An artificial windpipe transplant in Sweden is the first trachea made from… (Karolinska University…)
The windpipe transplanted into a terminal cancer patient in Sweden is garnering much buzz – and small wonder. The surgery marks the first time a trachea grown from a patient’s stem cells and seeded onto a synthetic, rather than a donor, structure has been transplanted in a human. And it saved a 36-year-old man’s life.
The trachea isn’t the first organ born in a lab—and experts say there are many more to come. We talked to Dr. Anthony Atala, a pioneer in the field who in 1999 transplanted the first of several synthetic bladders into young people with bladder disease.
Atala now directs the Institute for Regenerative Medicine at Wake Forest University; in March, he and colleagues announced they’d transplanted laboratory-grown urethras in five boys.
In this edited transcript of a phone interview, he elaborates on the significance of the latest transplant and explains why some other organs will be more difficult to craft in the lab.
What is new in the trachea transplant that hadn’t been done before?
It’s another advance. He [Professor Paolo Macchiarini of the Karolinska Institute] had done a segment of a trachea before. He has made it a larger segment.
The scaffold he used before, the biological material he used before, was a donor organ where they took the cells away and they put the patient’s own cells. This time they did the same process, but they created a scaffold, a spongy scaffold.
Basically, there are a couple of ways of creating these tissues. One of the ways is to take a very small biopsy from a patient’s own tissue, grow the cells outside the body, and then place those cells back on that mold that replicates the patient’s organ.
Now the mold can be either something you create, something you weave like a piece of material, or it could be a donor tissue that you take the cells off and add cells to it.
What other organs have been made in the lab?
There are several organs. We did the bladder. We are 12 years out for using molds in bladders. We are seven years out in urethras, an experience just published. We showed that we transplanted urethras, using their own cells, but using molds.
Which organs are next, and which will take more time?
At this point, there are four levels of complexity.
The first level are the flat structures, like skin. They are the easiest to make because they are flat.
The next level of complexity are tubular structures, like the blood vessel, the windpipe. They are usually acting as a conduit, allowing blood or air to go through.
Next are hollow non-tubular organs like the bladder or stomach because they have to act on demand. They have much more complex functionality.
The most complex are the solid organs like the heart. They require many different cell types.
At this point, we’ve been able to do all the first three: Flat, tubular and hollow non-tubular. Skin, urethra, windpipes and bladders. Solid organs are most complex.
The fourth level– that’s going to take time – that’s still years away.
There are definitely more in the pipeline. At our institute we’re working at over 30 different tissue and organ types. There’s definitely a long list of organs that are scheduled to go into patients. It’s just a matter of getting more tissue types and more patients treated over time.
Which organs will have the biggest clinical impact?
Well, of course for any patient who needs this tissue, it’s a major clinical impact. If you need a specific tissue, it’s a big thing.
The kidneys by far, if you look at the need—90% of the patients on a transplant list are waiting on a kidney. That’s a fourth category. We are absolutely, working very hard on that (watch Dr. Atala explain how a 3-D printer could create a human kidney in this TED talk from March).
What are the biggest challenges in making these organs?
Biggest challenges right now, for any solid organ, is basically the vascularity, the blood vessel supply. There are a lot more cells per centimeter in solid than flat tissue, and therefore, a lot of what needs to be done—how do you keep so many cells fed.
In the solid organ, if you can picture the branches of a tree, and then the branches have branches, and those branches have leaves, it’s a very complex branching system. If you can picture the leaf being the tissue and the tree being the blood vessel supply tree, it’s a complex organization so you have blood flowing through the tiny cell.
How did you react when you heard about the latest transplant?
We were very pleased to hear about this work because it just represents advances in the field and further validates the fact that these technologies may have a role in treating larger numbers of patients in the future.
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