Effect of tension-force on plasminogen activator activity from human periodontal ligament cells

The plasminogen activator (PA)-plasmin proteolytic system has recently received considerable attention because of its participation in a wide variety of biological activities and in pathological conditions involving tissue destruction. Excessive mechanical stress such as occlusal trauma is associated with alveolar bone loss in severe periodontitis. Therefore, mechanical stress may involve degradation of the extracellular matrix by occlusal trauma through activation of the PA-plasmin proteolytic system. We examined the effects of mechanical stress on PA activity, gene expressions of tissue type (t) PA, urokinase type (u) PA and PA inhibitor-1 (PAI-1) in human PDL cells. Human PDL cells were cultured on flexible-bottomed culture plates and placed on a Flexercell Strain Unit. The cells were flexed at 6 cycles (5 s strain, 5 s relaxation) at 9% and 18% elongation for 5 d. Application of tension-force induced significantly higher PA activity in stressed PDL cells than in non-stressed controls, and did so in a time- and magnitude-dependent manner (p<0.001, ANOVA). Western-blot analysis revealed that the high level of activity was due to tPA and not uPA. Gene expression of tPA mRNA in stressed PDL cells, as examined by RT-PCR, increased on d 5. These findings suggest that tPA may be involved in periodontal metabolism in response to mechanical stress.     

CT evaluation of trauma to the temporomandibular joint

The computed tomograms of 43 patients who had suffered craniofacial trauma and who were referred for evaluation of complaints of temporomandibular joint (TMJ) pain and dysfunction were reviewed. Fifteen of the 43 patients (34%) had sustained fractures, 16 (37%) had documented articular disc derangements without associated fractures, and 32 patients (74%) had degenerative joint changes. Computed tomography (CT) showed fractures, degenerative joint changes, and articular disc displacements not seen on conventional radiographs indicating that CT is particularly useful when patients' symptoms are not adequately explained by conventional radiographs or tomograms.     

Dexamethasone inhibits formation of osteoclast-like cells in bone-marrow cultures

Our observations confirm the previously reported observation that multinucleated cells develop within a two-week period in cat bone-marrow cultures. Calcitonin induces cytoplasmic contraction in these multinucleated cells, which indicates that they resemble osteoclasts. After seven days of culture, cat bone-marrow cultures contain both non-attached mononuclear cells and attached mononuclear and polynuclear cells. We have cultured the attached and non-attached cell populations separately from day 7 onward and have observed the appearance of multinucleated cells in both culture systems. In both types of cultures, dexamethasone (10(-9)-10(-7) mol/L) reduced the number of multinucleated cells. This effect of dexamethasone was more rapid in the cultures derived from non-attached cells (seven days) than in cultures derived from attached cells (14 days), suggesting that two different mechanisms are involved. Dexamethasone had no effect on the survival of multinucleated cells already formed.     

Bacterial adherence to gingival epithelial cells of rats with naturally occurring gingivitis

Bacterial adherence to gingival cells was compared in rats with spontaneous gingivitis (SUS rat) and in control rats (RES rat). In the SUS rat, the number of adherent bacteria in gingival cells changed according to the progression of gingival inflammation. There was a correlation between the change of the number of adherent bacteria, progress of inflammation and pH in the pocket. In the RES rat, the number of adherent bacteria was constant and very small. In the adherence assay, adherence of Bacteroides intermedius to epithelial cells was dependent on the pH. Adherence of B. intermedius was better than that of other species. B. gingivalis and B. macacae showed good adherence but B. levii showed poor adherence. Adherence to the epithelial cells of the SUS rat was always better than that of the RES rat. These results were supported by scanning electron microscopic studies.     

Effects of ethanol consumption on periodontal inflammation in rats

Studies suggest a correlation between ethanol consumption and periodontal disease. We hypothesized that elevated levels of blood reactive oxygen species following ethanol consumption may increase inflammation in periodontal tissue. Rats were divided into 4 groups (6-7 rats/group). Two groups were fed an ethanol-containing liquid diet, and 2 groups were fed a pair-fed control diet. In one of each dietary group, periodontitis was ligature-induced, while the other group was left unligated. Chronic ethanol feeding alone decreased the ratio of reduced/oxidized glutathione and increased 8-hydroxydeoxy-guanosine and tumor necrosis factor (TNF)-alpha levels in the gingiva. Blood hydroperoxides were also increased. In ligature-induced periodontitis lesions, ethanol feeding enhanced polymorpho-nuclear leukocyte infiltration and TNF-alpha expression. The results suggest that chronic alcohol consumption increased periodontal inflammation, oxidative damage, and TNF-alpha production and had an additive effect on polymorphonuclear leukocyte infiltration and gingival oxidative damage, increasing the severity of periodontal inflammation in the ligature model.