Spatial confinement downsizes the inflammatory response of macrophages

Area of Science:

• Cellular mechanobiology
• Immunology
• Epigenetics

Background:

• Macrophages are crucial immune cells responding to diverse stimuli.
• Decoupling chemical and physical stimuli during macrophage activation in vivo is challenging.
• Spatial cues significantly influence cellular behavior and function.

Purpose of the Study:

• To investigate the impact of spatial confinement on macrophage pro-inflammatory activation.
• To elucidate the mechanotransduction pathways involved in regulating macrophage responses.
• To explore the potential of mechanical cues in modulating immune cell function.

Main Methods:

• Utilizing micropatterning, microporous substrates, and cell crowding to impose spatial confinement.
• Assessing lipopolysaccharide (LPS)-stimulated transcriptional programs.
• Analyzing chromatin compaction, epigenetic alterations (HDAC3, H3K36-dimethylation), and protein translocation (MRTF-A).
• Employing chromatin immunoprecipitation coupled with quantitative PCR and RNA sequencing.

Main Results:

• Spatial confinement suppressed late LPS-activated inflammatory gene expression (IL-6, CXCL9, IL-1β, iNOS).
• Confinement reduced actin polymerization, inhibiting MRTF-A nuclear translocation and downstream SRF activity.
• Early LPS-induced signaling (TLR4, NF-κB, IRF3) and gene expression were minimally affected.
• Pro-inflammatory cytokine secretion and phagocytic potential were downregulated by confinement.

Conclusions:

• Macrophage spreading, regulated by spatial confinement, is critical for late inflammatory gene expression.
• Mechanotransduction pathways involving actin polymerization and MRTF-A are key mediators of this suppression.
• Spatial confinement offers a novel strategy to modulate macrophage inflammatory responses, with implications for regenerative medicine.