Paolo Rossi Castelli 10 March 2022 17 min read

A 'bio-hybrid' fish helps study the heart

Research from Harvard University. The little artificial fish contains two layers of human heart cells, which contract to create a sophisticated model of how the heart also moves.

An artificial fish to study the heart and its diseases and, in the future, to replace a damaged heart, especially when the disease appears at birth or in the early years of life and could affecting development. This is what the prototype created by cardiologists and bioengineers at Harvard University (USA), who have been working on the subject for years, promises to do. These researchers have now published the latest surprising results of their work in the journal Science.

As shown in a video, the fish is made of special plastic and metal, but the area near its tail is also covered with two layers of heart muscle cells derived from human stem cells.

When one of the layers contracts, the other relaxes. This relaxation, in turn, opens ion channels - microscopic holes in the cell surface - which increase the concentration of proteins that cause a new contraction. The system therefore allows this very special 'fish' to gently alternate between contraction and relaxation, just like a beating heart. The device also contains a small pacemaker to regulate the frequency and intensity of the heartbeat. The result is a kind of miniature heart that swims thanks to its beats.

The movements of the bio-hybrid fish (as it is called) improve over time, because the stem cells age and function better and better with mechanical stimulation. This fish is also very robust: it continued to swim for a hundred days during tests.

Improving old models
The prototype, inspired by the movements and features of real fish, is an innovation compared to past prototypes developed by the same group. In 2012, Harvard researchers created a kind of transparent bio-hybrid jellyfish containing heart muscle cells from rats that could contract, and in 2016 they built another fish (a stingray), also with rat heart muscle cells.

But a fish with human cells, almost as if bioengineering were imitating natural evolution, is a real step forward, as it is much closer to the real movements of the heart than previous devices.

Studying arrhythmia
So how could the fish be used in the future? While the model is being perfected, the one already available may allow certain heart conditions, like arrhythmia, to be studied closely. However, in the future a device of this kind could become a real artificial heart: something that researchers have been trying to achieve for years, but which has not yet been satisfactorily accomplished with the tools available up to now.

"Most of the studies to create an artificial heart in the past concentrated on reproducing anatomical features, or a simple heartbeat, in engineered tissues,” explains Kit Parker, professor of Bioengineering at Harvard University and coordinator of the Science journal study.

“Now, however, we no longer use cardiac imaging as a model, but we are trying to identify the key biophysical principles that make the heart function, use them as criteria for design and then reproduce them in a system: a swimming fish, where it is much easier to see if we will be successful.”

Ph. Credit: Keel Yong Lee, PhD, Postdoctoral fellow, Disease Biophysics Group, Harvard University (via Twitter)


Paolo Rossi Castelli

Journalist since 1983, Paolo has been dealing with scientific divulgation for years, especially in the fields of medicine and biology. He is the creator of Sportello Cancro, the site created by on oncology in collaboration with the Umberto Veronesi Foundation. He collaborated with the pages of the Science of Corriere della Sera for several years. He is the founder and director of PRC-Comunicare la scienza.