A living tissue factory: printed cells to create everything from bone marrow to lab meat

Nature has perfected the art of creating living cells over billions of years. A team of researchers is now learning from that process and looking for ways to speed it up. For Massimo Vassalli, chair of bioengineering at the University of Glasgow, the goal is to understand not only how living tissues form, but how they can be recreated in the laboratory.

Vassalli is the scientific coordinator of PRISM-LT, a five-year project funded by the European Union that will run until 2027. The team is developing a 3D bioprinting platform to create complex living tissues, with applications ranging from biomedical research to cultivated meat.

The project’s central idea sounds almost futuristic: engineered living materials, or ELMs. These are composite materials, wholly or partly made of living cells—including microorganisms such as bacteria or fungi—that can grow, respond to, and adapt to their environment. ELMs can self-organize and self-repair in ways conventional static materials cannot.

“Engineered living materials can have additional, dynamic features that we simply cannot replicate with traditional static materials,” Vassalli said.

Building with living cells

ELMs could transform multiple sectors, from healthcare to food production, but turning that potential into reality requires solving a difficult biological problem: how to print living cells into complex structures without killing them or losing control over their development.

The PRISM-LT team tackles this problem by creating living tissues from tiny capsules that contain living cells and a gel-like support material known as “bioink.”

“Instead of printing a continuous stream of bioink, we work with modular living components that are encapsulated,” said Laura Martinelli, PRISM-LT project coordinator and executive director of In Society, a research organization based in Udine, Italy.

“These capsules can be placed precisely by a robotic arm or bioprinted layer by layer to create complex tissue architectures,” Martinelli said. Conventional methods print cells in a continuous flow of material, without the biological guidance microorganisms can provide. In this approach, each capsule is a biological unit that includes both the scaffold and the artificial microorganisms that help steer cells as they develop.

These microorganisms have been genetically modified to act as biological guides. They detect when stem cells—cells that can develop into many different tissue types—begin to differentiate and respond by releasing chemical signals known as “growth factors” that direct them toward the desired tissue type.

The manufacturing process is fast, taking from a few minutes to an hour. The next stage is slower: a maturation period of about three weeks during which stem cells become bone, fat or muscle tissue. The team can currently produce roughly one square centimeter of thin tissue and is working to achieve a one cubic centimeter block.

What makes this especially complicated is that the process requires placing living components that, by nature, are not meant to coexist in the same environment.

“We have to create a symbiotic relationship between two systems not designed to live together, like yeast and stem cells,” Vassalli explained. “The main challenge is to create conditions suitable enough for both the yeast or bacteria and the stem cells while the latter differentiate.”

This curiosity about biological interaction was the project’s starting point. “We began this research because we were curious about that interaction,” Vassalli said. “In essence, that is how evolution happened too. Single-celled organisms interacted and evolved into the natural world as we know it.”

From bone marrow to the dinner table

Researchers are working to recreate two specific types of tissue. One is the interface between bone and adipose tissue found in bone marrow for biomedical research. The other is muscle-and-fat structures that reproduce the fat marbling that gives natural meat its texture and flavor—a quality long impossible to achieve in cultivated or lab-grown meat.

The platform will also be used to create miniature tissue models that mimic the structure of human organs, which could be used in drug testing and contribute to personalized medicine.

“The project aims to create a platform that allows the design of different tissues for very different purposes, but using the same principles,” Martinelli said.

In health care, the goal is to create three-dimensional bone marrow models to study drugs aimed at treating diseases that affect it, such as leukemia.

For food, achieving the right distribution of adipose tissue is essential for consumer acceptance of the product. “Thanks to our bioprinting technology, we can achieve the right texture in alternative meats, which gives us the opportunity to commercialize them,” Martinelli said.

Bringing this technology to the public will take time. “We are still far from real-world applications,” she said. “We focus on principles and mechanisms to see what is viable. However, we are already considering future challenges.”

Consumer perception is one such challenge. When developing cultivated meat, researchers chose to work with yeast rather than bacteria. “It would be hard to explain to consumers that meat was made using bacteria,” Martinelli noted.

Beyond the lab: the regulatory frontier

Scientific progress is only part of the challenge. Introducing genetically modified living materials into medicine or food production will also require a new regulatory approach.

Because ELMs combine living cells and, in some cases, genetically modified microorganisms, they do not fit neatly into existing regulatory frameworks, which are designed for conventional medicines or standard food products—not for materials that, in a sense, are alive.

In collaboration with the European Innovation Council, the team is already in contact with regulatory authorities, including the European Medicines Agency, to study what rules and authorizations these materials might need in the future.

“We have to adopt a new attitude toward this technology,” Martinelli said. “This collaboration helps us pave the way for the use of ELMs.”

Vassalli adds that ELMs could be “extremely powerful” if applied widely. “When we launched the project, we asked two key questions: is it viable? and is it scalable? Now we can say it is viable.”

Scalability is the next challenge. If the team succeeds, it could be another step toward a future in which living materials sit alongside the conventional materials we already take for granted.

This article was originally published in Horizon, the EU’s research and innovation magazine.

The research presented in this article was partly funded by the European Innovation Council (EIC).

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