimpsing a better prognosis for CCC. Using PTX, an affordable drug with immunomodulatory properties on T-cells and cardioprotective effects in non-infections disease, we bring a therapeutic candidate for treating CCC. PTX therapy downmodulated detrimental CD8⁺ T-cells and promoted T. cruzi-specific interferon-gamma-producing T-cells. Importantly, chronic chagasic electrical and echocardiographic alterations were reversed by PTX therapy. Future studies may test the use of PTX combined with trypanocidal drug or as a vaccine adjuvant to improve the quality of life of chronic CD patients.

Stem Cell-Based Therapies in Chagasic Cardiomyopathy

Chagas disease is caused by Trypanosoma cruzi and can lead to a dilated cardiomyopathy decades after the prime infection by the parasite. As with other dilated cardiomyopathies, conventional pharmacologic therapies are not always effective and as heart failure progresses patients need heart transplantation. Therefore alternative therapies are highly desirable and cell-based therapies have been investigated in preclinical and clinical studies. In this paper we review the main findings of such studies and discuss future directions for stem cell-based therapies in chronic chagasic cardiomyopathy.

Molecular imaging, biodistribution and efficacy of mesenchymal bone marrow cell therapy in a mouse model of Chagas disease

Chagasic cardiomyopathy, resulting from infection with the parasite Trypanosoma cruzi, was discovered more than a century ago and remains an incurable disease. Due to the unique properties of mesenchymal stem cells (MSC) we hypothesized that these cells could have therapeutic potential for chagasic cardiomyopathy. Recently, our group pioneered use of nanoparticle-labeled MSC to correlate migration with its effect in an acute Chagas disease model. We expanded our investigation into a chronic model and performed more comprehensive assays. Infected mice were treated with nanoparticle-labeled MSC and their migration was correlated with alterations in heart morphology, metalloproteinase activity, and expression of several proteins. The vast majority of labeled MSC migrated to liver, lungs and spleen whereas a small number of cells migrated to chagasic hearts. Magnetic resonance imaging demonstrated that MSC therapy reduced heart dilatation. Additionally metalloproteinase activity was higher in heart and other organs of infected mice. Protein expression analyses revealed that connexin 43, laminin γ1, IL-10 and INF-γ were affected by the disease and recovered after cell therapy. Interestingly, MSC therapy led to upregulation of SDF-1 and c-kit in the hearts. The beneficial effect of MSC therapy in Chagas disease is likely due to an indirect action of the cells of the heart, rather than the incorporation of large numbers of stem cells into working myocardium.

Chagas cardiomyopathy and ischemic stroke

American trypanosomiasis, known as Chagas disease is a major cause of cardiomyopathy in South America. Irreversible damage to the heart can appear 10-20 years after chagasic infection. The relationship between Chagas cardiomyopathy and ischemic stroke has been reviewed. Significant variables that predict ischemic stroke in chagasic patients have been identified: apical aneurysm, cardiac insufficiency, electrocardiogram arrhythmia and female gender. Chagasic cardiomyopathy should be included in the differential diagnosis of the etiology of stroke, being a potential source of cardioembolic stroke.

Imaging of small-animal models of infectious diseases

Infectious diseases are the second leading cause of death worldwide. Noninvasive small-animal imaging has become an important research tool for preclinical studies of infectious diseases. Imaging studies permit enhanced information through longitudinal studies of the same animal during the infection. Herein, we briefly review recent studies of animal models of infectious disease that have used imaging modalities.

Chagas heart disease: report on recent developments

Chagas disease, caused by the parasite Trypanosoma cruzi, is an important cause of cardiac disease in endemic areas of Latin America. It is now being diagnosed in nonendemic areas because of immigration. Typical cardiac manifestations of Chagas disease include dilated cardiomyopathy, congestive heart failure, arrhythmias, cardioembolism, and stroke. Clinical and laboratory-based research to define the pathology resulting from T. cruzi infection has shed light on many of the cellular and molecular mechanisms leading to these manifestations. Antiparasitic treatment may not be appropriate for patients with advanced cardiac disease. Clinical management of Chagas heart disease is similar to that used for cardiomyopathies caused by other processes. Cardiac transplantation has been successfully performed in a small number of patients with Chagas heart disease.

Correlation between clinical presentation and delayed-enhancement MRI pattern in myocarditis

PURPOSE

The exact incidence of myocarditis is unknown, as the diagnosis is frequently delayed or missed. Clinical presentation and disease course are extremely variable, as there may be acute onset with acute coronary syndrome, or cardiogenic shock, or progressive heart failure or arrhythmias. The purpose of this study was to identify prognostic factors on magnetic resonance imaging (MRI) performed in patients with bioptically proven myocarditis at presentation and after 6 months.

MATERIALS AND METHODS

Fifty-six consecutive patients with different presentations of myocarditis (20 with acute coronary syndrome, 20 with heart failure, 16 with arrhythmias) were enrolled. All patients underwent B-mode echocardiography (echo) and tissue Doppler imaging, coronarography, ventriculography, endomyocardial biopsy and contrast-enhanced MRI examination, as well as clinical and echo follow-up at 6 months.

RESULTS

At 6-month follow-up, patients were divided in two groups according to values of end-systolic volume and ejection fraction: patients with negative remodelling and those with positive remodelling. Late enhancement was found to be an independent predictor of negative remodelling.

CONCLUSIONS

Contrast-enhanced MRI is useful both in the diagnosis and as a prognostic indicator in the clinical suspicion of myocarditis.

Mesenchymal bone marrow cell therapy in a mouse model of chagas disease. Where do the cells go?

BACKGROUND

Chagas disease, resulting from infection with the parasite Trypanosoma cruzi (T. cruzi), is a major cause of cardiomyopathy in Latin America. Drug therapy for acute and chronic disease is limited. Stem cell therapy with bone marrow mesenchymal cells (MSCs) has emerged as a novel therapeutic option for cell death-related heart diseases, but efficacy of MSC has not been tested in Chagas disease.

METHODS AND RESULTS

We now report the use of cell-tracking strategies with nanoparticle labeled MSC to investigate migration of transplanted MSC in a murine model of Chagas disease, and correlate MSC biodistribution with glucose metabolism and morphology of heart in chagasic mice by small animal positron emission tomography (microPET). Mice were infected intraperitoneally with trypomastigotes of the Brazil strain of T. cruzi and treated by tail vein injection with MSC one month after infection. MSCs were labeled with near infrared fluorescent nanoparticles and tracked by an in vivo imaging system (IVIS). Our IVIS results two days after transplant revealed that a small, but significant, number of cells migrated to chagasic hearts when compared with control animals, whereas the vast majority of labeled MSC migrated to liver, lungs and spleen. Additionally, the microPET technique demonstrated that therapy with MSC reduced right ventricular dilation, a phenotype of the chagasic mouse model.

CONCLUSIONS

We conclude that the beneficial effects of MSC therapy in chagasic mice arise from an indirect action of the cells in the heart rather than a direct action due to incorporation of large numbers of transplanted MSC into working myocardium.

Advances in imaging of animal models of Chagas disease

Since serial studies of patients are limited, researchers interested in Chagas disease have relied on animal models of Trypanosoma cruzi infection to explore many aspects of this important human disease. These studies have been important for evaluation of the immunology, pathology, physiology and other aspects of pathogenesis. While larger animals have been employed, mice have remained the most favoured animal model, as they recapitulate many aspects of the human disease, are easy to manipulate genetically and are amenable to study by small animal imaging technologies. Further, developments in non-invasive imaging technologies have permitted the study of the same animal over an extended period of time by multiple imaging modalities, thus permitting the study of the transition from acute infection through the chronic stage and during therapeutic regimens.

Myocardial involvement in Chagas disease: insights from cardiac magnetic resonance

BACKGROUND

Chagas' disease is becoming a public health problem in Europe because of migratory movements. Cardiac magnetic resonance (CMR) has emerged as a non-invasive tool to assess cardiac tissue characteristics. There is scarce data available on CMR in patients with Chagas' disease.

OBJECTIVE

To describe CMR findings in patients with Chagas' disease living in a non-endemic area focusing on differentiation from other cardiomyopathies and relation with clinical status.

METHODS AND RESULTS

Sixty-seven Chagas' disease patients divided into 3 groups-group 1 (indeterminate form: positive serology without ECG or 2D-echocardiographic abnormalities; N = 27), group 2 (ECG abnormalities of Chagas' disease but normal 2D-echocardiography; N = 19), and group 3 (regional wall motion abnormalities, LV end-diastolic diameter >55 mm or LV ejection fraction <50% on echocardiography; N = 21)--were studied. The presence of wall motion abnormalities and delayed enhancement (DE) by CMR was more frequent in the inferolateral and apical segments. DE distribution in the myocardial wall was heterogeneous (subendocardial 26.8%, midwall 14.0%, subepicardial 22.6%, and transmural 36.0% of total segments with DE) and related to larger cardiac chambers and worse systolic function.

CONCLUSION

Pattern of DE in Chagas' disease may mimic that of both ischemic and nonischemic cardiomyopathies, with especial predilection for the apical and inferolateral segments of the left ventricle. These findings support that myocardial involvement in chronic Chagas' cardiomyopathy (CCC) may be due to both microvascular disturbances and chronic myocarditis and may favor CCC in the differential diagnosis of patients with compatible epidemiological history and heart failure of uncertain etiology.

The benefits of using selenium in the treatment of Chagas disease: prevention of right ventricle chamber dilatation and reversion of Trypanosoma cruzi-induced acute and chronic cardiomyopathy in mice

Cardiac damage is a frequent manifestation of Chagas disease, which is caused by the parasite Trypanosoma cruzi. Selenium (Se) is an essential micronutrient, the deficiency of which has been implicated in the development of cardiomyopathy. Our group has previously demonstrated that Se supplementation prevents myocardial damage during acute T. cruzi infection in mice. In this study, we analyzed the effect of Se treatment in cases of T. cruzi infection using prevention and reversion schemes. In the Se prevention scheme, mice were given Se supplements (2 ppm) starting two weeks prior to inoculation with T. cruzi(Brazil strain) and continuing until 120 days post-infection (dpi). In the Se reversion scheme, mice were treated with Se (4 ppm) for 100 days, starting at 160 dpi. Dilatation of the right ventricle was observed in the infected control group at both phases of T. cruzi infection, but it was not observed in the infected group that received Se treatment. Surviving infected mice that were submitted to the Se reversion scheme presented normal P wave values and reduced inflammation of the pericardium. These data indicate that Se treatment prevents right ventricular chamber increase and thus can be proposed as an adjuvant therapy for cardiac alterations already established by T. cruzi infection.

Would selenium supplementation aid in therapy for Chagas disease?

Chagas disease, a neglected tropical disease discovered over 100 years ago, is caused by the intracellular parasite Trypanosoma cruzi and is most frequently associated with chronic cardiomyopathy and digestive disorders. Initial invasion of cells is followed by progressive inflammatory destruction of heart, muscles, nerves, and gastrointestinal (GI) tract tissue. Approximately 30% of patients progress to a chronic cardiomyopathy associated with increased morbidity and mortality. Seven to 10% of patients develop megasyndromes involving the GI tract, in particular, the esophagus and the colon. Results from several studies suggest that selenium (Se) deficiency could be an important factor in the pathogenesis of Chagas disease. In this opinion article, Se supplementation is proposed as an adjuvant therapy for treatment of chronic Chagas disease.

Mitochondrial complex III defects contribute to inefficient respiration and ATP synthesis in the myocardium of Trypanosoma cruzi-infected mice

In this study, we conducted a thorough analysis of mitochondrial bioenergetic function as well as the biochemical and molecular factors that are deregulated and contribute to compromised adenosine triphosphate (ATP) production in the myocardium during Trypanosoma cruzi infection. We show that ADP-stimulated state 3 respiration and ATP synthesis supported by pyruvate/malate (provides electrons to complex I) and succinate (provides electrons to complex II) substrates were significantly decreased in left ventricular tissue and isolated cardiac mitochondria of infected mice. The decreased mitochondrial ATP synthesis in infected murine hearts was not a result of uncoupling between the electron-transport chain and oxidative phosphorylation and decreased availability of the intermediary metabolites (e.g., NADH). The observed decline in the activities of complex-I, -IV, and -V was not physiologically relevant and did not contribute to compromised respiration and ATP synthesis in infected myocardium. Instead, complex III activity was decreased above the threshold level and contributed to respiratory-chain inefficiency and the resulting decline in mitochondrial ATP synthesis in infected myocardium. The loss in complex III activity occurred as a consequence of cytochrome b depletion. Treatment of infected mice with phenyl-alpha-tert-butyl nitrone (PBN, antioxidant) was beneficial in preserving the mtDNA-encoded cytochrome b expression, and subsequently resulted in improved complex III activity, mitochondrial respiration, and ATP production in infected myocardium. Overall, we provide novel data on the mechanism(s) involved in cardiac bioenergetic inefficiency during T. cruzi infection.

Micro-positron emission tomography in the evaluation of Trypanosoma cruzi-induced heart disease: Comparison with other modalities

Noninvasive assessment of cardiac structure and function is essential to understand the natural course of murine infection with Trypanosoma cruzi. Magnetic resonance imaging (MRI) and echocardiography have been used to monitor anatomy and function; positron emission tomography (PET) is ideal for monitoring metabolic events in the myocardium. Mice infected with T. cruzi (Brazil strain) were imaged 15-100 days post infection (dpi). Quantitative (18)F-FDG microPET imaging, MRI and echocardiography were performed and compared. Tracer ((18)F-FDG) uptake was significantly higher in infected mice at all days of infection, from 15 to 100 dpi. Dilatation of the right ventricular chamber was observed by MRI from 30 to 100 dpi in infected mice. Echocardiography revealed significantly reduced ejection fraction by 60 dpi. Combination of these three complementary imaging modalities makes it possible to noninvasively quantify cardiovascular function, morphology, and metabolism from the earliest days of infection through the chronic phase.

Bone marrow cell therapy ameliorates and reverses chagasic cardiomyopathy in a mouse model

Chronic chagasic cardiomyopathy, which is caused by the protozoan Trypanosoma cruzi, is a major cause of heart failure in Latin America. It is a disease for which effective treatment in its advanced clinical forms is lacking. We have previously shown that bone marrow mononuclear cell (BMC) transplantation is effective in reducing inflammation and fibrosis in the mouse model of Chagas disease. The present study used magnetic resonance imaging to assess changes in the cardiac morphology of infected mice after therapy with BMCs. Serial imaging of the BMC-treated mice revealed regression of the right ventricular dilatation typically observed in the chagasic mouse model.