Scientists Pioneer Surgical Methods for Human Head and Eye Transplants

0:28This episode is brought to you by Accenture. We have two extraordinary breakthroughs in transplant surgery to report today. The first is a way to keep human eyes alive after death so that you might be able to do an eye transplant. And the second is a way to fuse a severed spinal cord and, you know, potentially that could allow people with spinal injuries to walk again and also potentially pave the way to so-called head transplants, body transplants, I think they should be called. They should. Now, we have a rule, as you know, in New Scientist, you're not allowed to say this is like something out of science fiction.

1:00So don't say it, Rowan. No, I have to say it. I have to say it. In this occasion, rules are there to be broken. Eye transplants and a body or head transplant, that is very science fiction-y. We're not reporting that yet, but we're reporting significant steps towards those kinds of surgeries. So that is definitely reminiscent of science fiction. All right, I'll allow it. From New Scientist, this is the world, the universe and us. I'm Dr Penny Sarsha. And I'm Dr Rowan Hooper. and we're joined by biomed editor Alexandra Thompson. Alex, let's start with a retina transplant story. Yes, so retinas are the light-sensitive tissue at the back of the eye and they convert light into electrical signals that the brain can interpret as images.

1:41So what scientists have done is they've perfused donor human retinas with blood and oxygen so they continue to respond to light for up to 10 hours after death, which is a really significant step towards eye transplants that restore vision. Yeah. I think it's worth sort of stressing just how amazing the retina is because we can keep all kinds of bits of humans alive, can't we? But the retina, like you say, is this sheet of light-sensitive cells. They're all kind of doing these special chemical reactions constantly to sense light and then all of that ultimately needs to be sort of plugged in to neurons in the brain.

2:17It's an incredibly sort of delicate thing to work with, isn't it? and so I guess the idea here is to then one day be able to transplant an entire eye so that someone can see again. That's the step on the road that we're on to but it's not quite so simple because we still need to connect it to the optic nerve but that doesn't take away from this tremendous feat. Retinas are famously wired backwards as you know. Backwards I'll say, remind me. So the blood vessels go in on top of the light sensing cells. Oh yes. So it's an argument against intelligent design because if you had designed it you'd have the light sensitive cells first and then the the blood vessels connecting behind it and not blocking the light am i misremembering this but the octopus got it right and we got it wrong yeah you can't get a detached retina exactly well done octopuses um yeah so eye transplants have been done but the eye has been kept alive but hasn't become functional again yeah so this is the important bit keeping uh the retina functional and then maybe stitching it back together again or connecting it back to the optic nerve is what you need to do.

3:23And so potentially might something like that be useful for things like age-related macular degeneration because these are sort of these conditions that are actually very common and take our sight but are really hard to treat. They are really hard to treat. They affect, well, that particular condition affects tens of thousands of people in the UK alone and treatments are very limited. There are some advances. So the idea of a transplant related to the eye isn't totally new. We do cornea transplants, but that's the sort of clear window at the front of the eye. And that can improve vision if you have a damaged cornea.

3:58But treating the retina is much more challenging because it's so sensitive to a loss of oxygen. And I should also say that there was a partial face and whole eye transplant in 2023, which was fantastic for the person who received it, but it didn't restore his vision. yeah I was looking at that Aaron James the guy's name was and he'd had this um an accident at work a massive electric shock to his face burnt it all off gosh and I always find these face transplant stories so moving because you're you are you're getting another chance at life from someone else's face and then it transforms your own life and he said you know he's grasping this opportunity with both hands he's got a second chance at life and it's it's just really moving yeah but as I say that eye so they transplanted one of the eyes but um it it didn't restore the vision in that eye that was damaged but at least he has a living eye in that on that side of the face but i was thinking about this like how technically hard is an eye transplant you know how do you even access all the stuff at the back of the eye yeah i don't know how they go about doing microsurgery and things like that well because it's the eyeball and and then ideally you then also want to plug in the retina that's got to be one of the most complex things to possibly but you have to get behind there and get inside it and the case study you just mentioned he didn't have scarring no i know it's amazing it's amazing stuff uh probably not worth looking too more deeply into that it's gonna be really squeamish to see how they did it but alex tell us a bit more then about this new procedure um about how they managed to actually keep the retinas alive you mentioned that the retina is really sensitive to oxygen levels and that's kind of critical here isn't it?

5:40It is so this was achieved by scientists creating what's called eye in care box so what this meant was that they inserted a flexible tube into the ophthalmic artery which supplies blood to the eye and its surrounding structures and then they perfused that eye with an oxygenated solution within the box and there were sensors to automatically regulate pressure and flow and then to put it to the test they took both eyes from six donors one was perfused one wasn't and they found that the perfusion system preserved the structure of the retina and maintained the health of the surrounding cells for up to 24 hours but the non-perfused eyes degraded very quickly after removal and then they found with another group of larger donor eyeballs that 15 out of 36 of the retinas produced electrical responses to light when perfused.

6:33So that is what we mean by them being active or alive outside of the body for so long. And it's quite similar, the responses they were having as what we see in living people. And it's quite the feat because in 2022, this was achieved for five hours, but now they've doubled it and done it for up to 10 hours after death. It gives you 10 hours to do that incredibly complicated transplant you just try to imagine. Well so in Minority Report Tom Cruise had it done quite quickly and then had to suddenly like skip the healing process and get his new eye open. It was disgusting. Well that's what we're getting talked towards.

7:08Yeah but we still have a way to go so it's not clear why not all of the eyeballs had that response to being perfused. Huge challenge that before we can restore vision via a transplanted eye is regenerating the fibres in the severed optic nerves, it can connect to the visual centers in the brain. This new work doesn't solve that, but by keeping the eye metabolically healthy for so long after death, it does make those sort of vision restoration strategies seem much more feasible. Amazing. This episode is brought to you by Google Chrome. You think you know a browser, but Gemini and Chrome, that's new.

7:42It can help you with practically anything on the web, like restoring a vintage motorcycle from a 50-page restoration block, or finally break down that long article you've had open for weeks. Gemini and Chrome is here for it. Ready to make anything online make sense? There's no place like Chrome. Check responses set up required compatibility and availability varies 18 plus. So that brings us really nicely to the other story we want to talk about today, which is the restoration of a severed spinal cord. And the initial aim of this kind of research is to treat spinal cord injuries, which can leave people unable to use their limbs.

8:15And there are more than 15 million people living with spinal cord injury. So a way to restore this would be brilliant. Yeah so that's the legitimate side of the paper but someone on this paper on the team is a neurosurgeon who's famous at New Scientist Sergio Canavero and he's the one who's been very open about wanting to perform head transplants or body transplants as we should call it in humans. Yeah and we'll get to that in a minute. Alex the neurosurgery in this particular study concerns fixing the spinal cords in pigs who've had their spinal cords severed. And so what they essentially did is they fixed this injury that was inflicted on them and these pigs were able to walk again.

8:56It's gruesome, but quite amazing. It is quite gruesome. They had to sever the spinal cords of pigs. And for some of them who actually controls, they stayed severed. It's been done at her institute in Russia using fusogenic neurosurgery. Yeah, and it's significant that it is in Russia that this sort of stuff goes on because the regulations are, let's say, looser there for this kind of very experimental neurosurgery. And also there's a law coming to pass in September in Russia that will allow nerve, spinal cord and fragments to be added to the list of authorised transplant tissues. And apparently Helen Thompson, who reported this for us, said that there's no other countries where they allow that.

9:39So this is the only country so far that you're allowed to muck around with, or you will be allowed to do this kind of transplant with spinal cord tissue. So what is fusogenic neurosurgery? Okay, it's quite complicated, but in a nutshell, the animals are anesthetised. They remove the bony arch that surrounds their spinal cord. The area is cooled and then they slice through that spinal cord with a sharp blade in the mid-back region. So that sort of mimics the most severe spinal cord injury. It cuts off the connection between the brain and the body below the abdomen. They stabilise the spine around that area and place two cut ends of the spinal cord close together.

10:18And then the animals are given this fusogen. So that's composed of polyethylene glycol and a biological polymer called chitosin, which is derived from crustacean shells. That's injected to the injury site. It's infused into the pig's blood. and then all of the animals including the controls received electrical stimulation to each limb every day twice a day and they also had drugs to reduce inflammation and bowel obstruction. Immediately after the surgery all the animals had motor and sensory paraplegia in their lower limbs and pelvis and that persisted in the control animals but in the treated group one animal started to move its hind limb on day two and all three responded to pinpricks in some area of that leg and by day seven one animal had attempted to stand wow gosh and then i should say that by the end of the 60-day study all three treated pigs could walk they were a bit unsteady on their feet and they had recovered pelvic control and some sensitivity to touch so um that implies then that there is some kind of electrical conduction going across this wound.

11:25So it sounds like you've got PEG, which is kind of a gel, isn't it? And chitosan, it's like a structural polymer. So this is like a clever kind of a glue to bring the severed bits together. And then what? The electrical stimulation then is trying to get it all sort of working together again? Yeah. I mean, someone once explained it is like if you have two spaghettis and you put them together, two bundles, some of them will touch. So it's almost like they're connecting that way. In reality, the spinal cord is not that simple. It's actually a dense bundle of axons and there's immune cells and blood vessels and supporting tissue.

12:01And all of these undergo damage when they're injured. So even if there are some connecting spaghetti, it doesn't mean it's going to promote a full recovery. And actually, previous work in mice suggests that that recovery depends on guiding axons back to their natural targets. and just random regrowth isn't effective, which is why in the past some people haven't been that accepting of fusogens and all that they promise. So to go back to the rationale behind this, as we said, more than 15 million people live with spinal cord injury and potentially methods like this could be an approach to handle that, to improve life for them.

12:39Yeah, I mean, as you know, there are other ways, but they're not really very wide. Well, they're not at all widely available. Not yet. Yeah, not yet. And so if you have a spinal cord injury, there's not much you can do about it. So that's what they're ostensibly trying to get towards. But Sergio Canavero is something of a controversial figure. Nice understatement there. Yeah, something of one. He said he's trying to do body transplants. I think he's done them in pigs, not dogs. That was a previous Russian experiment way before him. But yeah, there have been some pretty gruesome animal experiments.

13:17And he does want to try transplanting a human head onto a different body. Yeah. And the next step will be to do this experiment in a larger group of animals. And then maybe down the line in humans, something similar has been tried in cadavers. But it's a long way from demonstrating that it's safe and effective in living people. Yeah. I mean, Canavero is still talking, just to get back to him again, He is still talking about this as if it's a really feasible, plausible thing that he intends to try doing the body transplant in humans. And ultimately, it would be a brain transplant, what he's talking about.

13:53And the idea that futurists like to think about is when your body wears out, you just take your brain, put it in a nice young new body. But yes, very grim. Can I just unpick that? Because I can see why certain types who want to live forever would want the option of swapping onto a new body. but if we're thinking about this as a potential way to get a new body for people who have lost the use of their body which is which has been one of the sort of stated aims if that involves coming up with this technology to fuse the spinal cord because you have to do that as part of the transplant yeah and make it work why why can't we just do that so that the body you've got starts working again why would you need to swap another one in what's the logic there yeah i mean that's probably a massive plot hole in their argument, isn't it?

14:42So it does sort of hint towards it's the life extension thing rather than... And we want a nice young body rather than a saggy old one or a damaged one, you know, ravaged by a son and injury and illness and all of that. Yeah, it does really show the extremes that life extensionists are prepared to go to. Yeah, or at least they're prepared to talk about going to. Let's see whether they actually go to it. Rowan you did mention other attempts to sort of deal with this problem of what happens when you have a severed spinal cord and and there are ones that are less grotesque but it is still a really big job and requires a you know these kind of big feats of bioengineering back in 2022 a man with a severed spine was actually able to walk thanks to a spinal implant that sort of boosted his nerve signals that came down from the brain and sort of helped them jump across or get around the break yeah um and so i think you know there are various attempts like these and that you know nothing's going to be a really easy fix but i think if i had to put money on on something helping people with spinal injury to walk again that's where i'd put mine rather than the head transplant route yeah fair enough i'll accept that all right that's all for this week uh thanks to our guest alexandra thompson and thanks to you for listening do subscribe and follow us wherever you get your podcasts bye for now bye

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