Big Idea: Using plant leaves as scaffolding to grow human cells

Wisconsin’s best-known naturalist, John Muir (who took his first botany class at UW–Madison), said that when one tugs at a single thing in nature, he finds it attached to the rest of the universe. Biomedical engineering professor William Murphy felt that pull one spring day in 2014 from his office chair, staring at the Lakeshore Nature Preserve while contemplating the tiny, highly processed chips he’d been developing to grow microscale human tissues.

“We do a whole lot of complicated engineering to make them,” says Murphy. “Looking at a leaf, you can see all of that engineering embedded. So it was really just looking out the window and thinking, you know, here’s a template for the way that we ought to be making these human tissues.”

Though they kept their “little bit goofy” work quiet for two years, Murphy and his students—soon collaborating with Worcester Polytechnic Institute, Arkansas State University, Olbrich Botanical Gardens and the UW Arboretum—compiled enough data to support the astonishing hypothesis now published in two manuscripts: that plant leaves, stripped down to their bare, cellulose level, become the perfect scaffolding in which to grow human stem cells. In some cases, 50 times more cells are grown through scaffolding than the current (and finite) practice of growing them on flat plastic plates. And if you can grow human stem cells from renewable, biodegradable materials, you could eventually repair muscle, organs and bones from simple, inexpensive, scalable sources like parsley and elephant ear.

“Both heart muscle and skeletal muscle [are] difficult to regenerate,” says Murphy, for two key reasons. One, they’re highly vascular, requiring so many blood vessels to feed cells. Two, in order for muscle to functionally contract, cells must be aligned in a particular direction. Within plant scaffolding, Murphy’s team found that leaf structures not only have an “incredible ability” for mass transport, moving and expelling fluids rapidly and efficiently from one end to the other, but that human cells pattern themselves in the same aligned and structured direction as the plant tissue.

“One of the things that’s special about the University of Wisconsin–Madison is that the students are not just very bright, they have this entrepreneurial spirit. They’re highly creative, and when they explore a new idea, they want to turn it into something significant that can really affect human lives,” says Murphy, who hopes this might open up an entirely new field of study. “Maybe at a lot of institutions this plant idea could be sort of a fun conversation at a meeting, but wouldn’t turn into something significant. Whereas at Wisconsin, it’s turned into a research initiative. And now we’re continuing to pursue it toward affecting human lives.”