Mechanism of Methylene Blue Inducing the Disulfide Bond Formation of Tubulin-Associated Unit Proteins.

Methylene blue (MB) has recently completed a Phase-3 clinical trial as leuco-methylthioninium (LMT) bis(hydromethanesulfonate) for treating Alzheimer's disease. Herein, we investigated the mechanism underlying the MB inhibition of tubulin-associated unit (tau) aggregation by focusing on tau monomers. We found that MB causes disulfide bond formation, resulting in strong nuclear magnetic resonance chemical shift perturbations in a large area of tau proteins. The oxidized form of MB, namely methylthioninium (MT+), specifically catalyzed the oxidation of cysteine residues in tau proteins to form disulfide bonds directly using O2. This process is independent of the MT+-to-LMT redox cycle. Moreover, MT+ preferentially oxidized C291 and C322 in the lysine-rich R2 and R3 domains. Under in vivo brain physoxia conditions, LMT may convert to MT+, possibly interfering with tau fibrillation via disulfide bond formation.

Targeted Therapies for EGFR Exon 20 Insertion Mutation in Non-Small-Cell Lung Cancer.

Non-small-cell lung cancer (NSCLC) frequently harbors mutations in the epidermal growth factor receptor (EGFR), with exon 20 insertions comprising 1-10% of these mutations. EGFR exon 20 insertions are less responsive to conventional tyrosine kinase inhibitors (TKIs), leading to the development of targeted agents. This review explores key therapeutic agents, such as Amivantamab, Mobocertinib, Poziotinib, Zipalertinib, and Sunvozertinib, which have shown promise in treating NSCLC with EGFR exon 20 insertions. Amivantamab, a bispecific antibody-targeting EGFR and c-MET, demonstrates significant efficacy, particularly when combined with chemotherapy. Mobocertinib, a TKI, selectively targets EGFR exon 20 mutations but faces limitations in efficacy. Poziotinib, another oral TKI, shows mixed results due to mutation-specific responses. Zipalertinib and Sunvozertinib have emerged as potent TKIs with promising clinical data. Despite these advances, challenges in overcoming resistance mutations and improving central nervous system penetration remain. Future research should focus on optimizing first-line combination therapies and enhancing diagnostic strategies for comprehensive mutation profiling.

Melt-quenched carboxylate metal-organic framework glasses.

Although carboxylate-based frameworks are commonly used architectures in metal-organic frameworks (MOFs), liquid/glass MOFs have thus far mainly been obtained from azole- or weakly coordinating ligand-based frameworks. This is because strong coordination bonds of carboxylate ligands to metals block the thermal vitrification pathways of carboxylate-based MOFs. In this study, we present the example of carboxylate-based melt-quenched MOF glasses comprising Mg2+ or Mn2+ with an aliphatic carboxylate ligand, adipate. These MOFs have a low melting temperature (Tm) of 284 °C and 238 °C, respectively, compared to zeolitic-imidazolate framework (ZIF) glasses, and superior mechanical properties in terms of hardness and elastic modulus. The low Tm may be attributed to the flexibility and low symmetry of the aliphatic carboxylate ligand, which raises the entropy of fusion (ΔSfus), and the lack of crystal field stabilization energy on metal ions, reducing enthalpy of fusion (ΔHfus). This research will serve as a cornerstone for the integration of numerous carboxylate-based MOFs into MOF glasses.

Manufacturing of stretchable substrate with biaxial strain control for highly-efficient stretchable solar cells and displays.

There has been significant research focused on the development of stretchable materials that can provide a large area with minimal material usage for use in solar cells and displays. However, most materials exhibit perpendicular shrinkage when stretched, which is particularly problematic for polymer-based substrates commonly used in stretchable devices. To address this issue, biaxial strain-controlled substrates have been proposed as a solution to increase device efficiency and conserve material resources. In this study, we present the design and fabrication of a biaxial strain-controlled substrate with a re-entrant honeycomb structure and a negative Poisson's ratio. Using a precisely machined mold with a shape error of less than 0.15%, we successfully fabricated polydimethylsiloxane substrates with a 500 µm thick re-entrant honeycomb structure, resulting in a 19.1% reduction in perpendicular shrinkage. This improvement translates to a potential increase in device efficiency by 9.44% and an 8.60% reduction in material usage for substrate fabrication. We demonstrate that this design and manufacturing method can be applied to the fabrication of efficient stretchable devices, such as solar cells and displays.

An amphiphilic material arginine-arginine-bile acid promotes α-synuclein amyloid formation.

Amyloid generation plays essential roles in various human diseases, biological functions, and nanotechnology. However, developing efficient chemical and biological candidates for regulating amyloid fibrillation remains difficult because information on the molecular actions of modulators is insufficient. Thus, studies are needed to understand how the intermolecular physicochemical properties of the synthesised molecules and amyloid precursors influence amyloidogenesis. In this study, we synthesised a novel amphiphilic sub-nanosized material, arginine-arginine (RR)-bile acid (BA), by conjugating positively charged RR to hydrophobic BA. The effects of RR-BA on amyloid formation were investigated on α-synuclein (αSN) in Parkinson's disease and on K18 and amyloid-ß (1-42) (Aß42) in Alzheimer's disease. RR-BA showed no appreciable effect on the kinetics of K18 and Aß42 amyloid fibrillation because of their weak and non-specific interactions. However, RR-BA specifically bound to αSN with moderate binding affinity through electrostatic interactions between the positively charged RR and the negatively charged cluster in the C-terminus of αSN. In addition, hydrophobic BA in the αSN-RR-BA complex transiently condensed αSN for primary nucleation, thereby accelerating αSN amyloid fibrillation. We propose an electrostatic binding and hydrophobic condensation model of RR-BA-driven amyloid formation of αSN, which will contribute to the rational design and development of molecules for controlling amyloid aggregation in diverse fields.

Characterization of a new CCCTC-binding factor binding site as a dual regulator of Epstein-Barr virus latent infection.

Distinct viral gene expression characterizes Epstein-Barr virus (EBV) infection in EBV-producing marmoset B-cell (B95-8) and EBV-associated gastric carcinoma (SNU719) cell lines. CCCTC-binding factor (CTCF) is a structural chromatin factor that coordinates chromatin interactions in the EBV genome. Chromatin immunoprecipitation followed by sequencing against CTCF revealed 16 CTCF binding sites in the B95-8 and SNU719 EBV genomes. The biological function of one CTCF binding site (S13 locus) located on the BamHI A right transcript (BART) miRNA promoter was elucidated experimentally. Microscale thermophoresis assay showed that CTCF binds more readily to the stable form than the mutant form of the S13 locus. EBV BART miRNA clusters encode 22 miRNAs, whose roles are implicated in EBV-related cancer pathogenesis. The B95-8 EBV genome lacks a 11.8-kb EcoRI C fragment, whereas the SNU719 EBV genome is full-length. ChIP-PCR assay revealed that CTCF, RNA polymerase II, H3K4me3 histone, and H3K9me3 histone were more enriched at S13 and S16 (167-kb) loci in B95-8 than in the SNU719 EBV genome. 4C-Seq and 3C-PCR assays using B95-8 and SNU719 cells showed that the S13 locus was associated with overall EBV genomic loci including 3-kb and 167-kb region in both EBV genomes. We generated mutations in the S13 locus in bacmids with or without the 11.8-kb BART transcript unit (BART(+/-)). The S13 mutation upregulated BART miRNA expression, weakened EBV latency, and reduced EBV infectivity in the presence of EcoRI C fragment. Another 3C-PCR assay using four types of BART(+/-)·S13(wild-type(Wt)/mutant(Mt)) HEK293-EBV cells revealed that the S13 mutation decreased DNA associations between the 167-kb region and 3-kb in the EBV genome. Based on these results, CTCF bound to the S13 locus along with the 11.8-kb EcoRI C fragment is suggested to form an EBV 3-dimensional DNA loop for coordinated EBV BART miRNA expression and infectivity.

Graphene Antiadhesion Layer for the Effective Peel-and-Pick Transfer of Metallic Electrodes toward Flexible Electronics.

Owing to its exceptional physicochemical properties, graphene has demonstrated unprecedented potential in a wide array of scientific and industrial applications. By exploiting its chemically inert surface endowed with unique barrier functionalities, we herein demonstrate antiadhesive monolayer graphene films for realizing a peel-and-pick transfer process of target materials from the donor substrate. When the graphene antiadhesion layer (AAL) is inserted at the interface between the metal and the arbitrary donor substrate, the interfacial interactions can be effectively weakened by the weak interplanar van der Waals forces of graphene, enabling the effective release of the metallic electrode from the donor substrate. The flexible embedded metallic electrode with graphene AAL exhibited excellent electrical conductivity, mechanical durability, and chemical resistance, as well as excellent performance in flexible heater applications. This study afforded an effective strategy for fabricating high-performance and ultraflexible embedded metallic electrodes for applications in the field of highly functional flexible electronics.

Brushed lubricant-impregnated surfaces (BLIS) for long-lasting high condensation heat transfer.

Recently, lubricant-impregnated surfaces (LIS) have emerged as a promising condenser surface by facilitating the removal of condensates from the surface. However, LIS has the critical limitation in that lubricant oil is depleted along with the removal of condensates. Such oil depletion is significantly aggravated under high condensation heat transfer. Here we propose a brushed LIS (BLIS) that can allow the application of LIS under high condensation heat transfer indefinitely by overcoming the previous oil depletion limit. In BLIS, a brush replenishes the depleted oil via physical contact with the rotational tube, while oil is continuously supplied to the brush by capillarity. In addition, BLIS helps enhance heat transfer performance with additional route to droplet removal by brush sweeping. By applying BLIS, we maintain the stable dropwise condensation mode for > 48 hours under high supersaturation levels along with up to 61% heat transfer enhancement compared to hydrophobic surfaces.

Passive Anti-Flooding Superhydrophobic Surfaces.

Superhydrophobic (SHPo) surfaces can provide high condensation heat transfer due to facilitated droplet removal. However, such high performance has been limited to low supersaturation conditions due to surface flooding. Here, we quantify flooding resistance defined as the rate of increase in the fraction of water-filled cavities with respect to the supersaturation level. Based on the quantitative understanding of surface flooding, we suggest effective anti-flooding strategies through tailoring the nanoscale coating heterogeneity and structure length scale. Experimental verification is conducted using CuO nanostructures having different length scales combined with hydrophobic coatings with different nanoscale heterogeneities. The proposed anti-flooding SHPo can provide a ∼130% enhanced average heat transfer coefficient with ∼14% larger supersaturation range for droplet jumping compared to a previous CuO SHPo. The proposed anti-flooding parameter and the scalable SHPo will help develop high-performance condensers for real-world applications operating in a wide range of supersaturation levels.

Condensation Heat-Transfer Performance of Thermally Stable Superhydrophobic Cerium-Oxide Surfaces.

We introduce a thin (<200 nm) superhydrophobic cerium-oxide surface formed by a one-step wet chemical process to enhance the condensation heat-transfer performance with improved thermal stability compared to silane-treated surfaces. The developed cerium-oxide surface showed a superhydrophobic characteristic with a low (<5°) contact angle hysteresis because of the unique surface morphology and hydrophobicity of cerium oxide. The surface was successfully incorporated to popular engineering materials including copper, aluminum, and steel. Thermal stability of the surfaces was investigated by exposing them to hot (∼100 °C) steam conditions for 12 h. The introduced ceria surfaces could maintain active dropwise condensation after the thermal stability test, whereas silane-treated surfaces completely lost their hydrophobicity. The heat-transfer coefficient was calculated using the thermal network model incorporating the droplet size distribution and morphology obtained from the microscopic measurement. The analysis shows that the suggested cerium-oxide surfaces can provide approximately 2 times and 5 times higher heat-transfer coefficient before and after the thermal stability test, respectively, mainly because of the decrease in the thermal conduction resistance across droplets. The results indicate that the introduced nanostructured cerium-oxide surface is a promising condenser coating to enhance the droplet mobility and the resulting condensation heat-transfer performance for various thermal and environmental applications, especially those being exposed to hot steam conditions.

Euphorbia factor L1 inhibits osteoclastogenesis by regulating cellular redox status and induces Fas-mediated apoptosis in osteoclast.

Excessive bone resorption caused by increased osteoclast number or activity leads to a variety of bone diseases including osteoporosis, rheumatoid arthritis and periodontitis. Thus, the therapeutic strategy for these diseases has been focused primarily on the inhibition of osteoclast formation and function. This study shows that euphorbia factor L1 (EFL1), a diterpenoid isolated from Euphorbia lathyris, inhibited osteoclastogenesis and induced osteoclast apoptosis. EFL1 suppressed osteoclast formation and bone resorption at both initial and terminal differentiation stages. EFL1 inhibited receptor activator of NF-κB ligand (RANKL)-induced NFATc1 induction with attenuated NF-κB activation and c-Fos expression. EFL1 decreased the level of reactive oxygen species by scavenging them or activating Nrf2, and inhibited PGC-1ß that regulates mitochondria biogenesis. In addition, EFL1 induced apoptosis in differentiated osteoclasts by increasing Fas ligand expression followed by caspase activation. Moreover, EFL1 inhibited inflammation-induced bone erosion and ovariectomy-induced bone loss in mice. These findings suggest that EFL1 inhibits osteoclast differentiation by regulating cellular redox status and induces Fas-mediated apoptosis in osteoclast, and may provide therapeutic potential for preventing or treating bone-related diseases caused by excessive osteoclast.

Preparation and in vivo evaluation of an orally available enteric-microencapsulated parathyroid hormone (1-34)-deoxycholic acid nanocomplex.

The N-terminal 34-amino-acid peptide fragment of human parathyroid hormone PTH (1-34), is used clinically to treat osteoporosis; however, it is currently administered by a once-daily subcutaneous injection, resulting in poor patient compliance. We have developed enteric microcapsules containing an ionic nanocomplex between PTH (1-34) and lysine-linked deoxycholic acid (LysDOCA) for the oral delivery of PTH (1-34). We measured the particle size of the PTH/LysDOCA complex and assessed its biological activity by determining the cAMP content in MC3T3-E1 cells. We also assessed its permeability across a Caco-2 cell monolayer and the bioavailability of the intrajejunally administered PTH/LysDOCA complex compared with PTH (1-34) in rats. In addition, the antiosteoporotic activity of the PTH/LysDOCA complex, encapsulated in an enteric carrier by coaxial ultrasonic atomization, was evaluated after it was orally administered to ovariectomized (OVX) rats. The formation of an ionic complex between PTH (1-34) and LysDOCA produced nanoparticles of diameter 33.0±3.36 nm, and the bioactivity of the complex was comparable with that of PTH (1-34). The Caco-2 cell permeability and AUClast value of the PTH/LysDOCA (1:10) nanocomplex increased by 2.87- and 16.3-fold, respectively, compared with PTH (1-34) alone. Furthermore, the OVX rats treated with oral PTH/LysDOCA-loaded enteric microcapsules showed an increase in bone mineral density (159%), bone volume fraction (175%), and trabecular number (174%) compared with those in the OVX control group. Therefore, the PTH/LysDOCA nanocomplex oral delivery system is a promising treatment modality for osteoporosis because it improves osteogenesis and trabecular connectivity.

Effects of yuja peel extract and its flavanones on osteopenia in ovariectomized rats and osteoblast differentiation.

SCOPE: Yuja (Citrus junos Tanaka) possesses various health benefits, but its effects on bone health are unknown. In this study, the preventative effects of yuja peel ethanol extract (YPEE) on osteopenia were determined in ovariectomized (OVX) rats, and the mechanisms by which YPEE and its flavanones regulate osteoblastogenesis were examined in vitro. METHODS AND RESULTS: The effects of YPEE on osteoblastogenesis were investigated in MC3T3-E1 cells. YPEE promoted alkaline phosphatase (ALP) activity, mineralization, and the expression of osteoblast differentiation marker genes, such as ALP, runt-related transcription factor 2 (Runx2), and osteocalcin. YPEE and its flavanones promoted osteoblast differentiation via BMP-2-mediated p38 and the Smad1/5/8 signaling pathway. YPEE supplementation significantly decreased body weight and increased uterine weight and bone mineral density in OVX rats. Based on a micro-CT analysis of femurs, YPEE significantly attenuated osteopenia and increased trabecular volume fraction, trabecular separation, and trabecular number (p < 0.05). CONCLUSION: Dietary YPEE has a protective effect on OVX-induced osteopenia. YPEE and its flavanones promote osteoblastogenesis via the activation of the BMP/p38/Smad/Runx2 pathways. These results extend our knowledge of the beneficial effects of YPEE and provide a basis for the development of novel therapies for osteoporosis.

A novel small-molecule PPI inhibitor targeting integrin αvß3-osteopontin interface blocks bone resorption in vitro and prevents bone loss in mice.

Small molecule-inhibition targeting protein-protein interaction (PPI) is now recognized as an emerging and challenging area in drug design. We developed a novel interactive drug discovery methodology known as Protein Chip technology (ProteoChip) as a cutting-edge PPI assay system applicable for unique PPI-targeting therapeutics integrated with computer-aided drug design (CADD). Here, we describe a novel small molecular PPI inhibitor, IPS-02001, which the blocks integrin αvß3-osteopontin interface a novel PPI inhibitor identified by the interactive methodology of both ProteoChip- and CADD-based PPI assay. IPS-02001 (6,7-Dichloro-2,3,5,8-tetrahydroxy-1,4-naphthoquinone) was screened from different compound libraries (InterBioScreen, Commercial libraries) using an in silico structure-based molecular docking simulation method and a protein chip-based protein-protein interaction assay system. Additionally, integrin αvß3, an adhesion receptor expressed in osteoclasts (OCs), was implicated in the regulation of OC function via regulation of the cytoskeletal organization of OCs. IPS-02001 blocked OC maturation from murine bone marrow-derived macrophages, as well as the resorptive function of OCs. Moreover, treatment with IPS-02001 impaired downstream signaling of integrin αvß3 linked to Pyk2, c-Src, PLCγ2, and Vav3 and disrupted the actin cytoskeleton in mature OCs. Furthermore, IPS-02001 blocked RANKL-induced bone destruction by reducing the number of OCs and protected against ovariectomy-induced bone loss in mice. Thus, IPS-02001 may represent a promising new class of anti-resorptive drugs for treatment of bone diseases associated with increased OC function.

Sirt6 cooperates with Blimp1 to positively regulate osteoclast differentiation.

Global deletion of the gene encoding a nuclear histone deacetylase sirtuin 6 (Sirt6) in mice leads to osteopenia with a low bone turnover due to impaired bone formation. But whether Sirt6 regulates osteoclast differentiation is less clear. Here we show that Sirt6 functions as a transcriptional regulator to directly repress anti-osteoclastogenic gene expression. Targeted ablation of Sirt6 in hematopoietic cells including osteoclast precursors resulted in increased bone volume caused by a decreased number of osteoclasts. Overexpression of Sirt6 led to an increase in osteoclast formation, and Sirt6-deficient osteoclast precursor cells did not undergo osteoclast differentiation efficiently. Moreover, we showed that Sirt6, induced by RANKL-dependent NFATc1 expression, forms a complex with B lymphocyte-induced maturation protein-1 (Blimp1) to negatively regulate expression of anti-osteoclastogenic gene such as Mafb. These findings identify Sirt6 as a novel regulator of osteoclastogenesis by acting as a transcriptional repressor.

The effects of surface wettability on the fog and dew moisture harvesting performance on tubular surfaces.

The efficient water harvesting from air-laden moisture has been a subject of great interest to address world-wide water shortage issues. Recently, it has been shown that tailoring surface wettability can enhance the moisture harvesting performance. However, depending on the harvesting condition, a different conclusion has often been reported and it remains unclear what type of surface wettability would be desirable for the efficient water harvesting under the given condition. Here we compare the water harvesting performance of the surfaces with various wettability under two different harvesting conditions-dewing and fogging, and show that the different harvesting efficiency of each surface under these two conditions can be understood by considering the relative importance of the water capturing and removal efficiency of the surface. At fogging, the moisture harvesting performance is determined by the water removal efficiency of the surface with the oil-infused surfaces exhibiting the best performance. Meanwhile, at dewing, both the water capturing and removal efficiency are crucial to the harvesting performance. And well-wetting surfaces with a lower barrier to nucleation of condensates exhibit a better harvesting performance due to the increasing importance of the water capture efficiency over the water removal efficiency at dewing.

Sirtuin 3 (SIRT3) maintains bone homeostasis by regulating AMPK-PGC-1ß axis in mice.

The mitochondrial sirtuin 3 (SIRT3) is involved in suppressing the onset of multiple pathologies, including cardiovascular disease, fatty liver, age-related hearing loss, and breast cancer. But a physiological role of SIRT3 in bone metabolism is not known. Here we show that SIRT3 is a key regulatory molecule to maintain bone homeostasis. Mice deficient in SIRT3 exhibited severe osteopenia owing to increased numbers of osteoclasts. Osteoclast precursors from Sirt3-/- mice underwent increased osteoclastogenesis in response to receptor activator of nuclear factor-κB ligand (RANKL), an essential cytokine for osteoclast differentiation. SIRT3 expression from RANKL induction depended on the transcription coactivator PGC-1ß (peroxisome proliferator-activated receptor-γ co-activator-1ß) and the nuclear receptor ERRα (estrogen receptor-related receptor α), and that SIRT3 inhibited the differentiation by interfering with the RANKL-induced expression of PGC-1ß. Thus an auto-regulatory feedback mechanism operates to induce its own inhibitor SIRT3 by PGC-1ß. Moreover, Sirt3-/- osteoclast precursors reduced AMP-activated protein kinase (AMPK) phosphorylation through down-regulating the expression of AMPK. Our results suggest that a mitochondrial SIRT3 is an intrinsic inhibitor for RANKL-mediated osteoclastogenesis.

Oral delivery of zoledronic acid by non-covalent conjugation with lysine-deoxycholic acid: In vitro characterization and in vivo anti-osteoporotic efficacy in ovariectomized rats.

We assessed the possibility of changing the route of administration of zoledronic acid to an oral dosage form and its therapeutic efficacy in an estrogen-deficient osteoporosis rat model. To enhance oral bioavailability, we formed an ionic complex by electrostatic conjugation of zoledronic acid with lysine-linked deoxycholic acid (Lys-DOCA, an oral absorption enhancer). After forming the complex, the characteristic crystalline features of pure zoledronic acid disappeared completely in the powder X-ray diffractogram and differential scanning calorimetry thermogram, indicating that zoledronic acid existed in an amorphous form in the complex. In vitro permeabilities of zoledronic acid/Lys-DOCA (1:1) (ZD1) and zoledronic acid/Lys-DOCA (1:2) (ZD2) complex across Caco-2 cell monolayers were 2.47- and 4.74-fold higher than that of zoledronic acid, respectively. Upon intra-jejunal administration to rats, the intestinal absorption of zoledronic acid was increased significantly and the resulting oral bioavailability of the ZD2 complex was determined to be 6.76±2.59% (0.548±0.161% for zoledronic acid). Ovariectomized (OVX) rats showed 122% increased bone mineral density versus the OVX control at 12weeks after treatment with once weekly oral administration of ZD2 complex (16µg/kg of zoledronic acid). Furthermore, rats treated with ZD2 complex orally showed significant improvement in the parameters of trabecular microarchitecture and bone strength: 149% higher bone volume fraction (BV/TV), 115% higher trabecular number (Tb.N), and 56% higher mean maximum load (Fmax) than in the OVX group. The trabecular microstructure and bone mechanical properties in the oral zoledronic acid group were not significantly changed compared with the OVX control. Thus, the oral ZD2 complex inhibited osteoporosis progression effectively by promoting osteogenesis and trabecular connectivity. The oral ZD2 complex would be expected to improve patient compliance by replacing the conventional injectable form and expand the indications, to include prophylaxis for osteoporosis and bone metastases.

Anti-skeletal muscle atrophy effect of Oenothera odorata root extract via reactive oxygen species-dependent signaling pathways in cellular and mouse model.

Skeletal muscle atrophy can be defined as a decrease of muscle volume caused by injury or lack of use. This condition is associated with reactive oxygen species (ROS), resulting in various muscular disorders. We acquired 2D and 3D images using micro-computed tomography in gastrocnemius and soleus muscles of sciatic-denervated mice. We confirmed that sciatic denervation-small animal model reduced muscle volume. However, the intraperitoneal injection of Oenothera odorata root extract (EVP) delayed muscle atrophy compared to a control group. We also investigated the mechanism of muscle atrophy's relationship with ROS. EVP suppressed expression of SOD1, and increased expression of HSP70, in both H2O2-treated C2C12 myoblasts and sciatic-denervated mice. Moreover, EVP regulated apoptotic signals, including caspase-3, Bax, Bcl-2, and ceramide. These results indicate that EVP has a positive effect on reducing the effect of ROS on muscle atrophy.

Decreased Bone Volume and Bone Mineral Density in the Tibial Trabecular Bone Is Associated with Per2 Gene by 405 nm Laser Stimulation.

Low-level laser therapy/treatment (LLLT) using a minimally invasive laser needle system (MILNS) might enhance bone formation and suppress bone resorption. In this study, the use of 405 nm LLLT led to decreases in bone volume and bone mineral density (BMD) of tibial trabecular bone in wild-type (WT) and Per2 knockout (KO) mice. Bone volume and bone mineral density of tibial trabecular bone was decreased by 405 nm LLLT in Per2 KO compared to WT mice at two and four weeks. To determine the reduction in tibial bone, mRNA expressions of alkaline phosphatase (ALP) and Per2 were investigated at four weeks after 405 nm laser stimulation using MILNS. ALP gene expression was significantly reduced in the LLLT-stimulated right tibial bone of WT and Per2 KO mice compared to the non-irradiated left tibia (p < 0.001). Per2 mRNA expression in WT mice was significantly reduced in the LLLT-stimulated right tibial bone compared to the non-irradiated left tibia (p < 0.001). To identify the decrease in tibial bone mediated by the Per2 gene, levels of runt-related transcription factor 2 (Runx2) and ALP mRNAs were determined in non-irradiated WT and Per2 KO mice. These results demonstrated significant downregulation of Runx2 and ALP mRNA levels in Per2 KO mice (p < 0.001). Therefore, the reduction in tibial trabecular bone resulting from 405 nm LLLT using MILNS might be associated with Per2 gene expression.