Defined Surface Physicochemical Cues Inhibit M1 Polarization of Human Macrophages Using Colloidal Self-Assembled Patterns

Biophysical and biochemical cues modulate mammalian cell behavior and phenotype simultaneously. Macrophages, indispensable cells in the innate immune system, respond to external threats such as bacterial infections and implanted devices, undergoing the classical M1 polarization to become a pro-inflammatory phenotype. In the study, lipopolysaccharide (LPS)-induced M1 polarization was examined using RAW264.7, THP-1, and primary human PBMCs on a family of artificial extracellular matrix (ECM), named colloidal self-assembled patterns (cSAPs). The results showed that cSAPs were biocompatible, which cannot induce M1 or M2 polarization. Interestingly, specific cSAPs (e.g., cSAP3) suppress the level of M1 polarization (i.e., reduced nitric oxide production, down-regulated gene expression of iNOS, IL-6, TNF-α, IL-1β, and TLR4, and reduced proportion of CD11b+CD86+ cells). Transcriptome analysis showed that cell adhesion and cell-ECM interaction participated in the M1 polarization, and the mechano-sensitive genes such as PIEZO1 were down-regulated on the cSAP3. More interestingly, these genes were also down-regulated under LPS stimulation, indicating that cells became insensitive to the LPS. The abovementioned results indicate that the defined physicochemical cues can govern macrophage polarization. This study illustrates a potential surface design at biointerface, which is critical in tissue engineering and materiobiology. The outcome is also inspiring in ECM-mediated immune responses.