Risk factors for dental findings of the development of medication-related osteonecrosis of the jaw: Investigation of 3734 teeth in cancer patients receiving high dose antiresorptive agents.

Background/purpose: Local infection is a risk factor for medication-related osteonecrosis of the jaw (MRONJ), along with invasive dental treatment of the bone; the tooth that is the source of infection should be extracted prior to the administration of bone resorption inhibitors. However, which teeth should be extracted remains unclear. This study aimed to determine the relationship between dental findings prior to high-dose antiresorptive agent (ARA) administration and the subsequent development of MRONJ. Materials and methods: Patients with cancer who were scheduled to receive high-dose ARAs and referred to our hospital between 2011 and 2020 were included in this retrospective study. Apical lesions, enlargement of the periodontal space, thickening of the lamina dura, alveolar bone resorption of >1/3, periapical osteosclerosis, and local infection symptoms in each tooth were investigated using medical records and panoramic radiographs. Results: A total of 172 patients, 329 jaws, and 3734 teeth were registered. MRONJ developed in 68 teeth in 33 jaws of 32 patients. In tooth-by-tooth analysis, fewer teeth (P < 0.001), apical lesions (P < 0.001), periapical osteosclerosis (P < 0.001), local infection symptoms (P = 0.002), and one or more dental findings (P < 0.001) were significant factors for MRONJ development. In jaw-by-jaw analysis, old age, local infection symptoms, and number of radiographic abnormalities per tooth were significant. In patient-by-patient analysis, patients with diabetes and those with fewer teeth developed MRONJ. Conclusion: Patients with fewer teeth, apical lesions, periapical osteosclerosis, and local infection were more likely to develop MRONJ. Therefore, these teeth should be treated as much as possible before ARA administration.

Early-stage periodontal ligament compression predicts orthodontically induced root resorption in rats.

OBJECTIVES: To determine the effect of orthodontic pressure on periodontal ligament (PDL) compression in rats and assess correlation between PDL compression and orthodontically induced root resorption (OIRR). MATERIALS AND METHODS: Eight female Wistar rats aged 10 weeks underwent surgery to place 2 mini-screws at the center of the palatal plate. 25 cN coil springs connecting the maxillary first molars and mini-screws were applied bilaterally to generate mesial force. Maxillary first molars were assigned to undergo either bodily or tipping movements. Micro-computed tomography (µCT) scans were taken on days 0, 3, 7, and 14, and histological sections were taken on day 14. OIRR was measured from histological sections, and the corresponding PDL compression ratio was quantified using µCT images. RESULTS: The PDL was compressed by approximately 76% in tipping movement and 55% in bodily movement after 3 days, and by approximately 47% in bodily and tipping movements after 7 days of orthodontic force application. The extent of OIRR in tipping movement was significantly greater than that in bodily movement. A strong positive correlation between OIRR and PDL compression ratio was observed on day 3; however, no correlation was observed on day 7. CONCLUSIONS: A strong correlation between PDL compression ratio and OIRR was observed at an early stage after the application of orthodontic force regardless of the tooth movement type (bodily or tipping), implying the importance of early stage PDL compression in the induction of OIRR.

Fixation of an orthodontic anchor screw using beta-tricalcium phosphate in a screw-loosening model in rats.

OBJECTIVES: To create an orthodontic anchor screw (OAS)-loosening model and to investigate whether filling the bone hole with beta-tricalcium phosphate (ß-TCP) can fix the OAS against orthodontic force. MATERIALS AND METHODS: Bone holes with different diameters (1.6, 2.1, or 2.5 mm) were drilled in the tibias of 11-week-old male Wistar rats, and an OAS (3.0 mm in length and 1.2 mm in diameter) was inserted. After a healing period of 2 or 4 weeks, orthodontic force was applied, and the diameter of the bone hole appropriate for the loosening model was determined. Subsequently, under the loosening model, the bone hole was filled with ß-TCP, orthodontic force was applied, and movement of the OAS and surrounding tissue changes were evaluated by micro-computed tomography images and histological specimen analysis. RESULTS: The bone hole of 1.6 mm in diameter was employed as the OAS-loosening model. When ß-TCP was inserted into the bone hole, the linear distance and mesial tipping angle of the OAS movement decreased markedly. Furthermore, the values of bone morphometry significantly increased with ß-TCP filling. CONCLUSIONS: An OAS-loosening model was established in rats and demonstrated that the loosening OAS was stabilized by ß-TCP filling through bone formation. ß-TCP may be useful for fixation of a loosening OAS.

Effect of masseter muscle mass on the rate of experimental tooth movement in rats.

BACKGROUND: Previous clinical observational studies have suggested that orthodontic tooth movement (OTM) is related, at least partly, to the mass and/or capabilities of the masticatory muscles. OBJECTIVES: Our study aimed to examine the influence of masticatory muscle mass on the OTM in an animal experimental model in which the masseter muscle was modulated by botulinum neurotoxin type A (BTX) injection. METHODS: Eighteen Wistar rats were equally divided into two groups: BTX injection and control. BTX was injected bilaterally into the masseter muscles. Three days after the injection, the maxillary left first molars were orthodontically moved for 14 days. At the end of the experiment, micro-computed tomography was performed to evaluate the rate of OTM and bone morphometry. The masseter muscles were weighed and prepared for histological analyses. RESULTS: The masseter muscle mass in the BTX group was less than that in the control group, and histological findings showed atrophy of muscle fibres. The rate of OTM was significantly higher in the BTX group than in the control group. Furthermore, a negative correlation was detected between masseter muscle mass and OTM in the BTX group. Bone morphometry showed no difference between the control and BTX groups. CONCLUSION: Decreased masseter muscle mass was found to be closely related to an increase in the rate of OTM in rats using BTX injection to modify the masseter muscle mass. Masseter muscle mass could be a predictive factor for OTM in rats injected with BTX.

Lithium reduces orthodontically induced root resorption by suppressing cell death, hyalinization, and odontoclast formation in rats.

OBJECTIVES: To examine whether lithium suppresses orthodontically induced root resorption (OIRR) via two mechanisms (prevention of hyalinization in periodontal tissue and suppression of odontoclasts) and to investigate the changes in the periodontal tissue and alveolar bone, focusing on the appearance of cell death, hyalinization, and odontoclasts. MATERIALS AND METHODS: The maxillary first molars of 10-week-old male Wistar rats were moved mesially by a closed-coil spring for 14 days. Lithium chloride (LiCl; 0.64 mM/kg) or saline (control) was administered intraperitoneally daily. Tooth movements were measured using micro-computed tomography. Appearances of cell death, hyalinization, and odontoclasts were evaluated by histological analysis. RESULTS: OIRR observed on day 14 in the control group was suppressed strongly by LiCl administration. Apoptotic cells observed on day 1 in the compression area were gradually diminished on days 2 and 3 and transformed to hyalinization tissue in the control group. LiCl administration remarkably suppressed this cell death and subsequent hyalinization. Also, the appearance of odontoclasts in the compression area observed on day 7 was significantly suppressed by LiCl administration. Accordingly, these degenerative processes to OIRR were suppressed substantially by LiCl treatment. CONCLUSIONS: Lithium reduces OIRR through the suppression of periodontal ligament cell death, hyalinization, and odontoclast formation.

A case of periosteal fasciitis located in the mandible in a child.

Periosteal fasciitis (PF), a subtype of nodular fasciitis, is an uncommon benign soft-tissue mass that originates from the periosteum or tissues adjacent to bones. PF has rarely seen in children, especially involving in the mandible. This case report presents a rare case of PF originating from the periosteum of the mandible in an 11-year-old girl. She was referred to our hospital with fast-growing painless swelling in her left mandible. Computed tomography revealed an exophytic juxtacortical mass eroding the lower part of the left mandible and lower mandibular cortex with a periosteal reaction. The mass showed low signal intensity on T1-weighted magnetic resonance imaging (MRI) and high signal intensity on T2-weighted MRI. The apparent diffusion coefficient (ADC) of the lesion found to be moderate. Dynamic contrast-enhanced MRI revealed a gradual increment pattern in the central region of the mass. On 18F-fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT), relatively high 18F-FDG uptake was observed on the early scan and the 18F-FDG uptake was declined on the delayed scan. The clinical and conventional radiological findings of the mass were suggestive of malignancy. However, the findings of ADC and dynamic MRI and dual-time-point FDG-PET/CT favored benign etiology over malignant etiology. Histological and immunohistochemical findings along with reactive ossification of the periosteum confirmed the diagnosis of PF. Currently, comprehensive examinations, such as clinical, imaging, and histopathological examinations, are recommended for the definitive diagnosis of PF, while MRI and dual-time-point FDG-PET/CT could have a potential usefulness to differentiate from malignancy.

Traumatic myositis ossificans: multifocal lesions suggesting malignancy on FDG-PET/CT-a case report.

Myositis ossificans (MO) is a benign soft-tissue lesion characterized by the heterotopic formation of the bone in skeletal muscles, usually due to trauma. MO is occasionally difficult to diagnose because of its clinical and radiological similarities with malignancy. We report a case of traumatic MO (TMO) in the masseter and brachial muscles of a 37-year-old man who presented with painless swelling in the left cheek and severe trismus. Due to the absence of a traumatic history at the first consultation and identification of a tumorous lesion in the left masseter muscle by magnetic resonance imaging (MRI), the lesion was suspected to be a malignant tumor. Subsequently, 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (FDG-PET/CT) showed multiple regions of high FDG uptake across the whole body, suggestive of multiple metastases or other systemic diseases. However, intramuscular calcifications were also observed in the left masseter and brachial muscles, overlapping the areas with high FDG uptake. Moreover, multiple fractures were seen in the rib and lumbar spine, also overlapping the areas with high FDG uptake. Based on these imaging findings, along with a history of jet-ski trauma, TMO was suspected. The left cheek mass was surgically excised and histologically diagnosed as TMO. In this case report, FDG-PET/CT could detect multiple TMOs across the whole body. To the best of our knowledge, cases of multiple TMOs located far apart in different muscles are rare, and this may be the first report.

ATM-associated signalling triggers the unfolded protein response and cell death in response to stress.

Endoplasmic reticulum (ER) stress can be caused by perturbations in ER function resulting from the accumulation of unfolded/misfolded proteins in the ER lumen. Accumulating unfolded proteins trigger unfolded protein responses (UPRs) through activating three transmembrane sensors on the ER: IRE1α, PERK, and ATF6. The orchestrated action of these molecules upregulates genes encoding proteins involved in the downregulation of protein synthesis and acceleration of protein secretion. Ineffectiveness of these fail-safe mechanisms may lead to apoptosis. However, the molecular mechanisms upstream of the UPR are not fully understood. Here we show participation of ataxia telangiectasia mutated (ATM) in stress-induced apoptosis. Cytoplasmic ATM serves as a platform on which protein phosphatase 2A-dependent dephosphorylation of AKT activates glycogen synthase kinase 3ß, thereby downregulating nascent polypeptide-associated complex α subunit and γ-taxilin, triggering UPRs and leading to mitochondria-dependent apoptosis. These results suggest an ATM/AKT-dependent cell death pathway triggered by various forms of stress.

Phase 1 clinical study of cell therapy with effective-mononuclear cells (E-MNC) for radiogenic xerostomia (first-in-human study) (FIH study on E-MNC therapy for radiogenic xerostomia).

BACKGROUND: Treatment for most patients with head and neck cancers includes ionizing radiation with or without chemotherapy. This treatment causes irreversible damage to salivary glands in the irradiation field accompanied by a loss of fluid-secreting acinar cells and a considerable decrease of saliva secretion. There is currently no adequate conventional treatment for this condition. In recent years, we developed an effective culture method to enhance the anti-inflammatory and vasculogenic phenotypes of peripheral blood mononuclear cells (PBMNCs), and such effectively conditioned PBMNC (E-MNC) therapy has shown promising improvements to the function of radiation-injured salivary glands in preclinical studies. However, the safety and effect of E-NMC therapy have yet assessed in human. The objective of this ongoing first-in-man study is to assess the safety, tolerability, and in part the efficacy of E-MNC therapy for treating radiation-induced xerostomia. METHODS/DESIGN: This phase 1 first-in-man study is an open-label, single-center, two-step dose escalation study. A total of 6 patients, who had no recurrence of head and neck cancer over 5 years following radiation therapy and suffered from radiation-induced xerostomia, will receive a transplantation of E-NMCs derived from autologous PBMNCs to a submandibular gland. The duration of the intervention will be 1 year. To analyze the recovery of salivary secretion, a gum test will be performed. To analyze the recovery of atrophic salivary glands, computed tomography (CT), and magnetic resonance imaging (MRI) of salivary glands will be conducted. The primary endpoint is the safety of the protocol. The secondary endpoints are the changes from baseline in whole saliva secretion and salivary gland atrophy. DISCUSSION: This will be the first clinical study of regenerative therapy using E-MNCs for patients with severe radiation-induced xerostomia. The results of this study are expected to contribute to developing the low-invasive cell-based therapy for radiation-induced xerostomia. TRIAL REGISTRATION: This study was registered with the Japan Registry of Clinical Trials (http://jrct.niph.go.jp) as jRCTb070190057.

A case of tophaceous pseudogout of the temporomandibular joint extending into the cranium.

A case of tophaceous pseudogout (i.e., calcium pyrophosphate dihydrate crystal deposition disease) in the temporomandibular joint (TMJ) extending into the cranium is reported. A 59-year-old woman was referred to hospital with swelling and pain in the left cheek, and with trismus. Computed tomography imaging revealed a large, granular, calcified mass surrounding the left condylar head, partly destroying the cortex of the condylar head, and extending into the cranium by destroying the glenoid fossa. Magnetic resonance imaging revealed that the soft-tissue mass was of low-signal intensity on T1- and T2-weighted images, and was enhanced after intravenous injection of gadolinium. The mass was clinically and radiographically suspected to be a neoplastic lesion or a synovial osteochodromatosis. However, histological analysis demonstrated that the mass contained granulomatous lesion due to multiple nodular deposits of numerous rod-shaped and rhomboid crystals, which verified the diagnosis of tophaceous pseudogout. The lesion was excised surgically using a preauricular approach. Neither radiographic nor clinical examination demonstrated any signs of mass recurrence in the long-term 8- and 14-year postoperative recall examinations. Tophaceous pseudogout is a rare benign arthropathy that presents with clinical and radiographic features mimicking neoplastic conditions of the TMJ. Therefore, it is recommended that tophaceous pseudogout is considered in the differential diagnosis when a calcified mass lesion of the TMJ is encountered.

Magnetic resonance perfusion and diffusion characteristics of granulomatous diseases mimic those of malignant lesions: six case reports.

The perfusion and diffusion properties of a tumor are important clues in evaluating its growth potential and predicting its histological type, such as benign or malignant. Tumor perfusion can be estimated by assessing time-dependent changes in the intratumoral levels of the contrast agent during dynamic contrast-enhanced magnetic resonance (MR) imaging, whereas tumor diffusion can be estimated by assessing intratumoral water diffusivity on diffusion-weighted MR imaging. Granulomatous diseases with different etiologies occur in various head and neck regions, including the mandible, maxillary sinus, salivary glands, and lymph nodes. However, the perfusion and diffusion properties of granulomatous diseases in the head and neck regions are not well documented. In this study, we assessed the time-signal intensity curves and apparent diffusion coefficients of six granulomatous diseases of various histological types that appeared in the soft tissues of the head and neck. Our data show that the perfusion and diffusion characteristics of granulomatous diseases mimic those of malignant diseases, highlighting the need for careful interpretation of MR perfusion and diffusion findings to distinguish between granulomatous diseases and cancers of the head and neck region. Clinicians should pay particular attention to blood examination and biopsy results when interpreting imaging findings.

Lithium chloride reduces orthodontically induced root resorption and affects tooth root movement in rats.

OBJECTIVE: To investigate the influence of lithium chloride (LiCl) on orthodontic tooth movement (OTM), orthodontically induced root resorption (OIRR), and bone morphometry. MATERIALS AND METHODS: Ten-week-old female Sprague Dawley rats (n = 32) were divided into four groups based on the concentration of LiCl administered daily per kilogram body weight: 0 (control group), 0.32, 0.64, and 1.28 mM/kg body weight. The maxillary left first molars were moved mesially by a 10 cN coil spring for 14 days. Micro-computed tomography, scanning electron microscope, and scanning laser microscope images were taken to measure the amount of OTM, the volume of OIRR, and bone morphometry. RESULTS: OIRR clearly decreased depending on the amount of LiCl administered, although OTM moderately decreased. The tooth inclined mesially and the root apex moved distally in the control and 0.32 mM groups. On the other hand, the tooth inclination angle became smaller and the root apex moved mesially in the 0.64 and 1.28 mM groups. In bone morphometry, the cortical bone mineral content and bone volume increased because of LiCl administration, and the trabecular bone measurements decreased. OIRR negatively correlated to the cortical bone measurements, and the amount of OTM significantly correlated to the cortical bone morphometry. CONCLUSIONS: In rats, LiCl reduced OIRR, which induced mesial movement of the tooth root apex. OIRR positively correlated to cortical bone morphometry.

Perfusion MR imaging detection of carcinoma arising from preexisting salivary gland pleomorphic adenoma by computer-assisted analysis of time-signal intensity maps.

Tumor perfusion can be evaluated by analyzing the time-signal intensity curve (TIC) after dynamic contrast-enhanced (DCE) MR imaging. Accordingly, TIC profiles are characteristic of some benign and malignant salivary gland tumors. A carcinoma ex pleomorphic adenoma (CXPA) arises from a long-standing pleomorphic adenoma (PA) and has a distinctive prognostic risk depending on the tumor growth potential such as invasion beyond the preexisting capsule. Differentiating CXPA from PA can be very challenging. In this study, we have attempted to discriminate CXPA from PA based on a two-dimensional TIC mapping algorithm. TIC mapping analysis was performed on 8 patients with CXPA and 20 patients with PA after dynamic contrast-enhanced (DCE) MR imaging using a 1.5-T MR system. The TIC profiles obtained were automatically categorized into 5 types based on the enhancement ratio, maximum time, and washout ratio (Type 1 TIC with flat profile, Type 2 TIC with slow uptake, Type 3 TIC with rapid uptake and a low washout ratio, Type 4 TIC with rapid uptake and a high washout ratio, and Type 5 TIC not otherwise specific). The percentage tumor areas with each of the 5 TIC types were compared between CXPAs and PAs. Stepwise differentiation and cluster analysis using multiple TIC cut-off thresholds distinguished CXPAs from PAs with 75% sensitivity, 95% specificity, 86% accuracy, and 86% positive and 90% negative predictive values, when tumors with ≤1.1% Type 1 and ≥15% Type 4, or those with ≤1.1% Type 1, ≥78.1% Type 2, ≥16.1% Type 3, and <15% Type 4, or those with >1.1% Type 1, ≥78.1% Type 2, and ≥16.1% Type 3 areas were diagnosed as CXPAs. The overall TIC profiles predicted some aggressive CXPA growth patterns. These results suggest that stepwise differentiation based on TIC mapping is helpful in differentiating CXPAs from PAs.

Length of intact plasma membrane determines the diffusion properties of cellular water.

Molecular diffusion in a boundary-free medium depends only on the molecular size, the temperature, and medium viscosity. However, the critical determinant of the molecular diffusion property in inhomogeneous biological tissues has not been identified. Here, using an in vitro system and a high-resolution MR imaging technique, we show that the length of the intact plasma membrane is a major determinant of water diffusion in a controlled cellular environment and that the cell perimeter length (CPL) is sufficient to estimate the apparent diffusion coefficient (ADC) of water in any cellular environment in our experimental system (ADC = -0.21 × CPL + 1.10). We used this finding to further explain the different diffusion kinetics of cells that are dying via apoptotic or non-apoptotic cell death pathways exhibiting characteristic changes in size, nuclear and cytoplasmic architectures, and membrane integrity. These results suggest that the ADC value can be used as a potential biomarker for cell death.

Simple and reliable determination of intravoxel incoherent motion parameters for the differential diagnosis of head and neck tumors.

Intravoxel incoherent motion (IVIM) imaging can characterize diffusion and perfusion of normal and diseased tissues, and IVIM parameters are authentically determined by using cumbersome least-squares method. We evaluated a simple technique for the determination of IVIM parameters using geometric analysis of the multiexponential signal decay curve as an alternative to the least-squares method for the diagnosis of head and neck tumors. Pure diffusion coefficients (D), microvascular volume fraction (f), perfusion-related incoherent microcirculation (D*), and perfusion parameter that is heavily weighted towards extravascular space (P) were determined geometrically (Geo D, Geo f, and Geo P) or by least-squares method (Fit D, Fit f, and Fit D*) in normal structures and 105 head and neck tumors. The IVIM parameters were compared for their levels and diagnostic abilities between the 2 techniques. The IVIM parameters were not able to determine in 14 tumors with the least-squares method alone and in 4 tumors with the geometric and least-squares methods. The geometric IVIM values were significantly different (p<0.001) from Fit values (+2 ± 4% and -7 ± 24% for D and f values, respectively). Geo D and Fit D differentiated between lymphomas and SCCs with similar efficacy (78% and 80% accuracy, respectively). Stepwise approaches using combinations of Geo D and Geo P, Geo D and Geo f, or Fit D and Fit D* differentiated between pleomorphic adenomas, Warthin tumors, and malignant salivary gland tumors with the same efficacy (91% accuracy = 21/23). However, a stepwise differentiation using Fit D and Fit f was less effective (83% accuracy = 19/23). Considering cumbersome procedures with the least squares method compared with the geometric method, we concluded that the geometric determination of IVIM parameters can be an alternative to least-squares method in the diagnosis of head and neck tumors.

Comparison between ultrasonography and MR imaging for discriminating squamous cell carcinoma nodes with extranodal spread in the neck.

OBJECTIVE: To compare the diagnostic ability of ultrasonography (US) and MR imaging for discriminating squamous cell carcinoma (SCC) nodes with extranodal spread (ENS) in the neck. METHODS: US and MR imaging was retrospectively evaluated for differentiating ENS-positive (n=28) from ENS-negative (n=26) SCC nodes (>10mm short-axis diameter) in 50 patients with head and neck SCCs. We assessed nodal size on US and MR images; irregular nodal margin on US; and vanishing nodal border, flare, and shaggy nodal margin signs on T1-, fat-suppressed T2-, and contrast-enhanced T1-weighted MR images, respectively. US and MR images were analyzed by 3 radiologists in consensus and the results were compared between ENS-positive and ENS-negative SCC nodes. RESULTS: The nodal sizes of ENS-positive nodes (21±9 mm) were significantly larger than those of ENS-negative SCC nodes (14±4 mm) (p<0.001). Irregular nodal margins were more frequently observed in ENS-positive SCC nodes (75%) than in ENS-negative SCC nodes (12%). The vanishing nodal margin, flare, and shaggy nodal margin signs were more frequently observed in ENS-positive SCC nodes (93%, 89%, and 82%, respectively) than in ENS-negative nodes (46%, 19%, and 19%, respectively). A combination of size (≥22 mm) and imaging criteria (irregular margin or flare sign) best discriminated ENS-positive SCC nodes with 82% sensitivity, 89% specificity, and 85% accuracy for US and 89% sensitivity, 81% specificity, and 85% accuracy for MR imaging. CONCLUSION: US discriminated ENS-positive from ENS-negative SCC nodes with comparable accuracy and higher specificity than MR imaging.

An in vivo 3D micro-CT evaluation of tooth movement after the application of different force magnitudes in rat molar.

OBJECTIVE: To investigate the precise longitudinal change in the periodontal ligament (PDL) space width and three-dimensional tooth movement with continuous-force magnitudes in living rats. MATERIALS AND METHODS: Using nickel-titanium closed-coil springs for 28 days, 10-, 25-, 50-, and 100-g mesial force was applied to the maxillary left first molars. Micro-CT was taken in the same rat at 0, 1, 2, 3, 10, 14, and 28 days. The width of the PDL was measured in the pressure and tension sides from 0 to 3 days. Angular and linear measurements were used to evaluate molar position at day 0, 10, 14, and 28. The finite element model (FEM) was constructed to evaluate the initial stress distribution, molar displacement, and center of rotation of the molar. RESULTS: The initial evaluation of PDL width showed no statistical differences among different force magnitudes. Tooth movement was registered 1 hour after force application and gradually increased with time. From day 10, greater tooth movement was observed when 10 g of force was applied. The FEM showed that the center of rotation in the molar is located in the center of five roots at the apical third of the molar roots. CONCLUSION: The rat's molar movement mainly consists of mesial tipping, extrusion of distal roots, intrusion of mesial root, palatal inclination, and mesial rotation. Although the initial tooth movement after the application of different force magnitudes until day 3 was not remarkably different, 10 g of force produced more tooth movement compared with heavier forces at day 28.

Ionizing radiation induces macrophage foam cell formation and aggregation through JNK-dependent activation of CD36 scavenger receptors.

PURPOSE: Irradiated arteries of cancer patients can be associated with atherosclerosis-like lesions containing cholesterol-laden macrophages (foam cells). Endothelial cell damage by irradiation does not completely explain the foam cell formation. We investigated the possible underlying mechanisms for ionizing radiation (IR)-induced foam cell formation. METHODS AND MATERIALS: Human peripheral blood monocytes were activated by macrophage colony-stimulating factor and then treated with varying doses of IR in vitro in the absence of endothelial cells. Scavenger receptor expression and foam cell formation of IR-treated macrophages were investigated in the presence or absence of oxidized low-density lipoprotein. We also assessed the importance of mitogen-activated protein kinase activity in the macrophage colony-stimulating factor-activated human monocytes (macrophages) for the foam cell formation. RESULTS: We found that IR treatment of macrophage colony-stimulating factor-activated human peripheral blood monocytes resulted in the enhanced expression of CD36 scavenger receptors and that cholesterol accumulated in the irradiated macrophages with resultant foam cell formation in the presence of oxidized low-density lipoprotein. Furthermore, when cultured on collagen gels, human macrophages formed large foam cell aggregates in response to IR. Antibodies against CD36 inhibited the IR-induced foam cell formation and aggregation, indicating that the IR-induced foam cell formation and the subsequent aggregation are dependent on functional CD36. In addition, we found that IR of human macrophages resulted in c-Jun N-terminal kinase activation and that c-Jun N-terminal kinase inhibition suppressed IR-induced CD36 expression and the subsequent foam cell formation and aggregation. CONCLUSION: Taken together, these results suggest that IR-induced foam cell formation is mediated by c-Jun N-terminal kinase-dependent CD36 activation.

Molecular analysis of RANKL-independent cell fusion of osteoclast-like cells induced by TNF-alpha, lipopolysaccharide, or peptidoglycan.

Focusing on the final step of osteoclastogenesis, we studied cell fusion from tartrate-resistant acid phosphatase (TRAP)-positive mononuclear cells into multinuclear cells. TRAP-positive mononuclear cells before generation of multinuclear cells by cell fusion were differentiated from RAW264.7 cells by treatment with receptor activator of nuclear factor kappa B ligand (RANKL), and then the cells were treated with lipopolysaccharide (LPS), followed by culturing for further 12 h. LPS-induced cell fusion even in the absence of RANKL. Similarly, tumor necrosis factor (TNF)-alpha and peptidoglycan (PGN) induced cell fusion, but M-CSF did not. The cell fusion induced by RANKL, TNF-alpha, and LPS was specifically blocked by osteoprotegerin (OPG), anti-TNF-alpha antibody, and polymyxin B, respectively. LPS- and PGN-induced cell fusion was partly inhibited by anti-TNF-alpha antibody but not by OPG. When TRAP-positive mononuclear cells fused to yield multinuclear cells, phosphorylation of Akt, Src, extracellular signal-regulated kinase (ERK), p38MAPK (p38), and c-Jun NH2-terminal kinase (JNK) was observed. The specific chemical inhibitors LY294002 (PI3K), PP2 (Src), U0126 (MAPK-ERK kinase (MEK)/ERK), and SP600125 (JNK) effectively suppressed cell fusion, although SB203580 (p38) did not. mRNA of nuclear factor of activated T-cells c1 (NFATc1) and dendritic cell-specific transmembrane protein (DC-STAMP) during the cell fusion was quantified, however, there was no obvious difference among the TRAP-positive mononuclear cells treated with or without M-CSF, RANKL, TNF-alpha, LPS, or PGN. Collectively, RANKL, TNF-alpha, LPS, and PGN induced cell fusion of osteoclasts through their own receptors. Subsequent activation of signaling pathways involving PI3K, Src, ERK, and JNK molecules was required for the cell fusion. Although DC-STAMP is considered to be a requisite for cell fusion of osteoclasts, cell fusion-inducing factors other than DC-STAMP might be necessary for the cell fusion.