Fibrous nonlinear elasticity enables positive mechanical feedback between cells and ECMs

Abstract

In native states, animal cells of many types are supported by a fibrous network that forms the main structural component of the ECM. Mechanical interactions between cells and the 3D ECM critically regulate cell function, including growth and migration. However, the physical mechanism that governs the cell interaction with fibrous 3D ECM is still not known. In this article, we present single-cell traction force measurements using breast tumor cells embedded within 3D collagen matrices. We recreate the breast tumor mechanical environment by controlling the microstructure and density of type I collagen matrices. Our results reveal a positive mechanical feedback loop: cells pulling on collagen locally align and stiffen the matrix, and stiffer matrices, in return, promote greater cell force generation and a stiffer cell body. Furthermore, cell force transmission distance increases with the degree of strain-induced fiber alignment and stiffening of the collagen matrices. These findings highlight the importance of the nonlinear elasticity of fibrous matrices in regulating cell-ECM interactions within a 3D context, and the cell force regulation principle that we uncover may contribute to the rapid mechanical tissue stiffening occurring in many diseases, including cancer and fibrosis.cell traction force | 3D cell traction force microscopy | fibrous nonlinear elasticity | cell-ECM interaction | collagen A nimal cells of most cell types, including breast tumor cells, are supported structurally by a fibrous ECM within a 3D context (1, 2). Cells adhere to the fibers via the linkages between integrin receptors on the membrane surface and the adhesion molecules within the ECM. To migrate, cells pull/push along the fibers or squeeze through the pore structure of the network (3). The tensional balance between the cell and the ECM critically regulates many physiological and pathological processes, including immune response, tissue formation, and tumor progression (4-7). In the breast tumor, stiffening of the mechanical environment disrupts force balance between epithelial cells and the ECM, promoting a malignant phenotype (5, 8). Tumors stiffen as cells deposit more collagen than they digest (9-11), increasingly express cross-linking enzymes (8, 12), and exert traction forces to reorganize the ECM (13).The main structural component of the ECM is a network of cross-linked protein fibers. The fiber network aligns, stiffens, and sometimes, undergoes permanent changes when subjected to strain (14, 15). These adaptive mechanical properties of the fiber network provide cells entry points to modify their local microenvironment (16-18) and as such, perform physiologically realistic functions (1,3,(19)(20)(21)(22)(23). It has been reported that the nonlinear elasticity of fibrous matrices enables cells to transmit forces over distances of hundreds of micrometers, facilitating long-range communication between individual cells (24-26) and between tumor spheroids (27). Recent work has shown that individual cells are capable of stiffening the...

Decoupling the effects of stiffness and fiber density on cellular behaviors via an interpenetrating network of gelatin-methacrylate and collagen

“…As previous studies have shown that cells are influenced by the presence of fibers [50], a second major goal of this research was to develop a material where fiber density could be manipulated. Fibers not only provide biological cues to embedded cells, but also act as a source of non-linear elasticity within the scaffold, with the capacity to uniquely influence cell-cell communication and alignment [51], as well as the degree of cell contraction [52]. Collagen-mimetic peptides that reproduce a portion of the native collagen triple helix have been incorporated into synthetic scaffolds [53, 54], but these peptides cannot organize to form a fibrillar structure.…”

Modeling the two-way feedback between contractility and matrix realignment reveals a nonlinear mode of cancer cell invasion

“…For example, by decreasing the gelation temperature, the matrix critical strain (« cr ) decreases (40)(41)(42). Also, at certain gelation temperatures (for example, 37°C), increasing collagen concentration increases the critical strain (« cr ) (41,43). Therefore, we can use our model to predict the shape of the cells, at different levels of « cr and n. As shown in Fig.…”

Microfluidic modeling of the biophysical microenvironment in tumor cell invasion

“…This is not surprising because tumor and stromal cells are known to actively pull onto the ECM, and thereby remodel the ECM architecture 66, 77, 78 . Collagen bundles have been reported to align perpendicularly to the tumor periphery, possibly by active tumor and stromal cell contraction, facilitate collective tumor cell invasion and correlate with malignancy 79, 80 .…”