In a small but significant step towards creating an artificial heart, scientists at Harvard and Emory universities have developed a synthetic fish that can keep swimming like a beating heart for more than 100 days — with its tail flipping rhythmically from side to side.
"Our ultimate goal is to build an artificial heart to replace a malformed heart in a child," Harvard University bioengineer Kevin Kit Parker says.
This “biohybrid” fish comprises the heart’s two main attributes — voluntary movement (automaticity) and messaging triggered by mechanical motion (mechanoelectrical signaling). The two sides of its fins are composed of two layers of living heart muscle cells or cardiomyocytes each.
A feedback mechanism is triggered when a side is squeezed tight and the other side is stretched. This kind of physical bending activates the electrical signal that forms ion channels in the muscles, which makes them contract. That, in turn, cause the other side to stretch and triggered the same process, thus making it an ongoing cycle.
"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," Harvard University bioengineer Keel Yong Lee says.
The scientists also added an isolated cluster of cells that works as a pacemaker-like system into the biohybrid fish. "Because of the two internal pacing mechanisms, our fish can live longer, move faster, and swim more efficiently than previous work," explains biophysics researcher Sung-Jin Park, the co-first author of the study.
The key concepts of the heart’s functions were the basis of designing the fish. "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," says Parker.
Image credit: Michael Rosnach, Keel Yong Lee, Sung-Jin Park, Kevin Kit Parker via Harvard School of Engineering and Applied Sciences