Gingival mesenchymal stem cells attenuate pro-inflammatory macrophages stimulated with oxidized low-density lipoprotein and modulate lipid metabolism

Objective: To examine the effects of gingival mesenchymal stem cells (GMSCs) on inflammatory macrophages upon oxidized low-density lipoprotein (ox-LDL) stimulation and evaluate therapeutic potential of GMSCs on mouse model of periodontitis associated with hyperlipidemia.

Methods: in vitro, GMSCs were co-cultured with macrophages for 48 h in the absence or presence of M1 polarizing conditions and oxidized low-density lipoprotein in the transwell system. The supernatants were collected for ELISA. M1 and M2 markers of macrophages were analyzed by flow cytometry and PCR, and lipid accumulation was assessed by oil red O staining. in vivo, eighteen mice were divided into three groups (n = 6): Group A (periodontally healthy mice as control), Group B (periodontitis mice with hyperlipidemia), Group C (periodontitis mice with hyperlipidemia with the transplantation of GMSCs). The serum levels of Cholesterol and inflammatory factors were measured by automatic analyzer. Bone regeneration was evaluated by Masson staining.

Results: When co-cultured with GMSCs, the M1 markers of Tumor Necrosis Factor (TNF) -α, Interleukin (IL) -6, Interleukin (IL) -1β, CD86, and Human Leukocyte Antigen (HLA) -DR were significantly reduced. In contrast, M2 markers such as Interleukin(IL) -10 and CD206 were moderately increased. Similar results were obtained in the Cell Culture supernatants. In animal experiment, GMSCs suppressed the expression of sterol regulatory element binding transcription factor 1c (SREBP-1c) and elevated the levels of Peroxisome Proliferator-activated Receptor alpha (PPARα) and peroxisome proliferator activator receptor- coactivator 1(PGC-1α) in the liver, attenuated Cholesterol dysfunction via the downregulation of low-density lipoprotein (LDL) and total Cholesterol (TC), and the upregulation of high-density lipoprotein (HDL), and decreased the levels of TNF-α and IL-6. Moreover, GMSC treatment improved bone regeneration.

Conclusion: GMSCs inhibit the activation of M1 macrophages, regulate lipid metabolism and reduce inflammatory response, and promote bone regeneration in mouse model of periodontitis associated with hyperlipidemia.