Small organs grown in the lab can be organized into complex shapes. But it’s difficult to use these so-called “organoids” to study diseases because you’ll never do the same thing twice in the same way.
Now, scientists at the University of California, San Francisco have created a new material that helps organoids grow in a more predictable way. They mixed microparticles of alginate, a complex carbohydrate derived from algae, into Matrigel, a standard gel used to grow organoids. This made the gel more similar to the soft but supportive environment inside the body, where tissues normally grow.
The team was also able to 3D print the stem cells into precise shapes in a Petri dish before they began to mature. Organoids developed better and more consistently. Improved growth conditions may one day be useful for producing tissue replacements.
“What we found to be most important is how the material relaxes over time, something called stress relaxation,” said Dr. Zev Gartner, professor of pharmaceutical chemistry at UCSF and lead author of the paper. natural materials “At the same pace that an organization reshapes itself, it must disintegrate.”
Scientists have long imagined using printers to place stem cells into balls or tubes. It’s like 3D printing, but applied to living tissue. It is already being used to create flat sheets of skin and collagen for reconstructive surgery. But with matrigel it doesn’t work.
“Liquid Matrigel is too viscous to print, and once solidified, it pushes back too much,” said lead author Dr. Austin Graham, a postdoctoral fellow in Gartner’s lab. “We wanted a material that would allow us to place cells precisely where we wanted them, while also allowing them to grow and organize themselves.”
The researchers looked at how tissues naturally develop in the embryo and push and pull on their surroundings as they grow. If the environment is too harsh, development will stall. Too much fluidity can throw development off track.
When alginate microparticles were mixed with liquid Matrigel, they created a wet, sand-like material that supported stem cells printed in lines or clumps. This allowed us to build a consistent shape and size into these cells. As the cells grew, the material’s grip loosened, allowing the organoids to expand and fold into a more natural shape.
The researchers tested the method using several organoid-forming tissues, including mouse intestinal cells, salivary gland cells, human blood vessel cells, and brain cells derived from human stem cells. The printed clusters grow into healthy organoids, often maturing by budding germination. The intestinal cells, printed with long lines, formed tubes capable of transporting fluids, much like the human intestine.
This method leverages the natural capabilities of cells, rather than building tissues one by one.
“We’re not making tissue like Lego,” Gartner said. “We put the cells where we need them and let their developmental program assemble the tissue. The goal is to get to the point where the organ starts building itself.”
sauce:
University of California, San Francisco
Reference magazines:
Graham, A.J. Others. (2026). Stress-relieving granular bioprinting materials enable the self-assembly of complex and uniform organoids. natural materials. DOI: 10.1038/s41563-026-02519-4. https://www.nature.com/articles/s41563-026-02519-4
