An overview of the medical-physics-related verification system for radiotherapy multicenter clinical trials by the Medical Physics Working Group in the Japan Clinical Oncology Group-Radiation Therapy Study Group

The Japan Clinical Oncology Group-Radiation Therapy Study Group (JCOG-RTSG) has initiated several multicenter clinical trials for high-precision radiotherapy, which are presently ongoing. When conducting multi-center clinical trials, a large difference in physical quantities, such as the absolute doses to the target and the organ at risk, as well as the irradiation localization accuracy, affects the treatment outcome. Therefore, the differences in the various physical quantities used in different institutions must be within an acceptable range for conducting multicenter clinical trials, and this must be verified with medical physics consideration. In 2011, Japan's first Medical Physics Working Group (MPWG) in the JCOG-RTSG was established to perform this medical-physics-related verification for multicenter clinical trials. We have developed an auditing method to verify the accuracy of the absolute dose and the irradiation localization. Subsequently, we credentialed the participating institutions in the JCOG multicenter clinical trials that were using stereotactic body radiotherapy (SBRT) for lungs, intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) for several disease sites, and proton beam therapy (PT) for the liver. From the verification results, accuracies of the absolute dose and the irradiation localization among the participating institutions of the multicenter clinical trial were assured, and the JCOG clinical trials could be initiated.

Hyperuricemia impaired nitric oxide bioavailablity and deteriorated pulmonary arterial hypertension via a uric acid transporter, URATv1 in xanthine oxidoreductase (XOR)-independent manner

Background

Hyperuricemia occurs in approximately 80% in patients with pulmonary arterial hypertension (PAH) and is positively correlated with pulmonary arterial pressure (PAP). It has been reported that uric acid (UA) reduced endothelium derived nitric oxide (NO) production in porcine pulmonary arterial endothelial cells (PAEC). However, the effects of UA and xanthine oxidoreductase (XOR), catalytic enzyme of UA, on the development of PAH have not been fully elucidated.

Purpose

We examined the followings; (1) the effects of hyperuricemia on the endothelial function and the development of PAH in rats (2) the therapeutic effects of UA transporter inhibitor on PAH in rats, and (3) the role of XOR in PAH in mice.

Methods

We used normal and 5-wk Sugen5416/Hypoxia/Normoxia-exposed (SU/Hx/Nx) rats. Gene expression levels of URATv1, a UA transporter, were measured by RT-PCR. We determined the isometric tension of PA rings isolated from normal rats. The study with the isolated perfused lung preparation was performed in SU/HX/Nx rats. To investigate the chronic effect of UA on the development of PAH, hyperuricemia was induced by the administration of 2% oxonic acid (OA) in diet for 6-wk. Benzbromarone (BBR, 10mg/kg/day, diet, from weeks 0 to 5), a URATv1 transporter inhibitor, was administered in the SU/Hx/Nx-rats with or without 2%OA. To examine the role of XOR in PAH, XOR+/− and wild type (WT) mice were exposed to 3-wk Nx or Hx (10% O2).

Results

The mRNA of URATv1 was detected in the normal lungs. Isometric tension study showed that UA (8 mg/dl) inhibited acetylcholine-induced vasorelaxation. In perfused lung preparations, UA acutely increased estimated PVR in a dose-dependent manner (1.6–16.0mg/dl) with reducing cGMP levels in the lungs. BBR significantly attenuated the pressor response to UA. UA levels in the plasma and the lung tissues were significantly elevated in SU/Hx/Nx-rats with 2%OA (normal vs. vehicle vs. 2%OA, plasma: 0.24±0.01 vs. 0.80±0.14 and 1.44±0.17 mg/dl; lung tissues: 68±3 vs. 142±3 and 377±46 pmol/g tissue). They exhibited further elevation of right ventricle systolic pressure (RVSP) (31±2 vs. 72±6 vs. 101±3 mmHg) and Ea (a marker of RV afterload) (0.24±0.04 vs. 0.97±0.15 vs. 2.36±0.49 mmHg/μL) with the exacerbation of occlusive lesions of PAs. BBR had no changes in the UA levels in the plasma (1.93±0.30 mg/dL), but significantly reduced the UA levels in the lung tissues (101±10 pmol/g tissue) and attenuated the increase in RVSP (53±8mmHg) and Ea (0.21±0.05 mmHg/mL) in the SU/Hx/Nx-rats with 2%OA. On the other hand, BBR had no effects on RVSP (76±7 mmHg) and Ea (0.91±0.15 mmHg/mL) in the SU/Hx/Nx-rats without 2%OA. There were no significant differences in RVSP between XOR+/− mice with Hx and WT with Hx (26±2 vs. 26±2 mmHg).

Conclusions

Hyperuricemia itself impairs endothelial function and deteriorates PAH via URATv1 in a XOR-independent manner. UA can be a novel therapeutic target for PAH.

Funding Acknowledgement

Type of funding source: None

Comparison between optical frequency domain imaging and intravascular ultrasound in PCI guidance for Biolimus A9 eluting stent implantation

Background

It has been reported that intravascular ultrasound (IVUS) guided PCI reduced a risk of major adverse cardiac event compared to conventional angiography guided PCI, while comparison between IVUS-guided and optical frequency domain imaging (OFDI)-guided PCI specifically in long-term clinical outcomes (>1 year) has been unexplored.

Purpose

We sought to compare imaging surrogates at 8 months and clinical outcomes beyond 1 year after drug-eluting stent implantation between IVUS and OFDI guidance.

Methods

The MISTIC-1 is a prospective, multi-centre, single-blinded, randomised-controlled, non-inferiority trial comparing OFDI-guided and IVUS-guided PCI using Biolimus A9 eluting Nobori stent. We enrolled patients with stable coronary artery disease who have symptoms or clinically relevant myocardial ischemia. Stent landing zones were selected in the most normal looking sites with largest lumen and without percentage plaque area >50% in IVUS group while without lipidic plaque of >2 quadrants or suggestive thin-cap fibroatheroma in OFDI group. Stent sizing was based on external elastic lamina (EEL) in IVUS group, while by taking 10% or 0.25mm larger than mean lumen diameter at reference sites in OFDI group. Stent optimisation with in-stent minimum lumen area ≥80% of the average lumen area at proximal and distal reference sites was encouraged in both groups. Primary efficacy endpoint is in-segment minimum lumen area (MLA) assessed by OFDI at 8 months. Secondary safety endpoint is a composite of cardiovascular death, target vessel myocardial infarction, or target lesion revascularisation. Based on the assumption that mean in-segment MLA at follow-up was 4.5mm2 with a standard deviation of 2.0mm2 in the control (IVUS) group and a non-inferiority limit of 1.2mm2 for OFDI group, sample size was estimated as 48 cases in each group with 5% type I error and 90% statistical power.

Results

Since June-2014 and August-2016, we prospectively enrolled 109 patients (mean age 70 years, male 78%) with 126 lesions. Baseline patient and lesion characteristics were well balanced and average nominal size and length of stent used did not differ between OFDI-guided and IVUS-guided PCI (3.0 and 19.1mm vs. 3.1 and 19.3mm, respectively). Post-procedural minimum stent area was 6.24mm2 in OFDI group and 6.72mm2 in IVUS group (p=0.20). At 8-month follow-up, in-segment MLA was 4.56mm2 in OFDI group and 4.13mm2 in IVUS group (P for non-inferiority <0.001). During the follow-up (median 4.5 years [1654 days]), incidence rates of major adverse cardiac event were comparable between the two groups (7.4% in OFDI group and 7.3% in IVUS group, hazard ratio 0.96, 95% CI 0.24–3.83, p=0.95). No definite or probable stent thrombosis were documented in both groups.

Conclusion

OFDI-guided PCI demonstrated comparable results in achieving satisfactory imaging surrogates as well as long-term clinical outcomes after newer generation DES implantation as compared to IVUS-guided PCI.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Suzuken Memorial Foundation

Conceptual design of a collimator for the neutron emission profile monitor in JT-60SA using Monte Carlo simulations

Materials and structures of a collimator for a new neutron emission profile monitor in JT-60SA are examined through Monte Carlo simulations using the Monte Carlo N-Particle transport code. First, the shielding properties of various material combinations are compared in order to determine a combination with high shielding performances against both neutrons and gamma-rays. It is found that a collimator consisting of borated polyethylene and lead has a high shielding performance against neutrons. Moreover, a high shielding performance against gamma-rays is obtained when a lead pipe with a radial thickness of 0.01 m is inserted into a collimation tube. Second, we demonstrate that it is possible to improve the spatial resolution to a desired level by installing a thin tubular extension structure that fits into the limited space available between the main collimator block and the tokamak device. Finally, the collimator structures that meet both the targeted spatial resolutions (<10% of the plasma minor radius) and the targeted counting rate (10⁵ cps order) are discussed.

Five-year major adverse cardiac and cerebrovascular events of patients with lipid core abutting lumen (LCAL) on integrated-backscatter intravascular ultrasound undergoing PCI with current DES

Background

Percutaneous Coronary Intervention (PCI) using the new generation drug-eluting stent (DES) has been extremely reduced target lesion revascularization (TLR) in recent years. However, a high incidence of non-target lesion-related cardiovascular events in patients undergoing PCI is an important problem to be solved. According to the previous findings, patients with vulnerable plaques particularly have a high recurrence of cardiovascular events. Little studies, however, has been done to examine the relationship between plaque characteristics on intravascular imaging in a target lesion and non-target lesion-related cardiovascular events.

Purpose

The main objective of this study is to investigate the five-year major adverse cardiac and cerebrovascular events (MACCE) of patients with lipid core abutting lumen (LCAL) on integrated backscatter intravascular ultrasound (IB-IVUS) in a target lesion undergoing PCI with current DES.

Methods and results

Between February 2010 and September 2013, in total 780 patients with ischemic heart disease undergoing PCI, 166 target lesions in 166 consecutive patients with non-ST segment elevation acute coronary syndrome (NSTE-ACS) and stable angina pectoris (SAP) undergoing IVUS-guided PCI were studied.

Plaque characteristics in all target lesions were analyzed by three-dimensional IB-IVUS system using the mechanical IVUS catheter. Our previous study has found that LCAL which is defined as a lipid pool directly in contact with the lumen visualizes the thin fibrous cap of less than 75μm on optical coherence tomography (OCT). On the basis of this data, LCAL at minimal lumen area (MLA) site was identified.

In total, 39 patients had lesions with LCAL at MLA site (LCAL(+)), and 127 patients had those without LCAL (LCAL(−)).

The primary endpoint was defined as MACCE, including cardiovascular death, non-fatal myocardial infarction, non-fatal stroke and non-TLR for the new lesion during a median follow up of five years. The MACCE occurred significantly higher in the LCAL(+) than in the LCAL(−) (38.5% vs. 17.3%; p&lt;0.005). And the Kaplan-Meier estimates have shown that the cumulative incidence of MACCE was significantly higher in the LCAL(+) than in the LCAL(−) (log rank test, p=0.041). Additionally, after adjustment for confounders, gender, prior PCI and LCAL was the independent predictors for the MACCE of patients undergoing PCI with current DES.

Furthermore, after adding LCAL to a baseline model with established factors consisting of age, gender, diabetes mellitus, prior PCI and percentage lipid volume on IB-IVUS, the net reclassification (p&lt;0.002) and integrated discrimination improvement (p&lt;0.004) significantly improved compared to baseline model alone.

Conclusions

In this study, it has become clear that LCAL on IB-IVUS is likely to be a surrogate marker of MACCE in patients undergoing PCI with current DES.

Funding Acknowledgement

Type of funding source: None

The understanding of congruent and incongruent referential gaze in 17-month-old infants: an eye-tracking study comparing human and robot

Several studies have shown that the human gaze, but not the robot gaze, has significant effects on infant social cognition and facilitate social engagement. The present study investigates early understanding of the referential nature of gaze by comparing-through the eye-tracking technique-infants' response to human and robot's gaze. Data were acquired on thirty-two 17-month-old infants, watching four video clips, where either a human or a humanoid robot performed an action on a target. The agent's gaze was either turned to the target (congruent) or opposite to it (incongruent). The results generally showed that, independent of the agent, the infants attended longer at the face area compared to the hand and target. Additionally, the effect of referential gaze on infants' attention to the target was greater when infants watched the human compared to the robot's action. These results suggest the presence, in infants, of two distinct levels of gaze-following mechanisms: one recognizing the other as a potential interactive partner, the second recognizing partner's agency. In this study, infants recognized the robot as a potential interactive partner, whereas ascribed agency more readily to the human, thus suggesting that the process of generalizability of gazing behaviour to non-humans is not immediate.

Feasibility study on a novel tiny dosimeter using a barium titanate capacitor

In our laboratory we have confirmed that the capacitance of barium titanate-based capacitors changes due to radiation. Since a commercially available capacitor is very small and inexpensive, it may be used as a multidimensional dose meter in which a large number of capacitor elements are arranged, or may be embedded in the body and used as an in-vivo dose meter. In this study we examined the usefulness of a dosimeter using the capacitance change of a barium titanate capacitor. As a basic property, it was confirmed that the dose linearity was good. With regard to dose rate characteristics and response to fractionated irradiation, capacitance change due to aging affects measurement accuracy, but online measurement of capacitance change immediately before irradiation can be performed to correct aging effects during irradiation. By doing this, we confirmed that the dose rate characteristics and the response to fractionated radiation are improved.

[Real-time Lens Exposure Dose Measurement Using a Scintillator with Optical Fiber Dosimeter during Cardiac Catheter Operation]

In recent years, the exposure dose of the operator's eye lens during interventional radiology operations has become a problem. We therefore evaluated the feasibility of real-time lens dose measurement using scintillator with optical fiber (SOF) dosimeter. Given that the SOF dosimeter is calibrated for direct X-rays, we performed a calibration for scattered X-rays to investigate energy dependence and the accuracy of lens dose measurements. The detection limit was calculated using the Kaiser method. The SOF dosimeter and the radiophotoluminescence glass (RPLG) dosimeter were attached to the protective glasses worn by the operator, and the lens exposure dose of the operator during cardiac catheterization was measured. In the phantom experiment, the SOF dosimeter had an error rate of 5.45% based on the measured value of the ionization chamber dosimeter. The sensitivity characteristics of the SOF dosimeter were slightly reduced on the higher side of the effective energy. The difference in sensitivity was related to variations in the additional filter and energy dependency. The sensitivity difference was 18.5% at maximum. Furthermore, when the additional dose was displayed, the influence of noise on long-term measurement was considerable. Using the Kaiser method to obtain the detection limit, the accuracy of the integrated dose had SOF dosimeter error rates of 4.3% to 15.5% with respect to the integrated value of the RPLG dosimeter when calibrated by the ionization chamber dosimeter. The use of the SOF dosimeter allowed for the real-time visualization of the exposure status of the eye lens and measurements with a relatively high accuracy.

A self-reported measurement scale on a potential component of competency in the healthcare staff engaged in the prevention and control of non-communicable disease in Fiji

Background

According to the World Health Organization, an estimated 80% or more deaths in Pacific island countries, including Fiji, were related to non-communicable diseases (NCDs). Although competency-based approaches have been effective for developing healthcare workers’ capabilities, there are only a few reports on competency scales of healthcare workers for NCD prevention. We aimed to develop a self-reported measurement scale on a potential component of competency in the healthcare staff engaged in the prevention and control of NCDs in Fiji.

Methods

There were 378 Ministry of Health and Medical Services staff members working on NCD prevention and control in Fiji included in this study, which was a cross-sectional survey of social factors, working situation factors, and competency. Exploratory factor analysis was conducted to assess potential competency components, whereas Cronbach’s α coefficient and analysis of variance were used to assess the validity and reliability of the scale items, respectively. Multivariate regression analyses were conducted to analyze the respondents’ factor scores relative to social status and work situations.

Results

The factor analysis revealed 16 items that identified competency in four work types: 1) work management, 2) monitoring and evaluation, 3) community partnership, and 4) community diagnosis. The monitoring and evaluation roles were related to ethnic background, community partnership was related to religion, and community diagnosis was related to academic qualifications.

Conclusions

Based on the results, we developed a competency scale for the four work types. This scale can help healthcare workers engage in better management of residents with NCDs in Fiji.

P3388Five year outcomes of patients with lipid rich plaque detected three-dimensional Integrated-Backscatter intravascular ultrasound (IB-IVUS) in target lesion after second generation DES implantation

Background

Elective percutaneous coronary intervention (PCI) using second generation drug-eluting stent (DES) has been dramatically reduced restenosis rate. Recently, it has been reported that plaque characterization in nontarget lesion is associated with cardio-vascular events in ischemic heart disease patients undergoing elective PCI. However, it is unclear whether plaque characterization in target lesion is predictor of MACEs (major adverse cardiac events) after elective PCI.

Purposes

The aim of this study is whether plaque characterization detected integrated-backscatter intravascular ultrasound (IB-IVUS) in the target lesion is associated with MACEs in patients with PCI after second generation DES implantation.

Methods and results

Of 700 patients with ischemic heart disease, 552 patients were excluded for chronic totally occlusion, severe calcification hindering precise intracoronary imaging, tortuous lesions, ostial or left main stem lesions and ST-elevated myocardial infarction patients. Finally, 148 consecutive patients who consented to repeated IB-IVUS prior to undergoing elective PCI were recruited in the study.Plaque characterization in target lesion was identified for three-dimensional IB-IVUS technology using the mechanical IVUS catheter (ViewIT, 40 MHz, 2.5 Fr; Terumo, Tokyo, Japan). The median of percentage lipid volume in all target lesions was 47.6%. Furthermore, lipid rich plaque (LRP) group was defined as the lesions consisting of percentage lipid volume greater than the median. And, non-lipid rich plaque (non-LRP) group was defined as the lesions consisting of percentage lipid volume less than the median. MACEs were defined as cardiovascular death, target vessel myocardial infarction, target lesion revascularization and stent thrombosis. The median of follow up period was 60 months. Of the 148 patients, 106 patients had stable angina pectoris. The remaining 42 patients are acute coronary syndrome (NSTE-ACS). 74 patients were classified LRP groups and 74 patients were non-LRP groups. No significant differences were observed between the two groups with respect to age, sex and coronary risk factors. While plaque and vessel volume were greater in the LRP group (216.9±116.3mm3, p<0.001) than non-LRP group (322.5±144.0mm3, p p<0.001). Remodeling index was greater in LRP group (1.02±0.18) than non-LRP group (0.93±0.18, p<0.003). Although MACEs were no significant differences between the two groups, the number of MACEs tend to be more in patients with LRP group (8.1±27.4%) than small lipid group (2.7±16.3, p<0.147). Especially, cardiac death tend to be more in LRP group (6.7±25.2% than non-LRP group (1.3±11.6, p<0.096).

Conclusions

In conclusion, lipid rich plaque detected by three dimensional IB-IVUS system in target lesion with patients undergoing elective PCI may be associated with clinical outcomes for five years after second generation DES implantation.

Acknowledgement/Funding

None

P4691Chronic blockade of toll-like receptor 9 ameliorated pulmonary arterial hypertension by reducing perivascular inflammation in rats

Background/Introduction

Perivascular inflammation plays an important role in the pathogenesis of pulmonary arterial hypertension (PAH). Recent studies have demonstrated that damaged mitochondrial DNA induces sterile inflammation by activating toll-like receptor (TLR)9 in spontaneous hypertensive rats. However, it remains unclear whether TLR9 is involved in perivascular inflammation and subsequent development of PAH.

Purpose

The purpose of the present study is to investigate whether chronic inhibition of TLR9 can ameliorate monocrotaline (MCT)-induced PAH in rats.

Methods

Male Sprague-Dawley rats were injected with MCT (60 mg/kg). First, we conducted immunohistochemistory to examine which cell types express TLR9 in lungs of normal rats and MCT-exposed rats. Second, we extracted cell-free DNA from plasma of rats and amplified genes of COX2 by real-time PCR to detect circulating cell-free mitochondrial DNA, a ligand of TLR9. Third, the administration of a selective TLR9 inhibitor (E6446, 10mg/kg/day, drinking water) or non-selective TLR9 inhibitor (chloroquine: 50mg/kg/day, ip) started three days before MCT injection and sacrificed on day 21. We assessed hemodynamic data and histopathological analysis (EVG stain for medial wall thickness (MWT) in pulmonary arteries (outer diameter: 50 ∼ 100 μm) and CD68 for macrophage accumulation around pulmonary arteries (outer diameter: <50 μm)), and measured the levels of interleukin-6 (IL-6) in lungs by real time PCR. Finally, we investigated survival rate in the reversal protocol, where we started the administration of E6446 on day 14.

Results

TLR9 was expressed dominantly in pulmonary endothelial cells and macrophages in the lungs of both normal rats and MCT-exposed rats. Compared with normal rats, MCT-exposed rats showed increased gene expression of COX2 (0.048±0.001 vs. 0.052±0.001 expressed by 1/Ct) in plasma on day 14. MCT-exposed rats also had increased right ventricular systolic pressure (RVSP: 21±1 vs. 60±2 mmHg), total pulmonary vascular resistance index (TPRI: 0.07±0.01 vs. 0.43±0.02 mmHg/min/mL/kg), MWT (0.07±0.01 vs. 0.26±0,02) and accumulation of macrophages (1.6±0.3 vs. 20.0±1.7 cells/HPF) on day 21. In the prevention protocol, either E6446 or chloroquine significantly prevented the elevations of RVSP (49±4 or 48±3 mmHg) and TPRI (0.29±0.04 or 0.27±0.03 mmHg/min/mL/kg) with reducing MWT (0.18±0.01 or 0.18±0.01) and macrophage accumulation (9.7±1.3 or 9.8±2.5 cell/HPF) on day 21. In addition, these drugs significantly reduced the levels of IL-6 mRNA compared with MCT group (4.4±1.0 or 4.8±1.4 vs. 11.9±1.0). In the reversal protocol, the treatment of E6446 had significantly increased the survival rate (50 vs. 10%).

Conclusions

TLR9 largely contributes to the development of PAH by reducing perivascular inflammation. Inhibition of TLR9 could be a novel therapeutic target for PAH.

Relationship Between Tube Voltage and Physical Image Quality of Pulmonary Nodules on Chest Radiographs Obtained Using the Bone-Suppression Technique

RATIONALE AND OBJECTIVES

Image quality of chest radiographs is affected by tube voltage. This study aimed to clarify the relationship between tube voltage and physical image quality of pulmonary nodules on bone-suppressed chest radiographs.

MATERIALS AND METHODS

An anthropomorphic chest phantom and a spherical simulated nodule, with a 12-mm diameter and approximately +100 Hounsfield units were used. The lung field of the phantom was divided into three areas, based on the overlap with the ribs in the chest radiograph. Ten positions of the simulated nodule were defined in each area. One hundred and twenty chest radiographs were acquired using four tube voltages (70 kVp, 90 kVp, 110 kVp, and 130 kVp) for a total of 30 nodule positions and were processed to create bone-suppressed images. Differences in contrast and contrast-to-noise ratio (CNR) were analyzed for all pairs of the four tube voltages using a two-sided Wilcoxon signed-rank test.

RESULTS

In the area not overlapping with ribs, a statistically significant difference was observed only in contrast between tube voltage of 70 kVp and 90 kVp (p = 0.01). In the area overlapping with one or two ribs, the contrast and CNR tended to be higher at a lower tube voltage. In particular, the p values between the contrast at 70 kVp and that at the other three tube voltage settings were less than 0.01.

CONCLUSION

For a relatively dense nodule, the contrast and CNR in the bone-suppressed chest radiograph were significantly improved with lower tube voltage in the lung field overlapping with the ribs.

Identification of the Novel Tooth-Specific Transcription Factor AmeloD

Basic-helix-loop-helix (bHLH) transcription factors play an important role in various organs' development; however, a tooth-specific bHLH factor has not been reported. In this study, we identified a novel tooth-specific bHLH transcription factor, which we named AmeloD, by screening a tooth germ complementary DNA (cDNA) library using a yeast 2-hybrid system. AmeloD was mapped onto the mouse chromosome 1q32. Phylogenetic analysis showed that AmeloD belongs to the achaete-scute complex-like ( ASCL) gene family and is a homologue of ASCL5. AmeloD was uniquely expressed in the inner enamel epithelium (IEE), but its expression was suppressed after IEE cell differentiation into ameloblasts. Furthermore, AmeloD expression showed an inverse expression pattern with the epithelial cell-specific cell-cell adhesion molecule E-cadherin in the dental epithelium. Overexpression of AmeloD in dental epithelial cell line CLDE cells resulted in E-cadherin suppression. We found that AmeloD bound to E-box cis-regulatory elements in the proximal promoter region of the E-cadherin gene. These results reveal that AmeloD functions as a suppressor of E-cadherin transcription in IEE cells. Our study demonstrated that AmeloD is a novel tooth-specific bHLH transcription factor that may regulate tooth development through the suppression of E-cadherin in IEE cells.