TNF and periodontitis: Concomitantly, in a study by Li et al. [80], EPO hydrogel, through suppression of ROS levels, successfully shifted macrophage polarization from M1 to M2 enhancing tissue regeneration in periodontitis where M1 macrophage markers (IL-1β, IL-6, and TNF-α) were down-regulated while M2 macrophage markers (IL-10, Arg-1, and TGF-β) were upregulated.