The current world of medicine is plagued by a lack of hearts. The lack of organs leads to pigs being genetically modified to produce hearts that can be transplanted into humans. However, science is advancing so fast that in a few years, hearts can be made artificially from human stem cells. Researchers working to make artificial hearts have used heart cells to make biohybrid fish. It is an artificial fish made from heart cells. This fish moves like a heart beat.

Biohyroid fish from heart cells swim great

The Harvard University team would like to turn these cells into a functioning artificial heart over time. Such success is still remote and so they use heart cells for various experiments. They made the first biohybrid device that is made of cardiac cells. These cells are derived from human stem cells.


“Our ultimate goal is to build an artificial heart to replace a malformed heart in a child,” said Professor Kit Parker in a statement. “Rather than using heart imaging as a blueprint, we are identifying the key biophysical principles that make the heart work, using them as design criteria, and replicating them in a system, a living, swimming fish, where it is much easier to see if we are successful. ”

Why is this creation called a biohybrid?

Because it combines human cells with non-biological material such as gelatin, paper body and plastic float. No real fish material was used in the production. The scientific team had 73,000 stem cells converted into heart cells. These cells were applied to a zebrafish-shaped structure. Two layers of heart cells were formed on each side of the tail fin. The muscles contained ritinal proteins that are sensitive to different types of light. Thanks to the color change, the individual pages have become out of sync. As one side contracted, the other stretched. The fish began to move and actually swam. It can keep this movement for 108 days when it floats in a saline solution enriched with glucose.


“By leveraging cardiac mechano-electrical signaling between two layers of muscle, we recreated the cycle where each contraction results automatically as a response to the stretching on the opposite side,” said co-first author Dr Keel Yong Lee. The frequency and rhythm of the beat is controlled by a pacing node, giving the team practice in making a pacemaker counterpart.

Heart cells improve on their own

The team has worked in the past on various heart cell projects, such as jellyfish and stingrays. However, previous work has used rat heart cells. Remarkably, the created fish gradually improved in swimming. Regular exercise strengthened the cells and during the first month the fish learned to swim better.

None of this means we are about to see stem-cell hearts pumping blood in living people any time soon, but Parker considers it progress, saying: “I could build a model heart out of Play-Doh, it doesn’t mean I can build a heart. You can grow some random tumor cells in a dish until they curdle into a throbbing lump and call it a cardiac organoid. Neither of those efforts is going to, by design, recapitulate the physics of a system that beats over a billion times during your lifetime while simultaneously rebuilding its cells on the fly. That is the challenge. That is where we go to work. “

The study was published in the Science journal.


Image: Photo credit to Michael Rosnach, Keel Yong Lee, Sung-Jin Park, Kevin Kit Parker