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Asked by anon-251974 on 27 Apr 2020.
Question: I recently read the book "Pig Heart Boy" by Malorie Blackman. Do you think it would be possible to transplant the heart (or any other organ) of another animal into a human that has a problem with their heart? If so, which animal and how far in the future would this be?
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Freya Harrison answered on 27 Apr 2020:
This is very cool, but people are already doing heart valve transplants from pigs into humans! So not the whole heart, but just the valves that control blood flow – if they get diseased or damaged. Pig tissues and organs are surprisingly similar to human tissues an organs, in terms of their chemistry and immunology. Cows’ heart valves can also be used. In both cases, the valves taken from the animals have to be treated so they don’t bring infectious microbes into the person, and so that the person’s immune system doesn’t reject them. This type of animal-to-human transplant has been happening since the 1960s, and the transplanted valves can last for 10-15 years. No-one has transplanted a whole pig’s heart to a person yet, but researchers think it could be possible in the near future. How would you feel about getting a transplant organ from an animal instead of another person? There is a constant shortage of donor organs, so using animal tissue might become more common in the future.
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Eva Kane answered on 27 Apr 2020:
Transplanting a heart from a pig to a human is certainly theoretically possible, and it is something that scientists are working on as an alternative source of hearts for transplantation. Sir Terence English, the surgeon who pioneered human heart transplantation in the UK, suggested recently in an interview with the Sunday Telegraph that this could happen in the next three yearsMATOMO_URL However, it’s important to take this timeline with a grain of salt, as we never know what course the science will take and what unknown obstacles they will face. Even if the first transplantation happened in three years’ time and was successful, it would take several more years for the process to be more widely available. This is because scientists would need to ensure that the process worked in more than one person, was not overly dangerous, and that those people are carefully monitored for several years to ensure that they are healthy and do not suffer too many side effects from the process.
Pig hearts are a good option for transplantation into humans because the size and structure of the heart are actually very similar. We also know a lot about pig heart anatomy and physiology, which is useful. But it’s not the only option available – very recently, scientists in Japan successfully transplanted heart muscle cells that they had grown outside of the body into a patient suffering from a disease causing insufficient blood supply to their heart. These cells were grown from tissue taken from the patient, so there was no need to find a donor. Potentially, one day this process could be used to grow an entire heart outside of the body from a person’s own cells, and transplanted back into them.
One issue with transplantation of a pig heart (and transplanting a heart from another human) is that you need to suppress the transplant recipient’s immune system, which can leave them vulnerable to getting sick from infectious diseases. This is necessary to prevent the immune system attacking the new heart, which it will see as ‘foreign’. Using a heart grown from patients’ own cells would overcome this issue, as the immune system would recognise the heart as ‘self’.
However, growing a whole new heart in a Petri dish is not a trivial matter, so it’s important that scientists are working on several options at once, including possible transplantation of pig hearts, to ensure that they are able to help as many people as soon as they can.
*https://www.theguardian.com/science/2019/aug/19/pig-to-human-heart-transplants-possible-within-three-years-terence-english
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Anabel Martinez Lyons answered on 27 Apr 2020:
Great answers already – the process of transplanting organs or other tissues from one species to another is called xenotransplantation. To add to the ‘any other organ’ bit of your question, animal organs and tissues are already being used in human medicine. One example is that animal ligaments and tendons are often used to replace human ligaments or tendons after injury since the demand for these tissues is higher than can be fulfilled by human donation. A friend of mine has a bovine (cow) ligament in her knee, which replaced an injured ligament she got from a football injury. Also, regarding pig hearts in particular, here is a link describing a study where whole pig hearts were successfully transplanted into monkeys (which are primates like us and whose immune systems work similarly to our’s), so it’s very possible the same could be possible with humans! https://www.animalbiotech.com/blog/pig-organs-offer-new-hopes-for-heart-transplants/#more-417
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Candice Ashmore-Harris answered on 29 Apr 2020:
Some really great answers already! To add something new to what’s already been said. I work in ‘regenerative medicine’ meaning we are looking at how you can use different therapies to regenerate or repair damaged organs rather than transplanting whole new ones (because as Freya says there aren’t enough donors for all the people that need them). One of the things we look at is if you can transplant cells that have been grown in a petri dish into the damaged organ that either replace the lost function of the damaged cells or encourages the damaged tissue to fix itself based on signals released by the transplanted healthy cells. If these therapies work you could save more patients as fewer whole organs transplants would be needed!
Repairing a damaged organ won’t always be the best option. Other scientists are also looking at whether you can take an organ like a heart (either from an animal like a pig or from a human patient where their heart wouldn’t normally be suitable for transplant) and strip away the cells so that you’re just left with the 3D scaffold the cells grow in/on. This de-cellularised or ‘skeleton/ghost’ organ can then be coated with new cells from the patient or an immune compatible donor which grow over/into the scaffold. The idea is they may be able to produce a new functioning organ that could then be transplanted. Because it is coated with human cells, possibly even from the patient that is going to receive the transplant, the immune system should accept the organ as it is less likely to see it as ‘foreign’ (some nice pictures of what these ‘ghost’ organs look like if you decellularise the heart here: https://www.armiusa.org/decell-recell).
Scientists are also looking at whether you can grow whole human organs (such as the liver, kidney or pancreas) inside an animal like a pig a sheep or a goat that would be suitable (and accepted by immune cells) for transplant into people because they’re made partly from human cells. This is quite challenging to do because it involves growing a chimera (a part animal-part human organism) and these don’t exist in nature so you have to edit the genetic code very carefully. Whether this mixing of genes should be allowed has long been the subject of debate amongst scientists, government and the public, so even if it does work it might not ever reach patients (some further discussion on this here https://www.theguardian.com/technology/2019/aug/11/the-five-chimeras-human-monkey-hybrid-genetic and here: https://www.ft.com/content/1eff740c-148b-11e8-9e9c-25c814761640).
Also, did you know that pig heart boy was also made into a tv series? I remember watching it when I was at school- I would recommend it if you’ve just finished the book!
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Robert Ives answered on 29 Apr 2020: last edited 29 Apr 2020 1:40 pm
Great answers and I won’t add to them (as it’s not my speciality), but just want to say what a wonderful thought provoking book. Hope you found it an inspiring read.
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