Macrophage Polarization in Response to Collagen Scaffold Stiffness Is Dependent on Cross-Linking Agent Used To Modulate the Stiffness

Macrophages are the first responders to biomaterial implantation and determine the success or failure of an implant through their polarization into proinflammatory (M1) and anti-inflammatory (M2) states. It is known that material properties such as stiffness can influence this response, with these properties typically modulated using a cross-linking agent. However, the cellular response comparing different cross-linking agents is often not analyzed. In this study, collagen scaffolds were cross-linked with one physical (DHT) and two chemical cross-linking methods (EDAC and genipin) in order to independently modulate the stiffness of scaffolds. The physical and structural properties of the scaffolds were thoroughly characterized to ensure that macrophage behaviors toward scaffold stiffness and cross-linking agent employed could be evaluated independent of each other. Through gene expression and protein secretion analysis of THP1 cultures, we demonstrate that the macrophage response to collagen scaffold stif...