Intraoperative capsule protection can reduce the potential risk of adjacent segment degeneration acceleration biomechanically: an in silico study.

BACKGROUND: The capsule of the zygapophyseal joint plays an important role in motion segmental stability maintenance. Iatrogenic capsule injury is a common phenomenon in posterior approach lumbar interbody fusion operations, but whether this procedure will cause a higher risk of adjacent segment degeneration acceleration biomechanically has yet to be identified. METHODS: Posterior lumbar interbody fusion (PLIF) with different grades of iatrogenic capsule injury was simulated in our calibrated and validated numerical model. By adjusting the cross-sectional area of the capsule, different grades of capsule injury were simulated. The stress distribution on the cranial motion segment was computed under different loading conditions to judge the potential risk of adjacent segment degeneration acceleration. RESULTS: Compared to the PLIF model with an intact capsule, a stepwise increase in the stress value on the cranial motion segment can be observed with a step decrease in capsule cross-sectional areas. Moreover, compared to the difference between models with intact and slightly injured capsules, the difference in stress values was more evident between models with slight and severe iatrogenic capsule injury. CONCLUSION: Intraoperative capsule protection can reduce the potential risk of adjacent segment degeneration acceleration biomechanically, and iatrogenic capsule damage on the cranial motion segment should be reduced to optimize patients' long-term prognosis.

Vitamin D delays intervertebral disc degeneration and improves bone quality in ovariectomized rats.

Known to be involved in bone-cartilage metabolism, Vitamin D (VD) may play a role in human's disc pathophysiology. Given that postmenopausal women are prone to suffer VD deficiency and intervertebral disc degeneration (IDD), this study is intended to investigate whether VD can delay IDD in ovariectomized rats by improving bone microstructure and antioxidant stress. Female Sprague-Dawley rats were randomly allocated into four groups: sham, oophorectomy (OVX)+VD deficiency (VDD), OVX, and OVX+VD supplementation (VDS). In vivo, after a 6-month intervention, imaging and pathology slice examinations showed that IDD induced by OVX was significantly alleviated in VDS and deteriorated by VDD. The expressions of aggrecan and Collagen II in intervertebral disc were reduced by OVX and VDD, and elevated by VDS. Compared with the OVX+VDD and OVX group vertebrae, OVX+VDS group vertebrae showed significantly improved endplate porosity and lumbar bone mineral density with increased percent bone volume and trabecular thickness. Furthermore, 1α,25(OH)2D3 restored the redox balance (total antioxidant capacity, ratio of oxidized glutathione/glutathione) in the disc. The cocultivation of 1α,25(OH)2D3 and nucleus pulposus cells (NPCs) was conducted to observe its potential ability to resist excessive oxidative stress damage induced by H2O2. In vitro experiments revealed that 1α,25(OH)2D3 reduced the senescence, apoptosis, and extracellular matrix degradation induced by H2O2 in NPCs. In conclusion, VDS exhibits protective effects in OVX-induced IDD, partly by regulating the redox balance and preserving the microstructure of endplate. This finding provides a new idea for the prevention and treatment of IDD.

Comparison of three methods for nucleus pulposus volume measurement in rabbit lumbar spines: a preclinical model for measurement of the effectiveness of prophylactic intervertebral disk fenestration in dogs.

OBJECTIVE: Compare 3 methods of nucleus pulposus (NP) volume measurement using the rabbit lumbar spines as a preclinical model to determine the effectiveness of prophylactic intervertebral disk fenestration in dogs. ANIMALS: Twelve 9-month-old, skeletally mature female entire New Zealand White rabbits weighing between 3.5 to 4.5 kg. METHODS: NP volume measurements of dissected rabbit lumber spines between L1 and L6 were made and compared using gross measurements, reconstructed MRI images, and water volumetry based on Archimedes' principle. Water volumetry was used as the true gold standard volume measurement in this study. RESULTS: The true volume (mean ± SD) of the nucleus pulposus NP as measured by water volumetry increased caudally from L1/L2 (16.26 ± 3.32 mm3) to L5/L6 (22.73 ± 6.09 mm3). Volume estimates made by MRI were significantly higher than those made using water volumetry at all sites (L1/L2 [P = .044], L2/L3 [P = .012], L3/L4 [P = .015], L4/L5 [P < .001], and L5/L6 [P < .001]). Gross measurements also significantly overestimated volume when compared to water volumetry at all sites; L1/L2 (P = .021), L2/L3 (P = .025), L3/L4 (P = .001), L4/L5 (P < .001), and L5/L6 (P < .001). MRI and gross volume estimates were significantly different at L4/L5 (P = .035) and L5/L6 (P = .030). CLINICAL RELEVANCE: The findings of this preclinical model might be relevant to veterinary surgeons who perform prophylactic fenestration for which there is no reliable method to determine the amount of NP to be removed. Preclinical ex vivo and in vivo fenestration studies with pre- and postoperative NP volume assessment are required.

Extracellular vesicles derived from mesenchymal stem cells confer protection against intervertebral disc degeneration through a microRNA-217-dependent mechanism.

OBJECTIVE: Extracellular vesicles released by mesenchymal stem cells (MSC-EVs) can be applied to alleviate intervertebral disc degeneration (IVDD) by curbing apoptosis of nucleus pulposus cells (NPCs). The current study aims to evaluate the effect of MSC-EVs on NPC apoptosis and IVDD and the related regulatory mechanisms involving microRNA (miR)-217. METHOD: Expression of miR-217 was examined in tumor necrosis factor-α (TNF-α)-induced NPCs and MSC-EVs, followed by identification in the relationship between miR-217, enhancer of zeste homolog 2 (EZH2) and forkhead box O-3 (FOXO3). After isolation of EVs from MSCs and subsequent co-culture with NPCs, we assessed effects of miR-217 on NPC viability, autophagy, senescence and apoptosis along with extracellular matrix (ECM) degradation. Further in vivo experiments were conducted in rat models of IVDD to substantiate the effect of miR-217 on IVDD. RESULTS: Poor miR-217 expression was found in TNF-α-induced NPCs, while high miR-217 expression was identified in MSC-EVs (P < 0.05). MSC-EVs transferred miR-217 to NPCs and increased its expression, thus attenuating NPC apoptosis and ECM degradation (elevated collagen II and aggrecan but reduced MMP13 and ADAMTS5) (P < 0.05). miR-217 targeted EZH2, and EZH2 bound to the FOXO3 promoter and consequently downregulated its expression. FOXO3 restrained NPC apoptosis and ECM degradation by stimulating cell autophagy (P < 0.05). Furthermore, in vivo experimental results confirmed the suppressive role of miR-217 shuttled by MSC-EVs in IVDD. CONCLUSION: Overall, the delivery of miR-217 may be a novel mechanism underlying the effect of MSC-EVs on NPC apoptosis and ECM degradation following IVDD.

Upregulation of SIRT1 by Evodiamine activates PI3K/AKT pathway and blocks intervertebral disc degeneration.

Intervertebral disc degeneration (IDD) is a major cause of a number of spinal diseases, resulting in serious public health problems. Evodiamine (Evo) is an indole quinazoline alkaloid extracted from Evodia rutaecarpa, which has antioxidant, anti­apoptosis and anti­inflammatory effects. The purpose of the present study was to investigate lipopolysaccharide (LPS)­induced IDD progression in human nucleus pulposus cells (NPCs) and its potential mechanism. The viability and apoptosis of NPCs were detected by Cell Counting Kit­8 (CCK­8) and TUNEL staining, respectively. Western blotting was used to detect the expression levels of proteins, cell transfection was performed to knockdown Sirtuin 1 (SIRT1) and the expression of tumor necrosis factor­alpha (TNF­α) and interleukin 6 (IL­6) was detected by enzyme­linked immunosorbent assay kits. The results showed that Evo effectively alleviated LPS­induced NPCs apoptosis and caspase­3 activation and Evo treatment reversed the upregulation of matrix metalloproteinase­13, as well as the downregulation of collagen type II (collagen II), Sry­type high­mobility­group box 9 and aggrecan and reduced the production of pro­inflammatory factors TNF­α and IL­6 in LPS­stimulated NPCs. In addition, treatment with Evo upregulated SIRT1 and activated the PI3K/Akt pathway, knockdown of SIRT1 inhibited the phosphorylation of Akt and PI3K in LPS­stimulated NPCs. In general, Evo upregulated SIRT1 and inhibited LPS­induced NPCs apoptosis, extracellular matrix degradation and inflammation by activating the PI3K/Akt pathway.

Vitamin D/VDR in the pathogenesis of intervertebral disc degeneration: Does autophagy play a role?

To date, the underlying mechanisms involved intervertebral disc degeneration (IDD) remain unclear, which has hindered the development of molecular biological therapy for IDD. Autophagy is vital for intracellular quality control and metabolic balance in intervertebral disc cells. Hence, autophagy homeostasis is important. Emerging evidence has implicated vitamin D (VD) and the vitamin D receptor (VDR) in IDD progression because of their effects on different autophagy steps. However, the results of clinical trials in which VD supplementation was assessed as a treatment for IDD are controversial. Furthermore, experimental studies on the interplay between VD/VDR and autophagy are still in their infancy. In view of the significance of the crosstalk between VD/VDR and autophagy components, this review focuses on the latest research on VD/VDR modulation in autophagy and investigates the possible regulatory mechanisms. This article will deepen our understanding of the relationship between VD/VDR and autophagy and suggests novel strategies for IDD prevention and treatment.

Cyanidin attenuates the apoptosis of rat nucleus pulposus cells and the degeneration of intervertebral disc via the JAK2/STAT3 signal pathway in vitro and in vivo.

CONTEXT: Cyanidin has been shown to have therapeutic potential in osteoarthritis. However, it is unclear whether cyanidin prevents the progression of intervertebral disc degeneration (IVDD). OBJECTIVE: This study evaluates the effects of cyanidin on IVDD in vitro and in vivo. MATERIALS AND METHODS: Nucleus pulposus cells (NPCs) isolated from lumbar IVD of 4-week-old male Sprague-Dawley (SD) rats were exposed to 20 ng/mL IL-1ß, and then treated with different doses (0-120 µM) of cyanidin for 24 h. SD rats were classified into three groups (n = 8) and treated as follows: control (normal saline), IVDD (vehicle), IVDD + cyanidin (50 mg/kg). Cyanidin was administered intraperitoneally for 8 weeks. RESULTS: The IC50 of cyanidin for NPCs was 94.78 µM, and cyanidin had no toxicity at concentrations up to 500 mg/kg in SD rats. Cyanidin inhibited the apoptosis of NPCs induced by IL-1ß (12.73 ± 0.61% vs. 18.54 ± 0.60%), promoted collagen II (0.82-fold) and aggrecan (0.81-fold) expression, while reducing MMP-13 (1.02-fold) and ADAMTS-5 (1.40-fold) expression. Cyanidin increased the formation of autophagosomes in IL-1ß-induced NPCs, and promoted LC3II/LC3I (0.83-fold) and beclin-1 (0.85-fold) expression, which could be reversed by chloroquine. Cyanidin inhibited the phosphorylation of JAK2 (0.47-fold) and STAT3 (0.53-fold) in IL-1ß-induced NPCs. The effects of cyanidin could be enhanced by AG490. Furthermore, cyanidin mitigated disc degeneration in IVDD rats in vivo. DISCUSSION AND CONCLUSIONS: Cyanidin improved the function of NPCs in IVDD by regulating the JAK2/STAT3 pathway, which may provide a novel alternative strategy for IVDD. The mechanism of cyanidin improving IVDD still needs further work for in-depth investigation.

Anti-Degenerative Effect of Melatonin on Intervertebral Disc: Protective Contribution against Inflammation, Oxidative Stress, Apoptosis, and Autophagy.

Intervertebral disc (IVD) degeneration is a leading cause of lower back pain. Although the etiology of IVD degeneration (IVDD) is unclear, excessive oxidative stress, inflammation and apoptosis, and disruption of autophagy play an important role in the pathogenesis of IVDD. Therefore, finding a solution to mitigate these processes could stop or reduce the development of IVDD. Melatonin, a powerful antioxidant, plays an important role in regulating cartilage tissue hemostasis. Melatonin inhibits the destruction of the extracellular matrix (ECM) of the disc. Melatonin preserves ECM contents, including sox-9, aggrecan, and collagen II through inhibiting matrix degeneration enzymes such as MMP-13. These protective effects may be mediated by the inhibition of oxidative stress, inflammation and apoptosis, and regulation of autophagy in IVD cells.

Inhibition of IRE1 suppresses the catabolic effect of IL-1ß on nucleus pulposus cell and prevents intervertebral disc degeneration in vivo.

Neck pain and low back pain are two of the major diseases, which causes patients a low quantify of life and a heavy economic burden, intervertebral disc degeneration (IDD) contributes to them, and the mechanism is not totally clear. The increased inflammatory cytokines including interleukin (IL)-1ß and tumor necrosis factor (TNF)α and downstream signaling pathways are involved. Inositol requiring enzyme 1 (IRE1) is a crucial enzyme that regulates endoplasmic reticulum (ER) stress. It is reported that IRE1 plays an important role in the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. Considering this, we performed a series of experiments in vitro and in vivo to evaluate the role of IRE1 in the progress of IDD. We demonstrated that IRE1 pathway was induced by IL-1ß, inhibition of IRE1 suppressed the matrix degeneration of NP cells and ameliorated IDD grade in the punctured rat model. Further results indicated that inhibition of IRE1 suppressed H2O2 induced cell senescence, IL-1ß-induced cellular reactive oxygen species (ROS) level and the activation of NF-κB, PI3K/Akt and MAPK signaling pathways. It also played a crucial role in the apoptosis of NP cells and the progress of macrophage polarization. Our findings demonstrated that inhibition of IRE1 could suppress the degeneration of NP cells and prevent IDD in vivo. IRE1 may be a potential target for IDD treatment.

Dynamic Pressure Stimulation Upregulates Collagen II and Aggrecan in Nucleus Pulposus Cells Through Calcium Signaling.

STUDY DESIGN: An in vitro study to investigate the effect of pressure stimulation on nucleus pulposus (NP) cells. OBJECTIVE: The aim of this study was to investigate the question whether physical stimulation can be leveraged to enhance extracellular matrix (ECM) synthesis as a preventive measure for intervertebral disc (IVD) degeneration. SUMMARY OF BACKGROUND DATA: ECM plays an important role in regulating hydration and pressure balance of the IVD. METHODS: Cellular stimulation devices with different pressurizing protocols were used to create a pressurized environment to cells cultures. The setup was used to mimic the pressurized conditions within IVD to investigate the effect of pressure stimulation on NP cells. RESULTS: Pressure stimulation at 300 kPa can enhance the synthesis of ECM proteins Collagen II and aggrecan in NP cells and the effect of dynamic pressure stimulation outperformed the static one. The difference between static and dynamic pressure stimulation was due primarily to calcium signaling activated by pressure fluctuation. The superior effect of dynamic pressure holds for a wide range of stimulation durations, relating to the range of spontaneous calcium oscillations in NP cells. CONCLUSION: The results link mechanotransduction to the downstream ECM protein synthesis and suggest slow exercises that correspond with spontaneous calcium oscillations in NP cells can be effective to stimulate ECM synthesis in IVD.

[Research advances in prevention and treatment of intervertebral disc degeneration by targeting mitochondrial quality control].

Intervertebral disc degeneration(IDD) is a common clinical degenerative disease of the musculoskeletal system, which increases the risk of lower back pain, severely reduces patients' quality of life and work efficiency, and imposes a large economic burden on society. Mitochondria, as the "power stations" of eukaryotic cells, are involved in many key biological processes, and their abnormal function can induce cellular dysfunction and lead to the development of a series of degenerative diseases. Recent studies have revealed that mitochondrial quality control(MQC) imbalance, characterized by abnormalities in mitochondrial oxidative stress, kinetics, mitophagy and biogenesis, plays an important role in IDD. The research reviewed the progress of the role of MQC in IDD and summarized traditional Chinese medicine monomers and small molecule compounds targeting MQC for the treatment of IDD, with the aim of providing reference and new ideas for studying novel therapeutic strategies for IDD.

Circular RNA hsa_circ_0001658 Inhibits Intervertebral Disc Degeneration Development by Regulating hsa-miR-181c-5p/FAS.

METHODS: We obtained microarray data (GSE116726, GSE67566) from Gene Expression Omnibus database, and differential expression level of ncRNA in nucleus pulposus (NP) tissues of IDD patients was analyzed. The potential circRNA-miRNA-mRNA regulatory network was analyzed by starBase. The effect of the interaction between hsa_circ_0001658, hsa-miR-181c-5p, and FAS on the proliferation and apoptosis of human neural progenitor cells (hNPCs) was studied. RESULTS: hsa_circ_0001658 was significantly upregulated (logFC > 2.0 and adj.P.Val < 0.01) in the NP tissues of IDD patients, and hsa-miR-181c-5p expression was downregulated (logFC < -2.0 and adj.P.Val < 0.01). Silencing of hsa-miR-181c-5p or overexpression of hsa_circ_0001658 inhibited the proliferation of hNPCs and promoted their apoptosis. hsa_circ_0001658 acted as a sponge of hsa-miR-181c-5p. hsa-miR-181c-5p downregulated the expression of Fas cell surface death receptor (FAS), promoted the proliferation, and inhibited the apoptosis of hNPCs. hsa_circ_0001658 functioned in hNPCs through targeting hsa-miR-181c-5p/FAS. CONCLUSION: Circular RNA hsa_circ_0001658 inhibits IDD development by regulating hsa-miR-181c-5p/FAS. It is expected to be a potential target for the therapy of IDD.

Activation of Hypoxia-Inducible Factor-1α Signaling Pathway Has the Protective Effect of Intervertebral Disc Degeneration.

Intervertebral discs (IVDs) have poor nutrient diffusion, because the nucleus pulposus (NP) lacks direct vascular supply and likely generates adenosine triphosphate by anaerobic glycolysis. Regulation of glycolysis is mediated by hypoxia-inducible factor-1α (HIF-1α), a transcription factor that responds to local oxygen tension. Constitutively active HIF-1α (CA HIF-1α) was created by point mutation and determined the protective role of HIF-1α in IVD degeneration. Under fluoroscopy, rat caudal IVD segments were stabbed by a needle puncture, and pcDNA3- HIF-1α wild-type (WT) or pcDNA3-CA HIF-1α was transfected into NP cell lines. The constitutive activity of CA HIF-1α was analyzed using a luciferase assay after cell lysis. Next, IVD tissue samples were retrieved from five patients with degenerative lumbar spinal stenosis at the time of surgery, and NP cells were cultured. NP cells were transfected with CA HIF-1α, and relevant gene expression was measured. HIF-1α protein levels in the nucleus were significantly higher, and transcriptional activity was 10.3-fold higher in NP cells with CA HIF-1α than in those with HIF-1α WT. Gene transfer of CA HIF-1α into NP cells enhanced the expression of Glut-1, Glut-3, aggrecan, type II collagen, and Sox9. Moreover, CA HIF-1α reduced the apoptosis of NP cells induced by the Fas ligand. The HIF-1α and collagen 2 expression levels were notably increased in the NP cells of the CA HIF-1α transfected segments in histology and immunohistochemistry study. Collectively, these results suggest that activation of HIF-1α signaling pathway may play a protective role against IVD degeneration and could be used as a future therapeutic agent.

Curcumol Alleviates the Inflammation of Nucleus Pulposus Cells via the PI3K/Akt/NF-κB Signaling Pathway and Delays Intervertebral Disk Degeneration.

BACKGROUND: Intervertebral disk degeneration (IVDD) is closely associated with inflammatory environments. Curcumol has been shown to alleviate inflammation in various disease models, but its effects on IVDD remain unclear. In this study, we sought to determine the mechanism of curcumol in tumor necrosis factor (TNF)-α-induced nucleus pulposus cells and a mouse IVDD model. METHODS: Nucleus pulposus cells were pretreated with curcumol and then exposed to TNF-α. Cell viability was analyzed using CCK-8, and the messenger ribonucleic acid and protein levels of inflammatory cytokines and PI3K/Akt/NF-κB-related signaling molecules were detected using real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and western blotting. The mouse IVDD model was established by puncturing the C6/7 level of the caudal spine, and then it was treated with curcumol after surgery. Alcian blue/orange G staining was performed to evaluate the severity of intervertebral disk damage, and immunohistochemistry was performed to detect the expression of TNF-α. Toxicologic effects of curcumol were measured by performing hematoxylin-eosin staining and enzyme-linked immunosorbent assay. RESULTS: Curcumol reduced IL-1ß, IL-6, and TNF-α production in NPCs, and the phosphorylation of proteins in the PI3K/Akt/NF-κB signaling pathway was also decreased. The PI3K/Akt/NF-κB-related signaling molecules decreased when TNF-α-induced NPCs were treated with a PI3K inhibitor; however, curcumol did not reverse these effects. In vivo, curcumol ameliorated the progression of IVDD at the early stage and did not exert toxicologic effects. CONCLUSIONS: These results suggest a potential therapeutic use of curcumol to alleviate inflammation via the PI3K/Akt/NF-κB signaling pathway and delay the progression of IVDD.

Resveratrol protects human nucleus pulposus cells from degeneration by blocking IL-6/JAK/STAT3 pathway.

BACKGROUND: Nucleus pulposus cells' (NPCs') degeneration is mainly responsible for the intervertebral disc degeneration (IDD), which is closely related to inflammatory response. Among the major proinflammatory factors that are related to NPCs' degeneration, interleukin-6 (IL-6) and its downstream JAK/STAT3 pathway have received recent attention. The goal of our study is to figure out whether or how resveratrol (RSV) can protect NPCs from degeneration by affecting IL6/JAK/STAT3 pathway. METHODS: Different concentrations of RSV were added to NPCs' mediums. Cell viability was measured by MTT assay and crystal violet staining. Cell cycle and apoptosis were analyzed by flow cytometry. Protein expression level was determined by western blot. mRNA expression level was measured by qPCR. RESULTS: Our study showed that RSV improved NPCs' cell viability. It also inhibited cell apoptosis and cell cycle arrest, which were accompanied by the increased expression level of heat shock protein 90 (HSP90) and N-Cadherin. What' more, RSV also improved the NPCs' degeneration which was reflected in the increase of extracellular matrix (collagen II, Aggrecan). Moreover, RSV significantly attenuated the level of IL-6 secretion, which was accompanied by less phosphorylation of the transcription factors Janus kinase 1 (JAK1) and signal transducer and activator of transcription 3 (STAT3). CONCLUSION: RSV exerted its protective effect on HNPCs' degeneration by improving cell survival and function. The possible mechanism may be associated with the suppression of JAK/STAT3 phosphorylation and the decreased IL-6 production, which could be explained by a blockage of the positive feedback control loop between IL-6 and JAK/STAT3 pathway.

Raloxifene retards the progression of adjacent segmental intervertebral disc degeneration by inhibiting apoptosis of nucleus pulposus in ovariectomized rats.

BACKGROUND: Adjacent segmental intervertebral disk degeneration (ASDD) is a major complication secondary to lumbar fusion. Although ASSD pathogenesis remains unclear, the primary cause of intervertebral disk degeneration (IVDD) development is apoptosis of nucleus pulposus (NP). Raloxifene (RAL) could delay ASDD by inhibiting NP apoptosis. METHODS: An ASDD rat model was established by ovariectomy (OVX) and posterolateral spinal fusion (PLF) on levels 4-5 of the lumbar vertebrae. Rats in the treatment groups were administered 1 mg/kg/d RAL by gavage for 12 weeks, following which, all animals were euthanized. Lumbar fusion, apoptosis, ASDD, and vertebrae micro-architecture were evaluated. RESULTS: RAL maintained intervertebral disk height (DHI), delayed vertebral osteoporosis, reduced histological score, and inhibited apoptosis. The OVX+PLF+RAL group revealed upregulated expression of aggrecan and B-cell lymphoma-2 (bcl2), as well as significantly downregulated expression of a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4), metalloproteinase-13 (MMP-13), caspase-3, BCL2-associated X (bax), and transferase dUTP nick end labeling (TUNEL) staining. Micro-computed tomography (Micro-CT) analysis revealed higher bone volume fraction (BV/TV), bone mineral density (BMD), and trabecular number (Tb.N), and lower trabecular separation (Tb.Sp) in OVX+PLF+RAL group than in the OVX+PLF group. CONCLUSIONS: RAL can postpone ASDD development in OVX rats through inhibiting extracellular matrix metabolic imbalance, NP cell apoptosis, and vertebral osteoporosis. These findings showed RAL as a potential therapeutic target for ASDD.

Targeting oxidative stress with amobarbital to prevent intervertebral disc degeneration: Part I. in vitro and ex vivo studies.

BACKGROUND: Mounting evidence that oxidative stress contributes to the pathogenesis of intervertebral disc (IVD) degeneration (IDD) suggests that therapies targeting oxidative stress may slow or prevent disease progression. PURPOSE: The objective of this study was to investigate the inhibitory effects of amobarbital (Amo) on the mitochondria of nucleus pulposus (NP) cells under tert-butyl hydrogen peroxide (tBHP)-induced oxidative stress or in NP tissues under oxidative stress from tissue injury as a means of identifying therapeutic targets for IDD. STUDY DESIGN/SETTING: We tested the effects inhibiting mitochondria, a major source of oxidants, with Amo in NP cells subjected to two different forms of insult: exposure to tBHP, and physical injury induced by disc transection. N-acetylcysteine (NAC), an antioxidant known to protect NP cells, was compared to the complex I inhibitor, Amo. METHODS: NP cells were pre-treated for 2 hours with Amo, NAC, or both, and then exposed to tBHP for 1 hour. Apoptosis, necrosis, and reactive oxygen species (ROS) production were assessed using confocal microscopy and fluorescent probes (Annexin V, propidium iodide, and MitoSox Red, respectively). The activation of mitogen-activated protein kinases (MAPKs) involved in oxidative stress responses were interrogated by confocal imaging of immunofluorescence stains using phospho-specific antibodies to extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK), and p38. Mitochondrial function was assessed by imaging JC-1 staining, a probe for membrane potential. RESULTS: Amo was modestly more protective than NAC by some measures, while both agents improved mitochondrial function and lowered tBHP-induced apoptosis, necrosis, and ROS production. Activation of MAPK by tBHP was significantly suppressed by both drugs. Physically injured IVDs were treated immediately after transection with Amo or NAC for 24 hours, and then stained with dihydroethidium (DHE), a fluorescent probe for ROS production. Immunofluorescence was used to track the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a transcription factor that induces the expression of antioxidant genes. Amo and NAC significantly reduced ROS production and increased Nrf2 expression. CONCLUSION: These findings suggest that the progression of IDD may be forestalled by Amo via protection of NP cells from oxidative stress following IVD injury. CLINICAL SIGNIFICANCE: This study will define the extent to which a novel, minimally invasive procedure targeting oxidative stress in NP cells can augment surgical interventions intended to retard IVD degeneration.

Tea Polyphenol Attenuates Oxidative Stress-Induced Degeneration of Intervertebral Discs by Regulating the Keap1/Nrf2/ARE Pathway.

OBJECTIVE: Intervertebral disc degeneration (IDD) and low back pain caused by IDD have attracted public attention owing to their extremely high incidence and disability rate. Oxidative stress is a major cause of IDD. Tea polyphenols (TP) are natural-derived antioxidants extracted from tea leaves. This study explored the protective role of TP on the nucleus pulposus cells (NPCs) of intervertebral discs and their underlying mechanism. METHODS: An in vitro model of H2O2-induced degeneration of NPCs was established. RT-qPCR and western blotting were used to detect the mRNA and protein expression of the targets. An in vivo model of IDD was established via acupuncture of the intervertebral disc. Radiological imaging and histological staining were performed to evaluate the protective role of TP. RESULTS: H2O2 contributed to NPC degeneration by inducing high levels of oxidative stress. TP treatment effectively increased the expression of nucleus pulposus matrix-associated genes and reduced the expression of degeneration factors. Further mechanistic studies showed that TP delayed H2O2-mediated NPC degeneration by activating the Keap1/Nrf2/ARE pathway. In vivo experiments showed that TP delayed the degeneration of NPCs in rats through the Keap1/Nrf2/ARE pathway. CONCLUSION: Our study confirmed that TP activates the Keap1/Nrf2/ARE pathway to exert an antioxidative stress role, ultimately delaying the degeneration of intervertebral discs.

Cartilage endplate stem cells inhibit intervertebral disc degeneration by releasing exosomes to nucleus pulposus cells to activate Akt/autophagy.

Degeneration of the cartilage endplate (CEP) induces intervertebral disc degeneration (IVDD). Nucleus pulposus cell (NPC) apoptosis is also an important exacerbating factor in IVDD, but the cascade mechanism in IVDD is not clear. We investigated the apoptosis of NPCs and IVDD when stimulated by normal cartilage endplate stem cell (CESC)-derived exosomes (N-Exos) and degenerated CESC-derived exosomes (D-Exos) in vitro and in vivo. Tert-butyl hydroperoxide (TBHP) was used to induce inflammation of CESCs. The bioinformatics differences between N-Exos and D-Exos were analyzed using mass spectrometry, heat map, and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. NPC apoptosis was examined using TUNEL staining. The involvement of the AKT and autophagy signaling pathways was investigated using the signaling inhibitor LY294002. Magnetic resonance imaging, Western blotting, and immunofluorescence staining were used to evaluate the therapeutic effects of N-Exos in rats with IVDD. TBHP effectively induced inflammation and the degeneration of CEP in rat. N-Exos were more conducive to autophagy activation than D-Exos. The apoptotic rate of NPCs decreased obviously after treatment with N-Exos compared to D-Exos. N-Exos inhibited NPCs apoptosis and attenuated IVDD in rat via activation of the AKT and autophagy pathways. These results are the first findings to confirm that CEP delayed the progression of IVDD via exosomes. The therapeutic effects of N-Exos on NPC apoptosis inhibition and the slowing of IVDD progression were more effective than D-Exos due to activation of the PI3K/AKT/autophagy pathway, which explained the increase in the incidence of IVDD after inflammation of the CEP.