Improvement of Panax notoginseng saponin accumulation triggered by methyl jasmonate under arbuscular mycorrhizal fungi.

Panax notoginseng is a highly valued perennial medicinal herb plant in Yunnan Province, China, and the taproots are the main medicinal parts that are rich in active substances of P. notoginseng saponins. The main purpose of this study is to uncover the physiological and molecular mechanism of Panax notoginseng saponin accumulation triggered by methyl jasmonate (MeJA) under arbuscular mycorrhizal fungi (AMF) by determining physiological indices, high-throughput sequencing and correlation analysis. Physiological results showed that the biomass and saponin contents of P. notoginseng, the concentrations of jasmonic acids (JAs) and the key enzyme activities involved in notoginsenoside biosynthesis significantly increased under AMF or MeJA, but the interactive treatment of AMF and MeJA weakened the effect of AMF, suggesting that a high concentration of endogenous JA have inhibitory effect. Transcriptome sequencing results indicated that differential expressed genes (DEGs) involved in notoginsenoside and JA biosynthesis were significantly enriched in response to AMF induction, e.g., upregulated genes of diphosphocytidyl-2-C-methyl-d-erythritol kinases (ISPEs), cytochrome P450 monooxygenases (CYP450s)_and glycosyltransferases (GTs), while treatments AMF-MeJA and salicylhydroxamic acid (SHAM) decreased the abundance of these DEGs. Interestingly, a high correlation presented between any two of saponin contents, key enzyme activities and expression levels of DEGs. Taken together, the inoculation of AMF can improve the growth and saponin accumulation of P. notoginseng by strengthening the activities of key enzymes and the expression levels of encoding genes, in which the JA regulatory pathway is a key link. This study provides references for implementing ecological planting of P. notoginseng, improving saponin accumulation and illustrating the biosynthesis mechanism.

Temperature-Dependent Frictional Behavior of MoS2 in Humid Environments: Insights from Water Molecule Adsorption and DFT Analyses.

This study investigates the temperature-dependent frictional behavior of MoS2 in humid environments within the context of a long-standing debate over increased friction due to oxidation processes or molecular adsorption. By combining sliding friction experiments and density functional theory (DFT)-based first-principles simulations, it aims to clarify the role of water molecule adsorption in influencing frictional properties of MoS2, addressing the challenge of identifying interfacial bonding behavior responsible for friction in such conditions. Sliding experiments revealed that magnetron-sputtered MoS2 exhibits a reduction in the coefficient of friction (COF) with an increase in temperature from 25 to 100 °C under 20 and 40% relative humidity. This change in the COF obeys the Arrhenius law, presenting an energy barrier of 0.165 eV, indicative of the temperature-dependent nature of these frictional changes and suggests a consistent frictional mechanism. DFT simulations showed that H2O molecules are adsorbed at MoS2 vacancy defects with adsorption energies ranging from -0.56 to -0.17 eV, which align with the experimentally determined energy barrier. Adsorptive interactions, particularly the formation of stable H···S interfacial hydrogen bonds at defect sites, increase the interlayer adhesion and impede layer shearing. TEM analysis confirms that although MoS2 layers align parallel to the sliding direction in humid conditions, the COF remains at 0.12, as opposed to approximately 0.02 in dry air. This demonstrates that parallel layer alignment does not notably decrease the COF, underscoring humidity's significant role in MoS2's COF values, a result also supported by the Arrhenius analysis. The reversibility of the physisorption process, demonstrated by the recovery of the COF in high-temperature humid environments, suggests its dynamic nature. This study yields fundamental insights into MoS2 interfaces for environments with variable humidity and temperature, crucial for demanding tribological applications.

Experimental Evaluation of Anticorrosion of a Standard 20# Gathering Pipeline by Injecting Oxygen-Reduced Air into Simulated In-Service Wells.

Oxygen-reduced air flooding (ORAF) can effectively improve oil recovery in low-permeability reservoirs, but oxygen corrosion and CO2 corrosion in downstream gathering pipelines are inevitable due to the existence of oxygen, which limits the popularization and application of ORAF. In this paper, research on the corrosion inhibitor is carried out for the gathering pipeline of an oilfield with ORAF in China. Under the conditions of a simulated onsite gathering pipeline, 6 kinds of anti-CO2 corrosion inhibitors and 6 kinds of antioxygen corrosion inhibitors were selected to evaluate and screen the effects of 20# steel by the dynamic weight loss method. Two antioxygen corrosion inhibitors KY-12 and KY-17 and one anti-CO2 corrosion inhibitor A were selected for the experiment. The corrosion inhibition rates of the three inhibitors reached 83.67, 91.49, and 78.44%, respectively, at a temperature of 40 °C and an inhibitor concentration of 1000 mg/L. Through the experimental evaluation of three primary corrosion inhibitors at different temperatures (25, 40, and 55 °C) and different concentrations (400, 500, 800, 1000, and 2000 mg/L), the KY-17 corrosion inhibitor with the best stability at different temperatures was selected, and the corrosion inhibition effect was the best at different concentrations, with the highest slow release rate reaching 92.7%. This conclusion has a good reference significance for the selection and dosage of corrosion inhibitors for downstream gathering pipelines of the ORAF oilfield.

[Comparison of effectiveness of lower extremity axial distractor and traction table assisted closed reduction and intramedullary nail fixation in femoral subtrochanteric fracture].

Objective: To compare the effectiveness of lower extremity axial distractor (LEAD) and traction table assisted closed reduction and intramedullary nail fixation in treatment of femoral subtrochanteric fracture. Methods: The clinical data of 117 patients with subtrochanteric fracture of femur treated by closed reduction and intramedullary nail fixation between May 2012 and May 2022 who met the selection criteria were retrospectively analyzed. According to the auxiliary reduction tools used during operation, the patients were divided into LEAD group (62 cases with LEAD reduction) and traction table group (55 cases with traction table reduction). There was no significant difference in baseline data, such as gender, age, injured side, cause of injury, fracture Seinsheimer classification, time from injury to operation, and preoperative visual analogue scale (VAS) score, between the two groups ( P>0.05). Total incision length, operation time, intraoperative blood loss, fluoroscopy frequency, closed reduction rate, fracture reduction quality, fracture healing time, weight-bearing activity time, and incidence of complications, as well as hip flexion and extension range of motion (ROM), Harris score, and VAS score at 1 month and 6 months after operation and last follow-up were recorded and compared between the two groups. Results: There were 14 cases in the LEAD group from closed reduction to limited open reduction, and 43 cases in the traction table group. The incisions in the LEAD group healed by first intention, and no complication such as nerve and vascular injury occurred during operation. In the traction table group, 3 cases had perineal crush injury, which recovered spontaneously in 1 week. The total incision length, operation time, intraoperative blood loss, fluoroscopy frequency, and closed reduction rate in the LEAD group were significantly better than those in the traction table group ( P<0.05). There was no significant difference in the quality of fracture reduction between the two groups ( P>0.05). Patients in both groups were followed up 12-44 months, with an average of 15.8 months. In the LEAD group, 1 patient had delayed fracture union at 6 months after operation, 1 patient had nonunion at 3 years after operation, and 1 patient had incision sinus pus flow at 10 months after operation. In the traction table group, there was 1 patient with fracture nonunion at 15 months after operation. X-ray films of the other patients in the two groups showed that the internal fixator was fixed firmly without loosening and the fractures healed. There was no significant difference in fracture healing time, weight bearing activity time, incidence of complications, and postoperative hip flexion and extension ROM, Harris score, and VAS score at different time points between the two groups ( P>0.05). Conclusion: For femoral subtrochanteric fracture treated by close reduction and intramedullary nail fixation, compared with traction table, LEAD assisted fracture reduction can significantly shorten the operation time, reduce intraoperative blood loss and fluoroscopy frequency, reduce incision length, effectively improve the success rate of closed reduction, and avoid complications related to traction table reduction. It provides a new method for good reduction of femoral subtrochanteric fracture.

Targeted Protein Fate Modulating Functional Microunits Promotes Intervertebral Fusion.

Stable regulation of protein fate is a prerequisite for successful bone tissue repair. As a ubiquitin-specific protease (USP), USP26 can stabilize the protein fate of ß-catenin to promote the osteogenic activity of mesenchymal cells (BMSCs) and significantly increased bone regeneration in bone defects in aged mice. However, direct transfection of Usp26 in vivo is inefficient. Therefore, improving the efficient expression of USP26 in target cells is the key to promoting bone tissue repair. Herein, 3D printing combined with microfluidic technology is applied to construct a functional microunit (protein fate regulating functional microunit, denoted as PFFM), which includes GelMA microspheres loaded with BMSCs overexpressing Usp26 and seeded into PCL 3D printing scaffolds. The PFFM provides a microenvironment for BMSCs, significantly promotes adhesion, and ensures cell activity and Usp26 supplementation that stabilizes ß-catenin protein significantly facilitates BMSCs to express osteogenic phenotypes. In vivo experiments have shown that PFFM effectively accelerates intervertebral bone fusion. Therefore, PFFM can provide new ideas and alternatives for using USP26 for intervertebral fusion and other hard-to-repair bone defect diseases and is expected to provide clinical translational potential in future treatments.

Study on the Corrosion Mechanism of N80 Steel in Simulated Oxygen-Reduced Air Drive Production Wellbores.

In order to investigate the corrosion behavior of N80 steel in production wellbores of oxygen-reduced air drive, the main corrosion control factors are analyzed based on gray relational analysis. Taking reservoir simulation results as indoor simulation parameters, the corrosion behavior in different production periods is studied by the dynamic weight loss method combined with metallographic microscopy, XRD, 3D morphology, and other related characterizations. The results show that oxygen content is most sensitive to the corrosion of production wellbores. The corrosion rate increases significantly under oxygen-containing conditions, and the corrosion rate at an oxygen content of 3% (0.3 MPa) is about 5 times higher than that without oxygen. At the initial stage of oil displacement, the corrosion is CO2-dominated localized corrosion, and the corrosion products are mainly compact FeCO3. With the prolongation of gas injection time, the wellbore is in a CO2/O2 balanced environment, the corrosion changes into a combined action of the two, and the corrosion products are FeCO3 and loose porous Fe2O3. After continuous gas injection for 3 years, the production wellbore is in a high O2 and low CO2 environment, the dense FeCO3 is destroyed, the corrosion pit develops horizontally, and the corrosion changes to O2-dominated comprehensive corrosion.

Comprehensive Analysis of 34 Edible Flowers by the Determination of Nutritional Composition and Antioxidant Capacity Planted in Yunnan Province China.

The main purpose of this study was to reveal the nutritional value and antioxidant activity of 34 edible flowers that grew in Yunnan Province, China, through a comprehensive assessment of their nutritional composition and antioxidant indices. The results showed that sample A3 of Asteraceae flowers had the highest total flavonoid content, with a value of 8.53%, and the maximum contents of vitamin C and reducing sugars were from Rosaceae sample R1 and Gentianaceae sample G3, with values of 143.80 mg/100 g and 7.82%, respectively. Samples R2 and R3 of Rosaceae were the top two flowers in terms of comprehensive nutritional quality. In addition, the antioxidant capacity of Rosaceae samples was evidently better than that of three others, in which Sample R1 had the maximum values in hydroxyl radical (·OH) scavenging and superoxide anion radical (·O2-) scavenging rates, and samples R2 and R3 showed a high total antioxidant capacity and 2,2-diphenyl-1-pyridylhydrazine (DPPH) scavenging rate, respectively. Taken together, there were significant differences in the nutrient contents and antioxidant properties of these 34 flowers, and the comprehensive quality of Rosaceae samples was generally better than the other three families. This study provides references for 34 edible flowers to be used as dietary supplements and important sources of natural antioxidants.

An Integrated Quantitative Risk Assessment Method for Underground Engineering Fires.

Fires are one of the main disasters in underground engineering. In order to comprehensively describe and evaluate the risk of underground engineering fires, this study proposes a UEF risk assessment method based on EPB-FBN. Firstly, based on the EPB model, the static and dynamic information of the fire, such as the cause, occurrence, hazard, product, consequence, and emergency rescue, was analyzed. An EPB model of underground engineering fires was established, and the EPB model was transformed into a BN structure through the conversion rules. Secondly, a fuzzy number was used to describe the state of UEF variable nodes, and a fuzzy conditional probability table was established to describe the uncertain logical relationship between UEF nodes. In order to make full use of the expert knowledge and empirical data, the probability was divided into intervals, and a triangulated fuzzy number was used to represent the linguistic variables judged by experts. The α-weighted valuation method was used for de-fuzzification, and the exact conditional probability table parameters were obtained. Through fuzzy Bayesian inference, the key risk factors can be identified, the sensitivity value of key factors can be calculated, and the maximum risk chain can be found in the case of known evidence. Finally, the method was applied to the deductive analysis of three scenarios. The results show that the model can provide realistic analysis ideas for fire safety evaluation and emergency management of underground engineering. The proposed EPB risk assessment model provides a new perspective for the analysis of UEF accidents and contributes to the ongoing development of UEF research.

Intervertebral Disc Degeneration and Low Back Pain Depends on Duration and Magnitude of Axial Compression.

Purpose: The pathological role of axial stress in intervertebral disc degeneration (IDD) is controversial, and there was no quantified study until now. Here, we tried to clarify the correlation between IDD or low back pain (LBP) and axial stress at different duration and magnitude in vitro and in vivo. Method: In vitro, the gene expression of aggrecan, matrix metalloproteinase-3 (MMP3), calcitonin gene-related peptide (CGRP), and substance P (SP) was measured when nucleus pulposus cells (NPCs) were compressed under gradual severity. In vivo, a measurable Ilizarov-type compression apparatus was established for single coccygeal (Co) intervertebral disc (IVD) compression of Co7-8 in mouse. Gradient stress was placed at 0.4 Mpa (mild), 0.8 Mpa (moderate), and 1.2 Mpa (severe) for three days to investigate the effect of the magnitude of axial stress. Additionally, mild compression with 3, 7, and 14 days was used to determine the effect of the duration of axial stress. Subsequently, we evaluated the severity of IDD and LBP by radiological X-ray film; histological examination with H&E staining; immunohistochemical analysis with collagen II, aggrecan, and CGRP staining; and western blot analysis with collagen II, aggrecan, MMP-3, and interleukin-1ß (IL-1ß). Results: When NPCs suffered gradual increased mechanical stress, the cells exhibited gradual downregulated expression of extracellular matrix (ECM)-related gene of aggrecan, upregulated expression of IDD-related gene of MMP3, and LBP-related gene of CGRP and SP. In the meantime, with different magnitudes of axial stress, the IVD showed progressively severe IDD and LBP, with gradual narrowing intervertebral height, destruction of IVD anatomy, decreased ECM, and increased catabolic factors and proalgesic peptides. Conclusion: Axial compression is one of the critical pathological factors to cause IDD and LBP, and there was a strong positive correlation depended on the duration and magnitude of compression.

Increased Expression of Integrin Alpha 6 in Nucleus Pulposus Cells in Response to High Oxygen Tension Protects against Intervertebral Disc Degeneration.

The destruction of the low oxygen microenvironment in nucleus pulposus (NP) cells played a critical role in the pathogenesis of intervertebral disc degeneration (IVDD). The purpose of this study was to determine the potential role of integrin alpha 6 (ITG α6) in NP cells in response to high oxygen tension (HOT) in IVDD. Immunofluorescence staining and western blot analysis showed that the levels of ITG α6 expression were increased in the NP tissue from IVDD patients and the IVDD rat model with mild degeneration, which were reduced as the degree of degeneration increases in severity. In NP cells, the treatment of HOT resulted in upregulation of ITG α6 expression, which could be alleviated by blocking the PI3K/AKT signaling pathway. Further studies found that ITG α6 could protect NP cells against HOT-induced apoptosis and oxidative stress and protect NP cells from HOT-inhibited ECM protein synthesis. Upregulation of ITG α6 expression by HOT contributed to maintaining NP tissue homeostasis through the interaction with hypoxia-inducible factor-1α (HIF-1α). Furthermore, silencing of ITG α6 in vivo could obviously accelerate puncture-induced IVDD. Taken together, these results revealed that the increase of ITG α6 expression by HOT in NP cells might be a protective factor in IVD degeneration as well as restore NP cell function.

Reactive Oxygen Species Mediate Low Back Pain by Upregulating Substance P in Intervertebral Disc Degeneration.

Reactive oxygen species (ROS) are thought to have a strong correlation with a number of intervertebral disc (IVD) diseases. Here, we aimed to determine whether ROS represent an etiology of low back pain (LBP) during IVD degeneration. Thirty degenerated intervertebral disc samples were obtained from patients, and ROS levels were quantified using dihydroethidium (DHE) staining. The results suggested a significant correlation between the ROS level and the severity of LBP. Subsequently, a puncture-induced LBP model was established in rats, and ROS levels significantly increased compared with those in the sham surgery group, accompanied with severe puncture-induced IVD degeneration. In addition, when ROS levels were increased by H2O2 administration or decreased by NAC treatment, the rats showed increased or decreased LBP, respectively. Based on this evidence, we further determined that stimulation with H2O2 in nucleus pulposus cells (NPCs) in vivo or in vitro resulted in upregulation of substance P (SP), a peptide thought to be involved in the synaptic transmission of pain, and that the severity of LBP decreased when SP levels were increased by exogenous SP administration or neutralized via aprepitant treatment in the IVDs of rats. In conclusion, ROS are primary inducers of LBP based on clinical and animal data, and the mechanism involves ROS stimulation of NPCs to secrete SP, which is a critical neurotransmitter peptide, to promote LBP in IVDs. Therefore, reducing the level of ROS with specific drugs and inhibiting SP may be alternative methods to treat LBP in the clinic.

TRIM21 drives intervertebral disc degeneration induced by oxidative stress via mediating HIF-1α degradation.

The onset and progression of intervertebral disc degeneration (IVDD) is strictly associated with oxidative stress. TRIM21 (Tripartite motif-containing protein 21), a ubiquitin E3 ligase, has been shown to play an essential role in liver redox homeostasis; however, whether TRIM21 is involved in IVDD, especially in oxidative stress-induced IVDD, is unknown. Here, we reported that TRIM21 was upregulated in nucleus pulposus (NPs) with increasing severity of IVDD, and that oxidative stress was a stimulator of TRIM21 expression. Furthermore, we found that TRIM21 deficiency significantly protected NP cells from degeneration induced by oxidative stress as well as ameliorated disc degeneration in aged mice. Mechanistically, TRIM21 facilitated NP cells degeneration induced by oxidative stress via HIF-1α. TRIM21 could physically interact with HIF-1α and facilitated its degradation via its ubiquitylating activity. Taken together, these findings revealed that TRIM21 drived IVDD induced by oxidative stress by increasing HIF-1α degradation. These findings implicates the potential of TRIM21 as a therapeutic target in IVDD, especially in oxidative stress-induced IVDD.

A novel in vivo mouse intervertebral disc degeneration model induced by compressive suture.

Intervertebral disc degeneration (IDD) is the root cause of many musculoskeletal disorders of the spine. However, the etiology of IDD is complex and still not well understood. Animal models of IDD would be useful in deciphering the underlying mechanisms. But the existing animal models have their limitations. Therefore, to establish a novel mouse model that can simulate the human IDD process in vivo, we proposed to carefully circumcise the 2 mm-wide tail skin and then compressively sutured the defect with a simple end-to-end suture to exert excessive pressure on the disc. After 1-week, 2-week, and 4-week compression, the mice were sacrificed and the intervertebral discs were harvested for tissue analysis. The radiological, morphological, and molecular modifications of intervertebral discs were measured to characterize this model. Radiologically, the water content of the intervertebral disc decreased significantly after 2-week compression. Morphologically, the nucleus pulposus showed a decrease in volume and the number of notochordal cells. The compressive suture also broke the balance between anabolic and catabolic enzymes in nucleus pulposus, which led to the remodeling of the extracellular matrix in nucleus pulposus as the content of aggrecan and collagen II decreased. The compressive suture could induce intervertebral discs degeneration in a more reasonable way, which was solely influenced by mechanical loading, as the mice caudal vertebrae still moved freely after the operation. This kind of animal model could be adapted as a reliable in vivo mouse IDD model for the research regarding the etiology and treatments of IDD.

A modified thermal radiation model with multiple factors for investigating temperature rise around pool fire.

Hazardous chemical tanks are widely distributed in China, while tank fires occur frequently. Thermal radiation of pool fire plays a critical role in multi-points combustion and accident expansion, resulting in severe thermal damage to the surrounding targets. There are kinds of classical models used to predict the temperature rise of the target, but inaccuracies still exist in the application. In this work, we had conducted a series of pool fire tests in a full-size tunnel and open space for three petroleum products, and observed the temperature variations around the pool fire. A basic thermal radiation model with multiple factors was established first to predict the surrounding temperature rise, but its accuracy was still low. Subsequently, a correction approach of view factor and other aspects was proposed to accord with the experimental data, and the basic prediction model of temperature rise was then modified accordingly. Calculative results of the modified model agreed well with the experimental measuring temperatures, which verified the accuracy and reliability of the modified model. This modified model has a functional applicability to estimate the thermal radiation of pool fire on the surrounding objects.

The effects of tranylcypromine on osteoclastogenesis in vitro and in vivo.

Identification of anti-osteoclastogenic agents is important for the treatment of bone loss diseases that feature excessive osteoclast (OC) activity and bone resorption. Tranylcypromine (TCP), an irreversible inhibitor of monoamine oxidase (MAO), has been used as an antidepressant and anxiolytic agent in the clinical treatment of mood and anxiety disorders. TCP has been discovered to exert anabolic effect on osteoblasts, and MAO-A has also been verified as an important mediator in prostate cancer cells to accelerate osteoclastogenesis. In current study, we were focused on TCP and MAO-A effects on osteoclastogenesis. As illustrated by tartrate-resistant acid phosphatase staining, TCP was capable of inhibiting osteoclastogenesis induced by receptor activators of the NF-κB ligand (RANKL) in bone marrow-derived macrophage cells without any cytotoxicity. It was also shown to effectively suppress bone resorption of OCs. The subsequent study revealed that TCP inhibited osteoclastogenesis-related genes in a time-dependent manner through protein kinase B (AKT)-mediated mechanism followed by the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)-c-fos pathway. And TCP could overcome the osteoclastogenic effects of AKT activator SC79. In addition, our results indicated that the expression and catalytic activity of MAO-A were up-regulated by RANKL stimulation and down-regulated by TCP in vitro and in vivo. Furthermore, the effects of MAO-A knockdown on OC differentiation indicated that MAO-A played an important role in osteoclastogenesis in vitro and might contribute to the inhibitory effects of TCP. And AKT, NFATc1, and c-fos were involved in the MAO-A pathway. Notably, our in vivo study reflected that TCPs were capable of restoring the bone loss in LPS-induced calvaria osteolysis and estrogen deficiency-induced osteoporosis models. Thus, our current work provided a potential option for the treatment of bone loss diseases and highlighted the important role of MAO-A in osteoclastogenesis as well.-Liu, Z., Yang, K., Yan, X., Wang, T., Jiang, T., Zhou, Q., Qi, J., Qian, N., Zhou, H., Chen, B., Huang, P., Guo, L., Zhang, X., Xu, X., Jiang, M., Deng, L. The effects of tranylcypromine on osteoclastogenesis in vitro and in vivo.

CD24 identifies nucleus pulposus progenitors/notochordal cells for disc regeneration.

BACKGROUND: Cell-based therapy by transplantation of nucleus pulposus (NP) progenitor/notochordal cells has been proposed as a promising way to halt and reverse the progression of disc degeneration. Although some studies have provided a broad panel of potential markers associated with the phenotype of notochordal cells, suitability of these markers for isolation of notochordal cells for the treatment of disc degeneration is unclear. RESULTS: Here, we found that the number of CD24-positive NP cells significantly decreased with increasing severity of disc degeneration. In addition, CD24-positive NP cells were shown to maintain their multipotent differentiation and self-renewal potential in vitro and to abundantly express brachyury, SHH, and GLUT-1, suggesting that CD24-positive NP cells are the progenitor/notochordal cells in the NP. Moreover, our in vivo experiments revealed that transplantation of CD24-positive NP cells enables the recovery of degenerate discs, as evidenced by increased disc height, restored magnetic resonance imaging T2-weighted signal intensity, and NP structure. In terms of the mechanism, HIF-1α-Notch1 pathway activation was essential for the maintenance of CD24-positive NP cells. CONCLUSION: Our studies identify that CD24-positive NP cells are the resident progenitor/notochordal cells in disc regeneration and elucidate a crucial role of HIF-1α-Notch1 pathway in the phenotypic maintenance of CD24-positive NP cells.

Hypoxia-inducible factor (HIF)-1alpha knockout accelerates intervertebral disc degeneration in mice.

INTRODUCTION: The abnormality of nucleus pulposus (NP) plays a critical role in intervertebral disc (IVD) degeneration, in which NP cells show apoptosis and fibrosis, leading to the ability of the disc to transfer and distribute loads between the vertebrae is decreased. Considering that hypoxia inducible factor-1α (HIF-1α) is abundantly expressed in NP and that it mediates cell proliferation, migration and apoptosis in various cell types, we hypothesized that NP-HIF-1α plays an important role in NP and evaluate whether NP-HIF-1α is involved in IVD degeneration. MATERIAL AND METHODS: Sonic Hedgehog-Cre+/- mice were crossed with HIF-1αflox/flox mice to generate NP specific HIF-1α-deficient (HIF-1α-/-) mice. Magnetic resonance imaging (MRI) study was used to evaluate NP dehydration and X-ray study was used to acquire the changes of disc height. Histological changese, content of glycoproteins and the in situ expression of aggrecan were evaluated by hematoxylin & eosin (H&E) staining, safranin-O/fast green staining and immunohistochemistry assay, respectively. Western bloting was used to detect the change of extracellular matrix in IVD. RESULTS: Firstly, the results of in situ hybridization confirmed that HIF-1α in NP was successfully knocked out in HIF-1α-/- mice. Next, for HIF-1α deficiency mice, imaging study shows IVD was narrowed in X-ray and signal intensity of NP was decreased in MR T2-weight imaging. Accordingly, the size and cell number of NP and proteoglycan content was decreased in NP-HIF-1α-/- mice. Finally, Western bloting shows that protein level of collagen II and aggrecan, two main matrix in disc, were both decreased in NP-HIF-1α-/- mice. CONCLUSIONS: The present study demonstrates that HIF-1α is essential for NP development and homeostasis and the deficiency of NP-HIF-1α leads to IVD degeneration in mice.

Hypoxia-inducible factor-lα mediates aggrecan and collagen Π expression via NOTCH1 signaling in nucleus pulposus cells during intervertebral disc degeneration.

Although hypoxia-inducible factor-lα (HIF-lα) has been reported to have an important role in the metabolism and synthesis of the extracellular matrix (ECM) of nucleus pulposus cells (NPCs), the underlying mechanism has not been fully clarified. Here, we show for the first time that NOTCH1 expression is decreased in NPs isolated from degenerated human intervertebral discs (IVDs), as well as in the NPs of NP-specific HIF-1α-/- mice. Our study reveals that overexpression of HIF-1α leads to increased expression of NOTCH1, the NOTCH1 ligand JAGGED1, and its target gene hairy and enhancer of split-1 (HES1), while also upregulating collagen Π and aggrecan expression in human NPCs. Importantly, these changes in expression are significantly suppressed by the NOTCH1 inhibitor DAPT. In parallel with changes in collagen Π and aggrecan expression, inhibition of the HIF-1α-NOTCH1 pathway altered ECM turnover by suppressing expression of the matrix metalloproteinases MMP1 and MMP13, while increasing the expression of tissue inhibitor of metalloproteinase-1 (TIMP1). Lastly, activation of NOTCH1 via JAGGED1 in human NPCs isolated from degenerated IVDs restored collagen Π and aggrecan expression. Therefore, our study shows that HIF-1α regulates collagen Π and aggrecan expression through NOTCH1 signaling and implicate NOTCH1 as a potential therapeutic target in disc degeneration.

Relationship between annular tear and presence of Propionibacterium acnes in lumbar intervertebral disc.

PURPOSE: Propionibacterium acnes (P. acnes) in the intervertebral disc may result in low back pain. The purpose of this study was to determine how P. acnes accesses the disc. METHODS: Patients with low back pain and/or sciatica were examined using X-ray and MRI before surgery. The intervertebral disc space height was measured on X-ray image. Disc and muscle samples were obtained from 46 patients undergoing discectomy at the lumbar spine. The tear of annulus was inspected before discectomy. In the disc and muscle tissue cultures, 16S rDNA gene specific for P. acnes was examined using PCR. RESULTS: The discs from 11 (23.9 %) patients were identified as 16S rDNA positive, in which two patients also had 16S rDNA in their muscles. 16S rDNA gene was significantly more likely to appear in the discs with annular tear than those without tear (P < 0.05). The disc space height was significantly decreased when the disc contained P. acnes. CONCLUSION: P. acnes is significantly more likely to be present in herniated discs with an annular tear than in herniated discs without such a tear. Since in the vast majority of these cases, no P. acnes was found in control muscle samples, a true infection with P. acnes is far more likely than a contamination.