CLOSE
Juan Carlos Izpisua Belmonte
Juan Carlos Izpisua Belmonte

Biologists Grow Human Cells Inside Pig Embryos

Juan Carlos Izpisua Belmonte
Juan Carlos Izpisua Belmonte

Let’s all take a deep breath. The lab-created “pig/human hybrid” being reported in the news this week is real, but it’s not quite the monster you might imagine. Researchers from the Salk Institute, who published their results in the journal Cell, have successfully coaxed human cells to grow inside pig embryos.

Chimeras (hybrid organisms) have always been a sticky issue both scientifically and ethically. Public opinion about this kind of science is hardly favorable, and the National Institutes of Health and other research bodies will not fund studies that involve the implantation of human stem cells into the eggs and embryos of other animals.

 

But many scientists, including the authors of the new paper, feel it’s important to keep doing it anyway. The first phase of the current research, which was funded by supporters of the Salk Institute, involved creating a cross between a rat and a mouse by implanting rat cells into mouse embryos. (Earlier this week, we reported on similar research in which scientists grew mouse organs inside rats, then transplanted them back into mice.) The researchers used gene editing to encourage those cells to develop into specific parts of the mice, including their eyes, hearts, or pancreata. They even coaxed the rat cells into becoming gallbladders—a very impressive feat, since rats don’t actually have gallbladders.

"This suggests that the reason a rat does not generate a gallbladder is not because it cannot,” co-author Jun Wu of the Salk Institute said in a statement, “but because the potential has been hidden by a rat-specific developmental program.”

Next, the team attempted to try the same technique with human cells and non-human animal hosts. They decided to use cows and pigs, since their organs are naturally similar in size to our own.

But rats and mice are much more closely related to each other than pigs and humans are, so the process proved much more complicated. Part of the difficulty involved timing: Pig embryos develop faster than humans do.

"It's as if the human cells were entering a freeway going faster than the normal freeway," said lead investigator Juan Carlos Izpisua Belmonte. "If you have different speeds, you will have accidents."

 

After four years of work by more than 40 people, the researchers achieved their goal. Human cells acclimated to pig embryos and grew inside them alongside the pigs’ own parts. The growth period was brief (3 to 4 weeks); the researchers cut the experiment short well before the embryos became piglets. They were not about to create actual ManBearpigs.

"The ultimate goal is to grow functional and transplantable tissue or organs, but we are far away from that," Izpisua Belmonte said. "This is an important first step."

nextArticle.image_alt|e
iStock
arrow
science
The Surprising Reason Why Pen Caps Have Tiny Holes at the Top
iStock
iStock

If you’re an avid pen chewer, or even just a diehard fan of writing by hand, you’re probably well acquainted with the small hole that tops off most ballpoint pen caps, particularly those classic Bic Cristal pens. The reason it’s there has nothing to do with pen function, it turns out. As Science Alert recently reported, it’s actually designed to counter human carelessness.

Though it’s arguably unwise—not to mention unhygienic—to chomp or suck on a plastic pen cap all day, plenty of people do it, especially kids. And inevitably, that means some people end up swallowing their pen caps. Companies like Bic know this well—so they make pen caps that won’t impede breathing if they’re accidentally swallowed.

This isn’t only a Bic requirement, though the company’s Cristal pens do have particularly obvious holes. The International Organization for Standardization, a federation that sets industrial standards for 161 countries, requires it. ISO 11540 specifies that if pens must have caps, they should be designed to reduce the risk of asphyxiation if they’re swallowed.

It applies to writing instruments “which in normal or foreseeable circumstances are likely to be used by children up to the age of 14 years.” Fancy fountain pens and other writing instruments that are clearly designed for adult use don’t need to have holes in them, nor do caps that are large enough that you can’t swallow them. Any pen that could conceivably make its way into the hands of a child needs to have an air hole in the cap that provides a minimum flow of 8 liters (about 2 gallons) of air per minute, according to the standard [PDF].

Pen cap inhalation is a real danger, albeit a rare one, especially for primary school kids. A 2012 study [PDF] reported that pen caps account for somewhere between 3 and 8 percent of “foreign body aspiration,” the official term for inhaling something you’re not supposed to. Another study found that of 1280 kids (ages 6 to 14) treated between 1997 and 2007 for foreign body inhalation in Beijing, 34 had inhaled pen caps.

But the standards help keep kids alive. In that Beijing study, none of the 34 kids died, and the caps were successfully removed by doctors. That wasn’t always the case. In the UK, nine children asphyxiated due to swallowing pen caps between 1970 and 1984. After the UK adopted the international standard for air holes in pen caps, the number of deaths dropped precipitously [PDF]. Unfortunately, it’s not foolproof; in 2007, a 13-year-old in the UK died after accidentally swallowing his pen cap.

Even if you can still breathe through that little air hole, getting a smooth plastic pen cap out of your throat is no easy task for doctors. The graspers they normally use to take foreign bodies out of airways don’t always work, as that 2012 case report found, and hospitals sometimes have to employ different tools to get the stubbornly slippery caps out (in that study, they used a catheter that could work through the hole in the cap, then inflated a small balloon at the end of the catheter to pull the cap out). The procedure doesn’t exactly sound pleasant. So maybe resist the urge to put your pen cap in your mouth.

[h/t Science Alert]

nextArticle.image_alt|e
Mark Ralston/AFP/Getty Images
arrow
Big Questions
What Causes Sinkholes?
Mark Ralston/AFP/Getty Images
Mark Ralston/AFP/Getty Images

This week, a sinkhole opened up on the White House lawn—likely the result of excess rainfall on the "legitimate swamp" surrounding the storied building, a geologist told The New York Times. While the event had some suggesting we call for Buffy's help, sinkholes are pretty common. In the past few days alone, cavernous maws in the earth have appeared in Maryland, North Carolina, Tennessee, and of course Florida, home to more sinkholes than any other state.

Sinkholes have gulped down suburban homes, cars, and entire fields in the past. How does the ground just open up like that?

Sinkholes are a simple matter of cause and effect. Urban sinkholes may be directly traced to underground water main breaks or collapsed sewer pipelines, into which city sidewalks crumple in the absence of any structural support. In more rural areas, such catastrophes might be attributed to abandoned mine shafts or salt caverns that can't take the weight anymore. These types of sinkholes are heavily influenced by human action, but most sinkholes are unpredictable, inevitable natural occurrences.

Florida is so prone to sinkholes because it has the misfortune of being built upon a foundation of limestone—solid rock, but the kind that is easily dissolved by acidic rain or groundwater. The karst process, in which the mildly acidic water wears away at fractures in the limestone, leaves empty space where there used to be stone, and even the residue is washed away. Any loose soil, grass, or—for example—luxury condominiums perched atop the hole in the ground aren't left with much support. Just as a house built on a weak foundation is more likely to collapse, the same is true of the ground itself. Gravity eventually takes its toll, aided by natural erosion, and so the hole begins to sink.

About 10 percent of the world's landscape is composed of karst regions. Despite being common, sinkholes' unforeseeable nature serves as proof that the ground beneath our feet may not be as solid as we think.

A version of this story originally ran in 2014.

SECTIONS

arrow
LIVE SMARTER
More from mental floss studios