Decellularized Extracellular Matrix Scaffold Loaded with Regulatory T Cell-Conditioned Medium Induces M2 Macrophage Polarization.

Biomaterials often induce local inflammatory responses following implantation. Scaffolds that cause continuous M1 polarization typically hinder tissue healing and regeneration. Regulating the transformation of macrophages to the M2 phenotype in the inflammatory environment is crucial. We propose that regulatory T cell-conditioned medium (T(reg) CM) effectively promotes M2 polarization of macrophages induced by decellularized extracellular matrix (dECM) materials in inflammatory environments. In vitro results showed that in the presence of dECM, T(reg) CM induces the polarization of RAW264.7 macrophages to M2 and inhibits M1 macrophage polarization under inflammatory conditions (lipopolysaccharide + IFN-γ). Additionally, dECM promotes the polarization of bone marrow-derived macrophages (BMDMs) to M2, while T(reg) CM further promotes M2 polarization and inhibits M1 polarization in an inflammatory environment. These findings were confirmed by transcriptome sequencing. T(reg) CM inhibited IκB kinase/NF-κB signaling and cellular responses to oxidative stress. In vivo subcutaneous transplantation showed an increase in M2 macrophages, a decrease in M1 macrophages, and an increased M2/M1 ratio in dECM materials loaded with T(reg) CM. These results suggest that T(reg) CM can create a pro-M2 polarized microenvironment for dECM, guiding immune responses toward favorable tissue regeneration. Ultimately, this research highlights the potential of T(reg) CM as a therapeutic approach to modulate the immune response and improve the efficacy of regenerative biomaterials.