Inhibition of MAGL attenuates Intervertebral Disc Degeneration by Delaying nucleus pulposus senescence through STING

Intervertebral disc degeneration (IVDD) stands as the primary cause of low back pain (LBP). A significant contributor to IVDD is nucleus pulposus cell (NPC) senescence. However, the precise mechanisms underlying NPC senescence remain unclear. Monoacylglycerol lipase (MAGL) serves as the primary enzyme responsible for the hydrolysis of 2-arachidonoylglycerol (2-AG), breaking down monoglycerides into glycerol and fatty acids. It plays a crucial role in various pathological processes, including pain, inflammation, and oxidative stress. In this study, we utilized a lipopolysaccharide (LPS)-induced NPC senescence model and a rat acupuncture-induced IVDD model to investigate the role of MAGL in IVDD both in vitro and in vivo. Initially, our results showed that MAGL expression was increased 2.41-fold and 1.52-fold within NP tissues from IVDD patients and rats induced with acupuncture, respectively. This increase in MAGL expression was accompanied by elevated expression of p16INK4α. Following this, it was noted that the suppression of MAGL resulted in a notable decrease in the quantity of SA-β-gal-positive cells and hindered the manifestation of p16INK4α and the inflammatory factor IL-1β in NPCs. MAGL inhibition promotes type II collagen (Col-2) expression and inhibits matrix metalloproteinase 13 (MMP13), thereby restoring the balance of extracellular matrix (ECM) metabolism both in vitro and in vivo. A significant role for STING has also been demonstrated in the regulation of NPC senescence by MAGL. The expression of the STING protein was reduced by 57% upon the inhibition of MAGL. STING activation can replicate the effects of MAGL and substantially increase LPS-induced inflammation while accelerating the senescence of NPCs. These results strongly indicate that the inhibition of MAGL can significantly suppress nucleus pulposus senescence via its interaction with STING, consequently restoring the balance of ECM metabolism. This insight provides new perspectives for potential treatments for IVDD.

Injectable pathological microenvironment-responsive anti-inflammatory hydrogels for ameliorating intervertebral disc degeneration

Chronic local inflammation and resulting cellular dysfunction of nucleus pulposus (NP) cells are important pathogenic factors of intervertebral disc degeneration (IDD). Injectable pathological microenvironment-responsive hydrogels hold significant potential for treating IDD by adapting to dynamic microenvironment of IDD. Herein, we proposed an injectable gelatin-based hydrogel drug delivery system that could respond to the pathological microenvironment of IDD for controlled release of anti-inflammatory drug to promote degenerative NP repair. The hydrogel system was prepared by conjugating phenylboronic acid-modified gelatin methacryloyl (GP) with the naturally extracted anti-inflammatory drug epigallocatechin-3-gallate (EGCG) through dynamic boronic esters. The hydrogel exhibited excellent degradability, injectability, antioxidant properties, anti-inflammatory effects, and biocompatibility. It also displayed responsive-release of EGCG under high reactive oxygen species (ROS) levels and acidic conditions. The hydrogel demonstrated remarkable cytoprotective effects on NP cells in both hyperactive ROS environments and inflammatory cytokine-overexpressed environments in vitro. In vivo studies revealed that the hydrogel injected in situ could effectively ameliorate the intervertebral disc degeneration by maintaining the disc height and NP tissue structure in a rat IDD model. The hydrogel system exhibited excellent biocompatibility and responsive-release of diol-containing drugs in pathological microenvironments, indicating its potential application as a drug delivery platform.

Piezo1 channel exaggerates ferroptosis of nucleus pulposus cells by mediating mechanical stress-induced iron influx

To date, several molecules have been found to facilitate iron influx, while the types of iron influx channels remain to be elucidated. Here, Piezo1 channel was identified as a key iron transporter in response to mechanical stress. Piezo1-mediated iron overload disturbed iron metabolism and exaggerated ferroptosis in nucleus pulposus cells (NPCs). Importantly, Piezo1-induced iron influx was independent of the transferrin receptor (TFRC), a well-recognized iron gatekeeper. Furthermore, pharmacological inactivation of Piezo1 profoundly reduced iron accumulation, alleviated mitochondrial ROS, and suppressed ferroptotic alterations in stimulation of mechanical stress. Moreover, conditional knockout of Piezo1 (Col2a1-CreERT Piezo1flox/flox) attenuated the mechanical injury-induced intervertebral disc degeneration (IVDD). Notably, the protective effect of Piezo1 deficiency in IVDD was dampened in Piezo1/Gpx4 conditional double knockout (cDKO) mice (Col2a1-CreERT Piezo1flox/flox/Gpx4flox/flox). These findings suggest that Piezo1 is a potential determinant of iron influx, indicating that the Piezo1-iron-ferroptosis axis might shed light on the treatment of mechanical stress-induced diseases.

Kongensin a attenuates intervertebral disc degeneration by inhibiting TAK1-mediated PANoptosis of nucleus pulposus cells

Low back pain (LBP) is most commonly caused by intervertebral disc degeneration (IVDD). Pyroptosis, apoptosis, and necroptosis are crucial in IVDD pathogenesis; however, possible simultaneous occurrence in IVDD and co-regulation between the pathways and the regulatory mechanisms have not been investigated. PANoptosis is a regulated cell death (RCD) pathway with the key characteristics of pyroptosis, apoptosis, and necroptosis. This study revealed that tert-butyl hydroperoxide (TBHP) altered the expression of key proteins involved in PANoptosis in nucleus pulposus cells (NPCs). Furthermore, the natural product Kongensin A (KA), which has potential anti-necrotic and anti-inflammatory properties, inhibited PANoptosis. TAK1, often referred to as mitogen-activated protein kinase kinase kinase 7 (Map3k7), is a key regulator of innate immunity, cell death, inflammation, and cellular homeostasis; however, the physiological roles and regulatory mechanisms underlying IVDD remain unclear. In this study, we discovered that KA can upregulate TAK1 expression in NPCs, -which inhibits PANoptosis by suppressing oxidative stress. In conclusion, our results suggest that KA inhibits PANoptosis and delays IVDD progression in NPCs by upregulating TAK1 expression to maintain mitochondrial redox balance. Consequently, targeting TAK1 may be a promising therapeutic approach for IVDD therapy.

Ginsenoside Rg1 relieves rat intervertebral disc degeneration and inhibits IL-1β-induced nucleus pulposus cell apoptosis and inflammation via NF-κB signaling pathway

The study aimed to investigate the effect of ginsenoside Rg1 on intervertebral disc degeneration (IVDD) in rats and IL-1β-induced nucleus pulposus (NP) cells, and explore its underlying mechanism. Forty IVDD rat models were divided into the IVDD group, low-dose (L-Rg1) group (intraperitoneal injection of 20 mg/kg/d ginsenoside Rg1), medium-dose (M-Rg1) group (intraperitoneal injection of 40 mg/kg/d ginsenoside Rg1), and high-dose (H-Rg1) group (intraperitoneal injection of 80 mg/kg/d ginsenoside Rg1). The pathological change was observed by HE and safranin O-fast green staining. The expression of IL-1β, IL-6, TNF-α, MMP3, aggrecan, and collagen II was detected. The expression of NF-κB p65 in IVD tissues was detected. Rat NP cells were induced by IL-1β to simulate IVDD environment and divided into the control group, IL-1β group, and 20, 50, and 100 µmol/L Rg1 groups. The cell proliferation activity, the apoptosis, and the expression of IL-6, TNF-α, MMP3, aggrecan, collagen II, and NF-κB pathway-related protein were detected. In IVDD rats, ginsenoside Rg1 improved the pathology of IVD tissues; suppressed the expression of IL-1β, IL-6, TNF-α, aggrecan, and collagen II; and inhibited the expression of p-p65/p65 and nuclear translocation of p65, to alleviate the IVDD progression. In the IL-1β-induced NP cells, ginsenoside Rg1 also improved the cell proliferation and inhibited the apoptosis and the expression of IL-6, TNF-α, aggrecan, collagen II, p-p65/p65, and IκK in a dose-dependent manner. Ginsenoside Rg1 alleviated IVDD in rats and inhibited apoptosis, inflammatory response, and ECM degradation in IL-1β-induced NP cells. And Rg1 may exert its effect via inhibiting the activation of NF-κB signaling pathway.

The development of a nucleus pulposus-derived cartilage analog scaffold for chondral repair and regeneration

Focal chondral defects (FCDs) significantly impede quality of life for patients and impose severe economic costs on society. One of the most promising treatment options-autologous matrix-induced chondrogenesis (AMIC)-could benefit from a scaffold that contains both of the primary cartilage matrix components-sulfated glycosaminoglycans (sGAGs) and collagen type II. Here, 17 different protocols were evaluated to determine the most optimum strategy for decellularizing (decelling) the bovine nucleus pulposus (bNP) to yield a natural biomaterial with a cartilaginous constituency. The resulting scaffold was then characterized with respect to its biochemistry, biomechanics and cytocompatibility. Results indicated that the optimal decell protocol involved pre-crosslinking the tissue prior to undergoing decell with trypsin and Triton X-100. The residual DNA content of the scaffold was found to be 32.64 ± 9.26 ng/mg dry wt. of tissue with sGAG and hydroxyproline (HYP) contents of 72.53 ± 16.43. and 78.38 ± 8.46 μg/mg dry wt. respectively. The dynamic viscoelastic properties were found to be preserved (complex modulus: 17.92-16.62 kPa across a range of frequencies) while the equilibrium properties were found to have significantly decreased (aggregate modulus: 11.51 ± 9.19 kPa) compared to the non-decelled fresh bNP tissue. Furthermore, the construct was also found to be cytocompatible with bone marrow stem cells (BMSCs). While it was not permissive of cellular infiltration, the BMSCs were still found to have lined the laser drilled channels in the scaffold. Taken together, the biomaterial developed herein could be a valuable addition to the AMIC family of scaffolds or serve as an off-the-shelf standalone option for cartilage repair.

[Effect of fiber volume and material property and nucleus pulposus area on intervertebral disc mechanical behavior]

The material properties and volume proportion of the fibers as well as the cross-sectional area proportion of nucleus pulposus vary greatly in different studies. The effect of these factors on the mechanical behavior of intervertebral discs (IVDs) are uncertain. The IVDs finite element models with different parameters were created to investigate the pressure, height, rotation, stress, and strain of the IVDs under loads: pure compression, rotation after compression or axial moment after compression. The results showed that the material properties of fibers had great impact on the mechanical behavior of IVDs, especially on the rotation angle. When the fiber volume ratio was small, its changes had a significant impact on the rotation angle of the IVDs. The area proportions of nucleus pulposus had relatively little effect on the mechanical behavior of IVDs. The IVDs rotation should be observed when validating the model. By adjusting the elastic modulus or volume ratio of fibers within a reasonable range, a model that could simulate the mechanical behavior of normal IVDs could be obtained. It was reasonable to make the area proportion of nucleus pulposus within 25%-50% for the IVDs finite element model. This study provides guidance and reference for finite element modeling of the IVDs and the investigation of the IVDs degeneration mechanism.

From hyperglycemia to intervertebral disc damage: exploring diabetic-induced disc degeneration

The incidence of lumbar disc herniation has gradually increased in recent years, and most patients have symptoms of low back pain and nerve compression, which brings a heavy burden to patients and society alike. Although the causes of disc herniation are complex, intervertebral disc degeneration (IDD) is considered to be the most common factor. The intervertebral disc (IVD) is composed of the upper and lower cartilage endplates, nucleus pulposus, and annulus fibrosus. Aging, abnormal mechanical stress load, and metabolic disorders can exacerbate the progression of IDD. Among them, high glucose and high-fat diets (HFD) can lead to fat accumulation, abnormal glucose metabolism, and inflammation, which are considered important factors affecting the homeostasis of IDD. Diabetes and advanced glycation end products (AGEs) accumulation- can lead to various adverse effects on the IVD, including cell senescence, apoptosis, pyroptosis, proliferation, and Extracellular matrix (ECM) degradation. While current research provides a fundamental basis for the treatment of high glucose-induced IDD patients. further exploration into the mechanisms of abnormal glucose metabolism affecting IDD and in the development of targeted drugs will provide the foundation for the effective treatment of these patients. We aimed to systematically review studies regarding the effects of hyperglycemia on the progress of IDD.

The most influential articles on stem cells in intervertebral disc degeneration

BACKGROUND

Stem cell-related studies have been increasingly conducted to facilitate the regeneration of degenerative discs. However, analyses of high-impact articles focused on this topic are rare. This study aimed to determine and summarize the most-cited studies examining stem cells in the context of intervertebral disc degeneration (IDD).

METHODS

We searched the Web of Science (WoS) database for stem cell-related articles in IDD, and the 50 highest-cited papers were summarized. A correlation analysis was conducted to determine the relationship among WoS citations, Altmetric Attention Score (AAS), and Dimensions.

RESULTS

The number of citations of the top 50 manuscripts ranged from 92 to 370. The top three countries were the United States (14), China (10), and Japan (9). Spine (12) was the most prevalent journal, and this was followed by Biomaterials (6). Bone marrow-derived stem cells were the most common subject (38), and they were followed by nucleus pulposus-derived stem cells (4) and annulus fibrosus-derived stem cells (4). Humans were the most studied species (31), and the next most studied were rabbits (9) and rats (7). There was a very high correlation between WoS and Dimension citations (p < 0.001, r = 0.937).

CONCLUSIONS

For the first time, the highest impact articles examining stem cells in the context of IDD were assessed together. The current study provides a deepened understanding of historical studies focused on stem cells in IDD and is beneficial for future studies in this field.

Potential Use of Extracellular Vesicles in the Treatment of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is a major cause of low back pain, and several studies have evaluated the efficacy of extracellular vesicles (EVs) in the treatment of IVDD. The databases PubMed, Embase, and Cochrane Library were systematically searched from inception to the end of 2022 to identify studies investigating the therapeutic potential of cell-derived EVs for IVDD treatment. The following outcome measures were utilized: magnetic resonance imaging (MRI) Pfirrmann grading system, disc height index (DHI), histological grading, and apoptosis rate. A comprehensive meta-analysis was conducted, including a total of 13 articles comprising 19 studies involving 218 experimental animals. Comparative analysis between normal cell-derived EVs and placebo revealed significant reductions in MRI grade, increased DHI values, decreased nucleus pulposus cell apoptosis rates, and improved tissue grades. These findings collectively demonstrate the effective inhibition of IVDD through the application of EVs derived from cells. In conclusion, this study provides an updated synthesis of evidence supporting the efficacy of EVs as a promising therapeutic approach for IVDD treatment.

Nucleus pulposus cells regulate macrophages in degenerated intervertebral discs via the integrated stress response-mediated CCL2/7-CCR2 signaling pathway

Lower back pain (LBP), which is a primary cause of disability, is largely attributed to intervertebral disc degeneration (IDD). Macrophages (MΦs) in degenerated intervertebral discs (IVDs) form a chronic inflammatory microenvironment, but how MΦs are recruited to degenerative segments and transform into a proinflammatory phenotype remains unclear. We evaluated chemokine expression in degenerated nucleus pulposus cells (NPCs) to clarify the role of NPCs in the establishment of an inflammatory microenvironment in IDD and explored the mechanisms. We found that the production of C-C motif chemokine ligand 2 (CCL2) and C-C motif chemokine ligand 7 (CCL7) was significantly increased in NPCs under inflammatory conditions, and blocking CCL2/7 and their receptor, C-C chemokine receptor type 2(CCR2), inhibited the inductive effects of NPCs on MΦ infiltration and proinflammatory polarization. Moreover, activation of the integrated stress response (ISR) was obvious in IDD, and ISR inhibition reduced the production of CCL2/7 in NPCs. Further investigation revealed that activating Transcription Factor 3 (ATF3) responded to ISR activation, and ChIP-qPCR verified the DNA-binding activity of ATF3 on CCL2/7 promoters. In addition, we found that Toll-like receptor 4 (TLR4) inhibition modulated ISR activation, and TLR4 regulated the accumulation of mitochondrial reactive oxygen species (mtROS) and double-stranded RNA (dsRNA). Downregulating the level of mtROS reduced the amount of dsRNA and ISR activation. Deactivating the ISR or blocking CCL2/7 release alleviated inflammation and the progression of IDD in vivo. Moreover, MΦ infiltration and IDD were inhibited in CCR2-knockout mice. In conclusion, this study highlights the critical role of TLR4/mtROS/dsRNA axis-mediated ISR activation in the production of CCL2/7 and the progression of IDD, which provides promising therapeutic strategies for discogenic LBP.

[Research Progress in Nucleus Pulposus Tissue Engineering in Lumbar Intervertebral Disc]

Lumbar intervertebral disc degeneration is a common pathological process in the spine,with the main clinical symptoms of low back pain,numbness of lower limbs,and defecation dysfunction.The occurrence and development of lumbar intervertebral disc degeneration are determined by multiple factors,and the pathophysiological and cellular mechanisms remain to be fully understood.Nucleus pulposus tissue engineering is a new biotherapy that combines biological histology with material science to treat diseases including lumbar intervertebral disc degeneration.Clinicians should fully learn the complex relationship between nucleus pulposus tissue engineering and lumbar intervertebral disc degeneration,which will facilitate the clinical treatment of lumbar intervertebral disc degeneration,the rehabilitation of lumbar intervertebral disc after treatment,and the prevention of this disease in the population.

Modeling the effects of hydration on viscoelastic properties of nucleus pulposus tissue in shear using the fractional Zener model

Nucleus pulposus (NP) tissue in the intervertebral disc (IVD) is a viscoelastic material exhibiting both solid- and fluid-like mechanical behaviors. Advances in viscoelastic models incorporating fractional calculus, such as the Fractional Zener (FZ) model, have potential to describe viscoelastic behaviors. The objectives of this study were to determine whether the FZ model can accurately describe the shear viscoelastic properties of NP tissue and determine if the fractional order (α) is related to tissue hydration. 30 caudal IVDs underwent equilibrium dialysis in 5% or 25% polyethylene glycol solutions to alter tissue hydration. Excised NP tissue underwent stress relaxation testing in shear and unconfined compression. Stress relaxation data was fitted to the FZ model to obtain viscoelastic properties. In both loading modes, the initial modulus was greater for the less hydrated 25% equilibrated samples compared to 5% with no change in the equilibrium modulus. Samples with lower water content (25% samples) had shorter relaxation times in shear and longer time constants in compression, highlighting the different interactions between the fluid and solid matrix in loading modes. Samples with lower water content had α values closer to 0, indicating that less hydrated samples behaved more solid-like on the viscoelastic spectrum. Tissue hydration correlated with α values for 25% samples in shear. This study demonstrates that the FZ model may be used to describe IVD tissue behavior under both loading modes; however, the greatest utility of the FZ model is in describing flow-independent shear behaviors, and α may inform tissue hydration in shear.

In situ forming, mechanically resilient hydrogels prepared from 4a-[PEG-b-PTMC-Ac] and thiolated chondroitin sulfate for nucleus pulposus cell delivery

Intervertebral disk degeneration (IVDD) is a common condition that causes severe back pain and affects patients' mobility and life quality considerably. IVDD originates within the central region of the disk called the nucleus pulposus (NP). Removing the damaged tissue and replacing it with NP cells (NPCs) delivered within an in situ forming hydrogel is a promising treatment approach. Herein we describe a hydrogel formulation based on 4-arm [poly(ethylene glycol)-b-poly(trimethylene carbonate)-acrylate] (4a[PEG-b-PTMC-Ac]) crosslinked with thiolated chondroitin sulfate via Michael-type reaction for this purpose. A library of hydrogels based on 15 kDa 4a-[PEG] with PTMC blocks of varying molecular weight were prepared and characterized. The instantaneous moduli of the hydrogels were adjustable from 24 to 150 kPa depending on the length of the PTMC block and the polymer volume fraction. The influence of each of these parameters was effectively explained using both scaling or mean field theories of polyelectrolyte hydrogels. The hydrogels were resistant to cyclic compressive loading and degraded gradually over 70 days in vitro. A hydrogel formulation with an instantaneous modulus at the high end of the range of values reported for human NP tissue was chosen to assess the ability of these hydrogels for delivering NPCs. The prepolymer solution was injectable and formed a hydrogel within 30 minutes at 37 °C. Bovine NPCs were encapsulated within this hydrogel with high viability and proliferated throughout a 28 day, hypoxic culture period. The encapsulated NPCs formed clusters and deposited collagen type II but no collagen type I within the hydrogels. Despite an initial gradual decrease, a steady-state modulus was reached at the end of the 28 day culture period that was within the range reported for healthy human NP tissue. This in situ forming hydrogel formulation is a promising approach and with further development could be a viable clinical treatment for IVDD.

Panax notoginseng saponins inhibits oxidative stress- induced human nucleus pulposus cell apoptosis and delays disc degeneration in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Panax notoginseng (Burk) F. H. Chen has been a popular traditional Chinese medicine with a long history of treating low back pain. Its main active ingredient, Panax notoginseng saponins (PNS), can be found in several Chinese patent medicines that are frequently used to treat blood stasis type low back pain. Intervertebral disc degeneration (IDD) is the most common cause of back pain, and the injection of PNS has been used to relieve IDD-induced back pain in clinical practice. Despite its effectiveness, the exact mechanisms of action for PNS injections remain unclear.

AIM OF THE STUDY

IDD as a consequence of aging involves apoptosis of nucleus pulposus (NP) cells and imbalanced degradation of extracellular matrix (ECM) induced by several factors including oxidative stress. We hypothesized that PNS may have a therapeutic effect on IDD via inhibiting apoptosis of NP cells and degradation of ECM under oxidative stress.

MATERIALS AND METHODS

In this study, network pharmacology was initially employed to predict the targets of PNS against IDD. Subsequently, commercial PNS was analyzed by high-performance liquid chromatography to confirm the ingredients for in vitro and in vivo experiments. In vitro experiments were conducted on human nucleus pulposus (HNP) cells, including CCK-8, RT-PCR, Western blot, immunofluorescence staining, autophagic flux detection, and TUNEL assay. In vivo experiments were also performed on rats with IDD of tail discs induced by annular fibrosus needle puncture, which involved MRI, HE staining, and immunohistochemistry.

RESULTS

Our study demonstrated the theoretical targets of PNS against IDD, including Caspase 3, MMP13, Akt, and autophagy, based on network pharmacology. Subsequently, in vitro experiments revealed that PNS attenuated cellular apoptosis of NP by suppressing the expression of cleaved-caspase 3 and the ratio of Bax/Bcl-2 under H2O2 stimulation. Autophagy was also inhibited by PNS treatment, and the protective effect was abolished with rapamycin, an autophagy inducer, indicating that autophagy inhibition was involved in the protective effect of PNS on IDD. Furthermore, Akt/mTOR pathway activation was observed in HNP cells responding to H2O2 with PNS treatment, which played a role in autophagy downregulation. PNS was also shown to promote the expression of anabolic genes such as COL2A1 and ACAN while inhibiting the expression of catabolic gene MMP13 in HNP cells. In addition, the in vivo study revealed that PNS treatment could ameliorate IDD in a puncture-induced rat tail model. The development of IDD was significantly reduced, and there was decreased MMP13 expression, as well as increased COL2A1 protein expression in NP tissues.

CONCLUSION

Our study showed that PNS could protect HNP cells against apoptosis via autophagy inhibition and ameliorate disc degeneration in vivo, indicating its potential to be a therapeutic agent for IDD.

Bardoxolone methyl breaks the vicious cycle between M1 macrophages and senescent nucleus pulposus cells through the Nrf2/STING/NF-κB pathway

Intervertebral disc (IVD) degeneration (IDD), an age-related degenerative disease, is accompanied by the accumulation of senescent nucleus pulposus (NP) cells and extracellular matrix (ECM) degradation. The current study aims to clarify the role of M1 macrophages in the senescence of NP cells, and further explores whether bardoxolone methyl (CDDO-Me) can alleviate the pathological changes induced by M1 macrophages and relieve IDD. On the one hand, conditioned medium (CM) of M1 macrophages (M1CM) triggered senescence of NP cells and ECM degradation in a time-dependent manner. On the other hand, CM of senescent NP cells (S-NPCM) was collected to treat macrophages and we found that S-NPCM promoted the migration and M1-polarization of macrophages. However, both of the above effects can be partially blocked by CDDO-Me. We further explored the mechanism and found that M1CM promoted the expression level of STING and nuclear translocation of P65 in NP cells, while being restrained by CDDO-Me and STING inhibitor H151. In addition, the employment of Nrf2 inhibitor ML385 facilitated the expression level of STING and nuclear translocation of P65, thereby blocking the effects of CDDO-Me on suppressing senescence of NP cells and ECM degradation. In vivo, the injection of CDDO-Me into the disc decreased the infiltration of M1 macrophages and ameliorated degenerative manifestations in the puncture-induced rat IDD model. In conclusion, CDDO-Me was proved to break the vicious cycle between M1 macrophages and senescent NP cells through the Nrf2/STING/NF-κB pathway, thereby attenuating the progression of IDD.

Selenium-SelK-GPX4 axis protects nucleus pulposus cells against mechanical overloading-induced ferroptosis and attenuates senescence of intervertebral disc

Intervertebral disc degeneration (IVDD) is one of the most prevalent spinal degenerative disorders and imposes places heavy medical and economic burdens on individuals and society. Mechanical overloading applied to the intervertebral disc (IVD) has been widely recognized as an important cause of IVDD. Mechanical overloading-induced chondrocyte ferroptosis was reported, but the potential association between ferroptosis and mechanical overloading remains to be illustrated in nucleus pulposus (NP) cells. In this study, we discovered that excessive mechanical loading induced ferroptosis and endoplasmic reticulum (ER) stress, which were detected by mitochondria and associated markers, by increasing the intracellular free Ca2+ level through the Piezo1 ion channel localized on the plasma membrane and ER membrane in NP cells. Besides, we proposed that intracellular free Ca2+ level elevation and the activation of ER stress are positive feedback processes that promote each other, consistent with the results that the level of ER stress in coccygeal discs of aged Piezo1-CKO mice were significantly lower than that of aged WT mice. Then, we confirmed that selenium supplementation decreased intracellular free Ca2+ level by mitigating ER stress through upregulating Selenoprotein K (SelK) expression. Besides, ferroptosis caused by the impaired production and function of Glutathione peroxidase 4 (GPX4) due to mechanical overloading-induced calcium overload could be improved by selenium supplementation through Se-GPX4 axis and Se-SelK axis in vivo and in vitro, eventually presenting the stabilization of the extracellular matrix (ECM). Our findings reveal the important role of ferroptosis in mechanical overloading-induced IVDD, and selenium supplementation promotes significance to attenuate ferroptosis and thus alleviates IVDD, which might provide insights into potential therapeutic interventions for IVDD.

Decellularized nucleus pulposus matrix/chitosan hybrid hydrogel combined with nucleus pulposus stem cells and GDF5-loaded microspheres for intervertebral disc degeneration prevention

BACKGROUND

Intervertebral disc degeneration (IDD) is considered an important pathological basis for spinal degenerative diseases. Tissue engineering is a powerful therapeutic strategy that can effectively restore the normal biological properties of disc units. In this study, hydrogels loaded with growth/differentiation factor 5 (GDF5) and stem cells were combined to provide an effective strategy for nucleus pulposus regeneration.

METHODS

Nucleus pulposus stem cells (NPSCs) were obtained by low-density inoculation and culture, and their stem cell characteristics were verified by flow cytometry and a tri-lineage-induced differentiation experiment. A decellularized nucleus pulposus matrix (DNPM) and chitosan hybrid hydrogel was prepared, and GDF5-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres were incorporated into the hydrogels to obtain a composite hydrogels with GDF5-loaded microspheres. Taking bone marrow mesenchymal stem cells (BMSCs) as a reference, the effect of composite hydrogels with GDF5-loaded microspheres on the chondrogenic differentiation of NPSCs was evaluated. A model of intervertebral disc degeneration induced by acupuncture on the tail of rats was constructed, and the repair effect of composite hydrogels with GDF5-loaded microspheres combined with NPSCs on IDD was observed.

RESULTS

Stem cell phenotype identification, stemness gene expression and tri-lineage-induced differentiation confirmed that NPSCs had characteristics similar to those of BMSCs. The rat DNPM and chitosan hybrid hydrogels had good mechanical properties, and the GDF5-loaded microspheres sustainably released GDF5. NPSCs grew normally in the composite hydrogels and gradually expressed a chondrocyte phenotype. Animal experiments showed that the composite hydrogels with GDF5-loaded microspheres combined with NPSCs effectively promoted nucleus pulposus regeneration and that the effect of the hydrogels on the repair of IDD was significantly better than that of BMSCs.

CONCLUSION

GDF5-loaded microspheres combined with DNPM/chitosan composite hydrogels can effectively promote the differentiation of NPSCs into nucleus pulposus-like cells and effectively preventIDD.

Senescent response in inner annulus fibrosus cells in response to TNFα, H2O2, and TNFα-induced nucleus pulposus senescent secretome

Senescence, particularly in the nucleus pulposus (NP) cells, has been implicated in the pathogenesis of disc degeneration, however, the mechanism(s) of annulus fibrosus (AF) cell senescence is still not well understood. Both TNFα and H2O2, have been implicated as contributors to the senescence pathways, and their levels are increased in degenerated discs when compared to healthy discs. Thus, the objective of this study is to identify factor(s) that induces inner AF (iAF) cell senescence. Under TNFα exposure, at a concentration previously shown to induce senescence in NP cells, bovine iAF cells did not undergo senescence, indicated by their ability to continue to proliferate as demonstrated by Ki67 staining and growth curves and lack of expression of the senescent markers, p16 and p21. The lack of senescent response occurred even though iAF express higher levels of TNFR1 than NP cells. Interestingly, iAF cells showed no increase in intracellular ROS or secreted H2O2 in response to TNFα which contrasted to NP cells that did. Following TNFα treatment, only iAF cells had increased expression of the superoxide scavengers SOD1 and SOD2 whereas NP cells had increased NOX4 gene expression, an enzyme that can generate H2O2. Treating iAF cells with low dose H2O2 (50 μM) induced senescence, however unlike TNFα, H2O2 did not induce degenerative-like changes as there was no difference in COL2, ACAN, MMP13, or IL6 gene expression or number of COL2 and ACAN immunopositive cells compared to untreated controls. The latter result suggests that iAF cells may have distinct degenerative and senescent phenotypes. To evaluate paracrine signalling by senescent NP cells, iAF and TNFα-treated NP cells were co-cultured. In contact co-culture the NP cells induced iAF senescence. Thus, senescent NP cells may secrete soluble factors that induce degenerative and senescent changes within the iAF. This may contribute to a positive feedback loop of disc degeneration. It is possible these factors may include H2O2 and cytokines (such as TNFα). Further studies will investigate if human disc cells respond similarly.

Regulating pyroptosis by mesenchymal stem cells and extracellular vesicles: A promising strategy to alleviate intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main cause of low back pain (LBP), which can lead to disability and thus generate a heavy burden on society. IVDD is characterized by a decrease in nucleus pulposus cells (NPCs) and endogenous mesenchymal stem cells (MSCs), degradation of the extracellular matrix, macrophage infiltration, and blood vessel and nerve ingrowth. To date, the therapeutic approaches regarding IVDD mainly include conservative treatment and surgical intervention. However, both can only relieve symptoms rather than stop or revert the progression of IVDD, since the pathogenesis of IVDD is not yet clear. Pyroptosis, which is characterized by Caspase family dependence and conducted by the Gasdermin family, is a newly discovered mode of programmed cell death. Pyroptosis has been observed in NPCs, annulus fibrosus cells (AFCs), chondrocytes, MSCs, macrophages, vascular endothelial cells and neurons and may contribute to IVDD. MSCs are a kind of pluripotent stem cell that can be found in almost all tissues. MSCs have a strong ability to secrete extracellular vesicles (EVs), which contain exosomes, microvesicles and apoptotic bodies. EVs derived from MSCs play an important role in pyroptosis regulation and could be beneficial for alleviating IVDD. This review focuses on clarifying the regulation of pyroptosis to improve IVDD by MSCs and EVs derived from MSCs.

Combining biomimetic collagen/hyaluronan hydrogels with discogenic growth factors promotes mesenchymal stroma cell differentiation into Nucleus Pulposus like cells

Based on stem cell injection into degenerated Nucleus Pulposus (NP), novel treatments for intervertebral disc (IVD) regeneration were disappointing because of cell leakage or inappropriate cell differentiation. In this study, we hypothesized that mesenchymal stromal cells encapsulated within injectable hydrogels possessing adequate physico-chemical properties would differentiate into NP like cells. Composite hydrogels consisting of type I collagen and tyramine-substituted hyaluronic acid (THA) were prepared to mimic the NP physico-chemical properties. Human bone marrow derived mesenchymal stromal cells (BM-MSCs) were encapsulated within hydrogels and cultivated in proliferation medium (supplemented with 10% fetal bovine serum) or differentiation medium (supplemented with GDF5 and TGFβ1) over 28 days. Unlike pure collagen, collagen/THA composite hydrogels were stable over 28 days in culture. In proliferation medium, the cell viability within pure collagen hydrogels was high, whereas that in composite and pure THA hydrogels was lower due to the weaker cell adhesion. Nonetheless, BM-MSCs proliferated in all hydrogels. In composite hydrogels, cells exhibited a rounded morphology similar to NP cells. The differentiation medium did not impact the hydrogel stability and cell morphology but negatively impacted the cell viability in pure collagen hydrogels. A high THA content within hydrogels promoted the gene expression of NP markers such as collagen II, aggrecan, SOX9 and cytokeratin 18 at day 28. The differentiation medium potentialized this effect with an earlier and higher expression of these NP markers. Taken together, these results show that the physico-chemical properties of collagen/THA composite hydrogels and GDF5/TGFβ1 act in synergy to promote the differentiation of BM-MSCs into NP like cells.

Mechanical characterization and design of biomaterials for nucleus pulposus replacement and regeneration

Biomaterials for nucleus pulposus (NP) replacement and regeneration have great potential to restore normal biomechanics in degenerated intervertebral discs following nucleotomy. Mechanical characterizations are essential for assessing the efficacy of biomaterial implants for clinical applications. While traditional compression tests are crucial to quantify various modulus values, relaxation behaviors and fatigue resistance, rheological measurements should also be conducted to investigate the viscoelastic properties, injectability, and overall stability upon deformation. To recapitulate the physiological in vivo environment, the use of spinal models is necessary to evaluate the risk of implant extrusion and the restoration of biomechanics under different loading conditions. When designing devices for NP replacement, injectable materials are ideal to fully fill the nucleus cavity and prevent implant migration. In addition to achieving biocompatibility and desirable mechanical characteristics, biomaterial implants should be optimized to avoid implant extrusion or re-herniation post-operatively. This review discusses the most commonly used testing protocols for assessing mechanical properties of biomaterial implants and serves as reference material for enabling researchers to characterize NP implants through a unified approach whereby newly developed biomaterials may be compared and contrasted to existing devices.

Transplantation of active nucleus pulposus cells with a keep-charging hydrogel microsphere system to rescue intervertebral disc degeneration

BACKGROUND

Cell transplantation has been demonstrated as a promising approach in tissue regeneration. However, the reactive oxygen species (ROS) accumulation and inflammation condition establish a harsh microenvironment in degenerated tissue, which makes the transplanted cells difficult to survive.

METHODS

In this study, we constructed a keep-charging hydrogel microsphere system to enable cells actively proliferate and function in the degenerated intervertebral disc. Specifically, we combined Mg2+ to histidine-functionalized hyaluronic acid (HA-His-Mg2+) through coordination reaction, which was further intercrossed with GelMA to construct a double-network hydrogel microsphere (GelMA/HA-His-Mg2+, GHHM) with microfluidic methods. In vitro, the GHHM loaded with nucleus pulposus cells (GHHM@NPCs) was further tested for its ability to promote NPCs proliferation and anti-inflammatory properties. In vivo, the ability of GHHM@NPCs to promote regeneration of NP tissue and rescue intervertebral disc degeneration (IVDD) was evaluated by the rat intervertebral disc acupuncture model.

RESULTS

The GHHM significantly enhanced NPCs adhesion and proliferation, providing an ideal platform for the NPCs to grow on. The loaded NPCs were kept active in the degenerative intervertebral disc microenvironment as charged by the Mg2+ in GHHM microspheres to effectively support the loaded NPCs to reply against the ROS-induced inflammation and senescence. Moreover, we observed that GHHM@NPCs effectively alleviated nucleus pulposus degeneration and promoted its regeneration in the rat IVDD model.

CONCLUSION

In conclusion, we constructed a keep charging system with a double-network hydrogel microsphere as a framework and Mg2+ as a cell activity enhancer, which effectively maintains NPCs active to fight against the harsh microenvironment in the degenerative intervertebral disc. The GHHM@NPCs system provides a promising approach for IVDD management.

Exploring the Efficacy of Intervertebral Fusion and Nucleus Pulposus Removal in Treating Various Grades of Disc Herniation and Assessing the Significance of Lumbar Spine Rehabilitation Care

Objective

This study aims to assess the comparative effectiveness of posterior lumbar interbody fusion (PLIF) and percutaneous transforaminal endoscopic discectomy (PTED) in the treatment of various grades of intervertebral disc herniation (IDH) and evaluate the added value of incorporating McKenzie therapy-based lumbar spine rehabilitation care.

Methods

A retrospective analysis was conducted on 83 patients diagnosed with IDH admitted to our hospital between May 2020 and June 2022. Among these patients, 43 underwent PLIF (PLIF group), while the remaining 40 received PTED treatment (PTED group). Parameters such as operative time, intraoperative bleeding, hospitalization duration, Visual Analogue Score (VAS), and Oswestry Disability Index (ODI) were measured in both groups before and after the procedures. Additionally, 74 IDH patients were randomly assigned to either a research group receiving McKenzie therapy (n = 37) or a control group receiving standard care (n = 37). VAS and ODI scores were recorded pre- and post-intervention in both groups, and lumbar forward flexion joint range of motion (ROM) was assessed.

Results

The PTED group demonstrated shorter operative times, reduced intraoperative bleeding, and shorter hospital stays compared to the PLIF group (P < .05). One month after surgery, no significant differences in VAS and ODI were observed between the PLIF and PTED group patients with Pfirrmann class II-III herniation (P > .05). However, Pfirrmann class IV patients in the PLIF group exhibited lower VAS and ODI scores compared to those in the PTED group (P < .05). Following rehabilitation care, the research group exhibited lower VAS and ODI scores and greater ROM compared to the control group (P < .05).

Conclusions

PTED is characterized by reduced surgical trauma, shorter operative duration, and decreased intraoperative bleeding, while PLIF offers complete removal of the affected disc and stable intervertebral fusion. Integrating McKenzie therapy-based rehabilitation care further enhances lumbar spine function and alleviates pain in patients.

Gene expression in notochord and nuclei pulposi: a study of gene families across the chordate phylum

The transition from notochord to vertebral column is a crucial milestone in chordate evolution and in prenatal development of all vertebrates. As ossification of the vertebral bodies proceeds, involutions of residual notochord cells into the intervertebral discs form the nuclei pulposi, shock-absorbing structures that confer flexibility to the spine. Numerous studies have outlined the developmental and evolutionary relationship between notochord and nuclei pulposi. However, the knowledge of the similarities and differences in the genetic repertoires of these two structures remains limited, also because comparative studies of notochord and nuclei pulposi across chordates are complicated by the gene/genome duplication events that led to extant vertebrates. Here we show the results of a pilot study aimed at bridging the information on these two structures. We have followed in different vertebrates the evolutionary trajectory of notochord genes identified in the invertebrate chordate Ciona, and we have evaluated the extent of conservation of their expression in notochord cells. Our results have uncovered evolutionarily conserved markers of both notochord development and aging/degeneration of the nuclei pulposi.

Psoralen synergizes with exosome-loaded SPC25 to alleviate senescence of nucleus pulposus cells in intervertebral disc degeneration

OBJECTIVE

To explore the mechanism of psoralen synergized with exosomes (exos)-loaded SPC25 on nucleus pulposus (NP) cell senescence in intervertebral disc degeneration (IVDD).

METHODS

IVDD cellular models were established on NP cells by tert-butyl hydroperoxide (TBHP) induction, followed by the treatment of psoralen or/and exos from adipose-derived stem cells (ADSCs) transfected with SPC25 overexpression vector (ADSCs-oe-SPC25-Exos). The viability, cell cycle, apoptosis, and senescence of NP cells were examined, accompanied by the expression measurement of aggrecan, COL2A1, Bcl-2, Bax, CDK2, p16, and p21.

RESULTS

After TBHP-induced NP cells were treated with psoralen or ADSCs-oe-SPC25-Exos, cell proliferation and the expression of aggrecan, COL2A1, Bcl-2, and CDK2 were promoted; however, the expression of Bax, p16, p21, and inflammatory factors was decreased, and cell senescence, cycle arrest, and apoptosis were inhibited. Of note, psoralen combined with ADSCs-oe-SPC25-Exos further decelerated NP cell senescence and cycle arrest compared to psoralen or ADSCs-oe-SPC25-Exos alone.

CONCLUSION

Combined treatment of psoralen and ADSCs-oe-SPC25-Exos exerted an alleviating effect on NP cell senescence, which may provide an insightful idea for IVDD treatment.

Systemic pharmacology reveal the mechanism by which the Qiangjin Zhuanggu Qufeng mixture inhibits LPS-induced pyroptosis of rat nucleus pulposus cells

OBJECTIVE

Low back pain (LBP) is a worldwide health issue primarily attributed to intervertebral disc degeneration (IVDD). Qiangjin Zhuang Qufeng mixture (QJZG), an approved hospital-based formula with years of clinical application, has demonstrated notable therapeutic effects in the treatment of LBP. Nevertheless, the underlying mechanism by which it alleviates LBP remains uncertain.

METHODS

The bioactive constituents of QJZG were initially identified using ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). Subsequently, network pharmacology was employed to explore the core components and targets. In vivo and in vitro experiments were then conducted to validate the specific mechanism of action of QJZG based on the identified targets and pathways. Following that, ultra-high-performance liquid chromatography/mass spectrometry combined with 16S rRNA gene sequencing of blood and faecal samples was utilized to assess the impact of gut microbiota on faecal and serum metabolites subsequent to QJZG administration in intervertebral disc degeneration (IVDD) rats.

RESULTS

The principal constituents of QJZG were identified using UPLC-Q-TOF-MS/MS, revealing a substantial enrichment of flavonoids and triterpenes. Network pharmacology analysis indicated the potential inhibitory effects of QJZG on the NLRP3 inflammasome and downstream inflammatory factors. Furthermore, investigations demonstrated that intervertebral disc degeneration may be attributed to pyroptotic cell death within the nucleus pulposus. In vitro experiments were performed utilizing LPS to induce the inflammatory response in nucleus pulposus cells (NPC), and it was observed that QJZG-containing serum significantly suppressed key pyroptosis-related genes and downstream inflammatory factors. Additionally, in vivo experiments substantiated the capacity of QJZG to preserve disc height and ameliorate the progression of disc degeneration. Concurrently, oral pharmacotherapy in animal studies prominently involved the effects of Enterobacteriaceae and Clostridium, closely intertwined with lipid metabolism.

CONCLUSIONS

QJZG exhibited a delaying effect on IVDD by preserving the equilibrium between extracellular matrix (ECM) synthesis and degradation in NPCs. This effect was achieved through the suppression of NLRP3 inflammasome expression and the prevention of pyroptosis in NPCs.

[Clinical manifestation and treatment strategy of intervertebral space infection after radiofrequency ablation of lumbar nucleus pulposus]

OBJECTIVE

To study the clinical manifestations and treatment of intervertebral space infection after percutaneous lumbar radiofrequency ablation of nucleus pulposus.

METHODS

A retrospective analysis was performed of 496 patients who underwent percutaneous lumbar disc decompression using low-temperature plasma radiofrequency ablation nucleus pulposus from June 2009 to June 2019. Six patients had lumbar infection, and the infection rate was 1.21%. All patients were male, ranging in age from 20 to 61 years old. Three patients underwent single segment radiofrequency ablation, two patients underwent dual segments ablation;and one patient underwent three segment ablation, totaling 10 intervertebral discs. One patient was complicated with type 2 diabetes before operation. The interval between infection occurrence ranged from 21 to 65 days.

RESULTS

All 6 patients were followed up, and the duration ranged from 18 to 40 months, with an average of 24 months. Among them, 2 patients presented with symptoms of low back pain accompanied by fever, and imaging examination showed intervertebral space infection accompanied by abscess. In addition, 4 patients experienced low back pain but no fever, and MRI showed abnormal signals of the infected intervertebral endplate or vertebral body. One patient showed staphylococcus aureus in blood culture, while the remaining 5 patients showed negative bacterial culture. All the patients were treated with antibiotics after diagnosis. Four patients were treated with conservative management to control infection;1 patient was treated with debridement of posterior lumbar infection focus, and 1 patient was treated with debridement of posterior lumbar infection focus combined with interbody fusion and internal fixation.

CONCLUSION

The occurrence of intervertebral space infection during lumbar radiofrequency ablation nucleoplasty should be given sufficient attention. Strict aseptic technique, avoiding repeated multi segment puncture, realizing early detection and treatment, and selecting appropriate treatment methods according to the severity of infection is the guarantee of achieving curative effect.

Degenerated nucleus pulposus cells derived exosome carrying miR-27a-3p aggravates intervertebral disc degeneration by inducing M1 polarization of macrophages

BACKGROUND

Intervertebral disc degeneration (IVDD) is a major contributor to spinal disorders. Previous studies have indicated that the infiltration of immunocytes, specifically macrophages, plays a crucial role in the advancement of IVDD. Exosomes (exo) are believed to play a significant role in intercellular communication. This study aims to investigate the role of exosomes derived from degenerated nucleus pulposus (dNPc) in the process of macrophages M1 polarization.

METHODS

Nucleus pulposus (NP) tissue and nucleus pulposus cells (NPc) were collected from patients with intervertebral disc degeneration (IVDD) and idiopathic scoliosis. Immunohistochemistry analysis was performed to determine the number of M1 macrophages in NP tissue. Subsequently, exosomes derived from degenerated NP cells (dNPc-exo) and non-degenerated NP cells (nNPc-exo) were collected and co-cultured with M0 macrophages, which were induced from THP-1 cells. The M1 phenotype was assessed using western blot, flow cytometry, immunofluorescence staining, and qRT-PCR. RNA-sequencing analysis was conducted to examine the expression levels of microRNAs in the dNPc-exo and nNPc-exo groups, and qRT-PCR was performed to investigate the effect pf different microRNA to induce macrophage polarization. Furthermore, western blot and qRT-PCR were employed to demonstrate the regulatory effect of microRNAs carried by dNPc-exo on downstream target signaling pathways in macrophages. Finally, an animal model of IVDD was utilized to investigate the impact of dNPc-exo on inducing M1 polarization of macrophages and its role in the IVDD process.

RESULTS

In this study, we observed an increase in the number of M1 macrophages as the intervertebral disc (IVD) degraded. Additionally, we discovered that dNPc releases exosomes (dNPc-exo) could promote the polarization of macrophages towards the M1 phenotype. Notably, through RNA-sequencing analysis of dNPc-exo and nNPc-exo groups, we identified miR-27a-3p as a highly expressed miRNA in the dNPc-exo group, which significantly influences the induction of M1 polarization of macrophages. And then, we discovered that dNPc-exo has the ability to transport miR-27a-3p and target the PPARγ/NFκB/PI3K/AKT signaling pathway, thereby influencing the M1 polarization of macrophages. We conducted experiments using rat model of IVDD and observed that the exosomes carrying miR-27a-3p actually induced the M1 polarization of macrophages and exacerbated the degradation of IVD.

CONCLUSION

In conclusion, our findings highlight the significant role of dNPc-exo in IVDD process and provide a basis for further investigation into the mechanism of IVDD and the potential of exosome-based therapy.

A Review: Methodologies to Promote the Differentiation of Mesenchymal Stem Cells for the Regeneration of Intervertebral Disc Cells Following Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD), a highly prevalent pathological condition worldwide, is widely associated with back pain. Treatments available compensate for the impaired function of the degenerated IVD but typically have incomplete resolutions because of their adverse complications. Therefore, fundamental regenerative treatments need exploration. Mesenchymal stem cell (MSC) therapy has been recognized as a mainstream research objective by the World Health Organization and was consequently studied by various research groups. Implanted MSCs exert anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects and promote extracellular component production, as well as differentiation into IVD cells themselves. Hence, the ultimate goal of MSC therapy is to recover IVD cells and consequently regenerate the extracellular matrix of degenerated IVDs. Notably, in addition to MSC implantation, healthy nucleus pulposus (NP) cells (NPCs) have been implanted to regenerate NP, which is currently undergoing clinical trials. NPC-derived exosomes have been investigated for their ability to differentiate MSCs from NPC-like phenotypes. A stable and economical source of IVD cells may include allogeneic MSCs from the cell bank for differentiation into IVD cells. Therefore, multiple alternative therapeutic options should be considered if a refined protocol for the differentiation of MSCs into IVD cells is established. In this study, we comprehensively reviewed the molecules, scaffolds, and environmental factors that facilitate the differentiation of MSCs into IVD cells for regenerative therapies for IDD.

TMT-Based Proteomics Analysis of Senescent Nucleus Pulposus from Patients with Intervertebral Disc Degeneration

Lower back pain, a leading cause of disability worldwide, is associated with intervertebral disc degeneration (IDD) in approximately 40% of cases. Although nucleus pulposus (NP) cell senescence is a major contributor to IDD, the underlying mechanisms remain unclear. We collected NP samples from IDD patients who had undergone spinal surgery. Healthy and senescent NP tissues (n = 3) were screened using the Pfirrmann grading system combined with immunohistochemistry, as well as hematoxylin and eosin, Safranin O, Alcian blue, and Masson staining. Differentially expressed proteins (DEPs) were identified using quantitative TMT-based proteomics technology. Bioinformatics analyses included gene ontology (GO) annotation, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and protein-protein interaction (PPI) analyses. In addition, immunofluorescence was used to verify protein expression. In total, 301 DEPs were identified in senescent NP tissues, including 92 upregulated and 209 downregulated proteins. In GO, DEPs were primarily associated with NF-kappaB transcription factor, extracellular regions, cellular protein metabolic processes, and post-translational protein modification. The enriched KEGG pathways included TGF-β, Wnt, RAP1, interleukin-17, extracellular matrix-receptor adhesion, and PI3K/Akt signaling pathways. PPI analysis demonstrated interactions between multiple proteins. Finally, immunofluorescence verified the expressions of MMP3, LUM, TIMP1, and CDC42 in senescent NP cells. Our study provides valuable insights into the mechanisms underlying senescent NP tissues in IDD patients. DEPs provide a basis for further investigation of the effects of senescent factors on IDD.

Effects of Hyperbaric Oxygen Intervention on the Degenerated Intervertebral Disc: From Molecular Mechanisms to Animal Models

MicroRNA (miRNA) 107 expression is downregulated but Wnt3a protein and β-catenin are upregulated in degenerated intervertebral disc (IVD). We investigated mir-107/Wnt3a-β-catenin signaling in vitro and in vivo following hyperbaric oxygen (HBO) intervention. Our results showed 96 miRNAs were upregulated and 66 downregulated in degenerated nucleus pulposus cells (NPCs) following HBO treatment. The 3' untranslated region (UTR) of the Wnt3a mRNA contained the "seed-matched-sequence" for miR-107. MiR-107 was upregulated and a marked suppression of Wnt3a was observed simultaneously in degenerated NPCs following HBO intervention. Knockdown of miR-107 upregulated Wnt3a expression in hyperoxic cells. HBO downregulated the protein expression of Wnt3a, phosphorylated LRP6, and cyclin D1. There was decreased TOP flash activity following HBO intervention, whereas the FOP flash activity was not affected. HBO decreased the nuclear translocation of β-catenin and decreased the secretion of MMP-3 and -9 in degenerated NPCs. Moreover, rabbit serum KS levels and the stained area for Wnt3a and β-catenin in repaired cartilage tended to be lower in the HBO group. We observed that HBO inhibits Wnt3a/β-catenin signaling-related pathways by upregulating miR-107 expression in degenerated NPCs. HBO may play a protective role against IVD degeneration and could be used as a future therapeutic treatment.

Astragaloside IV relieves IL-1β-induced human nucleus pulposus cells degeneration through modulating PI3K/Akt signaling pathway

BACKGROUND

Intervertebral disc degeneration (IDD) is a multifactorial disease that is associated with nucleus pulposus (NP) apoptosis and extracellular matrix (ECM) degeneration and inflammation. Astragaloside IV (AS IV) has antioxidant, free radical scavenging, anti-inflammatory and anti-apoptosis effects. This study was to investigate whether AS IV could inhibit IL-1β-mediated apoptosis of HNP cells and its possible signal transduction pathway.

METHODS

Human nucleus pulposus cells (HNPCs) were stimulated with AS IV or LY294002 (PI3K inhibitor), followed by exposure to IL-1β for 24 hours. CCK8, TUNEL analysis and flow cytometry, ELISA and Western blotting were used to analyze the effects of AS IV on cell proliferation, apoptosis, inflammation, ECM and PI3K/Akt pathway signaling path-related proteins in IL-1β-induced HNPCs.

RESULTS

Compared with IL-1β-induced HNPCs, AS IV could improve the proliferation activity and the expressions of Collagen II, Aggrecan and Bcl-2 proteins, inhibit the apoptosis rate, inflammation and Bax and cleaved caspase-3 protein expression, and increase the activity of PI3K/Akt pathway. LY294002 attenuated the protective effect of AS IV against IL-1β-induced HNPCs degeneration.

CONCLUSION

AS IV can inhibit IL-1β-induced HNPCs apoptosis inflammation and ECM degeneration by activating PI3K/Akt signaling pathway, which can be an effective drug to reduce disc degeneration.

Development and validation of lumbar spine finite element model

The functional biomechanics of the lumbar spine have been better understood by finite element method (FEM) simulations. However, there are still areas where the behavior of soft tissues can be better modeled or described in a different way. The purpose of this research is to develop and validate a lumbar spine section intended for biomechanical research. A FE model of the 50th percentile adult male (AM) Total Human Model for Safety (THUMS) v6.1 was used to implement the modifications. The main modifications were to apply orthotropic material properties and nonlinear stress-strain behavior for ligaments, hyperelastic material properties for annulus fibrosus and nucleus pulposus, and the specific content of collagenous fibers in the annulus fibrosus ground substance. Additionally, a separation of the nucleus pulposus from surrounding bones and tissues was implemented. The FE model was subjected to different loading modes, in which intervertebral rotations and disc pressures were calculated. Loading modes contained different forces and moments acting on the lumbar section: axial forces (compression and tension), shear forces, pure moments, and combined loading modes of axial forces and pure moments. The obtained ranges of motion from the modified numerical model agreed with experimental data for all loading modes. Moreover, intradiscal pressure validation for the modified model presented a good agreement with the data available from the literature. This study demonstrated the modifications of the THUMS v6.1 model and validated the obtained numerical results with existing literature in the sub-injurious range. By applying the proposed changes, it is possible to better model the behavior of the human lumbar section under various loads and moments.

Single-cell RNA-seq analysis reveals that immune cells induce human nucleus pulposus ossification and degeneration

Background and aims

Determining the transcriptomes and molecular mechanism underlying human degenerative nucleus pulposus (NP) is of critical importance for treating intervertebral disc degeneration (IDD). Here, we aimed to elucidate the detailed molecular mechanism of NP ossification and IDD using single-cell RNA sequencing.

Methods

Single-cell RNA-seq and bioinformatic analysis were performed to identify NP cell populations with gene signatures, biological processes and pathways, and subpopulation analysis, RNA velocity analysis, and cell-to-cell communication analysis were performed in four IDD patients. We also verified the effects of immune cells on NP ossification using cultured NP cells and a well-established rat IDD model.

Results

We identified five cell populations with gene expression profiles in degenerative NP at single-cell resolution. GO database analysis showed that degenerative NP-associated genes were mainly enriched in extracellular matrix organization, immune response, and ossification. Gene set enrichment analysis showed that rheumatoid arthritis signaling, antigen processing and presentation signaling were activated in the blood cell cluster. We revealed that stromal cells, which are progenitor cells, differentiated toward an ossification phenotype and delineated interactions between immune cells (macrophages and T cells) and stromal cells. Immune factors such as TNF-α, CD74 and CCL-3 promoted the differentiation of stromal cells toward an ossification phenotype in vitro. Blocking TNF-α with a specific inhibitor successfully reversed NP ossification and modified NP morphology in vivo.

Conclusion

Our study revealed an increase in macrophages and T cells in degenerative NP, which induced stromal cell differentiation toward an ossification phenotype, and contributed to the identification of a novel therapeutic target to delay IDD.

The Inhibitory Effect of RADKPS on Pyroptosis of Nucleus Pulposus-Derived Mesenchymal Stem Cells

Intervertebral disc (IVD) degeneration (IDD) is a primary cause of low-back pain in people, which is associated with nucleus pulposus-derived mesenchymal stem cells (NPMSCs). In this study, the involvement of lipopolysaccharide (LPS) in the pyroptosis of NPMSCs was investigated. The effect of RADKPS on the pyroptosis of NPMSCs and the underlying mechanism behind the impact of RADKPS on the proliferative capacity of NPMSCs were also studied. Pyroptosis of NPMSCs was induced with 10 μg/mL LPS and its effects on the downstream signaling pathways were explored. The protective effect of RADKPS on NPMSCs under the action of LPS and its possible mechanism were explored, using different techniques such as immunohistochemical analysis, cell proliferation assay, quantitative real-time polymerase chain reaction (qPCR), and Western blot analysis. Accordingly, caspase1/p20/p10, a protein associated with pyroptosis, was found to be overexpressed in LPS-challenged NPMSCs, Furthermore, the qPCR results demonstrated that LPS promoted the expression of pyroptosis-related gene IL-1β (p < 0.0001), while downregulating the expression of Sox-9 (p < 0.001), which was a gene associated with the extracellular matrix. The immunohistochemical results identified lowered extracellular signal-regulated kinase 1/2 (ERK1/2) expression and phosphorylated (p-)ERK1/2 in the degenerated IVD tissues. In this study, the influence of RADKPS on the proliferative ability of NPMSCs was evaluated using two-dimensional (2D) and three-dimensional (3D) cultures. It was noted that RADKPS promoted the proliferation of NPMSCs in 2D and 3D cultures. The findings of the Western blot experiments revealed that RADKPS inhibited the expression of pyroptosis-related proteins, while it upregulated the p-ERK1/2 (p < 0.001), RhoA (p < 0.01), collagen II (p < 0.01), and Sox-9 (p < 0.01), whereas ERK inhibitor PD98059 and RhoA signaling pathway inhibitor CCG-1423 inhibited their expression. These findings reveal to us that RADKPS hydrogel may protect NPMSCs from pyroptosis. It was also noted that cell proliferation-related signaling pathways may promote the proliferation of NPMSCs. The results revealed that RADKPS hydrogel could be used as a potential therapeutic approach for IDD. Impact Statement RADKPS inhibits the pyroptosis of NPMSCs and promotes the production of extracellular matrix, which has the potential of intervertebral disc biotherapy.

Investigation of the Mitigation of DMSO-Induced Cytotoxicity by Hyaluronic Acid following Cryopreservation of Human Nucleus Pulposus Cells

To develop an off-the-shelf therapeutic product for intervertebral disc (IVD) repair using nucleus pulposus cells (NPCs), it is beneficial to mitigate dimethyl sulfoxide (DMSO)-induced cytotoxicity caused by intracellular reactive oxygen species (ROS). Hyaluronic acid (HA) has been shown to protect chondrocytes against ROS. Therefore, we examined the potential of HA on mitigating DMSO-induced cytotoxicity for the enhancement of NPC therapy. Human NPC cryopreserved in DMSO solutions were thawed, mixed with equal amounts of EDTA-PBS (Group E) or HA (Group H), and incubated for 3-5 h. After incubation, DMSO was removed, and the cells were cultured for 5 days. Thereafter, we examined cell viability, cell proliferation rates, Tie2 positivity (a marker of NP progenitor cells), and the estimated numbers of Tie2 positive cells. Fluorescence intensity of DHE and MitoSOX staining, as indicators for oxidative stress, were evaluated by flow cytometry. Group H showed higher rates of cell proliferation and Tie2 expressing cells with a trend toward suppression of oxidative stress compared to Group E. Thus, HA treatment appears to suppress ROS induced by DMSO. These results highlight the ability of HA to maintain NPC functionalities, suggesting that mixing HA at the time of transplantation may be useful in the development of off-the-shelf NPC products.

Ultrashort time-to-echo MR morphology of cartilaginous endplate correlates with disc degeneration in the lumbar spine

PURPOSE

Using ultrashort echo time (UTE) MRI, we determined prevalence of abnormal cartilaginous endplate (CEP), and the relationship between CEP and disc degeneration in human lumbar spines.

MATERIALS AND METHODS

Lumbar spines from 71 cadavers (age 14-74 years) were imaged at 3 T using sagittal UTE and spin echo T2 map sequences. On UTE images, CEP morphology was defined as "normal" with linear high signal intensity or "abnormal" with focal signal loss and/or irregularity. On spin echo images, disc grade and T2 values of the nucleus pulposus (NP) and annulus fibrosus (AF) were determined. 547 CEPs and 284 discs were analysed. Effects of age, sex, and level on CEP morphology, disc grade, and T2 values were determined. Effects of CEP abnormality on disc grade, T2 of NP, and T2 of AF were also determined.

RESULTS

Overall prevalence of CEP abnormality was 33% and it tended to increase with older ages (p = 0.08) and at lower spinal levels of L5 than L2 or L3 (p = 0.001). Disc grades were higher and T2 values of the NP were lower in older spines (p < 0.001) and at lower disc level of L4-5 (p < 0.05). We found significant association between CEP and disc degeneration; discs adjacent to abnormal CEPs had high grades (p < 0.01) and lower T2 values of the NP (p < 0.05).

CONCLUSION

These results suggest that abnormal CEPs are frequently found, and it associates significantly with disc degeneration, suggesting an insight into pathoetiology of disc degeneration.

Innovative design of minimal invasive biodegradable poly(glycerol-dodecanoate) nucleus pulposus scaffold with function regeneration

Minimally invasive biodegradable implants with regeneration have been a frontier trend in clinic. Degeneration of nucleus pulposus (NP) is irreversible in most of spine diseases, and traditional spinal fusion or discectomy usually injure adjacent segments. Here, an innovative minimally invasive biodegradable NP scaffold with function regeneration inspired by cucumber tendril is developed using shape memory polymer poly(glycerol-dodecanoate) (PGD), whose mechanical property is controlled to the similar with human NP by adjusting synthetic parameters. The chemokine stromal cell-derived factor-1α (SDF-1α) is immobilized to the scaffold recruiting autologous stem cells from peripheral tissue, which has better ability of maintaining disc height, recruiting autologous stem cells, and inducing regeneration of NP in vivo compared to PGD without chemokine group and hydrogel groups significantly. It provides an innovative way to design minimally invasive implants with biodegradation and functional recovery, especially for irreversible tissue injury, including NP, cartilage and so on.

Hesperidin mitigates oxidative stress-induced ferroptosis in nucleus pulposus cells via Nrf2/NF-κB axis to protect intervertebral disc from degeneration

Intervertebral disc degeneration (IVDD), a widely known contributor to low back pain (LBP), has been proved to be a global health challenging conundrum. Hesperidin (hesperetin-7-O-rutinoside, HRD) is a flavanone glycoside that belongs to the subgroup of citrus flavonoids with therapeutic effect on various diseases due to its anti-inflammatory, antioxidant properties. However, the effect of HRD on IVDD remains elusive. The human nucleus pulposus tissues were harvested for isolating human nucleus pulposus (HNP) cells to verify the expression of Nrf2. The biological effect of HRD on HNP cells were assessed in vitro, and the in vivo therapeutic effects of HRD were assessed in mice. Firstly, we found that the expression of Nrf2 was decreased with the progression of degeneration in degenerated human nucleus pulposus tissue. Subsequently, we confirmed that HRD could mitigate oxidative stress-induced ferroptosis in nucleus pulposus cells via enhancing the expression of Nrf2 axis and suppressing the NF-κB pathway to protect intervertebral disc from degeneration in vitro. Finally, the therapeutic effects of HRD were confirmed in vivo. The current study proved for the first time that HRD may protect HNP cells from degeneration by suppressing ferroptosis in an oxidative stress-dependent via enhancing the expression of Nrf2 and suppressing the NF-κB pathway. The evidence will provide a possible basis for future targeted treatment for IVDD.

Toward a mechanically biocompatible intervertebral disc: Engineering of combined biomimetic annulus fibrosus and nucleus pulposus analogs

Intervertebral disc (IVD) degeneration and accompanying lower back pain impose global medical and societal challenges, affecting over 600 million people worldwide. The IVD complex fibrocartilaginous structure is responsible for the spine biomechanical function. The nucleus pulposus (NP), composed of swellable glycosaminoglycan (GAG), transfers compressive loads to the surrounding fiber-reinforced annulus fibrosus (AF) lamellae, which stretches under tension. Together, these substructures allow the IVD to withstand extremely high and complex loads. Key to mimic the complete disc must consider the properties of its substructures. This study presents three novel substructures-a biomimetic silk-reinforced composite lamella for the AF, a GAG analog for the NP, and a novel biomimetic combined AF-NP construct. The biomimetic AF demonstrates nonlinear, hyperelastic, and anisotropic behavior similar to the native human AF, while the NP analog demonstrates mechanical behavior similar to the human NP. The synergized biomimetic AF-NP demonstrates similar behavior to the unconfined NP, with significantly increased deformations indicating improved performance. Validation of the AF-NP construct mechanics using a finite element model yields results compatible with native human IVD under various physiological loadings. The ability of our AF-NP construct to mimic the native IVD offers a revolutionary concept for the potential development of a fully functional IVD.

Trigonochinene E promotes lysosomal biogenesis and enhances autophagy via TFEB/TFE3 in human degenerative NP cells against oxidative stress

BACKGROUND

Macroautophagy (henceforth autophagy) is the major form of autophagy, which delivers intracellular cargo to lysosomes for degradation. Considerable research has revealed that the impairment of lysosomal biogenesis and autophagic flux exacerbates the development of autophagy-related diseases. Therefore, reparative medicines restoring lysosomal biogenesis and autophagic flux in cells may have therapeutic potential against the increasing prevalence of these diseases.

PURPOSE

The aim of the present study was thus to explore the effect of trigonochinene E (TE), an aromatic tetranorditerpene isolated from Trigonostemon flavidus, on lysosomal biogenesis and autophagy and to elucidate the potential underlying mechanism.

METHODS

Four human cell lines, HepG2, nucleus pulposus (NP), HeLa and HEK293 cells were applied in this study. The cytotoxicity of TE was evaluated by MTT assay. Lysosomal biogenesis and autophagic flux induced by 40 μM TE were analyzed using gene transfer techniques, western blotting, real-time PCR and confocal microscopy. Immunofluorescence, immunoblotting and pharmacological inhibitors/activators were applied to determine the changes in the protein expression levels in mTOR, PKC, PERK, and IRE1α signaling pathways.

RESULTS

Our results showed that TE promotes lysosomal biogenesis and autophagic flux by activating the transcription factors of lysosomes, transcription factor EB (TFEB) and transcription factor E3 (TFE3). Mechanistically, TE induces TFEB and TFE3 nuclear translocation through an mTOR/PKC/ROS-independent and endoplasmic reticulum (ER) stress-mediated pathway. The PERK and IRE1α branches of ER stress are crucial for TE-induced autophagy and lysosomal biogenesis. Whereas TE activated PERK, which mediated calcineurin dephosphorylation of TFEB/TFE3, IRE1α was activated and led to inactivation of STAT3, which further enhanced autophagy and lysosomal biogenesis. Functionally, knockdown of TFEB or TFE3 impairs TE-induced lysosomal biogenesis and autophagic flux. Furthermore, TE-induced autophagy protects NP cells from oxidative stress to ameliorate intervertebral disc degeneration (IVDD).

CONCLUSIONS

Here, our study showed that TE can induce TFEB/TFE3-dependent lysosomal biogenesis and autophagy via the PERK-calcineurin axis and IRE1α-STAT3 axis. Unlike other agents regulating lysosomal biogenesis and autophagy, TE showed limited cytotoxicity, thereby providing a new direction for therapeutic opportunities to use TE to treat diseases with impaired autophagy-lysosomal pathways, including IVDD.

Injection of Ultra-Purified Stem Cells with Sodium Alginate Reduces Discogenic Pain in a Rat Model

Intervertebral disc (IVD) degeneration is a major cause of low back pain. However, treatments directly approaching the etiology of IVD degeneration and discogenic pain are not yet established. We previously demonstrated that intradiscal implantation of cell-free bioresorbable ultra-purified alginate (UPAL) gel promotes tissue repair and reduces discogenic pain, and a combination of ultra-purified, Good Manufacturing Practice (GMP)-compliant, human bone marrow mesenchymal stem cells (rapidly expanding clones; RECs), and the UPAL gel increasingly enhanced IVD regeneration in animal models. This study investigated the therapeutic efficacy of injecting a mixture of REC and UPAL non-gelling solution for discogenic pain and IVD regeneration in a rat caudal nucleus pulposus punch model. REC and UPAL mixture and UPAL alone suppressed not only the expression of TNF-α, IL-6, and TrkA (p < 0.01, respectively), but also IVD degeneration and nociceptive behavior compared to punching alone (p < 0.01, respectively). Furthermore, REC and UPAL mixture suppressed these expression levels and nociceptive behavior compared to UPAL alone (p < 0.01, respectively). These results suggest that this minimally invasive treatment strategy with a single injection may be applied to treat discogenic pain and as a regenerative therapy.

Celecoxib activates autophagy by inhibiting the mTOR signaling pathway and prevents apoptosis in nucleus pulposus cells

BACKGROUND

Intervertebral disc degeneration results from a variety of etiologies, including inflammation and aging. Degenerated intervertebral discs feature down-regulated extracellular matrix synthesis, resulting in losing their ability to retain water and absorb compression. Celecoxib is a well-known selective cyclooxygenase-2 inhibitor for treating arthritis and relieving pain. Nevertheless, the mechanism of Celecoxib for treating inflammation-related intervertebral disc degeneration has not yet been clarified.

METHOD

Protein synthesis was analyzed by western blot. Fluorescent probes DCFH-DA and MitoSox Red detected reactive oxygen species and were measured by flow cytometry. The activity of the kinase pathway was evaluated by protein phosphorylation. Autophagy was monitored by mRFP-GFP-LC3 transfection and LC3 analysis. Mitochondrial apoptotic proteins were analyzed by western blot and cell membrane integrity was measured by flow cytometry. The autophagic gene was silenced by siRNA.

RESULTS

In this study, interleukin-1β stimulation reduced the synthesis of aggrecan, type I and II collagen and caused excessive production of reactive oxygen species. We looked for a therapeutic window of Celecoxib for nucleus pulposus cells to regain extracellular matrix synthesis and reduce oxidative stress. To look into nucleus pulposus cells in response to stimuli, enhancement of autophagy was achieved by Celecoxib, confirmed by mRFP-GFP-LC3 transfection and LC3 analysis. The mammalian target of rapamycin and a panel of downstream proteins responded to Celecoxib and propelled autophagy machinery to stabilize homeostasis. Ultimately, inhibition of autophagy by silencing autophagy protein 5 disrupted the protective effects of Celecoxib, culminating in apoptosis.

CONCLUSION

In summary, we have demonstrated a new use for the old drug Celecoxib that treats intervertebral disc degeneration by enhancing autophagy in nucleus pulposus cells and opening a door for treating other degenerative diseases.

The impact of matrix age on intervertebral disc regeneration

With the lack of effective treatments for low back pain, the use of extracellular matrix (ECM)-based biomaterials have emerged with undeniable promise for IVD regeneration. Decellularized scaffolds can recreate an ideal microenvironment inducing tissue remodeling and repair. In particular, fetal tissues have a superior regenerative capacity given their ECM composition. In line with this, we unraveled age-associated alterations of the nucleus pulposus (NP) matrisome. Thus, the aim of the present work was to evaluate the impact of ECM donor age on IVD de/regeneration. Accordingly, we optimized an SDS (0.1 %, 1 h)-based decellularization protocol that preserves ECM cues in bovine NPs from different ages. After repopulation with adult NP cells, younger matrices showed the highest repopulation efficiency. Most importantly, cells seeded on younger scaffolds produced healthy ECM proteins suggesting an increased capacity to restore a functional IVD microenvironment. In vivo, only fetal matrices decreased neovessel formation, showing an anti-angiogenic potential. Our findings demonstrate that ECM donor age has a strong influence on angiogenesis and ECM de novo synthesis, opening new avenues for novel therapeutic strategies for the IVD. Additionally, more appropriate 3D models to study age-associated IVD pathology were unveiled.

Study on swelling, compression property and degradation stability of PVA composite hydrogels for artificial nucleus pulposus

Artificial nucleus pulposus (ANP) replacement as an alternative to the treatment of cervical spondylosis aims to relieve pain and restore the normal cervical motion. In this study, the PVA/PVP and PVA/Pectin composite hydrogels (CH)s with different concentrations were prepared by the freezing-thawing process, and their performances were tested. The effect of different concentrations on both kinds of PVA CHs were evaluated and analysed. The results demonstrated that both kinds of CHs had good swelling property (¿190%), compressive stress-strain characteristic response and stable performance, and they were not easy to degrade (¡9%). The elastic modulus of the PVA/PVP CH was close to that of nucleus pulposus prosthesis, and the weight loss ratio of the PVA/PVP CH was lower than that of PVA/Pectin CH under load condition. Further, the experimental results showed that the PVA/PVP CH with 15 wt% solute and 1 wt% PVP content had the best comprehensive performance, which may provide significant advantages for use in future clinical application in replacing nucleus pulposus.

[Visual acupotomy intervention mitigates pain reaction by improving intervertebral disc degeneration and inhibiting apoptosis of nucleus pulposus cells in rabbits with cervical spondylosis]

OBJECTIVE

To investigate the effect of visual acupotomy intervention on intervertebral disc degeneration, nucleus pulposus cell apoptosis and expression of apoptosis related proteins in rabbits with cervical spondylosis (CS), so as to explore its mechanism underlying improvement of CS.

METHODS

A total of 48 male New Zealand rabbits were randomly divided into blank control, model, acupotomy and medication (meloxicam) groups, with 12 rabbits in each group. The neck type CS model was established by forcing the rabbit to make a neck flexion for 5 hours in a restrained chamber, once daily for 12 weeks. Rabbits of the medication group received an intramuscular injection of meloxicam (0.35 mg/kg), once daily for 4 consecutive weeks, and those of the acupotomy group received ultrasound-guided acupotomy intervention, once a week for 4 weeks. The pain threshold (PT) was measured by using a VonFrey electronic pain detector. The levels of prostaglandin E2 (PGE2), 5-hydroxytryptamine (5-HT) and substance P (SP) in serum were detected by ELISA. The severity of intervertebral disc degeneration was observed by using magnetic resonance imaging (MRI) and given scores in accordance with Suzuki's and colleague's "new classification system of cervical disk degeneration". The apoptosis of nucleus pulposus cells was analyzed by TUNEL staining. The protein expression levels of apoptosis-related protein Fas, cysteinyl aspartate-specific protease-3 (Caspase-3), B-cell lymphoma-2 asso-ciated X protein (Bax) and B-cell lymphoma-2 protein (Bcl-2) were measured by Western blot.

RESULTS

Compared with the blank control group, the PT and Bcl-2 expression and MRI score were significantly down-regulated (P<0.01, P<0.001), whereas the contents of serum PGE2, 5-HT and SP, ratios of TUNEL-positive cells, and expression of Fas, Caspase-3 and Bax were considerably up-regulated (P<0.001, P<0.05, P<0.01) in the model group. In contrast to the model group, both the medication and acupotomy groups had an obvious increase in the levels of PT and Bcl-2 expression and MRI score (P<0.05, P<0.01), and a significant decrease in the contents of serum PGE2, 5-HT, SP, ratios of TUNEL-positive cells, and expression of Fas, Caspase-3 and Bax proteins (P<0.05). No significant differences were found between the medication and acupotomy groups in all the indexes mentioned above (P>0.05).

CONCLUSION

Visual acupotomy intervention can mitigate the pain state of CS rabbits, which may be related to its functions in improving the intervertebral disc degeneration, reducing inflammatory reactions and apoptosis of nucleus pulposus cells.

[Comparative study of two elastic fixation systems in single-segment lumbar disc herniation surgery for nucleus pulposus extraction]

OBJECTIVE

To investigate the clinical application of two elastic pedicle internal fixation systems in single-segment lumbar disc herniation fenestration.

METHODS

A retrospective analysis of 64 patients with lumbar intervertebral disc herniation treated by surgery from June 2019 to March 2021. According to the different elastic fixation systems placed during the operation, the patients were divided into ordinary pedicle screw elastic rod link group (elastic rod group) and a special elastic pedicle screw rigid rod fixed connection group (elastic screw group). There were 33 cases in the elastic rod group, including 18 males and 15 females, aged from 30 to 69 years old with an average of(49.18±10.23) years old;and 31 cases in the elastic screw group, including 16 males and 15 females, aged from 32 to 68 with an average of (49.81±9.24) years old. The operation time, intraoperative blood loss, postoperative wound drainage, and postoperative landing time of the two groups were recorded separately. The visual analogue scale (VAS), Japanese Orthopaedic Association (JOA) score, and Oswestry Disability Index (ODI) were compared before and 3, 12 months after operation. The height of the adjacent vertebral space on the lateral DR film before and 12 months after the operation was measured. The clinical efficacy was evaluated by Macnab standard.

RESULTS

All the patients successfully completed the operation, and were followed up. The operation time, intraoperative blood loss, postoperative wound drainage and postoperative landing time in the elastic rod group were(63.73±12.01) min, (89.55±16.07) ml, (81.67±16.00) ml, (3.45±0.75) d , while in the elastic nail group was (62.96±11.54) min, (88.35±17.14) ml, (82.29±15.40) ml, (3.29±0.78) d, the difference was not statistically significant. The symptoms of low back pain and lower extremity numbness were significantly improved in all patients after operation. There was no significant difference in VAS, JOA score and ODI between the two groups before and after surgery (P>0.05). At 12 months after operation, there was no significant difference in the height of the adjacent vertebral space between the upper adjacent vertebral body and the same segment before operation(P>0.05), and there was no significant difference between the groups before and after the operation. According to Macnab criteria, the elastic rod group was excellent in 30 cases, good in 2 cases, fair in 1 case, while the elastic nail group was excellent in 29 cases, good in 2 cases, fair in 0 cases, and there was no significant difference(Z=-0.42, P=0.68).

CONCLUSION

In fenestrated nucleus pulposus extraction for lumbar disc herniation, the two elastic pedicle internal fixation systems are equally effective and can be used. The elastic screw internal fixation system has certain advantages when the distance between the two vertebral bodies is short, and the elastic rod cannot be placed or is difficult to be placed, and it is more widely used.

Discovery and Application of Postnatal Nucleus Pulposus Progenitors Essential for Intervertebral Disc Homeostasis and Degeneration

Intervertebral disc degeneration (IDD) results from the dysfunction of nucleus pulposus (NP) cells and the exhaustion of NP progenitors (ProNPs). The cellular applications of NP cells during IDD are currently limited due to the lack of in vivo studies showing whether NP cells are heterogeneous and contain ProNPs throughout postnatal stages. In this study, single-cell RNA sequencing of purified NP cells is used to map four molecularly defined populations and urotensin II receptor (UTS2R)-expressing postnatal ProNPs is identified, which are markedly exhausted during IDD, in mouse and human specimens. The lineage tracing shows that UTS2R⁺ ProNPs preferentially resides in the NP periphery with its niche factor tenascin-C and give rise to functional NP cells. It is also demonstrated that transplanting UTS2R⁺ ProNPs with tenascin-C into injured intervertebral discs attenuate the progression of IDD. The study provides a novel NP cell atlas, identified resident ProNPs with regenerative potential, and revealed promising diagnostic and therapeutic targets for IDD.