Gap-junction-mediated Communication in Human Periodontal Ligament Cells

Periodontal tissue homeostasis depends on a complex cellular network that conveys cell-cell communication. Gap junctions (GJs), one of the intercellular communication systems, are found between adjacent human periodontal ligament (hPDL) cells; however, the functional GJ coupling between hPDL cells has not yet been elucidated. In this study, we investigated functional gap-junction-mediated intercellular communication in isolated primary hPDL cells. SEM images indicated that the cells were in contact with each other via dendritic processes, and also showed high anti-connexin43 (Cx43) immunoreactivity on these processes. Gap-junctional intercellular communication (GJIC) among hPDL cells was assessed by fluorescence recovery after a photobleaching (FRAP) analysis, which exhibited dye coupling between hPDL cells, and was remarkably down-regulated when the cells were treated with a GJ blocker. Additionally, we examined GJs under hypoxic stress. The fluorescence recovery and expression levels of Cx43 decreased time-dependently under the hypoxic condition. Exposure to GJ inhibitor or hypoxia increased RANKL expression, and decreased OPG expression. This study shows that GJIC is responsible for hPDL cells and that its activity is reduced under hypoxia. This is consistent with the possible role of hPDL cells in regulating the biochemical reactions in response to changes in the hypoxic environment.

Lipopolysaccharide of Aggregatibacter actinomycetemcomitans up-regulates inflammatory cytokines, prostaglandin E2 synthesis and osteoclast formation in interleukin-1 receptor antagonist-deficient mice

BACKGROUND AND OBJECTIVE

The interleukin (IL)-1 receptor antagonist (Ra) binds to IL-1 receptors and inhibits IL-1 activity. However, it is unclear whether the IL-1Ra plays a protective role in periodontal disease. The purpose of this study was to compare IL-1Ra knockout (KO) and wild-type (WT) mice in regard to proinflammatory cytokine production, osteoclast formation and bone resorption in response to periodontal bacterial lipopolysaccharide (LPS).

MATERIAL AND METHODS

Peritoneal macrophages (Mφs) were obtained from 13-wk-old IL-1Ra KO and WT mice. Peritoneal Mφs were cultured with or without 10 μg/mL of Aggregatibacter actinomycetemcomitans LPS for 24 h. The levels of IL-1alpha (IL-1α), IL-1beta (IL-1β), tumor necrosis factor-α (TNF-α) and IL-6 were measured in periotoneal Mφs supernatant fluid (PM-SF) using an ELISA. Bone marrow cells were obtained from the mice and stimulated with PM-SF for 9 d, then stained with TRAP. The frequency of TRAP-positive multinucleated giant cell formation was calculated based on a fusion index. PM-SF-stimulated calvarial bone resorption was analyzed using micro-computed tomography, and calvarial histological analysis was performed using hematoxylin and eosin and TRAP staining. The expression of cyclooxygenase-2 (Cox2), prostanoid receptor EP4 (Ep4) and Rank mRNAs in bone marrow cells were measured using real-time quantitative PCR, while prostaglandin E2 (PGE2 ) production was determined by ELISA.

RESULTS

The levels of IL-1α, IL-1β, TNF-α and IL-6 in IL-1Ra KO mice PM-SF stimulated with A. actinomycetemcomitans LPS were significantly increased by approximately 4- (p < 0.05), 5- (p < 0.05), 1.3- (p < 0.05) and 6- (p < 0.05) fold, respectively, compared with the levels in WT mice. Moreover, osteoclast formation, expression of Rank, Ep4 and Cox2 mRNAs and production of PGE2 were significantly increased by approximately 2- (p < 0.05), 1.6- (p < 0.05), 2.5- (p < 0.05), 1.6- (p < 0.05) and 1.9- (p < 0.05) fold, respectively, in IL-1Ra KO mice stimulated with A. actinomycetemcomitans LPS compared with WT mice.

CONCLUSION

IL-1Ra regulates IL-1 activity and appears to reduce the levels of other inflammatory cytokines, including TNF-α and IL-6, while it also reduces expression of the EP4 receptor related to prostanoid sensitivity and osteoclast formation. These results suggest that IL-1Ra is an important molecule for inhibition of inflammatory periodontal bone resorption.

SSEA-4 is a marker of human deciduous periodontal ligament stem cells

Although human deciduous teeth are an ideal source of adult stem cells, no method for identifying deciduous periodontal ligament (D-PDL) stem cells has so far been developed. In the present study, we investigated whether stage-specific embryonic antigen (SSEA)-4 is a marker that could be used to isolate D-PDL stem cells. The isolated D-PDL cells met the minimum criteria for mesenchymal stem cells (MSCs): They showed plastic adherence, specific-surface antigen expression, and multipotent differentiation potential. SSEA-4+ D-PDL cells were detected in vitro and in vivo. A flow cytometric analysis demonstrated that 22.7% of the D-PDL cells were positive for SSEA-4. SSEA-4+ clonal D-PDL cells displayed multilineage differentiation potential: They were able to differentiate into adipocytes, osteoblasts, and chondrocytes in vitro. A clonal assay demonstrated that 61.5% of the SSEA-4+ D-PDL cells had adipogenic, osteogenic, and chondrogenic potential. Our present study demonstrated that SSEA-4+ D-PDL cells are a subset of multipotent stem cells. Hence, SSEA-4 is a specific marker that can be used to identify D-PDL stem cells.

Hyperbilirubinemia in the early phase after allogeneic HSCT: prognostic significance of the alkaline phosphatase/total bilirubin ratio

Hyperbilirubinemia in the early phase after allogeneic hematopoietic SCT (HSCT) is due to various causes. One of the most important causes of hyperbilirubinemia is veno-occlusive disease/sinusoidal obstructive syndrome (VOD/SOS). However, the prognosis of patients who are clinically diagnosed as SOS varies. We retrospectively evaluated 82 patients who underwent their first allogeneic HSCT. GVHD prophylaxis was a combination of short-term MTX and CsA (n=77) or tacrolimus (n=5). Thirty-three patients developed hyperbilirubinemia, with a bilirubin level of at least 2 mg/dL, within 20 days after HSCT. Of these patients, 24 were diagnosed as VOD/SOS using the modified Seattle criteria. Twenty-six recovered to a bilirubin level of <2 mg/dL. We focused on the serum alkaline phosphatase/total bilirubin ratio (ALP/TB) at the onset of hyperbilirubinemia and found that it significantly predicted the recovery from hyperbilirubinemia. OS was significantly higher in patients with a lower ALP/TB ratio (P=0.00056). In addition, a lower ALP/TB ratio was associated with better survival even in patients who were clinically diagnosed as SOS (P<0.001). The ALP/TB ratio at the onset of hyperbilirubinemia may be a useful predictor for the prognosis of hyperbilirubinemia and SOS early after HSCT.

Maxillary stability after Le Fort I osteotomy using three different plate systems

The purpose of this study was to compare postoperative changes in maxillary stability after Le Fort I osteotomy in three groups: with an unsintered hydroxyapatite (u-HA)/poly-L-lactic acid (PLLA) plate; a PLLA plate; and a titanium plate. Subjects comprised 60 Japanese patients diagnosed with mandibular prognathism. All patients underwent Le Fort I osteotomy and bilateral sagittal split ramus osteotomy. All patients were randomized in groups of 20 to a u-HA/PLLA group, a PLLA plate group and a titanium plate group. Changes in postoperative time intervals between the plate groups were compared using lateral and posteroanterior cephalography. The uHA/PLLA group had significantly larger values than the PLLA group regarding change of mx1-S perpendicular to SN between 3 and 12 months (T3) (P=0.0269). The uHA/PLLA group had a significantly larger value than the PLLA group regarding change of S-A perpendicular to SN between baseline and 1 month (T1) (P=0.0257). There was no significant difference in the other measurements. This study suggests that maxillary stability with satisfactory results could be obtained in the u-HA/PLLA, PLLA plate and titanium plate groups, although there was a slight difference between the u-HA/PLLA and PLLA plate systems in Le Fort I osteotomy.

Heating characteristics with a re-entrant type applicator in consideration of tissue blood flow rate

We have proposed the heating system based on a re-entrant cavity that can heat a localized deep region in a living body noninvasively. This system is superior in a local heating characteristic. However, when the living body was treated as a heating object during thermotherapy (hyperthermia), the effect of blood flow changes on a heating characteristic has to be examined. The purpose of this study was to establish the quantitative evaluation method of heating characteristics for a re-entrant type applicator. The numerical analyses by using three-dimensional finite element method in consideration of a blood flow and fundamental experiments with prototype system were carried out. Since the difference of numerical analyses and experiments was as small as about 4.2 [%] by evaluation with full width at half maximum (FWHM), the validity of this numerical analysis was confirmed.

Behaviour and adsorptive removal of siloxanes in sewage sludge biogas

We investigated the behaviour of siloxanes, which adversely affect biogas engines, as well as their concentration levels in sewage sludge biogas in Japan. We also performed experiments on the absorptive removal of siloxanes using various adsorbents and determined the main adsorbent characteristics required for the removal of siloxanes. The results of our study on the concentration and composition of siloxanes in biogas were similar to previous reports. Moreover, we found that the concentration of siloxanes changes in relation to the outside air temperature based on real-time measurements of siloxanes using a continuous analyser. We further speculated that the continuous analyser would accurately indicate the siloxane concentration in model biogas but overestimate the siloxane concentration in actual biogas because of positive interference by VOCs and other biogas components. In the siloxane adsorption experiment, the equilibrium uptake of both cyclic siloxanes, D4 and D5, was positively related to the BET-specific surface area of the adsorbents and the fraction of the external surface area taken up by relatively large diameter pores. We attributed the adsorption results to the fact that the siloxane molecules are generally larger than micropores; therefore, they are less susceptible to adsorption to micropores. Based on these results, we concluded that adsorbents with large BET-specific surface areas, especially those with a high external specific surface area and pores of relatively large diameters, are desired for the removal of siloxanes.