STKE Focus Issue on the Bionic Human: The Molecular Signaling of Tissue Repair

The prospect of replacing injured or diseased human cells, tissues, and organs with their normal counterparts lies at the evolving interface between two disciplines--biological science and applied engineering. The special issue in Science magazine on the Bionic Human ( and ) highlights current state-of-the-art technologies that are revolutionizing the development of prosthetic devices and engineered tissues, bringing this clinical goal ever so closer. This issue of the STKE expands on several of these topics, revealing why a fundamental understanding of cell signaling remains at the heart of many of these technological advances. Several Viewpoints in Science , including those of Hench and Polak ( ) and Griffith and Naughton ( ), point to why today's engineered biomaterials are designed to account for how various living tissues respond to the physiological loads or biochemical stimuli to which they are normally exposed. These newer materials interact with relevant cell surface proteins, such as integrins, to regulate normal cell proliferation, differentiation, and the production and organization of extracellular matrix. STKE's Perspective by Alenghat and Ingber ( ) describes how cells respond to mechanical stimulation, particularly sensory cells. Indeed, understanding sensory hair cell response to sound stimulation is integral to engineering auditory prothetics, as described in Science by Rauschecker and Shannon ( ). Engineering living tissue for implantation requires understanding how cells grow and differentiate in three dimensions. Hench and Polak raise the additional issue of how to get a blood supply to such implanted engineered tissue. The STKE Perspective by Stupack and Cheresh ( ) takes a deeper look at angiogenesis and how proangiogenic factors and remodeling of the extracellular environment by vascular endothelial cells contributes to this complex process. A Review on signaling by the proangiogenic factor vascular endothelial growth factor (VEGF) can also be found in the STKE Archive by Matsumoto and Claesson-Welsh ( ). One of the greatest clinical challenges is treatment of processes controlled by the central and peripheral nervous systems. Implantation of tailored biomaterials that sustain a controlled release of appropriate molecules that promote or inhibit neurite outgrowth may serve to stimulate nerve regeneration is the topic of the Science Viewpoint by Schwab ( ). STKE features a Review by He et al . ( ) describing axon guidance by Semaphorins. Articles in the STKE Archive, such as the Perspective about netrin signaling by Merz and Culotti ( ) and the Review on Ephrins and Eph Receptors by Boyd ( ) describe other players in controlling axon migration. Insight into processes and signaling mechanisms regulated by neurotrophins are highlighted in a Perspective on retrograde signaling by Segal ( ) and a Book Review by Roth ( ) from the STKE Archives. The regulation of synapse development is the focus of the Perspective on γ-amino butyric acid (GABA) in developing synapses by Kriegstein and Owens ( ). Finally, implanted biomaterials must have a minimal toxic response. Optimal implants are those that are inert and do not trigger an immune response. A Review in the STKE Archive by O'Neill ( ) describes some general aspects of host defense mediated by Toll-like receptors. Featured in This Focus Issue on the Bionic Human Related Resources at STKE