IL-1β promotes disc degeneration and inflammation through direct injection of intervertebral disc in a rat lumbar disc herniation model

Silencing DDX3 Attenuates Interleukin-1β-Induced Intervertebral Disc Degeneration Through Inhibiting Pyroptosis

Intervertebral disc degeneration (IVDD) is a common disorder associated with chronic inflammation and cell death. In this study, an IVDD rat model was created through Interleukin-1β (IL-1β) injection. The degeneration of intervertebral disc tissues was assessed using magnetic resonance imaging (MRI), followed by hematoxylin and eosin (H&E) and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining. RNA sequencing was performed to identify differentially expressed genes (DEGs) between the IVDD model and control rats. The expression levels of DEGs (DEAD-box polypeptide 3 (DDX3), lysine-specific demethylase 5D (KDM5D), interferon-induced gene-1 (IFIT1), ribosomal protein S10 (RPS10), tenomodulin (TNMD), and pentraxin 3 (PTX3)) were measured by real-time quantitative polymerase chain reaction (RT-qPCR). The regulatory effect of DDX3 on pyroptosis in IL-1β-treated nucleus pulpous (NP) cells was assessed after transfection with siRNA of DDX3. A total of 601 DEGs were identified from the IVDD model rat, and were abundant in extracellular matrix (ECM) organization, ECM-receptor interaction, and inflammatory pathways, including the PI3K-Akt, TNF, and AMPK signaling pathways. DDX3, KDM5D, and IFIT1 levels were notably elevated, whereas RPS10, TNMD, and PTX3 levels were decreased in the IL-1β-induced IVDD rat model. Moreover, silencing DDX3 promoted cell proliferation and abolished IL-1β-induced cell apoptosis and pyroptosis. This study revealed the role of DDX3 in IVDD pyroptosis, providing potential target for IVDD management.

Biphasic release of betamethasone from an injectable HA hydrogel implant for alleviating lumbar disc herniation induced sciatica

Epidural steroid injection (ESI) is a common therapeutic approach for managing sciatica caused by lumbar disc herniation (LDH). However, the short duration of therapeutic efficacy and the need for repeated injections pose challenges in LDH treatment. The development of a controlled delivery system capable of prolonging the effectiveness of ESI and reducing the frequency of injections, is highly significant in LDH clinical practice. In this study, we utilized a thiol-ene click chemistry to create a series of injectable hyaluronic acid (HA) based release systems loaded with diphasic betamethasone, including betamethasone dipropionate (BD) and betamethasone 21-phosphate disodium (BP) (BD/BP@HA). BD/BP@HA hydrogel implants demonstrated biocompatibility and biodegradability to matched neuronal tissues, avoiding artificial compression following injection. The sustained release of betamethasone from BD/BP@HA hydrogels effectively inhibited both acute and chronic neuroinflammation by suppressing the nuclear factor kappa-B (NF-κB) pathway. In a mouse model of LDH, the epidural administration of BD/BP@HA efficiently alleviated LDH-induced sciatica for at least 10 days by inhibiting the activation of macrophages and microglia in dorsal root ganglion and spinal dorsal horn, respectively. The newly developed HA hydrogels represent a valuable platform for achieving sustained drug release. Additionally, we provide a simple paradigm for fabricating BD/BP@HA for epidural injection, demonstrating greater and sustained efficiency in alleviating LDH-induced sciatica compared to traditional ESI and displaying potentials for clinical translation. This system has the potential to revolutionize drug delivery for co-delivery of both soluble and insoluble drugs, thereby making a significant impact in the pharmaceutical industry. STATEMENT OF SIGNIFICANCE: Lumbar disc herniation (LDH) is a common degenerative disorder leading to sciatica and spine surgery. Although epidural steroid injection (ESI) is routinely used to alleviate sciatica, the efficacy is short and repeated injections are required. There remains challenging to prolong the efficacy of ESI. Herein, an injectable hyaluronic acid (HA) hydrogel implant by crosslinking acrylated-modified HA (HA-A) with thiol-modified HA (HA-SH) was designed to achieve a biphasic release of betamethasone. The hydrogel showed biocompatibility and biodegradability to match neuronal tissues. Notably, compared to traditional ESI, the hydrogel better alleviated sciatica in vivo by synergistically inhibiting the neuroinflammation in central and peripheral nervous systems. We anticipate the injectable HA hydrogel implant has the potential for clinical translation in treating LDH-induced sciatica.

The clinicopathologic and immunohistochemical features of 60 cutaneous glomus tumor: a retrospective case series study

BACKGROUND

Glomus Tumor (GT) are benign neoplasms that originate from mesenchymal cells. It presents as tenderness and cold allodynia in the digits, especially in the subungual region. There are a few studies that investigated the mechanism of pain.

OBJECTIVES

To analyze the clinical-pathologic characteristics of GT and to identify the expression of IL-1β, IL-6, and CGRP in it, further, to explore the possible mechanism of pain.

METHODS

The clinical and pathological data of 60 GT patients were retrospectively analyzed. Tissue microarrays and immunohistochemistry were used to measure the expression of IL-1β, IL-6 and CGRP.

RESULTS

GT is more common in females and the ratio of male to was near to 1:2, mostly in middle-aged people. It often occurs in fingertips, especially the thumbs. Patients often present with spontaneous pain, tenderness, and cold hypersensitivity. Both the two pain mediators IL-1β and IL-6 were highly expressed in GT cells of patients with and without cold hypersensitivity. While CGRP was not expressed in GT.

STUDY LIMITATIONS

Low sample size and further research is needed to explore the specific mechanism.

CONCLUSIONS

IL-1β and IL-6 were highly expressed in GT cells, suggesting that IL-1β and IL-6 have certain nociceptive roles in GT. In the 4 patients with cold intolerance, the intensity of IL-1β and IL-6 staining was also strong, suggesting that they may not play a role in the cold hypersensitivity. However, since there are only 4 patients with cold intolerance, it's necessary to conduct further in-depth research using a larger sample size. The specific role of CGRP in GT has not been found yet.

Palmitic acid and trans-4-hydroxy-3-methoxycinnamate, the active ingredients of Yaobishu formula, reduce inflammation and pain by regulating gut microbiota and metabolic changes after lumbar disc herniation to activate autophagy and the Wnt/β-catenin pathway

The imbalance in gut microbiota triggers an inflammatory response that spreads from the gut to the discs and is associated with lumbar disc herniation (LDH). In this study, we investigated the mechanism of palmitic acid (PA) and trans-4-hydroxy-3-methoxycinnamic acid (THMC) on microbiota, metabolic homeostasis, and autophagy after LDH. The LDH rat model was established by puncturing the exposed intervertebral disc. 16S rDNA was used to assess the gut microbiome composition. The microbial metabolites were analyzed by UPLC-MS. The mechanism of PA and THMC in LDH was explored by fecal microbiota transplantation (FMT). We found that Yaobishu, PA, THMC, and the positive control drug Celebrex attenuated intervertebral disc damage in LDH rats and downregulated TRPV1, IL-1β, and IL-18 expression. In addition, Yaobishu reduced Oscillospirales and Ruminococcaceae abundances after LDH. PA increased Bacilli's abundance while decreasing Negativicutes and Ruminococcaceae abundances. Metabolomics showed that Yaobishu increased 2-hexanone, methyl isobutyl ketone, 2-methylpentan-3-one, and nonadecanoic acid levels but decreased pantetheine and urocanate levels. PA and THMC reduced uridine and urocanate levels. Yaobishu, PA, and THMC activated autophagy and the Wnt/β-catenin pathway in LDH rats. Moreover, antibiotics abrogated these effects. FMT-PA and FMT-THMC activated autophagy and decreased IL-1β, IL-18, Wnt1, β-catenin, and TRPV1 expression. FMT-PA and FMT-THMC partially reversed the effects of 3-MA. Taken together, our data suggest that Yaobishu, PA, and THMC relieve inflammation and pain by remodeling the gut microbiota and restoring metabolic homeostasis after LDH to activate autophagy and the Wnt/β-catenin pathway, which provide a new therapeutic target for LDH in the clinic.

Protectin D1 ameliorates non-compressive lumbar disc herniation through SIRT1-mediated CGRP signaling

Background. Neuro-inflammatory response promotes the initiation and sustenance of lumbar disc herniation (LDH). Protectin D1 (PD1), as a new type of specialized pro-resolving mediator (SPM), can improve the prognosis of various inflammatory diseases. Recent studies have shown that over representation of calcitonin gene-related peptides (CGRP) may activate nociceptive signaling following nerve injury. Silent information regulator 1 (SIRT1) is ubiquitously expressed in the dorsal horn of the spinal cord and plays a role in the pathogenesis of LDH. In this study, we investigated the analgesic effects of PD1 and elucidated the impact of neurogenic inflammation in the pathogenesis of neuropathic pain induced by non-compressive lumbar disc herniation (NCLDH) in a rat model. Methods. NCLDH models were established by applying protruding autologous nucleus pulposus to the L5 Dorsal root ganglion (DRG). PD1, SIRT1 antagonist or agonist, CGRP or antagonist were administered as daily intrathecal injections for three consecutive days postoperatively. Behavioral tests were conducted to assess mechanical and thermal hyperalgesia. The ipsilateral lumbar (L4-6) segment of the spinal dorsal horn was isolated for further analysis. Alterations in the release of SIRT1 and CGRP were explored using western blot and immunofluorescence. Results. Application of protruded nucleus (NP) materials to the DRG induced mechanical and thermal allodynia symptoms, and deregulated the expression of pro-inflammatory and anti-inflammatory cytokines in rats. Intrathecal delivery of PD1 significantly reversed the NCLDH-induced imbalance in neuro-inflammatory response and alleviated the symptoms of mechanical and thermal hyperalgesia. In addition, NP application to the DGRs resulted the spinal upregulation of CGRP and SIRT1 expression, which was almost restored by intrathecal injection of PD1 in a dose-dependent manner. SIRT1 antagonist or agonist and CGRP or antagonist treatment further confirmed the result. Conclusion. Our findings indicate PD1 has a potent analgesic effect, and can modulate neuro-inflammation by regulating SIRT1-mediated CGRP signaling in NCLDH.

Tension-activated nanofiber patches delivering an anti-inflammatory drug improve repair in a goat intervertebral disc herniation model

Conventional microdiscectomy treatment for intervertebral disc herniation alleviates pain but does not repair the annulus fibrosus, resulting in a high incidence of recurrent herniation and persistent dysfunction. The lack of repair and the acute inflammation that arise after injury can further compromise the disc and result in disc-wide degeneration in the long term. To address this clinical need, we developed tension-activated repair patches (TARPs) for annulus fibrosus repair and local delivery of the anti-inflammatory factor anakinra (a recombinant interleukin-1 receptor antagonist). TARPs transmit physiologic strain to mechanically activated microcapsules embedded within the patch, which release encapsulated bioactive molecules in direct response to spinal loading. Mechanically activated microcapsules carrying anakinra were loaded into TARPs, and the effects of TARP-mediated annular repair and anakinra delivery were evaluated in a goat model of annular injury in the cervical spine. TARPs integrated with native tissue and provided structural reinforcement at the injury site that prevented aberrant disc-wide remodeling resulting from detensioning of the annular fibrosus. The delivery of anakinra by TARP implantation increased matrix deposition and retention at the injury site and improved maintenance of disc extracellular matrix. Anakinra delivery additionally attenuated the inflammatory response associated with TARP implantation, decreasing osteolysis in adjacent vertebrae and preserving disc cellularity and matrix organization throughout the annulus fibrosus. These results demonstrate the therapeutic potential of TARPs for the treatment of intervertebral disc herniation.

Enhanced Intervertebral Disc Repair via Genetically Engineered Mesenchymal Stem Cells with Tetracycline Regulatory System

The therapeutic potential of Mesenchymal stem cells (MSCs) for the treatment of Intervertebral disc (IVD) degeneration can be enhanced by amplifying specific cytokines and proteins. This study aimed to investigate the therapeutic potential of tetracycline-off system-engineered tonsil-derived mesenchymal stem cells (ToMSC-Tetoff-TGFβ1-IGF1-BMP7) for treating intervertebral disc (IVD) degeneration. ToMSCs were isolated from a tonsillectomy patient and genetically modified with four distinct plasmids via CRISPR/Cas9-mediated knock-in gene editing. Transgene expression was confirmed through immunofluorescence, western blots, and an enzyme-linked immunosorbent assay for transforming growth factor beta 1 (TGFβ1) protein secretion, and the effect of MSC-TetOff-TGFβ1-IGF1-BMP7 on disc injury was assessed in a rat model. The ToMSC-Tetoff-TGFβ1-IGF1-BMP7 treatment exhibited superior therapeutic effects compared to ToMSC-TGFβ1, and ToMSC-SDF1α implantation groups, stimulating the regeneration of nucleus pulposus (NP) cells crucial for IVD. The treatment showed potential to restore the structural integrity of the extracellular matrix (ECM) by upregulating key molecules such as aggrecan and type II collagen. It also exhibited anti-inflammatory properties and reduced pain-inducing neuropeptides. ToMSC-Tetoff-TGFβ1-IGF1-BMP7 holds promise as a novel treatment for IVD degeneration. It appears to promote NP cell regeneration, restore ECM structure, suppress inflammation, and reduce pain. However, more research and clinical trials are required to confirm its therapeutic potential.

Pure platelet-rich plasma promotes semaphorin-3A expression: a novel insight to ameliorate intervertebral disk degeneration in vitro

INTRODUCTION

Intervertebral disk degeneration (IVDD) can be effectively treated using platelet-rich plasma (PRP). While the exact process is fully understood, it is believed that using pure PRP (P-PRP) without leukocytes is a better option for preventing IVDD. Semaphorin-3A (Sema3A), an inhibitor of angiogenesis and innervation, is essential for preserving IVDD's homeostasis. Whether PRP prevents IVDD by modifying Sema3A has yet to receive much research. This work aims to clarify how P-PRP affects Sema3A when IVDD develops in vitro.

METHODS

Nucleus pulposus cells (NPCs) isolated from 8-week-old male Sprague-Dawley rats were exposed to 10 ng/ml IL-1β and then treated with P-PRP or leukocyte platelet-rich plasma (L-PRP) in vitro, followed by measuring cell proliferation, apoptosis and microstructures, inflammatory gene and Sema3A expression, as well as anabolic and catabolic protein expression by immunostaining, quantitative real-time polymerase chain reaction (qPCR), western blot, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

In comparison with L-PRP, P-PRP had a higher concentration of growth factors but a lower concentration of inflammatory substances. P-PRP increased the proliferation of NPCs, while IL-1 relieved the amount of apoptosis due to its intervention. Anabolic genes, aggrecan, and collagen II had higher expression levels. MMP-3 and ADAMTS-4, two catabolic or inflammatory genes, showed lower expression levels. Sema3A activity was enhanced after P-PRP injection, whereas CD31 and NF200 expression levels were suppressed.

CONCLUSIONS

P-PRP enhanced the performance of NPCs in IVDD by modifying the NF-κB signaling pathway and encouraging Sema3A expression, which may offer new therapy options for IVDD.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

The findings provide a new therapeutic target for the treatment of IVDD and show a novel light on the probable mechanism of PRP and the function of Sema3A in the progression of IVDD.

Multifunctional annulus fibrosus matrix prevents disc-related pain via inhibiting neuroinflammation and sensitization

Chronic low back pain mainly attributed to intervertebral disc (IVD) degeneration. Endogenous damage-associated molecular patterns (DAMPs) in the injured IVD, particularly mitochondria-derived nucleic acid molecules (CpG DNA), play a primary role in the inflammatory responses in macrophages. M1-type macrophages form a chronic inflammatory microenvironment by releasing pro-inflammatory factors and nerve growth factor (NGF) that induce nerve growth into the inner annulus fibrosus, resulting in persistent hyperalgesia. We fabricated an amphiphilic polycarbonate that naturally forms cationic nanoparticles (cNP) in aqueous solutions, with the hydrophobic core loaded with TrkA-IN-1, an antagonist against the NGF receptor (TrkA). The drug delivery nanoparticles were denoted as TI-cNP. TrkA-IN-1 and TI-cNP were added to the decellularized annulus fibrosus matrix (DAF) hydrogel to form hybrid hydrogels, denoted as TI-DAF and TI-cNP-DAF, respectively. As a result, TrkA-IN-1 showed a delayed release profile both in TI-DAF and TI-cNP-DAF. Each mole of cNP could bind approximately 3 mol of CpG DNA to inhibit inflammation. cNP-DAF and TI-cNP-DAF significantly inhibited the M1 phenotype induced by CpG DNA. TI-DAF and TI-cNP-DAF reduced neurite branching and axon length, and inhibited the expression of neurogenic mediators (CGRP and substance P) in the presence of NGF. Besides, TI-cNP-DAF relieved mechanical hyperalgesia, reduced CGRP and substance P expression in the dorsal root ganglion, and downregulated GFAP and c-FOS signaling in the spinal cord in the rat disc herniation model. Summarily, TI-cNP-DAF, a novel composite IVD hydrogel, efficiently mediated the inflammatory environment, inhibited nerve ingrowth and sensitization, and could be clinically applied for treating discogenic pain. STATEMENT OF SIGNIFICANCE: Discogenic lower back pain, related to intervertebral disc degeneration (IDD), imposes a tremendous health and economic burden globally. M1-type macrophages release pro-inflammatory factors and nerve growth factor (NGF) that induce nerve growth into the inner annulus fibrosus, resulting in persistent hyperalgesia and discogenic pain. Reconstructing matrix integrity and modulating the inflammatory microenvironment are promising strategies for preventing the ingrowth and activation of neurites. The TI-cNP-DAF hydrogel recovers tissue integrity, alleviates inflammation, and delivers the TrkA antagonist to inhibit the activity of NGF, thus restraining hyperinnervation and nociceptive input. Due to its simple production process, injectability, and acellular strategy, the hydrogel is operable and holds great potential for treating discogenic lower back pain.

Effective Modulation of Inflammation and Oxidative Stress for Enhanced Regeneration of Intervertebral Discs Using 3D Porous Hybrid Protein Nanoscaffold

Degeneration of fibrocartilaginous tissues is often associated with complex pro-inflammatory factors. These include reactive oxygen species (ROS), cell-free nucleic acids (cf-NAs), and epigenetic changes in immune cells. To effectively control this complex inflammatory signaling, it developed an all-in-one nanoscaffold-based 3D porous hybrid protein (3D-PHP) self-therapeutic strategy for treating intervertebral disc (IVD) degeneration. The 3D-PHP nanoscaffold is synthesized by introducing a novel nanomaterial-templated protein assembly (NTPA) strategy. 3D-PHP nanoscaffolds that avoid covalent modification of proteins demonstrate inflammatory stimuli-responsive drug release, disc-mimetic stiffness, and excellent biodegradability. Enzyme-like 2D nanosheets incorporated into nanoscaffolds further enabled robust scavenging of ROS and cf-NAs, reducing inflammation and enhancing the survival of disc cells under inflammatory stress in vitro. Implantation of 3D-PHP nanoscaffolds loaded with bromodomain extraterminal inhibitor (BETi) into a rat nucleotomy disc injury model effectively suppressed inflammation in vivo, thus promoting restoration of the extracellular matrix (ECM). The resulting regeneration of disc tissue facilitated long-term pain reduction. Therefore, self-therapeutic and epigenetic modulator-encapsulated hybrid protein nanoscaffold shows great promise as a novel approach to restore dysregulated inflammatory signaling and treat degenerative fibrocartilaginous diseases, including disc injuries, providing hope and relief to patients worldwide.

Manipulation of osteogenic and adipogenic differentiation of human degenerative disc and ligamentum flavum derived progenitor cells using IL-1β, IL-19, and IL-20

PURPOSE

To elucidate whether pro-inflammatory cytokines might influence the commitment of intervertebral disc (IVD)- and ligamentum flavum (LF)-derived progenitor cells toward either osteogenesis or adipogenesis, specifically Interleukin-1β (IL-1β), IL-19, and IL-20.

METHODS

Sixty patients with degenerative spondylolisthesis and lumbar or lumbosacral spinal stenosis were included in the study. Injuries to the spine, infections, and benign or malignant tumors were excluded. From nine patient samples, IVD- and LF-derived cells were isolated after primary culture, and two clinical samples were excluded due to mycoplasma infection. The effects of IL-1β, IL-19, as well as IL-20 in regulating osteogenic and adipogenic differentiation in vitro were investigated.

RESULTS

Primary IVD- and LF-derived cells were found to have a similar cell morphology and profile of surface markers (CD44, CD90, and CD105) as placenta-derived mesenchymal stem cells (MSCs). Primary IVD/LF cells have a high capacity to differentiate into osteocytes and adipocytes. IL-19 had a tendency to promote adipogenesis. IL-20 inhibited osteogenesis and promoted adipogenesis; IL-1β promoted osteogenesis but inhibited adipogenesis.

CONCLUSION

IL-1β, IL-19, and IL-20 impact the adipogenic and osteogenic differentiation of IVD-derived and LF-derived cells. Modulating the expression of IL-1β, IL-19, and IL-20 provides a potential avenue for controlling cell differentiation of IVD- and LF-derived cells, which might have beneficial effect for degenerative spondylolisthesis and spinal stenosis.

Programmable DNA hydrogel provides suitable microenvironment for enhancing autophagy-based therapies in intervertebral disc degeneration treatment

The pathogenesis of intervertebral disc degeneration (IVDD) is attributed to metabolic dysregulation within the extracellular matrix and heightened apoptosis of nucleus pulposus cells (NPC). Therefore, a potential therapeutic strategy for managing IVDD involves the reestablishment of metabolic equilibrium within the extracellular matrix and the suppression of excessive myeloid cell apoptosis. The microRNA, miR-5590, displays marked differential expression in degenerative nucleus pulposus (NP) tissues and exerts a direct influence on the regulation of DDX5 expression. This, in turn, modulates mammalian target of rapamycin (mTOR) phosphorylation, thereby impacting autophagy and apoptosis. However, ensuring the smooth delivery of miRNA to a specific injury site poses a significant challenge. To address this issue, a multifunctional DNA hydrogel was developed and subsequently loaded with miR-5590 via spherical nucleic acids (SNAs) for the treatment of IVDD. The hydrogel, which exhibits versatility, has the potential to be administered through injection at the site of injury, resulting in a consistent and prolonged release of miR-5590. This leads to the creation of a genetic microenvironment within the NP, which triggers the onset of autophagy in NPCs and subsequently suppresses apoptosis. As a result, this process regulates the metabolic equilibrium within the extracellular matrix, thereby impeding the in vitro and in vivo progression of IVDD. The amalgamation of miRNAs and biomaterials offers a promising therapeutic strategy for the management of IVDD in clinical settings.

Intervertebral disc degeneration and inflammatory microenvironment: expression, pathology, and therapeutic strategies

BACKGROUND

Intervertebral disc degeneration (IDD) is a leading cause of low back pain (LBP), posing a significant socioeconomic burden. Recent studies highlight the crucial role of inflammatory microenvironment in IDD progression.

METHOD

A keyword-based search was performed using the PubMed database for published articles.

RESULTS AND CONCLUSIONS

Dysregulated expression of inflammatory cytokines disrupts intervertebral disc (IVD) homeostasis, causing atrophy, fibrosis, and phenotypic changes in nucleus pulposus cells. Modulating the inflammatory microenvironment and restoring cytokine balance hold promise for IVD repair and regeneration. This comprehensive review systematically examines the expression regulation, pathological effects, therapeutic strategies, and future challenges associated with the inflammatory microenvironment and relevant cytokines in IDD. Key inflammatory cytokines, including interleukins (IL), tumor necrosis factor-alpha (TNF-α), and chemokines, exhibit significant pathological effects in IDD. Furthermore, major therapeutic modalities such as chemical antagonists, biologics, plant extracts, and gene transcription therapies are introduced to control and ameliorate the inflammatory microenvironment. These approaches provide valuable insights for identifying potential targets in future anti-inflammatory treatments for IDD.

Kartogenin-enhanced dynamic hydrogel ameliorates intervertebral disc degeneration via restoration of local redox homeostasis

INTRODUCTION

Over-activation of oxidative stress due to impaired antioxidant functions in nucleus pulpous (NP) has been identified as a key factor contributing to intervertebral disc degeneration (IVDD). While Kartogenin (KGN) has previously demonstrated antioxidant properties on articular cartilage against osteoarthritis, its effects on NP degeneration have yet to be fully understood.

OBJECTIVES

This study aimed to investigate the protective effects of KGN on nucleus pulpous cells (NPCs) against an inflammatory environment induced by interleukin (IL)-1β, as well as to explore the therapeutic potential of KGN-enhanced dynamic hydrogel in preventing IVDD.

METHODS

NPCs were isolated from rat caudal IVDs and subjected to treatment with KGN at varying concentrations (ranging from 0.01 to 1 ​μM) in the presence of IL-1β. The expression of extracellular matrix (ECM) anabolism markers was quantitatively assessed at both the mRNA and protein levels. Additionally, intracellular reactive oxygen species and antioxidant enzyme expression were evaluated, along with the role of nuclear factor erythroid 2-related factor 2 (NRF2). Based on these findings, a dynamic self-healing hydrogel loaded with KGN was developed through interconnecting networks. Subsequently, KGN-enhanced dynamic hydrogel was administered into rat caudal IVDs that had undergone puncture injury, followed by radiographic analysis and immunohistochemical staining to evaluate the therapeutic efficacy.

RESULTS

In vitro treatments utilizing KGN were observed to maintain ECM synthesis and inhibit catabolic activities in IL-1β-stimulated NPCs. The mechanism behind this protective effect of KGN on NPCs was found to involve the asctivation of NRF2 and downstream antioxidant enzymes, including glutathione peroxidase 1 and heme oxygenase 1. This was further supported by the loss of both antioxidant and anabolic effects upon pharmacological inhibition of NRF2. Furthermore, a self-healing hydrogel was developed and loaded with KGN to achieve localized and sustained release of the compound. The injection of KGN-enhanced hydrogel effectively ameliorated the degradation of NP ECM and mitigated inflammation in a rat model of puncture-induced IVDD.

CONCLUSIONS

Our results indicate that KGN exhibits potential as a therapeutic agent for NP degeneration, and that KGN-enhanced dynamic hydrogel represents a novel approach for treating IVDD by restoring redox homeostasis in NP.The translational potential of this article: The dysregulation of oxidant and antioxidant balance has been shown to impede the repair and regeneration of NP, thereby hastening the progression of IVDD following injury. The present investigation has demonstrated that the sustained release of KGN promotes the synthesis of ECM in vitro and mitigates the progression of IVDD in vivo by restoring redox equilibrium, thereby presenting a novel therapeutic candidate based on the antioxidant properties of KGN for the treatment of IVDD.

Constructing intervertebral disc degeneration animal model: A review of current models

Low back pain is one of the top disorders that leads to disability and affects disability-adjusted life years (DALY) globally. Intervertebral disc degeneration (IDD) and subsequent discogenic pain composed major causes of low back pain. Recent studies have identified several important risk factors contributing to IDD's development, such as inflammation, mechanical imbalance, and aging. Based on these etiology findings, three categories of animal models for inducing IDD are developed: the damage-induced model, the mechanical model, and the spontaneous model. These models are essential measures in studying the natural history of IDD and finding the possible therapeutic target against IDD. In this review, we will discuss the technical details of these models, the duration between model establishment, the occurrence of observable degeneration, and the potential in different study ranges. In promoting future research for IDD, each animal model should examine its concordance with natural IDD pathogenesis in humans. We hope this review can enhance the understanding and proper use of multiple animal models, which may attract more attention to this disease and contribute to translation research.

Regulatory Effect of Inflammatory Mediators in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is a major contributor to back, neck, and radicular pain. It is related to changes in tissue structure and function, including the breakdown of the extracellular matrix (ECM), aging, apoptosis of the nucleus pulposus, and biomechanical tissue impairment. Recently, an increasing number of studies have demonstrated that inflammatory mediators play a crucial role in IDD, and they are being explored as potential treatment targets for IDD and associated disorders. For example, interleukins (IL), tumour necrosis factor-α (TNF-α), chemokines, and inflammasomes have all been linked to the pathophysiology of IDD. These inflammatory mediators are found in high concentrations in intervertebral disc (IVD) tissues and cells and are associated with the severity of LBP and IDD. It is feasible to reduce the production of these proinflammatory mediators and develop a novel therapy for IDD, which will be a hotspot of future research. In this review, the effects of inflammatory mediators in IDD were described.

Epigenetic Changes within the Annulus Fibrosus by DNA Methylation in Rat Intervertebral Disc Degeneration Model

Intervertebral disc degeneration (IDD) is an age-dependent progressive spinal disease that causes chronic back or neck pain. Although aging has long been presented as the main risk factor, the exact cause is not fully known. DNA methylation is associated with chronic pain, suggesting that epigenetic modulation may ameliorate disc degeneration. We examined histological changes in the DNA methylation within the discs and their association with pain-related transient receptor potential vanilloid subtype 1 (TrpV1) expression in rats subjected to IDD. Epigenetic markers (5-hydroxymethylcytosine (5hmC), 5-methylcytosine (5Mc)), DNA methyltransferases (DNMTs), and Ten-eleven translocations (Tets) were analyzed using immunohistochemistry, real-time PCR, and DNA dot-blot following IDD. Results revealed high 5mC levels in the annulus fibrosus (AF) region within the disc after IDD and an association with TrpV1 expression. DNMT1 is mainly involved in 5mC conversion in degenerated discs. However, 5hmC levels did not differ between groups. A degenerated disc can lead to locomotor defects as assessed by ladder and tail suspension tests, no pain signals in the von Frey test, upregulated matrix metalloproteinase-3, and downregulated aggrecan levels within the disc. Thus, we found that the DNA methylation status in the AF region of the disc was mainly changed after IDD and associated with aberrant TrpV1 expression in degenerated discs.

The role of nerve fibers and their neurotransmitters in regulating intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) has been the major contributor to chronic lower back pain (LBP). Abnormal apoptosis, senescence, and pyroptosis of IVD cells, extracellular matrix (ECM) degradation, and infiltration of immune cells are the major molecular alternations during IVDD. Changes at tissue level frequently occur at advanced IVD tissue. Ectopic ingrowth of nerves within inner annulus fibrosus (AF) and nucleus pulposus (NP) tissue has been considered as the primary cause for LBP. Innervation at IVD tissue mainly included sensory and sympathetic nerves, and many markers for these two types of nerves have been detected since 1940. In fact, in osteoarthritis (OA), beyond pain transmission, the direct regulation of neuropeptides on functions of chondrocytes have attracted researchers' great attention recently. Many physical and pathological similarities between joint and IVD have shed us the light on the neurogenic mechanism involved in IVDD. Here, an overview of the advances in the nervous system within IVD tissue will be performed, with a discussion on in the role of nerve fibers and their neurotransmitters in regulating IVDD. We hope this review can attract more research interest to address neuromodulation and IVDD itself, which will enhance our understanding of the contribution of neuromodulation to the structural changes within IVD tissue and inflammatory responses and will help identify novel therapeutic targets and enable the effective treatment of IVDD disease.

Development of a Novel Inflammatory-Associated Gene Signature and Immune Infiltration Patterns in Intervertebral Disc Degeneration

Background. Both inflammatory factors and immune response play important roles in the pathogenesis of intervertebral disc degeneration (IDD). However, a comprehensive analysis of interaction between inflammatory response-associated genes (IRGs) and immune microenvironment in patients with IDD remains lacking. Hence, the current research is aimed at investigating the correlations between IRG signatures and immune cells in the progression of IDD. Methods. The expression profiles (GSE27494 and GSE41883) and IRGs were downloaded from the Gene Expression Omnibus (GEO) database and Molecular Signature Database (MSigDB), respectively. Weighted gene coexpression network analysis (WGCNA) and differential expression analysis were used to identify the pivotal modules and common differentially expressed genes (DEGs) associated with IDD. Subsequently, we retrieved differentially expressed IRGs (DE-IRGs) by intersecting IRGs and DEGs for enrichment analysis. Next, LASSO regression analyses were performed to screen optimal marker genes for IDD prediction. Additionally, we validated differences DE-IRGs between IDD patients and controls in GSE150408. Finally, the infiltration alteration of immune cells was evaluated by the CIBERSORT, and the correlation between diagnostic markers and infiltrating immune cells was analyzed. Results. A total of 10 upregulated differentially expressed inflammatory genes were identified that were obviously related to progression of IDD. Functional analysis results revealed that DE-IRGs were mainly enriched in signaling pathways TNF, IL-17, NOD-like receptor, and NF-kappa B pathway. A five-gene signature that consisted of IL-1β, LIF, LYN, NAMPT, and SLC7A2 was constructed by the LASSO Cox regression. IL1B, LYN, and NAMPT were further validated as optimal candidate genes in the pathophysiology of IDD. In addition, there was a remarkable immune cell infiltration difference between the healthy and IDD groups. The proportions for dendritic cells activated, mast cells activated, and neutrophils in the IDD group were significantly higher than those in the normal group, while the proportion of some cells was lower than that of the normal group, such as T cell CD4 memory resting, NK cells activated, and macrophage M0. Furthermore, correlation analysis indicated IL-1β, LYN, and NAMPT were closely implicated with immune cell infiltration in IDD development. Conclusions. We explored an association between inflammatory response-associated signature and immune infiltration in IDD and validated that IL-1β, LYN, and NAMPT might serve as biomarkers and therapeutic targets for IDD in the future.

Harpagophytum procumbens Inhibits Iron Overload-Induced Oxidative Stress through Activation of Nrf2 Signaling in a Rat Model of Lumbar Spinal Stenosis

Lumbar spinal stenosis (LSS) is a common degenerative spinal condition in older individuals that causes impaired walking and other disabilities due to severe lower back and leg pain. Ligamentum flavum hypertrophy is a major LSS cause that may result from oxidative stress caused by degenerative cascades, including imbalanced iron homeostasis that leads to excessive reactive oxygen species production. We investigated the effects of Harpagophytum procumbens (HP) on iron-induced oxidative stress associated with LSS pathophysiology. Primary spinal cord neuron cultures were incubated in FeSO₄-containing medium, followed by addition of 50, 100, or 200 μg/mL HP. Cell viability was assessed by CCK-8 and live/dead cell assays and by propidium iodide-live imaging. In an in vivo rat model of LSS, HP were administered at 100, 200, and 400 mg/kg, and disease progression was monitored for up to 3 weeks. We investigated the in vitro and in vivo effects of HP on iron-induced neurotoxicity by immunochemistry, real-time PCR, and flow cytometry. HP exerted neuroprotective effects and enhanced neurite outgrowths of iron-injured rat primary spinal cord neurons in vitro. HP treatment significantly reduced necrotic cell death and improved cells' antioxidative capacity via the NRF2 signaling pathway in iron-treated neurons. At 1 week after HP administration in LSS rats, the inflammatory response and oxidative stress markers were substantially reduced through regulation of excess iron accumulation. Iron that accumulated in the spinal cord underneath the implanted silicone was also regulated by HP administration via NRF2 signaling pathway activation. HP-treated LSS rats showed gradually reduced mechanical allodynia and amelioration of impaired behavior for 3 weeks. We demonstrated that HP administration can maintain iron homeostasis within neurons via activation of NRF2 signaling and can consequently facilitate functional recovery by regulating iron-induced oxidative stress. This fundamentally new strategy holds promise for LSS treatment.

Single-cell assessment of the modulation of macrophage activation by ex vivo intervertebral discs using impedance cytometry

Measurement of macrophage activation and its modulation for immune regulation is of great interest to arrest inflammatory responses associated with degeneration of intervertebral discs that cause chronic back pain, and with transplants that face immune rejection. Due to the phenotypic plasticity of macrophages that serve multiple immune functions, the net disease outcome is determined by a balance of subpopulations with competing functions, highlighting the need for single-cell methods to quantify heterogeneity in their activation phenotypes. However, since macrophage activation can follow several signaling pathways, cytometry after fluorescent staining of markers with antibodies does not often provide dose-dependent information on activation dynamics. We present high throughput single-cell impedance cytometry for multiparametric measurement of biophysical changes to individual macrophages for quantifying activation in a dose and duration dependent manner, without relying on a particular signaling pathway. Impedance phase metrics measured at two frequencies and the electrical diameter from impedance magnitude at lower frequencies are used in tandem to benchmark macrophage activation by degenerated discs against that from lipopolysaccharide stimulation at varying dose and duration levels, so that reversal of the activation state by curcumin can be ascertained. This label-free single-cell measurement method can form the basis for platforms to screen therapies for inflammation, thereby addressing the chronic problem of back pain.

The role of microenvironment in stem cell-based regeneration of intervertebral disc

Regenerative medicine for intervertebral disc (IVD) disease, by utilizing chondrocytes, IVD cells, and stem cells, has progressed to clinical trials in the treatment of back pain, and has been studied in various animal models of disc degeneration in the past decade. Stem cells exist in their natural microenvironment, which provides vital dynamic physical and chemical signals for their survival, proliferation and function. Long-term survival, function and fate of mesenchymal stem cells (MSCs) depend on the microenvironment in which they are transplanted. However, the transplanted MSCs and the endogenous disc cells were influenced by the complicated microenvironment in the degenerating disc with the changes of biochemical and biophysical components. It is important to understand how the MSCs and endogenous disc cells survive and thrive in the harsh microenvironment of the degenerative disc. Furthermore, materials containing stem cells and their natural microenvironment have good clinical effects. However, the implantation of tissue engineering IVD (TE-IVD) cannot provide a complete and dynamic microenvironment for MSCs. IVD graft substitutes may need further improvement to provide the best engineered MSC microenvironment. Additionally, the IVD progenitor cells inside the stem cell niches have been regarded as popular graft cells for IVD regeneration. However, it is still unclear whether actual IVD progenitor cells exist in degenerative spinal conditions. Therefore, the purpose of this review is fourfold: to discuss the presence of endogenous stem cells; to review and summarize the effects of the microenvironment in biological characteristics of MSC, especially those from IVD; to explore the feasibility and prospects of IVD graft substitutes and to elaborate state of the art in the use of MSC transplantation for IVD degeneration in vivo as well as their clinical application.

The Thermosensitive Injectable Celecoxib-Loaded Chitosan Hydrogel for Repairing Postoperative Intervertebral Disc Defect

Percutaneous endoscopic lumbar discectomy has been widely used in clinical practice for lumbar spine diseases. But the postoperative disc re-herniation and inflammation are the main reason for pain recurrence after surgery. The postoperative local defect of the intervertebral disc will lead to the instability of the spine, further aggravating the process of intervertebral disc degeneration. In this work, we successfully synthesized the thermosensitive injectable celecoxib-loaded chitosan hydrogel and investigated its material properties, repair effect, biocompatibility, and histocompatibility in in vitro and in vivo study. In vitro and in vivo, the hydrogel has low toxicity, biodegradability, and good biocompatibility. In an animal experiment, this composite hydrogel can effectively fill local tissue defects to maintain the stability of the spine and delay the process of intervertebral disc degeneration after surgery. These results indicated that this composite hydrogel will be a promising way to treat postoperative intervertebral disc disease in future clinical applications.

Omentin-1 promoted proliferation and ameliorated inflammation, apoptosis, and degeneration in human nucleus pulposus cells

PURPOSE

Intervertebral disc degeneration is an abnormal, cell-mediated process of tissue remodeling, recognized as the principal cause of low back pain affecting 80% of the population worldwide. Inflammatory cytokine, Interleukin-1beta (IL-1β) is involved in the intervertebral disc degeneration (IDD) process, and it is upregulated in degenerated discs. Omentin-1, also known as intelectin-1, is an adipokine with anti-inflammatory, anti-apoptosis, pro-proliferation, and proangiogenic properties in various types of cells. However, little is known about the effects of omentin-1 on human nucleus pulposus cells (HNPCs). This study aims to investigate the effects of omentin-1 on healthy HNPCs regarding proliferation and further investigate the effects of omentin-1 on IL-1β-induced inflammation, apoptosis, and degeneration in HNPCs.

METHODS

Genes and proteins of interest were measured by qRT-PCR, immunoblotting, and immunofluorescence to conduct related experiments. Cell viability (CCK-8), EdU, and mitochondrial membrane potential (JC-1), flow cytometry assays were used to assess proliferation and apoptosis, respectively.

RESULTS

Our study showed that omentin-1 promoted proliferation in normal HNPCs. Furthermore, omentin-1 expression was decreased in IL-1β-treated HNPCs. Omentin-1 protected against IL-1β-induced inflammation, apoptosis, and degeneration in HNPCs in vitro via the activation of the PI3K/Akt signaling pathway.

CONCLUSION

These findings may contribute to understanding the role of omentin-1 in HNPCs and may be a potential therapeutic candidate for intervertebral disc degeneration.

[Effect of resveratrol on high mobility group box-1 protein signaling pathway in cartilage endplate degeneration caused by inflammation]

Objective

To investigate the effect of resveratrol (RES) on inflammation-induced cartilage endplate (CEP) degeneration, and its regulatory mechanism on high mobility group box-1 protein (HMGB1) signaling pathway.

Methods

The intervertebral CEP cells of Sprague Dawley (SD) rats aged 3 weeks were extracted and identified by toluidine blue staining and immunofluorescence staining of rabbit anti-rat collagen type Ⅱ. The cell counting kit 8 (CCK-8) method was used to screen the optimal concentration of RES on intervertebral CEP cells. Gene chip analysis was used to determine the target of RES on intervertebral CEP cells. Interleukin 1β (IL-1β) was used to construct the intervertebral CEP cell degeneration model caused by inflammation and the 7-8-week-old SD rat intervertebral disc degeneration model, and pcDNA3.1-HMGB1 (pcDNA3.1) was used as the control of RES effect. Flow cytometry and TUNEL staining were used to detect the apoptotic rate of intervertebral CEP cells and rat intervertebral disc tissue cells, respectively. ELISA kit was used to detect the content of interleukin 10 (IL-10) and tumor necrosis factor α (TNF-α) in the cell supernatant and rat serum. Western blot was used to detect the expressions of HMGB1, extracellular signal-regulated protein kinase (ERK), phosphorylated ERK (p-ERK), B cell lymphoma/leukemia 2 gene (Bcl-2), and Bcl-2-associated X protein (Bax).

Results

The extracted cells were identified as rat intervertebral CEP cells. CCK-8 method screened out the highest activity of intervertebral CEP cells treated with 30 μmol/L RES. The gene chip analysis confirmed that the HMGB1-ERK signal was the target of RES. Both cell experiments and animal experiments showed that RES treatment can significantly down-regulate the apoptosis rate of intervertebral CEP cells, inhibit the release of TNF-α, and increase the content of IL-10; and down-regulate the expressions of HMGB1, p-ERK, and Bax, and increase Bcl-2; and pcDNA3.1 could partially reverse these effects of RES, and the differences were all significant (P<0.05).

Conclusion

RES can significantly inhibit the apoptosis of intervertebral CEP cells induced by inflammation, which is related to inhibiting the expression of HMGB1.

Senolytics: Eliminating Senescent Cells and Alleviating Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) is the main cause of cervical and lumbar spondylosis. Over the past few years, the relevance between cellular senescence and IVDD has been widely studied, and the senescence-associated secretory phenotype (SASP) produced by senescent cells is found to remodel extracellular matrix (ECM) metabolism and destruct homeostasis. Elimination of senescent cells by senolytics and suppression of SASP production by senomorphics/senostatics are effective strategies to alleviate degenerative diseases including IVDD. Here, we review the involvement of senescence in the process of IVDD; we also discuss the potential of senolytics on eliminating senescent disc cells and alleviating IVDD; finally, we provide a table listing senolytic drugs and small molecules, aiming to propose potential drugs for IVDD therapy in the future.

Is There Any Relationship between Plasma IL-6 and TNF-α Levels and Lumbar Disc Degeneration? A Retrospective Single-Center Study

Intervertebral disc degeneration (IDD) is one of the most common degenerative diseases all over the world. A growing number of studies have proved that large amounts of cytokines are produced during the development of IDD, and the inflammatory responses induced by these cytokines aggravate the occurrence and development of the disc degeneration. In this retrospective single-center study, a total of 182 lumbar spine cases were retrospectively reviewed between July 2020 and October 2021. An appropriate cutoff value was found for discriminating severity of IDD by William rank-sum test and locally weighted scatterplot smoothing algorithm. The cumulative grade was also calculated by summing Pfirrmann grades for all lumbar spine intervertebral discs. It was found that high-score group (total score > 18) plasma interleukin-6 (IL-6) concentration was significantly higher than that of the low-score group (total score ≤ 18) (9.6 ± 1.75 vs. 5.40 ± 0.61 pg/ml, p = 0.002), tumor necrosis factor-α (TNF-α) following the same trend (5.27 ± 1.48 vs. 2.97 ± 0.23, p = 0.006), which was most pronounced in the upper lumbar intervertebral discs (L1-3). In the entire sample, preoperative IL-6 concentration was significantly higher than that of the postoperation (p < 0.001), while the TNF-α was the opposite (p = 0.039). It was also found that there were significant differences in the two groups with respect to age and hypertension (p < 0.001 and p = 0.037). In conclusion, this study preliminarily indicated the relationship between IL-6 and TNF-α and the severity of lumbar disc degeneration.

Elevated Mitochondrial Reactive Oxygen Species within Cerebrospinal Fluid as New Index in the Early Detection of Lumbar Spinal Stenosis

Lumbar spinal stenosis (LSS) is a common neurodegenerative condition. However, how neurogenic claudication develops with severe leg pain has not yet been clearly elucidated. Moreover, cerebrospinal fluid (CSF) physiology at the lumbosacral level is poorly understood because of the difficulties involved in quantification and visualization. Recent studies have suggested that assessment of mitochondrial function in CSF provides an indirect way to assess neurological disorders and an important feature of disease progression. In this study, we assessed the relevance of endogenous extracellular mitochondria in the CSF of rats after LSS. Mitochondrial changes within the CSF were analyzed following LSS at 1 week using flow cytometry. An increase in cell size and number was observed in CSF with LSS, and reactive oxygen species (ROS) levels were also increased within the CSF at 1 week in the LSS group. Elevated mitochondrial ROS and functional changes in the CSF are hallmarks of LSS. The present study is the first to demonstrate that elevated mitochondrial ROS within the CSF is a new index for the early detection of LSS. Moreover, it may represent a potential novel treatment target for LSS.