Manipulation of Macrophages to Enhance Bone Repair and Regeneration

Abstract

Bone is a unique tissue in that it has the ability to heal itself perfectly, without scarring, under certain conditions. Therapeutic strategies that harness its powerful repair processes have the potential to successfully regenerate bone tissue in large defects, which remain a significant clinical challenge. However, despite the demonstrated importance of the inflammatory response in dictating the success or failure of implanted biomaterials, it is not often considered as an important criterion in the design of tissue engineering scaffolds. This chapter first highlights the role of macrophages in orchestrating the delicate balance between bone formation and resorption. Then, the main strategies that have been explored to actively control the inflammatory response are discussed, including delivery of mesenchymal stem cells, controlled release of immunomodulatory cytokines, and topographical modification of biomaterial scaffolds. Increased understanding of macrophage phenotypes (M1, various M2's, osteoclasts, etc.) will allow us to design therapeutic strategies that tip the balance toward healthy bone regeneration and away from pathologic bone loss.