Aim Variations in the expression of cytokines during the progression of periodontitis remain ill-defined. We evaluated the expression of 19 cytokine genes related to T cell phenotype/function during initiation, progression, and resolution of periodontitis, and related these to the expression of soft and bone tissue destruction genes (TDGs). Materials and Methods A ligature-induced periodontitis model was used in rhesus monkeys (M. mulatta) (n=18). Gingival tissues were taken at baseline pre-ligation, 2 weeks and 1 month (Initiation), and 3 months (Progression) post-ligation. Ligatures were removed and samples taken 2 months later (Resolution). Total RNA was isolated and the Rhesus Gene 1.0 ST (Affymetrix) used for gene expression analysis. Significant expression changes were validated by qRT-PCR. Results Disease Initiation/Progression was characterized by over-expression of Th17/Treg cytokine genes (IL-1β, IL-6, TGFβ, and IL-21) and down-regulation of Th1/Th2 cytokine genes (IL-18, and IL-25). Increased IL-2 and decreased IL-10 levels were seen during disease resolution. Several Th17/Treg cytokine genes positively correlated with TDGs, whereas most Th1/Th2 genes exhibited a negative correlation. Conclusion Initiation, progression and resolution of periodontitis involve over- and under-expression of cytokine genes related to various T-helper subsets. In addition, variations in individual T-helper response subset/genes during disease progression correlated to protective/destructive outcomes.

Maintenance of periodontal health or transition to a periodontal lesion reflects the continuous and ongoing battle between the vast microbial ecology in the oral cavity and the array of resident and emigrating inflammatory/immune cells in the periodontium. This war clearly signifies many 'battlefronts' representing the interface of the mucosal-surface cells with the dynamic biofilms composed of commensal and potential pathogenic species, as well as more recent knowledge demonstrating active invasion of cells and tissues of the periodontium leading to skirmishes in connective tissue, the locality of bone and even in the local vasculature. Research in the discipline has uncovered a concerted effort of the microbiome, using an array of survival strategies, to interact with other bacteria and host cells. These strategies aid in colonization by 'ambushing, infiltrating and outflanking' host cells and molecules, responding to local environmental changes (including booby traps for host biomolecules), communicating within and between genera and species that provide MASINT (Measurement and Signature Intelligence) to enhance sustained survival, sabotage the host inflammatory and immune responses and by potentially adopting a 'Fabian strategy' with a war of attrition and resulting disease manifestations. Additionally, much has been learned regarding the ever-increasing complexity of the host-response armamentarium at both cellular and molecular levels that is addressed in this review. Knowledge regarding how these systems fully interact requires both new laboratory and clinical tools, as well as sophisticated modeling of the networks that help maintain homeostasis and are dysregulated in disease. Finally, the triggers resulting in a 'coup de main' by the microbiome (exacerbation of disease) and the characteristics of susceptible hosts that can result in 'pyrrhic victories' with collateral damage to host tissues, the hallmark of periodontitis, remains unclear. While much has been learned, substantial gaps in our understanding of the 'parameters of this war' remain elusive toward fulfilling the Sun Tzu adage: 'If you know the enemy and know yourself, you need not fear the result of a hundred battles.'

In pregnant women with periodontitis, non-surgical periodontal therapy significantly reduced levels of periodontal pathogens. Baseline levels of selected periodontal pathogens or changes in these bacteria resulting from therapy were not associated with preterm birth.

SUMMARY Recent evidence has determined a phenotypic and functional heterogeneity for macrophage populations. This plasticity of macrophage function has been related to specific properties of subsets (M1, M2) of these cells in inflammation, adaptive immune responses, and resolution of tissue destructive processes. This investigation hypothesized that targeted alterations in the distribution of macrophage phenotypes in aged individuals, and with periodontitis would be skewed towards M1 inflammatory macrophages in gingival tissues. The study used a nonhuman primate model to evaluate gene expression profiles as footprints of macrophage variation in healthy and periodontitis gingival tissues from animals 3–23 years of age and in periodontitis tissues in adult and aged animals. Significant increases in multiple genes reflecting overall increases in macrophage activities were observed in healthy aged tissues, and were significantly increased in periodontitis tissues from both adults and aged animals. Generally, gene expression patterns for M2 macrophages were similar in healthy young, adolescent, and adult tissues. However, modest increases were noted in healthy aged tissues, similar to those seen in periodontitis tissues from both age groups. M1 macrophage gene transcription patterns increased significantly over the age range in healthy tissues, with multiple genes (e.g. CCL13, CCL19, CCR7, TLR4) significantly increased in aged animals. Additionally, gene expression patterns for M1 macrophages were significantly increased in adult health versus periodontitis and aged healthy versus periodontitis. The findings supported a significant increase in macrophages with aging and in periodontitis. The primary increases in both healthy aged tissues and, particularly periodontitis tissues appeared in the M1 phenotype.

Oral bacterial biofilms trigger chronic inflammatory responses in the host that can result in the tissue destructive events of periodontitis. However, the characteristics of the capacity of specific host cell types to respond to these biofilms remain ill-defined. This report describes the use of a novel model of bacterial biofilms to stimulate oral epithelial cells and profile select cytokines and chemokines that contribute to the local inflammatory environment in the periodontium. Monoinfection biofilms were developed with Streptococcus sanguinis, Streptococcus oralis, Streptococcus gordonii, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis on rigid gas-permeable contact lenses. Biofilms, as well as planktonic cultures of these same bacterial species, were incubated under anaerobic conditions with a human oral epithelial cell line, OKF4, for up to 24 h. Gro-1α, IL1α, IL-6, IL-8, TGFα, Fractalkine, MIP-1α, and IP-10 were shown to be produced in response to a range of the planktonic or biofilm forms of these species. P. gingivalis biofilms significantly inhibited the production of all of these cytokines and chemokines, except MIP-1α. Generally, the biofilms of all species inhibited Gro-1α, TGFα, and Fractalkine production, while F. nucleatum biofilms stimulated significant increases in IL-1α, IL-6, IL-8, and IP-10. A. naeslundii biofilms induced elevated levels of IL-6, IL-8 and IP-10. The oral streptococcal species in biofilms or planktonic forms were poor stimulants for any of these mediators from the epithelial cells. The results of these studies demonstrate that oral bacteria in biofilms elicit a substantially different profile of responses compared to planktonic bacteria of the same species. Moreover, certain oral species are highly stimulatory when in biofilms and interact with host cell receptors to trigger pathways of responses that appear quite divergent from individual bacteria.

Aim Gingival tissues of periodontitis lesions contribute to local elevations in mediators, including both specific T cell and antibody immune responses to oral bacterial antigens. Thus, antigen processing and presentation activities must exist in these tissues to link antigen-presenting cells with adaptive immunity. We hypothesized that alterations in the transcriptome of antigen processing and presentation genes occur in aging gingival tissues and that periodontitis enhances these differences reflecting tissues less capable of immune resistance to oral pathogens. Materials and Methods Rhesus monkeys (n=34) from 3–23 years of age were examined. A buccal gingival sample from healthy or periodontitis sites were obtained, total RNA isolated, and microarray analysis was used to describe the transcriptome. Results The results demonstrated increased transcription of genes related to the MHC class II and negative regulation of NK cells with aging in healthy gingival tissues. In contrast, both adult and aging periodontitis tissues showed decreased transcription of genes for MHC class II antigens, coincident with up-regulation of MHC class I-associated genes. Conclusion These transcriptional changes suggest a response of healthy aging tissues through the class II pathway (i.e., endocytosed antigens) and altered responses in periodontitis that could reflect host-associated self-antigens or targeting cytosolic intra-cellular microbial pathogens.

Synthesis of a porous bioactive ceramic implant for load bearing applications is a challenging task in maxillofacial and orthopedic surgeries. A novel bioactive resorbable silica-calcium phosphate nanocomposite (SCPC) has recently been introduced as a potential bone graft. In the present study, we employed SCPC to develop a resorbable porous scaffold and analyzed the effects of composition and porosity on the mechanical properties. The ranges of compressive strength and modulus of elasticity of SCPC containing 32-56% porosity were 1.5-50 MPa and 0.14-2.1 GPa, respectively, which matched the corresponding values for trabecular bone. The compressive strength of dense SCPC was dependent on the Si content and acquired values (93-285 MPa) comparable to that of cortical bone. The superior mechanical properties of SCPC are attributed to the intricate interactions at the boundaries of the nanograins and to the homogenous distribution of hierarchical pore-structure throughout the material volume. X-ray computed tomography and mercury porosimetry analyses revealed high interconnectivity of the pores in the size range 3 nm to 650 microm. Quantitative real-time PCR analyses showed that neonatal rat calvarial osteoblasts attached to Si-rich SCPC expressed 5- and 26-fold higher osteocalcin mRNA levels compared to cells attached to ProOsteon hydroxyapatite disks and tissue culture polystyrene plates respectively, after four days in culture. Results of the present study strongly suggest that porous, bioactive resorbable SCPCs can serve as tissue engineering scaffolds for cell delivery to treat load-bearing bone defects in orthopedic and maxillofacial surgeries.

Silica-calcium phosphate nanocomposite (SCPC) has recently been proposed as a novel resorbable, bioactive, and mechanically compatible template for bone reconstruction. The effect of the physicochemical properties on the surface reactivity and dissolution kinetics of SCPC immersed in simulated body fluid (SBF) was investigated and compared to that of bioactive glass (BG). Moreover, the stimulatory effect on osteoblast gene expression of SCPC was determined using quantitative real-time polymerase chain reaction (qRT-PCR), and compared to that of hydroxyapatite (HA-200). Mercury porosimetry revealed that surface areas of SCPC particles containing 10 (SCPC10), 30 (SCPC30), and 50 (SCPC50) wt % Si-content were 14-, 18-, and 32-times higher than that of BG. Inductively coupled plasma analysis showed that after 192 h of immersion, Si-rich SCPC50 exhibited controlled bulk-dissolution and released 43.1 ppm Si, which was sixfold higher than that released from BG (7.7 ppm). Moreover, SCPC50 showed a rapid Ca-uptake from SBF and developed a surface apatite layer after only 2 h, whereas a similar layer was detected on BG after 8 days of immersion under the same experimental conditions. qRT-PCR revealed that osteopontin and osteocalcin mRNA expression by osteoblast-like cells attached to Si-rich SCPC50 was significantly higher than that on HA-200 or polystyrene after 2 days in culture. This suggested a role of dissolved Si in stimulating the differentiation and mineralization of osteoblast precursor cells. The favorable physiochemical and bioactivity properties of Si-rich SCPC nanocomposite indicate that SCPC can have wide applications as a synthetic bone graft for cell delivery applications in tissue engineering.