When Bone Behaves Like a Sponge: A New Platform for Observing How Cells Feel Force

Bone may look solid, but at the scale of the cells that live inside it, it behaves more like a sponge.

Every step, jump or stretch compresses bone’s porous structure, pushing fluid through microscopic channels and bathing embedded cells in a complex mix of mechanical strain and flowing liquid. For decades, mechanobiologists have known this environment exists, but they haven’t had a way to recreate it in the lab.

Now, Ottman Tertuliano, AMA Family Assistant Professor in Mechanical Engineering and Applied Mechanics, and his lab at Penn Engineering have built a platform that does exactly that. In a study published in Biophysical Journal and led by postdoctoral fellow Kailin Chen and graduate students Alexander Bolanos Campos and Mistica Lozano Perez, the team introduced a nanoengineered, 3D-printed scaffold that allows scientists to simultaneously control and observe solid deformation and fluid flow around living cells.

The Tertuliano Lab including [rear standing] Stephen Ching, Ottman Tertuliano, Luc Capaldi, [middle standing] Tianbai Wang, Mystica Lozano Perez, Cangyu Qu, Alexander Bolanos Campos, [front sitting ] Riti Sharma, Quan Vo and Elaine Chesoni. (Credit: Sylvia Zhang)

More than a single discovery, the work lays the groundwork for a new way of studying how cells sense and respond to the complex combination of solid and fluid forces. This scaffold could reshape research on bone, cartilage and other load-bearing tissues throughout the body and help us understand how millions of small, repeated forces, like those experienced in the knee during walking or running, accumulate to reshape individual cells inside load-bearing tissues. Research such as this might shed light on why some people maintain mobility over decades while others develop degenerative conditions.

“Understanding how individual cells respond to complex forces helps us bridge the gap between routine physiological activity like walking and the microscopic local changes those cells make to the tissue,” says Tertuliano, sharing why understanding force at the cellular level matters.

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