Significance: Macrophages are central regulators of the immune response during infection and wound healing, and their behavior is largely thought to be regulated by soluble factors in the microenvironment. Here, we find that adhesive cues are also critical for regulating the proinflammatory vs. prohealing state of these cells. We use engineered cell culture substrates to control cell shape and find that elongation of cells promotes a prohealing phenotype. Moreover, we identify key molecular pathways that are responsible for transducing physical cues to the biochemical cues that govern this response. Together, these studies suggest an important role for cell shape in regulating macrophage function.

Macrophages perform diverse functions within tissues during immune responses to pathogens and injury, but molecular mechanisms by which physical properties of the tissue regulate macrophage behavior are less well understood. Here, we examine the role of the mechanically activated cation channel Piezo1 in macrophage polarization and sensing of microenvironmental stiffness. We show that macrophages lacking Piezo1 exhibit reduced inflammation and enhanced wound healing responses. Additionally, macrophages expressing the transgenic Ca²⁺ reporter, Salsa6f, reveal that Ca²⁺ influx is dependent on Piezo1, modulated by soluble signals, and enhanced on stiff substrates. Furthermore, stiffness-dependent changes in macrophage function, both in vitro and in response to subcutaneous implantation of biomaterials in vivo, require Piezo1. Finally, we show that positive feedback between Piezo1 and actin drives macrophage activation. Together, our studies reveal that Piezo1 is a mechanosensor of stiffness in macrophages, and that its activity modulates polarization responses.

Macrophages sense biophysical cues in the microenvironment via YAP to tune their inflammatory response.