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Study Design: Preclinical experimental study. Objective: To develop an intraoperative ultrasound-assisted imaging device, which could be placed at the surgical site through an endoscopic working channel and which could help surgeons recognition of different tissue types during endoscopic spinal surgery (ESS). Summary of Background Data: ESS remains a challenging task for spinal surgeons. Great prof iciency and experience are needed to perform procedures such as intervertebral discectomy and neural decompression within a narrow channel. The limited surgical view poses a risk of damaging important structures, such as nerve roots. Methods: We constructed a spinal endoscopic ultrasound system, using a 4-mm custom ultrasound probe, which can be easily inserted through the ESS working channel, allowing up to 10 mm depth detection. This system was applied to ovine lumbar spine samples to obtain ultrasound images. Subsequently, we proposed a 2-stage classification algorithm, based on a pretrained DenseNet architecture for automated tissue recognition. The recognition algorithm was evaluated for accuracy and consistency. Results: The probe can be easily used in the ESS working channel and produces clear and characteristic ultrasound images. We collected 367 images for training and testing of the recognition algorithm, including images of the spinal cord, nucleus pulposus, adipose tissue, bone, annulus fibrosis, and nerve roots. The algorithm achieved over 90% accuracy in recognizing all types of tissues with a Kappa value of 0.875. The recognition times were under 0.1 s using the current configuration. Conclusion: Our system was able to be used in existing ESS working channels and identify at-risk spinal structures in vitro. The trained algorithms could identify 6 intraspinal tissue types accurately and quickly. The concept and innovative application of intraoperative ultrasound in ESS may shorten the learning curve of ESS and improve surgical efficiency and safety. [ABSTRACT FROM AUTHOR]

Bone marrow mesenchymal stem cell (BMSC)-derived exosomes possess therapeutic potential against degenerative diseases. This study aimed to investigate the effects of BMSC-derived exosomes on intervertebral disc degeneration (IVDD) and explore the underlying molecular mechanisms. Through transcriptome sequencing and histological analysis, we observed a significant increase in HIF-1α expression in degenerative nucleus pulposus (NP) tissues. The addition of HIF-1α resulted in elevated expression of inflammatory factors IL-1β and IL-6, higher levels of matrix-degrading enzyme MMP13, and lower expression of aggrecan in NP cells. Co-culturing with BMSCs diminished the expression of HIF-1α, MMP13, IL-1β, and IL-6 in degenerative NP cells induced by overload pressure. miRNA chip analysis and PCR validation revealed that miR-145a-5p was the primary miRNA carried by BMSC-derived exosomes. Overexpression of miR-145a-5p was effective in minimizing the expression of HIF-1α, MMP13, IL-1β, and IL-6 in degenerative NP cells. Luciferase reporter assays confirmed USP31 as the target gene of miR-145a-5p, and the regulation of NP cells by BMSC-derived exosomes via miR-145a-5p was dependent on USP31. In conclusion, BMSC-derived exosomes alleviated IVDD through the miR-145a-5p/USP31/HIF-1α signaling pathway, providing valuable insights into the treatment of IVDD. [ABSTRACT FROM AUTHOR]

Low back pain (LBP) is a significant global health issue, contributing to disability and socioeconomic burdens worldwide. The degeneration of the human intervertebral disc (IVD) is a critical factor in the pathogenesis of LBP. Recent studies have emphasized the significance of a specific set of genes and extracellular matrix (ECM) in IVD health. In particular, Noggin has emerged as a critical gene due to its high expression levels in healthy nucleus pulposus cells (NPCs) observed in our previous research. In this study, it was hypothesized that decreased Noggin expression in NPCs is associated with IVD degeneration and contributes to LBP development. A lentivirus-mediated RNAi was applied to knock down Noggin expression in primary NPCs from six human donors. The NPCs after transduction were evaluated through cell viability analysis, XTT assay, and cell apoptosis analyses. After two weeks, a colony formation assay was used to examine the anchor-independent growth ability of transduced cells. At the transcript level, anabolic and catabolic markers were quantified using RT-qPCR. The results demonstrated that lentivirus-mediated downregulation of Noggin significantly inhibited cell proliferation, reduced cell viability, and suppressed colony formation, while inducing apoptosis in human NPCs in vitro. Notably, it disrupted cellular anabolic processes and promoted catabolic activity in human NPCs post-transduction. Our findings indicated that the degeneration of human IVD is possibly related to decreased Noggin expression in NPCs. This research provides valuable insights into the role of Noggin in IVD homeostasis and its implications in LBP treatment. [ABSTRACT FROM AUTHOR]

Intervertebral disk degeneration (IVDD) may lead to an increase in extracellular matrix (ECM) stiffness, potentially contributing to the progression of the disease. Melatonin reportedly mitigates IVDD; however, its potential to attenuate elevated matrix stiffness-induced IVDD remains unexplored. Therefore, we aimed to investigate whether melatonin can alleviate the progression of IVDD triggered by increased matrix stiffness and elucidate its underlying mechanisms. Nucleus pulposus (NP) tissues were collected from patients, and ECM stiffness, reactive oxygen species (ROS) levels, apoptosis rates, and P65 expression in these tissues with varying Pfirrmann scores were determined. In vitro experiments were conducted to investigate the effects of melatonin on various pathophysiological mechanisms within the NP cells cultured on soft substrates with differing stiffness levels. Our findings revealed a positive correlation between ECM stiffness in human NP tissue and degree of IVDD. In addition, phosphorylation of P65 exhibited a strong association with matrix stiffness. Enhanced levels of ROS and cellular apoptosis were observed within degenerated intervertebral disks. In vitro experiments demonstrated that melatonin significantly inhibited catabolism and apoptosis induced by stiff matrices, along with elevated ROS levels. Furthermore, we observed that melatonin inhibited NP cell catabolism and apoptosis by reducing the melatonin receptors mediated activation of the PI3K/AKT and nuclear factor-kappa B (NF-κB) pathways. Also, we found that the reduction of ROS by melatonin can assist in inhibiting the activation of the NF-κB pathway. The outcomes of the in vivo experiments corroborated the results of the in vitro experiments, illustrating that melatonin treatment could alleviate the compression-induced upregulation of matrix stiffness in NP and IVDD. Collectively, melatonin can potentially alleviate high matrix stiffness-induced IVDD by reducing intracellular ROS levels and inhibiting the PI3K/AKT/NF-κB pathway. NEW & NOTEWORTHY: Melatonin mitigates intervertebral disk degeneration (IVDD) induced by matrix stiffness through reactive oxygen species (ROS) reduction. Matrix stiffness is related to increased nucleus pulposus cell ROS, apoptosis, and degeneration. Melatonin inhibits PI3K/AKT/NF-κB pathways via melatonin receptors in a stiff matrix environment. In vivo, melatonin restores disk height and alleviates IVDD progression. [ABSTRACT FROM AUTHOR]

Microvascular changes are considered key factors in the process of intervertebral disk degeneration (IDD). Microvascular invasion and growth into the nucleus pulposus (NP) and cartilaginous endplates are unfavorable factors that trigger IDD. In contrast, the rich distribution of microvessels in the bony endplates and outer layers of the annulus fibrosus is an important safeguard for the nutrient supply and metabolism of the intervertebral disk (IVD). In particular, the adequate supply of microvessels in the bony endplates is the main source of the nutritional supply for the entire IVD. Microvessels can affect the progression of IDD through a variety of pathways. Many studies have explored the effects of microvessel alterations in the NP, annulus fibrosus, cartilaginous endplates, and bony endplates on the local microenvironment through inflammation, apoptosis, and senescence. Studies also elucidated the important roles of microvessel alterations in the process of IDD, as well as conducted in‐depth explorations of cytokines and biologics that can inhibit or promote the ingrowth of microvessels. Therefore, the present manuscript reviews the published literature on the effects of microvascular changes on IVD to summarize the roles of microvessels in IVD and elaborate on the mechanisms of action that promote or inhibit de novo microvessel formation in IVD. [ABSTRACT FROM AUTHOR]

Intradiscal injection is required to deliver therapeutic agents to the intervertebral disc (IVD) nucleus pulposus (NP). However, injectate leakage following needle retraction may result in decreased treatment efficacy and adverse side effects. While enzymatic digestion is a common research approach for simulating degeneration in healthy animal IVDs, contributions to the leakage phenomenon are unknown. In this study, bovine caudal discs were treated with injection into the NP of either a tris buffer control, collagenase (to primarily target collagen), or trypsin (to primarily target proteoglycans) and then injected with fluorescent saline using a through-puncture defect protocol. Pressure–volume records during injection were used to determine volume and pressure at leakage. Discs were then frozen, transected, and photographed to visualize injectate dispersion. Collagenase treatment resulted in a large increase in injectate dispersion, along with a decrease in injection pressure relative to control. Trypsin treatment resulted in a moderate increase in dispersion, with no associated effect on pressure. This study concludes that care should be taken when employing enzymatic digestion to simulate IVD degeneration, as NP tissue disruption may affect both retention and dispersion of subsequent therapeutic injections. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IDD) is one of the most common causes of chronic low back pain, which does great harm to patients' life quality. At present, the existing treatment options are mostly aimed at relieving symptoms, but the long‐term efficacy is not ideal. Tetrahedral framework nucleic acids (tFNAs) are regarded as a type of nanomaterial with excellent biosafety and prominent performance in anti‐apoptosis and anti‐inflammation. MicroRNA155 is a non‐coding RNA involved in various biological processes such as cell proliferation and apoptosis. In this study, a complex named TR155 was designed and synthesised with microRNA155 attached to the vertex of tFNAs, and its effects on the nucleus pulposus cells of intervertebral discs were evaluated both in vitro and in vivo. The experimental results showed that TR155 was able to alleviate the degeneration of intervertebral disc tissue and inhibit nucleus pulposus cell apoptosis via Bcl‐2/Bax pathway, indicating its potential to be a promising option for the treatment of IDD. [ABSTRACT FROM AUTHOR]

Purpose: Recently, there has been significant focus on extracellular matrix proteolysis due to its importance in the pathological progression of intervertebral disc degeneration (IVDD). The present study investigates the circulating levels of extracellular matrix proteins in the plasma of IVDD and determines their potential relevance as biomarkers in disc degeneration. Methods: Global proteomic analysis was performed in the plasma samples of 10 healthy volunteers (HV) and 10 diseased subjects (DS) after depletion of highly abundant proteins such as albumin and IgG. Results: We identified 144 and 135 matrix-associated proteins in plasma samples from healthy volunteers (HV) and patients with disc degeneration (DS), respectively. Among these, 49 of the matrix-associated proteins were identical to the proteins found in intervertebral disc (IVD) tissues retrieved from the in-house library. Applying stringent parameters, we selected 28 proteins, with 26 present in DS and 21 in HV. 19 proteins were found common between the groups, two of which—aggrecan (ACAN) and fibulin 1 (FBLN1) - showed statistically significant differences. Specifically, ACAN was up-regulated and FBLN1 was down-regulated in the DS-plasma. In particular, DS-plasma exhibited specific expression of collagen type 2a1 (COL2A1), native to the nucleus pulposus. Conclusion: The distinct presence of collagen type 2a1 and the elevated expression of aggrecan in IVDD plasma may serve as the basis for the development of a potential biomarker for monitoring the progression of disc degeneration. [ABSTRACT FROM AUTHOR]

Purpose: To compare the mechanical properties of human annulus fibrosus obtained by forceps versus bistoury and observe whether the measurement could be affected by forceps sampling method. Methods: In this study, the mechanical properties of the the extracellular matrix (ECM) of human annulus fibrosus, including elastic modulus and stiffness, were investigated using atomic force microscope (AFM). Tissue was obtained from patients during operation using a bistoury or nucleus pulposus forceps. Tissues obtained with the nucleus pulposus forceps were considered as the forceps group and those obtained with a bistoury were considered as the bistoury group. Results: There was no significant difference observed between the forceps and bistoury group according to histological staining. The elastic modulus of the forceps group was 0.41 ± 0.08 MPa, and that of bistoury group was 0.53 ± 0.13 MPa, and the difference between the two groups was statistically significant (p < 0.05). The stiffness of the forceps group was 0.024 ± 0.003 N/m, and that of the bistoury group was 0.037 ± 0.003 N/m, and the difference between the two groups was statistically significant (p < 0.05). Conclusion: The results indicate that the forceps sampling method has a substantial negative effect on the micromechanical properties of the ECM of the annulus fibrosus. Bistoury sampling method is recommended as the experimental subject for exploring the micromechanics mechanisms of cervical degenerative disease. [ABSTRACT FROM AUTHOR]

Low back pain is a global public and occupational health problem. Approximately 80% of the general population experiences low back pain of varying intensity at some point in their lives. Intervertebral disc degeneration is the main pathology in 42% of patients suffering from low back pain. The intervertebral disc is composed of three separate elements: a central part - nucleus pulposus, an outer part - annulus fibrosus and two cartilaginous endplates covering the upper and lower surfaces of the vertebral bodies. The degenerative process consists of 4 stages: dehydration, cracking, neovascularization and bone changes. As a result of these changes, the biomechanics of the lumbar compartment is disturbed and local and, in some patients, radicular pain occurs. The proven therapeutic approaches for discogenic lumbalgia are divided in conservative (pharmacological and non-pharmacological) and surgical methods for the treatment of this disease. New therapeutic strategies that are being actively investigated include gene therapy, growth factor therapy and inhibition of chemical mediators of pain. Biological therapies that stimulate the recovery processes in the intervertebral discs are still in the experimental stage and more studies are needed to establish their effectiveness in cases of severe degenerative changes. Knowing the pathophysiologic mechanisms of low back pain enables the clinician to differentiate the mechanism that plays the dominant role in the onset of pain and to conduct targeted treatment with optimal results. The aim of this review is to reveal the pathophysiological mechanisms of pain symptomatology in the lumbar spine and to discuss the main therapeutic approaches to address the problem. [ABSTRACT FROM AUTHOR]

Discectomy is the surgical standard of care to relieve low back pain caused by intervertebral disc (IVD) herniation. However, there remains annulus fibrosus (AF) defect and nucleus pulposus (NP) degeneration, which often result in recurrent herniation (re-herniation). Herein, we develop a polyphenol-modified waterborne polyurethane bioadhesives (PPU-glues) to promote therapy prognosis after discectomy. Being composed of tannic acid (TA) mixed cationic waterborne polyurethane nanodispersions (TA/WPU+) and curcumin (Cur) embedded anionic waterborne polyurethane nanodispersions (Cur-WPU-), PPU-glue gels rapidly (<10 s) and exhibits low swelling ratios, tunable degradation rates and good biocompatibility. Due to the application of an adhesion strategy combing English ivy mechanism and particle packing theory, PPU-glue also shows considerable lap shear strength against wet porcine skin (≈58 kPa) and burst pressure (≈26 kPa). The mismatched particle sizes and the opposite charges of TA/WPU+ and Cur-WPU- in PPU-glue bring electrostatic interaction and enhance particle packing density. PPU-glue possesses superior reactive oxygen species (ROS)-scavenging capacity derived from polyphenols. PPU-glue can regulate extracellular matrix (ECM) metabolism in degenerated NP cells, and it can promote therapy biologically and mechanically in degenerated rat caudal discs. In summary, this study highlights the therapeutic approach that combines AF seal and NP augmentation, and PPU-glue holds great application potentials for post discectomy therapy. Currently, there is no established method for the therapy of annulus fibrosus (AF) defect and nucleus pulposus (NP) degeneration after discectomy. Herein, we developed a polyphenol-modified biomimetic polyurethane bioadhesive (PPU-glue) with strong adhesive strength and superior bioactive property. The adhesion strategy that combined a particle packing theory and an English ivy mechanism was firstly applied to the intervertebral disc repair field, which benefited AF seal. The modified method of incorporating polyphenols was utilized to confer with ROS-scavenging capacity, ECM metabolism regulation ability and anti-inflammatory property, which promoted NP augmentation. Thus, PPU-glue attained the synergy effect for post discectomy therapy, and the design principle could be universally expanded to the bioadhesives for other surgical uses. [Display omitted] [ABSTRACT FROM AUTHOR]

The stress relaxation of the TZ region, located at the interface of the Annulus Fibrosus (AF) and Nucleus Pulposus (NP) of the disc, and how its stress is relaxed compared to the adjacent regions is unknown. The current study aimed to identify the TZ stress relaxation properties under different strain magnitudes (0.2, 0.4, and 0.6 mm/mm) and compared the TZ stress relaxation characteristics to the NP and inner AF (IAF) regions at a specific strain magnitude (0.6 mm/mm). The results of the current study revealed that the TZ region exhibited different stress relaxation properties under various strain magnitudes with significantly higher initial (p < 0.008) and reduced stresses (marginally; p = 0.06) at higher strains. Our experimental stress relaxation data revealed a significantly higher equilibrium stress for the IAF compared to the TZ and NP regions (p < 0.001) but not between the TZ and NP regions (p = 0.7). We found that NP radial stress relaxed significantly faster (p < 0.04) than the TZ and NP. Additionally, the current study proposed a simple mathematical model and identified that, consistent with experimental data, the overall effect of region on both the level of decayed stress and the rate at which stress is relaxed was significant (p < 0.006). The current study found a similar stress relaxation characteristic between the NP and TZ regions, while IAF exhibited different stress relaxation properties. It is possible that this mismatch in stress relaxation acts as a shape transformation mechanism triggered by viscoelastic behavior. Our understanding of the biomechanical properties of the transition zone (TZ) in the IVD, a region at the interface of the Nucleus Pulposus (NP) and Annulus Fibrosus (AF), is sparse. Unfortunately, there are no current studies that investigate the TZ stress relaxation properties and how stress is relaxed in the TZ compared to the adjacent regions. For the first time, the current study characterized the stress relaxation properties of the TZ and described how the TZ stress is relaxed compared to its adjacent regions. [Display omitted] [ABSTRACT FROM AUTHOR]

During intervertebral disc (IVD) degeneration, microenvironmental challenges such as decreasing levels of glucose, oxygen, and pH play crucial roles in cell survival and matrix turnover. Antacids, such as Mg(OH)2 and CaCO3, entrapped in microcapsules are capable of neutralizing acidic microenvironments in a controlled fashion and therefore may offer the potential to improve the acidic niche of the degenerated IVD and enhance cell‐based regeneration strategies. The objectives of this work were, first, to develop and characterize antacid microcapsules and assess their neutralization capacity in an acidic microenvironment and, second, to combine antacid microcapsules with cellular microcapsules in a hybrid gel system to investigate their neutralization effect as a potential therapeutic in a disc explant model. To achieve this, we screened five different pH‐ neutralizing agents (Al(OH)3, Mg(OH)2, CaCO3, and HEPES) in terms of their pH neutralization capacities, with Mg(OH)2 or CaCO3 being carried forward for further investigation. Antacid‐alginate microcapsules were formed at different concentrations using the electrohydrodynamic spraying process and assessed in terms of size, buffering kinetics, cell compatibility, and cytotoxicity. Finally, the combination of cellular microcapsules and antacid capsules was examined in a bovine disc explant model under physiological degenerative conditions. Overall, CaCO3 was found to be superior in terms of neutralization capacities, release kinetics, and cellular response. Specifically, CaCO3 elevated the acidic pH to neutral levels and is estimated to be maintained for several weeks based on Ca2+ release. Using a disc explant model, it was demonstrated that CaCO3 microcapsules were capable of increasing the local pH within the core of a hybrid cellular gel system. This work highlights the potential of antacid microcapsules to positively alter the challenging acidic microenvironment conditions typically observed in degenerative disc disease, which may be used in conjunction with cell therapies to augment regeneration. [ABSTRACT FROM AUTHOR]

Background: Intervertebral disc degeneration (IDD) is widely regarded as the primary contributor to low back pain(LBP). As an immune-privileged organ, upon the onset of IDD, various components of the nucleus pulposus (NP) are exposed to the host’s immune system, accumulating cytokines. Cytokines facilitate intercellular communication within the immune system, induce immune cells polarisation, and exacerbate oxidative stress in IDD. Methods: Machine learning was used to identify crucial immune cells. Subsequently, Immune Response Enrichment Analysis (IREA) was conducted on the key immune cells to determine their cytokine responses and polarisation states in IDD. “CellChat” package facilitated the analysis of cell-cell communication. Differential gene expression analysis, PPI network, GO and KEGG pathway enrichment analysis, GSVA, co-expressed gene analysis and key gene-related networks were also performed to explore hub genes and their associated functions. Lastly, the differential expression and functions of key genes were validated through in vitro and in vivo experiments. Results: Through multiple machine learning methods, monocytes were identified as the crucial immune cells in IDD, exhibiting significant differentiation capacity. IREA revealed that monocytes in IDD polarize into an IFN-a1 and IFN-b enriched Mono-a state, potentially intensifying inflammation. Cell–cell communication analysis uncovered alteration in ANNEXIN pathway and a reduction in CXCL signaling between macrophages and monocytes, suggesting immune response dysregulation. Furthermore, ten algorithms identified three hub genes. Both experiments conducted in vitro and in vivo have conclusively shown that IRF7 serves as a crucial target for the treatment of IDD, and its knockdown alleviates IDD. Eight small-molecule drugs were predicted to have therapeutic potential for IDD. Conclusion: These findings offer a multidimensional understanding of the pathogenesis of IDD, pinpointing monocytes and key genes as potential diagnostic and therapeutic targets. They provide novel insights into potential diagnostic and therapeutic targets for IDD. [ABSTRACT FROM AUTHOR]

Objective: The correlation between high-intensity zone (HIZ) of lumbar disc magnetic resonance imaging (MRI) and discogenic low back pain (DLBP) is currently controversial, this study aimed to systematically evaluate the correlation between HIZ of lumbar disc MRI and positive discography, as well as its diagnostic value for DLBP. Method: Databases were searched to include research literature on high intensity zone (HIZ) related to discography and DLBP diagnosis. HIZ is a separate small, confined area of high signal located at the posterior border of the annulus fibrosus on MRI T2-weighted images of the lumbar spine, which is separated from the nucleus pulposus but has a higher signal than the nucleus pulposus. Studies on the correlation of HIZ with discography and DLBP diagnosis were searched in the Pubmed, EMBASE, Cochrane Central, Science Direct, China Knowledge Network, Wanfang Database, and China Biomedical Literature Databases, Scopus from January 1992 to June 2024. The outcomes were diagnostic values of HIZ for DLBP. The risk assessment was performed by Deeks' funnel methods in the Stata 17.0 software after 2 investigators independently screened the literature, extracted information and evaluated the risk of bias of the included studies. Results: A total of 25 studies including 5889 patients were included. meta-analysis showed that the sensitivity of HIZ for the diagnosis of DLBP was (0.49, 95% CI [0.37,0.61]) and specificity was (0.89, 95% CI [0.85,0.93]); the positive likelihood ratio was (4.52, 95% CI [3.28,6.25]) and the negative likelihood ratio was (0.58, 95% CI [0.46,0.71]). The diagnostic ratio was (7.87, 95% CI [5.05,12.26]). Conclusion: The available evidence suggests that HIZ has acceptable sensitivity and high specificity in the diagnosis of DLBP. Due to the limitation of the number and quality of included studies, the above conclusions need to be validated by more high-quality studies. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IVDD) is a primary contributor to low back pain and poses a considerable burden to society. However, the molecular mechanisms underlying IVDD remain to be elucidated. PR/SET domain 1 (PRDM1) regulates cell proliferation, apoptosis, and inflammatory responses in various diseases. Despite these regulatory functions, the mechanism of action of PRDM1 in IVDD remains unexplored. In this study, we investigated the role and underlying mechanisms of action of PRDM1 in IVDD progression. The expression of PRDM1 in nucleus pulposus (NP) tissues and NP cells (NPCs) was assessed using western blotting, immunohistochemistry, and immunofluorescence. The effects of PRDM1 on IVDD progression were investigated in vitro and in vivo. Mechanistically, mRNA sequencing, chromatin immunoprecipitation, and dual-luciferase reporter assays were performed to confirm that PRDM1 triggered CASP1 transcription. Our study demonstrated for the first time that PRDM1 expression was substantially upregulated in degenerated NP tissues and NPCs. PRDM1 overexpression promoted NPCs pyroptosis by inhibiting mitophagy and exacerbating IVDD progression, whereas PRDM1 silencing exerted the opposite effect. Furthermore, PRDM1 activated CASP1 transcription, thereby promoting NPCs pyroptosis in vitro. Notably, CASP1 silencing reversed the effects of PRDM1 on the NPCs. To the best of our knowledge, this study is the first to demonstrate that PRDM1 silencing inhibits NPCs pyroptosis by repressing CASP1 transcription, which may be a promising new therapeutic target for IVDD. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IVDD) is a prevalent musculoskeletal disorder that involves the excessive accumulation of reactive oxygen species (ROS), resulting in mitochondrial dysfunction and matrix metabolism imbalance in nucleus pulposus cells (NPCs). Selenium, an indispensable trace element, plays a crucial role in maintaining mitochondrial redox homeostasis by being incorporated into antioxidant selenoproteins as selenocysteine. In this study, we employed a straightforward synthesis method to produce selenium nanoparticles (SeNPs) with consistent size and distribution, and evaluated their potential protective effects in ameliorating IVDD. In a simulated inflammatory environment induced by interleukin-1beta (IL-1β) in vitro, SeNPs demonstrated a protective effect on the matrix synthesis capacity of NPCs through the up-regulation of aggrecan and type II collagen, while concurrently suppressing the expression of matrix degradation enzymes including MMP13 and ADAMTS5. Additionally, SeNPs preserved mitochondrial integrity and restored impaired mitochondrial energy metabolism by activating glutathione peroxidase1 (GPX1) to rebalance redox homeostasis. In a rat lumbar disc model induced by puncture, the local administration of SeNPs preserved the hydration of nucleus pulposus tissue, promoted matrix deposition, and effectively mitigated the progression of IVDD. Our results indicate that the enhancement of GPX1 by SeNPs may offer a promising therapeutic approach for IVDD by restoring mitochondrial function and redox homeostasis. [ABSTRACT FROM AUTHOR]

This study investigates the potential molecular mechanisms by which O-GlcNAc modification of YTHDF2 regulates the cell cycle and participates in intervertebral disc degeneration (IDD). We employed transcriptome sequencing to identify genes involved in IDD and utilized bioinformatics analysis to predict key disease-related genes. In vitro mechanistic validation was performed using mouse nucleus pulposus (NP) cells. Changes in reactive oxygen species (ROS) and cell cycle were assessed through flow cytometry and CCK-8 assays. An IDD mouse model was also established for in vivo mechanistic validation, with changes in IDD severity measured using X-rays and immunohistochemical staining. Bioinformatics analysis revealed differential expression of YTHDF2 in NP cells of normal and IDD mice, suggesting its potential as a diagnostic gene for IDD. In vitro cell experiments demonstrated that YTHDF2 expression and O-GlcNAcylation were reduced in NP cells under H2O2 induction, leading to inhibition of the cell cycle through decreased stability of CCNE1 mRNA. Further, in vivo animal experiments confirmed a decrease in YTHDF2 expression and O-GlcNAcylation in IDD mice, while overexpression or increased O-GlcNAcylation of YTHDF2 promoted CCNE1 protein expression, thereby alleviating IDD pathology. YTHDF2 inhibits its degradation through O-GlcNAc modification, promoting the stability of CCNE1 mRNA and the cell cycle to prevent IDD formation. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IVDD) is a degenerative disease accompanied by the loss of nucleus pulposus cells and the degradation of extracellular matrix (ECM), which tends to be associated with lower back pain. The ECM and various types of cell death in IVDD are regulated by multiple factors, such as inflammatory responses and oxidative stress. The glutathione (GSH) redox system is the most important antioxidant defense system in cells. GSH is one of the most abundant thiol antioxidants in mammalian cells, which functions directly and indirectly by scavenging peroxides through the GSH redox system. In these reactions, GSH is oxidized by electrophilic substances, such as reactive oxygen species and free radicals, to form glutathione disulfide to exert antioxidative effects. It has been reported that GSH can protect cells against the damage of oxidative stress and various pathophysiological stimulus that can lead to different types of cell death. In addition, it was reported that the level of GSH widely participates in apoptosis, autophagy, ferroptosis, and oxidative stress in many diseases including osteoarthritis and IVDD. Therefore, we summarized the effects of GSH on ECM metabolism and cells' functions during IVDD. In addition, we summarized the regulatory effects of small molecule compounds on GSH to explore potential ways to regulate the level of GSH. Better understanding the underlying role of GSH in regulating IVDD will facilitate the goal of preventing and retarding the progress of IVDD in the future. [ABSTRACT FROM AUTHOR]

Low back pain is a common clinical symptom of intervertebral disc degeneration (IVDD), which seriously affects the quality of life of the patients. The abnormal apoptosis and senescence of nucleus pulposus cells (NPCs) play important roles in the pathogenesis of IVDD. PHLDA2 is an imprinted gene related to cell apoptosis and tumour progression. However, its role in NPC degeneration is not yet clear. Therefore, this study was set to explore the effects of PHLDA2 on NPC senescence and apoptosis and the underlying mechanisms. The expression of PHLDA2 was examined in human nucleus pulposus (NP) tissues and NPCs. Immunohistochemical staining, magnetic resonance imaging imaging and western blot were performed to evaluate the phenotypes of intervertebral discs. Senescence and apoptosis of NPCs were assessed by SA‐β‐galactosidase, flow cytometry and western blot. Mitochondrial function was investigated by JC‐1 staining and transmission electron microscopy. It was found that the expression level of PHLDA2 was abnormally elevated in degenerated human NP tissues and NPCs. Furthermore, knockdown of PHLDA2 can significantly inhibit senescence and apoptosis of NPCs, whereas overexpression of PHLDA2 can reverse senescence and apoptosis of NPCs in vitro. In vivo experiment further confirmed that PHLDA2 knockdown could alleviate IVDD in rats. Knockdown of PHLDA2 could also reverse senescence and apoptosis in IL‐1β‐treated NPCs. JC‐1 staining indicated PHLDA2's knockdown impaired disruption of the mitochondrial membrane potential and also ameliorated superstructural destruction of NPCs as showed by transmission electron microscopy. Finally, we found the PHLDA2 knockdown promoted Collagen‐II expression and suppressed MMP3 expression in NPCs by repressing wnt/β‐catenin pathway. In conclusion, the results of the present study showed that PHLDA2 promotes IL‐1β‐induced apoptosis and senescence of NP cells via mitochondrial route by activating the Wnt/β‐catenin pathway, and suggested that therapy targeting PHLDA2 may provide valuable insights into possible IVDD therapies. [ABSTRACT FROM AUTHOR]

Simple Summary: Hydrated nucleus pulposus extrusion (HNPE) is a well-known pathological condition in veterinary neurology. Any breed of middle-aged or older dogs (median 9 years old) can be affected; it has an acute spontaneous onset, is rarely exercise-associated, and commonly affects the cervical region, causing tetraparesis or tetraplegia and mild cervical hyperesthesia. This study presents the first documented case of double cervical adjacent HNPEs in a small breed dog. A 9-year-old 6 Kg intact male Yorkshire terrier was referred for an acute onset of non-ambulatory tetraparesis. MR examination of the cervical spine showed two concurrent HNPEs at sites C3-C4 and C4-C5. The dog had a remission of symptoms with conservative therapy and physiotherapy. A 9-year-old Yorkshire terrier was brought to the emergency department for inability to maintain the correct station with acute onset. Neurological examination showed a non-ambulatory tetraparesis, spontaneous proprioceptive deficit in all limbs, and decreased flexor reflex in the forelimbs. The neurological symptoms suggested a cranial cervical spinal cord with suspicion of spinal shock. The clinical differential diagnoses included degenerative (intervertebral disc extrusion), vascular, inflammatory, or neoplastic disease. No pathological findings were evident in the hematobiochemical tests or in the radiograph examination. MRI examination of the cervical spine showed the presence of two adjacent hydrated nucleus pulposus extrusions at C3-C4 and C4-C5 tracts. Treatment included analgesic and non-steroidal anti-inflammatory therapy; movement restriction was initially necessary, followed by physiotherapy. Follow-up at 4 weeks showed complete recovery. A telephone follow-up after 3 months with the owner confirmed the absence of symptoms. This article reports the first double cervical HNPE case in a dog, adding the possibility that the disease may present in this form and the success of conservative treatment as described in the literature. [ABSTRACT FROM AUTHOR]

Background: The nucleus pulposus (NP) degradation is a primary factor in intervertebral disk degeneration (IVD) and a major contributor to low back pain. Intervertebral disk-derived stem cell (IVDSC) therapy presents a promising solution, yet identifying suitable cell carriers for NP transplantation remains challenging. The present study investigates this issue by developing smart injectable hydrogels incorporating vanillin (V) and hyaluronic acid (HA) encapsulated with IVDSCs to facilitate IVD regeneration. Materials and methods: The hydrogel was cross linked by carbodiimide-succinimide (EDC-NHS) method. Enhanced mechanical properties were achieved by integrating collagen and HA into the hydrogel. The rheological analysis revealed the pre-gel viscoelastic and shear-thinning characteristics. Results: In vitro, cell viability was maintained up to 500 µg/mL, with a high proliferation rate observed over 14 days. The hydrogels supported multilineage differentiation, as confirmed by osteogenic and adipogenic induction. Anti-inflammatory effects were demonstrated by reduced cytokine release (TNF-α, IL-6, IL-1β) after 24 h of treatment. Gene expression studies indicated elevated levels of chondrocyte markers (Acan, Sox9, Col2). In vivo, hydrogel injection into the NP was monitored via X-ray imaging, showing a significant increase in disk height index (DHI%) after 8 weeks, alongside improved histologic scores. Biomechanical testing revealed that the hydrogel effectively mimicked NP properties, enhancing compressive stiffness and reducing neutral zone stiffness post-denucleation. Conclusion: The results suggest that the synthesized VCHA-NP hydrogel can be used as an alternative to NPs, offering a promising path for IVD regeneration. The of synthesis of hydrogel VCHA-NP for IVD, illustrated graphically. [ABSTRACT FROM AUTHOR]

Background: Intervertebral disc degeneration (IDD) progression involves multiple factors, including loss of nucleus pulposus cells and extracellular matrix as the basic pathological mechanism of degeneration, and is closely related to cellular senescence and immune cell infiltration. The aim of study was to identify critical cellular senescence-related genes and immune cell infiltration characteristics in IDD. Methods: Four datasets, including GSE70362, GSE112216, GSE114169, and GSE150408, were downloaded from the Gene Expression Omnibus database. The senescence-related genes were acquired from the CellAge Database and intersected with differentially expressed genes (DEGs) between IDD and control samples for senescence-related DEGs (SRDEGs). Protein-protein interaction (PPI) network analysis was performed to obtain ten hub SRDEGs. A consensus cluster analysis based on these hub genes was performed to divide the patients into clusters. The functional enrichment, and immune infiltration statuses of the clusters were compared. Weighted gene co-expression network analysis was used to identified key gene modules. The overlapping genes from key modules, DEGs of clusters and hub SRDEGs were intersected to obtain potential biomarkers. To verify the expression of potential biomarkers, quantitative polymerase chain reaction (qPCR) and immunohistochemistry were performed by using human intervertebral disc tissues. Results: In the GSE70362 dataset, a total of 364 DEGs were identified, of which 150 were upregulated and 214 were downregulated, and 35 genes were selected as SRDEGs. PPI analysis revealed ten hub SRDEGs and consensus cluster analysis divided the patients into two clusters. Compared to Cluster 2, Cluster 1 was highly enriched in extracellular matrix organization and various metabolic process. The level of Follicular T helper cells in the Cluster 1 was significantly higher than that in the Cluster 2. IGFBP3 and NQO1 were identified as potential biomarkers. The remaining 3 datasets, and the result of qPCR and immunohistochemistry showed that the expression levels of NQO1 and IGFBP3 in the degenerated group were higher than those in the control or treatment groups. Conclusion: Senescence-related genes play a key role in the development and occurrence of IDD. IGFBP3 and NQO1 are strongly correlated with immune infiltration in the IDD and could become novel therapeutic targets that prevent the progression of IDD. [ABSTRACT FROM AUTHOR]

The transplantation of collagen hydrogels encapsulating human dental pulp stem cell (DPSC)‐derived chondrogenic cells is potentially a novel approach for the regeneration of degenerated nucleus pulposus (NP) and cartilage. Grafted cell migration allows cells to disperse in the hydrogels and the treated tissue from the grafted location. We previously reported the cell migration in type I and type II hydrogels. It is important to explore further how cell culture time affect the cell motility. In this study, we observed the decreased motility of DPSC‐derived chondrogenic cells after culturing for 2 weeks compared with cells cultured for 2 days in these gels. The Alamarblue assay showed the cell proliferation during the two‐week cell culture period. The findings suggest that the transitions of cell motility and proliferation during the longer culture time. The result indicates that the early culture stage is an optimal time for cell transplantation. In a degenerated disc, the expression of IL‐1β and TNFα increased significantly compared with healthy tissue and therefore may affect grafted cell migration. The incorporation of IL‐1β and TNFα into the collagen hydrogels decreased cell motility. The study indicates that the control of IL‐1β and TNFα production may help to maintain cell motility after transplantation. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Traditionally, the intervertebral disks' (IVD) nucleus pulposus (NP) and annulus fibrosus (AF) are considered to have few cellular components and cell junctions. Patients affected by a new variant of endemic pemphigus foliaceus in El Bagre, Colombia, experience back pain in the spinal areas of the lower and upper back. Here, we investigate the reactivity of the patient's autoantibodies to structures in and around the IVDs at the cellular level.We first administered a questionnaire and performed a medical examination. We then tested for autoreactivity against IVDs by indirect immunofluorescence, confocal microscopy, and reflectance confocal microscopy using bovine and human tissues as antigen sources. We tested 45 sera from patients affected by the disease and 45 control sera from the endemic area matched by age, gender, demographics, and work activity.Most of the patient sera revealed polyclonal antibodies against newly discovered cell junctions in the NP and AF, including their translamellar cross‐bridges. Additional reactivities were detected against cell junctions in the spinal cord neurons, paraspinal nerves, blood vessels, anterior and posterior longitudinal ligaments, and paraspinal skeletal muscles. The reactivities of the patient's autoantibodies co‐localized with those of commercially available antibodies to desmoplakins I–II, armadillo repeat gene deleted in velo‐cardio‐facial syndrome, plakophilin‐4, and myocardium‐enriched zonula occludens‐1‐associated protein (p < 0.001).We discovered novel complex cell junctions in the IVDs using patients' autoantibodies. These discoveries open a new chapter in the knowledge of IVD, representing a breakthrough pertinent to many diseases. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IVDD) is a chronic degenerative disease involving the aging and loss of proliferative capacity of nucleus pulposus cells (NPCs), processes heavily dependent on mitochondrial dynamics and autophagic flux. This study finds that the absence of BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3) is associated with senescence‐related NPC degeneration, disrupting mitochondrial quality control. Bone marrow mesenchymal stem cells (BMSCs) have multidirectional differentiation potential and produce extracellular vesicles containing cellular activators. Therefore, in this study, BMSCs are induced under hypoxic stimulation to deliver BNIP3‐rich extracellular vesicles to NPCs, thereby alleviating aging‐associated mitochondrial autophagic flux, promoting damaged mitochondrial clearance, and restoring mitochondrial quality control. Mechanistically, BNIP3 is shown to interact with the membrane‐bound protein annexin A2 (ANXA2), enabling the liberation of the transcription factor EB (TFEB) from the ANXA2‐TFEB complex, promoting TFEB nuclear translocation, and regulating autophagy and lysosomal gene activation. Furthermore, a rat model of IVDD is established and verified the in vivo efficacy of the exosomes in repairing disc injuries, delaying NPC aging, and promoting extracellular matrix (ECM) synthesis. In summary, hypoxia‐induced BMSC exosomes deliver BNIP3‐rich vesicles to alleviate disc degeneration by activating the mitochondrial BNIP3/ANXA2/TFEB axis, providing a new target for IVDD treatment. [ABSTRACT FROM AUTHOR]

Background: Limited supply of certain nutrients and deregulation of nucleus pulposus (NP) plays a key role in the pathogenesis of intervertebral disc degeneration (IVDD). However, whether nutrient deprivation-induced cell death, particularly disulfidptosis, contributes to the depletion of NP cells and the development of IVDD, is unknown. Methods: RNA-seq, single-cell RNA-seq, and Genome-wide DNA methylation datasets of nucleus pulposus tissue were collected for bioinformatic analysis. Predictive models of disulfidptosis related genes in IVDD were constructed by machine learning and their differential expression was analyzed. In addition, we performed cell subsets identification analysis, cell-cell communications analysis, and functional enrichment analysis of key genes in the core subset based on single-cell RNA-seq data of NP tissues isolated from one normal sample and one IVDD sample. Finally, glucose deprivation-induced disulfidptosis in human NP cells (HNPCs) was verified by various cell death inhibitors and disulfidptosis-related molecular markers. Results: We found the disulfidptosis signal was significantly activated in the IVDD group. Using single-cell RNA-seq analysis, we focused on the chondrocytes and found that disulfidptosis-related genes significantly highly expressed in the IVDD C4 chondrocyte subset, which was identified as a new disulfidptosis-associated cell subset. Correlation analysis revealed the negative correlation between SLC7A11 (driving gene of disulfidptosis) and the glucose transporter GLUTs (SLC2A1-4) family genes (suppressing genes of disulfidptosis) in the IVDD group. We also found obvious cell death in HNPC upon glucose starvation, while employment of various cell death inhibitors could not inhibit glucose starvation-induced death in HNPCs. Moreover, the accumulation of disulfide bonds in cytoskeletal proteins was indicated by slowed migration in non-reducible protein blotting experiments. 2-DG, a key disulfidptosis inhibitor, significantly rescued cell death caused by glucose starvation through lowering the NADP+/NADPH ratio. Conclusions: We validated the occurrence of disulfidptosis in HPNCs and identified a novel disulfidptosis-associated cell subset, followed by experimental verification of disulfidptosis in a glucose-limited context to mimic a fall in nutrient supply during the development disc degeneration. These findings provided new insights into the pathological mechanisms of IVDD and encourage us to explore potential therapeutic targets involved in the regulation of disulfidptosis for the prevention of intervertebral disc degeneration. [ABSTRACT FROM AUTHOR]

Methods: Single-cell transcriptomics and high-throughput transcriptomics were used to screen factors significantly correlated with intervertebral disc degeneration (IDD). Expression changes of CFIm25 were determined via RT-qPCR and Western blot. NP cells were isolated from mouse intervertebral discs and induced to degrade with TNF-α and IL-1β. CFIm25 was knocked out using CRISPR-Cas9, and CFIm25 knockout and overexpressing nucleus pulposus (NP) cell lines were generated through lentiviral transfection. Proteoglycan expression, protein expression, inflammatory factor expression, cell viability, proliferation, migration, gene expression, and protein expression were analyzed using various assays (alcian blue staining, immunofluorescence, ELISA, CCK-8, EDU labeling, transwell migration, scratch assay, RT-qPCR, Western blot). The GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA was designed, and its effects on NP regeneration were assessed through in vitro and mouse model experiments. The progression of IDD in mice was evaluated using X-ray, H&E staining, and Safranin O-Fast Green staining. Immunohistochemistry was performed to determine protein expression in NP tissue. Proteomic analysis combined with in vitro and in vivo experiments was conducted to elucidate the mechanisms of hydrogel action. Results: CFIm25 was upregulated in IDD NP tissue and significantly correlated with disease progression. Inhibition of CFIm25 improved NP cell degeneration, enhanced cell proliferation, and migration. The hydrogel effectively knocked down CFIm25 expression, improved NP cell degeneration, promoted cell proliferation and migration, and mitigated IDD progression in a mouse model. The hydrogel inhibited inflammatory factor expression (IL-6, iNOS, IL-1β, TNF-α) by targeting the p38/NF-κB signaling pathway, increased collagen COLII and proteoglycan Aggrecan expression, and suppressed NP degeneration-related factors (COX-2, MMP-3). Conclusion: The study highlighted the crucial role of CFIm25 in IDD and introduced a promising therapeutic strategy using a porous spherical GelMA-HAMA hydrogel loaded with APET×2 polypeptide and sgRNA. This innovative approach offers new possibilities for treating degenerated intervertebral discs. [ABSTRACT FROM AUTHOR]

Diabetes mellitus (DM) is a well-documented risk factor of intervertebral disc degeneration (IVDD). The current study was aimed to clarify the effects and mechanisms of NADH: ubiquinone oxidoreductase subunit A3 (NDUFA3) in human nucleus pulposus cells (HNPCs) exposed to high glucose. NDUFA3 was overexpressed in HNPCs via lenti-virus transduction, which were co-treated with high glucose and rotenone (a mitochondrial complex I inhibitor) for 48 h. Cell activities were assessed for cell viability, cell apoptosis, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) ratio, oxygen consumption rate (OCR) and mitochondrial complexes I activities. High glucose decreased cell viability, increased apoptotic cells, increased ROS production, decreased MMP levels and OCR values in HNPCs in a dose-dependent manner. Rotenone co-treatment augmented the high glucose-induced injuries on cell viability, apoptosis, ROS production and mitochondrial function. NDUFA3 overexpression counteracted the high glucose-induced injuries in HNPCs. HDAC/H3K27ac mechanism was involved in regulating NDUFA3 transcription. NDUFA3 knockdown decreased cell viability and increased apoptotic cells, which were reversed by ROS scavenger N-acetylcysteine. HDAC/H3K27ac-mediated transcription of NDUFA3 protects HNPCs against high glucose-induced injuries through suppressing cell apoptosis, eliminating ROS, improving mitochondrial function and oxidative phosphorylation. This study sheds light on candidate therapeutic targets and deepens the understanding of molecular mechanisms behind DM-induced IVDD. [ABSTRACT FROM AUTHOR]

Background: Intervertebral disc degeneration (IDD) can lead to disc herniation and spinal instability, sometimes requiring surgical intervention. Currently, estrogen has a potential protective effect on IDD, and estrogen is associated with an increased risk of some cancers, such as breast and endometrial cancer. Therefore, it is important to identify natural compounds that estrogen analogues treat IDD while reducing the risk of tumor development. Objective: This study aims to explore a natural metabolic treatment strategy by targeting CRISP2 with the natural compound Hesperidin to mimic the protective effects of estrogen on IDD and reduce the risk of tumor development. Methods: Microarray data from healthy volunteers and IDD patients were extracted from the Gene Expression Omnibus (GEO) database, and RNA sequencing and clinical data from various cancer types were analyzed. Differentially expressed genes (DEGs) were identified using the Bioconductor Limma package, followed by principal component analysis, volcano plot, and heatmap visualization. Additionally, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, CIBERSORT and ssGSEA immune cell infiltration assessments, survival analysis, metabolite enrichment analysis, and molecular docking were performed. Hesperidin's interaction with CRISP2 was further validated through molecular docking and experimental studies. Results: Hesperidin significantly reduced the expression of CRISP2, iNOS, and COX2 in IDD models, decreased reactive oxygen species (ROS) and apoptosis, and diminished inflammatory markers. CIBERSORT and ssGSEA analyses revealed a correlation between CRISP2 and immune cell infiltration. Survival analysis demonstrated that CRISP2 expression levels were associated with patient survival across various cancer types. Hesperidin was found to mimic estrogen's effects on IDD and reduce tumor progression. Cell culture and experimental validation confirmed Hesperidin's protective effects on nucleus pulposus cells (NPCs). Conclusion: Hesperidin, as a potential natural metabolic regulator, not only has therapeutic effects on IDD but may also synergize with estrogen therapy to promote spinal health without increasing cancer risk. This study presents a new clinical approach for IDD treatment and lays the foundation for further drug development and experimental research. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IDD) is a major cause of discogenic pain, and is attributed to the dysfunction of nucleus pulposus, annulus fibrosus, and cartilaginous endplate (CEP). Osteopontin (OPN), a glycoprotein, is highly expressed in the CEP. However, little is known on how OPN regulates CEP homeostasis and degeneration, contributing to the pathogenesis of IDD. Here, we investigate the roles of OPN in CEP degeneration in a mouse IDD model induced by lumbar spine instability and its impact on the degeneration of endplate chondrocytes (EPCs) under pathological conditions. OPN is mainly expressed in the CEP and decreases with degeneration in mice and human patients with severe IDD. Conditional Spp1 knockout in EPCs of adult mice enhances age-related CEP degeneration and accelerates CEP remodeling during IDD. Mechanistically, OPN deficiency increases CCL2 and CCL5 production in EPCs to recruit macrophages and enhances the activation of NLRP3 inflammasome and NF-κB signaling by facilitating assembly of IRAK1-TRAF6 complex, deteriorating CEP degeneration in a spatiotemporal pattern. More importantly, pharmacological inhibition of the NF-κB/NLRP3 axis attenuates CEP degeneration in OPN-deficient IDD mice. Overall, this study highlights the importance of OPN in maintaining CEP and disc homeostasis, and proposes a promising therapeutic strategy for IDD by targeting the NF-κB/NLRP3 axis. [ABSTRACT FROM AUTHOR]

Cell therapy strategies hold great promise for nucleus pulposus (NP) regeneration and intervertebral disc degeneration (IVDD) treatment. However, their therapeutic efficiency is compromised by the anoikis of administered cells and the harsh environment in degenerated intervertebral discs (IVD). Inspired by the ability of nucleobases to form multiple H‐bonds, a nucleobase‐driven self‐gelling strategy is proposed for the incorporation of nucleobases (e.g., thymine) into hyaluronic acid (HA) chains to trigger gel formation through enhanced intermolecular H‐bond interactions. An aqueous solution of a thymine‐modified HA (HAT) supramolecular polymer is shown to exhibit self‐gelation behavior, injectability, tissue adhesion, and hydration capacity (comparable to that observed in the NP tissue of a 25‐year‐old adult). These characteristics enable the injection and filling of the HAT hydrogel system in the IVD, integration of the separated NP tissues, restoration of the biomechanical functions of the degenerated IVD, and securing of the encapsulated cells in the NP site. Manganese dioxide (MnO2) nanoparticles incorporated into the HAT system (HATMn) regulate oxidative stress and the hypoxic microenvironment in degenerated IVD, ensuring the viability of the encapsulated cells. The 12‐week in vivo study results demonstrate that the administration of the MSCs‐laden HATMn system (HATMn‐MSCs) effectively restores the structure and function of degenerated IVD. [ABSTRACT FROM AUTHOR]

Degenerative disc disease (DDD) represents a significant global health challenge, yet its underlying molecular mechanisms remain elusive. This study aimed to investigate the role of type 1 phosphatidylinositol 4‐phosphate 5‐kinase (Pip5k1) in intervertebral disc (IVD) homeostasis and disease. All three Pip5k1 isoforms, namely Pip5k1α, Pip5k1β, and Pip5k1γ, were detectable in mouse and human IVD tissues, with Pip5k1γ displaying a highest expression in nucleus pulposus (NP) cells. The expression of Pip5k1γ was significantly down‐regulated in the NP cells of aged mice and patients with severe DDD. To determine whether Pip5k1γ expression is required for disc homeostasis, we generated a Pip5k1γfl/fl; AggrecanCreERT2 mouse model for the conditional knockout of the Pip5k1γ gene in aggrecan‐expressing IVD cells. Our findings revealed that the conditional deletion of Pip5k1γ did not affect the disc structure or cellular composition in 5‐month‐old adult mice. However, in aged (15‐month‐old) mice, this deletion led to several severe degenerative disc defects, including decreased NP cellularity, spontaneous fibrosis and cleft formation, and a loss of the boundary between NP and annulus fibrosus. At the molecular level, the absence of Pip5k1γ reduced the anabolism of NP cells without markedly affecting their catabolic or anti‐catabolic activities. Moreover, the loss of Pip5k1γ significantly dampened the activation of the protective Ampk pathway in NP cells, thereby accelerating NP cell senescence. Notably, Pip5k1γ deficiency blunted the effectiveness of metformin, a potent Ampk activator, in activating the Ampk pathway and mitigating lumbar spine instability (LSI)‐induced disc lesions in mice. Overall, our study unveils a novel role for Pip5k1γ in promoting anabolism and maintaining disc homeostasis, suggesting it as a potential therapeutic target for DDD. [ABSTRACT FROM AUTHOR]

The nucleus pulposus is in a hypoxic environment in the human body, and when intervertebral disc degeneration (IVDD) occurs, the hypoxic environment is disrupted. Nucleus pulposus cell (NPC) ferroptosis is one of the causes of IVDD. N6‐methyladenosine (m6A) and its reader protein YTHDF1 regulate cellular activities by affecting RNA metabolism. However, the regulation of ferroptosis in NPCs by m6A‐modified RNAs under hypoxic conditions has not been as well studied. In this study, through in vitro and in vivo experiments, we explored the underlying mechanism of HIF‐1α and YTHDF1 in regulating ferroptosis in NPCs. The results indicated that the overexpression of HIF‐1α or YTHDF1 suppressed NPC ferroptosis; conversely, the knockdown of HIF‐1α or YTHDF1 increased ferroptosis levels in NPCs. Luciferase reporter assays and chromatin immunoprecipitation demonstrated that HIF‐1α regulated YTHDF1 transcription by directly binding to its promoter region. Polysome profiling results showed that YTHDF1 promoted the translation of SLC7A11 and consequently the expression of the anti‐ferroptosis protein GPX4 by binding to m6A‐modified SLC7A11 mRNA. In conclusion, HIF‐1α‐induced YTHDF1 expression reduces NPC ferroptosis and delays IVDD by promoting SLC7A11 translation in a m6A‐dependent manner. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IDD) is an age‐related disease and is responsible for low back pain. Oxidative stress‐induced cell death plays a fundamental role in IDD pathogenesis. Cuproptosis is a recently discovered form of programmed cell death dependent on copper availability. Whether cuproptosis is involved in IDD progression remains unknown. Herein, we established in vitro and in vivo models to investigate cuproptosis in IDD and the mechanisms by which oxidative stress interacts with copper sensitivity in nucleus pulposus cells (NPCs). We found that ferredoxin‐1 (FDX1) content increased in both rat and human degenerated discs. Sublethal oxidative stress on NPCs led to increased FDX1 expression, tricarboxylic acid (TCA) cycle‐related proteins lipoylation and aggregation, and cell death in the presence of Cu2+ at physiological concentrations, while FDX1 knockdown inhibited cell death. Since copper homeostasis is involved in copper‐induced cytotoxicity, we investigated the role of copper transport‐related proteins, including importer (CTR1) and efflux pumps (ATPase transporter, ATP7A, and ATP7B). CTR1 and ATP7A content increased under oxidative stress, and blocking CTR1 reduced oxidative stress/copper‐induced TCA‐related protein aggregation and cell death. Moreover, oxidative stress promoted the expression of specific protein 1 (SP1) and SP1‐mediated CTR1 transcription. SP1 inhibition decreased cell death rates, preserved disc hydration, and alleviated tissue degeneration. This suggests that oxidative stress upregulates FDX1 expression and copper flux through promoting SP1‐mediated CTR1 transcription, leading to increased TCA cycle‐related protein aggregation and cuproptosis. This study highlights the importance of cuproptosis in IDD progression and provides a promising therapeutic target for IDD treatment. [ABSTRACT FROM AUTHOR]

Introduction: The disco-vertebral junction (DVJ) of the lumbar spine contains thin structures with short T2 values, including the cartilaginous endplate (CEP) sandwiched between the bony vertebral endplate (VEP) and the nucleus pulposus (NP). We previously demonstrated that ultrashort-echo-time (UTE) MRI, compared to conventional MRI, is able to depict the tissues at the DVJ with improved contrast. In this study, we sought to further optimize UTE MRI by characterizing the contrast-to-noise ratio (CNR) of these tissues when either single echo or echo subtraction images are used and with varying echo times (TEs). Methods: In four cadaveric lumbar spines, we acquired 3D Cones (a UTE sequence) images at varying TEs from 0.032 ms to 16 ms. Additionally, spin echo T1- and T2-weighted images were acquired. The CNRs of CEP-NP and CEP-VEP were measured in all source images and 3D Cones echo subtraction images. Results: In the spin echo images, it was challenging to distinguish the CEP from the VEP, as both had low signal intensity. However, the 3D Cones source images at the shortest TE of 0.032 ms provided an excellent contrast between the CEP and the VEP. As the TE increased, the contrast decreased in the source images. In contrast, the 3D Cones echo subtraction images showed increasing CNR values as the second TE increased, reaching statistical significance when the second TE was above 10 ms (p < 0.05). Conclusions: Our study highlights the feasibility of incorporating UTE MRI for the evaluation of the DVJ and its advantages over conventional spin echo sequences for improving the contrast between the CEP and adjacent tissues. Additionally, modulation of the contrast for the target tissues can be achieved using either source images or subtraction images, as well as by varying the echo times. [ABSTRACT FROM AUTHOR]

Intervertebral disc degeneration (IVDD) is a common chronic orthopaedic disease in orthopaedics that imposes a heavy economic burden on people and society. Although it is well established that IVDD is associated with genetic susceptibility, ageing and obesity, its pathogenesis remains incompletely understood. Previously, IVDD was thought to occur because of excessive mechanical loading leading to destruction of nucleus pulposus cells (NPCs), but studies have shown that IVDD is a much more complex process associated with inflammation, metabolic factors and NPCs death and can involve all parts of the disc, characterized by causing NPCs death and extracellular matrix (ECM) degradation. The damage pattern of NPCs in IVDD is like that of some programmed cell death, suggesting that IVDD is associated with programmed cell death. Although apoptosis and pyroptosis of NPCs have been studied in IVDD, the pathogenesis of intervertebral disc degeneration can still not be fully elucidated by using only traditional cell death modalities. With increasing research, some new modes of cell death, PANoptosis, ferroptosis and senescence have been found to be closely related to intervertebral disc degeneration. Among these, PANoptosis combines essential elements of pyroptosis, apoptosis and necroptosis to form a highly coordinated and dynamically balanced programmed inflammatory cell death process. Furthermore, we believe that PANoptosis may also crosstalk with pyroptosis and senescence. Therefore, we review the progress of research on multiple deaths of NPCs in IVDD to provide guidance for clinical treatment. [ABSTRACT FROM AUTHOR]

Presently, the clinical treatment of intervertebral disc degeneration (IVDD) remains challenging, but the strategy of simultaneously overcoming the overactive inflammation and restoring the anabolic/catabolic balance of the extracellular matrix (ECM) in the nucleus pulposus (NP) has become an effective way to alleviate IVDD. IL-1ra, a natural antagonist against IL-1β, can mitigate inflammation and promote regeneration in IVDD. Chondroitin sulfate (CS), an important component of the NP, can promote ECM synthesis and delay IVDD. Thus, these were chosen and integrated into functionalized microspheres to achieve their synergistic effects. First, CS-functionalized microspheres (GelMA-CS) with porous microstructure, good monodispersion, and about 200 µm diameter were efficiently and productively fabricated using microfluidic technology. After lyophilization, the microspheres with good local injection and tissue retention served as the loading platform for IL-1ra and achieved sustained release. In in vitro experiments, the IL-1ra-loaded microspheres exhibited good cytocompatibility and efficacy in inhibiting the inflammatory response of NP cells induced by lipopolysaccharide (LPS) and promoting the secretion of ECM. In in vivo experiments, the microspheres showed good histocompatibility, and local, minimally invasive injection of the IL-1ra-loaded microspheres could reduce inflammation, maintain the height of the intervertebral disc (IVD) and the water content of NP close to about 70 % in the sham group, and retain the integrated IVD structure. In summary, the GelMA-CS microspheres served as an effective loading platform for IL-1ra, eliminated inflammation through the controlled release of IL-1ra, and promoted ECM synthesis via CS to delay IVDD, thereby providing a promising intervention strategy for IVDD. The strategy of simultaneously overcoming the overactive inflammation and restoring the anabolic/catabolic balance of the extracellular matrix (ECM) in nucleus pulposus (NP) has shown great potential prospects for alleviating intervertebral disc degeneration (IVDD). From the perspective of clinical translation, this study developed chondroitin sulfate functionalized microspheres to act as the effective delivery platform of IL-1ra, a natural antagonist of interleukin-1β. The IL-1ra loading microspheres (GelMA-CS-IL-1ra) showed good biocompatibility, good injection with tissue retention, and synergistic effects of inhibiting the inflammatory response induced by lipopolysaccharide and promoting the secretion of ECM in NPCs. In vivo , they also showed the beneficial effect of reducing the inflammatory response, maintaining the height of the intervertebral disc and the water content of the NP, and preserving the integrity of the intervertebral disc structure after only one injection. All demonstrated that the GelMA-CS-IL-1ra microspheres would have great promise for the minimally invasive treatment of IVDD. [Display omitted] [ABSTRACT FROM AUTHOR]

Background. Intervertebral disc degeneration (IDD) is a major cause of low back pain. Sinapine thiocyanate (ST) has been reported to have a wide range of biological activities. However, the treatment of IDD with ST has not been studied. Objectives. To explore the role and mechanism of ST treatment in IDD. Materials and methods. Nucleus pulposus cells (NPCs) were induced using lipopolysaccharide (LPS), which was used as an in vitro model of IDD. Cell activity, oxidative stress-related indicators and protein expression were detected using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, enzyme-linked immunosorbent assay (ELISA) and western blot. Pyroptosis was evaluated with propidium iodide (PI)/Hoechst double staining and immunofluorescence for NOD-like receptor protein 3 (NLRP3), and pyroptosis-related proteins and inflammatory factors were measured with western blot and ELISA. The pathological changes of IDD were assessed with hematoxylin & eosin (H&E) and safranin-O staining. Results. Our results showed that ST alleviated LPS-induced degeneration of NPCs, as evidenced by reducing reactive oxygen species (ROS), malondialdehyde (MDA), matrix metalloproteinase-13 (MMP-13), a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5), and increasing collagen II and aggrecan expression. Moreover, ST repressed LPS-induced pyroptosis by inhibiting NLRP3, caspase-1 p20, interleukin (IL)-1β and IL-18. Further studies showed that ST did not restrain the activation of the JAK1/STAT3 signaling pathway induced by colivelin, or of the enhanced pyroptosis induced by polyphyllin VI. Sinapine thiocyanate alleviated IDD in vivo and suppressed NLRP3-mediated pyroptosis and the JAK1/STAT3 signaling pathway. Conclusions. Sinapine thiocyanate could alleviate IDD, although this did not include a reduction in NLRP3- mediated pyroptosis and inactivation of the JAK1/STAT3 signaling pathway, thus potentially being a candidate drug for IDD treatment. [ABSTRACT FROM AUTHOR]

The intervertebral disc (IVD) is the largest avascular organ of the human body and plays a fundamental role in providing the spine with its unique structural and biomechanical functions. The inner part of the IVD contains the nucleus pulposus (NP), a gel-like tissue characterized by a high content of type II collagen and proteoglycans, which is crucial for the disc's load-bearing and shock-absorbing properties. With aging and IVD degeneration (IDD), the NP gradually loses its physiological characteristics, leading to low back pain and additional sequelae. In contrast to surrounding spinal tissues, the NP presents a distinctive embryonic development since it directly derives from the notochord. This review aims to explore the embryology of the NP, emphasizing the pivotal roles of key transcription factors, which guide the differentiation and maintenance of the NP cellular components from the notochord and surrounding sclerotome. Through an understanding of NP development, we sought to investigate the implications of the critical developmental aspects in IVD-related pathologies, such as IDD and the rare malignant chordomas. Moreover, this review discusses the therapeutic strategies targeting these pathways, including the novel regenerative approaches leveraging insights from NP development and embryology to potentially guide future treatments. [ABSTRACT FROM AUTHOR]

Purpose: One-hole Split Endoscopy (OSE) is a newer surgical modality that can be applied to posterior cervical foraminotomy (PCF), lumbar discectomy, laminectomy, and decompression. It incorporates intervertebral foraminotomy, open surgery, and other lumboendoscopic techniques with a wide observation field, free space, and compatibility with various spinal surgical techniques and instruments. This study investigated the clinical efficacy of minimally invasive posterior cervical nucleus pulposus removal for cervical spondylotic radiculopathy (CSR) by OSE-Keyhole technique. Patients and Methods: This was a retrospective study of 63 patients treated with OSE keyhole treatment for CSR between May 2021 and September 2023 at Qilu Hospital of Shandong University, Qilu Hospital of Shandong University (Qingdao, China), and Second Hospital of Shandong University, respectively. Clinical outcomes included patients' preoperative and postoperative visual analogue scale (VAS) - arm and neck, Japanese Orthopaedic Association Assessment Treatment Score (JOA) - cervical spine, which were collected at baseline, two days postoperatively, one month postoperatively, and three months postoperatively after the last follow-up visit for evaluation, and perioperative indicators, including intraoperative bleeding, length of hospital stay, postoperative complications, and reoperations, which were also collected. Results: Statistical analyses were performed for the baseline data and follow-up results of 63 patients. Compared to the preoperative baseline values, the follow-up results two days, one month and three months after surgery showed significant improvements in vas-arm, neck and JOA scores in the operated patients (P< 0.05) as well as a reduction in all perioperative-related indices. Conclusion: In the treatment of cervical pain and disability due to radiculopathy, OSE keyhole removal of the posterior cervical nucleus pulposus is a better clinical option as it is less invasive and recovers better postoperatively. [ABSTRACT FROM AUTHOR]

Background: While growth factors have the potential to halt degeneration and decrease inflammation in animal models, the literature investigating the effect of dosage on human cells is lacking. Moreover, despite the completion of clinical trials using growth differentiation factor‐5 (GDF‐5), no results have been publicly released. Aims: The overall objective was to quantitatively assess the effect of three clinically relevant concentrations of GDF‐5 (0.25, 1, and 2 mg) as a therapeutic for disc regeneration. Materials and methods: Firstly, this work experimentally determined the effects of GDF‐5 concentration on the metabolic and matrix synthesis rates of human nucleus pulposus (NP) cells. Secondly, in silico modeling was employed to predict the subsequent regenerative effect of different GDF‐5 treatments (± cells). Results: This study suggests a trend of increased matrix synthesis with 0.25 and 1 mg of GDF‐5. However, 2 mg of GDF‐5 significantly upregulates oxygen consumption. Despite this, in silico models highlight the potential of growth factors in promoting matrix synthesis compared to cell‐only treatments, without significantly perturbing the nutrient microenvironment. Discussion: This work elucidates the potential of GDF‐5 on human NP cells. Although the results did not reveal statistical differences across all doses, the variability and response among donors is an interesting finding. It highlights the complexity of human response to biological treatments and reinforces the need for further human research and personalized approaches. Furthermore, this study raises a crucial question about whether these potential biologics are more regenerative in nature or better suited as prophylactic therapies for younger patient groups. Conclusion: Biological agents exhibit unique characteristics and features, demanding tailored development strategies and individualized assessments rather than a one‐size‐fits‐all approach. Therefore, the journey to realizing the full potential of biological therapies is long and costly. Nonetheless, it holds the promise of revolutionizing spinal healthcare and improving the quality of life for patients suffering from discogenic back pain. [ABSTRACT FROM AUTHOR]

Background: Tissue cryopreservation requires saturation of the structure with cryoprotectants (CPAs) that are also toxic to cells within a short timeframe unless frozen. The race between CPA delivery and cell death is the main barrier to realizing transplantation banks that can indefinitely preserve tissues and organs. Unrealistic cost and urgency leaves less life‐threatening ailments unable to capitalize on traditional organ transplantation systems that immediately match and transport unfrozen organs. For instance, human intervertebral discs (IVD) could be transplanted to treat back pain or used as ex vivo models for studying regenerative therapies, but both face logistical hurdles in organ acquisition and transport. Here we aimed to overcome those challenges by cryopreserving intact IVDs using compressive loading and swelling to accelerate CPA delivery. Methods: CPAs were tested on bovine nucleus pulposus cells to determine the least cytotoxic solution. Capitalizing on our CPAs Computed Tomography (CT) contrast enhancement, we imaged and quantified saturation time in intact bovine IVDs under different conditions in a bioreactor. Finally, the entire protocol was tested, including 1 week of frozen storage, to confirm tissue viability in multiple IVD regions after thawing. Results: Results showed cryopreserving medium containing dimethyl sulfoxide and ethylene glycol gave over 7.5 h before cytotoxicity. While non‐loaded IVDs required over 3 days to fully saturate, a dynamic loading protocol followed by CPA addition and free‐swelling decreased saturation time to <5 h. After cryopreserving IVDs for 1 week with the optimized CPA and permeation method, all IVD regions had 85% cell viability, not significantly different from fresh unfrozen controls. Conclusions: This study created a novel solution to a roadblock in IVD research and development. Using post‐compression swelling CPA can be delivered to an intact IVD over 20× more quickly than previous methods, enabling cryopreservation of the IVD with no detectable loss in cell viability. [ABSTRACT FROM AUTHOR]

Xinyu Yang,1,2 Qiaochu Li,1,2 Linbang Wang,3 Jiaxing Chen,1,2 Zhengxue Quan1,2 1Department of Orthopedics, the First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, People’s Republic of China; 2Orthopedic Laboratory of Chongqing Medical University, Chongqing, 400016, People’s Republic of China; 3Department of Orthopedics, Peking University Third Hospital, Beijing, 100191, People’s Republic of ChinaCorrespondence: Zhengxue Quan; Jiaxing Chen, Email quanzx18@126.com; cqykdxcjx@163.comPurpose: Ferroptosis is an underlying mechanism for various degenerative diseases, but its role in intervertebral disc degeneration remains elusive. This study aims to explore the key ferroptosis-related genes and its role in nucleus pulposus (NP) and annulus fibrosus (AF) degeneration.Methods: We analyzed the gene expression profiles of NP and AF from the Gene Expression Omnibus database. The ferroptosis-related differentially expressed genes (FRDEGs) in degenerated NP and AF were filtered, followed by GO and KEGG analysis. Feature FRDEGs were identified by the LASSO and SVM-RFE algorithms, and then Gene Set Enrichment Analysis (GSEA) and Gene Set Variation Analysis (GSVA) were conducted. Immune infiltration analysis was conducted by CIBERSORT algorithm. We established drug networks via the Drug–Gene Interaction Database and competitive endogenous RNA (ceRNA) networks via miRanda, miRDB, and TargetScan database. The expression levels of the feature FRDEGs were assessed by the validation sets, single-cell RNA-seq, and experimental verification.Results: A total of 15 and 18 FRDEGs were obtained for NP and AF, respectively. GO and KEGG analysis revealed their implication in oxidative stress. Four (AKR1C1, AKR1C3, MUC1, ENPP2) and five (SCP2, ABCC1, KLF2, IDO1, CREB3) feature genes were identified for NP and AF, respectively. The GSEA and GSVA analysis showed that these feature genes were enriched in lots of biological functions, including immune response. CREB3 in degenerated AF was negatively correlated with Eosinophils via CIBERSORT algorithm. The drugs and ceRNAs targeting CREB3 and MUC1 were identified. Experimental verification and single-cell RNA-seq analysis revealed that MUC1 and CREB3 were downregulated in degenerated NP and AF, respectively.Conclusion: MUC1 and CREB3 were considered novel biomarkers for NP and AF ferroptosis, respectively. Drug and ceRNA networks were constructed for future drug development and investigation of new mechanisms of ferroptosis.Keywords: bioinformatics analysis, experimental verification, ferroptosis, nucleus pulposus, annulus fibrosus, single-cell RNA-seq

Abstract The nucleus pulposus (NP) plays a vital role in intervertebral disc degeneration (IVDD). Previous studies have revealed cellular heterogeneity in NP tissue during IVDD progression. However, the cellular and molecular alterations of diverse cell clusters during IVDD remain to be fully elucidated. NP tissues were isolated from patients with different grades of IVDD undergoing discectomy, and then subjected to single-cell RNA sequencing (scRNA-seq). Cell subsets were identified based on unbiased clustering of gene expression profiles. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to determine the molecular features of diverse cell clusters. Monocle analysis was used to illustrate the differentiation trajectories of chondrocytes. Additionally, CellPhoneDB analysis revealed potential interactions between chondrocytes and other cells during IVDD. Based on the expression profiles of 47,610 individual cells, eight putative clusters including chondrocytes, endothelial cells, fibroblasts, macrophages, mural cells, osteoclasts, proliferating stromal cells and T cells were identified. The chondrocyte cluster was classified into three subsets, C1-C3, which were associated with stress-resistance, fibrosis and inflammatory responses, respectively. Pseudo-time trajectories suggested that chondrocytes gradually differentiated into fibroblasts during IVDD. Immune cells including cDC2s, macrophages and monocytes were identified. Further analysis showed that chondrocytes might communicate with immune cells via the MIF, TNFSF9, SPP1 and CCL4L2 signaling pathways. In addition, we found that invading endothelial cells might interact with chondrocytes through the COL4A1, CXCL12, VEGFA and SEMA3E signaling pathways. Our results reveal the cellular complexity and phenotypic characteristics of NP tissues at single-cell resolution, which will contribute to the in-depth investigation of preventative and regenerative strategies for IVDD.

Microvascular changes are considered key factors in the process of intervertebral disk degeneration (IDD). Microvascular invasion and growth into the nucleus pulposus (NP) and cartilaginous endplates are unfavorable factors that trigger IDD. In contrast, the rich distribution of microvessels in the bony endplates and outer layers of the annulus fibrosus is an important safeguard for the nutrient supply and metabolism of the intervertebral disk (IVD). In particular, the adequate supply of microvessels in the bony endplates is the main source of the nutritional supply for the entire IVD. Microvessels can affect the progression of IDD through a variety of pathways. Many studies have explored the effects of microvessel alterations in the NP, annulus fibrosus, cartilaginous endplates, and bony endplates on the local microenvironment through inflammation, apoptosis, and senescence. Studies also elucidated the important roles of microvessel alterations in the process of IDD, as well as conducted in‐depth explorations of cytokines and biologics that can inhibit or promote the ingrowth of microvessels. Therefore, the present manuscript reviews the published literature on the effects of microvascular changes on IVD to summarize the roles of microvessels in IVD and elaborate on the mechanisms of action that promote or inhibit de novo microvessel formation in IVD.

Zhaobai Lao,1,&ast; Xuliang Fang,1,&ast; Shuchao Shen,1,&ast; Yuliang Zhang,2,&ast; Xin Chen,1 Helou Zhang,1 Yishan Bian,1 Chengcong Zhou,1 Ronghua Bao,2 Taotao Xu,3 Hongting Jin,1 Fangda Fu,1 Chengliang Wu,1 Changfeng Hu,4 Hongfeng Ruan1 1Institute of Orthopaedics and Traumatology, The First Affiliated Hospital of Zhejiang Chinese Medical University (Zhejiang Provincial Hospital of Traditional Chinese Medicine), Hangzhou, Zhejiang, 310053, People’s Republic of China; 2Hangzhou Fuyang Hospital of TCM Orthopedics and Traumatology, Hangzhou, Zhejiang, 311400, People’s Republic of China; 3Department of Orthopaedics, The First Affiliated Hospital of Zhejiang Chinese Medical University (Zhejiang Provincial Hospital of Traditional Chinese Medicine), Hangzhou, Zhejiang, 310053, People’s Republic of China; 4College of Basic Medical Sciences, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Changfeng Hu, College of Basic Medical Sciences, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, People’s Republic of China, Email zhudianzhuifeng@163.com Hongfeng Ruan, Institute of Orthopaedics and Traumatology, The First Affiliated Hospital of Zhejiang Chinese Medical University, 548 Binwen Road, Hangzhou, 310053, People’s Republic of China, Email rhf@zcmu.edu.cnPurpose: Systemic lupus erythematosus (SLE) is an autoimmune disorder marked by immune system dysregulation and autoantibodies production, causing widespread inflammation and damage across various body systems. Despite the prevalent back pain in SLE patients, the link between SLE and intervertebral disc (IVD) degeneration, a primary contributor to back pain, remains inadequately understood. This study explored the impact of SLE on IVD degeneration using the MRL/lpr mouse model, which effectively replicates human SLE manifestations.Methods: The study utilized MRL/lpr mice to investigate the effects of SLE on IVD degeneration. The mice were evaluated for typical SLE phenotypes and indicators of IVD degeneration, including IVD height, IVD score, tissue integrity, extracellular matrix degradation, and apoptosis of IVD cells. Additionally, the study examined nucleus pulposus (NP) pyroptosis and inflammatory cytokine secretion. Mechanistic analysis focused on the antioxidant pathway, specifically the expression levels of NRF2, HO-1, KEAP1, and the phosphorylation levels of p65.Results: MRL/lpr mice displayed typical SLE phenotypes and exacerbated profiles of IVD degeneration, including reduced IVD height, lower IVD score, significant IVD tissue impairment, extracellular matrix degradation, and increased apoptosis of IVD cells. Notably, SLE stimulated NP pyroptosis and excessive secretion of inflammatory cytokines. Mechanistic analysis indicated that the progression of SLE impedes the antioxidant pathway by downregulating NRF2 and HO-1 expression, upregulating KEAP1, and enhancing phosphorylation levels of p65.Conclusion: Our findings highlight the mechanistic link between SLE and IVD degeneration, suggesting potential therapeutic targets for mitigating back pain in SLE patients.Keywords: systemic lupus erythematosus, intervertebral disc degeneration, nucleus pulposus, pyroptosis, NRF2/KEAP1/NF-κB pathway

Abstract Intervertebral disc degeneration (IVDD) is a prevalent musculoskeletal disorder that involves the excessive accumulation of reactive oxygen species (ROS), resulting in mitochondrial dysfunction and matrix metabolism imbalance in nucleus pulposus cells (NPCs). Selenium, an indispensable trace element, plays a crucial role in maintaining mitochondrial redox homeostasis by being incorporated into antioxidant selenoproteins as selenocysteine. In this study, we employed a straightforward synthesis method to produce selenium nanoparticles (SeNPs) with consistent size and distribution, and evaluated their potential protective effects in ameliorating IVDD. In a simulated inflammatory environment induced by interleukin-1beta (IL-1β) in vitro, SeNPs demonstrated a protective effect on the matrix synthesis capacity of NPCs through the up-regulation of aggrecan and type II collagen, while concurrently suppressing the expression of matrix degradation enzymes including MMP13 and ADAMTS5. Additionally, SeNPs preserved mitochondrial integrity and restored impaired mitochondrial energy metabolism by activating glutathione peroxidase1 (GPX1) to rebalance redox homeostasis. In a rat lumbar disc model induced by puncture, the local administration of SeNPs preserved the hydration of nucleus pulposus tissue, promoted matrix deposition, and effectively mitigated the progression of IVDD. Our results indicate that the enhancement of GPX1 by SeNPs may offer a promising therapeutic approach for IVDD by restoring mitochondrial function and redox homeostasis.

BACKGROUND: Scholars at home and abroad consider New Zealand rabbits to be an ideal model animal because of the similar anatomical morphology of the lumbar spine to that of the human lumbar spine. There is a lack of systematic comparison of different ways to establish rabbit intervertebral disc degeneration models under X-ray guidance. OBJECTIVE: To establish a rabbit model of lumbar disc degeneration using X-ray guided acupuncture, end-plate injection and combined method, and to compare the modeling effects of these three methods. METHODS: Eighteen 6-month-old New Zealand white rabbits were randomly selected and divided into four groups: acupuncture group, endplate injection group, combined group and blank control group. In the acupuncture group, three consecutive segments of the intervertebral discs (L2/3, L3/4, L4/5) were needled and modeled; in the endplate injection group, 50 μL of anhydrous ethanol was injected at a single point on the endplates of the three consecutive segmental discs; in the combined group, three consecutive segmental intervertebral discs were needled and injected with 50 μL of anhydrous ethanol at four azimuthal points on the endplates of the corresponding segmental discs; and the blank control group received no interventions. X-ray examination was performed to measure the disc height index at 2, 4, and 8 weeks after surgery. The intervertebral disc tissues were then taken for anatomical observation and pathological examination. RESULTS AND CONCLUSION: (1) Anatomical examination showed that fibrous annulus rupture, nucleus pulposus degeneration, and total disc structure disorder were the main manifestation in the acupuncture group, endplate injection group, and combined group, respectively. (2) X-ray examination showed that the disc height index showed the most obvious reduction in the acupuncture group at 2 weeks after operation, significant reductions in the endplate injection group at 2 and 4 weeks after operation, and significant reductions in the combined group at 2, 4, and 8 weeks after operation. (3) Pathological examination showed that the fibrous ring structure was damaged and the inner annulus fibrosus protruded inward in the acupuncture group; endplate fissure, disordered arrangement and nucleus loss were observed in the endplate injection group; total disc structure disorder with the nucleus pulposus losing water and shrinking and no obvious border with the broken annulus fibrosus was found in the combined group. To conclude, acupuncture, endplate injection and the modified endplate injection method can establish the rabbit intervertebral disc degeneration model. Compared with the single method, the modified endplate injection method can greatly accelerate and aggravate the degeneration of the intervertebral disc, and can effectively shorten the experiment period. [ABSTRACT FROM AUTHOR]

• Effects of osmotic and hydrostatic pressure (HP) and confinement on nucleus pulposus (NP) cells were investigated. • Confinement and constant HP counteract the swelling of NP cells and help retain sulfated glycosaminoglycan. • Aggrecan core protein gene is significantly upregulated under confinement and constant HP. • NPs' metabolic turnover is regulated by the configuration of actin and fibrillar extracellular matrices under HP. • These findings will assist understanding stress loading in the NP and replicate the native environment ex vivo for therapy. Spinal movement in both upright and recumbent positions generates changes in physicochemical stresses including hydrostatic pressure (HP), deviatoric stress, and confinement within the intradiscal compartment. The nucleus pulposus (NP) of the intervertebral disc is composed of highly negatively charged extracellular matrix (ECM), which increases osmotic pressure (OP) and generates tissue swelling. In pursuing regenerative therapies for intervertebral disc degeneration, the effects of HP on the cellular responses of NP cells and the ECM environment remain incompletely understood. We hypothesized that anabolic turnover of ECM in NP tissue is maintained under HP and confinement. We first clarified the effects of the relationships among HP, OP, and confinement on swelling NP explants isolated from bovine caudal intervertebral discs over 12 h. We found that the application of confinement and constant HP significantly inhibits the free swelling of NP (p < 0.01) and helps retain the sulfated glycosaminoglycan. Since confinement and HP inhibited swelling, we incubated confined NPs under HP in high-osmolality medium mimicking ECM-associated OP for 7 days and demonstrated the effects of HP on metabolic turnover of ECM molecules in NP cells. The aggrecan core protein gene was significantly upregulated under confinement and constant HP compared to confinement and no HP (p < 0.01). We also found that confinement and constant HP helped to significantly retain smaller cell area (p < 0.01) and significantly prevent the severing of actin filaments compared to no confinement and HP (p < 0.01). Thus, we suggest that NP's metabolic turnover and cellular responses are regulated by the configuration of intracellular actin and fibrillar ECMs under HP. [ABSTRACT FROM AUTHOR]