Zebrafish. 2016 Dec;13(6):477-480. DOI: 10.1089/zeb.2016.1274

Use of Coronary Ultrasound Imaging to Evaluate Ventricular Function in Adult Zebrafish.

Ernens I1,+, Lumley AI1, Devaux Y1, Wagner DR1,2.

1 Cardiovascular Research Unit, Luxembourg Institute of Health , Strassen, Luxembourg.

2 Division of Cardiology, Centre Hospitalier de Luxembourg , Luxembourg, Luxembourg.

+ Correspondence : isabelle.ernens@lih.lu

 

Abstract

So far, imaging of the adult zebrafish heart and assessment of heart failure in adult zebrafish have been very limited. Here, we describe a new method for in vivo imaging of the hypertrabeculated heart of the adult zebrafish using miniaturized cardiac ultrasound catheters obtained from the cardiac catheterization laboratory. This method allows the observation of the ventricle of zebrafish and the assessment of ventricular diameters during diastole and systole, as well as heart rate and fractional shortening. Significant changes in these parameters were detected through the use of an adult zebrafish heart failure model induced by chronic anemia. This imaging technique opens the door to detailed in vivo analysis of the adult heart failure phenotype in zebrafish.

Keywords

adult zebrafish; cardiac function; heart failure; miniaturized ultrasound system

PMID: 27326768

 

Supplement

The zebrafish is an animal model more and more popular to investigate heart development and cardiovascular disease[1]. Indeed, zebrafish embryos grow outside of the mother and are transparent which eases the imaging of the heart. Until now, embryos have been largely used to study heart development, congenital heart disease and for drug screening. In addition, zebrafish are easily genetically modifiable and are thus an incredible tool to study gene implication in cardiovascular development and disease[2, 3].

 

Having said this, many human cardiovascular diseases occur during adulthood when the optical clarity of the zebrafish is lost. The small size of the heart (around 1mm in diameter) and the opacity of the adult fish challenge the assessment of cardiac function in adult fish and thus have limited the use of adult zebrafish to investigate cardiovascular disease.

 

In this publication, we have tested whether a miniaturized ultrasound catheter used for coronary artery imaging of human subjects could be used to non-invasively visualize the ventricle of adult zebrafish. The ultrasound microprobe is easy to manipulate and can be placed accurately on the beating area of an anesthesized fish thorax (Fig 1A). The modulation of the brightness of the spots represented on the screen of the echograph is recorded during 30 seconds.

 

On an image, the bright signal intensity allows to easily locate the ventricular wall (Fig 1B: B-Mode) while no clear signal can be obtained for the 2 other parts of the heart: the atrium and the bulbus atrium. Thus, a scan line is drawn from the external part of the ventricle wall to the external part of the opposite side of the ventricle wall to obtain the motion of the ventricle overtime (Fig 1C: M-Mode). On the M-Mode, the movement of the ventricle wall allows to assess heart rate and the dilated (DD) and contracted (CD) diameters of the ventricle wall (Fig 1D). The fractional shortening can be calculated from these two diameters using the formula: [(DD-CD)/DD]x100 [4].

 

This protocol has been used to assess cardiac function of healthy adult zebrafish and zebrafish with heart failure generated by chronic anemia. Significant differences were detected using this coronary ultrasound imaging system such as an enlargement of the ventricle diameter (+27 %), a decrease in heart rate (-11%) and in fractional shortening (-24%) in the heart failure model.

 

These results indicate that this miniaturized ultrasound catheter is well-adapted to rapidly, conveniently and non-invasively image the ventricle of the adult zebrafish heart. Furthermore, it is suitable to detect ventricular parameter changes especially in longitudinal studies. Thus, a new technique for non-invasive imaging of the ventricle of adult zebrafish is now available for research labs. This will foster research projects dedicated to study cardiac disease in zebrafish.

 

 

Figure 1. Non-invasive imaging of the ventricle of adult zebrafish using a miniaturized ultrasound catheter (A) Positioning of the microprobe on the thorax of the fish kept in a damp sponge. (B) Representative picture of a B-Mode ultrasound image showing the ventricle wall and the scan line to obtain the M-Mode. (C) Representative picture of the time motion on the M-Mode. (D) Zoom on the M-Mode to determine the dilated (DD) and contracted diameters (CD) of the ventricle to calculate the fractional shortening.

 

References

1. Poon, K.L. and T. Brand, The zebrafish model system in cardiovascular research: A tiny fish with mighty prospects. Glob Cardiol Sci Pract, 2013(1): p. 9-28.
2. Dahme, T., H.A. Katus, and W. Rottbauer, Fishing for the genetic basis of cardiovascular disease. Dis Model Mech, 2009. 2(1-2): p. 18-22.
3. Huang, C.C., et al., Zebrafish heart failure models for the evaluation of chemical probes and drugs. Assay Drug Dev Technol, 2013. 11(9-10): p. 561-72.
4. Shin, J.T., et al., High-resolution cardiovascular function confirms functional orthology of myocardial contractility pathways in zebrafish. Physiol Genomics, 2010. 42(2): p. 300-9.