Evaluation of material mechanical properties influence on single cell mechanics

Abstract Mechanobiology research has shown that mechanical signals influence a wide spectrum of cellular events, including cell proliferation, differentiation, gene expression, protein production and their alterations. The objective of this projects is to elucidate the role of two mechanical factors, matrix stiffness and externally applied forces, in the organization and contractile activity of the cytoskeleton and distribution of intracellular forces. Indeed, localized concentration of cytoskeletal tensions at focal adhesions, the structures that link cells to their surrounding extracellular matrix, is the major mediator of mechanical signaling. Therefore, in the first phase of project we have studied how matrix stiffness in coordination with surface functionalization can regulate shape and the structural organization of integrated system constituted by actin network and integrin-mediated adhesion of fibroblasts. Then, we have investigated if there is a direct correlation between ECM stiffness and intracellular mechanics, measuring mechanical properties by particle tracking technique. A mechanical model has been developed to support experimental results and explain the relation that exists between matrix rigidity, focal adhesion sites dimension, cytoskeleton structure and intracellular mechanics. In the second part of project, we have focused attention on how integration of externally applied mechanical forces from focal adhesions over the entire cell body affects fibroblast responses to its mechanical environments both in 2D and in 3D matrix. In conclusion, we have observed that both matrix stiffness and external mechanical stress represent important stimuli to enhance cell stiffness and contractility of fibroblasts through cytoskeleton structuration, indicating that mechanics plays a critical role in cell biology. This consideration provides a solid foundation and rationale for use of mechanics to improve human health by designing appropriate equipment/instruments, exercise protocols, and rehabilitation regimens.