Pharmacological effects of methysticin and L-sulforaphane through the Nrf2/ARE signaling pathway in MLO-Y4 osteocytes: in vitro study.

BACKGROUND: Oxidative stress plays a crucial role in the pathogenesis of many skeletal diseases by inducing osteocyte death. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of various antioxidant gene expressions through antioxidant response element (ARE) against cellular oxidative stress and can be induced by various stimulants, including the phytochemicals methysticin (MET) and L-sulforaphane (SFN). This study aimed to establish an osteocyte in vitro model to investigate the pharmacological effects of MET and SFN on the Nrf2/ARE pathway. METHODS: MLO-Y4 murine osteocytes and the stably transduced MLO-Y4-SIN-lenti-ARE reporter gene cell line were used. MET and SFN were used as Nrf2 inducers. The cytotoxicity of MET, SFN, and hydrogen peroxide (H2O2) was evaluated using the CytoTox-Glo™ Assay. Time- and dose-dependent ARE induction was examined by Monoluciferase Assay. The mRNA and protein expressions of Nrf2 target markers, such as heme-oxygenase 1 (Ho-1), NADPH quinone dehydrogenase 1 (Nqo1), and thioredoxin reductase 1 (Txnrd1), were detected by RT-qPCR, Western Blot, and immunofluorescence staining, respectively. Osteogenesis markers, osteopontin, and osteocalcin were compared with and without treatment by immunofluorescence staining. RESULTS: The experimental data showed that MET and SFN induced ARE activity in a time- and dose-dependent manner and increased the mRNA and protein expression of antioxidant markers compared to vehicle-treated controls. The protein expression of osteopontin and osteocalcin in the samples treated with SFN were significantly higher than without treatment, and the number of cell death treated with SFN was significantly lower than without treatment under H2O2-induced stress conditions. CONCLUSIONS: Nrf2 inducers MET and SFN increased the mRNA expression of antioxidant genes through the Nrf2/ARE pathway in osteocytes. Notably, SFN increased the protein expression of osteocyte-associated osteogenic markers and suppressed cell death under H2O2-induced stress condition. Thus, Nrf2 stimulators can exert stress-relieving and osteogenic effects on osteocytes.

Influence of blood lactate variations and passive exercise on cardiac responses.

[Purpose] This study aimed to investigate cardiovascular responses, including heart rate (HR) and heart rate variability (HRV), to various hyperlactatemia-passive exercise interactions. [Participants and Methods] Nine healthy male participants performed upper limb passive cycling movement, and their HR and HRV were assessed while their blood lactate levels were manipulated by sustained handgrip exercise at control, 15% maximum voluntary contraction (MVC), and 30% MVC, followed by postexercise circulatory occlusion. [Results] HR and root mean squared standard difference (rMSSD) of HRV response remained constant at all blood lactate levels during passive exercise (HR: control, 75.8 ± 3.4 bpm; 15% MVC, 76.9 ± 2.7 bpm; and 30% MVC, 77.0 ± 3.7 bpm; rMSSD: control, 33.2 ± 6.9 ms; 15% MVC, 36.3 ± 7.3 ms; and 30% MVC, 37.3 ± 8.9 ms). [Conclusion] Manipulating metaboreflex activation did not significantly alter HR or HRV during passive exercise. These results suggest that, in healthy participants, the interactions between mechanical and metabolic stimuli do not affect HR and HRV responses, implying that passive exercise may be safely implemented.

Error of intraoperative measurement of stem anteversion is decreased by measuring in neutral hip position during total hip arthroplasty.

BACKGROUND: Intraoperative stem anteversion, which is the angle between the lower leg axis and the trial-stem axis with hip flexion and adduction, is generally evaluated by the surgeon's visual estimation during total hip arthroplasty (THA). However, the conventional approach can be influenced by knee osteoarthritis or uncertain surgeon's observation point. Therefore, we developed a new method for measuring the stem anteversion angle in the neutral hip position using an original rod attached to the trial-stem perpendicular to the long axis and parallel to the stem neck. This study aimed to assess the accuracy of our method in comparison with the conventional method of measuring intraoperative stem anteversion angle. METHODS: We measured the intraoperative stem anteversion angle in consecutive 106 hips of 106 patients who underwent cementless primary THA with a tapered wedge stem. Absolute error in the stem anteversion angle was expressed as the difference between intraoperative (common vs. neutral hip positions) and postoperative computed tomography measurements, i.e., true stem anteversion. Additionally, we investigated the factors affecting these errors. RESULTS: The absolute error of measurement was significantly smaller in the neutral hip position than in the common position (3.0° ± 2.5° vs. 8.0° ± 3.9°; p < 0.0001). The factor associated with the error was advanced knee osteoarthritis in the common position, whereas it was not statistically significant in the neutral hip position. CONCLUSIONS: This study suggests that the error in the intraoperative measurement of stem anteversion is decreased by measuring in the neutral hip position during THA.

The Contribution of the Nrf2/ARE System to Mechanotransduction in Musculoskeletal and Periodontal Tissues.

Mechanosensing plays an essential role in maintaining tissue functions. Across the human body, several tissues (i.e., striated muscles, bones, tendons, ligaments, as well as cartilage) require mechanical loading to exert their physiological functions. Contrary, mechanical unloading triggers pathological remodeling of these tissues and, consequently, human body dysfunctions. At the cellular level, both mechanical loading and unloading regulate a wide spectrum of cellular pathways. Among those, pathways regulated by oxidants such as reactive oxygen species (ROS) represent an essential node critically controlling tissue organization and function. Hence, a sensitive balance between the generation and elimination of oxidants keeps them within a physiological range. Here, the Nuclear Factor-E2-related factor 2/Antioxidant response element (Nrf2/ARE) system plays an essential role as it constitutes the major cellular regulation against exogenous and endogenous oxidative stresses. Dysregulations of this system advance, i.a., liver, neurodegenerative, and cancer diseases. Herein, we extend our comprehension of the Nrf2 system to the aforementioned mechanically sensitive tissues to explore its role in their physiology and pathology. We demonstrate the relevance of it for the tissues' functionality and highlight the imperative to further explore the Nrf2 system to understand the physiology and pathology of mechanically sensitive tissues in the context of redox biology.

Effects of n-3 polyunsaturated fatty acid supplementation on quadriceps weakness immediately after total knee arthroplasty: a pilot, randomized, open-label clinical trial.

[Purpose] Severe quadriceps weakness immediately after total knee arthroplasty can be problematic. The n-3 long-chain polyunsaturated fatty acids have antioxidant and anti-inflammatory effects against ischemia-reperfusion injury, whereas n-6 long-chain polyunsaturated fatty acids exert pro-inflammatory effects, thereby promoting ischemia-reperfusion injury. [Participants and Methods] We explored the efficacy of preoperative n-3 long-chain polyunsaturated fatty acid supplementation against early quadriceps weakness among 20 patients scheduled for total knee arthroplasty (intervention group, n=10; control group, n=10). The intervention group received 645 mg of eicosapentaenoic acid) and 215 mg of docosahexaenoic acid daily for 30 days preoperatively. Serum eicosapentaenoic acid, docosahexaenoic acid, and arachidonic acid levels were measured preoperatively. We compared serum derivatives of reactive oxygen metabolites as oxidative stress biomarkers, knee circumference, thigh volume, knee pain during the quadriceps strength test, and quadriceps strength preoperatively and 4 days postoperatively to quantify the change. [Results] Preoperative n-3 long-chain polyunsaturated fatty acid supplementation significantly increased the (eicosapentaenoic acid+docosahexaenoic acid)/arachidonic acid ratio in the intervention group. A significantly lower increase in quadriceps weakness was exhibited in the intervention group than in the control group. However, changes in oxidative stress, knee/thigh swelling, and knee pain during strength testing did not significantly differ between the two groups. [Conclusion] Preoperative n-3 long-chain polyunsaturated fatty acid supplementation exhibited beneficial effects on quadriceps weakness immediately after total knee arthroplasty.

Effect of Lower Limb Venous Dilation on the Autonomic Cardiac Response among Healthy Young Men.

Venous occlusion of the lower limbs, which simulates edema, can alter heart rate variability (HRV) by increasing feedback information from group III/IV sensory fibers. Our aim was to quantify this effect among healthy young men. The study group included 13 men (mean age, 20.4 years). Venous occlusion of the lower limbs was induced using a pressure cuff around both thighs. The effect of occlusion on autonomic cardiac response was quantified under occlusion pressures of 20, 60, and 100 mmHg. Compression was applied for 5 min. HRV was evaluated from changes in the low-frequency (LF) and high-frequency (HF) power of the electrocardiogram and the resulting LF/HF balance. Near-infrared spectroscopy of the leg was used to quantify the effects of occlusion on deoxyhemoglobin, measured as the area under the curve (HHb-AUC). The occlusion pressure of 100 mmHg induced a significant increase in the LF/HF ratio, compared to the baseline (p < 0.05). HHb-AUC was highest for the 100 mmHg occlusion pressure compared with the 20 and 60 mmHg pressures (p < 0.01). These findings indicate that venous dilation may elicit a shift towards sympathetic dominance in the autonomic balance.

Nuclear factor erythroid 2-related factor 2 (Nrf2) deficiency causes age-dependent progression of female osteoporosis.

BACKGROUND: Nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial transcription factor for cellular redox homeostasis. The association of Nrf2 with elderly female osteoporotic has yet to be fully described. The aim was to elucidate a potential age-dependent Nrf2 contribution to female osteoporosis in mice. METHODS: Eighteen female wild type (WT) and 16 Nrf2-knockout (KO) mice were sacrificed at different ages (12 weeks = young mature adult and 90 weeks = old) to analyze their femurs. The morphological properties (trabecular and cortical) were evaluated by micro-computed tomography (µCT) and compared to gold standard histochemistry analysis. The quasi-static compression tests were performed to calculate the mechanical properties of bones. Additionally, the population of bone resorbing cells and aromatase expression by osteocytes was immunohistochemically evaluated and empty osteocyte lacunae was counted in cortical bone. RESULTS: Old Nrf2-KO mice revealed a significantly reduced trabecular bone mineral density (BMD), cortical thickness, cortical area, and bone fraction compared to old WT mice, regardless of no significant difference in skeletally mature young adult mice between WT and KO. Specifically, while all old WT mice showed thin metaphyseal trabeculae, trabecular bone was completely absent in 60% of old KO mice. Additionally, old KO mice showed significantly more osteoclast-like cells and fewer aromatase-positive osteocytes than WT mice, whereas the occurrence of empty osteocyte lacunae did not differ between both groups. Nrf2-KO mice further showed an age-dependently reduced fracture resilience compared to age-matched WT mice. CONCLUSION: Our results suggest that chronic Nrf2 loss can lead to age-dependent progression of female osteoporosis.

Validity of anaerobic threshold measured in resistance exercise.

[Purpose] Intensity for resistance exercise is estimated based on the maximum muscle strength. Exercise prescription without evaluating the biological response has a challenge. This study aimed to confirm whether anaerobic threshold measured using cardiopulmonary exercise test in resistance exercise is appropriate or not. [Participants and Methods] Resistance exercise adopted for the study was right-leg knee extension. The participants were 10 healthy young males. We investigated whether the oxygen uptake kinetics achieved a steady state within 3 min during the constant-load test with knee extension at 80% anaerobic threshold using cardiopulmonary exercise test with knee extension. If oxygen uptake kinetics achieved a steady state within 3 min, the exercise intensity measured using cardiopulmonary exercise test was considered appropriate. [Results] Anaerobic threshold was measured using the conventional approach in all participants. The steady state of oxygen uptake kinetics could be achieved within 3 min. In the constant-load test with knee extension at 80% anaerobic threshold, the oxygen uptake kinetics achieved a steady state within 3 min. [Conclusion] Based on the findings, the anaerobic threshold obtained using cardiopulmonary exercise test with resistance exercise was judged as appropriate. The results of this study contribute to the accurate setting of exercise load for resistance exercise and condition setting for the evaluation of skeletal muscle function.

Platelet-Released Growth Factors Influence Wound Healing-Associated Genes in Human Keratinocytes and Ex Vivo Skin Explants.

Platelet-released growth factors (PRGFs) or other thrombocyte concentrate products, e.g., Platelet-Rich Fibrin (PRF), have become efficient tools of regenerative medicine in many medical disciplines. In the context of wound healing, it has been demonstrated that treatment of chronic or complicated wounds with PRGF or PRF improves wound healing in the majority of treated patients. Nevertheless, the underlying cellular and molecular mechanism are still poorly understood. Therefore, we aimed to analyze if PRGF-treatment of human keratinocytes caused the induction of genes encoding paracrine factors associated with successful wound healing. The investigated genes were Semaphorin 7A (SEMA7A), Angiopoietin-like 4 (ANGPLT4), Fibroblast Growth Factor-2 (FGF-2), Interleukin-32 (IL-32), the CC-chemokine-ligand 20 (CCL20), the matrix-metalloproteinase-2 (MMP-2), the chemokine C-X-C motif chemokine ligand 10 (CXCL10) and the subunit B of the Platelet-Derived Growth Factor (PDGFB). We observed a significant gene induction of SEMA7A, ANGPLT4, FGF-2, IL-32, MMP-2 and PDGFB in human keratinocytes after PRGF treatment. The CCL20- and CXCL10 gene expressions were significantly inhibited by PRGF therapy. Signal transduction analyses revealed that the PRGF-mediated gene induction of SEMA7A, ANGPLT4, IL-32 and MMP-2 in human keratinocytes was transduced via the IL-6 receptor pathway. In contrast, EGF receptor signaling was not involved in the PRGF-mediated gene expression of analyzed genes in human keratinocytes. Additionally, treatment of ex vivo skin explants with PRGF confirmed a significant gene induction of SEMA7A, ANGPLT4, MMP-2 and PDGFB. Taken together, these results describe a new mechanism that could be responsible for the beneficial wound healing properties of PRGF or related thrombocytes concentrate products such as PRF.

Nrf2/ARE Signaling Directly Regulates SOX9 to Potentially Alter Age-Dependent Cartilage Degeneration.

Oxidative stress is implicated in osteoarthritis, and nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway maintains redox homeostasis. We investigated whether Nrf2/ARE signaling controls SOX9. SOX9 expression in human C-28/I2 chondrocytes was measured by RT-qPCR after shRNA-mediated knockdown of Nrf2 or its antagonist the Kelch-like erythroid cell-derived protein with cap ''n'' collar homology-associated protein 1 (Keap1). To verify whether Nrf2 transcriptionally regulates SOX9, putative ARE-binding sites in the proximal SOX9 promoter region were inactivated, cloned into pGL3, and co-transfected with phRL-TK for dual-luciferase assays. SOX9 promoter activities without and with Nrf2-inducer methysticin were compared. Sox9 expression in articular chondrocytes was correlated to cartilage thickness and degeneration in wild-type (WT) and Nrf2-knockout mice. Nrf2-specific RNAi significantly decreased SOX9 expression, whereas Keap1-specific RNAi increased it. Putative ARE sites (ARE1, ARE2) were identified in the SOX9 promoter region. ARE2 mutagenesis significantly reduced SOX9 promoter activity, but ARE1 excision did not. Functional ARE2 site was essential for methysticin-mediated induction of SOX9 promoter activity. Young Nrf2-knockout mice revealed significantly lower Sox9-positive chondrocytes, and old Nrf2-knockout animals showed thinner cartilage and more cartilage degeneration. Our results suggest Nrf2 directly regulates SOX9 in articular cartilage, and Nrf2-loss can develop mild osteoarthritis at old age. Pharmacological Nrf2 induction may hold the potential to diminish age-dependent cartilage degeneration through improving SOX9 expression.

Platelet-Released Growth Factors Induce Genes Involved in Extracellular Matrix Formation in Human Fibroblasts.

Platelet concentrate products are increasingly used in many medical disciplines due to their regenerative properties. As they contain a variety of chemokines, cytokines, and growth factors, they are used to support the healing of chronic or complicated wounds. To date, underlying cellular mechanisms have been insufficiently investigated. Therefore, we analyzed the influence of Platelet-Released Growth Factors (PRGF) on human dermal fibroblasts. Whole transcriptome sequencing and gene ontology (GO) enrichment analysis of PRGF-treated fibroblasts revealed an induction of several genes involved in the formation of the extracellular matrix (ECM). Real-time PCR analyses of PRGF-treated fibroblasts and skin explants confirmed the induction of ECM-related genes, in particular transforming growth factor beta-induced protein (TGFBI), fibronectin 1 (FN1), matrix metalloproteinase-9 (MMP-9), transglutaminase 2 (TGM2), fermitin family member 1 (FERMT1), collagen type I alpha 1 (COL1A1), a disintegrin and metalloproteinase 19 (ADAM19), serpin family E member 1 (SERPINE1) and lysyl oxidase-like 3 (LOXL3). The induction of these genes was time-dependent and in part influenced by the epidermal growth factor receptor (EGFR). Moreover, PRGF induced migration and proliferation of the fibroblasts. Taken together, the observed effects of PRGF on human fibroblasts may contribute to the underlying mechanisms that support the beneficial wound-healing effects of thrombocyte concentrate products.

Activation of the Prefrontal Cortex and Improvement of Cognitive Performance with Standing on One Leg.

The prefrontal cortex (PFC) is involved in attention, motor planning, and executive functions. In addition, it is known that postural control and cognitive performance are affected during dual-task paradigms, suggesting that postural control and cognition use common areas of the brain. Although postural control and cognition have been used as interfering dual tasks, the neuronal mechanisms underlying interference are not fully understood. We simultaneously performed postural and cognitive tasks in healthy young adults and evaluated activity in the PFC using near-infrared spectrometry. The displacement of the center of pressure (COP) is reduced by cognitive tasks. Difficult postural tasks increased the relative proportion and amplitude of postural sway in the high-frequency bandwidth, related to the adjustment of postural sway. Although the cognitive tasks did not affect the relative proportion of each frequency bandwidth, the amplitudes were selectively reduced. The postural task-dependent change in PFC activity was correlated with the relative proportion and amplitude of postural sway in the high-frequency bandwidth of the COP movement. Cognitive task-dependent changes in PFC activity were not correlated with postural sway. Cognitive performance was better in unipedal standing than bipedal standing. These findings suggest that postural tasks affect cognitive performance via the activation of the PFC, but cognitive tasks affect postural control through a different mechanism.

Association between pulmonary oxygen uptake on-kinetics and acute cardiovascular responses to resistance exercise in patients with coronary artery disease: a preliminary study.

[Purpose] This study aimed to examine whether pulmonary oxygen uptake on-kinetics at the onset of moderate-intensity exercise can predict acute cardiovascular responses to resistance exercise. [Participants and Methods] The association between pulmonary oxygen uptake on-kinetics and acute cardiovascular responses to a single resistance exercise session was investigated in seven patients with low-risk coronary artery disease who underwent revascularization through percutaneous coronary intervention. The participants performed a cardiopulmonary exercise test on a cycle ergometer and a single resistance exercise session at 30% of maximum voluntary contraction on a bilateral leg-extension machine 1 week after surgery. We measured the ventilatory anaerobic threshold and pulmonary oxygen uptake on-kinetics during the cardiopulmonary exercise test; left ventricular ejection fraction at rest; and heart rate, systolic blood pressure, and rate pressure product during the single resistance exercise session. [Results] Pulmonary oxygen uptake on-kinetics showed a positive association with the amount of increase in systolic blood pressure and rate pressure product during the single resistance exercise session, but had no association with the amount of increase in heart rate. Ventilatory anaerobic threshold and left ventricular ejection fraction were not associated with these parameters. [Conclusion] These data suggested that pulmonary oxygen uptake on-kinetics can be a useful evaluation index for predicting acute systolic blood pressure and rate pressure product responses to low-intensity resistance exercise 1 week after percutaneous coronary intervention in patients with low-risk coronary artery disease.

Association between Preoperative Long-Chain Polyunsaturated Fatty Acids and Oxidative Stress Immediately after Total Knee Arthroplasty: A Pilot Study.

Quadriceps muscle atrophy following total knee arthroplasty (TKA) can be caused by tourniquet-induced ischemia-reperfusion (IR) injury, which is often accompanied by oxidative stress and inflammatory responses. n-3 long-chain polyunsaturated fatty acids (LCPUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), exert antioxidant and anti-inflammatory effects against IR injury, whereas n-6 LCPUFAs, particularly arachidonic acid (AA), exhibit pro-inflammatory effects and promote IR injury. This study aimed to examine whether preoperative serum EPA + DHA levels and the (EPA + DHA)/AA ratio are associated with oxidative stress immediately after TKA. Fourteen eligible patients with knee osteoarthritis scheduled for unilateral TKA participated in this study. The levels of serum EPA, DHA, and AA were measured immediately before surgery. Derivatives of reactive oxygen metabolites (d-ROMs) were used as biomarkers for oxidative stress. The preoperative serum EPA + DHA levels and the (EPA + DHA)/AA ratio were found to be significantly negatively correlated with the serum d-ROM levels at 96 h after surgery, and the rate of increase in serum d-ROM levels between baseline and 96 h postoperatively. This study suggested the preoperative serum EPA + DHA levels and the (EPA + DHA)/AA ratio can be negatively associated with oxidative stress immediately after TKA.

Platelet-released growth factors protect articular chondrocytes from inflammatory condition.

BACKGROUND: Although platelet-released growth factors (PRGF) can protect cells from inflammation or oxidative stress condition, their therapeutic efficacy for articular cartilage degeneration has been little discussed. The purpose of this study was to investigate the effect of PRGF on human articular chondrocytes under inflammatory conditions. METHODS: Human C-28/I2 chondrocytes were treated with PRGF, the production from liquid-preserved platelet concentrates obtained by platelet apheresis from human volunteers. Cell proliferation/viability, and collagen type (COL) II and SOX9 gene expressions for chondrogenesis were evaluated with different PRGF concentrations. Additionally, in vitro inflammatory condition was mimicked by stimulating the cells with tumor necrosis factor (TNF)-α. Under inflammation, cell viability, TNF-α gene expression, and the protein levels of cytokines including TNF-α, interleukin (IL)-1ß and -6, and vascular endothelial growth factor (VEGF) angiogenesis marker, were compared with and without PRGF treatment. RESULTS: Cell proliferation/viability, and SOX9 and COL II expressions in chondrocytes stimulated with 10% PRGF were significantly higher than without treatment. Cell viability with 10% PRGF was also statistically higher than without treatment under inflammation. The TNF-α gene expression with 10% PRGF was significantly lower than without treatment under inflammation. The protein levels of endogenous TNF-α with 5% PRGF, IL-1ß with 10% PRGF, and IL-6 with 5 and 10% PRGF in chondrocytes were significantly lower than untreated ones under inflammation. The VEGF-protein level in chondrocytes stimulated with 20% PRGF was significantly higher than without treatment under inflammation, while there was no significant difference between with 10% PRGF and without treatment. CONCLUSIONS: Our results reveal that optimal PRGF treatment leads to the increase of chondrocyte proliferation/viability and chondrogenic markers, while it increased cell viability but reduced IL-1ß and IL-6 expressions under inflammatory condition, suggesting the therapeutic role of PRGF for protection from articular cartilage degeneration through anti-inflammatory effects.

The Role of Adipose Stem Cells in Bone Regeneration and Bone Tissue Engineering.

Bone regeneration is a complex process that is influenced by tissue interactions, inflammatory responses, and progenitor cells. Diseases, lifestyle, or multiple trauma can disturb fracture healing, which might result in prolonged healing duration or even failure. The current gold standard therapy in these cases are bone grafts. However, they are associated with several disadvantages, e.g., donor site morbidity and availability of appropriate material. Bone tissue engineering has been proposed as a promising alternative. The success of bone-tissue engineering depends on the administered cells, osteogenic differentiation, and secretome. Different stem cell types offer advantages and drawbacks in this field, while adipose-derived stem or stromal cells (ASCs) are in particular promising. They show high osteogenic potential, osteoinductive ability, and immunomodulation properties. Furthermore, they can be harvested through a noninvasive process in high numbers. ASCs can be induced into osteogenic lineage through bioactive molecules, i.e., growth factors and cytokines. Moreover, their secretome, in particular extracellular vesicles, has been linked to fracture healing. The aim of this review is a comprehensive overview of ASCs for bone regeneration and bone tissue engineering.

Adverse Effects of Oxidative Stress on Bone and Vasculature in Corticosteroid-Associated Osteonecrosis: Potential Role of Nuclear Factor Erythroid 2-Related Factor 2 in Cytoprotection.

Significance: Osteonecrosis (ON) is characterized by bone tissue death due to disturbance of the nutrient artery. The detailed process leading to the necrotic changes has not been fully elucidated. Clinically, high-dose corticosteroid therapy is one of the main culprits behind osteonecrosis of the femoral head (ONFH). Recent Advances: Numerous studies have proposed that such ischemia concerns various intravascular mechanisms. Of all reported risk factors, the involvement of oxidative stress in the irreversible damage suffered by bone-related and vascular endothelial cells during ischemia simply cannot be overlooked. Several articles also have sought to elucidate oxidative stress in relation to ON using animal models or in vitro cell cultures. Critical Issues: However, as far as we know, antioxidant monotherapy has still not succeeded in preventing ONFH in humans. To provide this desideratum, we herein summarize the current knowledge about the influence of oxidative stress on ON, together with data about the preventive effects of administering antioxidants in corticosteroid-induced ON animal models. Moreover, oxidative stress is counteracted by nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent cytoprotective network through regulating antioxidant expressions. Therefore, we also describe Nrf2 regulation and highlight its role in the pathology of ON. Future Directions: This is a review of all available literature to date aimed at developing a deeper understanding of the pathological mechanism behind ON from the perspective of oxidative stress. It may be hoped that this synthesis will spark the development of a prophylactic strategy to benefit corticosteroid-associated ONFH patients. Antioxid. Redox Signal. 35, 357-376.

Effects of preoperative low-intensity training with slow movement on early quadriceps weakness after total knee arthroplasty in patients with knee osteoarthritis: a retrospective propensity score-matched study.

BACKGROUND: Severe and early quadriceps weakness (QW) after total knee arthroplasty (TKA), which is caused by acute inflammation resulting from surgical trauma and tourniquet-induced ischemia-reperfusion (IR) injury, can be especially problematic. We focused on tourniquet-induced IR injury, because it has been shown to be preventable through ischemic and exercise preconditioning. Low-intensity resistance exercise with slow movement and tonic force generation (LST) share some similarities with ischemic and exercise preconditioning. The present study primarily aimed to clarify the efficacy of preoperative LST program as prehabilitation for early QW among patients with TKA using propensity score matching analysis. METHODS: This single-center retrospective observational study used data from patients with knee osteoarthritis (n = 277) who were scheduled to undergo unilateral TKA between August 2015 and January 2017. Those with missing outcome data due to their inability to perform tests were excluded. The LST group included participants who performed LST and aerobic exercise (LST session) more than seven times for three months prior to surgery. The control group included participants who performed less than eight LST sessions, a general and light exercise or had no exercise for three months prior to surgery. Knee circumference, thigh volume, knee pain during quadriceps strength test (QST) and timed up and go test (TUG), quadriceps strength, and TUG were measured before and 4 days after surgery. Knee swelling, thigh swelling, Δknee pain, QW, and ΔTUG were determined by comparing pre- and postoperative measurements. RESULTS: Propensity score matching generated 41 matched pairs who had nearly balanced characteristics. The LST group had a significantly lower knee and thigh swelling, QW, and ΔTUG compared to the control group (all, p < 0.05). No significant differences in Δknee pain during the QST and TUG were observed between both groups (both, p > 0.05). CONCLUSIONS: The present study demonstrated the beneficial effects of preoperative LST program on knee swelling, thigh swelling, QW, and walking disability immediately after TKA.

Temperature limits to deep subseafloor life in the Nankai Trough subduction zone.

Microorganisms in marine subsurface sediments substantially contribute to global biomass. Sediments warmer than 40°C account for roughly half the marine sediment volume, but the processes mediated by microbial populations in these hard-to-access environments are poorly understood. We investigated microbial life in up to 1.2-kilometer-deep and up to 120°C hot sediments in the Nankai Trough subduction zone. Above 45°C, concentrations of vegetative cells drop two orders of magnitude and endospores become more than 6000 times more abundant than vegetative cells. Methane is biologically produced and oxidized until sediments reach 80° to 85°C. In 100° to 120°C sediments, isotopic evidence and increased cell concentrations demonstrate the activity of acetate-degrading hyperthermophiles. Above 45°C, populated zones alternate with zones up to 192 meters thick where microbes were undetectable.

Distribution of Femoral Head Subchondral Fracture Site Relates to Contact Pressures, Age, and Acetabular Structure.

OBJECTIVE. Nontraumatic subchondral fracture of the femoral head (FH) is often seen in elderly patients with osteoporosis and acetabular dysplasia. Although this injury can also occur in young people, even those without osteoporosis, it remains unclear who is at risk. We examined the acetabular structure and sites of subchondral fracture of the FH in young patients compared with those in middle-aged and older patients. MATERIALS AND METHODS. Forty-eight hips with nontraumatic subchondral fracture of the FH were divided into two groups according to patient age: young (< 40 years) and middle-aged and older (≥ 40 years). Dysplasia and retroversion were defined as a lateral center-edge angle of < 20° and crossover sign on anterosuperior radiographs, respectively. Locations and extents of fracture were evaluated by measuring the edge location of low-signal-intensity bands on coronal T1-weighted MR images. Stress distribution on subchondral bone in young patients was evaluated in contralateral unaffected hips with the same acetabular structure using finite element modeling based on CT. RESULTS. Twelve hips were in young patients and 36 were in middle-aged and older patients. Hips in young patients showed retroversion in 41.7%, whereas those in middle-aged and older patients had dysplasia in 38.9%. Young patients had larger mediolateral fractures; fractures in middle-aged and older patients were laterally located. Anterosuperior fractures were seen in both groups. Contact stress in patients with retroversion was mainly distributed on the mediolateral and superior sides but was concentrated laterally and superiorly in one patient with dysplasia. CONCLUSION. Mediolateral and anterosuperior fractures and stress distribution by retroversion were commonly observed in young patients, suggesting partial involvement of retroversion in the mechanism of injury of nontraumatic subchondral fractures of the FH in young patients.