In a recent study published in Nature Physics, engineers at Brown University have investigated how human epithelial cells behave when grouped as spheroids within a collagen matrix. The research provides new insights into how cells collectively move and alter their environment during tissue formation.
The team created multicellular spheroids using the hanging droplet method, introducing about 500 human mammary epithelial cells into each droplet of culture media on an inverted Petri dish lid. After forming spherical aggregates, these cell clusters were embedded in a collagen material designed to mimic the body’s extracellular matrix. This setup allowed researchers to observe both cell movement and the forces they exert.
Jiwon Kim, postdoctoral researcher at Brown’s School of Engineering and lead author of the study, explained that “the spheroids are not perfectly circular to begin with, but slightly oval. Cells invade from these sharper ends, as if they have a memory of the original shape. The early shape already hints at where the invasion will happen later.”
Using confocal microscopy and fluorescent tagging, researchers tracked cellular motion and changes in the surrounding collagen matrix over time. Within five hours of embedding, the cell clusters began rotating collectively inside the matrix.
“It’s really striking to see,” said Ian Y. Wong, associate professor of engineering at Brown and corresponding author of the study. “These spheroids with hundreds of cells just start spinning around inside the collagen matrix.”
After approximately 12 hours, certain “leader” cells started moving outward from the main sphere, creating strands that pushed through the external collagen. Over time, these strands elongated and enabled further outward migration.
Hyuntae Jeong, another postdoctoral researcher involved in the project, noted: “We saw that the cells were pulling a little harder in places where the original culture was a little bit sharper, where it deviates a little from being spherical. One of the consequences of that pulling is that it starts to reshape the collagen that surrounds the cells, aligning the fibers radially and steering the cells outward.”
The team also demonstrated that altering osmotic pressure around these spheroids affected cell invasion patterns. Increased pressure halted or reversed invasion activity depending on when it was applied during development.
Researchers believe this work could advance understanding of tissue development and cancer metastasis by highlighting how physical environments influence cellular behavior.
“This is really an argument for understanding the cellular microenvironment,” Wong said. “Cells are getting instructions from each other, but also from their surroundings. And they’re able to reshape their surroundings in important ways. We think it’s worth looking more deeply into these interactions between cells and their surroundings.”
Co-authors include Carles Falcó (University of Oxford), Alex M. Hruska (Brown), W. Duncan Martinson (Francis Crick Institute), Alejandro Marzoratti (Brown), Mauricio Araiza (University of Wisconsin-Madison), Haiqian Yang (MIT), Vera C. Fonseca (Brown), Stephen A. Adam (Northwestern), Christian Franck (Wisconsin), José A. Carrillo (Oxford) and Ming Guo (MIT). The research received primary support from Brown University’s Hibbitt Engineering Fellowship, along with funding from the National Institutes of Health and U.S. Army Research Office.
