Peristalsis-Induced Mechanical Activation of Macrophages.

Inflammation is a complex process that drives both acute and chronic diseases. It is modulated by cascading biochemical and biophysical cues that result in immune cell activation. Macrophages are a primary immune cell type that are involved in multiple inflammatory conditions, including cancer, fibrosis, and autoimmune diseases. Traditional methods of investigating macrophage activation involve biochemical stimulation with defined cytokine or chemokine cues, activating macrophages into the edges of a pro- or anti-inflammatory state. Emerging evidence suggests that biophysical cues also play a role in macrophage activation, in addition to the biochemical cues within tissues. One such prevalent mechanical cue is peristalsis, consisting of multiaxial strain and shear stress, occurring in the gastrointestinal tract, uterus, developing airways, and ureters. Here, we tested the hypothesis that peristalsis may activate macrophages. In this protocol, the use of a peristaltic bioreactor is described to investigate the mechanical activation of macrophages. Polydimethyl siloxane membranes were coated with fibronectin to enhance macrophage adhesion. Immortalized murine bone marrow derived macrophages (iBMDM) were seeded onto fibronectin-coated membranes and maintained as static controls or exposed to peristalsis for 4 h. Peristalsis activated the macrophages, with significant differences in the gene expression of Il6 (50.9 fold over static controls; p < 0.0001, t-test) and Nos2 (19.8 fold over static controls; p = 0.0046). Interestingly, no significant changes were observed in Chil3 (1.22 fold over static controls; p = 0.9726) or Mrc1 (1.16 fold over static controls; p = 0.9810) compared to static controls, indicating that mechanics primarily drove proinflammatory activation. The current findings support the concept of mechano-immunomodulation of macrophages, especially in response to peristalsis mechanics that are prevalent across many smooth-muscle-based tissues.