Human Macrophage Polarization Dynamics on a 3D Fibrous Polydioxanone Mesh In Vitro

The host immune response plays a central role in determining biomaterial performance, particularly through early macrophage activation dynamics at the tissue-biomaterial interface. This study evaluated the response of THP-1-derived human macrophages cultured on a fibrous extracellular matrix-like polydioxanone (PDO) mesh under basal (M0), M1-induced, and M2-induced in vitro conditions. Macrophage responses were assessed by gene expression analysis, immunofluorescence staining of macrophage- and polarization-associated markers, scanning electron microscopy (SEM), and metabolic and viability assays. Distinct stimulus- and time-dependent responses were observed across transcriptional, marker distribution, morphological, and metabolic readouts. Pro-inflammatory gene expression increased under M1-polarizing conditions at 72 h and declined at 96 h, whereas anti-inflammatory and M2-associated markers progressively increased under M2 stimulation, reaching higher levels at 96 h. Immunofluorescence confirmed macrophage differentiation under basal conditions and showed condition-dependent distributions of CD86- and CD206-associated signals, consistent with the transcriptional profiles. SEM revealed stable cell-material interactions and polarization-associated morphological heterogeneity. Metabolic and viability assays confirmed viable cells under all conditions, with activity patterns consistent with induced activation states. Under basal (M0) conditions, macrophages cultured on the PDO mesh maintained a basal phenotype without evidence of marked pro-inflammatory activation. Overall, these findings indicate that fibrous PDO meshes support macrophage viability, differentiation, and stimulus-responsive activation, highlighting their potential as immunologically compatible polymeric platforms for regenerative biomaterial applications.