It’s been more than a decade since the first lab-grown organ (a more-or-less functional replacement bladder) was successfully implanted into a human body. But in the time since tens of thousands of people have been added to the organ donor waiting list in America alone.
Scientists are still figuring out how to grow organs at a scale — and price — that can meet the needs of thousands of patients a year. One of the big challenges to creating new organs in the lab is simply growing them: human cells require a very specific environment to shape themselves into functioning tissues.
Now, a team of researchers at the University of Massachusetts Lowell points out that human cells can grow on on a variety of scaffolds made of materials from everyday life. Think eggshells, paper, spinach leaves and more.
“We are talking about very common materials that we see in nature or we use in everyday life,” says Gulden Camci-Unal, an assistant professor of chemical engineering at the University of Massachusetts Lowell. “I think that, perhaps, simple things are often overlooked.”
To help highlight the many options out there, Camci-Unal and her colleagues compiled a list of some of the more unconventional methods scientists have used to grow human tissues, published today in the journal Trends in Biotechnology.
Organs From Ice and More
When scientists grow organs they first need a molecular-scale scaffold, almost like a very intricate mold, that guides a tissue culture as it’s grown into a medically useful 3D structure. These are often synthetic, but, Camci-Unal found, they don’t necessarily have to be.
In Australia, researchers at the University of Sydney worked with a 3D-printer capable of making ice into scaffolds that could be used to grow common cardiovascular replacements, like artificial aortic arches, or thin-walled and thick-walled arteries. One project that Camci-Unal found especially interesting, by a team based in China, used tofu to produce a more porous scaffolding that let a wound or skin laceration better breathe as the artificial tissue helped it heal.
The tofu-based scaffolding shared something with her own team’s research, which used eggshells to create a calcium carbonate-rich scaffolding better suited to guiding the work of osteoblasts: cells that produce the matrix of materials needed to regenerate bone. Even after they were prepared in the lab, both the tofu- and egg shell-based scaffolds still had remnant protein material on their surface that helped to guide the tissue cells as they took shape.
“If you include protein functional groups in your materials,” Camci-Unal said, “it’s very likely that it’s going to interact with cells better compared to a completely synthetic material.”
The current synthetic cell-culture scaffolds require complex fabrication steps and specialized hardware. And they can still cause problems. Artificial cell scaffolds can be less flexible than the tissues they are helping to replace. or conversely may not have the mechanical strength to retain their shape as the tissue grows. They may also simply be too expensive to manufacture at the scale the public needs.
Organs of the Future
But, as Camci-Unal found, Mother Nature may have already provided us with the materials we need to grow fully functioning organs. She and her coauthors describe how one group washed the plant cells out of spinach leaves, and grew cardiac tissue in the plant wall matrix left behind. Others have tried adapting marine sponges, paper, textiles, the apple pomace left behind after making cider and that ever-adaptable staple crop, soy.
Buddy Ratner, who directs the Engineered Biomaterials research center at the University of Washington, sees a lot of potential in this kind of tissue engineering, even though it has yet to yield any breakout applications in the day-to-day practice of medicine.
“It’s quite legitimate,” Ratner says. “[But] bigger issues are what do spinach and tofu bring to the table (pardon the pun) for tissue engineering?” Some biologically derived materials, have already been well-explored, he says, like chitosan scaffolds from shrimp shells, and alginate from seaweed.
“They start out as ‘cheap materials’ — when fully processed how expensive will they be?”
Finding cheaper materials was actually one of the researcher’s goals. They hoped to better understand what has already been explored in the hopes of finding materials that will lower the financial and environmental costs of this research. While much more work lies ahead to see if any of these materials truly suits scientists’ needs, natural options would ultimately make lab-grown organs more accessible to everyone.
“We do this because we want to help patients, right?” Camci-Unal says. “There are a lot of unmet clinical needs, and there’s a lot of room for the development of new functional materials to repair and regenerate tissue.”