Gingival tissue transcriptomes provide a valuable scientific tool for further hypothesis-driven studies of the pathobiology of periodontitis.

Aims-We investigated the effect of comprehensive periodontal therapy on the levels of multiple systemic inflammatory biomarkers.Methods-Thirty patients with severe periodontitis received comprehensive periodontal therapy within a 6-week period. Blood samples were obtained at: one week pre-therapy (T1), therapy initiation (T2), treatment completion (T3), and 4 weeks thereafter (T4). We assessed plasma concentrations of 19 biomarkers using multiplex assays, and serum IgG antibodies to periodontal bacteria using checkerboard immunoblotting. At T2 and T4, dental plaque samples were analyzed using checkerboard hybridizations.Results-At T3, PAI-1, sE-selectin, sVCAM-1, MMP-9, myeloperoxidase, and a composite Summary Inflammatory Score (SIS) were significantly reduced. However, only sE-selectin, sICAM, and serum amyloid P sustained a reduction at T4. Responses were highly variable: analyses of SIS slopes between baseline and T4 showed that approximately 1/3 and 1/4 of the patients experienced marked reduction and pronounced increase in systemic inflammation, respectively, while the remainder were seemingly unchanged. Changes in inflammatory markers correlated poorly with clinical, microbiological and serological markers of periodontitis.Conclusions-Periodontal therapy resulted in an overall reduction of systemic inflammation, but the responses were inconsistent across subjects and largely not sustainable. The determinants of this substantial heterogeneity need to be explored further.

BackgroundPeriodontitis is a chronic inflammatory disease caused by the microbiota of the periodontal pocket. We investigated the association between subgingival bacterial profiles and gene expression patterns in gingival tissues of patients with periodontitis. A total of 120 patients undergoing periodontal surgery contributed with a minimum of two interproximal gingival papillae (range 2-4) from a maxillary posterior region. Prior to tissue harvesting, subgingival plaque samples were collected from the mesial and distal aspects of each tissue sample. Gingival tissue RNA was extracted, reverse-transcribed, labeled, and hybridized with whole-genome microarrays (310 in total). Plaque samples were analyzed using checkerboard DNA-DNA hybridizations with respect to 11 bacterial species. Random effects linear regression models considered bacterial levels as exposure and expression profiles as outcome variables. Gene Ontology analyses summarized the expression patterns into biologically relevant categories.ResultsWide inter-species variation was noted in the number of differentially expressed gingival tissue genes according to subgingival bacterial levels: Using a Bonferroni correction (p < 9.15 × 10-7), 9,392 probe sets were differentially associated with levels of Tannerella forsythia, 8,537 with Porphyromonas gingivalis, 6,460 with Aggregatibacter actinomycetemcomitans, 506 with Eikenella corrodens and only 8 with Actinomyces naeslundii. Cluster analysis identified commonalities and differences among tissue gene expression patterns differentially regulated according to bacterial levels.ConclusionOur findings suggest that the microbial content of the periodontal pocket is a determinant of gene expression in the gingival tissues and provide new insights into the differential ability of periodontal species to elicit a local host response.

Aims-We investigated the effects of periodontal therapy on gene expression of peripheral blood monocytes.Methods-Fifteen patients with periodontitis gave blood samples at four time points: 1 week before periodontal treatment (#1), at treatment initiation (baseline, #2), 6-week (#3) and 10-week postbaseline (#4). At baseline and 10 weeks, periodontal status was recorded and subgingival plaque samples were obtained. Periodontal therapy (periodontal surgery and extractions without adjunctive antibiotics) was completed within 6 weeks. At each time point, serum concentrations of 19 biomarkers were determined. Peripheral blood monocytes were purified, RNA was extracted, reverse-transcribed, labelled and hybridized with AffymetrixU133Plus2.0 chips. Expression profiles were analysed using linear random-effects models. Further analysis of gene ontology terms summarized the expression patterns into biologically relevant categories. Differential expression of selected genes was confirmed by real-time reverse transcriptase-polymerase chain reaction in a subset of patients.Address: Panos N. Papapanou Division of Periodontics Section of Oral and Diagnostic Sciences College of Dental Medicine Columbia University 630 W 168th Street PH-7-E-110 New York NY 10032 USA E-mail: E-mail: pp192@columbia.edu. Conflict of interest and source of fundingThe authors declare that they have no conflict of interests. Supplementary materialThe following material is available for this article online: Fig. S1. Dendrogram for hierarchical clustering of expression profiles for all patient samples. Data for the top 500 probe sets showing interactions between patient and treatment were used as input for average linkage hierarchical clustering. Samples for several patients corresponding to post-treatment time points cluster together. This result supports the idea that there is a relatively coherent response in some patients that we refer to as top responders in the main text, especially in patients 35, 36 and 40. Fig. S2. Visualization of the pairwise correlations of the expression profiles for each sample in the study. Data from all probe sets was used as input. Darker colors indicate lower correlations (correlations less that 0.75 would be shown as black, see scale bar). This figure indicates that a subset of samples exhibit substantially lower correlations with other samples. These largely correspond to post-treatment time points from patients identified as "top responders", for example samples from patients 40, 36, 35 and 45. This material is available as part of the online article from: http://www.blackwell-synergy.com/doi/abs/10.1111/j.1600-051X.2007.01113.x (This link will take you to the article abstract)Publisher's Disclaimer: Please note: Blackwell Publishing is not responsible for the content or func-tionality of any supplementary materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Results-Treatment resulted in a substantial improvement in clin...