B10 Adoptive Transfer Ameliorates Inflammation and Bone Loss in Experimental Periodontitis Through Promoting Macrophage-Mediated Pro-Resolving Functions.

Immune cell-cell interaction plays a critical role in the regulation of inflammatory responses. IL-10-expressing regulatory B cells (B10) alleviate the periodontal inflammation and bone loss by secreting IL-10, which can stimulate pro-resolving macrophage differentiation. However, little is known about the dynamic B10-macrophage interaction and the specific B10-induced pro-resolving functions in vivo in periodontitis. This study aimed to determine the dynamic local infiltration of B10 and macrophages, and the B10-induced macrophage differentiation and functions in experimental periodontitis. B10 were adoptively transferred via tail vein injection in a mouse model of experimental periodontitis. In some experiments, macrophages were depleted by intraperitoneal injection of clodronate liposomes. Dynamic gingival infiltration of B10 and macrophages were evaluated by in vivo imaging system (IVIS). The level of bone loss was evaluated by Micro-CT and TRAP staining. Cytokine productions, macrophage efferocytosis and autophagy were assessed by immunohistochemical / immunofluorescence analysis. Production of specialized pro-resolving mediators (SPMs) was detected by LC-MS/MS. B10 adoptive transfer inhibited alveolar bone resorption and osteoclast differentiation. B10 adoptive transfer promoted the number of pro-resolving macrophages compared with the control groups. A significant increase in IL-10, Arg-1, and YM-1, ATG5⁺, LC3B⁺, CD68⁺LC3B⁺, CD68+ATG5+ and CD68⁺Ly6G⁺ cells were detected in gingival tissues following B10 transfer, accompanied by a marked decrease in IL-17 A, TNF-α, and IL-1β expression. However, the B10-mediated suppression of alveolar bone resorption, osteoclast differentiation, TNF-α and IL-1β expression, as well as the upregulation of IL-10, ATG5, and LC3B, was attenuated upon macrophage depletion, whereas IL-17 A expression remained suppressed regardless of the macrophage presence. Notably, B10 adoptive transfer promoted RvD2 release in a macrophage-dependent manner. This study suggested that B10 adoptive transfer inhibited inflammation and bone loss in experimental periodontitis through the induction of macrophage-mediated pro-resolving functions, including RvD2 production, enhanced neutrophil clearance, and induction of macrophage autophagy.