Macrophage polarization: An opportunity for improved outcomes in biomaterials and regenerative medicine

Abstract

The host response to biomaterials has been studied for decades. Largely, the interaction of host immune cells, macrophages in particular, with implanted materials has been considered to be a precursor to granulation tissue formation, the classic foreign body reaction, and eventual encapsulation with associated negative impacts upon device functionality. However, more recently, it has been shown that macrophages, depending upon context dependent polarization profiles, are capable of affecting both detrimental and beneficial outcomes in a number of disease processes and in tissue remodeling following injury. Herein, the diverse roles played by macrophages in these processes are discussed in addition to the potential manipulation of macrophage effector mechanisms as a strategy for promoting site-appropriate and constructive tissue remodeling as opposed to deleterious persistent inflammation and scar tissue formation.

Restoring Mucosal Barrier Function and Modifying Macrophage Phenotype with an Extracellular Matrix Hydrogel: Potential Therapy for Ulcerative Colitis

“…Regulatory M2-like macrophages have been associated with mucosal healing outcomes [21,22] in preclinical models of IBD. Similarly, the restoration of functional tissues via ECM bioscaffold mediated events in a variety of regenerative medicine applications has been shown to be either associated with, or dependent upon a timely shift in macrophage phenotype toward M2 predominance [23,24,25].…”

Titanium-Enriched Hydroxyapatite–Gelatin Scaffolds with Osteogenically Differentiated Progenitor Cell Aggregates for Calvaria Bone Regeneration

“…Despite these facts, we believe that it would be beneficial to assess the M1/M2 host response in future studies particularly when using allogeneic (nonautologous) MAPC transplants. 48,49 The immune rejection mechanism can start between day 3 and day 8 after implantation of allogeneic stem cells. 45 In our previous studies, we found no rejection-associated tissue necrosis or mixed lymphocytic reaction 10 days after implantation of OD-MAPCs.…”

Valence State Manipulation of Cerium Oxide Nanoparticles on a Titanium Surface for Modulating Cell Fate and Bone Formation

“…In response to various tissue microenvironmental cues, highly plastic macrophages can alter their phenotypes and functions to display the classically activated proinflammatory M1 and alternatively activated antiinflammatory M2 forms 9. The prohealing M2‐polarized macrophage phenotype can elicit positive outcomes on osteogenesis, angiogenesis, and osseointegration,[[qv: 8a,10]] and macrophage polarization can be modulated by the surface physics and chemistry cues of bone biomaterials.…”