Ubiquitous sialometabolism present among oral fusobacteria.

Fusobacterium nucleatum is a ubiquitous member of the human oral flora and is associated with the development of periodontitis and a variety of other types of polymicrobial infections of the mucosa. In the oral cavity, this species is one of the few that is prevalent in both healthy and diseased subgingival plaque. Using microarray analysis, we examined the transcriptional response of F. nucleatum subspecies nucleatum to whole blood in order to identify some of the genetic responses that might occur during the transition from health to disease. From these studies, we identified a sialic acid catabolism operon that was induced by the presence of blood. We subsequently confirmed that this operon was inducible by the presence of synthetic sialic acid, but we found no evidence suggesting sialic acid was used as a major carbon source. However, this organism was found to possess a de novo synthesized surface sialylation ability that is widely conserved among the various F. nucleatum subspecies as well as in F. periodonticum. We provide evidence that fusobacterial sialylation does occur in the oral cavity irrespective of health status. Interestingly, only a minority of fusobacterial cells exhibit surface sialylation within dental plaque, whereas most cells are uniformly sialylated when grown in pure culture. The implications of these results are discussed.

Decellularization method influences early remodeling of an allogenic tissue scaffold.

Extracellular matrix-based biomaterials are currently pursued as an alternative to autologous transplants for the treatment of gingival recession and periodontal disease. These grafts offer improved tissue regeneration without the need for a second operative procedure used in current treatments to remove nonresorbable synthetic biomaterials. However, while decellularization is necessary to minimize the potential immunological impact, it can significantly modify the materials architectural and biochemical properties. By understanding cellular responses, it is possible to more specifically target varying clinical situations. These investigations assess a novel allogenic scaffold derived from the human umbilical vein and determine the effects of two decellularization approaches (osmotic lysis and the surfactant Triton X-100) on the biological and mechanical properties during early remodeling events. Results show Triton X-100 to be significantly more effective at extracting lipids, while the extraction of the scaffolds bulk protein, GAG and DNA similar between the two treatments. Once seeded, scaffolds prepared with osmotic lysis displayed increased cellular proliferation and reduced metabolic activity compared to scaffolds treated with surfactant. Biomechanical properties were largely preserved and similar between the two treatments. These results suggest that by optimizing scaffold processing conditions, biological events associated with remodeling can be modulated to tailor scaffold function for specific clinical applications.

The relationship between receptor for advanced glycation end products expression and the severity of periodontal disease in the gingiva of diabetic and non diabetic periodontitis patients.

OBJECTIVE: Activation of receptor for advanced glycation end products (RAGE) has been implicated in many chronic diseases, including diabetic complications. In this study we examined the relationship between RAGE expression and the morphological changes seen in the gingiva of diabetic and periodontitis patients. DESIGN: Gingival biopsies from 15 diabetic patients with periodontitis, 25 non diabetic patients with periodontitis and 10 healthy individuals were collected. Sections were stained with haematoxylin and eosin, and immunohistochemically to detect RAGE. Samples were examined in light and fluorescence microscopes and histomorphometric analysis was performed. RESULTS: Increased number of inflammatory cells and changes in collagen and vasculature were observed in diabetic and non diabetic patients with periodontitis. RAGE was weakly expressed in healthy gingiva. The strongest reaction with anti-RAGE antibody was found in the gingiva of diabetic patients with periodontitis followed by the severe periodontitis patients. RAGE expression in inflammatory cells was stronger than in the epithelium. The number of inflammatory cells in the gingiva was higher in the diabetic periodontitis patients than in the non diabetic severe periodontitis patients. CONCLUSIONS: RAGE is strongly expressed in the gingiva of diabetic patients with periodontitis and with severe periodontitis alone, the latter indicating RAGE activation even in the absence of hyperglycemia. However our findings are based on relatively small sample size. With a larger patient population, some of our other findings may have reached statistical significance.

Biomechanical behavior of oral soft tissues.

BACKGROUND: Little attention has been given to understanding the variation in biomechanical behavior of oral soft tissues, and this represents an obstacle for the development of biomaterials that perform with appropriate biomechanical characteristics. With this as our motivation, a uniaxial mechanical analysis was performed on lingual and buccal aspects of the attached gingiva, alveolar mucosa, and buccal mucosa to gain insight into human tissue performance and site-specific mechanical variation. METHODS: A discrete quantitative mechanical evaluation of each soft tissue region using tensile, dynamic compression, and stress relaxation analysis was conducted to correlate tissue structure with function as assessed histologically. RESULTS: Results confirm the keratinized gingiva to have increased tensile strength (3.94 ± 1.19 MPa) and stiffness (Young modulus of 19.75 ± 6.20 MPa) relative to non-keratinized mucosal regions, where densely arranged elastin fibers contribute to a tissue with increased viscoelastic properties. Dynamic compression analysis indicated the instantaneous modulus (E(int)), steady modulus (E(s)), and peak stress increased with loading frequency and strain amplitude, with the highest values found in the buccal attached gingiva. CONCLUSION: These investigations quantify the biomechanical properties of oral soft tissues and show region-to-region variation that details structure-function relationships and provides key parameters to aid development of biomaterials that perform with appropriate biomechanical properties.

Cellular interactions and biomechanical properties of a unique vascular-derived scaffold for periodontal tissue regeneration.

These investigations describe the development of a novel ex vivo three-dimensional scaffold derived from the human umbilical vein (HUV), and its potential as a regenerative matrix for tissue regeneration. Unique properties associated with the vascular wall have shown potential to function as a surgical barrier for guided tissue regeneration, particularly with the regeneration of periodontal tissues. HUV was isolated from umbilical cords using a semiautomated machining technology, decellularized using 1% sodium dodecyl sulfate, and then opened longitudinally to form tissue sheets. Uniaxial tensile testing, stress relaxation, and suture retention tests were performed on the acellular matrix to evaluate the HUV's biomechanical properties, followed by an evaluation of cellular interactions by seeding human gingival fibroblasts to assess adhesion, metabolic function, and proliferation on the scaffold. The scaffold's biomechanical properties were shown to display anisotropic behavior, which is attributed to the ex vivo material's composite structure. Detailed results indicated that the ultimate tensile strength of the longitudinal strips was significantly higher than that of the circumferential strips (p < 0.001). The HUV also exhibited significantly higher stress relaxation response in the longitudinal direction than in the circumferential orientation (p < 0.05). The ablumenal and lumenal surfaces of the material were also shown to differentially influence cell proliferation and metabolic activity, with both cellular functions significantly increased on the ablumenal surface (p < 0.05). Human gingival fibroblast migration into the scaffold was also influenced by the organization of extracellular matrix components, where the lumenal surface inhibits cell migration, acting as a barrier, while the ablumenal surface, which is proposed to interface with the wound site, promotes cellular invasion. These results show the HUV bioscaffold to be a promising naturally derived surgical barrier that may function well as a resorbable guided tissue regeneration membrane as well as in other clinical applications.

Antibacterial activity of chitosan-based matrices on oral pathogens.

Chitosan is a well sought-after polysaccharide in biomedical applications due to its biocompatibility, biodegradability to non-toxic substances, and ease of fabrication into various configurations. However, alterations in the anti-bacterial properties of chitosan in various forms is not completely understood. The objective of this study was to evaluate the anti-bacterial properties of chitosan matrices in different configurations against two pathogens-Gram-positive Streptococcus mutans and Gram-negative Actinobacillus actinomycetemcomitans. Two-dimensional (2-D) membranes and three-dimensional (3-D) porous scaffolds were synthesized by air drying and controlled-rate freeze drying. Matrices were suspended in bacterial broths with or without lysozyme (enzyme that degrades chitosan). Influences of pore size, blending with Polycaprolactone (PCL, a synthetic polymer), and neutralization process on bacterial proliferation were studied. Transient changes in optical density of the broth, adhesion characteristics, viability, and contact-dependent bacterial activity were assessed. 3-D porous scaffolds were more effective in reducing the proliferation of S. mutans in suspension than 2-D membranes. However, no significant differences were observed on the proliferation of A. actinomycetemcomitans. Presence of lysozyme significantly increased the antibacterial activity of chitosan against A. actinomycetemcomitans. Pore size did not affect the proliferation kinetics of either species, with or without lysozyme. NaOH neutralization of chitosan increased bacterial adhesion whereas ethanol neutralization inhibited adhesion without lowering proliferation. Mat culture tests indicated that chitosan does not allow proliferation on its surface and it loses antibacterial activity upon blending with PCL. Results suggest that the chemical and structural characteristics of chitosan-based matrices can be manipulated to influence the interaction of different bacterial species.