• Question: HOW MANY PARTS OF THE HUMAN BODY IS IT POSSIBLE TO REPLACE?

    Asked by anon-252589 on 1 May 2020.
    • Photo: Kim Liu

      Kim Liu answered on 1 May 2020: last edited 1 May 2020 8:32 am

      This is a tough question to answer, because the words ‘possible’ and ‘replace’ mean there are a lot of answers! I’ll try some; others will help I’m sure.
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      Easiest answer: none; we can’t yet make living replacement body parts for ourselves. There are special cells called stem cells which in principle can be transformed into any other body part for us, but we do not have the bioengineering capacity to use this to replace organs yet. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

      Another easy answer: All of them! Your body is constantly growing cells to continuously regenerate your tissues. But we don’t have much control over this process, though it is a very important question in aging.
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      Organs of the human body can also be replaced by donations from other humans; this works with some success with kidneys, lungs, the heart, liver, pancreas, skin, stomach, intestines and bones; there are probably more.
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      Hands, feet, legs, arms, hips, joints can be replaced with prosthetics built from non-organic materials. Pacemakers can also generate artificial heartbeats, and hearing aids help with hearing loss.

    • Photo: Anabel Martinez Lyons

      Anabel Martinez Lyons answered on 1 May 2020:

      Great question – in terms of which organs and tissues can be successfully transplanted (given from one person to another to replace that person’s faulty/dysfunctional organ), these are the heart, kidneys, liver, lungs, pancreas, intestine, thymus, uterus, and the skin. Parts of organs can also be transplanted, like heart valves, bits of bone or the cornea (front part of the eye). It is also possible to transplant soft tissues like tendons, nerves and veins. Worldwide, the kidneys are the most commonly transplanted organs, followed by the liver and then the heart. Hope that answers your question :-).

    • Photo: Nina Rzechorzek

      Nina Rzechorzek answered on 1 May 2020:

      Great question – it depends on what you mean by ‘replace’. If you mean an exact natural replica of the original that’s much more challenging than say, a synthetic version like a hip replacement. At the moment, we definitely cannot replace the brain, but some clinical trials have used stem cells to try and replace specific brain cell types lost in Parkinson’s disease

    • Photo: Candice Ashmore-Harris

      Candice Ashmore-Harris answered on 7 May 2020:

      Some great answers already, to add to these I work in ‘regenerative medicine’ meaning we are looking at how you can use different therapies to regenerate or repair damaged organs or parts of organs (as there aren’t enough donors for all the people that need replacement of whole organs). 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 (including stem cells) that either replace the lost function of the damaged cells or encourage the damaged tissue to fix itself based on signals released by the transplanted healthy cells. 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 a compatible donor which will grow over/into the scaffold. The idea is they may be able to produce a new functioning organ that could then be transplanted as a replacement. 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).

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