The Science Of Replacing Body Parts, From Hair To Hearts

In “Replaceable You,” Mary Roach describes mind-boggling efforts to replace human body parts—and why it’s proven to be so difficult.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

  WNYC Studios is supported by Wise. Wise, the smart way to manage the currencies you need around the world. With a Wise account, you can send, spend, and receive in up to 40 currencies with only a few simple taps. Be smart, get wise. Download the Wise app today. Terms and conditions apply.

• 0:17Ira Flatow?

  Science Friday is supported by MathWorks, creator of MATLAB and Simulink software for technical computing and model-based design. MathWorks, accelerating the pace of discovery in engineering and science. Learn more at mathworks.com.

• 0:34Flora Lichtman?

  Hey, it's Flora Lixman, and you're listening to Science Friday.

• 0:41Flora Lichtman?

  On today's episode, the science of replacing body parts, from hearts to hair.

• 0:46Speaker 03

  If you take armpit hair and put it on the head, this is a quote from some clinic in LA, it is difficult to style.

• 0:56Flora Lichtman?

  It seems like every week, there is a new headline about some kind of sci-fi sounding organ transplant. Eyeballs, 3D-printed kidneys, pig hearts. In the new book, Replacable You: Adventures in Human Anatomy, science writer Mary Roach chronicles this effort to fabricate human body parts and why it can be so monumentally difficult. The book does not skimp on the details, and neither do we. So if you want to hear the nitty-gritty on hair transplants or vaginoplasties, today is your day. And if you don't, don't say we didn't warn you. Mary, welcome to Science Friday.

• 1:33Speaker 03

  Thank you, Flora.

• 1:34Flora Lichtman?

  This is your fifth book on the human body, I think, if I'm counting right. It's a characteristically wild ride. What keeps you curious about our bodies?

• 1:46Speaker 03

  Well, they're just endlessly amazing and weird, I think, is the answer. I mean, because I didn't study...

• 1:57Speaker 03

  Biology or physiology in any formal way. Uh, every time I step into a new system of the body, whether it's the alimentary canal, you know, the gut or sexual physiology or whatever it is, I'm just kind of gobsmacked by the stuff that's kind of going on behind the scenes, behind the curtain. It's uh, it's kind of miraculous and, and weird.

• 2:19Flora Lichtman?

  Behind the skin drapes. Yeah.

• 2:21Speaker 03

  Yeah, the skin drapes. Exactly.

• 2:24Flora Lichtman?

  Mary, let's start with a transplant that weirdly is dominating my social feeds right now. Hair transplants. What is the state of hair transplant science?

• 2:33Speaker 03

  Yeah, hair transplants are interesting. The principle by which they work is something called donor dominance. So if you take follicles from the sides or the back of the head where they're not sensitive to testosterone, they're not going to fall out. You put those on the top of the head. Now they're going to stay permanent. They're not going to fall out because they retain the characteristics of the back of the head, side and back of the head hair.

• 3:00Flora Lichtman?

  They've got that back of the head hair identity.

• 3:02Speaker 03

  Yeah, exactly.

• 3:03Flora Lichtman?

  Yeah.

• 3:04Speaker 03

  Exactly. So that's kind of the, the, the principle of it. Um, but over time, of course, if your hairline recedes, um, and it continues behind where the, the new transplants were, now you're going to have a bare patch there. So it's kind of a, an ongoing relationship between the surgeon and the patient. Um, and I looked into the history of, of hair transplants. It began with this surgeon named Okuda, Japanese surgeon. And if I found the Okuda papers and he was going crazy with the donor dominance. He was like, you can take chest hair, you can take armpit hair, put it on the head. You can take head hair and put it for, use it for pubic alopecia, which I had never heard of.

• 3:48Speaker 03

  But apparently it is something that can happen, but the

• 3:50Flora Lichtman?

  That's such a you book thing, Mary.

• 3:53Speaker 03

  I know. The Okuda papers. I was like, wow, he did that. He was like putting armpit hair on the mustache and, uh, anyway, but then it works. It all works. The, the, the issue again with donor dominance is that say you had head hair in the pubic region, now you need to trim it. Uh, if you take armpit hair and put it on the head, this is a quote from some clinic in LA. It is difficult to style.

• 4:19Flora Lichtman?

  You did some self experimentation for this book on this topic.

• 4:23Speaker 03

  Yes, I did. When I went out on book tour, I wanted to be able to demonstrate donor dominance. So I was at a hair transplant clinic in Southern California and I asked if they would transplant a follicular unit from my head to my calf so that during the book tour, I could roll up my pant leg and just show them this long luxuriant hair that was growing on my leg.

• 4:47Flora Lichtman?

  A leg pony. Yeah.

• 4:48Speaker 03

  Yeah, exactly. You know, and then it was, it had, I think it had two hair, two follicles in it. So it would have been like, it would have been two hairs, long flowing hairs. Unfortunately, it didn't take.

• 4:59Flora Lichtman?

  But they did it. Like, were they like, oh, sure, we'll do it on our lunch break?

• 5:03Speaker 03

  Yeah. Well, what happened, I was donating a dozen follicles to science. So they were studying just the process by which follicles grow, you know, from the basic cells, you know, keratinocytes and dermal papillae cells, how do they grow into a follicle so they could try to match that. So I said, sure, I will donate a dozen hairs to you and your effort. I have now a little tiny bald spot.

• 5:31Flora Lichtman?

  Itty bitty.

• 5:32Speaker 03

  Yeah, at the top of my head. And I said, well, while you're doing this, would you mind putting a few in my leg? I mean, I explained, I really want to be able to demonstrate donor dominance. You know, this is educational. It's for.

• 5:47Flora Lichtman?

  Anything for psychoms.

• 5:49Speaker 03

  Yes, exactly.

• 5:50Flora Lichtman?

  As we say.

• 5:51Speaker 03

  Exactly.

• 5:53Flora Lichtman?

  Let's talk about Judy. Tell us about Judy.

• 5:56Speaker 03

  Oh, sure. Yeah. Judy is, she's kind of the starting point for this book. She's a reader who wrote to me, going back almost four years now, and said,

• 6:10Speaker 03

  I love your books and would you write one about professional football referees? I don't know why she thought that that was a good fit for me. I don't watch football. I don't know anything about football. But anyway, in the course of emailing back and forth with her, she mentioned that she's an amputee, specifically elective amputee. It was an elective amputation. She had had spina bifida. Her, because of a tumor on her spinal cord, her foot was twisted. She wasn't able to walk on it the way she wanted to be able to walk on it. She'd had numerous surgeries that weren't really resolving the problem. And she would see people with a prosthetic lower limb who were hiking and running and doing the things she couldn't really do.

• 6:55Speaker 03

  And she tried, she was trying to find a surgeon to cut off her foot.

• 7:00Flora Lichtman?

  Trying to find a surgeon because it was hard to find a surgeon.

• 7:03Speaker 03

  It was hard to find somebody because they'd say to her, well, this is a healthy foot. It has a blood supply. It's not gangrenous. You could just get more surgeries. And, and it took her years to find someone to do the amputation. And it's an interesting issue. I mean, there are reasons why surgeons don't want to do that.

• 7:24Flora Lichtman?

  Such as?

• 7:24Speaker 03

  Such as what if there's phantom limb pain? What if the patient sues me? I can't put this foot back on. You know, it's just safer to say, let's try one more surgery. You know, safer in the sense of, am I going to help this patient or make things worse? Because there's a certain finality to cutting off a foot. It's also, you know, you need the insurance to cover it. Unless the patient wants to pay for the surgery out of pocket. So you would need to make the case that this is necessary, medically necessary. And now if the foot is not dying, that, that may be hard to do.

• 8:03Flora Lichtman?

  Right. You know, in this chapter, you write about this bias that we seem to have towards wholeness, you know, that like the whole body is better than some incomplete body. And as I was reading it, I was thinking that culturally, like in other ways, we do accept body modification all the time, Botox, collagen, rhinoplasty. And then sometimes we don't at all. And I wondered what you you made of that.

• 8:32Speaker 03

  Well, we I think we accept it if it's making us quote unquote, more attractive or more cutting edge or trendy. I think we don't accept it as much when it's perceived as a disability. There are studies that look at limb salvage surgery and otherwise, let's keep the foot, but let's just do surgery after surgery after surgery and try and get it to the point where it's almost as good as new versus let's be realistic, this is unlikely to get to 100%. Let's amputate now. And the person will ultimately be better off in terms of discomfort and function. And time and again, things land on the side

• 9:15Speaker 03

  of amputation. But I think because it feels drastic, you know, no matter how problematic that foot has been, it's you, you know, it's you and it's now it's gone. So and and I think particularly as an outsider imagining that when you're not dealing with the discomfort and the pain of this foot that doesn't really work. Well, you can't, you can't imagine that you're, you know, you put yourself in that position.

• 9:41Flora Lichtman?

  The book is filled with with stories. What was your favorite replacement from the book?

• 9:47Speaker 03

  My favorite replacement? Um, well, I found fascinating the ones in which some part of the human body is asked to become a different part. And there were a number of those. The body is very flexible, agreeable, you might almost say. I had dinner with a

• 10:11Speaker 03

  Surgeon at Cedar Sinai Center for Transgender Health and Surgery. And one of the techniques that is sometimes used is not a, it's not a common first approach, but to create a neo-vagina for a trans woman, you can take a section of the ascending colon, I think it was, and you can keep it attached to a blood supply and kind of use it as a vagina. And then also do vulvoplasty. So you have all the other, the sort of outside components, but that's something dating from the 1800s. There were patients who'd had cancer and there were a couple of surgeons who had tried that and it does work. Another one that was fascinating

• 10:53Speaker 03

  to me is that you could kind of, you could use the rectum as kind of a third lung.

• 10:58Flora Lichtman?

  Hmm.

• 10:58Speaker 03

  If, in certain situations.

• 10:59Flora Lichtman?

  Tell us about that.

• 11:00Speaker 03

  Not recreationally, but if you, if you have an infant born very, very premature, so their lungs haven't developed to the point where they're really working, you know, that means that you're going to have to go in the neonatal intensive care unit and to use a ventilator, a positive pressure ventilator on an infant that young, it can be, it can damage the lungs. So if you could augment with material through the rectum, which you can, you can, the body, the mucosa will absorb oxygen that way, then you know, you get a boost.

• 11:40Flora Lichtman?

  You can breathe through your butt.

• 11:41Speaker 03

  You can breathe through your butt, is what, what I'm saying.

• 11:45Flora Lichtman?

  That is an aha, I would say.

• 11:47Speaker 03

  You can. Yeah, you can breathe. Somebody told me about that and I'm like, so it's going all the way through. That's this like constant copious farting then? Like that, it's not, that doesn't, that doesn't.

• 11:59Flora Lichtman?

  On babies, it's cute.

• 12:00Speaker 03

  It's, exactly.

• 12:01Flora Lichtman?

  You know?

• 12:02Speaker 03

  They get away with it. Yeah.

• 12:04Flora Lichtman?

  That's right.

• 12:07Flora Lichtman?

  Hey, don't go away because coming up after the break, just how close are we with 3D-printed organs?

• 12:13Speaker 03

  We're kind of in the Wright Brothers era, if you compare it to flight.

• 12:24Speaker 00

  Science Friday is supported by PBS, presenting Going Wild. If you love learning about the natural world and meeting the scientists who help us understand it, be sure to check out the new season of Going Wild with Dr. Ray Wynn Grant. It's the chart-topping and Webby Award-winning podcast from the folks at Nature on PBS, now with a video companion series. In this season of Going Wild, host acclaimed wildlife ecologist Dr. Ray Wynn Grant heads out into the field to explore the animals, people, and stories that make nature worth saving. Stops include a hibernating black bear den in Arkansas and an underwater shipwreck site off the Florida coast. If you're looking for a place to start, check out the season's debut episode, where Ray joins beloved biologist and influencer Jordan King in the Florida Everglades to learn about

• 13:08Speaker 00

  his unlikely journey into science and how to study a wetland when it's not very, well, wet. So don't miss out. Follow Going Wild with Dr. Ray Wynn Grant on Apple Podcasts, Spotify, YouTube, or wherever you get your podcasts.

• 13:21Speaker 04

  Support for Science Friday comes from the Heising Simons Foundation, unlocking knowledge, opportunity, and possibilities. More at hsfoundation.org.

• 13:37Flora Lichtman?

  Let's talk about lab-grown organs. Where are we with that?

• 13:42Speaker 03

  Well, bioprinted organs, I asked that exact question. I was at Carnegie Mellon, the Feinberg Lab, where they're doing some very cool stuff, printing muscle in particular, and it's so much more complicated than you would think. It's not like printing a four-color brochure. And I said to Dr. Feinberg, "Wow, how long before we're at the point where we can print an organ that can be installed?" And he said, "We're kind of in the Wright Brothers era, if you compare it to flight."

• 14:16Flora Lichtman?

  But that's a big era, you know?

• 14:18Speaker 03

  Yeah, and things happened fast between Wright Brothers and plane flights, right? I mean, I don't have the timeline, but it's pretty quick. And so, stuff is moving. I mean, he said a couple of decades. And to me, that sounds slow, because, you know, to me, that's, wow, that's like three or four books.

• 14:38Speaker 03

  Whoa, that's not fast, but he's like, things are moving very quickly, two to three decades. No. So with printing muscle, it's fascinating. You, you have to align the cells so that they will perform the function for which that muscle is intended. For example, the heart, and I didn't know this, when the heart squeezes blood out, it twists slightly, kind of like wringing out a sweater. You get the maximum amount of blood expelled from the, you know, via the musculature contraction. So if you're printing a heart, say, or a ventricle, that you print them in like a helix form, as opposed to say a hamstring muscle where they're kind of parallel. So, you know, you don't really think about that.

• 15:22Speaker 03

  Plus, you know, you got to feed that muscle. So are you going to print the vasculature? You're gonna, you're there at the point where they're trying to figure out, okay, how much can we let the body do? Because the body will grow in capillaries. So some of, some of it you can get the body to do. But at a certain point, you're gonna have to print those. Nobody's printing nerves quite yet, so.

• 15:44Flora Lichtman?

  And should I be imagining a 3D printer? Or is this more like a Chia Pet? Where you have some kind of scaffolding and you sprinkle the?

• 15:51Speaker 03

  No, it's a, what I saw is a, it's a printer with like four extruder heads that are, can be printing different material, like cellular material in one, extracellular, like collagen material in another one. So, so it is, it's, it's laying down one layer at a time. So it's a, it's a, it's a printer. Feinberg teaches a course where you can take like a Office Depot printer and you can kind of like rejigger it to, to make a 3D printer. So obviously, you know, for simpler things than hearts, but it is a, it's a, it's a printer.

• 16:28Flora Lichtman?

  I'm assuming the best option for transplants is there's still organ donors, though.

• 16:33Speaker 03

  Yeah, um, yes, the best option is right now, still a human donor's organ. One of the things going on that I found kind of exciting, because it's a little bit. Simpler than printing something or growing it from scratch. At the University of Michigan Extracorporeal Life Support Laboratory, extracorporeal, meaning outside the body.

• 16:58Flora Lichtman?

  It's a great name for a lab.

• 16:59Speaker 03

  It is, totally. So, one of the things they're trying to do is extend the shelf life of a donated organ, like a heart, say, okay, the traditional method where you put it on ice and you ship it out, you've got, you know, four to six hours to get it where it needs to go. But they're looking at tweaking that so that they can extend it to a few days or more, which would be very cool because you could now bring in an echocardiogram machine and take a look at the heart, see how it's pumping, how well is it, how healthy is that heart? And you could, and if there's an issue that could be fixed, you could fix it. So, right now, you know, there's an age cutoff because it's, you don't have time to take a look

• 17:43Speaker 03

  and see how well it's working. You'd basically say, well, these are too old, so we're not going to take them. But if you could do it based on quality, that'd be helpful. And if you could repair them, that would also be helpful.

• 17:56Flora Lichtman?

  The title of the book is Replaceable You. Do you feel like we are replaceable, or our parts, anyway?

• 18:04Speaker 03

  No, the title really should be Irreplaceable You, but it doesn't sound as good. Because it's, it's a play on this song that, of course, nobody who's younger than 40 is going to know, Embraceable You, it's some old kind of standard from way back when that I happen to have heard of. But yeah, it should technically, the book should be called Irreplaceable You, because I, I don't, you know, I tried to find just, what's a simple bit of the body that we, what is, is there anything simple that we can replace so that it's 100% as good as what you were born with? And I thought about, okay, tears.

• 18:47Speaker 03

  That seems pretty straightforward, like salt water, a little bit of oil to keep it from evaporating. How hard could that be? And I, I contacted this researcher who has studied tears for decades.

• 19:01Speaker 03

  And, you know, we went on for two of the free Zooms because I'm too cheap to pay for this. We went on for two 45 minute Zooms about the tear film. And I said, so artificial tears that you buy, he goes, well, yeah, those will buy you, you know, a couple of hours, but they kind of wash away the good stuff. So, no, they're not, they're not a replacement. Uh, yeah, I mean, we, we as a, as a species have gotten pretty good at coming up with

• 19:31Speaker 03

  substitutes when things go wrong. But in terms of plugging in something that is as good as what you started out with, I, I don't, I can't name one.

• 19:43Flora Lichtman?

  Mary Roach is a science writer and author of the new book, Replaceable You: Adventures in Human Anatomy. Thanks for coming on, Mary.

• 19:51Speaker 03

  Oh, thank you so much. That was really fun.

• 19:53Flora Lichtman?

  Really fun, as always.

• 19:55Speaker 03

  Yeah, yay. Okay, thanks, Laura.

• 19:58Flora Lichtman?

  Thanks for listening. Don't forget to rate and review us if you like the show. Um, and you can always leave us a comment on this segment on Spotify. We'd love to hear from you. Today's episode was produced by Rasha Aridi. I'm Flora Lichtman. Thanks for listening.

• 20:18Speaker 00

  WNYC is supported by AT&T. We all love to connect via video call, a text, or a group chat that never stops. And right now, AT&T has a deal that will keep the connection going. You can get the new iPhone 18 Pro for $0 with eligible trade-in. It has the ultimate Pro camera system and big leap in battery life, so you can turn this deal into a long-lasting connection. Learn how you can trade in your phone for the new iPhone 18 Pro at AT&T. Connecting changes everything. Required trade-in of $230 or more and eligible plan. Terms and restrictions apply, subject to change. Visit an AT&T store for details.