Meat Doesn’t Grow on Trees But Maybe It Could

Illustration by Matt Panuska

What if your steak came from the greenhouse instead of the slaughterhouse?

To make meat out of animal cells but no actual animals, you have to solve a big (meaty!) problem: Where do you grow the stuff?

Though it might sound like a vegetarian’s nightmare, the answer could be to produce the meat on plants.

Glenn Gaudette is seeing if he can make that happen. A professor of biomedical engineering at Worcester Polytechnic Institute in Massachusetts, Gaudette is growing cow muscle cells on spinach leaves.

It’s early days — Gaudette told at the New Harvest conference at MIT last Friday that he will have data in a couple of weeks. But experts in the field of lab-grown meat (also known as “cultured meat” or “clean meat”) say that Gaudette could be addressing one of the technology’s big problems. Plant leaves could give cultured meat a scaffold that also happens to be edible.

Brian Spears, CEO of the startup New Age Meats in San Francisco, heard the idea for the first time in Gaudette’s presentation at New Harvest. “That was really exciting,” he says. “We’re going to try that.”

Growing meat without using the body of an animal might be more environmentally sustainable. But the meat cells need to multiply on a structure that supplies them with nutrients, as blood vessels do in an animal.

Joshua Gershlak, a graduate student working with Gaudette, pointed out that plants feed their cells with blood-vessel-like structures with the same branching patterns seen in animal tissue. So they used detergents to strip the plant cells away from spinach leaves, a process called decellularization. What’s left behind looks like a spinach leaf, but it’s pale white and has a texture like Styrofoam. Last year they coaxed human stem cells to grow into beating heart tissue on this spinach skeleton—work that might have implications for tissue regeneration technologies. Now they are trying to get cow stem cells to develop into the muscle cells that make up a tasty steak or hamburger.

Various other materials exist for growing cultured meat. Some that work well as scaffolds, including materials known as hydrogels, are not necessarily edible, meaning some other step will be needed to remove the meat. As for the edible options, there are silk, chitosan (from shrimp and other crustaceans), zein (from corn), and alginate (from seaweed). “But whether cells grow well on them is another matter,” says Marianne Ellis, of the University of Bath, a biochemist and tissue engineer who is collaborating with Gaudette.

A decellularized spinach leaf (left) and one with bovine blood in it, which could nurture the growth of a cow’s meat cells. (Courtesy of Glenn Gaudette)

Even though growing meat on leaves could be cheap and clean, there are big obstacles. The most fundamental is that no one knows how well animal stem cells grow on plant skeletons, because no one has tried it. “Stem cells are notoriously finicky,” says Spears. To grow into the kind of cells that make up a sausage or steak, the cells need to not only grow and thrive, but they must also differentiate properly into skeletal muscle cells, and not veer off into some other kind of cell or revert to stem cells.

Stephanie Wallis, chief scientific officer of Higher Steaks, a cultured meat company in London, says she believes cultured muscle cells won’t grow properly if the scaffold doesn’t have the exact right shape or provide the proper distance between cells. Stem cells too densely packed will die, become unhealthy, or differentiate into the wrong kind of cell.

Plant leaves have a structure that can’t be manipulated and customized as easily as other scaffolding materials, says Wallis. But there’s a chance that’s OK: plants come in a wide variety of shapes and sizes, and maybe one of those is already perfect for growing cultured meat. Gaudette and Gershlak have decellularized not only spinach but also other kinds of leaves, including parsely.

To grow meat this way, researchers will need to ensure that the detergents used to strip the plant cells away don’t leave any residue that’s either harmful or bad-tasting.

Ellis says she and her students can’t yet test whether plant-based scaffolds affect the taste of cultured meat, either for better or worse. Because food isn’t allowed in most scientific labs, she says, “they’re not allowed to eat the research yet.”

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