Biomaterials, fibrosis, and the use of drug delivery systems in future antifibrotic strategies.

All biomaterials, when implanted into the body, elicit an inflammatory response that evolves into fibrovascular tissue formation on and around the material. As a result, material scientists and tissue engineers should be concerned about host response to tissue-engineered constructs that have a biomaterial component, because the host response to this component will interfere with device function and reduce the lifespan of tissue engineering devices in vivo. The fibrotic response to biomaterials is not unlike pathological fibrosis of the liver, lung, kidney, and peritoneum in many ways: i) the presence of mononuclear leukocytes are common in the local environment of both pathological fibrosis and biomaterial-induced fibrosis even though cells of mesenchymal origin are responsible for laying the majority of the extracellular matrix; ii) paracrine-signaling molecules, such as transforming growth factor beta;1, are essential mediators of fibrosis, whether it is pathological or biomaterial induced; and iii) injury and/or the presence of foreign materials (including bacterial components, toxins, or man-made objects) are essential initiators for the development of the fibrotic response. This review discusses mechanisms and research methodology related to pathological fibrosis that is of interest to researchers focused on biomaterials. Potential research models for the study of fibrosis from the fields of biomaterials and drug delivery are also discussed, which may be of interest to scientists working on the pathology of fibrotic disease.