Impact of the SIK3 pathway inhibition on osteoclast differentiation via oxidative phosphorylation.

Maintenance of bone homeostasis and the balance between bone resorption and formation are crucial for maintaining skeletal integrity. This study sought to investigate the role of salt-inducible kinase 3 (SIK3), a key regulator in cellular energy metabolism, during the differentiation of osteoclasts. Despite osteoclasts being high energy-consuming cells essential for breaking down mineralized bone tissue, the specific function of SIK3 in this process remains unclear. To address this issue, we generated osteoclast-specific SIK3 conditional knockout mice and assessed the impact of SIK3 deletion on bone homeostasis. Our findings revealed that SIK3 conditional knockout mice exhibited increased bone mass and an osteopetrosis phenotype, suggesting a pivotal role for SIK3 in bone resorption. Moreover, we assessed the impact of pterosin B, a SIK3 inhibitor, on osteoclast differentiation. The treatment with pterosin B inhibited osteoclast differentiation, reduced the numbers of multinucleated osteoclasts, and suppressed resorption activity in vitro. Gene expression analysis demonstrated that SIK3 deletion and pterosin B treatment influence a common set of genes involved in osteoclast differentiation and bone resorption. Furthermore, pterosin B treatment altered intracellular metabolism, particularly affecting key metabolic pathways, such as the tricarboxylic acid cycle and oxidative phosphorylation. These results provide valuable insights into the involvement of SIK3 in osteoclast differentiation and the molecular mechanisms underlying osteoclast function and bone diseases.

Osteoporosis is a disease that causes bones to become weak and fragile, increasing the risk of fractures especially in elderly. It is caused by an imbalance between the formation of new bone and the destruction of old bone. Cells called osteoclasts are responsible for breaking down old bone. Excessive osteoclast activity results in bone loss and osteoporosis. Our research has identified a LKB1-SIK3 pathway, which acts as an energy sensor in osteoclasts. We found that this pathway is activated when osteoclast activity is increased, and we were able to reduce osteoclast activity by genetically removing or inhibiting SIK3. These findings suggest that targeting the LKB1-SIK3 pathway may be a promising new approach for the treatment of osteoporosis. Developing drugs that inhibit SIK3 may slow bone loss and reduce the risk of fractures in osteoporotic patients.

Effect of Partial Substitution of Zr for Ti Solvent on Young's Modulus, Strength, and Biocompatibility in Beta Ti Alloy.

In orthopedics and dentistry, there is an urgent need to obtain low-stiffness implants that suppress the stress shielding caused by the use of metallic implants. In this study, we aimed to fabricate alloys that can reduce the stiffness by increasing the strength while maintaining a low Young's modulus based on the metastable ß-Ti alloy. We designed alloys in which Ti was partially replaced by Zr based on the ISO-approved metastable ß-Ti alloy Ti-15Mo-5Zr-3Al. All alloys prepared by arc melting and subsequent solution treatment showed a single ß-phase solid solution, with no formation of the ω-phase. The alloys exhibited a low Young's modulus equivalent to that of Ti-15Mo-5Zr-3Al and a high strength superior to that of Ti-15Mo-5Zr-3Al and Ti-6Al-4V. This strengthening was presumed to be due to solid-solution strengthening. The biocompatibility of the alloys was as good as or better than that of Ti-6Al-4V. These alloys have potential as metallic materials suitable for biomedical applications.

Study on the Fatigue Crack Initiation and Growth Behavior in Bismuth- and Lead-Based Free-Cutting Brasses.

Several studies have been conducted on the fatigue behavior of copper and 7-3, and 6-4 brasses. However, there have been fewer studies on the fatigue behavior and fatigue crack growth (FCG) properties of free-cutting brass, primarily because emphasis has been placed on the development of lead-free free-cutting brass. In this study, fatigue experiments were performed in the atmosphere at room temperature using three types of free-cutting, two types of bismuth (Bi)-based (with different grain sizes), and lead (Pb)-based brasses. It was found that lead-free Bi-based free-cutting brass had approximately the same fatigue performance as that of Pb-based free-cutting brass. It was also clarified that the addition of Bi or Pb initiated fatigue cracks, and that the crack growth period occupied most of the fatigue life. Differences in the FCG behavior of the three free-cutting brasses were observed in the low ΔK range. The modified linear fracture mechanics parameter M was used to quantitatively analyze the fatigue life and FCG behavior (short surface cracks). A comparison between the calculated and experimental results showed that M was useful.

Association of Ligamentum Flavum Hypertrophy with Adolescent Idiopathic Scoliosis Progression-Comparative Microarray Gene Expression Analysis.

The role of the ligamentum flavum (LF) in the pathogenesis of adolescent idiopathic scoliosis (AIS) is not well understood. Using magnetic resonance imaging (MRI), we investigated the degrees of LF hypertrophy in 18 patients without scoliosis and on the convex and concave sides of the apex of the curvature in 22 patients with AIS. Next, gene expression was compared among neutral vertebral LF and LF on the convex and concave sides of the apex of the curvature in patients with AIS. Histological and microarray analyses of the LF were compared among neutral vertebrae (control) and the LF on the apex of the curvatures. The mean area of LF in the without scoliosis, apical concave, and convex with scoliosis groups was 10.5, 13.5, and 20.3 mm2, respectively. There were significant differences among the three groups (p < 0.05). Histological analysis showed that the ratio of fibers (Collagen/Elastic) was significantly increased on the convex side compared to the concave side (p < 0.05). Microarray analysis showed that ERC2 and MAFB showed significantly increased gene expression on the convex side compared with those of the concave side and the neutral vertebral LF cells. These genes were significantly associated with increased expression of collagen by LF cells (p < 0.05). LF hypertrophy was identified in scoliosis patients, and the convex side was significantly more hypertrophic than that of the concave side. ERC2 and MAFB genes were associated with LF hypertrophy in patients with AIS. These phenomena are likely to be associated with the progression of scoliosis.

Direct Reprogramming and Induction of Human Dermal Fibroblasts to Differentiate into iPS-Derived Nucleus Pulposus-like Cells in 3D Culture.

Intervertebral disc (IVD) diseases are common spinal disorders that cause neck or back pain in the presence or absence of an underlying neurological disorder. IVD diseases develop on the basis of degeneration, and there are no established treatments for degeneration. IVD diseases may therefore represent a candidate for the application of regenerative medicine, potentially employing normal human dermal fibroblasts (NHDFs) induced to differentiate into nucleus pulposus (NP) cells. Here, we used a three-dimensional culture system to demonstrate that ectopic expression of MYC, KLF4, NOTO, SOX5, SOX6, and SOX9 in NHDFs generated NP-like cells, detected using Safranin-O staining. Quantitative PCR, microarray analysis, and fluorescence-activated cell sorting revealed that the induced NP cells exhibited a fully differentiated phenotype. These findings may significantly contribute to the development of effective strategies for treating IVD diseases.

Protective Effect of Green Perilla-Derived Chalcone Derivative DDC on Amyloid ß Protein-Induced Neurotoxicity in Primary Cortical Neurons.

Amyloid ß protein (Aß) causes neurotoxicity and cognitive impairment in Alzheimer's disease (AD). Oxidative stress is closely related to the pathogenesis of AD. We have previously reported that 2',3'-dihydroxy-4',6'-dimethoxychalcone (DDC), a component of green perilla, enhances cellular resistance to oxidative damage through the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway. Here, we investigated the effects of DDC on cortical neuronal death induced by Aß. When Aß and DDC had been preincubated for 3 h, the aggregation of Aß was significantly suppressed. In this condition, we found that DDC provided a neuroprotective action on Aß-induced cytotoxicity. Treatment with DDC for 24 h increased the expression of heme oxygenase-1 (HO-1), and this was controlled by the activation of the Nrf2-ARE pathway. However, DDC did not affect Aß-induced neuronal death under any of these conditions. These results suggest that DDC prevents the aggregation of Aß and inhibits neuronal death induced by Aß, and although it activates the Nrf2-ARE pathway, this mechanism is less involved its neuroprotective effect.

Pharmacokinetics and Pharmacodynamics of Once-Daily Tacrolimus Compared With Twice-Daily Tacrolimus in the Early Stage After Living Donor Liver Transplantation.

BACKGROUND: This study investigates the pharmacokinetics and pharmacodynamics of tacrolimus using the once-daily (OD) formulation in the early stage after living donor liver transplantation (LDLT) in comparison with those using the twice-daily (TD) formulation. METHODS: Nine patients undergoing primary LDLT and treated with the OD tacrolimus formulation were included. The trough blood concentration (C0) of tacrolimus was monitored every day for 3 weeks after LDLT. A time course study of the blood tacrolimus concentrations and calcineurin (CN) phosphatase activity in peripheral blood mononuclear cells was performed 3 weeks after LDLT. Pharmacokinetic and pharmacodynamic parameters were compared with previously reported data using the TD formulation. RESULTS: The interindividual variability in the daily dose of tacrolimus was significantly larger in the OD formulation than in the TD formulation (P < 0.001). In the time course study, the tacrolimus blood concentrations at 4, 8, and 12 hours after administration and the area under the concentration-time curve from 0 to 24 hours (AUC0-24) in the OD group were significantly higher than in the TD group, although the C0 was equivalent. In addition, the C0 was not significantly correlated with the AUC0-24 in the OD formulation. The apparent clearance and the pharmacodynamic parameters examined were not significantly different between the OD and TD groups. CONCLUSIONS: The C0 monitoring of the OD formulation may not be optimal in patients at the early stage after LDLT because the C0 was not correlated with the AUC0-24. If clinicians target the same C0 using the OD and TD formulations, the exposure of tacrolimus can be higher in the OD formulation, and excessive immunosuppression should be noted. Particular attention should be paid to the patients in the early stage after LDLT in the use of the OD oral formulation of tacrolimus.

Non-toxic conformer of amyloid ß may suppress amyloid ß-induced toxicity in rat primary neurons: implications for a novel therapeutic strategy for Alzheimer's disease.

The 42-mer amyloid ß-protein (Aß42) oligomers cause neurotoxicity and cognitive impairment in Alzheimer's disease (AD). We previously identified the toxic conformer of Aß42 with a turn at positions 22-23 ("toxic" turn) to form oligomers and to induce toxicity in rat primary neurons, along with the non-toxic conformer with a turn at positions 25-26. G25P-Aß42 and E22V-Aß42 are non-toxic mutants that disfavor the "toxic" turn. Here we hypothesize that these non-toxic mutants of Aß42 could suppress Aß42-induced neurotoxicity, and examined their effects on the neurotoxicity, aggregation, and levels of the toxic conformer, which was evaluated by dot blotting using a monoclonal antibody (11A1) against the toxic conformer. G25P-Aß42 and E22V-Aß42 suppressed the neurotoxicity and aggregation of Aß42 as well as the formation of the toxic conformer. The neurotoxicity induced by Aß42 was also significantly reduced by the treatment of 11A1, but not of Aß-sequence specific antibodies (6E10 and 4G8). Since recent studies indicate that Aß oligomers contain parallel ß-sheet, the present results suggest that the non-toxic mutants of Aß42 without the "toxic" turn could prevent the propagation process of the toxic conformer of Aß42 resulting in suppression of the formation of the toxic oligomers. This could be a promising strategy for AD therapeutics.