Conductive single-phase SrMoO3 epitaxial films synthesized in pure Ar ambience via plasma-assisted radio frequency sputtering.

The cubic perovskite SrMoO3 with a paramagnetic ground state and remarkably low room-temperature resistivity has been considered as a suitable candidate for the new-era oxide-based technology. However, the difficulty of preparing single-phase SrMoO3 thin films by hydrogen-free sputtering has hindered their practical use, especially due to the formation of thermodynamically favorable SrMoO4 impurity. In this work, we developed a radio frequency sputtering technology enabling the reduction reaction and achieved conductive epitaxial SrMoO3 films with pure phase from a SrMoO4 target in a hydrogen-free, pure argon environment. We demonstrated the significance of controlling the target-to-substrate distance (TSD) on the synthesis of SrMoO3; the film resistivity drastically changes from 1.46 × 105 µΩ·cm to 250 µΩ·cm by adjusting the TSD. Cross-sectional microstructural analyses demonstrated that films with the lowest resistivity, deposited for TSD = 2.5 cm, possess a single-phase SrMoO3 with an epitaxial perovskite structure. The formation mechanism of the conductive single-phase SrMoO3 films can be attributed to the plasma-assisted growth process by tuning the TSD. Temperature-dependent resistivity and Hall effect studies revealed metal-like conducting properties for low-resistive SrMoO3 films, while the high-resistive ones displayed semiconductor-like behavior. Our approach makes hydrogen-free, reliable and cost-efficient scalable deposition of SrMoO3 films possible, which may open up promising prospects for a wide range of future applications of oxide materials.

For the first time, we developed a plasma-assisted RF sputtering technology enabling the reduction reaction for the synthesis of single-phase conductive SrMoO₃ epitaxial films from insulating SrMoO₄ in pure-argon atmosphere.

Dialkyl Carbonate Synthesis Using Atmospheric Pressure of CO2.

Dialkyl carbonates (DRCs) are valuable compounds widely used in the industry. The synthesis of DRC from CO2 has attracted interest as an alternative to the current method, which uses phosgene. However, the reported approaches for DRC synthesis from CO2 requires high-pressure and high-concentration CO2, resulting in elevated costs associated with CO2 purification and manufacturing facilities. In this report, we present an environmentally friendly method for producing DRC from low-concentration and low-pressure CO2 via a dehydration condensation approach without the use of halogenated alkylating agents. This method involves the formation of monoalkyl carbonate [BASE-H][ROC(O)O] using a strong organic base and alcohols, tetraalkyl orthosilicates as dehydrating agents, and CeO2 as the catalyst. Using the method, 39 and 30% of diethyl carbonate yields were accomplished with only 100 and 15 vol % CO2 (CO2/N2 = 15:85) gas bubbling at atmospheric pressure, even under reaction conditions with no large excess of either CO2, alcohol, or dehydration agent.

Quadrupole anomalous Hall effect in magnetically induced electron nematic state.

Berry phases in both momentum and real space cause transverse motion in itinerant electrons, manifesting various off-diagonal transport effect such anomalous and topological Hall effects. Although these Hall effects are isotropic within the plane perpendicular to the fictitious magnetic field, here, we report the manifestation of the anisotropic linear anomalous Hall effect (AHE) in the spinel oxide NiCo2O4 epitaxial film. The unconventional Hall effect indicates a quadrupole dependence on the in-plane current direction being added to the uniform AHE. Moreover, its sign can be manipulated just by magnetic-field cooling. The anisotropic effect is attributed to an electron nematic state originating from a deformed electronic state owing to an extended magnetic toroidal quadrupole and ferrimagnetic order.

Direct Conversion of Low-Concentration CO2 into N-Aryl and N-Alkyl Carbamic Acid Esters Using Tetramethyl Orthosilicate with Amidines as a CO2 Capture Agent and a Catalyst.

Herein, we report the direct conversion of low-concentration CO2 (15 vol %), equivalent to the CO2 concentration in the exhaust gas from a thermal power station, into carbamic acid esters (CAEs), which are precursors for pharmaceuticals, agrochemicals, and isocyanates. The reaction was performed using Si(OMe)4 as a nonmetallic regenerable reagent and 1,8-diazabicyclo[5.4.0]undec-7-ene as a CO2 capture agent and catalyst. This reaction system does not require the addition of metal complex catalysts or metal salt additives and is therefore simpler than our previously reported reaction system involving Ti(OR)4 and a Zn(II) catalyst. A variety of N-aryl, N-alkyl, and bis CAEs (precursors of polyurethane raw materials) were obtained in moderate to high yields (45-77% for 6 examples, 84-89% for 7 examples). In addition, bis CAEs were successfully synthesized from simulated exhaust gas containing impurities such as SO2, NO2, and CO or on a gram scale. We believe that this method can eliminate the use of toxic phosgene as the raw material for isocyanate production and mitigate CO2 emissions.

N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO2.

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc)2 /phen-catalyzed synthesis of organic carbamates from CO2 , amines, and the reusable reactant Si(OMe)4 . Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure.

One-pot catalytic synthesis of urea derivatives from alkyl ammonium carbamates using low concentrations of CO2.

To reduce anthropogenic carbon dioxide (CO2) emissions, it is desirable to develop reactions that can efficiently convert low concentrations of CO2, present in exhaust gases and ambient air, into industrially important chemicals, without involving any expensive separation, concentration, compression, and purification processes. Here, we present an efficient method for synthesizing urea derivatives from alkyl ammonium carbamates. The carbamates can be easily obtained from low concentrations of CO2 as present in ambient air or simulated exhaust gas. Reaction of alkyl ammonium carbamates with 1,3-dimethyl-2-imidazolidinone solvent in the presence of a titanium complex catalyst inside a sealed vessel produces urea derivatives in high yields. This reaction is suitable for synthesizing ethylene urea, an industrially important chemical, as well as various cyclic and acyclic urea derivatives. Using this methodology, we also show the synthesis of urea derivatives directly from low concentration of CO2 sources in a one-pot manner.

CO2 capture by Mn(i) and Re(i) complexes with a deprotonated triethanolamine ligand.

CO2 capture at low concentration by catalysts is potentially useful for developing photocatalytic and electrocatalytic CO2 reduction systems. We investigated the CO2-capturing abilities of two complexes, fac-Mn(X2bpy)(CO)3(OCH2CH2NR2) and fac-Re(X2bpy)(CO)3(OCH2CH2NR2) (X2bpy = 4,4'-X2-2,2-bipyridine and R = -CH2CH2OH), which work as efficient catalysts for CO2 reduction. Both complexes could efficiently capture CO2 even from Ar gas containing only low concentration of CO2 such as 1% to be converted into fac-M(X2bpy)(CO)3(OC(O)OCH2CH2NR2) (M = Mn and Re). These CO2-capturing reactions proceeded reversibly and their equilibrium constants were >1000. The substituents of X2bpy strongly affected the CO2-capturing abilities of both Mn and Re complexes. The density functional theory (DFT) calculation could be used to estimate the CO2-capturing abilities of the metal complexes in the presence of triethanolamine.

Electrocatalytic reduction of low concentration CO2.

Utilization of low concentration CO2 contained in the exhaust gases from various industries and thermal power stations without the need for energy-consuming concentration processes should be an important technology for solving global warming and the shortage of fossil resources. Here we report the direct electrocatalytic reduction of low concentration CO2 by a Re(i)-complex catalyst that possesses CO2-capturing ability in the presence of triethanolamine. The reaction rate and faradaic efficiency of CO2 reduction were almost the same when using Ar gas containing 10% CO2 or when using pure CO2 gas, and the selectivity of CO formation was very high (98% at 10% CO2). At a concentration of 1% CO2, the Re(i) complex still behaved as a good electrocatalyst; 94% selectivity of CO formation and 85% faradaic efficiency were achieved, and the rate of CO formation was 67% compared to that when using pure CO2 gas. The electrocatalysis was due to the efficient insertion of CO2 into the Re(i)-O bond in fac-[Re(dmb)(CO)3{OC2H4N(C2H4OH)2}] (dmb = 4,4'-dimethyl-2,2'-bipyridine).

Acetylcholine-induced Ciliary Beat of the Human Nasal Mucosa Is Regulated by the Pannexin-1 Channel and Purinergic P2X Receptor.

Background Airway mucociliary transport is an important function for the clearance of inhaled foreign particulates in the respiratory tract. The present study aimed at investigating the regulatory mechanism of acetylcholine (Ach)-induced ciliary beat of the human nasal mucosa in ex vivo. Methods The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic surgery. The mucosa was cut into thin strips, and ciliary movement was observed under a phase-contrast light microscope with a high-speed digital video camera. The sample was alternatively subjected to scanning electron microscopic observation. Results Cilia on the turbinate epithelium were well preserved at the ultrastructural level. The baseline ciliary beat frequency (CBF) was 6.45 ± 0.32 Hz. CBF was significantly increased by stimulation with 100 µM Ach and 100 µM adenosine triphosphate. The Ach-induced CBF increase was completely inhibited by removing extracellular Ca2+. Significant inhibition of the Ach-induced CBF was also observed by the addition of 1 µM atropine, 40 µM 2-aminoethoxydiphenyl borate (inositol trisphosphate [IP3] receptor antagonist), 10 µM carbenoxolone (pannexin-1 blocker), 1 mM probenecid (pannexin-1 blocker), 100 µM pyridoxalphosphate-6-azophenyl-20,40-disulfonic acid (P2X antagonist), and 300 µM flufenamic acid (connexin blocker). Meanwhile, 30 nM bafilomycin A1 (vesicular transport inhibitor) did not inhibit the Ach-induced CBF increase. CONCLUSIONS: These results indicate that the regulatory mechanism of the Ach-induced ciliary beat is dependent on extracellular Ca2+ and involves the muscarinic Ach receptor, IP3 receptor, pannexin-1 channel, purinergic P2X receptor, and connexin channel. We proposed a tentative intracellular signaling pathway of the Ach-induced ciliary beat, in which the pannexin-1-P2X unit may play a central role in ciliary beat regulation.

Comparison of 2 and 4 Intratympanic Steroid Injections in the Treatment of Idiopathic Sudden Sensorineural Hearing Loss.

OBJECTIVE: We studied the effect of intratympanic steroid administration with different total injection times on hearing outcomes in patients with idiopathic sudden sensorineural hearing loss (ISSNHL). METHODS: The subjects were 191 consecutive patients (192 ears) with ISSNHL (hearing level ≥40 dB, interval between onset and treatment ≤30 days). They received systemic prednisolone (100 mg followed by tapered doses) combined with intratympanic injection of dexamethasone (4 mg/ml). Intratympanic injection was performed 4 times (days 1, 2, 4, and 7) in 92 patients (92 ears) or 2 times (days 1 and 2) in 99 patients (100 ears). The hearing outcomes were evaluated at 1 week from the start of treatment and 1 to 2 months after the completion of treatment. RESULTS: There was no significant difference in hearing outcomes between the 4- and 2-injection groups at either time point. Multiple regression analysis also showed that the hearing level after treatment did not depend on the total number of intratympanic steroid injections. CONCLUSION: These results indicate that a protocol using only 2 intratympanic steroid injections exerts a sufficient effect on the hearing outcomes of ISSNHL. This simplified treatment protocol would be greatly beneficial to relieve the physical and mental stress of patients.

Possible contribution of pannexin-1 to capsaicin-induced ATP release in rat nasal columnar epithelial cells.

Current evidence indicates that transient receptor potential (TRP) channel activity involves a relationship between opening of pannexin-1 and release of ATP into the extracellular space. We examined the effects of agonists of thermosensitive TRP channels (TRPM8, TRPA1, TRPV1, and TRPV2) on ATP release from rat nasal mucosa, and measured ciliary beat frequency (CBF) using digital high-speed video imaging. Single-cell patch clamping from dissociated rat nasal columnar epithelial cells was performed to confirm the relationship between pannexin-1 and TRP. We demonstrated that ATP release and CBF were significantly potentiated by the heat-sensitive TRPV1 agonist capsaicin (10 µM), but not by other TRP agonists. Capsaicin-induced ATP release and CBF increase were significantly inhibited by the pannexin-1 blockers carbenoxolone (10 µM) and probenecid (300 µM). In addition, the voltage step-evoked currents in the presence of capsaicin were inhibited by the pannexin-1 blockers in single-cell patch clamping. Our results suggest the participation of TRPV1 and pannexin-1 in the physiologic functions of rat nasal mucosa.

Expressions of TRPVs in the cholesteatoma epithelium.

OBJECTIVE: We have recently proposed a hypothesis that acid leakage through the cholesteatoma epithelium mediates bone resorption in middle ear cholesteatoma. In the present study, we investigated the expressions of transient receptor potential vanilloid (TRPV) channels, which have been shown to play roles in the regulation of epidermal barrier function, in the cholesteatoma epithelium in comparison with the normal skin. METHODS: Cholesteatoma epithelium and postauricular skin were collected from 17 patients with primary acquired middle ear cholesteatoma who underwent tympanomastoidectomy. Expressions of TRPV1, TRPV3, TRPV4, and TRPV6 were explored by fluorescence immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). RESULTS: TRPV1, TRPV3, TRPV4, and TRPV6 mRNAs were all detected by qRT-PCR both in the skin and cholesteatoma tissue. Immunohistochemical staining showed that TRPV1 and TRPV3 were positive in the viable cell layers of the epidermis of the skin, and only TRPV3 was positive in those of the cholesteatoma epithelium. The immunoreactivity for TRPV3 was significantly weaker in cholesteatoma than in the skin. CONCLUSIONS: The lower expression of TRPV3 in cholesteatoma may be one of the mechanisms underlying the increased permeability of this tissue. On the other hand, TRPV1, TRPV4, and TRPV6 are unlikely to be involved in the regulation of epithelial permeability in cholesteatoma.

Acetylcholine-induced ex vivo ATP release from the human nasal mucosa.

OBJECTIVE: The present study aimed at investigating ATP release in response to acetylcholine (Ach) and pharmacologically elucidating the intracellular signal transduction pathway of this reaction in an ex vivo experiment. METHODS: The inferior turbinate mucosa was collected from 21 patients with chronic hypertrophic rhinitis who underwent endoscopic turbinectomy. The mucosa was shaped into a filmy round piece, and incubated with chemical(s) in Hank's balanced salt solution for 10min. After incubation, the ATP concentration was measured by a luciferin-luciferase assay. RESULTS: The baseline release of ATP without stimulus was 57.2±10.3fM. The ATP release was significantly increased by stimulation with 100µM Ach. The Ach-induced ATP release was completely inhibited by removing extracellular Ca2+. Significant inhibition of the Ach-induced ATP release was also observed by the addition of 1µM atropine, 40µM 2-APB, 10µM CBX, and 100µM PPADS, whereas 30nM bafilomycin A1 did not affect the ATP release. CONCLUSION: These results indicate that the Ach-induced ATP release from the human nasal mucosa is dependent on the pannexin-1 channel and purinergic P2X7 receptor, suggesting that these two molecules constitute a local autocrine/paracrine signaling system in the human nasal epithelium.

Presence of osteoclasts in middle ear cholesteatoma: a study of undecalcified bone sections.

CONCLUSIONS: Osteoclasts are unlikely to be involved in bone resorption in middle ear cholesteatoma. OBJECTIVE: The authors searched for osteoclasts in undecalcified bone sections in patients with middle ear cholesteatoma to determine whether and to what extent these cells are involved in this disease. METHODS: Twelve patients, eight men and four women, aged 30-87 years, who underwent tympanomastoidectomy were enrolled. Six patients had primary acquired middle ear cholesteatoma (cholesteatoma group) and the other six patients had other otologic diseases including otosclerosis, non-cholesteatomatous chronic otitis media, adhesive otitis media, perilymphatic fistula and ossicular malformation (control group). The scutum bone was collected during surgery, fixed with ethanol, stained with Villanueva bone stain, and embedded in methyl methacrylate. Five-micrometer-thick sections were prepared and examined under a polarizing microscope. Images were analyzed using a semiautomatic graphics system. RESULTS: No osteoclasts were seen in any of the samples in either group. To avoid the risk of under-estimating the presence of osteoclasts, the number of osteoclasts was considered to be <1 in each sample, and the osteoclast density was calculated. The osteoclast densities in both the cholesteatoma and control groups were significantly lower than the sex- and age-matched standard value of the normal iliac cortical bone (p = .028).

Revision Myringoplasty Using Thin-Sliced Cartilage for Postoperative Reperforation in Patients with Chronic Otitis Media.

Myringoplasty is one of the basic procedures in otologic surgery, and is important to achieve good hearing outcome. The temporal fascia is most widely used and considered to be a stable graft in this procedure, although 10-20% of patients develop reperforation after surgery, which is often hard to repair, even by revision surgery. We herein conducted revision myringoplasty using a cartilage graft to repair postoperative reperforation in 7 patients (8 ears) with chronic otitis media. The patients were 3 males and 4 females, aged 13-80 years with an average of 53.9 years. A cartilage graft was harvested from the tragus, sliced in 0.3 mm thickness with perichondrium attached on one side, and trimmed into an appropriate shape and size. The graft was then underlaid beneath the perforation and fixed with fibrin glue. The operation was Wullstein type I tympanoplasty in 5 ears and myringoplasty in 3 ears, using the temporal fascia in 7 ears and subcutaneous tissue in 1 ear. The postoperative follow-up period ranged from 16 to 44 months with an average of 30.0 months. Perforation of the tympanic membrane was successfully closed in 7 ears (87.5%). Hearing outcome was judged successful in 5 ears (62.5%) according to the criteria of the Otological Society of Japan (postoperative hearing level < 30 dB, hearing gain > 15 dB, or postoperative air-bone gap < 15 dB). These results indicate that cartilage is a stable and reliable graft material for revision myringoplasty to repair postoperative reperforation in patients with chronic otitis media.

Treatment outcome of ion beam therapy in eight patients with head and neck cancers.

Ion beam therapy has enabled us to treat formerly untreatable malignant tumors. The aim of the present study was to investigate the long-term follow-up course of patients with head and neck cancers who received ion beam therapy. The subjects were 8 patients (3 men and 5 women aged 43-78 years) with head and neck cancers who visited our department from 2006 to 2015 and received ion beam therapy. Six patients received carbon ion beam therapy, and the other two patients received proton beam therapy. The medical records of the patients were retrospectively analyzed. The primary site was the nasal and paranasal sinuses in six cases, nasopharynx in one case, and external auditory canal in one case. The histological type was olfactory neuroblastoma, malignant melanoma, and adenoid cystic carcinoma in two cases each, and chondrosarcoma and squamous cell carcinoma in one case each. The exposure dose ranged from 64 to 70.4 GyE. The average follow-up period was 42.0 months. Early adverse events were generally mild, and complete therapeutic response was obtained in all cases. However, five patients developed severe late complications including craniospinal dissemination, osteoradionecrosis of the maxilla and skull base, brain necrosis, and loss of eyesight. Three patients died of distant metastasis, local recurrence and/or brain necrosis within 2 years, and four patients have been surviving with distant metastasis or severe late complications. Ion beam therapy exhibits outstanding antitumor effects, but the severe late complications of the therapy must also be recognized.

Hearing outcome does not depend on the interval of intratympanic steroid administration in idiopathic sudden sensorineural hearing loss.

We studied the effect of intratympanic steroid administration with different intervals on hearing outcomes in patients with idiopathic sudden sensorineural hearing loss (ISSNHL). The subjects were 197 consecutive patients (197 ears) with ISSNHL (hearing level ≥40 dB, interval between onset and treatment ≤30 days). They received systemic administration of prednisolone (100 mg followed by tapered doses) combined with intratympanic injection of dexamethasone (4 mg/ml). Intratympanic injection was performed once a week for 4 weeks in 105 patients (long-interval group), or 4 times in 1 week in 92 patients (short-interval group). The hearing outcomes were evaluated at two points of time: 1 week from the start of treatment, and 1-2 months after the completion of treatment when the hearing level reached a plateau. There was no significant difference in the cure rate, marked-recovery rate, recovery rate, hearing gain, hearing level, or percent hearing improvement between the long- and short-interval groups at either point of time. Multiple regression analysis also showed that the final hearing level did not depend on the interval of intratympanic steroid injection. These results indicate that the hearing outcome of ISSNHL does not improve even if the interval of intratympanic injection is shortened. This implies that a lower total number of intratympanic steroid injections may be as effective as the present protocol.

Obstructive sleep apnea in preschool-aged Japanese children - efficiency of screening using lateral neck radiography.

Conclusions The prevalence of obstructive sleep apnea (OSA) in preschool-aged children diagnosed by the International Classification of Sleep Disorders (ICSD) version 3 criteria was relatively higher than that diagnosed by ICSD-2. Although the assessment of the upper airway by lateral neck radiography was effective for detecting OSA in this age group, this assessment is not recommended for all children as a screening method because of parental concern related to radiation exposure. Objective This study investigated the prevalence of OSA and the screening capacity of lateral neck radiography in community-based preschool-aged children. Methods Parents of 211 children aged 3-6 years were requested to complete the sleep-related questionnaire. Subjects who agreed to further investigations were invited to undergo home type 3 portable monitoring and clinical examination, including radiography. We estimated the prevalence of OSA and evaluated the detection power of radiography for predicting OSA. Results One hundred and eighty-eight (89.1%) subjects completed the questionnaire and 67 (31.8%) agreed to further examinations. The weighted prevalence was 7.3% and 12.8% by ICSD-2 and 3, respectively. Area under the receiver operator curve for the adenoidal/nasopharyngeal and tonsil/pharyngeal ratios measured using radiography was slightly larger than that for tonsil size graded by visual inspection.

Electrical Impedance and Expression of Tight Junction Components of the Nasal Turbinate and Polyp.

PURPOSE: We investigated the electrical impedance and expression of tight junction components of the turbinate mucosa, nasal polyp, and normal skin. PROCEDURES: The inferior turbinate and nasal polyp of patients with chronic rhinosinusitis and the postauricular skin of patients with otitis media were examined. Electrical impedance was measured in vivo using a tissue conductance meter. Expressions of claudin-1 and tricellulin were examined by fluorescence immunohistochemistry and quantitative RT-PCR. RESULTS: Electrical impedance was higher in the skin than in the turbinate and polyp, but did not differ between the turbinate and polyp. Immunoreactivities for claudin-1 and tricellulin were seen in the epithelial/epidermal layer. Expression of claudin-1 was higher in the skin than in the turbinate and polyp. The polyp tended to show higher expression of claudin-1 but showed lower expression of tricellulin than the turbinate. The ratio of claudin-1 to tricellulin was highest in the skin and lowest in the turbinate. The correlation between expressions of the two tight junction components was strongly positive in the skin (r = 0.964) and negative (r = -0.527) in the turbinate and polyp. CONCLUSIONS: These results suggest that the roles of claudin-1 and tricellulin in barrier function may be complementary, and may thereby maintain a constant level of permeability of the mucosal tissues.

Osteoclasts are not activated in middle ear cholesteatoma.

It is unclear whether osteoclasts are present and activated in cholesteatomas. We explored the expression of messenger RNA (mRNA) for osteoclast biomarkers and regulating factors in middle ear cholesteatomas to elucidate the level of osteoclast activity in this disease. Bone powder was collected from 14 patients with cholesteatomatous and noncholesteatomatous chronic otitis media during tympanomastoidectomy, separately from cortical bone of the mastoid (clean bone powder), from bone neighboring cholesteatoma (cholesteatomatous bone powder), and from bone of the air cells and antrum of noncholesteatomatous chronic otitis media patients (noncholesteatomatous bone powder). The samples collected were soaked in TRIzol reagent, and total RNA was extracted and purified by the acid guanidinium thiocyanate-phenol-chloroform method, followed by the use of magnetic bead technology. The sample was then subjected to quantitative reverse transcription polymerase chain reaction for receptor activator of nuclear factor κB (RANK), tartrate-resistant acid phosphatase (TRAP), cathepsin K (CTSK), osteoclast-associated receptor (OSCAR), calcitonin receptor (CALCR), matrix metalloproteinase 9 (MMP9), receptor activator of nuclear factor κB ligand (RANKL), and osteoprotegerin (OPG). There was no significant difference in the expression of TRAP, CTSK, OSCAR, CALCR, MMP9, or OPG among the clean, cholesteatomatous, and noncholesteatomatous bone powder. On the other hand, the expression of RANK and RANKL was significantly lower in the cholesteatomatous bone powder than in the noncholesteatomatous bone powder (P = 0.003 and P = 0.028, respectively). The RANKL mRNA/OPG mRNA ratio did not differ among the three samples. These results indicate that osteoclasts are unlikely to be activated in cholesteatomas. Bone resorption mechanisms not mediated by osteoclasts may need to be reappraised in cholesteatoma research in future studies.