Application of an automated analysis framework for pulsed-wave Doppler cardiac ultrasound measurements to generate reference data in adult zebrafish.

High-frequency cardiac ultrasound is the only well-established method to characterize in vivo cardiovascular function in adult zebrafish noninvasively. Pulsed-wave Doppler imaging allows measurements of blood flow velocities at well-defined anatomical positions, but the measurements and results obtained using this technique need to be analyzed carefully, taking into account the substantial baseline variability within one recording and the possibility for operator bias. To address these issues and to increase throughput by limiting hands-on analysis time, we have developed a fully automated processing pipeline. This framework enables the fast, unbiased analysis of all cardiac cycles in a zebrafish pulsed-wave Doppler recording of both atrioventricular valve flow as well as aortic valve flow without operator-dependent inputs. Applying this automated pipeline to a large number of recordings from wild-type zebrafish shows a strong agreement between the automated results and manual annotations performed by an experienced operator. The reference data obtained from this analysis showed that the early wave peak during ventricular inflow is lower for female compared with male zebrafish. We also found that the peaks of the ventricular inflow and outflow waves as well as the peaks of the regurgitation waves are all correlated positively with body surface area. In general, the presented reference data, as well as the automated Doppler measurement processing tools developed and validated in this study will facilitate future (high-throughput) cardiovascular phenotyping studies in adult zebrafish ultimately leading to a more comprehensive understanding of human (genetic) cardiovascular diseases.

Unraveling the role of TGFß signaling in thoracic aortic aneurysm and dissection using Fbn1 mutant mouse models.

Although abnormal TGFß signaling is observed in several heritable forms of thoracic aortic aneurysms and dissections including Marfan syndrome, its precise role in aortic disease progression is still disputed. Using a mouse genetic approach and quantitative isobaric labeling proteomics, we sought to elucidate the role of TGFß signaling in three Fbn1 mutant mouse models representing a range of aortic disease from microdissection (without aneurysm) to aneurysm (without rupture) to aneurysm and rupture. Results indicated that reduced TGFß signaling and increased mast cell proteases were associated with microdissection. In contrast, increased abundance of extracellular matrix proteins, which could be reporters for positive TGFß signaling, were associated with aneurysm. Marked reductions in collagens and fibrillins, and increased TGFß signaling, were associated with aortic rupture. Our data indicate that TGFß signaling performs context-dependent roles in the pathogenesis of thoracic aortic disease.

Fluid-Structure Interaction Modeling of the Aortic Hemodynamics in Adult Zebrafish: A Pilot Study Based on Synchrotron X-Ray Tomography.

OBJECTIVE: The zebrafish is increasingly used as a small animal model for cardiovascular disease, including vascular disorders. Nevertheless, a comprehensive biomechanical understanding of the zebrafish cardiovascular circulation is still lacking and possibilities for phenotyping the zebrafish heart and vasculature at adult - no longer optically transparent - stages are limited. To improve these aspects, we developed imaging-based 3D models of the cardiovascular system of wild-type adult zebrafish. METHODS: In vivo high-frequency echocardiography and ex vivo synchrotron X-ray tomography were combined to build fluid-structure interaction finite element models of the fluid dynamics and biomechanics inside the ventral aorta. RESULTS: We successfully generated a reference model of the circulation in adult zebrafish. The dorsal side of the most proximal branching region was found as the location of highest first principal wall stress and was also a location of low wall shear stress. Reynolds number and oscillatory shear were very low compared to mice and humans. SIGNIFICANCE: The presented wild-type results provide a first extensive biomechanical reference for adult zebrafish. This framework can be used for advanced cardiovascular phenotyping of adult genetically engineered zebrafish models of cardiovascular disease, showing disruptions of the normal mechano-biology and homeostasis. By providing reference values for key biomechanical stimuli (including wall shear stress and first principal stress) in wild-type animals, and a pipeline for image-based animal-specific computational biomechanical models, this study contributes to a more comprehensive understanding of the role of altered biomechanics and hemodynamics in heritable cardiovascular pathologies.

An Overview of Investigational and Experimental Drug Treatment Strategies for Marfan Syndrome.

Marfan syndrome (MFS) is a heritable connective tissue disorder caused by pathogenic variants in the gene coding for the extracellular matrix protein fibrillin-1. While the disease affects multiple organ systems, the most life-threatening manifestations are aortic aneurysms leading to dissection and rupture. Other cardiovascular complications, including mitral valve prolapse, primary cardiomyopathy, and arrhythmia, also occur more frequently in patients with MFS. The standard medical care relies on cardiovascular imaging at regular intervals, along with pharmacological treatment with ß-adrenergic receptor blockers aimed at reducing the aortic growth rate. When aortic dilatation reaches a threshold associated with increased risk of dissection, prophylactic surgical aortic replacement is performed. Although current clinical management has significantly improved the life expectancy of patients with MFS, no cure is available and fatal complications still occur, underscoring the need for new treatment options. In recent years, preclinical studies have identified a number of potentially promising therapeutic targets. Nevertheless, the translation of these results into clinical practice has remained challenging. In this review, we present an overview of the currently available knowledge regarding the underlying pathophysiological processes associated with MFS cardiovascular pathology. We then summarize the treatment options that have been developed based on this knowledge and are currently in different stages of preclinical or clinical development, provide a critical review of the limitations of current studies and highlight potential opportunities for future research.

Trypanosoma brucei brucei causes a rapid and persistent influx of neutrophils in the spleen of infected mice.

Trypanosomosis is a chronic parasitic infection, affecting both humans and livestock. A common hallmark of experimental murine infections is the occurrence of inflammation and the associated remodelling of the spleen compartment. The latter involves the depletion of several lymphocyte populations, the induction of T-cell-mediated immune suppression, and the activation of monocyte/macrophage cell populations. Here, we show that in experimental T b brucei infections in mice, these changes are accompanied by the alteration of the spleen neutrophil compartment. Indeed, mature neutrophils are rapidly recruited to the spleen, and cell numbers remain elevated during the entire infection. Following the second peak of parasitemia, the neutrophil cell influx coincides with the rapid reduction of splenic marginal zone (MZ)B and follicular (Fo)B cells, as well as CD8+ T and NK1.1+ cells, the latter encompassing both natural killer (NK) and natural killer T (NKT) cells. This report is the first to show a comprehensive overview of all alterations in spleen cell populations, measured with short intervals throughout the entire course of an experimental T b brucei infection. These data provide new insights into the dynamic interlinked changes in spleen cell numbers associated with trypanosomosis-associated immunopathology.

Salivarian Trypanosomosis: A Review of Parasites Involved, Their Global Distribution and Their Interaction With the Innate and Adaptive Mammalian Host Immune System.

Salivarian trypanosomes are single cell extracellular parasites that cause infections in a wide range of hosts. Most pathogenic infections worldwide are caused by one of four major species of trypanosomes including (i) Trypanosoma brucei and the human infective subspecies T. b. gambiense and T. b. rhodesiense, (ii) Trypanosoma evansi and T. equiperdum, (iii) Trypanosoma congolense and (iv) Trypanosoma vivax. Infections with these parasites are marked by excessive immune dysfunction and immunopathology, both related to prolonged inflammatory host immune responses. Here we review the classification and global distribution of these parasites, highlight the adaptation of human infective trypanosomes that allow them to survive innate defense molecules unique to man, gorilla, and baboon serum and refer to the discovery of sexual reproduction of trypanosomes in the tsetse vector. With respect to the immunology of mammalian host-parasite interactions, the review highlights recent findings with respect to the B cell destruction capacity of trypanosomes and the role of T cells in the governance of infection control. Understanding infection-associated dysfunction and regulation of both these immune compartments is crucial to explain the continued failures of anti-trypanosome vaccine developments as well as the lack of any field-applicable vaccine based anti-trypanosomosis intervention strategy. Finally, the link between infection-associated inflammation and trypanosomosis induced anemia is covered in the context of both livestock and human infections.