Fibroblast growth factor 2 inhibits the expression of stromal cell-derived factor 1α in periodontal ligament cells derived from human permanent teeth in vitro

Establishment of Down's syndrome periodontal ligament cells by transfection with SV40T-Ag and hTERT

Down's syndrome is one of the most common human congenital genetic diseases and affected patients have increased risk of periodontal disease. To examine involvement of the disease with periodontal disease development, we established immortalized periodontal ligament cells obtained from a Down's syndrome patient by use of SV40T-Ag and hTERT gene transfection. Expressions of SV40T-Ag and hTERT were observed in periodontal ligament cell-derived immortalized cells established from healthy (STPDL) and Down's syndrome patient (STPDLDS) samples. Primary cultured periodontal ligament cells obtained from a healthy subject (pPDL) had a limited number of population doublings (< 40), while STPDL and STPDLDS cells continued to grow with more than 80 population doublings. Primary cultured periodontal ligament cells obtained from the patient showed a chromosome pattern characteristic of Down's syndrome with trisomy 21, whereas STPDLDS samples showed a large number of abnormal chromosomes in those results. Gene expression analysis revealed that expression of DSCR-1 in STPDLDS is greater than that in STPDL. These results suggest that the newly established STPDLDS cell line may be a useful tool for study of periodontal disease in Down's syndrome patients.

Enhancement of Anti-Inflammatory and Osteogenic Abilities of Mesenchymal Stem Cells via Cell-to-Cell Adhesion to Periodontal Ligament-Derived Fibroblasts

Mesenchymal stem cells (MSCs) are involved in anti-inflammatory events and tissue repair; these functions are activated by their migration or homing to inflammatory tissues in response to various chemokines. However, the mechanism by which MSCs interact with other cell types in inflammatory tissue remains unclear. We investigated the role of periodontal ligament fibroblasts (PDL-Fs) in regulating the anti-inflammatory and osteogenic abilities of bone marrow-derived- (BM-) MSCs. The expression of monocyte chemotactic protein- (MCP-)1 was significantly enhanced by stimulation of PDL-Fs with inflammatory cytokines. MCP-1 induced the migratory ability of BM-MSCs but not PDL-Fs. Expression levels of anti-inflammatory and inflammatory cytokines were increased and decreased, respectively, by direct-contact coculture between MSCs and PDL-Fs. In addition, the direct-contact coculture enhanced the expression of MSC markers that play important roles in the self-renewal and maintenance of multipotency of MSCs, which in turn induced the osteogenic ability of the cells. These results suggest that MCP-1 induces the migration and homing of BM-MSCs into the PDL inflammatory tissue. The subsequent adherence of MSCs to PDL-Fs plays an immunomodulatory role to terminate inflammation during wound healing and upregulates the expression stem cell markers to enhance the stemness of MSCs, thereby facilitating bone formation in damaged PDL tissue.

Modulation of stromal cell-derived factor 1 alpha (SDF-1α) and its receptor CXCR4 in Porphyromonas gingivalis-induced periodontal inflammation

Background

The production of chemokines by tissue resident cells during inflammation is considered one of the main mechanisms involved in the formation of inflammatory infiltrates. Fibroblasts are the main resident cell type in gingival and periodontal ligament tissues, and their ability to produce chemokine stromal cell-derived factor 1 alpha (SDF-1α) and its receptor CXCR4 under stimulation by gram negative bacteria, Porphyromonas gingivalis, commonly found in periodontal infections was investigated.

Methods

Western blots were used to assess SDF-1α and CXCR4 protein expression levels in human gingival fibroblast cells (HGF-1) induced by Lipopolysaccharide (LPS) from P. gingivalis in the presence or absence of LY294002, a highly selective inhibitor of PI-3K/Akt. RT-PCR and quantitative Real-time PCR was performed using gingival mRNAs from periodontitis patients. Immunohistochemistry was performed to analyze the expression and subcellular localization of SDF-1α and CXCR4, together with NF-kβ phosphorylation, in specimens from patients with periodontitis and in an experimental rat periodontitis model.

Results

We found that P. gingivalis LPS up-regulated SDF-1α and CXCR4 protein levels and elevated phosphorylation of the SDF-1α-responsive NF-kβ and Akt at 24 h in HGF-1 cells. SDF-1α and CXCR4 mRNA and protein expression levels were high in all patients with periodontitis. In the P. gingivalis-induced rat experimental periodontitis model, SDF-1α and CXCR4 immunoreactivity was higher in gingival and periodontal ligament tissues compared to the control.

Conclusion

Our data showed that PI-3K/Akt is an upstream participant in the P. gingivalis LPS-mediated induction of SDF-1α. Taken together, these results suggest that the chemokine SDF-1α and its receptor CXCR4 contribute to P. gingivalis-induced periodontal inflammation.

Forced mastication increases survival of adult neural stem cells in the hippocampal dentate gyrus

In this study, we examined the effect of forced mastication on neurogenesis in the hippocampal dentate gyrus (DG) of adult mice. Six-week-old mice were subjected to either a hard or normal diet for 13 weeks. They received a daily injection of bromodeoxyuridine (BrdU) for 12 consecutive days beginning at 14 weeks of age. The number of BrdU-positive cells in the DG was counted 1 day after and 5 weeks after the final BrdU injection. The number of BrdU-positive cells 1 day after injection did not differ between the 2 diet groups. However, the number of BrdU-positive cells in the group fed the hard diet was significantly increased 5 weeks after BrdU injection compared to the group fed the normal diet. The results of the Morris water maze test showed that mice fed a hard diet required significantly less time to reach the platform than the control mice when tested at 10 days. Moreover, mice in the group fed the hard diet spent significantly more time in the former platform area than the group fed the normal diet, indicating that hard diet feeding improved spatial memory compared to normal diet feeding. Real-time PCR analysis showed that the expression of glutamate receptor 1 mRNA was significantly increased in the group fed the hard diet compared with the group fed the normal diet. These results suggest that mastication increases the survival of adult neural stem cells in the hippocampal DG.

MyD88 or TRAM knockdown regulates interleukin (IL)-6, IL-8, and CXCL12 mRNA expression in human gingival and periodontal ligament fibroblasts

BACKGROUND

In a previous report, it was shown that Toll-like receptor (TLR) 2 knockdown modulates interleukin (IL)-6 and IL-8 but not the chemokine CXCL12, an important mediator with inflammatory and proangiogenic effects, in human gingival fibroblasts (HGF) and human periodontal ligament fibroblasts (HPDLF). This study investigates whether knocking down two important TLR adaptor molecules, such as myeloid differentiation protein 88 (MyD88) and TRIF-related adaptor molecule (TRAM), could affect mRNA expression of IL-6, IL-8, and CXCL12 in HGF and HPDLF.

METHODS

After small interfering (si) RNA-mediated silencing of MyD88 or TRAM, HGF and HPDLF were stimulated with Porphyromonas gingivalis (Pg) lipopolysaccharide (LPS) or two synthetic ligands of TLR2 (Pam2CSK4 and Pam3CSK4) for 6 hours. IL-6, IL-8, and CXCL12 mRNAs were evaluated by quantitative polymerase chain reaction.

RESULTS

Knockdown of MyD88 or TRAM partially impaired the IL-8 mRNA upregulation in both fibroblast subpopulations. Similarly, IL-6 upregulation was partially prevented by siMyD88 or siTRAM in HGF stimulated with Pg LPS, as well as in both fibroblast subtypes challenged with Pam2CSK4. Conversely, constitutive CXCL12 mRNA levels were upregulated by MyD88 or TRAM knockdown in non-stimulated cells.

CONCLUSIONS

These results suggest that TLR adaptor molecules knockdown, such as MyD88 or TRAM, can decrease IL-6 and IL-8 mRNA and increase CXCL12 mRNA expression in HGF and HPDLF. This can be an important step for better understanding the mechanisms that control the inflammatory cytokine and chemokine expression, which in turn contributes to periodontal pathogenesis.