Conditioned Medium Derived From Human Dental Follicle Mesenchymal Stem Cells Alleviates Macrophage Proinflammatory Responses Through MAPK‐ERK‐EGR1 Axis

The regulation of macrophage polarization by mesenchymal stem cells (MSCs) is a prominent area of research but faces challenges due to limited MSC sources and incomplete understanding of underlying mechanisms. We sought to identify an accessible MSC source and investigate how MSCs regulate macrophage polarization using high‐throughput sequencing. We isolated dental follicle MSCs from discarded human third molar dental follicles and cocultured them with THP‐1‐derived macrophages in the conditioned medium. Transcriptome sequencing identified differentially expressed genes (DEGs) in macrophages, integrating with multiomics database analysis to uncover polarization mechanisms. Our findings demonstrated successful MSC extraction from dental follicles, with the conditioned medium suppressing proinflammatory macrophage functions and influencing macrophage subtyping. MSCs, through paracrine signaling, activated the mitogen‐activated protein kinase (MAPK) pathway, leading to extracellular regulated protein kinases (ERK)1/2 phosphorylation and upregulation of early growth response 1 (EGR1) protein. Elevated EGR1 levels inhibited inflammatory gene expression, inhibiting the pro‐inflammatory immunoregulatory function of macrophages in inflammatory states. This study provides an efficient method for in vitro macrophage polarization identification. It offers insights into MSC‐regulated polarization mechanisms, with potential clinical implications for anti‐inflammatory therapy and immune regulation.