No abstract

Transplanted PDL cell sheets cultured with osteogenic differentiation medium induced periodontal regeneration containing an obvious cementum layer and Sharpey's fibres. Thus, the method could be feasible as a new therapeutic approach for periodontal regeneration.

Wingless proteins, termed Wnt, are involved in embryonic development, blood cell differentiation, and tumorigenesis. In mammalian hematopoiesis, Wnt signaling is essential for stem-cell homeostasis and lymphocyte differentiation. Recent studies have suggested that these molecules are associated with cardiovascular diseases, rheumatoid arthritis, and osteoarthritis. Furthermore, Wnt5a signaling is essential for the general inflammatory response of human macrophages. Periodontitis is a chronic inflammatory disease caused by gram-negative periodontopathic bacteria and the resultant host immune response. Periodontitis is characterized by loss of tooth-supporting structures and alveolar bone resorption. There have been no previous reports on Wnt5a expression in periodontitis tissue, and only few study reported the molecular mechanisms of Wnt5a expression in LPS-stimulated monocytic cells. Using RT-PCR, we demonstrated that Wnt5a mRNA expression was up-regulated in chronic periodontitis tissue as compared to healthy control tissue. P. gingivalis LPS induced Wnt5a mRNA in the human monocytic cell line THP-1 with a peak at 4 hrs after stimulation. P. gingivalis LPS induced higher up-regulation of Wnt5a mRNA than E. coli LPS. The LPS receptors TLR2 and TLR4 were equally expressed on the surface of THP-1 cells. P. gingivalis LPS induced IκBα degradation and was able to increase the NF-κB binding activity to DNA. P. gingivalis LPS-induced Wnt5a expression was inhibited by NF-κB inhibitors, suggesting NF-κB involvement. Furthermore, IFN-γ synergistically enhanced the P. gingivalis LPS-induced production of Wnt5a. Pharmacological investigation and siRNA experiments showed that STAT1 was important for P. gingivalis LPS-induced Wnt5a expression. These results suggest that the modulation of Wnt5a expression by P. gingivalis may play an important role in the periodontal inflammatory process and serve a target for the development of new therapies.

SummaryPeriodontitis, a chronic inflammatory disease, is characterized by increased expression of interleukin (IL)-1 and other inflammatory mediators resulting in extensive osteoclast formation and bone loss. Expression of receptor activator of nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), by osteoblasts is important to regulate osteoclast differentiation. The aim of the present study was to investigate the regulatory effects of IL-1 on RANKL and OPG production by mesenchymal fibroblasts in periodontal tissue. Human gingival fibroblasts (HGF) and periodontal ligament fibroblasts (PDL) were stimulated with IL-1α α α α with or without protein synthesis inhibitor cycloheximide (CHX), protein kinase A (PKA) inhibitors, protein kinase C (PKC) inhibitors and prostaglandin E 2 (PGE 2 ) inhibitor. In some experiments, the cultured cells were directly stimulated with either PKA or PKC activators. In HGF, IL-1α α α α -stimulated OPG mRNA expression was high and could be reduced by CHX. PKA inhibitor completely abrogated IL-1α α α α -induced OPG mRNA expression and OPG production. Endogenous PGE 2 further enhanced IL-1α α α α -induced OPG production in HGF. In PDL, RANKL mRNA expression was greatly augmented by IL-1α α α α . IL-1α α α α induced OPG mRNA expression and protein production. PKC inhibitor partially reduced IL-1α α α α -induced OPG production and PKC activator enhanced OPG production in PDL. The IL-1α α α α -stimulated OPG mRNA expression in HGF was greater than PDL. These results provide new evidence for the possible osteoclastogenesis-inhibitory function of HGF through PKA activity pathway. PDL utilized PKC for OPG production. Thus, we emphasize that HGF and PDL have different characteristics of host defence mechanism against inflammatory process.