Science writer Mary Roach is fascinated by the human body, especially, she says, the "gooey bits and pieces of us that are performing miracles on a daily basis."
Take the human heart, for instance. If we're lucky, Roach says, our hearts might continue beating for 80+ years. "What thing that you buy at Best Buy keeps going that long?" she asks.
Roach is known for her books about what makes the human body so remarkable. She's done deep dives on human cadavers, the digestive system and the science of sex. Now, in Replaceable You: Adventures in Human Anatomy, she chronicles both the history of body part replacement (including prosthetic noses that date back to the 1500s), as well as more recent medical breakthroughs.
The book was inspired by a woman Roach knows with spina bifida, whose gait was impeded by a twisted foot. The woman was seeking to have her foot surgically amputated and replaced with a prosthetic limb, when she encountered an unexpected impediment: Surgeons were reluctant to remove what they considered a healthy limb — even though the patient could not walk on it.
"And I thought that was interesting, the reluctance of the surgeons to remove a foot because it is an act with some finality to remove a foot," Roach says.
Roach's book describes how advancements in gene editing and 3D printing technology might further make our anatomy "replaceable." She profiles scientists in lab at Carnegie Mellon University who used a 3D printer to create a tiny ventricle, which was used to pump the heart of a mouse. But, she adds, the Trump administration's cuts to medical research threaten to interrupt the "pipeline of innovation and discovery."
"That's going to have terrible effects further down the line," Roach says. "Just looking forward to the future of innovation and medical care, it's very depressing."
Interview highlights
On why pigs became the animal used in organ transplants
You can, to a certain extent, blame Hormel, the pork company. What happened in the '40s, '50s, '60s, there was a project, it was a collaboration between the Mayo Clinic, the Mayo Foundation, which was the research arm of the Mayo clinic, and the Hormel Institute, which was the research arm of pork. The goal here was to create a smaller pig, a pig that would be a good match in terms of not just the size of human organs, but the functions. There were all these studies were done looking at do pigs get coronary artery disease? And it turns out they do. In fact, the pig was described in one of their papers as a caricature of an obese human. In other words, gets heart disease, has heart issues, doesn't get enough exercise. …
If you are going to use the pig as your model, as your stand-in for a human, then you want to be sure that these organs ... behave similarly, that they have a similar size. So this research, once it got rolling, and there were dozens and dozens of papers, three volumes of papers looking at kidney function, liver function. There was one on orthodontia where they had put braces onto pigs. So it was all toward the goal of creating an analog, a stand-in for a human being for trying out surgical techniques or not so much pharmaceuticals, but techniques and replacements. So the pig became the go-to creature. … I mean who knows, a goat might've been equally useful, but nobody started using goats.
On preventing the body from rejecting a pig organ
With an organ that's coming from another species, the reaction is quite severe. It's called a hyperacute rejection, where, within minutes, the body starts to attack, the organ starts to turn black. You don't want to put a pig organ into somebody without it having been genetically edited. So one of the things that's edited is something called the alpha-gal protein. And this is a surface protein that the body, if you can knock that out, you're basically just making the pig organ seem a little less pig-like and a little more human-like. So now you're dealing with a level of rejection that you would get with a human transplant. In other words, taking some other human's organ and transplanting it. So the person is still on an immunosuppressive regimen, taking drugs to suppress the immune system. But on about the same level as they would with a human.
On if a pig transplant is kosher
I asked the surgeon who was involved in the first pig transplant … and he said, yeah, there are a lot of folks both in the Jewish religion and the Muslim religion who really wish we'd chosen a different species, because I had been asking him, why pigs? And he says, I get that question all the time. The thing is, he said, we're not eating them, we are saving lives. So it's OK to get a pig organ if you're keeping kosher. ... There were interviews with various religious thought leaders and there was consensus that it is indeed OK to have a pig organ implanted. Just don't eat it.
On experiments 3D printing muscle and tissue
I spent a day at the Feinberg lab at Carnegie Mellon in Pittsburgh, and what people were working on there was trying to print muscle in a way that the alignment of the cells would create muscle that had the specific function that muscle needed. In other words, a heart, the heart needs to move in a kind of a twisting motion. It twists as it pumps, so you've got to print the cells. They have to be in a helix shape, which is different from, say, the hamstring, where it'd be kind of parallel. Or the shoulder muscle, they're in a fan-like shape, which gives you a lot of the versatility of the movement of the shoulder. So you're not just printing generic muscle. You have to print it in a very specific way to achieve the function that you want it to be doing, which I found kind of amazing. No one is printing whole organs. That's way off in the future.
On the tediousness of tissue recovery for organ donations
When I arrived in the room where they were doing the tissue recovery, where they would be extracting the bone and the tendon and the skin, etc., one of the people doing it said to me, this is the worst part of the job. And I kind of assumed I had preconceived notions of what the worst of that job might be, but she was talking about handwriting on labels the same ID number over and over, double checking, cross checking, the amount of paperwork and labeling, and then at the end, packing and shipping was the tedious and unpleasant part of her job, not the opening up of a leg and the extracting of bone or ligament. I guess I just wasn't expecting that.
On how knowing too much about how our bodies work can get in your head
When I wrote Gulp ... I became really aware of what's going on in your mouth when you chew, the process of bolus formation, where you're taking a piece of meat, say, and you're breaking it down and then you're putting it back together in a bolus that's a shape that can slide down the throat. And I visited somebody who studies chewing and this process and what the jaws do, and I remember for a while after that going to restaurants and thinking, looking around at people chewing and swallowing and thinking this is disgusting. People should have sex in public and eat in private! It's absolutely disgusting.
Sam Briger and Susan Nyakundi produced and edited this interview for broadcast. Bridget Bentz, Molly Seavy-Nesper and Carmel Wroth adapted it for the web.
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