Role of Mechanotransduction in Periodontal Homeostasis and Disease.

Novel findings broaden the concept of mechanotransduction (MT) in biophysically stimulated tissues such as the periodontium by considering nuclear MT, convergence of intracellular MT pathways, and mechanoresponsive cotranscription factors such as Yes-associated protein 1 (YAP1). Regarding periodontal disease, recent studies have elucidated the role of bacterial gingipain proteases in disturbing the barrier function of cadherins, thereby promoting periodontal inflammation. This leads to dysregulation of extracellular matrix homeostasis via proteases and changes the cell's biophysical environment, which leads to alterations in MT-induced cell behavior and loss of periodontal integrity. Newest experimental evidence from periodontal ligament cells suggests that the Hippo signaling protein YAP1, in addition to integrin-FAK (focal adhesion kinase) mechanosignaling, also regulates cell stemness. By addressing mechanosignaling-dependent transcription factors, YAP1 is involved in osteogenic and myofibroblast differentiation and influences core steps of autophagy. Recent in vivo evidence elucidates the decisive role of YAP1 in epithelial homeostasis and underlines its impact on oral pathologies, such as periodontitis-linked oral squamous cell carcinogenesis. Here, new insights reveal that YAP1 contributes to carcinogenesis via overexpression rather than mutation; promotes processes such as apoptosis resistance, epithelial-mesenchymal transition, or metastasis; and correlates with poor prognosis in oral squamous cell carcinoma. Furthermore, YAP1 has been shown to contribute to periodontitis-induced bone loss. Mechanistically, molecules identified to regulate YAP1-related periodontal homeostasis and disease include cellular key players such as MAPK (mitogen-activated protein kinase), JNK (c-Jun N-terminal kinase), Rho (Ras homologue) and ROCK (Rho kinase), Bcl-2 (B-cell lymphoma 2), AP-1 (activator protein 1), and c-myc (cellular myelocytomatosis). These findings qualify YAP1 as a master regulator of mechanobiology and cell behavior in human periodontal tissues. This review summarizes the most recent developments in MT-related periodontal research, thereby offering insights into outstanding research questions and potential applications of molecular or biophysical strategies aiming at periodontal disease mitigation or prevention.

N-Acetylcysteine modulates the effects of composites on human gingival keratinocytes.

OBJECTIVE: The aim of this study was to evaluate, if antioxidants, like N-Acetylcysteine, can modulate effects of composite eluates on human gingival keratinocytes. METHODS: Composite samples of ceram.x® universal, Filtek™ Supreme XTE, and Admira® Fusion were stored 72h in cell culture medium to prepare eluates, according to ISO 10993-12:2012. Human gingival keratinocytes were exposed to these eluates with or without 3mM N-Acetylcysteine. Following cell observation by iCELLigence®, exposure periods were determined at 1d and 4d. Cell morphological analysis combined with live/dead staining was performed. Tissue-specific biomarkers of terminal differentiation, Involucrin and Filaggrin, were analyzed by indirect immunofluorescence (IIF) and Western blot (WB). qPCR profiling was performed on genes encoding for: inflammation, apoptosis, turn-over of extracellular matrix, adhesion, proliferation and differentiation. For statistical analysis one-way Anova was used (p<0.05). RESULTS: Cells exposed to N-Acetylcysteine exhibited morphological changes but no cell death. After adding 3mM N-Acetylcysteine to HGK cultures, increased fluorescence intensity and protein amounts of Involucrin and Filaggrin indicated enhanced differentiation (p<0.05). Gene expression was modulated by: (i) composition of the composite eluates, (ii) NAC and (iii) exposure time. Filtek™ Supreme XTE showed a significant increased gene expression in inflammatory genes (p<0.05), which was amplified by the addition of NAC at 1d. Concerning exposure time, modulated gene expression showed eluate dependency, substantiated by Filtek™ Supreme XTE modulation at day 1 and Admira® Fusion at day 4. SIGNIFICANCE: N-Acetylcysteine-emerging effects on gingival keratinocytes were threefold: (i) increase of differentiation, (ii) modulation of composite-related effects and (iii) in parts counteraction of eluate-induced effects.

Electronic Cigarette Smoke Impairs Normal Mesenchymal Stem Cell Differentiation.

Electronic cigarettes (e-cigarettes) are promoted as low-risk alternatives to combustible cigarettes. However, the effects of chronic inhalation of potential toxicants emitted by ecigarettes remain largely unexamined. It is conceivable that smoking-induced chronic diseases result in cellular injury, in the absence of effective repair by stem cells. This study evaluates the effect of cigarette and e-cigarette aerosol extracts on the survival and differentiation of bone marrow-derived mesenchymal stem cells (MSCs). MSC growth and osteogenic differentiation were examined after exposure to smoke extracts. Data revealed detrimental effects of both cigarette and e-cigarette extracts on MSC morphology and growth. Levels and activity of alkaline phosphatase, an osteogenic marker, decreased and induction of osteoblastic differentiation was impaired. Both smoke extracts prevented osteogenic differentiation from progressing, evident by decreased expression of terminal osteogenic markers and mineralization. Elevated levels of reactive oxygen species (ROS) were detected in cells exposed to smoke extracts. Moreover, decreased differentiation potential was concomitant with severe down-regulation of Connexin 43 expression, leading to the loss of gap junction-mediated communication, which together with elevated ROS levels, could explain decreased proliferation and loss of differentiation potential. Hence, e-cigarettes present similar risk as combustible cigarettes with respect to tissue repair impairment.

Relationship between intensive care complications and costs and initial 24 h events of trauma patients with severe haemorrhage.

BACKGROUND: The correlation between the events occurring in the initial 24 h following traumatic injury and the outcome of patients presenting with hypovolaemic shock is not clear. METHODS: 27 patients who presented to a regional trauma centre with severe hypovolaemic shock were prospectively monitored. Evidence of severe hypovolaemia and shock was noted on admission with a mean systolic blood pressure of 73.8 mm Hg and a mean lactate level of 6.6 mM/l. The patients received a mean of 21.7 litres intravenous fluids during the first 24 h to maintain a mean systolic blood pressure >or=110 mm Hg and urine output of >or=50 ml/h. Multiple metabolic and physiological parameters were obtained prospectively and on an almost hourly basis for the first 24 h after admission. Patients were followed throughout their stay in hospital to record outcome, complications, total hospital costs and length of stay. RESULTS: Using regression and multivariate analysis, adult respiratory distress syndrome was correlated with hypothermia and persistent lactic acidosis (R(2) = 0.65, p = 0.005). Coagulopathy was associated with hypothermia (R(2) = 0.43, p = 0.04). Length of stay and cost of hospitalisation were highly related to intensive care unit days, hospital-acquired infections and ventilator days (R(2) = 0.86, p = 0.03). CONCLUSION: The initial 24 h events of trauma patients with haemorrhagic shock may have a significant impact on hospital costs and on complications developing later during hospitalisation.

Changes in resistances of endotracheal tubes with reductions in the cross-sectional area.

BACKGROUND AND OBJECTIVES: Partial obstruction of endotracheal tubes due to accumulation of secretions and mucus plugs can increase the tube resistance and subsequently impose increased resistive load on the patient. This study was performed to determine the changes in the resistance of endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm with different degrees and locations of endotracheal tube narrowing. METHODS: Reductions of 10%, 25%, 50% and 75% in the endotracheal tube's cross-sectional areas were created at different sites along the axes of the tube connected to an artificial lung. While ventilating with a constant inspiratory flow, a 1 s end-inspiratory occlusion manoeuvre was applied and the resulting plateau pressure was determined. The resistance was calculated as (peak airway pressure--plateau pressure)/peak inspiratory flow. RESULTS: Significant increases in the endotracheal tube's resistances were observed as the tube's cross-sectional area reduction was increased from 25% to 50% and from 50% to 75% for the 7.5 mm endotracheal tube, from 25% to 50% for the 8.0 mm endotracheal tube, and from 50% to 75% for the 8.5 mm endotracheal tube. Changes of the endotracheal tube resistances were not affected by the site of cross-sectional area reductions along the axes of the tubes. CONCLUSIONS: For endotracheal tubes of sizes 7.5, 8.0 and 8.5 mm, significant changes in the tubes resistances are observed when the partial obstructions of the tubes exceed certain critical values. The location of the partial obstruction did not affect the changes in the endotracheal tube resistances.

The effects of recombinant human thrombomodulin on endotoxin-induced multiple-system organ failure in rats.

Activation of the coagulation system is postulated to play an important role in the pathogenesis of endotoxin-induced tissue injury. Thrombomodulin (TM) is an endothelial cell membrane glycoprotein receptor for thrombin. Once bound to TM, thrombin loses its procoagulant activity, which results in decreased clotting. In addition, the binding of thrombin to TM activates the endogenous anticoagulant pathway through protein C. We studied the effect of recombinant human TM (rh-TM) on endotoxin-induced multiple-system organ failure (MSOF) in Sprague-Dawley rats weighing 400 to 450 g: 2 mg/kg of rh-TM was injected (T1/2 = 4.5 h) 30 min prior to intravenous injection of 20 mg/kg of Escherichia coli endotoxin. The study presented here consisted of three separate experiments. Experiment 1: 24-h survival study. Experiment 2: multiple-system organ microthrombi study in which 125I-human fibrinogen was injected 30 min prior to an endotoxin or saline injection and tissue microthrombi formation was assessed by measuring the percentage of organ radioactivity (lung, heart, liver, and kidney) against total injected radioactivity (microthrombi index, MI) 2.25 h after an endotoxin or saline injection. Experiment 3: endotoxin-induced MSOF study in which 125I-rat albumin was injected 5 h after an endotoxin or saline injection, and endotoxin-induced organ injury was evaluated by measuring tissue wet-to-dry ratios (W/D) and tissue-to-plasma 125I-rat albumin concentration ratios (T/P) 8 h after the endotoxin or saline injection. Blood contamination in samples from Experiments 2 and 3 was corrected by using 131I-rat albumin measurements. Pretreatment with rh-TM improved the survival from 12 h through 23 h as compared with that of the endotoxin control group (p < 0.05). However, at 24 h, after essentially all injected rh-TM had been eliminated, there was no difference in survival. Significant reductions in MI, W/D, and T/P in the organs sampled were observed in the rh-TM pretreated groups (p < 0.05). In conclusion, rh-TM improved short-term but not overall survival and decreased MSOF in endotoxemic rats.

Pulmonary mucormycosis presenting as an endobronchial lesion.

A 56-year-old diabetic man presented with left upper lobe collapse and postobstructive pneumonitis. Fiberoptic bronchoscopy revealed an endobronchial mass obstructing the left mainstem bronchus. The lesion resembled a bronchial adenoma; however, cytologic and histologic examination revealed invasive mucormycosis. The patient was treated with intravenous amphotericin B followed by endoscopic laser surgery that relieved the obstruction.

Wegener's granulomatosis presenting as right middle lobe obstruction.

Wegener's granulomatosis may present with a variety of findings and be difficult to diagnose. We report a case of a 55-year-old woman presenting with right middle lobe obstruction who was found to have limited Wegener's granulomatosis. Extensive medical evaluation was nondiagnostic and open lung biopsy specimens were required to establish the diagnosis.