Nucleus Pulposus Tissue Research Articles

Single-cell sequencing reveals cellular heterogeneity of nucleus pulposus in intervertebral disc degeneration

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.

The muscle-intervertebral disc interaction mediated by L-BAIBA modulates extracellular matrix homeostasis and PANoptosis in nucleus pulposus cells.

Upon engaging in physical activity, skeletal muscle synthesizes myokines, which not only facilitate crosstalk with various organs, including the brain, adipose tissue, bone, liver, gut, pancreas, and skin but also promote intramuscular signaling. Crosstalk is vital for maintaining various physiological processes. However, the specific interactions between skeletal muscle and intervertebral discs remain largely unexplored. β-Aminoisobutyric acid (BAIBA), an exercise-induced myokine and a metabolite of branched-chain amino acids in skeletal muscle, has emerged as a key player in this context. Our study demonstrated that exercise significantly elevates BAIBA levels in skeletal muscle, plasma, and nucleus pulposus (NP) tissues. Moreover, exercise enhances extracellular matrix (ECM) synthesis in NP tissues and upregulates L-BAIBA synthase in skeletal muscle. Both in vivo and in vitro evidence revealed that L-BAIBA impedes PANoptosis and ECM degradation in NP cells by activating the AMPK/NF-κB signaling pathway. These findings suggest that exercise, coupled with the resulting increase in L-BAIBA, may serve as an effective intervention to decelerate the progression of intervertebral disc degeneration (IDD). Consequently, L-BAIBA, which originates from skeletal muscle, is a promising new therapeutic approach for IDD.

PRDM1 promotes nucleus pulposus cell pyroptosis leading to intervertebral disc degeneration via activating CASP1 transcription.

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.

Selenium nanoparticles ameliorate lumbar disc degeneration by restoring GPX1-mediated redox homeostasis and mitochondrial function of nucleus pulposus cells

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.

Inactivation of Tnf-α/Tnfr signaling attenuates progression of intervertebral disc degeneration in mice.

Intervertebral disc degeneration (IVDD) is a major cause of low back pain (LBP), worsened by chronic inflammatory processes associated with aging. Tumor necrosis factor alpha (Tnf-α) and its receptors, Tnf receptor type 1 (Tnfr1) and Tnf receptor type 2 (Tnfr2), are upregulated in IVDD. However, its pathologic mechanisms remain poorly defined. To investigate the role of Tnfr in IVDD, we generated global Tnfr1/2 double knockout (KO) mice and age-matched control C57BL/6 male mice, and analyzed intervertebral disc (IVD)-related phenotypes of both genotypes under physiological conditions, aging, and lumbar spine instability (LSI) model through histological and immunofluorescence analyses and μCT imaging. Expression levels of key extracellular matrix (ECM) proteins in aged and LSI mice, especially markers of cell proliferation and apoptosis, were evaluated in aged (21-month-old) mice. At 4 months, KO and control mice showed no marked differences of IVDD-related parameters. However, at 21 months of age, the loss of Tnfr expression significantly alleviated IVDD-like phenotypes, including a significant increase in height of the nucleus pulposus (NPs) and reductions of endplates (EPs) porosity and histopathological scores, when compared to controls. Tnfr deficiency promoted anabolic metabolism of the ECM proteins and suppressed ECM catabolism. Tnfr loss largely inhibited hypertrophic differentiation, and, in the meantime, suppressed cell apoptosis and cellular senescence in the annulus fibrosis, NP, and EP tissues without affecting cell proliferation. Similar results were observed in the LSI model, where Tnfr deficiency significantly alleviated IVDD and enhanced ECM anabolic metabolism while suppressing catabolism. The deletion of Tnfr mitigates age-related and LSI-induced IVDD, as evidenced by preserved IVD structure, and improved ECM integrity. These findings suggest a crucial role of Tnf-α/Tnfr signaling in IVDD pathogenesis in mice. Targeting this pathway may be a novel strategy for IVDD prevention and treatment.

Effects of hydrostatic pressure, osmotic pressure, and confinement on extracellular matrix associated responses in the nucleus pulposus cells ex vivo

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 hours. 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.

Facile fabrication of nano-bioactive glass functionalized blended hydrogel with nucleus pulposus-derived MSCs to improve regeneration potential in treatment of disc degeneration by in vivo rat model

Orthopaedic medicine often treats intervertebral disc degeneration (IVDD), which is caused by nucleus pulposus (NP) tissue damage and mechanical stress. Bioactive glasses (BGs), widely used for bone regeneration, can incorporate therapeutic ions into their network. Manganese (Mn) activates human osteoblast integrins, proliferation, and spreading. The CMnBGNPs-NPMSCs are carboxymethyl cellulose hydrogels functionalized with MnBGsNPs and NP-derived mesenchymal stem cells to treat IVDD. To ensure stability and biocompatibility of CMnBGNPs-NPMSCs were characterized for rheological properties like gelation time and swelling ratio. Gene expression analysis of PAX1, FOXF1, CA12, HBB, and OVOS2 via qRT-PCR further assessed the hydrogel's characteristics. Rat models with induced IVDD had hydrogel-MSC composite injected into their intervertebral discs for in vivo studies. Histological examination, immunohistochemical staining for inflammation and disc regeneration markers, and disc height assessments assessed therapeutic efficacy. CMnBGNPs-NPMSCs show promising results for IVDD treatment, offering a novel therapeutic strategy with clinical implications for degenerative disc diseases.

Arthroscopic-assisted uni-portal ligament flavum sparing bone anchoring annular suture technique for lumbar disc herniation: A case report and literature review.

Lumbar disc herniation (LDH) manifests in diverse forms. If the nucleus pulposus or endplate tissues protrudes, the location of annular tears also varies, which poses various challenges for the annular suture technique. Tears at the annular attachment area at the edge of the vertebral body (cephalad or caudad) are considered a prohibitively challenging area for annular suturing. A 37-year-old woman presented with a gradual onset of symptoms, experiencing leg pain and numbness over the left leg for 1 year before presentation. The pain radiated to the left S1 dermatome. Despite undergoing continuous medical therapy for more than 6 months, her symptoms showed no improvement. The strength of the left plantar flexion in the ankle and great toe was rated at 4 out of 5. The straight leg-raising and strengthening tests were positive for the left sides. Lumbar computed tomography and magnetic resonance imaging revealed left-sided disc herniation at the L5-S1 level, and nerve root compression, confirming the diagnosis of LDH. The preoperative impression was LDH, intraoperative confirmation of a tear in the annular attachment area at the vertebral body edge. This patient was treated with an arthroscopic-assisted uniportal spinal surgery (AUSS) technique focusing on ligament flavum (LF) preservation, protruding nucleus pulposus removal, nerve root decompression, and vertebral edge tear was then sutured using a bone anchoring annular suture with the Smile suture device. This technique was performed successfully in a patient with LDH. Significant improvements were observed in postoperative pain and numbness, Visual Analog Scale, and Japanese Orthopaedic Association scores. No postoperative instability or complications were observed, with computed tomography and magnetic resonance imaging confirming complete decompression. To the best of our knowledge, this is the first used AUSS with LF preservation and bone anchoring annular suture technique for LDH. This case study demonstrates the AUSS combined with LF preservation and the bone anchoring annular suture technique provides favorable clinical and imaging outcomes and is a safe and effective technique for the treatment of LDH.

Fibulin-3 Regulates Tissue Inhibitor of Metalloproteinases 3 to Inhibit Senescence in Intervertebral Disc Nucleus Pulposus Cells

To investigate the effect of fibulin-3 on the senescence of intervertebral disc nucleus pulposus cells (NPCs) through the regulation of tissue inhibitor of metalloproteinases 3 (TIMP-3) expression and to elucidate the molecular mechanisms involved. 1). The nucleus pulposus tissues and imaging data of 37 patients who had undergone intervertebral disc surgery were collected. The degree of degeneration of the intervertebral discs were classified according to the Pfirrmann grading system. The senescence degree of NPCs was determined using senescence-associated β-galactosidase (SA-β-gal) staining. Fibulin-3 expression levels were determined using Western blot and ELISA. The relationship between fibulin-3 and disc degeneration and NPCs senescence was investigated. 2). Human intervertebral disc NPCs were cultured in vitro. The proliferation and senescence of NPC across continuous passage were observed via CCK-8 assay and SA-β-gal staining, respectively. Fibulin-3 expression levels and the expression of inflammatory cytokines and matrix metalloproteinases were assessed. Exogenous fibulin-3 was added to verify its effect on the proliferation and senescence of NPCs. 3). The effect of fibulin-3 on the apoptosis and proliferation of NPCs was verified through gene overexpression, which was used in combination with an apoptosis inhibitor for bidirectional verification. 4). Bioinformatics analysis was performed to explore the relationship between fibulin-3 and the TIMP family. Experiments overexpressing fibulin-3 and silencing the TIMP-3 gene were performed to verify their role in NPCs senescence. 1). The intervertebral disc degeneration samples from 37 patients were classified according to the Pfirrmann grading system. The higher the degeneration grade, the lower fibulin-3 expression. Spearman correlation analysis showed that the disc grade was negatively correlated with the NPC senescence grade (r=－0.87, P<0.001) and fibulin-3 expression (r=－0.79, P<0.001). 2). As the passage number of NPCs increased, fibulin-3 expression gradually decreased, cell proliferation ability weakened, and the expression of inflammatory cytokines and matrix metalloproteinases increased. After exogenous fibulin-3 was added, cell morphology and growth status were maintained, cell senescence was significantly inhibited, and the expression of inflammatory cytokines and matrix metalloproteinases was markedly reduced. 3). Gene overexpression experiments showed that fibulin-3 reduced NPC apoptosis and promoted cell proliferation, thereby inhibiting NPC senescence. 4). Bioinformatics analysis revealed a significant association between fibulin-3 and TIMP-3 of the TIMP family. Further experiments confirmed that overexpressing fibulin-3 enhanced TIMP-3 expression, while silencing the TIMP-3 gene significantly weakened the inhibitory effect of fibulin-3 on NPCs senescence. This indicates that, through regulating TIMP-3, fibulin-3 inhibits the activity of matrix metalloproteinases, affects the synthesis and degradation of the extracellular matrix, and ultimately inhibits NPCs senescence. This study demonstrates that fibulin-3 plays a crucial role in inhibiting the senescence of intervertebral disc NPCs by regulating TIMP-3. The specific mechanisms involved are as follows, fibulin-3 upregulates TIMP-3 expression, inhibits matrix metalloproteinase activity, and reduces extracellular matrix degradation, thereby promoting extracellular matrix synthesis. Additionally, fibulin-3 inhibits NPCs senescence by reducing apoptosis and promoting cell proliferation. Therefore, fibulin-3 and TIMP-3 have potential therapeutic significance in maintaining intervertebral disc health and delaying degeneration.

A novel spherical GelMA-HAMA hydrogel encapsulating APET×2 polypeptide and CFIm25-targeting sgRNA for immune microenvironment modulation and nucleus pulposus regeneration in intervertebral discs

MethodsSingle-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.ResultsCFIm25 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).ConclusionThe 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.Graphical Molecular mechanism of GCA targeting CFIm25 in NP cells to promote regeneration of degenerated intervertebral disc NP

Glucose deprivation-induced disulfidptosis in human nucleus pulposus cells: a novel pathological mechanism of intervertebral disc degeneration

BackgroundLimited 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.MethodsRNA-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.ResultsWe 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.ConclusionsWe 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.Graphical

Melatonin mitigates matrix stiffness-induced intervertebral disk degeneration by inhibiting reactive oxygen species and melatonin receptors mediated PI3K/AKT/NF-κB pathway.

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.

Bone Marrow Mesenchymal Stem Cell-Derived Exosomes Alleviate Nuclear Pulposus Cells Degeneration Through the miR-145a-5p/USP31/HIF-1α Signaling Pathway.

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.

Effect of electroacupuncture on expression of autophagy-related proteins in nucleus pulposus of cervical spondylosis rabbits.

To observe the effects of electroacupuncture (EA) on the morphological changes of intervertebral disc tissues, apoptosis of nucleus pulposus cells, and the protein expression of Unc-51 like autophagy-activated kinase 1 (ULK1), homologous series of yeast Atg6 (Beclin1), and light chain protease complication 3 type (LC3) in nucleus pulposus tissue of cervical spondylosis rabbits, so as to explore the role of cellular autophagy in EA treatment of cervical spondylosis. A total of 24 New Zealand white rabbits were randomly divided into blank, model and EA groups, with 8 rabbits in each group. In the EA group, both sides of the cervical (C)3-C6 "Jiaji" (EX-B2) were stimulated by EA (2 Hz/100 Hz, 1 mA) for 25 min, once daily for 5 days in a course, with a 2-day interval between courses, totaling 4 treatment courses. X-ray was used to assess cervical spine radiographic changes and evaluate radiographic scores；transmission electron microscopy was used to observe ultrastructural changes in nucleus pulposus cells；HE staining was used to observe morphological changes of intervertebral disc tissues and conduct pathological scoring；TUNEL staining was used to observe apoptosis rate of nucleus pulposus cells；Western blot was performed to detect protein expression levels of ULK1, Beclin1, and LC3 in nucleus pulposus tissue. Compared with the blank group, rabbits in the model group showed significantly higher cervical spine radiographic scores (P<0.01), higher pathological scores of intervertebral disc tissues (P<0.05), increased apoptosis rate of nucleus pulposus cells (P<0.01), and decreased expression levels of ULK1, Beclin1, and LC3Ⅱ proteins in nucleus pulposus tissue (P<0.05). Compared with the model group, the EA group showed significantly lower pathological scores of intervertebral discs (P<0.05), lower apoptosis rate of nucleus pulposus cells (P<0.01), and higher protein expression levels of ULK1, Beclin1, and LC3Ⅱ in nucleus pulposus tissue (P<0.01). Rabbits in the blank control group exhibited generally normal organelle structures in nucleus pulposus tissues with few autophagic vacuoles, indicative of early stages of autophagy；while those in the model group showed disrupted organelle structures with cytoplasmic condensation and those in the EA group exhibited autophagosomes with double-membrane structures in nucleus pulposus tissues. EA promotes the expression of ULK1, Beclin1, and LC3Ⅱ proteins in nucleus pulposus tissues, reduces apoptosis of nucleus pulposus cells, and improves intervertebral disc degeneration.

Inhibition of OLR1 reduces SASP of nucleus pulposus cells by targeting autophagy-GATA4 axis.

Targeting cellular senescence and Senescence Associated Secretory Phenotype (SASP) through autophagy has emerged as a promising intervertebral disc (IVD) degeneration (IDD) treatment strategy in recent years. This study aimed to clarify the role and mechanism of autophagy in preventing IVD SASP. Methods involved in vitro experiments with nucleus pulposus (NP) tissues from normal and IDD patients, as well as an in vivo IDD animal model. GATA4's regulatory role in SASP was validated both in vitro and in vivo, while autophagy modulators were employed to assess their impact on GATA4 and SASP. Transcriptomic sequencing identified Oxidized low-density lipoprotein receptor 1 (OLR1) as a key regulator of autophagy and GATA4. A series of experiments manipulated OLR1 expression to investigate associated effects. Results demonstrated significantly increased senescent NP cells (NPCs) and compromised autophagy in IDD patients and animal models, with SASP closely linked to IDD progression. The aged disc milieu impeded autophagic GATA4 degradation, leading to elevated SASP expression in senescent NPCs. Restoring autophagy reversed senescence by degrading GATA4, hence disrupting the SASP cascade. Moreover, OLR1 was identified for its regulation of autophagy and GATA4 in senescent NPCs. Silencing OLR1 enhanced autophagic activity, suppressing GATA4-induced senescence and SASP expression in senescent NPCs. In conclusion, OLR1 was found to control autophagy-GATA4 and SASP, with targeted OLR1 inhibition holding promise in alleviating GATA4-induced senescence and SASP expression while delaying extracellular matrix degradation, offering a novel therapeutic approach for IDD management.

IL-32 aggravates metabolic disturbance in human nucleus pulposus cells by activating FAT4-mediated Hippo/YAP signaling

Extracellular matrix (ECM) metabolism disorders in the inflammatory microenvironment play a key role in the pathogenesis of intervertebral disc degeneration (IDD). Interleukin-32 (IL-32) has been reported to be involved in the progression of various inflammatory diseases; however, it remains unclear whether it participates in the matrix metabolism of nucleus pulposus (NP) cells. Therefore, this study aimed to investigate the mechanism of IL-32 on regulating the ECM metabolism in the inflammatory microenvironment. RNA-seq was used to identify aberrantly expressed genes in NP cells in the inflammatory microenvironment. Western blotting, real-time quantitative PCR, immunohistochemistry and immunofluorescence analysis were performed to measure the expression of IL-32 and metabolic markers in human NP tissues or NP cells treated with or without tumor necrosis factor-α (TNF-α). In vivo, an adeno-associated virus overexpressing IL-32 was injected into the caudal intervertebral discs of rats to assess its effect on IDD. Proteins interacting with IL-32 were identified via immunoprecipitation and mass spectrometry. Lentivirus overexpressing IL-32 or knocking down Fat atypical cadherin 4 (FAT4), yes-associated protein (YAP) inhibitor-Verteporfin (VP) were used to treat human NP cells, to explore the pathogenesis of IL-32. Hippo/YAP signaling activity was verified in human NP tissues. IL-32 expression was significantly upregulated in degenerative NP tissues, as indicated in the clinical samples. Furthermore, IL-32 was remarkably overexpressed in TNF-α-induced degenerative NP cells. IL-32 overexpression induced IDD progression in the rat model. Mechanistically, the elevation of IL-32 in the inflammatory microenvironment enhanced its interactions with FAT4 and mammalian sterile 20-like kinase1/2 (MST1/2) proteins, prompting MST1/2 phosphorylation, and activating the Hippo/YAP signaling pathway, causing matrix metabolism disorder in NP cells. Our results suggest that IL-32 mediates matrix metabolism disorders in NP cells in the inflammatory micro-environment via the FAT4/MST/YAP axis, providing a theoretical basis for the precise treatment of IDD.

Enzymatic Digestion of the Intervertebral Disc Alters Intradiscal Injection and Leakage Mechanics.

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), 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.

The Different Influence of Cutibacterium acnes and Staphylococcus epidermidis in the Lumbar Disc : An in Vivo Study in Rabbits.

Animal laboratory study. This study investigated the effects of Cutibacteriumacnes and Staphylococcusepidermidis on the lumbar discs of rabbits, as well as the outcomes of combined infection. Many studies have indicated that bacterial infections are associated with lumbar disc degeneration (LDD). The most commonly cultured bacteria from disc tissues are C. acnes and S. epidermidis . New Zealand white rabbits (n=40) were randomly divided into control, C. acnes , S. epidermidis , and C. acnes plus S. epidermidis ( i.e. , combined) groups. All groups except the control were injected with 25μL of saline at L4-L5 and 25μL of bacteria (1×10 7 CFU/mL) at L5-L6. All injections were performed under x-ray guidance. Weight measurements, haematological evaluations, and magnetic resonance imaging were performed after 4, 8, and 12 weeks. Histological examination and gene expression detection were performed 12 weeks after surgery. Inflammatory factors in the blood and weight did not differ among the groups after 4, 8, and 12 weeks ( P >0.05). However, after 4 weeks, LDD occurred in the C. acnes group, and discitis occurred in the S. epidermidis and combined groups, all of which worsened after 8 weeks. After 12 weeks, the nucleus pulposus (NP) protruded and compressed the spinal cord in the C. acnes group, and tissue staining showed decreased NP tissue and cartilaginous endplate fracture. In the S. epidermidis and combined groups, the discitis was more confined, but tissue staining revealed a significant decrease in NP tissue, and loss of the normal disc structure. In the early stage of infection in rabbits, C. acnes caused LDD, and S. epidermidis caused discitis. Coinfection with C. acnes and S. epidermidis caused discitis but was more limited in scope than infection with S. epidermidis alone.

Unveiling the Therapeutic Potential of hUCMSC-Derived EVs in Intervertebral Disc Degeneration through MALAT1/miR-138-5p/SLC7A11 Coexpression Regulation.

Intervertebral disc degeneration (IVDD) is a prevalent chronic condition causing spinal pain and functional impairment. This study investigates the role of extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (hUCMSCs) in regulating IVDD. Using RNA-seq, we analyzed differential expressions of lncRNA and miRNA in nucleus pulposus tissues from various mouse groups. We identified key regulatory molecules, MALAT1 and miRNA-138-5p, which contribute to IVDD. Further experiments demonstrated that MALAT1 can up-regulate SLC7A11 expression by competitively binding to miR-138-5p, forming a MALAT1/miR-138-5p/SLC7A11 coexpression regulatory network. This study elucidates the molecular mechanism by which hUCMSC-derived EVs regulate IVDD and could help develop novel therapeutic strategies for treating this condition. Our findings demonstrate that hUCMSCs-EVs inhibit ferroptosis in nucleus pulposus cells, thereby improving IVDD. These results highlight the therapeutic potential of hUCMSCs-EVs in ameliorating the development of IVDD, offering significant scientific and clinical implications for new treatments.

Rescue of nucleus pulposus cells from an oxidative stress microenvironment via glutathione-derived carbon dots to alleviate intervertebral disc degeneration

The senescence of nucleus pulposus (NP) cells (NPCs), which is induced by the anomalous accumulation of reactive oxygen species (ROS), is a major cause of intervertebral disc degeneration (IVDD). In this research, glutathione-doped carbon dots (GSH-CDs), which are novel carbon dot antioxidant nanozymes, were successfully constructed to remove large amounts of ROS for the maintenance of NP tissue at the physical redox level. After significantly scavenging endogenous ROS via exerting antioxidant activities, such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity, GSH-CDs with good biocompatibility have been demonstrated to effectively improve mitochondrial dysfunction and rescue NPCs from senescence, catabolism, and inflammatory factors in vivo and in vitro. In vivo imaging data and histomorphological indicators, such as the disc height index (DHI) and Pfirrmann grade, demonstrated prominent improvements in the progression of IVDD after the topical application of GSH-CDs. In summary, this study investigated the GSH-CDs nanozyme, which possesses excellent potential to inhibit the senescence of NPCs with mitochondrial lesions induced by the excessive accumulation of ROS and improve the progression of IVDD, providing potential therapeutic options for clinical treatment.Graphical