BioEd Online

Kit Parker from Harvard University has made an artificial jellyfish using silicone and muscle cells from a rat’s heart [1]. The synthetic creature, which he calls a medusoid, looks like a flower with eight petals. When placed in an electric field, it pulses and swims exactly like its living counterpart.

“Morphologically, we’ve built a jellyfish. Functionally, we’ve built a jellyfish. Genetically, this thing is a rat,” says Parker.

Parker’s lab works on artificial models of human heart tissues for regenerating organs and testing drugs, and they built the medusoid as a way of understanding the “fundamental laws of muscular pumps”. It is an engineer’s approach to basic science: prove that you identified the right principles by building something with them.

In 2007, Parker was searching for new ways of studying muscular pumps, when he visited Boston’s New England Aquarium. “I saw the jellyfish display and it hit me like a thunderbolt,” he says. “I thought: I know I can build that.” To do so, he recruited John Dabiri, who studies biological propulsion at the California Institute of Technology. “I grabbed him and said, ‘John, I think I can build a jellyfish.’ He didn’t know who I was, but I was pretty excited and waving my arms, and I think he was afraid to say no.”

Janna Nawroth, a graduate student who led the project, began by mapping every cell in the bodies of juvenile moon jellies (Aurelia aurita) to understand how they swim. Their umbrellas consist of a single layer of muscle, with fibres that are tightly aligned around a central ring and along eight spokes.

As the umbrellas beat downwards, electrical signals spread through the muscle in a smooth wave, “like when you drop a pebble in water,” says Parker. “It’s exactly like what you see in the heart. My bet is that to get a muscular pump, the electrical activity has got to spread as a wavefront.”

Nawroth mimicked these properties by growing a single layer of rat heart muscle on a patterned sheet of Polydimethylsiloxane. When an electric field is applied, the muscle rapidly contracts, compressing the medusoid and mimicking the jellyfish’s power stroke. The elastic silicone then pulls the medusoid back to its original flat shape, ready for the next stroke.

When placed between two electrodes, the medusoid swam like the real thing. It even mimicked the feeding currents that jellyfish produce to wash food particles into their mouths. “We thought if we’re really good at this, we’re going to recreate that vortex, and we did,” says Parker. “We took a rat apart and rebuilt it as a jellyfish.”

“I think that this is terrific,” says Joseph Vacanti, a pioneering tissue engineer from Massachusetts General Hospital. “It is a powerful demonstration of engineering chimeric systems of living and non-living components.”

Parker says his team is taking synthetic biology to a new level. “Usually when we talk about synthetic life forms, somebody will take a living cell and put new genes in. We built an animal. It’s not just about genes, but about morphology and function.”

The team now plans on building a medusoid using human heart cells and they have filed a patent to use it, or something similar, as a platform for testing new drugs. “You’ve got a heart drug?” he says. “You let me put it on my jellyfish, and I’ll tell you if it can improve the pumping.”

They are also looking to reverse-engineer other marine life-forms too, says Parker. “We’ve got a whole tank of stuff in there, and an octopus on order.”