Differential Activation of Human Gingival Epithelial Cells and Monocytes by Porphyromonas gingivalis Fimbriae

Humans develop periodontitis in response to challenge by microbial dental plaque. Inflammation begins after perturbation of gingival epithelial cells by subgingival bacteria interacting through pattern-recognition receptors, including the Toll-like receptors (TLR). Porphyromonas gingivalis is a major periodontopathogen that interacts with epithelial cells through its cell surface fimbriae (FimA), leading to colonization and/or invasion. Previous work by our group has established membrane CD14 as an essential coreceptor for TLR2-mediated activation of transfected cell lines by P. gingivalis FimA. We have shown that gingival epithelial cells express TLR2 but not CD14 on their cell surfaces. We thus speculated that P. gingivalis FimA does not readily activate epithelial innate immune responses but rather functions to promote P. gingivalis colonization in the absence of a vigorous FimA-induced response. This hypothesis was verified by the findings that primary human gingival epithelial cells responded poorly to FimA in terms of interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor alpha responses, in stark contrast to the marked response to other TLR2 agonists (Pam3Cys, FSL-1) that are not strictly dependent on CD14. On the other hand, CD14-expressing human primary monocytes responded with high levels of the same cytokines to both FimA and the control TLR2 agonists. The gingival epithelial cells failed to respond to FimA even in the presence of exogenously added soluble CD14. These data indicate that the gingival epithelial cell hyporesponsiveness to FimA is attributable to the lack of membrane-expressed but not soluble CD14. In conclusion, P. gingivalis FimA differentially activates human monocytes and epithelial cells, perhaps reflecting different tactics used by P. gingivalis when interacting with different host cell types or a host strategy to limit inflammation

The effect of membrane exposure on lateral ridge augmentation: a case-controlled study

Abstract Background The effect of membrane exposure on guided bone regeneration (GBR) for lateral ridge augmentation has been poorly addressed. This case-controlled study aimed to investigate potential effect of membrane exposure lateral ridge augmentation and subsequent implant placement. Methods A total of 14 patients that did receive lateral ridge augmentation procedure using allogeneic cancellous graft particulate in combination with an alloplastic bioresorbable matrix barrier were retrospectively selected for this study. Bone width was measured at the crest with a digital caliper before bone augmentation and at the reopening for implant placement 4 months later for all patients. Cases where primary flap closure was achieved and the barrier did not expose throughout the time until implant placement were assigned to the control group (n = 7). Cases where primary closure could not be achieved or a barrier exposure happened within the first week following the initial surgery were assigned to the test group. Results The measured alveolar ridge width before surgery as well as after GBR procedure were not statistically significant different between the two groups (p > 0.05). Both groups showed a significant (p < 0.05) increase in their mean alveolar ridge width 4 months after later augmentation procedure, from 3.4 ± 1.2 to 6.0 ± 1.1 mm in the control group and from 3.6 ± 1.0 to 5.0 ± 1.4 mm in the test group. However, the mean alveolar ridge gain was significantly greater in the control group than in the test group (p < 0.05). Consequently, the reduction of the augmented alveolar ridge was significantly higher in the test group averaging to 4.7 mm than for the control group showing a loss of 3.1 mm after 4 months, respectively. However, in all 14 cases, successful implant placement was achieved after 4 months. Conclusions Within the limit of this study, it can be concluded that early exposure of a bioresorbable matrix barrier during lateral ridge augmentation may compromise the results of the GBR procedure but may still result in a favorable alveolar ridge width gain that allows for the placement of dental implants

Interleukin-1β Modulates Proinflammatory Cytokine Production in Human Epithelial Cells▿

Periodontitis is a chronic human inflammatory disease initiated and sustained by dental plaque microorganisms. A major contributing pathogen is Porphyromonas gingivalis, a gram-negative bacterium recognized by Toll-like receptor 2 (TLR2) and TLR4, which are expressed by human gingival epithelial cells (HGECs). However, it is still unclear how these cells respond to P. gingivalis and initiate inflammatory and immune responses. We have reported previously that HGECs produce a wide range of proinflammatory cytokines, including interleukin-6 (IL-6), IL-8, granulocyte-macrophage colony-stimulating factor, tumor necrosis factor alpha (TNF-α), and IL-1β. In this study, we show that IL-1β has a special role in the modulation of other inflammatory cytokines in HGECs challenged with P. gingivalis. Our results show that the increased production of IL-1β correlates with the cell surface expression of TLR4, and more specifically, TLR4-normal HGECs produce fourfold more IL-1β than do TLR4-deficient HGECs after challenge. Moreover, blocking the IL-1β receptor greatly reduces the production of “secondary” proinflammatory cytokines such as IL-8 or IL-6. Our data indicate that the induction of IL-1β plays an important role in mediating the release of other proinflammatory cytokines from primary human epithelial cells following challenge with P. gingivalis, and this process may be an inflammatory enhancement mechanism adopted by epithelial cells

Modulation of TLR2 Protein Expression by miR-105 in Human Oral Keratinocytes*

Mammalian biological processes such as inflammation, involve regulation of hundreds of genes controlling onset and termination. MicroRNAs (miRNAs) can translationally repress target mRNAs and regulate innate immune responses. Our model system comprised primary human keratinocytes, which exhibited robust differences in inflammatory cytokine production (interleukin-6 and tumor necrosis factor-α) following specific Toll-like receptor 2 and 4 (TLR-2/TLR-4) agonist challenge. We challenged these primary cells with Porphyromonas gingivalis (a Gram-negative bacterium that triggers TLR-2 and TLR-4) and performed miRNA expression profiling. We identified miRNA (miR)-105 as a modulator of TLR-2 protein translation in human gingival keratinocytes. There was a strong inverse correlation between cells that had high cytokine responses following TLR-2 agonist challenge and miR-105 levels. Knock-in and knock-down of miR-105 confirmed this inverse relationship. In silico analysis predicted that miR-105 had complementarity for TLR-2 mRNA, and the luciferase reporter assay verified this. Further understanding of the role of miRNA in host responses may elucidate disease susceptibility and suggest new anti-inflammatory therapeutics