Simultaneous cell traction and growth measurements using light

Characterizing the effects of force fields generated by cells on proliferation, migration and differentiation processes is challenging due to limited availability of nondestructive imaging modalities. Here, we integrate a new real‐time traction stress imaging modality, Hilbert phase dynamometry (HPD), with spatial light interference microscopy (SLIM) for simultaneous monitoring of cell growth during differentiation processes. HPD uses holographic principles to extract displacement fields from chemically patterned fluorescent grid on deformable substrates. This is converted into forces by solving an elasticity inverse problem. Since HPD uses the epi‐fluorescence channel of an inverted microscope, cellular behavior can be concurrently studied in transmission with SLIM. We studied the differentiation of mesenchymal stem cells (MSCs) and found that cells undergoing osteogenesis and adipogenesis exerted larger and more dynamic stresses than their precursors, with MSCs developing the smallest forces and growth rates. Thus, we develop a powerful means to study mechanotransduction during dynamic processes where the matrix provides context to guide cells toward a physiological or pathological outcome. We have developed a nondestructive imaging modality that enables continuous monitoring of traction forces generated by cells and cell mass through the stem cell differentiation process. Traction force is measured by fluorescence imaging of chemically patterned adhesion proteins on deformable substrates and a fast computational technique, and is termed Hilbert phase dynamometry. Cell mass is measured using spatial light interference microscopy. We demonstrate that differentiating mesenchymal cells exert larger and more dynamic stresses than ones not programmed to differentiate. Similar trends were observed in terms of cell growth.