Fabrication of Hydrogen Boride Thin Film by Ion Exchange in MgB2.

In this study, hydrogen boride films are fabricated by ion-exchange treatment on magnesium diboride (MgB2) films under ambient temperature and pressure. We prepared oriented MgB2 films on strontium titanate (SrTiO3) substrates using pulsed laser deposition (PLD). Subsequently, these films were treated with ion exchangers in acetonitrile solution. TOF-SIMS analysis evidenced that hydrogen species were introduced into the MgB2 films by using two types of ion exchangers: proton exchange resin and formic acid. According to the HAXPES analysis, negatively charged boron species were preserved in the films after the ion-exchange treatment. In addition, the FT-IR analysis suggested that B-H bonds were formed in the MgB2 films following the ion-exchange treatment. The ion-exchange treatment using formic acid was more efficient compared to the resin treatment; with respect to the amount of hydrogen species introduced into the MgB2 films. These ion-exchanged films exhibited photoinduced hydrogen release as observed in a powder sample. Based on the present study, we expect to be able to control the morphology and hydrogen content of hydrogen boride thin films by optimising the ion-exchange treatment process, which will be useful for further studies and device applications.

Temperature dependence on bandgap of semiconductor photocatalysts.

Light irradiation onto a semiconductor generates heat; however, its electronic structure under high temperature has not yet been well investigated. In this study, we have carefully examined the temperature dependence on the bandgap of simple metal oxides, which are well-known photocatalysts, i.e., TiO2, CeO2, Nb2O5, SnO2 Ta2O5, WO3, ZnO, and ZrO2, using operando UV-visible spectroscopy under controlled temperature (from room temperature to 500 °C). Consequently, a linear decrease in bandgap was seen as a function of temperature with a different slope for each semiconductor. We found that the slope was dependent on the bonding distance between metal and oxygen. This finding is essential to develop a photocatalyst used under the condition involving photo-thermal effect.

The C-terminus of amelogenin enhances osteogenic differentiation of human cementoblast lineage cells.

BACKGROUND AND OBJECTIVES: Amelogenin proteins are the major constituent of developing extracellular enamel matrix and are believed to have an exclusively epithelial origin. Recent studies have suggested that amelogenins might induce the differentiation and maturation of various cells, including cementoblast lineage cells. However, the residues comprising the active site of amelogenin remain unclear. The purpose of this study was to identify the active site region of amelogenin by studying the effects of amelogenin fragments on the osteogenic differentiation of cementoblasts. MATERIAL AND METHODS: Amelogenin fragments lacking the C-terminus (rh163) and N-terminus (rh128) and a fragment consisting of the C-terminal region of rh174 (C11 peptide) were synthesized and purified. Human cementoblast lineage cells were cultured in osteogenic differentiation medium and treated with 0, 10, 100 or 1000 ng/mL of rh163, rh128 or C11 peptide. The mRNA levels of bone markers were examined by real-time polymerase chain reaction analysis. Alkaline phosphatase activity and calcium deposition were also determined. Mineralization was evaluated by alizarin red staining. RESULTS: The osteogenic differentiation of human cementoblast lineage cells was significantly enhanced by treatment with rh128 or C11 peptide, whereas rh163 had no significant effect as compared with untreated controls. CONCLUSIONS: The C-terminus of amelogenin promotes the osteogenic differentiation of human cementoblast lineage cells, indicating the possible utility of C11 peptide in periodontal tissue regeneration.

The FGFR1 inhibitor PD173074 induces mesenchymal-epithelial transition through the transcription factor AP-1.

BACKGROUND: Epithelial-mesenchymal transition (EMT) is a crucial process in cancer progression that provides cancer cells with the ability to escape from the primary focus, invade stromal tissues and migrate to distant regions. Cell lines that lack E-cadherin show increased tumorigenesis and metastasis, and the expression levels of E-cadherin and Snail correlate inversely with the prognosis of patients suffering from breast cancer or oral squamous cell carcinoma (OSCC). Moreover, recent studies have shown that most EMT cases are regulated by soluble growth factors or cytokines. Among these factors, fibroblast growth factors (FGFs) execute diverse functions by binding to and activating members of the FGF receptor (FGFR) family, including FGFR1-4. Fibroblast growth factor receptor 1 is an oncoprotein that is involved in tumorigenesis, and PD173074 is known to be a selective inhibitor of FGFR1. However, the roles of FGFR1 and FGFR1 inhibitors have not yet been examined in detail. METHODS: Here, we investigated the expression of FGFR1 in head and neck squamous cell carcinoma (HNSCC) and the role of the FGFR1 inhibitor PD173074 in carcinogenesis and the EMT process. RESULTS: Fibroblast growth factor receptor 1 was highly expressed in 54% of HNSCC cases and was significantly correlated with malignant behaviours. Nuclear FGFR1 expression was also observed and correlated well with histological differentiation, the pattern of invasion and abundant nuclear polymorphism. Fibroblast growth factor receptor 1 was also overexpressed in EMT cell lines compared with non-EMT cell lines. Furthermore, treatment of HOC313 cells with PD173074 suppressed cellular proliferation and invasion and reduced ERK1/2 and p38 activation. These cells also demonstrated morphological changes, transforming from spindle- to cobble stone-like in shape. In addition, the expression levels of certain matrix metalloproteinases (MMPs), whose genes contain activator protein-1 (AP-1) promoter sites, as well as Snail1 and Snail2 were reduced following PD173074 treatment. CONCLUSION: Taken together, these data suggest that PD173074 inhibits the MAPK pathway, which regulates the activity of AP-1 and induces MET. Furthermore, this induction of MET likely suppresses cancer cell growth and invasion.

Glue embolization for gastroduodenal ulcer bleeding: contribution to hemodynamics and healing process.

BACKGROUND: Although the morbidity of bowel ischemic events after glue embolization has been suggested, a causal relationship between glue and ischemia has not been clearly established. PURPOSE: To evaluate the efficiency and safety of transcatheter arterial embolization with n-butyl cyanoacrylate (NBCA-TAE) for upper gastrointestinal hemorrhage (GIH). MATERIAL AND METHODS: Between October 2006 and October 2012, 21 patients with upper GIH underwent NBCA-TAE, and endoscopic data were obtained within 30 days of follow-up. Shock index prior to and immediately after NBCA-TAE were compared to determine changes in hemodynamics. Days to Forrest type III, as assessed by follow-up endoscopy, was used as an indicator of the healing process. Other clinical outcomes included days for starting ingestion and for hospital discharge. RESULTS: Sixteen gastric and five duodenal ulcers, classified into Forrest type I, were treated. Immediate hemostasis was achieved in all the patients, and no re-bleeding occurred within the follow-up period. Shock index significantly (P < 0.001) improved from before (0.99 ± 0.076) to immediately after NBCA-TAE (0.67 ± 0.038). Sequential mucosal healing processes were observed in all the patients, and the number of days to Forrest type III was 9.6 ± 7.1. The number of days for starting ingestion and hospital discharge was 9.0 ± 4.5 and 15 ± 7.7 days, respectively. CONCLUSION: NBCA-TAE is an effective and safe method for the control of nonvariceal upper GIH, in terms of contribution to hemodynamics and healing process of the gastroduodenal mucosa.

Lipopolysaccharide induces rapid loss of follicular dendritic cell-secreted protein in the junctional epithelium.

UNLABELLED: Oshiro A, Iseki S, Miyauchi M, Terashima T, Kawaguchi Y, Ikeda Y, Shinomura T. Lipopolysaccharide induces rapid loss of follicular dendritic cell-secreted protein in the junctional epithelium. J Periodont Res 2012; 47: 689-694. © 2012 John Wiley & Sons A/S Background and Objective: We have previously reported that mRNA encoding follicular dendritic cell-secreted protein (FDC-SP) is expressed specifically in the junctional epithelium at the gingival crevice. Other tissues, such as tonsil, prostate gland and trachea, also express high levels of FDC-SP. These tissues participate in a range of functions closely related to innate immunity. Therefore, it is hypothesized that FDC-SP plays a crucial role in close association with the host defense system within the gingival crevice. Accordingly, the main aim of this study was to investigate the expression and localization of FDC-SP in and around the junctional epithelium and to observe the dynamic changes of FDC-SP in experimental inflammation. MATERIAL AND METHODS: We examined, immunohistochemically, the expression of FDC-SP in the junctional epithelium using a specific antibody raised in rabbit after immunization with a synthetic peptide derived from the hydrophilic region of FDC-SP. Experimental inflammation was induced in the upper molars of Wistar rats by applying bacterial lipopolysaccharide (LPS; 5 mg/mL in sterile saline) for 1 h. RESULTS: We confirmed that FDC-SP is present in the junctional epithelium in a pattern that is consistent with the expression of FDC-SP mRNA. Of special interest is that no FDC-SP was detectable in the junctional epithelium 3 h after transient topical treatment with LPS. CONCLUSION: The presence of FDC-SP in the junctional epithelium and its loss after LPS treatment strongly support our hypothesis of FDC-SP playing a crucial role in close association with the host defense system within the gingival crevice.

Topical application of Aggregatibacter actinomycetemcomitans cytolethal distending toxin induces cell cycle arrest in the rat gingival epithelium in vivo.

BACKGROUND: Aggregatibacter actinomycetemcomitans is one of the etiological pathogens implicated in the onset of periodontal disease. This pathogen produces cytolethal distending toxin (CDT) that acts as a genotoxin to induce cell cycle arrest and cellular distension in cultured cell lines. Therefore, CDT is a possible virulence factor; however, the in vivo activity of CDT on periodontal tissue has not been explored. Here, CDT was topically applied into the rat molar gingival sulcus; and the periodontal tissue was histologically and immunohistochemically examined. MATERIALS AND METHODS: Recombinant purified A. actinomycetemcomitans CDT was applied to gingival sulcus of male Wistar rats and tissue samples were immunohistochemmically examined. RESULTS: One day after application, infiltration of neutrophils and dilation of blood vessels in the gingival connective tissue were found. At day three, desquamation and detachment of cells in the junctional epithelium was observed. This abrasion of junctional epithelium was not observed in rats treated with mutated CDT, in which a His274Ala mutation is present in the CdtB subunit. This indicates the tissue abrasion may be caused by the genotoxicity of CdtB. Expression of the proliferating cell nuclear antigen (PCNA), a marker for proliferating cells, was significantly suppressed using CDT treatment in the junctional epithelium and gingival epithelium. CONCLUSION: Using the rat model, these data suggest CDT intoxication induces cell cycle arrest and damage in periodontal epithelial cells in vivo.

Ultrasound stimulation attenuates root resorption of rat replanted molars and impairs tumor necrosis factor-α signaling in vitro.

BACKGROUND AND OBJECTIVE: A therapeutic protocol to minimize root resorption induced by tooth replantation has not yet been universally established. In this context, noninvasive modality such as ultrasound therapy have been a focus of increased interest. This study aimed to evaluate the inhibitory effect of ultrasound therapy on root resorption of replanted rat molars. In addition, the study aimed to promote insights into the mechanism through which ultrasound mediates the metabolism of periodontal cells in vitro. MATERIAL AND METHODS: An experimental model of tooth replantation in rats, involving luxation and immediate replacement of the maxillary first molars, was used to assess the inhibitory effect of an ultrasound-therapy regimen (15 min of exposure to ultrasound, each day for 21 d) on root resorption. Moreover, the effect of ultrasound on osteoclastogenesis/cementoclastogenesis was examined in vitro using a mouse osteoblastic stromal cell line (ST2) and a mouse cementoblastic cell line (OCCM-30). RESULTS: The area of root resorption lacunae was statistically decreased (p < 0.01) in the ultrasound-treated sample. In addition, immunohistochemical staining, using murine TNF-α polyclonal antibody, failed to detect tumor necrosis factor-α (TNF-α) protein in the ultrasound-treated sample compared with the control. An in vitro study showed that the lipopolysaccharide (LPS)-induced expression of Tnfalpha mRNA was significantly reduced by ultrasound therapy in both osteoblastic and cementoblastic cells. Moreover, the TNF-α-induced up-regulation of Rankl mRNA was also inhibited by ultrasound. CONCLUSION: Ultrasound may contribute to the reduction of the trauma-induced inflammatory reaction through impairment of the TNF-α signaling pathway. It is therefore suggested that ultrasound shows potential as a therapeutic tool to optimize the regenerative potential of periodontal tissues on replanted teeth.

Effects of mechanical stimulation by a powered toothbrush on the healing of periodontal tissue in a rat model of periodontal disease.

BACKGROUND AND OBJECTIVE: Elimination of pathogens is the main aim of periodontal treatment; however, modulation of the host immune response should also be considered. This study aimed to evaluate the effects of mechanical stimulation on periodontal healing in rats. MATERIAL AND METHODS: Before starting the experiment, lipopolysaccharide and proteases were applied once a day, for 4 wk, to both maxillary first molars of 30 rats to induce periodontal disease, and the application was stopped at the end of the 4-wk period. The experiment started immediately following this pretreatment. In the experiment, the left palatal gingiva was stimulated once daily using a powered toothbrush and the right gingiva served as a control (no mechanical stimulation). Pathological changes, and proliferation and cell death in periodontal tissues, were evaluated histometrically and immunohistochemically at baseline (0 wk), and at 1 and 3 wk of stimulation. RESULTS: The control showed a reduction of polymorphonuclear leukocyte infiltration in connective tissue and an increase in the numbers of gingival and periodontal ligament fibroblasts. Mechanical stimulation reduced polymorphonuclear leukocyte infiltration and the area of destroyed collagen in connective tissue, and increased the number of gingival fibroblasts; however, it had no effect on alveolar bone and root resorption or on the number of periodontal ligament fibroblasts. CONCLUSION: Mechanical stimulation accelerated the healing of gingival inflammation by reducing the infiltration of polymorphonuclear leukocytes and enhancing fibroblast proliferation and collagen synthesis.

DFF45/ICAD restores cisplatin-induced nuclear fragmentation but not DNA cleavage in DFF45-deficient neuroblastoma cells.

We have previously defined a homozygously deleted region at chromosome 1p36.2-p36.3 in human neuroblastoma cell lines, NB-1 and NB-C201, and identified six genes including DFF45/ICAD within this region. In this study, we found that NB-C201 cells are much more resistant to various genotoxic stresses such as cisplatin (CDDP) than CHP134 and SH-SY5Y cells that do not have the homozygous deletion. To examine a role(s) of DFF45 in the regulation of apoptosis in response to CDDP, we have established stably DFF45-expressing NB-C201 cell clones (DFF45-1 and DFF45-3) and a control cell clone (NB-C201-C) using a retrovirus-mediated gene transfer. In contrast to NB-C201-C cells, DFF45-3 cells displayed apoptotic nuclear fragmentation in response to CDDP. Although CDDP-induced proteolytic cleavage of procaspase-3 and DFF45 in DFF45-3 cells, we could not detect a typical apoptotic DNA fragmentation. Additionally, deletion analysis revealed that C-terminal region of DFF45 is required for inducing nuclear fragmentation. Unexpectedly, (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays demonstrated that DFF45 has undetectable effect on CDDP sensitivity of NB-C201 cells. Taken together, our present results suggest that DFF45/DFF40 system may be sufficient for CDDP-induced nuclear fragmentation but not DNA cleavage.

An investigation of 2,093 renal biopsies performed at Tokai University Hospital between 1976 and 2000.

We retrospectively investigated 2,093 renal biopsy procedures performed between 1976 and 2000 at Tokai University Hospital. The study period was divided into 5-year intervals, and the frequencies of each renal disease, age and sex of patients were compared across the study period. Clinical diagnosis was based on WHO criteria. A total of 2,093 patients aged 8 months to 84 years underwent renal biopsy during the study period. The percentage of elderly patients who underwent renal biopsy increased from 1.2% in 1976 - 1980 to 9.9% in 1996 - 2000. IgAN was the most common disease in every 5-year period. CresGN showed an increase from 1 patient (0.3%) in 1976 - 1980 to 15 patients (4.0%) in 1996 - 2000. In contrast, the number of patients with PGN or BRH, MPGN significantly decreased during the study period. Although the criteria for renal biopsy and renal diseases detected are expected to change in the future, renal biopsy will remain an essential procedure for making a definite diagnosis, selection of optimum treatment, and prediction of prognosis.

Effects of ultrasound on the proliferation and differentiation of cementoblast lineage cells.

BACKGROUND: The purpose of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) stimulation on the proliferation and differentiation of cementoblast lineage cells. METHODS: An immortalized human periodontal ligament cell line (HPL) showing immature cementoblastic differentiation was used. Cultured HPL cells were subjected to LIPUS exposure (frequency = 1 MHz; pulsed 1:4; intensity = 30 mW/cm(2)) or sham exposure for 15 minutes per day. Expression levels of alkaline phosphatase (ALP), type I collagen (Col-I), runt-related gene 2 (Runx2), bone sialoprotein (BSP), osteocalcin (OCN), and osteopontin (OPN) mRNA were analyzed with real-time polymerase chain reaction analysis. Furthermore, ALP activity, collagen synthesis, and protein level of Runx2 were examined after 6 days of LIPUS exposure. RESULTS: mRNA and protein levels of ALP, Col-I, and Runx2 were significantly increased by LIPUS exposure compared to controls, whereas BSP, OCN, and OPN mRNA expression could not be detected in HPL cells, irrespective of LIPUS exposure. CONCLUSION: LIPUS enhanced ALP activity, collagen synthesis, and Runx2 expression of HPL cells, which provides important insight into the promotion of early cementoblastic differentiation of immature cementoblasts.

Tissue inhibitor of metalloproteinase-1 promotes cell proliferation through YAP/TAZ activation in cancer.

Tissue inhibitor of metalloproteinase-1 (TIMP-1), a member of the TIMP family (TIMP-1 to 4), is highly expressed in various types of cancer and forms a complex with its receptor CD63 and Integrin ß1. However, the precise oncogenic mechanism of TIMP-1 remains unclear. Yes-associated protein (YAP) and transcriptional co-activator with PDZ binding motif (TAZ) are transcription co-activators enhancing the transcription of specific genes related to cell proliferation. But the mechanism of aberrant YAP/TAZ activation in cancer is not fully understood. Here, we showed that TIMP-1 activates YAP/TAZ as novel downstream targets to promote cell proliferation. The TIMP-1-CD63-Integrin ß1 axis activates Src and promotes RhoA-mediated F-actin assembly, leading to LATS1/2 inactivation. This results in under-phosphorylation, protein stabilization and nuclear translocation of YAP/TAZ (YAP/TAZ activation); CTGF production; and cell proliferation. Furthermore, the TIMP-1-YAP/TAZ axis is aberrantly activated in various types of cancer cells or tissues. TIMP-1 knockdown inhibits cell proliferation through YAP/TAZ inactivation in cancer cells. This study found that TIMP-1 accelerates cell proliferation through YAP/TAZ activation in cancer, and suggests the TIMP-1-YAP/TAZ axis may be a novel potential drug target for cancer patients.

Hippocampal volumes and diffusion-weighted image findings in children with prolonged febrile seizures.

OBJECTIVES: To assess hippocampal volumes (HV) and signal changes on diffusion-weighted imaging (DWI) within 5 days of prolonged febrile seizures (PFS) and compare them with the PFS duration and EEG. METHODS: We studied 12 children (mean age: 32 +/- 21 months, range 10 months-5 years) within 5 days of a first episode of PFS (a seizure or series of seizures lasting for 30 min or longer, without return of consciousness between the seizures). The HV measurements were carried out using high-resolution magnetic resonance imaging and signal intensity abnormalities were evaluated visually on DWI. HV in patients were compared with those of 13 neurologically normal controls (mean age 31 +/- 16 months, range 15 months-5 years). HV abnormalities correlated with PFS duration. HV and DWI abnormalities were compared with EEG abnormalities. RESULTS: Seizure duration ranged from 40 to 95 min. In seven out of twelve patients, seizures were refractory and lasted for 60 min or longer despite intravenous infusion of diazepam. In the patients with PFS for 60 min or longer, HV were significantly larger than that of controls. In all patients, there was a positive correlation between HV and seizure duration. DWI showed hyperintensity in unilateral hippocampus in three patients with intractable seizures, ipsilateral thalamus in two, and cingulate in one. EEG showed abnormalities in temporal areas ipsilateral to the DWI abnormalities in these patients. CONCLUSIONS: Large HV and hippocampal hyperintensity on DWI were seen in patients with refractory PFS. Our results suggest that medically refractory PFS lasting for 60 min or longer may cause structural changes in limbic structures that could promote later epileptogenesis.

PGE2 activates cementoclastogenesis by cementoblasts via EP4.

Destruction of cementum and alveolar bone is the main causative event for the exfoliation of teeth as a consequence of periodontitis. Prostaglandin E(2) (PGE(2)) and PGE receptor subtypes (EPs) play an important role in modulating osteoblast-mediated osteoclastogenesis; however, no information is available on the role of PGE(2) and EPs in regulating cementoblast-mediated cementoclastogenesis. We hypothesized that the PGE(2)-EPs pathway also regulates cementoblasts' ability to activate cementoclasts. For these studies, OCCM-30 cells (a mouse cementoblast cell line) were exposed to PGE(2) and specific EP agonists. PGE(2) (100 ng/mL) and EP4 agonist (1 microM) up-regulated RANKL and IL-6 mRNA levels, while they down-regulated OPG mRNA expression. The EP4 antagonist (1 microM) eliminated these effects of PGE(2). PGE(2) treatment of co-cultures of OCCM-30 cells with bone marrow cells induced TRAP-positive cells via the EP4 pathway. These findings suggest that PGE(2) promotes cementoblast-mediated cementoclastogenesis by regulating the expression of RANKL and OPG via the EP4 pathway.

Hippocampal volumes and diffusion-weighted image findings in children with prolonged febrile seizures.

OBJECTIVES: To assess hippocampal volumes (HV) and signal changes on diffusion-weighted imaging (DWI) within 5 days of prolonged febrile seizures (PFS) and compare them with the PFS duration and EEG. METHODS: We studied 12 children (mean age: 32 +/- 21 months, range 10 months-5 years) within 5 days of a first episode of PFS (a seizure or series of seizures lasting for 30 min or longer, without return of consciousness between the seizures). The HV measurements were carried out using high-resolution magnetic resonance imaging and signal intensity abnormalities were evaluated visually on DWI. HV in patients were compared with those of 13 neurologically normal controls (mean age 31 +/- 16 months, range 15 months-5 years). HV abnormalities correlated with PFS duration. HV and DWI abnormalities were compared with EEG abnormalities. RESULTS: Seizure duration ranged from 40 to 95 min. In seven out of twelve patients, seizures were refractory and lasted for 60 min or longer despite intravenous infusion of diazepam. In the patients with PFS for 60 min or longer, HV were significantly larger than that of controls. In all patients, there was a positive correlation between HV and seizure duration. DWI showed hyperintensity in unilateral hippocampus in three patients with intractable seizures, ipsilateral thalamus in two, and cingulate in one. EEG showed abnormalities in temporal areas ipsilateral to the DWI abnormalities in these patients. CONCLUSIONS: Large HV and hippocampal hyperintensity on DWI were seen in patients with refractory PFS. Our results suggest that medically refractory PFS lasting for 60 min or longer may cause structural changes in limbic structures that could promote later epileptogenesis.

Characteristics of periodontal ligament subpopulations obtained by sequential enzymatic digestion of rat molar periodontal ligament.

Periodontal ligament (PDL) consists of different cell populations in various differentiation stages. In the present study, we isolated cell populations from rat molar PDL by sequential enzymatic digestion and characterized growth potential and mineralization activity of the PDL subpopulations (PDL-SP) to throw light on the mechanism of PDL remodeling and, in its turn, periodontal tissue regeneration. PDL attached to extracted rat molars was digested 2 mg/ml collagenase and 0.25% trypsin at 37 degrees C for 30 min. Then four consecutive digestions were performed for 20 min each in a fresh digestive solution. The solutions were centrifuged to collect released cells and 5 PDL subpopulations (30M-, 50M-, 70M-, 90M-and 110M-PDL-SP) were obtained. Light microscopic observation showed that about a half of PDL in width attached on the root surface of extracted teeth and 30M-PDL-SP was considered to contain cells mainly from middle portion of PDL. Scanning electron microscopic examination indicated that 110M-PDL-SP was enriched by root lining cementoblastic cells. 30M-PDL-SP showed a high level of proliferative activity. Although the growth potential of a subpopulation decreased in PDL-SP toward the root surface, 110M-PDL-SP had a high proliferative activity equivalent to that of 30M-PDL-SP. Analyses of alkaline phosphatase (ALP) and mineralization activities showed that higher activities in PDL-SP toward the surface of roots and that 110M-PDL-SP had the highest activity of ALP and the largest number of mineralization nodules. The present study shows as supposed by previous studies on cell kinetics in PDL that subpopulations with larger growth potential were generally located in the middle portion of PDL and those with higher mineralization activities toward the surface of the roots. It is suggested, however, that a possible pathway of PDL cell turnover may exist within the PDL-SP on the root surface in addition to the generally recognized pathway from the middle area of PDL to root surface.

Effects of endogenous and exogenous prostaglandin E2 on the proliferation and differentiation of a mouse cementoblast cell line (OCCM-30).

BACKGROUND: Cementum formation is considered to be a critical event for successful regeneration of periodontal tissues. Cementoblasts share many characteristics with osteoblasts. Prostaglandin E(2) (PGE(2)) is an important local factor in bone metabolism. Although the effects of PGE(2) on osteoblasts are well known, its effects on cementoblasts have not yet been established. We examined the effects of PGE(2) on proliferation and differentiation in a mouse cementoblast cell line, OCCM-30 cells. METHODS: OCCM-30 cells were treated with three concentrations of PGE(2) (10, 100, and 1,000 ng/ml). Cell number, alkaline phosphatase (ALP) activity, and expression for mineralization-related genes were determined. Osteoprotegerin (OPG) and receptor activator of nuclear factor-kappa B (NF-kappaB) ligand (RANKL) expression were also examined by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). RESULTS: The addition of PGE(2) at the highest dose used in this study suppressed cell proliferation of OCCM-30 cells. The expression of mineralization-related marker mRNA, such as type 1 collagen, ALP, bone sialoprotein (BSP), and osteocalcin (OCN), was constitutively detected in OCCM-30 cells. PGE(2) dose dependently stimulated ALP activity and BSP-mRNA expression in OCCM-30 cells at day 3. Transcripts for OPG and RANKL and the protein level of OPG in culture media were upregulated with PGE(2) stimulation. CONCLUSION: These results demonstrate that PGE(2) suppressed cementoblast proliferation but stimulated ALP activity and the BSP-mRNA level, suggesting a role of PGE(2) in controlling cementoblast differentiation, and further indicate that PGE(2) modulates RANKL and OPG expression in cementoblasts; the increase of OPG secreted from cementoblasts with PGE(2) stimulation may be essential to protect the root surface from resorption.