Co-culture of bone marrow stem cells and macrophages indicates intermediate mechanism between local inflammation and innate immune system in diabetic periodontitis

Diabetic periodontitis (DP), which has been shown to cause alveolar bone loss, is among the most common complications associated with diabetes. The precise mechanisms underlying alveolar bone loss in patients with DP remain unclear. Therefore, the present study established a co-culture system of bone marrow stem cells (BMSCs) and macrophages, in order to investigate the potential mechanisms underlying DP-associated alveolar bone loss in vitro. In addition, Porphyromonas gingivalis (PG) periodontal infection and high glucose levels were used to induce DP in mice. The present study evaluated the protein expression levels of various chemokines and the migration of BMSCs and macrophages. The protein expression levels of extracellular signal-regulated kinase 1 and 2, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) were significantly increased in the BMSCs exposed to high glucose and PG, which may have been due to the activation of MAPK. In addition, DP induction in mice was associated with the release of chemokine (C-C motif) ligand 2 (CCL2) from BMSCs and the secretion of chemokine (C-C Motif) receptor 2 (CCR2) and tumor necrosis factor-α from macrophages, which was associated in turn with enhanced adhesion and chemotaxis of macrophages. The results of the present study suggested that DP led to the upregulation of CCL2 in the periodontal tissues and enhanced macrophage infiltration via the CCL2/CCR2 axis, which in turn promoted alveolar bone loss.