Sensing the Stiffness: Cellular Mechano-Sensing at the Implant Interface.

In this perspective, we highlight the relevance of the FA-Hippo signaling pathway and its regulation of the Yes-associated protein (YAP) and the transcriptional coactivator with a PDZ-binding domain (TAZ) as main players in the process of implants integration. The modulation and responses of YAP/TAZ triggered by substrate and ECM stiffness are of particular interest in the construction of materials used for medical implants. YAP/TAZ nuclear localization and activity respond to the substrate stiffness by several mechanisms that involve the canonical and non-canonical Hippo signaling and independently of the Hippo cascade. YAP/TAZ regulate the expression of genes involved in several mechanisms of relevance for implant integration such as the proliferation and differentiation of cell precursors and the immune response to the implant. The influence of substrate stiffness on the regulation of the immune response is not completely understood and the progress in this field can contribute to the designing of an adequate implant design. Though the use of nano-biomaterials has been proved to contribute to implant success, the relationship between grain size and stiffness of the material has not been explored in the biomedical field; filling these gaps in the knowledge of biomaterials will highly contribute to the design of biomaterials that could take advantage of the cells sensing and response to the stiffness at the implant interface.