• Question: I have heard that some amphibians are able to re-grow limbs, and some scientists believe that they would be able (to some extent) make this possible in humans, for soldiers and people who have lost limbs. A) Is this theory correct? B) If it is, then do you think this would be a good idea, or could we be facing mutations, and see a result like that of \"I am legend\" ?

    Asked by caragh26 to Meeks, Pete, Stephen, Steve, Tom on 23 Jun 2010 in Categories: .
    • Photo: Stephen Curry

      Stephen Curry answered on 17 Jun 2010:

      Hi caragh26 – very interesting question. It is certainly true that some amphibians (e.g. frogs) can regenerate limbs they have lost. I don’ think we fully understand yet why they have this capacity and yet mammals do not.

      I do think there could be a good chance of exploiting this capability in medicine once it has been figured out.

      To ‘program’ humans to have this capability from birth would require genetic engineering of embryos and I’m not sure about the ethics of that one. I am comfortable with trying to eliminate killer diseases that way but making other wholesale changes could have unpredictable effects.

      But it’s a tricky area because disease-causing mutations can sometimes have benefits. For example, some mutations in the gene for haemoglobin lead to sickle-cell anemia. The mutation causes an alteration in the hemoglobin protein that makes it form long fibres; these fibres distort red blood cells, which end up blocking the fine blood vessels in the body. If both your haemoglobin genes (from Mum & Dad) have the mutation, you are unlikely to live beyond your 30s. However, people with one mutant copy and one normal copy of the haemoglobin gene are *more* resistant to infection by malaria.

      So in that case, it would be hard to know what engineering choice to make.

    • Photo: Tom Hartley

      Tom Hartley answered on 17 Jun 2010:

      A. I found this web page on the topic, it looks as though there’s something in it. Based on my own (rather quick) reading of the article it looks as if human limb regrowth is quite a long way from the basic results (but maybe there are other studies I don’t know about). Relatedly, I think it would be excellent if we could get adult cells to be “pluripotent” stem cells (which means they can grow into any tissue, like embryonic cells). Quite apart from the ethics of embryonic stem cell research (is it right to use cells from human embryos which have the potential to grow into babies?), embryonic cells are hard to come by and are not the same as those of the person who would want to use them (e.g., to grow a new bone, or whatever). So (and I really am not an expert on this) adult stem cells would be very useful all round.
      B) I enjoyed I Am Legend (sort of) but I don’t think that type of (spoiler alert) zombie apocalypse is at all realistic. I would think the main danger with regrowing limbs or other tissue is that the growth will go out of control causing cancer or a benign but unpleasant growth. But I stress I am not a medical doctor or stem cell researcher, so I don’t know much more about this than you (in fact I didn’t know about the salamanders till you raised it).

    • Photo: Pete Edwards

      Pete Edwards answered on 18 Jun 2010:

      I think I’ll leave this one to the biologists!

    • Photo: Marieke Navin

      Marieke Navin answered on 22 Jun 2010:

      Hey Caragh26, this is not my field so i’ve done a bit of googling. You’re right, the salamander can grow perfect replacements for lost body parts. I think we are a way off bring able to do this in the lab – i haven’t seen I am Legend I am afraid!

    • Photo: Steve Roser

      Steve Roser answered on 23 Jun 2010:

      I think the intersting science here is in stem cell research – these are basic cells which can reproduce to form specialised ones, such as kidney or lymph – and therefore could in principle be ued to build new organs – this could be great news.