Biomaterial-associated molecular patterns (BAMPs) modulate macrophage polarization in bone grafting

Bone graft rejection in oral surgery remains a significant challenge, potentially compromising the success of reconstructive procedures. Biomaterial-associated molecular patterns (BAMPs) play a pivotal role in bone graft integration and rejection by initiating and modulating immune responses during the foreign body reaction (FBR). This study evaluated BAMPs components, physicochemical properties, and adsorbed serum proteomic profiles in demineralized (DMB) and decellularized (DCC) bone grafts. The immunomodulatory effect of adsorbed serum proteins on DMB and DCC to modulate macrophage polarization was also investigated. Serum protein adsorption profiles were determined by incubating 0.5 g of DMB and DCC bone grafts in 10% FBS. Adsorbed serum proteins were buffer-desorbed, quantified, and subjected to proteomic analysis. The capacity of DMB and DCC adsorbed serum proteins to modulate functional and phenotypic profiles of macrophages was assessed using THP-1 cells. Macrophages were incubated for 72 hours with or without DMB- or DCC-adsorbed serum proteins, followed by expression analysis of CD14, CD16, CD86, CD206, HLA-DR, iNOS, Arg-1, IL-1β, TNF-α, IL-10, and TGF-β. Physicochemical analysis revealed that DCC bone grafts' surfaces were hydrophilic, anionic, and smooth, whereas DMB surfaces were hydrophobic, mildly anionic, and rough. The proteomic profiles of adsorbed serum proteins associated with DMB and DCC bone grafts showed significant variations. Macrophages exposed to DCC-adsorbed serum proteins exhibited an elongated cell morphology, increased expression of CD16 and CD206 (p < 0.0001), and higher Arg-1 expression. Conversely, the DMB group macrophages exhibited a rounded cell morphology, increased expression of CD86 and HLA-DR (p < 0.01), and higher iNOS expression. The DCC group showed higher mRNA levels of IL-10 and TGF-β (p < 0.0001). The physicochemical properties of bone grafts govern serum protein adsorption, which, in turn, directs macrophage polarization and graft acceptance. Understanding these interactions guides the design of immunomodulatory biomaterials to enhance graft integration.