Biomechanical force induces the growth factor production in human periodontal ligament-derived cells

Xanthohumol exerts anti-inflammatory effects in an in vitro model of mechanically stimulated cementoblasts

Xanthohumol (XN) is a prenylated plant polyphenol that naturally occurs in hops and its products, e.g. beer. It has shown to have anti-inflammatory and angiogenesis inhibiting effects and it prevents the proliferation of cancer cells. These effects could be in particular interesting for processes within the periodontal ligament, as previous studies have shown that orthodontic tooth movement is associated with a sterile inflammatory reaction. Based on this, the study evaluates the anti-inflammatory effect of XN in cementoblasts in an in vitro model of the early phase of orthodontic tooth movement by compressive stimulation. XN shows a concentration-dependent influence on cell viability. Low concentrations between 0.2 and 0.8 µM increase viability, while high concentrations between 4 and 8 µM cause a significant decrease in viability. Compressive force induces an upregulation of pro-inflammatory gene (Il-6, Cox2, Vegfa) and protein (IL-6) expression. XN significantly reduces compression related IL-6 protein and gene expression. Furthermore, the expression of phosphorylated ERK and AKT under compression was upregulated while XN re-established the expression to a level similar to control. Accordingly, we demonstrated a selective anti-inflammatory effect of XN in cementoblasts. Our findings provide the base for further examination of XN in modulation of inflammation during orthodontic therapy and treatment of periodontitis.

In Vitro Compression Model for Orthodontic Tooth Movement Modulates Human Periodontal Ligament Fibroblast Proliferation, Apoptosis and Cell Cycle

Human Periodontal Ligament Fibroblasts (hPDLF), as part of the periodontal apparatus, modulate inflammation, regeneration and bone remodeling. Interferences are clinically manifested as attachment loss, tooth loosening and root resorption. During orthodontic tooth movement (OTM), remodeling and adaptation of the periodontium is required in order to enable tooth movement. hPDLF involvement in the early phase-OTM compression side was investigated for a 72-h period through a well-studied in vitro model. Changes in the morphology, cell proliferation and cell death were analyzed. Specific markers of the cell cycle were investigated by RT-qPCR and Western blot. The study showed that the morphology of hPDLF changes towards more unstructured, unsorted filaments under mechanical compression. The total cell numbers were significantly reduced with a higher cell death rate over the whole observation period. hPDLF started to recover to pretreatment conditions after 48 h. Furthermore, key molecules involved in the cell cycle were significantly reduced under compressive force at the gene expression and protein levels. These findings revealed important information for a better understanding of the preservation and remodeling processes within the periodontium through Periodontal Ligament Fibroblasts during orthodontic tooth movement. OTM initially decelerates the hPDLF cell cycle and proliferation. After adapting to environmental changes, human Periodontal Ligament Fibroblasts can regain homeostasis of the periodontium, affecting its reorganization.

Gene expression and phosphorylation of ERK and AKT are regulated depending on mechanical force and cell confluence in murine cementoblasts

Cementoblasts, located on the tooth root surface covered with cementum, are considered to have tooth protecting abilities. They prevent tissue damage and secure teeth anchorage inside the periodontal ligament during mechanical stress. However, the involvement of cementoblasts in mechanical compression induced periodontal remodeling needs to be identified and better understood. Here, we investigated the effect of static compressive stimulation, simulating the compression side of orthodontic force and cell confluence on a murine cementoblast cell line (OC/CM). The influence of cell confluence in cementoblast cells was analyzed by MTS assay and immunostaining. Furthermore, mRNA and protein expression were investigated by real-time RT-PCR and western blotting at different confluence grades and after mechanical stimulation. We observed that cementoblast cell proliferation increases with increasing confluence grades, while cell viability decreases in parallel. Gene expression of remodeling markers is regulated by compressive force. In addition, cementoblast confluence plays a crucial role in this regulation. Confluent cementoblasts show a significantly higher basal expression of Bsp, Osterix, Alpl, Vegfa, Mmp9, Tlr2 and Tlr4 compared to sub-confluent cells. After compressive force of 48 h at 60% confluence, an upregulation of Bsp, Osterix, Alpl, Vegf and Mmp9 is observed. In contrast, at high confluence, all analyzed genes were downregulated through mechanical stress. We also proved a regulation of ERK, phospho-ERK and phospho-AKT dependent on compressive force. In summary, our findings provide evidence that cementoblast physiology and metabolism is highly regulated in a cell confluence-dependent manner and by mechanical stimulation.

TGF-β-induced activation of conjunctival fibroblasts is modulated by FGF-2 and substratum stiffness

Purpose

This study aimed to investigate the effects of substratum stiffness on the sensitivity of human conjunctival fibroblasts to transforming growth factor (TGF)-β, and to explore the molecular mechanism of action.

Methods

Human conjunctival fibroblasts were cultured on collagen-coated plastic or silicone plates. The stiffness of the silicone plates was 0.2 or 64 kPa. Cells were treated by 2.5 ng/mL TGF-β2 with or without fibroblast growth factor (FGF)-2 (0–100 ng/mL) for 24 h or 48 h. The protein expression levels were determined by Western blot analysis. Cell proliferation was assessed using the WST-8 assay.

Results

FGF-2 suppressed the TGF-β-induced expression of α-smooth muscle actin (SMA) and collagen type I (Col I), but not fibronectin (FN). Both FGF-2 and TGF-β2 increased cell proliferation without an additive effect. The induction of α-SMA by TGF-β2 was decreased on the soft substratum, without any change in the expression level or subcellular location of Yes-associated protein/transcriptional coactivator with PDZ-binding motif (YAP/TAZ). FGF-2 suppressed TGF-β-induced α-SMA expression even on the soft substratum.

Conclusions

FGF-2 treatment and a soft substratum suppressed TGF-β-induced transdifferentiation of conjunctival fibroblasts into myofibroblasts. FGF-2 attenuated the TGF-β-induced expression of α-SMA, even on a soft substratum.

Effects of mechanical stress on human oral mucosa-derived cells

OBJECTIVES

Placement of a denture results in the application of mechanical stress (MS), such as occlusal force, onto the oral mucosa beneath the denture. To better understand the molecular mechanism underlying MS-induced inflammation in the oral mucosa, we examined the impact of MS on human oral epithelial cells (HO-1-N-1) and human fibroblasts (HGFs) in this study.

MATERIALS AND METHODS

MS was applied on HO-1-N-1 and HGFs using a hydrostatic pressure apparatus. The expression and production of inflammatory cytokines and growth factors were examined by real-time RT-PCR and ELISA. MS-induced intracellular signal transduction via MAP kinase (MAPK) was also examined.

RESULTS

1 MPa MS resulted in a significant increase in inflammatory cytokines, and 3 MPa MS resulted in a significant increase in FGF-2. MS also increased p-38 phosphorylation and the addition of a p-38 inhibitor significantly suppressed the production of inflammatory cytokines.

DISCUSSION

Our study suggested that MS applied through a denture increases the production of inflammatory cytokines from oral mucosal epithelial cells and fibroblasts via the p38 MAPK cascade. These responses to MS likely lead to inflammation of the mucosal tissue beneath dentures. On other hand, up-regulation of growth factors is likely a manifestation of the biological defense mechanism against excessive MS.

Estimation of Cadaveric Age by Ultrasonography

(1) Background: While decreasing bone mineral density (BMD) with age in living people has been well documented, a correlation between age and bone mineral density in deceased people has only been reported in a few studies. A correlation between age and BMD in deceased people was investigated as an objective tool for age estimation of unidentified remains. (2) Methods: The Bone Area Ratio (BAR) was measured in 402 autopsy cases (143 females and 259 males over the age of 20). (3) Results: The correlation coefficient in the females was r = -0.5476, and the correlation coefficient in the males was r = -0.2166, indicating a stronger correlation in females than in males. A comparison of the BAR values in the deceased females for each age group with that in live females found no significant differences in the BAR values. BAR values in the deceased were similar to in live individuals, and this did not change with duration of the postmortem interval. (4) Conclusions: Measuring the BAR value based on bone mass using ultrasonic waves is rapid and easy, even for those lacking forensic training, and may be used to estimate the age of an individual and the likelihood of fracture due to trauma.

Selection and validation of reference genes by RT-qPCR for murine cementoblasts in mechanical loading experiments simulating orthodontic forces in vitro

Different structures and cell types of the periodontium respond to orthodontic tooth movement (OTM) individually. Cementoblasts (OC/CM) located in the immediate vicinity of the fibroblasts on the cement have found way to the centre of actual research. Here, we identify and validate possible reference genes for OC/CM cells by RT-qPCR with and without static compressive loading. We investigated the suitability of 3 reference genes in an in vitro model of cementoblast cells using four different algorithms (Normfinder, geNorm, comparative delta-Ct method and BestKeeper) under different confluences and time. Comparable to our previous publications about reference genes in OTM in rats and human periodontal ligament fibroblasts (hPDLF), Rpl22 in murine OC/CM cells appears as the least regulated gene so that it represents the most appropriate reference gene. Furthermore, unlike to the expression of our recommended reference genes, the expression of additionally investigated target genes changes with confluence and under loading compression. Based on our findings for future RT-qPCR analyses in OC/CM cells, Rpl22 or the combination Rpl22/Tbp should be favored as reference gene. According to our results, although many publications propose the use of Gapdh, it does not seem to be the most suitable approach.

Transplantation of dental pulp-derived cell sheets cultured on human amniotic membrane induced to differentiate into bone

OBJECTIVE

The usefulness of the amniotic membrane as a cell culture substrate has led to its use in the development of dental pulp-derived cell sheets. We induced osteoblastic differentiation of dental pulp-derived cell sheets and conducted histological and immunological examinations in addition to imaging assessments for regeneration of bone defects.

METHODS

Dental pulp cells were obtained by primary culture of the dental pulp tissue harvested from extracted wisdom teeth. These cells were maintained for three to four passages. Subsequently, the dental pulp cells were seeded onto an amniotic membrane to produce dental pulp-derived cell sheets. Following the induction of osteoblastic differentiation, the sheets were grafted into the subcutaneous tissue of the lower back and maxillary bone defect of a nude mouse. Histological and immunological examinations of both grafts were performed.

RESULTS

Dental pulp-derived cell sheets cultured on an osteoblast differentiation-inducing medium demonstrated resemblance to dental pulp tissue and produced calcified tissue. Mineralization was maintained following grafting of the sheets. Regeneration of the maxillary bone defect was observed.

CONCLUSION

Induction of osteoblastic differentiation of the dental pulp-derived cell sheets may be indicated for the regeneration of periodontal tissue.

Notch Signaling Participates in TGF-β-Induced SOST Expression Under Intermittent Compressive Stress

Notch signaling is regulated by mechanical stimuli in various cell types. It has previously been reported that intermittent compressive stimuli enhanced sclerostin (SOST) expression in human periodontal ligament cells (hPDLs) by regulating transforming growth factor-β (TGF-β) expression. The aim of the present study was to determine the involvement of Notch signaling in the TGF-β-induced SOST expression in hPDLs. Cells were treated with intermittent compressive stress in a computer-controlled apparatus for 24 h. The mRNA and protein expression of the cells were determined by real-time polymerase chain reaction and Western blot analysis, respectively. In some experiments, the target signaling pathway was impeded by the addition of a TGF-β receptor kinase inhibitor (SB431542) or a γ-secretase inhibitor (DAPT). The results demonstrated that hPDLs under intermittent compressive stress exhibited significantly higher NOTCH2, NOTCH3, HES1, and HEY1 mRNA expression compared with control, indicating that mechanical stress induced Notch signaling. DAPT pretreatment markedly reduced the intermittent stress-induced SOST expression. The expression of NOTCH2, NOTCH3, HES1, and HEY1 mRNA under compressive stress was significantly reduced after pretreatment with SB431542, coinciding with a reduction in SOST expression. Recombinant human TGF-β1 enhanced SOST, Notch receptor, and target gene expression in hPDLs. Further, DAPT treatment attenuated rhTGF-β1-induced SOST expression. In summary, intermittent compressive stress regulates Notch receptor and target gene expression via the TGF-β signaling pathway. In addition, Notch signaling participates in TGF-β-induced SOST expression in hPDLs. J. Cell. Physiol. 232: 2221-2230, 2017. © 2016 Wiley Periodicals, Inc.