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Stem Cells Grow a Liver

July 7, 2013

liver

For the first time, scientists report in Nature that they have grown functional liver tissue from stem cells. While they did not form an entire liver, the human cells formed organized liver tissue that functioned as such once transplanted into an immunodeficient mouse (to avoid rejection).

In the past, researchers have feared that forming whole new organs (or even mini-organs) would be impossible–too complex for isolated stem cells. Forming an organ requires more than differentiation of specialized cells. It requires cell-to-cell communication, to form organized sheets (epithelia) with upper and lower sides; and it requires vascular cells to form blood vessels snaking into the tissue to supply it with nutrients. An inordinately complex operation.

And yet, it happens every day in new, natural embryos. Somehow the single fertilized cell generates various cell types that interact and instruct each other to form organs. So why not in a culture dish?

So the researchers tried mixing three different types of early-differentiated stem cells, all from so-called “adult” stem lines; the kind of stem cells that persist after the body develops. They took immature liver-destined stem cells, and combined them with endothelial cells (cells from the interior lining of blood vessels) and mesenchymal cells (embryonic-type cells that develop into connective tissues, bone and cartilage). The endothelial and mesenchymal cells allowed the immature liver cells to “self-organize” into tissue forms including blood vessels, apparently by “recapitulating” the cell-cell communications that occur during normal organogenesis.

Only a small liver bud formed; but the bud was “functional” in the dish. That is, it produced liver-specific proteins and performed liver metabolism such as detoxifying drug molecules (a key function of the liver). Moreover, functional liver buds took root when implanted within a mouse abdomen, or even (bizarrely) within the mouse brain.

These findings are medically relevant because we know already that a small transplanted part of a liver can grow into a full liver of normal size and function. While the current liver buds are still way too small, nevertheless, it looks like formation  growing a new liver may be less far off than we thought. This is the kind of research I imagined in Daughter of Elysium.

2 Comments
  1. Alex Tolley permalink
    July 8, 2013 11:12 am

    This experiment caught my eye too. We seem to be making progress in developing organs from stem cells. It seemed that we would need scaffolds to do this, but maybe that was unnecessary. If the organs can be grown to mature size, that would have huge medical implications.

    My question however, is how useful will this be medically? The idea is to use your own stem cells so that immune suppression isn’t needed. But unlike the movies, growing any organ takes time, say at least 9 months and probably longer for adult sized ones. So if you have an organ failure, especially a vital organ, how does this help you? Will it require a temporary transplant before yours is ready? Will it mean having your own ready to go in a bank somewhere, ready to be shipped? (seems very expensive). Obviously we don’t want those dystopic ideas of having your clone raised as an organ donor to happen. For some systems, like the heart, you can use a pump while the stem cell heart is grown. For a liver, that wouldn’t work – you would need to diagnose failure well in advance and do the implantation then so that the new organ would grow in time to compensate for the original liver failure.. Any thoughts on this?

  2. SFreader permalink
    July 12, 2013 4:57 pm

    Perhaps implanting a bunch of small liver buds which are basically a semi-mature/-formed functional liver would work as well as waiting for the entire organ to form. There’s been some success with “mini-transplants” re: some leukemias.

    (A “mini-transplant” is a “kinder, gentler” form of allogeneic (cells from another person) stem cell transplantation. Conventional stem cell transplants are generally not performed on blood cancer patients older than 60 because the prep for ‘bone marrow – or peripheral blood stem cell transplant” can require high doses of total-body radiation and potent chemotherapy. Such a procedure completely ablates the bone marrow. Very, very risky/serious.

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