In their quest to build a beating heart from scratch, Harvard University researchers looked to the sea for inspiration, building a tiny swimming “jellyfish” out of rat heart cells and a thin, jellyfish-shaped polymer film.
The real jellyfish, a simple aquatic creature buffeted by ocean currents, may seem a world away from the human heart, but researchers found that the repetitive pulsations jellyfish use to swim through salt water are similar to the way the heart pumps blood through the human body.
“I do a lot of cardiac research, and . . . I started looking at marine life forms, [thinking] maybe we don’t understand the fundamental laws of muscular pumps,” said Kevin Kit Parker, a professor of bioengineering and applied physics at Harvard who was one of the project’s leaders.
Parker had become frustrated with the lack of new drugs for various heart problems and began to wonder if one of the bottlenecks could be incomplete understanding of how the heart really works.
Then, on a visit to the New England Aquarium, Parker realized that marine organisms — and particularly jellyfish — resembled the heart in key ways and offered a simple model that could be studied. “I look at these jellyfish and I’m thinking, I could build that — and they pump,” Parker said.
He quickly enlisted a collaborator with expertise in biological propulsion systems and a special interest in jellyfish: John Dabiri from the California Institute of Technology.
In their new work, published Sunday in the journal Nature Biotechnology, the team reports on the steps it took to build a “pseudo-organism" called the Medusoid.
They started with the real thing, examining the biomechanics of jellyfish propulsion in the laboratory, running computer simulations and conducting experiments. They repurposed forensic software typically used to analyze fingerprints, in order to study the protein networks in the cells of jellyfish. They used a thin film of silicon polymer with eight lobes, seeded with rat heart cells that responded to electrical stimulation in water.
The engineered organism, they found, could swim just like a real jellyfish.
Dabiri, a professor of aeronautics and bioengineering at Caltech, said the parallels between jellyfish propulsion and the heart went deep. To propel themselves, he said, they create currents of water called “vortex rings” that are much like the smoke rings someone might blow when smoking a cigar. As the heart pumps blood, he said, those same types of rings are generated.
The techniques the team developed will extend beyond the quixotic task of building a simple marine creature from scratch, Parker said, because the work lays the foundation of a new approach that could enable scientists to design and build complicated organisms and organs.
“You don’t start building a bedroom set when you start woodworking; you build a little thing to hold books on your desk,” Parker said, explaining that he and his team will attempt to mimic and understand more complicated creatures and organs.
Many efforts to bioengineer tissues depend largely on cells to naturally assemble into the correct configuration and then function. But the Harvard team approached the problem like engineers who wanted to design a helicopter or an airplane.
Dabiri said they simply focused on understanding the structure, function, and locomotion of the jellyfish.
“We really needed to understand why the animals had muscles arranged the way they did,” he said.
Dr. Harald Ott, an instructor in surgery at Massachusetts General Hospital, said the study was inspiring because it showed that figuring out precisely how an organism works and carefully mimicking it can produce results.
“What it really shows is if we want to engineer a muscle pump, we have to understand the physiology of the muscle pump we’re trying to mimic,” Ott said.
Yiannis N. Kaznessis, a professor of chemical engineering and materials science at the University of Minnesota, cautioned that knowledge of living organisms is not detailed enough to guide bioengineering at the same level of detail as other engineering disciplines. But he said the combination of experimentation and models used in the new work indicate one way to make progress.
“Mathematical models can help us gain this knowledge step by step and assist in proto-engineering attempts,” Kaznessis wrote in an e-mail. “These models can help us pose better questions and narrow the possible answers.”
By extending such precise engineering approaches to other muscular pumps, Parker hopes to hone his team’s ability to engineer more complicated organisms — and eventually organs. Parker said his laboratory is interested in stingrays and is already making room for its newest arrival, an octopus.