Alteration of immunomodulatory properties of locally applied gingival-derived mesenchymal stem cells by the oral inflammatory environment via Caspase-3/8 in periodontitis.

Objectives: To investigate whether gingival tissue-specific mesenchymal stem cells exhibit relevant phenotypic features in the periodontal inflammatory microenvironment.

Methods: In this study, periodontitis model mice were treated with N-GMSCs or I-GMSCs once per week for 8 weeks, and alveolar bone loss was assessed via micro-CT and hematoxylin and eosin (H&E) staining. Normal gingival tissue-specific mesenchymal stem cells (N-GMSCs) or inflammatory gingival tissue-specific mesenchymal stem cells (I-GMSCs) were isolated in vitro. Then, colony formation assays were performed to detect cell proliferation. Osteogenic and adipogenic differentiation assays were subsequently performed. Afterward, apoptosis was measured by Annexin-V staining and enzyme-linked immunosorbent assay (ELISA), and flow cytometry analysis was performed to analyze the cell cycle distribution and inflammatory cytokines. Polymerase chain reaction (PCR) and western blot (WB) analyses were also performed.

Results: In this study, periodontitis model mice treated with I-GMSCs presented greater alveolar bone loss than N-GSMC-treated control mice. Then, we isolated normal gingival tissue-specific mesenchymal stem cells (N-GMSCs) or inflammatory gingival tissue-specific mesenchymal stem cells (I-GMSCs) in vitro. We found that I-GMSCs inhibited osteoblast and adipocyte differentiation. Furthermore, I-GMSCs inhibited cell growth and induced apoptosis and cell cycle arrest. We also found that the inflammatory environment targeted Caspase 3 and Caspase 8 and positively regulated their protein expression. Furthermore, the knockdown of Caspase 3 and Caspase 8 inhibited the apoptosis of both N-GMSCs and I-GMSCs. Moreover, periodontitis in mice injected with siRNA-Caspase-3 or siRNA-Caspase-8 promoted the treatment of periodontitis. Furthermore, There was no significant difference in periodontitis in mice injected with GMSCs+PAC-1 or GMSCs +Gag-Caspase-8-VLP compared with control group.

Conclusions: The oral inflammatory environment inhibited GMSCs in the treatment of periodontitis via Caspase 3 and Caspase 8.