SCIENTISTS have made an artificial jellyfish out of rat heart muscles and rubbery silicon. When given an electric shock, it swims just like the real thing. Future versions should be able to swim and feed by themselves. “That then allows us to extend their lifetime,” John Dabiri, a professor of aeronautics and bioengineering at the California Institute of Technology, told me. The breakthrough is a big step toward the development of an artificial human heart with living cells. It also opens a window to a future where humans could loosen the constraints of evolution. “The design of the heart that we have today is by no means the best physically possible design,” Dabiri said. “It is the one that evolution stumbled onto over the course of millions of years of random searching.” It's possible, perhaps probable, that there's a better design out there for humans to discover. An artificial heart, for example, could be engineered to steer clear of heart disease, the leading cause of death in the US. Building a better pump ?To get there, though, scientists must first understand how biology assembles its building blocks into a pump, Dabiri noted. “We know pretty well how to build engineered pumps, things that are built out of steel and aluminum and so on,” he said. “We don't have as good a handle right now in biology on how nature builds things out of muscle tissues.” Researchers from Caltech and Harvard explain how and why they created an artificial jellyfish from rat heart cells and silicone rubber. To start, they looked to the jellyfish, an example of a simple biological pump, and tried to build it in the lab from scratch. Jellyfish essentially have two parts: muscle cells that squeeze down on the body, pushing out water and jetting the animal the opposite way, and elastic stretchy tissue (the jelly) that gently recovers to its relaxed shape after each pump. “In our engineered system, we needed to have these two components,” Dabiri explained. The team could have used jellyfish tissue and jellyfish muscle, but “it so happens that the building blocks we are more familiar with in tissue engineering come from the heart cells of rats,” he said. The technique was pioneered by Kevin Kit Parker, a bioengineer at Harvard and co-author of a paper describing the artificial jellyfish published today in the journal Nature Biotechnology. It allows researchers to take rat heart cells and pattern them in different shapes and sizes that act as actuators – “things that can move, they can pump, they can flap,” Dabiri said. For the jelly part, the team used a thin layer of silicone rubber. Putting together the pieces ?The next step was to put the two pieces together in the best possible way to get a functioning jellyfish. Instead of simply copying nature, the team tried out all kinds of muscle patterns, looking for the best. “As engineers in this process of building artificial jellyfish, we simply don't have the same constraintsthat evolution does,” Dabiri said. “These organisms, as they evolve, have to worry about fending off predators, catching their prey, reproducing. All we have to do is show up in a lab and try to be creative.” “So, it is a very different set of constraints that we have in terms of developing this, and so it is not surprising that we might find solutions that are different from what might have come through evolution.” In the end, the team settled on a muscle arrangement that is similar to that of the jellyfish, but “not a carbon copy,” Dabiri said. — Agencies
