Heart failure is a silent but deadly disease that has steadily increased over the last decade as the
population has gotten older. There has also been an alarming trend of heart failure in the young
population. A pre-clinical model is required to study this disease and find treatments or drugs for it.
We describe the methods for developing a zebrafish model of heart failure, as well as the parameters
for testing it.
Heart failure is characterised by a gradual deterioration of cardiac function, which eventually leads to
erratic heart rhythm, edoema, and death. The majority of heart failures are chronic processes caused
by long-term hypertension or cardiovascular disease. Weakening heart function frequently causes
congestion, or fluid buildup, in the lungs and other tissues by impeding blood flow through the
chambers of the heart. Several physiological systems, including the neurohormone, antidiuresis, and
renin–angiotensin system, are activated as a reflex response to stress to the heart’s normal function to
compensate for insufficient cardiac output.
Zebrafish embryos have demonstrated numerous benefits for human disease research and drug
discovery. Using zebrafish embryos and aristolochic acid, a low-cost model that can be easily
observed and allows for rapid experimental procedures was developed for zebrafish (AA)
Heart failure is distinguished by either impaired pump/systolic function [heart failure with reduced
ejection fraction (HFrEF)] or impaired relaxation/diastolic function [heart failure with preserved
ejection fraction (HFpEF) HFpEF is becoming the most common type of HF, and these patients are
more likely to be elderly women with comorbidities. The aetiology of HFpEF is still unknown, and
there are no drugs that can improve the prognosis. When modelling HF, it is critical to characterise its
sub-type as precisely as possible. Until recently, zebrafish HF models were largely uncharacterized in
terms of diastolic and/or systolic dysfunction. However, with the development and availability of
echocardiography, characterization of the HF subtype in adult zebrafish is becoming more common.
The time has come to establish guidelines for standardised imaging conditions (anaesthesia, water
temperature, etc.) and criteria for characterising cardiac function in zebrafish echocardiography.
Furthermore, embryonic zebrafish HF models are now frequently used to elaborate on the subtype of
HF.Chronic stress causes HF to develop slowly as a result of a cardiac remodelling process. Adult
human cardiomyocytes are terminally differentiated and cannot proliferate in response to stress.
Cardiomyocytes grow in size (cardiac hypertrophy) in order to maintain adequate heart function to
meet the body’s demands. This adaptive hypertrophy eventually becomes maladaptive and leads to HF
via a variety of molecular signalling pathways that are still largely unknown. These pathways are
known to involve cell growth and proliferation, gene expression (including non-coding RNAs),
immune responses, cellular metabolism, mitochondrial function, fibrosis, impaired intracellular
calcium handling, and cell death. Scientists are still debating whether cardiac hypertrophy is
beneficial (adaptive) or harmful (maladaptive). Unlike humans, zebrafish hearts can respond to
cardiac stress by increasing the number of cardiomyocytes (hyperplasia) as well as increasing cell size
(hypertrophy), as demonstrated by high-output cardiac stress caused by anaemia and following
ventricular resection. The counting and sizing of cardiomyocytes in embryonic zebrafish hearts is a
simple process.
Due to various their genotypic and phenotypic similarities, zebrafish are a useful model for studying
CMs and the phenotype/physiology of genetic variants. When its limitations are understood, zebrafish
can be used to model pathological cardiac electrophysiology and congenital heart disease. With each
model, care should be taken to accurately characterise cardiac structure and function, including
quantification of cardiac size while distinguishing between cardiac hypertrophy and hyperplasia. The
fact that zebrafish have small two-chambered hearts with scarce fibrosis, as well as differences in
calcium cycling and ionic currents, which lead to differences in hemodynamic and cardiac
electrophysiology, limit the value of zebrafish HF models for impaired cardiac function and
arrhythmias.The incredible ability of zebrafish to repair and restore cardiac function is the most
intriguing zebrafish HF research avenue.
Heart disease zebrafish models can be created with the following phenotypes: cardiac hypertrophy,
severed cardiac fibres, endocardium loss, and gradual weakening and subsequent cessation of cardiac
contractility within 2 days of treatment. Cardiac phenotypes can appear as early as 48 hpf in the
embryonic stage.
These changes include distortion of the heart shape, decrease of heart size, and gradual decrease of
heart rate. Zebrafish at 48 hpf (hours post fertilisation) is chosen to begin verapamil treatment for the
development of the heart failure model.
Parameters to analyze heart development using quantitative and qualitative assays:
1) Image quantitative analysis.A microscope was used to perform image-based morphometric
analysis.The most common symptoms are heart dilatation and venous congestion.
2) Polymerase Chain Reaction Quantitative
RNA was extracted from 20 embryos from each treatment using Trizol.The MxPro QPCR software
was used to calculate the mRNA quantity of the genes of interest, with the b-actin gene serving as a
normalizer.The experimental groups’ results were then compared to a control group (DMSO or AAtreated embryos).
Conclusion
Zebrafish can be used to perform rapid in vivo screening and efficacy assessments of heart failure
therapeutic drugs.
The zebrafish is emerging as a predictive animal model for assessing drug efficacy, toxicity, and
safety in vivo.
The morphological and molecular bases of tissues and organs in zebrafish are either identical or
similar to those in other vertebrates, including humans