EU project prints living bone, fat, and muscle with engineered microbes

A different way to print living tissue

Most bioprinters lay cells down in a flowing bioink and hope they organize themselves. The EU backed PRISM-LT project takes the opposite route. Researchers package stem cells inside tiny capsules alongside engineered microbes that act as biological foremen. When the stem cells start to change, the microbes release growth factors that nudge them toward becoming bone, fat, or muscle.

"Rather than printing a continuous stream of bioink, we work with encapsulated living building blocks," said Laura Martinelli, CEO of InSociety and the project coordinator. A robotic arm can place the capsules with precision, or they can be printed layer by layer into more complex shapes.

Two markets, one platform

The team is chasing two very different goals from the same method. The first is the bone and fat interface found in bone marrow, which could give researchers better 3D models for testing drugs against diseases like leukaemia. The second is the muscle and fat structure that gives real meat its marbling, the part of cultivated meat that has resisted scale for years.

Fat distribution decides whether people accept lab grown meat, and Martinelli frames the work as a market unlock. The team deliberately chose yeast over bacteria as the guiding microbe, reasoning that meat grown with bacteria would be a harder sell at the dinner table.

The hard part is keeping everyone alive

These capsules force organisms together that never evolved to share a space. "The main challenge is to create conditions that are good enough for yeast or bacteria, as well as the stem cells while they differentiate," said researcher Vassalli.

The printing itself is fast, from minutes to about an hour. The tissue then needs roughly three weeks to mature. Right now the group can produce about one square centimetre of thin tissue, and they are working toward a one cubic centimetre block.

Regulators are already in the room

Because these engineered living materials combine living cells with genetically modified microorganisms, they fall outside the rules written for conventional medicines and standard foods. The team is working with the European Innovation Council and talking with the European Medicines Agency to map what approvals such materials might need.

Vassalli says the project has cleared its first hurdle. "We can now say that it is feasible," he said. Scalability is the next test, and the one that decides whether living materials eventually sit alongside the inert ones industry already relies on.