The active role of gingival proteoglycans in periodontal disease

Turnover in periodontal connective tissues: dynamic homeostasis of cells, collagen and ground substances

The connective tissues of the periodontium are composed of two soft tissues and two hard tissues--each of which has unique features. This review considers the constituents of normal, healthy periodontal connective tissues together with an appraisal of the changes in the connective tissue matrices of the periodontium which occur during the development of periodontitis. Recent developments in this field have paved the way for new and exciting vistas in periodontal diagnosis and regeneration which, ultimately, are two important goals in periodontal therapy.

Proteoglycan changes in carcinogen (4NQO)-treated rat tongue mucosa

The purpose of this study was to undertake preliminary analyses of the extracellular proteoglycans in carcinogen [4-nitroquinoline N-oxide (4NQO)]-treated rat tongue mucosa. Experimental rats were exposed to twice-weekly applications of 4NQO in propylene glycol for six months, after which the animals were killed. Control and 4NQO-treated tissues were subjected to sequential aqueous extractions of proteoglycans under associative and dissociative conditions, followed by alkaline cleavage of protein-glycosaminoglycan linkages to yield a glycosaminoglycan residue. Tissues subjected to 4NQO applications contained smaller proportions of proteoglycans which were readily soluble under associative and dissociative conditions. Proportionately more proteoglycan remained strongly associated with other intercellular tissue components, being released only by alkaline cleavage. These biochemical alterations in preinvasive 4NQO-treated epithelium and connective tissues, together with an observed associated change in water retention by the connective tissue, occurred prior to actual neoplastic invasion and suggest differences in macromolecular conformation and orderliness. We hypothesize that these changes are related to the phenomenon of neoplastic epithelial invasion.

Identification of components in Fusobacterium nucleatum chemostat-culture supernatants that are potent inhibitors of human gingival fibroblast proliferation

The present investigation concerned the effect of chemostat-culture cell-free supernatants of Fusobacterium nucleatum on the growth and synthetic activity of human gingival fibroblasts in vitro. Human gingival fibroblasts were cultured in fetal calf serum supplemented Dulbecco-Vogt medium containing various dilutions of conditioned or unconditioned bacterial culture medium. Cell proliferation was monitored by assessing cell growth over 5 days or incorporation of [3H]-thymidine into DNA. Protein and proteoglycan synthesis were monitored by the incorporation of [3H]-proline and [35S]-sulfate, respectively, into macromolecules. While the conditioned culture medium caused a complete inhibition of cell growth and incorporation of [3H]-thymidine DNA, there was no discernible effect on protein or proteoglycan synthesis. This indicated that the cells remained viable yet unable to divide. Such a view was supported by the observation that the inhibitory effect was reversible upon removal of the conditioned medium. This activity had a molecular size less than 30,000, was heat-stable and nonvolatile. Chemical analysis of the conditioned bacterial culture supernatants indicated that high proportions of butyrate, ammonium, and acetate were present. When these components were added to unconditioned medium and tested, most of the inhibitory activity could be attributed to ammonium and butyrate. Since many bacteria which constitute the subgingival microflora release ammonium and butyrate, a very high concentration of these metabolites may well accumulate. Clearly, the potential for inhibition of fibroblast proliferation has ramifications related to diminished tissue repair following bacterially-induced periodontal destruction.

Effect of lipopolysaccharide on proteoglycan synthesis by adult human gingival fibroblasts in vitro

The effect of lipopolysaccharide preparations from Salmonella enteritidis, Bacteroides gingivalis, and Actinobacillus actinomycetemcomitans on human gingival fibroblasts was studied. Lipopolysaccharide from all sources inhibited fibroblast proliferation in the concentration range of 0.5 to 50 micrograms/ml, with the lipopolysaccharide from A. actinomycetemcomitans having the strongest inhibitory effect. Assessment of the effect of lipopolysaccharide on gingival fibroblast metabolism indicated both total protein and proteoglycan synthesis to be inhibited with increasing concentrations of lipopolysaccharide. As for the antiproliferative effect, lipopolysaccharide from A. actinomycetemcomitans had the greatest inhibitory effect on cell synthetic activity. This inhibitory effect was determined by pulse-chase experiments to be a true depression in synthesis. Furthermore, the effect was independent of lipopolysaccharide-induced changes in cell proliferation and prostaglandin synthesis. This study confirmed the toxic effect of lipopolysaccharide on fibroblasts and, in particular, indicated that various lipopolysaccharide preparations vary in their potency to influence cell proliferation and extracellular matrix synthesis.

The effect of chronic inflammation on gingival connective tissue proteoglycans and hyaluronic acid

Proteoglycans have been isolated and analysed from extracts of normal and chronically inflamed human gingiva in order to determine the effects of chronic inflammation on these important soft connective tissue extracellular macromolecules. The uronic acid content of glycosaminoglycans isolated by papain digestion of normal and inflamed gingiva did not differ significantly. Likewise, electrophoretic analysis revealed that the content of hyaluronic acid, heparan sulfate, dermatan sulfate and chondroitin sulfate was similar. The sulfated glycosaminoglycans from both sources eluted from a Sepharose C1-6B column with a Kav of 0.45 (approximate Mr 25,000). However, hyaluronic acid from normal gingiva was predominantly of a large size eluting in the void volume of a Sepharose. CL-6B column, while that isolated form inflamed tissue was mostly a small molecular weight species which eluted in the included volume of a Sepharose CL-6B column. Using dissociative conditions, intact proteoglycans could be more readily extracted from inflamed tissues (90% of the total tissue uronic acid) than from normal tissues where only 80% of the total tissue uronic acid was extractable. Even though DEAE-Sephacel ion-exchange chromatography revealed no differences in charge between normal and inflamed gingival proteoglycans, Sepharose CL-4B chromatography revealed more molecular size polydispersity in samples from inflamed tissue than from normal tissue. Taken together, these results indicate that while hyaluronic acid is depolymerized in inflamed tissue, no evidence of sulfated glycosaminoglycan degradation was found. Therefore, the most likely cause for disruption to the molecular integrity of the proteoglycans is via proteolytic alteration to the proteoglycan core protein.