Nucleotide-binding oligomerization domain 2 (NOD2), which is constitutively expressed in human pulp fibroblasts, plays a role in pulpal immune responses by sensing muramyl dipeptide (MDP) from bacteria, which leads to pulpitis. Matrix metalloproteinase-3 (MMP-3), which exhibits broad substrate specificity to the extracellular matrix (ECM) and induces angiogenesis and fibroblast wound healing, is expressed when pulp is inflamed. In the present study, we examined MDP/NOD2-induced MMP-3 production and the role of its signaling cascade involving TAK1/MAP kinase in human deciduous dental pulp fibroblast-like cells (hDDPFs). MDP did not affect the proliferation or viability of hDDPFs. The MAP kinase signaling pathway was involved in the production of MMP-3 in MDP-stimulated hDDPFs. The MDP stimulation enhanced ERK 1/2 phosphorylation, but did not affect the degradation of IκB. These results suggest that the production of MMP-3 in MDP-stimulated hDDPFs stimulated the degradation of surrounding collagen, leading to alterations in the structure of the ECM and inflammation, and appeared to promote angiogenesis.

The purpose of this study was to find novel factors that promote bone formation by the stem cells in vitro. The systemic administration of an immunosuppressive agent is expected to promote bone formation by stem cells. It was hypothesized that mizoribine (MZR) can increase mesenchymal stem cells for bone formation. Rat bone marrow cells (rBMCs) from the femur were used in this study. To obtain MZR-affected rBMCs (MZR-rBMCs), rats were injected with the agent subcutaneously. Dexamethasone (Dex), β-glycerophosphate (β-GP), ascorbic acid (Vc) and different amounts of MZR were added in culture medium for the subculture of MZR-rBMCs and normal rBMCs. The effects of MZR were evaluated by comparing the Ca²⁺ quantity from calcified nodules formed in the subculture. Dex, β-GP and Vc in culture medium were essential for calcified nodule formation by rBMCs. MZR had no direct effects on rBMCs. MZR-rBMCs may promote calcified nodule formation.

Despite rapid advances in the field of bone regeneration therapy, little is known about information related to the quality of bone regenerated under chronic inflammation. This study was carried out to compare the qualities (trabecular structure and collagen maturity) of regenerated bone in rat calvaria defects under different conditions of lipopolysaccharide (LPS) stimulation. To generate different residual levels of LPS at the defect sites, two types of gelatin sponges that release the bacterial endotoxin at different rates were applied; namely, LPS sustained-release gelatin (LS-G) sponge and LPS rapid-release gelatin (LR-G) sponge. Histomorphometric analysis by micro-computed tomography showed that, compared with rapid LPS stimulation with the LR-G sponge, sustained low-dose LPS stimulation using the LS-G sponge markedly impaired bone regeneration for up to 3 weeks, but not at 6 weeks, and induced a vulnerable trabecular structure. Polarized light microscopy with picrosirius red-stained tissue samples revealed that the LS-G sponge generated immature collagen in the regenerated bone. These deleterious changes in the trabecular structure and in collagen maturation were retained even after recovery of the bone volume at 6 weeks. These findings provide insights into the quality of regenerated bone during and after chronic inflammation.

The spontaneous differentiation of mouse-derived ES cells is suppressed by the supplementation of mouse Leukemia Inhibitory Factor (mLIF) into the medium. ES cells immediately differentiate when cultured in mLIF-free medium. Although the effects of mLIF on ES cell differentiation are well known, its effects on cell proliferation have hardly been investigated. Furthermore, no report has been published on the effects of mLIF in medium on cell viability. C60 fullerene has potent antioxidant capacity but little toxicity in in vivo and in vitro studies. Therefore, the effects of C60 fullerene on the viability of ES-D3 cells were examined in three-dimensional culture with and without mLIF, demonstrating no significant difference due to the supplementation of mLIF. Thus, we obtained data required for examining the effects of mLIF on the differentiation of ES-D3 cells.