In vivo, high-throughput imaging for functional characterization of the embryonic zebrafish heart

High-throughput imaging allows characterizing the phenotype of large populations of cells, organs or organisms. Studying the function of organs in similar ways remains a challenge. Here, we present a semi-automatic, in vivo, high-throughput imaging and analysis method to characterize cardiac function in the embryonic heart of developing zebrafish larvae subjected to an increase of breeding temperature. We sequentially acquire high-speed movies of the beating heart by automatically visiting embryos arranged in a matrix of wells placed on a motorized microscope stage. We then estimate the radial heart-wall contraction velocity over time for each fish at various temperature settings. Next, we synchronize these signals to obtain an average velocity signature that characterizes heart function at each temperature. We observe a 47 ± 5% increase in the heart rate as the breeding temperature increases from 28°C to 38.1°C (n = 10), accompanied by a change of the contraction pattern that is consistent within the population. Specifically, we quantified intra-population variabilities of the velocity amplitude signal (18%-30%) and the heartbeat length (4%-8%). We expect our approach to be highly relevant for early identification of functional abnormalities during heart development, screening fish carrying genetic defects, or for quantitatively evaluating the effect of pharmacological agents.