Bacterial Protein Enables 2D Culture of Organoids

Researchers from the Organoid group have developed a novel method for growing organoids—miniature lab-grown organs that resemble their real-life counterparts. Using a bacterial protein called Invasin, the team successfully created organoids in a sustainable, cost-effective, and animal-free manner. Their groundbreaking study, published in PNAS on December 30th, 2024, showcases the potential of Invasin as an alternative to current methods.

What Are Organoids?

Organoids are small, lab-grown structures that mimic the function and structure of real organs. Scientists use them to study organ behavior, disease development, and drug testing. To grow organoids, cells require an environment similar to the extracellular matrix found in the body—a network of proteins, such as collagen, that supports cells and tissues.

This environment acts like scaffolding in construction, providing cells the support they need to grow. Currently, researchers use basement membrane extracts like Matrigel and BME for this purpose. While effective, these extracts are expensive, their composition is variable, and they are derived from animals. This has led researchers to search for affordable, consistent, and animal-free alternatives.

In their search for alternatives, the researchers identified an unexpected candidate: a bacterial protein. Specifically, they focused on Yersinia, a bacterium found in the gut. Yersinia uses a protein called Invasin to adhere to human cells by binding to specific surface proteins. The team decided to repurpose this mechanism for organoid growth.

“We started to think out of the box and try something completely different,” said Joost Wijnakker, the study’s first author and a PhD student at the Hubrecht Institute.

The researchers isolated and purified a key fragment of the Invasin protein to test whether it could mimic the functions of proteins found in Matrigel and BME.

Growing Organoids with Invasin

The team coated culture dishes with the enhanced Invasin protein and found that it enabled organoid growth. The coating proved versatile.

“We were able to grow and maintain organoids long term from human intestinal and airway cells, mouse intestinal cells, and even snake venom gland cells,” Wijnakker explained.

The organoids retained their ability to differentiate into specialized cell types, closely resembling real organs in both structure and function. This resemblance is vital for studying organ development, regeneration, and drug responses.

Why 2D is the New 3D

Another advantage of the Invasin coating is its ability to grow organoids as flat 2D sheets rather than the traditional 3D gel-based structures. Growing organoids in 3D gels, like Matrigel or BME, can complicate analysis—akin to studying a blueberry trapped in jelly pudding.

The 2D Invasin coating simplifies this process. Cells grown in 2D are easier to culture and study, and the flat structure allows simultaneous testing of multiple drugs. Additionally, the 2D format preserves the natural order of the cells. For instance, intestinal cells maintain their polarity, with one side facing digestive contents for nutrient absorption and the other attached to the basement membrane. This architecture enables researchers to study both sides of the cell more effectively.

The use of Invasin to grow organoids has far-reaching implications.

“We believe that Invasin represents a fully defined, cheap, versatile, and animal-free alternative to Matrigel/BME,” Wijnakker stated.

This technology opens new possibilities for research and drug development, offering a more ethical and accessible approach. By replacing mouse-derived gels with bacterial proteins, the study highlights how even the smallest organisms, like bacteria, can lead to transformative advancements in medical science.