Robofish powered by heart cells

Insights into this aren't as fishy as some may think…
21 February 2022

Interview with 

Kit Parker, Harvard University




Studying how the human body works is no mean feat. And trying to figure out how the heart - our automatically-beating, life-dependent organ - functions requires scientists to think outside-of-the-box. Julia spoke to Kit Parker from Harvard University, who is making waves with his novel approach to understand how our heart cells operate…

Julia - Almost every second we're alive, our heart beats. This process is automatic, orchestrated by the cardiac cells which make up our blood pumping organ. Kit studies how these cells work and came up with a somewhat unconventional way of doing so.

Kit - Morphologically, it looks like a fish. Functionally, it looks like a fish. Genetically, it's human.

Julia - He got his inspiration to do this from a trip with his daughter.

Kit - In the New England aquarium of Boston, there is a display of jellyfish. I was watching these things swimming around and I was thinking, "that thing's pumping just like the ventricle in the heart" and said, "I bet I could build that."

Julia - Using heart cells, Kit wanted to see if he could mimic the pumping of these marine organisms to learn about how the heart functions.

Kit - So we built a jellyfish - and that was quite a scene because we took a rat apart and we rebuilt it as a jellyfish. It was alive and swimming around.

Julia - Next up on Kit's list (after another aquarium trip), a stingray.

Kit - I said, "I bet I can build that one too." You know, now my daughter's always teasing me: "Oh you gonna build that Daddy." Whenever I see something cool: "You gonna build that. You think you can build that."

Julia - Why Kit is keen to use heart cells to build constructs in the lab is to improve regenerative medicine: a field which aims to build human hearts and other organs in the lab to give to people who need them. But a lot of focus in this area has been elsewhere.

Kit - Mostly, it boils down to trying to replicate the anatomy, but there's some pretty complex physics there in the heart. We decided to pick a couple principles of cardiac biophysics and build a very simple model: the fish - and we chose the zebra fish.

Julia - Kit and his team made a pacemaker: a bundle of cells like those in our own heart to alter how fast or slow it beats. This pacemaker is called a genode. They then constructed two parallel layers of heart cells derived from human stem cells, embedded in gelatin, with a fin across them to balance, and set them off beating.

Kit - And if you give a little bit of a tickle to the genome, it sends a wave of excitation through the tissue and that's what causes it to contract.

Julia - When the pacemaker kicks in, the heart cells in one layer contract, stretching the other layer over to the side, which then prompts it to contract, creating this swishing back and forth like a fish's tail, which allows it to swim. And they could keep this up for a while.

Kit - They would swim for weeks on end - for about four and a half months they would swim with the same velocity. This is a big advance, Julia, because when you're born, the number of cells you have in your heart, two days after you leave the womb, is the same for the rest of your life unless you have a heart attack and some of them die. Those cells have to rebuild themselves as they grow and as they pump.

Julia - It's thought human heart cells rebuild themselves every 20 days.

Kit - With our fish that were pumping for 180 days, that means they rebuilt themselves five times. That's a big deal.

Julia - Multiple healthy rebuilds while the cells are functioning is a great sign for Kit's overall goal.

Kit - Eventually, what we want to do is build a heart for a child that's born with a malformed heart. Building with biophysics, understanding those design criteria, and the longevity of the tissues that we build, are two big, important steps for us. We think we learned a lot from that.

Julia - But, sadly, the human fish are no more. They were a lot of work for Kit and his team.

Kit - It's like having a child, right? You've got to feed it, change it's diaper every day. It's kind of the same thing with these fish. You've got to come into the lab every day and so after a while you're just like "This thing's never going to stop." People are always disappointed when I tell them. They say, "Well, what are you going to do with the fish now?" I'm like, "Nothing it's over. We're never going to build another one." It was a training exercise to see how good we were at building human cardiac tissue. Before I can build a heart that goes into a sick child (because it's game on when that happens - there's no turning back) I have to continually test myself to see how good of an engineer I am. So, with these marine organisms, by going to more and more complex anatomies, we test ourselves as engineers.

Julia - This is a pretty new field of science.

Kit - It's a cross between marine zoology and robotics. So, maybe 'zoobotics' is the word for it, I don't know.

Julia - By using this technique to build more complex marine creatures, this can hopefully tell us more about how our own hearts work.

Kit - The idea of using robotic design as a scientific instrument, the same way we use a microscope, is a really cool concept to me.


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