Macrophage reprogramming: influence of latex beads with various functional groups on macrophage phenotype and phagocytic uptake in vitro.

Macrophages play a crucial role in initiating immune responses with various functions ranging from wound healing to antimicrobial actions. The type of biomaterial is suggested to influence macrophage phenotype. Here, we show that exposing M1- and M2-activated macrophages to polystyrene latex beads bearing different functional groups can alter secretion profiles, providing a possible method for altering the course of the host response. Macrophages were stimulated with either lipopolysaccharide or interleukin (IL) 4 and cultured for 24 h with 10 different latex beads. Proinflammatory cytokines (tumor necrosis factor α, monocyte chemotactic protein 1) and nitrite served as markers for the M1 phenotype and proangiogenic cytokine (IL-10) and arginase activity for M2 cells. The ability of the macrophages to phagocytize Escherichia coli particles and water contact angles of the polymers were also assessed. Different patterns of cytokine expression and phagocytosis activity were induced by the various particles. Particles did not polarize the cells toward one specific phenotype versus another, but rather induced changes in both pro- and anti-inflammatory markers. Our results suggest a dependence of pro- and anti-inflammatory cytokines and phagocytic activities on material type and cytokine stimuli. These data also illustrate how biomaterials can be exploited to alter host responses for drug delivery and tissue engineering applications.