Bone engineering: combining smart biomaterials and the application of stem cells

Remarkable preclinical progress and achievements in the isolation and characterization of stem cells from different sources have been made, together with the ability to control proliferation and differentiation in vitro. Researchers and physicians pin their hope on stem cells to develop novel approaches in regenerative medicine. Stem cell therapy is no longer a scientific discipline in the laboratory or in animal models only, as it is already performed routinely in the human therapeutical and clinical treatment for hematological malignancies and clinical trials for bone repair. It has further been recognized that angiogenesis plays a pivotal role for the successful transplantation of in vitro engineered tissues like bone structures, for the repair of large bone defects to facilitate engraftment. We intended to generate transplantable composite grafts, which consist of in vitro generated bone tissue from multipotent adult progenitor cells, maintaining an angiogenic potential to ease and optimize a successful engraftment of long-term sustainable and viable bone tissue. The other component was generated from several synthetically produced three-dimensional tissues like fibrin, thrombin, collagen, hydroxyapatite, and beta-tricalciumphosphate in different compositions and concentrations, all mimicking natural body structures of bone tissue as biocompatible grafts. We established an in vitro mouse model, using bone marrow and peripheral blood-derived murine progenitor cells as well as industrially manufactured materials generating composite grafts. Based on our preliminary results, we propose to pursue research on composite grafts for an extended graft survival and successful engraftment of transplanted tissue.