Transplantation of Macrophages Pretreated With Gingival Mesenchymal Stem Cell Conditioned Medium as a Potential Cell Therapy for Promoting Periodontal Tissue Regeneration in Rats With Experimental Periodontitis

Periodontitis is caused by the interaction between dental plaque and various risk factors, leading to the pathological loss of periodontal tissues. However, the traditional methods for periodontitis treatment is insufficient for controlling inflammation and promoting periodontal tissue regeneration. The current study attempts to investigate if M2 macrophages can contribute to inflammation control and periodontal tissue regeneration by transplanting macrophages pretreated with gingival mesenchymal stem cell conditioned medium (GMSCs-CM) into periodontal defects of rats with experimental periodontitis. GMSCs-CM were acquired from the culture medium of GMSCs and concentrated. The Dulbecco's Modified Eagle Medium (DMEM) was also concentrated as control conditioned medium(C-CM). In vitro, macrophages induced from THP-1 were treated by C-CM and GMSCs-CM. Total RNA was extracted for real-time quantitative polymerase chain reaction (qRT-PCR) analysis to assess the mRNA expression of Arg-1, CD206, IL-10, TNF-α and IL-6. In vivo, 40 periodontal tissue defects were created around the first molar of rats with experimental periodontitis and received one of the 4 treatments:PBS, C-CM treated macrophages, nontreated macrophages and GMSCs-CM treated macrophages. Paraffin slices were procedured for HE staining, modified Masson staining and immunohistochemical staining of TNF-α, IL-6, IL-10, CD163 and iNOS. Our findings revealed that significant upregulation of IL-10 and CD206 mRNA expression, along with downregulation of TNF-α and IL-6 in GMSCs-CM in vitro treated macrophages. In rats, the height of newly formed alveolar bone in GMSCs-CM treated group was significantly greater than those in the other three groups. In GMSCs-CM treated group, the immunohistochemical expression of CD163 and iNOS was significantly increased while IL-6 and TNF-α were significantly decreased. However, IL-10 was significantly most expressed in nontreated macrophages group. These results support our hypothesis that the transplantation of GMSCs-CM treated macrophages has the potential to facilitate periodontal tissue regeneration through their effectively managing local inflammation.