Protein-mediated macrophage adhesion and activation on biomaterials: a model for modulating cell behavior

The elucidation of proteins involved in biomaterial-modulated macrophage behavior is critical for the improvement of material performance and the initial exploration of material design capable of manipulating macrophage function for tissue engineering. In this paper, several in vitro and in vivo techniques are presented to demonstrate means of delineating a part of the complex molecular mechanisms involved in the interaction between biomaterial and macrophage adhesion and phenotypic development. The following conclusions were reached: (1) using radioimmunoassay, complement component C3 was found to be critical in mediating human macrophage adhesion on polyurethanes. (2) The presence of a diphenolic antioxidant additive in polyurethanes increased the propensity for complement upregulation but did not affect adherent macrophage density. (3) The subcutaneous cage-implant system was utilized to delineate interleukin-4 participation in the fusion of adherent macrophages to form foreign body giant cells in vivo in mice. The injection of purified interleukin-4 neutralizing antibody into the implanted cages significantly decreased the giant cell density; conversely, the giant cell density was significantly increased by the injection of recombinant interleukin-4 when compared with the controls. (4) The RGD and PHSRN amino acid sequences of the central cell binding domain and the PRRARV sequence of the C-terminal heparin binding domain of human plasma fibronectin were utilized to study the structure-functional relationship of protein in mediating macrophage behavior. Polyethyleneglycol-based networks grafted with the RGD-containing peptide supported higher adherent human macrophage density than surfaces grafted with other peptides. The formation of foreign body giant cell was highly dependent on the relative orientation between PHSRN and RGD domains located in a single peptide.