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A new experimental design that can sustain mouse embryos outside the uterus means that soon, we may be able to watch mammalian embryo development in real time.

Hosted by: Hank Green

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Sources:
https://www.nature.com/articles/s41586-021-03416-3
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[♪ INTRO] “Artificial wombs” might sound more like science fiction than science.  But in a recent study in the journal Nature, scientists described an artificial womb for mouse embryos that actually worked!  And it could bust the field of developmental biology wide open.  Here’s the thing about mammals: typically, their embryos need to grow in a living uterus, and that makes it kinda hard to study their development.

We can’t exactly peek our heads in there to see what’s going on. And that’s a real shame, since mammals are the best models for understanding exactly what goes on in pregnant people’s bodies — intel which could help us prevent and treat conditions that can arise in utero.

Now, we might actually be able to watch mammalian development happen in real time, thanks to an experimental setup that can sustain mouse embryos outside the uterus. This artificial womb consists of clear vials filled with nutrient-rich fluids attached to a rotating wheel. The rotation keeps the embryos from sticking to the walls of the vials, which can interrupt development.  These researchers didn’t invent this setup from nothing; it’s based on previous experiments.  But those attempts only managed to sustain the embryos for a day or less.

A big factor in this team’s success was the ventilation system they designed, which provides oxygen and carbon dioxide to the embryos.  With it, the researchers could precisely control the concentration and pressure of these gases, which allowed them to better mimic what fetuses experience in utero.   And it worked!  In their study, they report taking mice fetuses out of the uterus after 5 days of development, and sustaining them in the artificial wombs for another 6 days. The scientists also claim that, in as of yet unpublished experiments, they’ve made it 11 days starting with 0-day-old embryos — so, ones pulled from the parent mouse straight after fertilization. Either way, that’s about halfway through the mouse’s 20-day gestation — around the time the fetuses start developing legs.

And most incredibly, the lab-grown embryos appeared to develop normally. But they only made those 11 days, and the scientists think that’s because they haven’t quite figured out how to scale up the nutritional supplement for the next stages of development.  The team’s already working on solving that, though, and are making progress with more recent experiments. They hope that, soon, they’ll be able to grow mouse embryos from fertilization to birth in their artificial womb.

And if they succeed, their technology would allow for highly detailed embryological studies, which could help answer all sorts of questions about problems that can arise during development. It also may open the door to major ethical questions about artificially-grown animals or even humans... but we’ve still got some time before we crack that can of worms.  While we’re on the subject of sci-fi worthy medical tech, though: another team of researchers recently reported that they’ve produced an artificial heart valve that could make it much easier to treat children with heart conditions. You see, our circulatory systems, including our arteries, veins, and hearts, use valves to control the flow of blood.

If these don’t work properly, a person may need surgery to replace them with artificial versions.  But that’s not so straightforward when the patient is a child, because children grow, and artificial valves don’t. A kid with a heart condition may have to replace their valves half a dozen times before they reach adulthood and stop growing. That’s a lot of heart surgeries!

But according to the new paper published in Science Translational Medicine, it’s possible to create valves in the lab that grow!  To make these growing valves, the researchers started with skin cells from sheep. They placed these cells inside a tube of gel that encouraged them to develop an extracellular matrix: the soft tissue between cells that holds them together and facilitates cellular communication. Once the cells had done this, they were washed away, leaving behind a tube of this matrix.

The researchers then knit multiple tubes together to create a flexible matrix in the shape of a heart valve.  The trick ended up being getting the right toughness.  Their early attempts weren’t strong enough at the seams, so the valves fell apart over time when they faced the pressure of actual blood. But eventually, the researchers came up with a multi-tube design that held together and functioned like a normal valve. And when they implanted these tubes into living lambs, the lambs’ native cells invaded the empty matrix and took over the task of keeping it healthy.

Their cells even expanded it as needed, so that the valves remained functional for twelve full months as the lambs developed into adult sheep. The researchers think the same thing could be done with human cells to replace human valves — so their next step is to get approval for clinical trials. Every year, hundreds of children need to undergo heart surgery to replace defective valves.

So if this technology ends up working in people like it did in those lambs, it could remove the need for repeated operations, and make those kids’ lives a lot easier! Which would be great, because it’s not every day that a scientific study is so heartwarming. Thanks for watching this episode of SciShow News!

For more of the latest breakthroughs in science, be sure to tune in right here every Friday.  Or, you can just click that subscribe button and ring the notification bell, and you’ll get notification for all our new episodes! It’s really just that easy!  [♪ OUTRO].