To grow clusters of human stem cells that mimic organs in the lab and might be used someday in tissue implants, Bill Murphy, a UW-Madison professor of biomedical engineering, creates tiny scaffolds made of plastic or rubber.
The three-dimensional scaffolds must support the cells and feed them, help them organize and allow them to communicate.
One spring day in 2014, Murphy looked out his office window near UW Hospital, onto the university’s Lakeshore Nature Preserve, and saw a structure that does those very things naturally: plants — specifically, cellulose, the main component of the cell walls of green plants.
Now, Murphy and Gianluca Fontana, a UW-Madison post-doctoral fellow — with help from Olbrich Botanical Gardens — have grown skin, brain, bone marrow and blood vessel cells on cellulose from plants such as parsley, spinach, vanilla and bamboo.
Plants could be an alternative to artificial scaffolds for growing stem cells, the researchers reported Monday in the journal Advanced Healthcare Materials.
“Rather than having to manufacture these devices using high-tech approaches, we could literally pick them off of a tree,” said Murphy, co-director of the UW-Madison Stem Cell and Regenerative Medicine Center.
The strength, porosity and large surface area of plants could prove superior to making scaffolds using current methods, such as 3-D printing and injection molding, Murphy said.
“Plants have a huge capacity to grow cell populations,” he said. “They can deliver fluids very efficiently to their leaves ... At the microscale, they’re very well organized.”
In addition, there are many plants to chose from. After Murphy’s inspirational gaze out the window, he and Fontana tested plants as scaffolds for stem cells using varieties they could easily obtain: parsley, spinach, jewelweed, water horsetail, summer lilac and, from the UW Arboretum, softstem bulrush.
Then Fontana asked John Wirth, Olbrich’s conservatory curator, about other species that might work. Wirth invited Fontana to walk through the tropical greenhouse and take samples back to his lab.
“I had never had a request like this before; it made me look at plant material in a different way,” Wirth said. “I think it’s a fantastic way of using these pieces of living tissue, to grow human tissue.”
Olbrich plants that proved useful include vanilla, bamboo, wasabi, elephant ear, zebra plant and various orchids.
To use plants as scaffolds, the scientists strip away all of the cells, leaving husks of cellulose. Since human cells have no affinity for plants, they add peptides as biological fasteners.
“They’re like grappling hooks for the cells to attach to the plant,” Murphy said.
To determine if plant scaffolds could really replace those made of plastic or rubber, the researchers hope to test the cellulose models in animal studies this year.
A major goal of tissue engineering is to develop implants that could regenerate tissue in people — to repair bone or muscle damage after traumatic injuries, for example.
It is likely the human body wouldn’t reject tissue implants formed on plant scaffolds because the plant cells would be removed, Murphy said.
“We’re crossing kingdoms,” he said. “But we’re optimistic that these materials would be well-tolerated.”