The red wine polyphenol resveratrol shows promising potential for the treatment of nucleus pulposus-mediated pain in vitro and in vivo

The role of sirtuins in intervertebral disc degeneration: Mechanisms and therapeutic potential

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which affects the patients' quality of life and health and imposes a significant socioeconomic burden. Despite great efforts made by researchers to understand the pathogenesis of IDD, effective strategies for preventing and treating this disease remain very limited. Sirtuins are a highly conserved family of (NAD+)-dependent deacetylases in mammals that are involved in a variety of metabolic processes in vivo. In recent years, sirtuins have attracted much attention owing to their regulatory roles in IDD on physiological activities such as inflammation, apoptosis, autophagy, aging, oxidative stress, and mitochondrial function. At the same time, many studies have explored the therapeutic effects of sirtuins-targeting activators or micro-RNA in IDD. This review summarizes the molecular pathways of sirtuins involved in IDD, and summarizes the therapeutic role of activators or micro-RNA targeting Sirtuins in IDD, as well as the current limitations and challenges, with a view to provide possible solutions for the treatment of IDD.

Sirtuins in intervertebral disc degeneration: current understanding

BACKGROUND

Intervertebral disc degeneration (IVDD) is one of the etiologic factors of degenerative spinal diseases, which can lead to a variety of pathological spinal conditions such as disc herniation, spinal stenosis, and scoliosis. IVDD is a leading cause of lower back pain, the prevalence of which increases with age. Recently, Sirtuins/SIRTs and their related activators have received attention for their activity in the treatment of IVDD. In this paper, a comprehensive systematic review of the literature on the role of SIRTs and their activators on IVDD in recent years is presented. The molecular pathways involved in the regulation of IVDD by SIRTs are summarized, and the effects of SIRTs on senescence, inflammatory responses, oxidative stress, and mitochondrial dysfunction in myeloid cells are discussed with a view to suggesting possible solutions for the current treatment of IVDD.

PURPOSE

This paper focuses on the molecular mechanisms by which SIRTs and their activators act on IVDD.

METHODS

A literature search was conducted in Pubmed and Web of Science databases over a 13-year period from 2011 to 2024 for the terms "SIRT", "Sirtuin", "IVDD", "IDD", "IVD", "NP", "Intervertebral disc degeneration", "Intervertebral disc" and "Nucleus pulposus".

RESULTS

According to the results, SIRTs and a large number of activators showed positive effects against IVDD.SIRTs modulate autophagy, myeloid apoptosis, oxidative stress and extracellular matrix degradation. In addition, they attenuate inflammatory factor-induced disc damage and maintain homeostasis during disc degeneration. Several clinical studies have reported the protective effects of some SIRTs activators (e.g., resveratrol, melatonin, honokiol, and 1,4-dihydropyridine) against IVDD.

CONCLUSION

The fact that SIRTs and their activators play a hundred different roles in IVDD helps to better understand their potential to develop further treatments for IVDD.

NOVELTY

This review summarizes current information on the mechanisms of action of SIRTs in IVDD and the challenges and limitations of translating their basic research into therapy.

From drugs to biomaterials: a review of emerging therapeutic strategies for intervertebral disc inflammation

Chronic low back pain (LBP) is an increasingly prevalent issue, especially among aging populations. A major underlying cause of LBP is intervertebral disc degeneration (IDD), often triggered by intervertebral disc (IVD) inflammation. Inflammation of the IVD is divided into Septic and Aseptic inflammation. Conservative therapy and surgical treatment often fail to address the root cause of IDD. Recent advances in the treatment of IVD infection and inflammation range from antibiotics and small-molecule drugs to cellular therapies, biological agents, and innovative biomaterials. This review sheds light on the complex mechanisms of IVD inflammation and physiological and biochemical processes of IDD. Furthermore, it provides an overview of recent research developments in this area, intending to identify novel therapeutic targets and guide future clinical strategies for effectively treating IVD-related conditions.

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.

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.

Pharmacological Effects of Resveratrol in Intervertebral Disc Degeneration: A Literature Review

Intervertebral disc degeneration (IDD) is a high incidence disease of musculoskeletal system that often leads to stenosis, instability, pain and even deformity of the spinal segments. IDD is an important cause of discogenic lower back pain and often leads to large economic burden to families and society. Currently, the treatment of IDD is aimed at alleviating symptoms rather than blocking or reversing pathological progression of the damaged intervertebral disc. Resveratrol (RSV) is a polyphenol phytoalexin first extracted from the Veratrum grandiflflorum O. Loes and can be found in various plants and red wine. Owing to the in-depth study of pharmacological mechanisms, the therapeutic potential of RSV in various diseases such as osteoarthritis, neurodegenerative diseases, cardiovascular diseases and diabetes have attracted the attention of many researchers. RSV has anti-apoptotic, anti-senescent, anti-inflammatory, anti-oxidative, and anabolic activities, which can prevent further degeneration of intervertebral disc cells and enhance their regeneration. With high safety and various biological functions, RSV might be a promising candidate for the treatment of IDD. This review summarizes the biological functions of RSV in the treatment of IDD and to facilitate further research.

Targeting Oxidative Stress and Inflammation in Intervertebral Disc Degeneration: Therapeutic Perspectives of Phytochemicals

Low back pain is a major cause of disability worldwide that declines the quality of life; it poses a substantial economic burden for the patient and society. Intervertebral disc (IVD) degeneration (IDD) is the main cause of low back pain, and it is also the pathological basis of several spinal degenerative diseases, such as intervertebral disc herniation and spinal stenosis. The current clinical drug treatment of IDD focuses on the symptoms and not their pathogenesis, which results in frequent recurrence and gradual aggravation. Moreover, the side effects associated with the long-term use of these drugs further limit their use. The pathological mechanism of IDD is complex, and oxidative stress and inflammation play an important role in promoting IDD. They induce the destruction of the extracellular matrix in IVD and reduce the number of living cells and functional cells, thereby destroying the function of IVD and promoting the occurrence and development of IDD. Phytochemicals from fruits, vegetables, grains, and other herbs play a protective role in the treatment of IDD as they have anti-inflammatory and antioxidant properties. This article reviews the protective effects of phytochemicals on IDD and their regulatory effects on different molecular pathways related to the pathogenesis of IDD. Moreover, the therapeutic limitations and future prospects of IDD treatment have also been reviewed. Phytochemicals are promising candidates for further development and research on IDD treatment.

Bioactive compounds for neuropathic pain: An update on preclinical studies and future perspectives

Among different types of chronic pain, neuropathic pain (NP), arising from damage to the nervous system, including peripheral fibers and central neurons, is notoriously difficult to treat and affects 7-10% of the general population. Currently available treatment options for NP are limited and opioid analgesics have severe side effects and can result in opioid use disorder. Recent studies have exhibited the role of dietary bioactive compounds in the mitigation of NP. Here, we assessed the effects of commonly consumed bioactive compounds (ginger, curcumin, omega-3 polyunsaturated fatty acids, epigallocatechin gallate, resveratrol, soy isoflavones, lycopene, and naringin) on NP and NP-related neuroinflammation. Cellular studies demonstrated that these bioactive compounds reduce inflammation via suppression of NF-κB and MAPK signaling pathways that regulate apoptosis/cell survival, antioxidant, and anti-inflammatory responses. Animal studies strongly suggest that these regularly consumed bioactive compounds have a pronounced anti-NP effect as shown by decreased mechanical allodynia, mechanical hyperalgesia, thermal hyperalgesia, and cold hyperalgesia. The proposed molecular mechanisms include (1) the enhancement of neuron survival, (2) the reduction of neuronal hyperexcitability by activation of antinociceptive cannabinoid 1 receptors and opioid receptors, (3) the suppression of sodium channel current, and (4) enhancing a potassium outward current in NP-affected animals, triggering a cascade of chemical changes within, and between neurons for pain relief. Human studies administered in this area have been limited. Future randomized controlled trials are warranted to confirm the findings of preclinical efficacies using bioactive compounds in patients with NP.

The Role of Oxidative Stress in Intervertebral Disc Degeneration

Intervertebral disc degeneration is a very common type of degenerative disease causing severe socioeconomic impact, as well as a major cause of discogenic low back pain and herniated discs, placing a heavy burden on patients and the clinicians who treat them. IDD is known to be associating with a complex process involving in extracellular matrix and cellular damage, and in recent years, there is increasing evidence that oxidative stress is an important activation mechanism of IDD and that reactive oxygen and reactive nitrogen species regulate matrix metabolism, proinflammatory phenotype, autophagy and senescence in intervertebral disc cells, apoptosis, autophagy, and senescence. Despite the tremendous efforts of researchers within the field of IDD pathogenesis, the proven strategies to prevent and treat this disease are still very limited. Up to now, several antioxidants have been proved to be effective for alleviating IDD. In this article, we discussed that oxidative stress accelerates disc degeneration by influencing aging, inflammation, autophagy, and DNA methylation, and summarize some antioxidant therapeutic measures for IDD, indicating that antioxidant therapy for disc degeneration holds excellent promise.

Antioxidant Effects of Resveratrol in Intervertebral Disk

Intervertebral disk (IVD) degeneration (IVDD) can cause various spinal degenerative diseases. Cumulative evidence has indicated that IVDD can result from inflammation, apoptosis, autophagy, biomechanical changes and other factors. Currently, lack of conservative treatment for degenerative spinal diseases leads to an urgent demand for clinically applicable medication to ameliorate the progression of IVDD. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a polyphenol compound extracted from red wine or grapes, has shown protective effects on IVD, alleviating the progression of IVDD. Resveratrol has been demonstrated as a scavenger of free radicals both in vivo and in vitro. The antioxidant effects of resveratrol are likely attributed to its regulation on mitochondrial dysfunction or the elimination of reactive oxygen species. This review will summarize the mechanisms of the reactive oxygen species production and elaborate the mechanisms of resveratrol in retarding IVDD progression, providing a comprehensive understanding of the antioxidant effects of resveratrol in IVD.

miR-217 through SIRT1 regulates the immunotoxicity of cadmium in Cyprinus carpio

MicroRNAs (miRNAs) play a critical role in regulating the response of animals exposed to heavy metal stress. As a globally dispersed heavy metal in aquatic ecosystems, cadmium (Cd) is highly toxic to many aquatic species. However, little is known about the miRNA response to Cd stress in fish. To investigate the regulatory effect of miRNAs in response to Cd, common carp (Cyprinus carpio) were exposed to Cd²⁺-containing water (0.005 mg/L, 0.05 mg/L, 0.5 mg/L) for 30 days. After exposure, Cd²⁺ contents were significantly higher in the kidneys of C. carpio compared to other tissues, when exposed to 0.5 mg/L Cd²⁺. Hematoxylin and eosin staining images revealed that elevated Cd induced inflammatory damage in the kidneys of C.carpio. Further, miRNA sequencing revealed nine differentially expressed miRNAs (miR-217, miR-205 and seven novel miRNAs) in the kidneys, between 0.5 mg/L Cd²⁺ exposure and control groups. Potential target mRNAs of miRNAs suggest that miR-217 is involved in immunotoxicity. miR-217 agomir was intraperitoneally administered to C. carpio and RT-PCR revealed that the expression of IL-8 and SIRT1 decreased, while TLR-4, TRAF6, NF-kB, TNF-α, IL-1β, and TGF-β increased in the kidneys of C.carpio. Additionally, the expression of SIRT1 decreased, while the expression of other mRNAs increased in kidneys of C. carpio exposed to Cd. According to mRNAs expression in the agomir and Cd treatment, miRNAs inhibit the expressions of target mRNAs. These results demonstrate that miR-217 via SIRT1 plays a regulatory role in the immunotoxicity of Cd to C. carpio.

Role of SIRT1 in Neuropathic Pain from the Viewpoint of Neuroimmunity

The current clinical first-line treatment of neuropathic pain still considers only the nervous system as the target, and its therapeutic effect is limited. An increasing number of studies support the opinion that neuropathic pain is a result of the combined action of the sensory nervous system and the related immune system. Under physiological conditions, both the nervous system and the immune system can maintain homeostasis by adjusting the mitochondrial function when sensing noxious stimulation. However, in the case of neuropathic pain, mitochondrial regulatory dysfunction occurs, which may result from the decreased expression of SIRT1. In this study, we review the role of SIRT1 in neuropathic pain from the viewpoint of neuroimmunity.

The Anti-Inflammatory and Cytoprotective Efficiency of Curvularin, a Fungal Macrolactone against Lipopolysaccharide-Induced Inflammatory Response in Nucleus Pulposus Cells: An In Vitro Study

STUDY DESIGN

Developing an in vitro model for assessing the anti-inflammatory properties of curvularin.

PURPOSE

To evaluate the efficacy of natural fungal macrolactone as a therapeutic drug against lipopolysaccharide (LPS)-induced inflammation in primary human nucleus pulposus cells (NPCs) in vitro.

OVERVIEW OF LITERATURE

Lumbar disk disease is a common cause of lower back pain (LBP) and sciatica. It is an established fact that inflammation, rather than mechanical compression on the nerve root, plays a role in the cause of LBP and sciatica. Current treatment options for reducing inflammation are either nonsteroidal anti-inflammatory drugs or steroids, prolonged use of which can potentially lead to adverse effects such as gastrointestinal disturbances and renal and cardiac issues. Hence, there is a need for better antiinflammatory drugs with no or minimal complications for treating inflammation-induced LBP and sciatica. Curvularin (Cur), a fungal macrolactone, is known for its anti-inflammatory activity, but nothing is known about its impact on inflammation due to disk pathologies.

METHODS

Primary NPCs were cultured and characterized by flow cytometry and immunocytochemistry using the CD24 antibody and treated with 10 μg/mL LPS for 36 hours and then treated with Cur, betamethasone, and dexamethasone (10 μg/mL) for 48 hours, after which cell cycle analysis, cell viability assay, and gene expression studies (quantitative polymerase chain reaction [PCR] and quantitative real-time-PCR) were conducted. The NPCs treated with Cur downregulated the expression of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin [IL]-1β, and IL-6); matrix metalloproteinases (MMPs; MMP-2 and MMP-3), ADAMTS; and apoptotic marker (cytochrome c).

RESULTS

In our study, Cur-treated cells showed enhanced expression of collagen 9A1 and insulin-like growth factor receptor 1, indicating the recovery of NPCs from inflammatory assault.

CONCLUSIONS

Based on observations, the anti-inflammatory properties of Cur render it an excellent drug molecule for treating disk degeneration nonsurgically, by direct injection into spinal disks when treating LBP and sciatica.

S100A9 induces nucleus pulposus cell degeneration through activation of the NF-κB signaling pathway

Oxidative stress in the lumbar disc leads to the degeneration of nucleus pulposus (NP). However, the molecular mechanisms underlying this process remain unclear. In this study, we delineated a key calcium-binding protein, S100A9, which was induced by oxidative stress and was highly expressed in the degenerative NP. Immunofluorescence staining and Western blotting revealed that S100A9 induced NP cell apoptosis in vitro by up-regulating the expression of pro-apoptotic markers, including cleaved caspase-3, cytochrome c and Bax. Moreover, RT-PCR analyses revealed that the expression of S100A9 caused NP matrix degradation by up-regulating the expression of matrix degradation enzymes and increased the inflammatory response by up-regulating cytokine expression. Therefore, S100A9 induced NP cell degeneration by exerting pro-apoptotic, pro-degradation and pro-inflammatory effects. The detailed mechanism underlying S100A9-induced NP degeneration was explored by administering SC75741, a specific NF-κB inhibitor in vitro. We concluded that S100A9 induced NP cell apoptosis, caused matrix degradation and amplified the inflammatory response through the activation of the NF-κB signalling pathway. Inhibition of these pro-apoptotic, pro-degradation and pro-inflammatory effects induced by S100A9 in NP may be a favourable therapeutic strategy to slow lumbar disc degeneration.

Resveratrol-enhanced SIRT1-mediated osteogenesis in porous endplates attenuates low back pain and anxiety behaviors

Low back pain (LBP) is a major clinical problem that lacks effective treatments. The sensory innervation in porous vertebral endplates and anxiety contributes to spinal hyperalgesia. We hypothesized that SIRT1 activator resveratrol alleviates LBP and anxiety via promotion of osteogenesis in the porous endplates. The hyperalgesia and anxiety-related behaviors; sensory innervation, inflammation and porosity of endplates; and osteogenic/osteoclastic factors expression were measured following resveratrol treatment after lumbar spine instability (LSI) surgery. To explore whether resveratrol promotes endplates osteogenesis and thus alleviates LBP through activation of SIRT1 in the osteoprogenitor cells of endplates, SIRT1OSX-/- mice were employed. Additionally, the levels of inflammation markers, phosphorylation of cAMP response element-binding protein (pCREB), and brain-derived neurotrophic factor (BDNF) in hippocampus were evaluated. After 4 or 8 weeks LSI surgery, the mice suffered from hyperalgesia and anxiety, which were efficiently attenuated by resveratrol at 8 weeks. Resveratrol treatment-enhanced osteogenesis and decreased endplates porosities accompanied with the reduction of TNFα, IL-1β, and COX2 levels and CGRP+ nerve fibers innervation in porous endplates. Resveratrol-mediated endplates osteogenesis, decreased endplates porosities, and analgesic and antianxiety effects were abrogated in SIRT1OSX-/- mice. Furthermore, resveratrol relieved inflammation and increased pCREB and BDNF expression in the hippocampus after 8 weeks, which alleviate anxiety-related behaviors. This study provides that resveratrol-mediated porous endplates osteogenesis via the activation of SIRT1 markedly blocked sensory innervation and inflammation in endplates, therefore, alleviating LSI surgery-induced LBP and hippocampus-related anxiety.

Painful intervertebral disc degeneration and inflammation: from laboratory evidence to clinical interventions

Low back pain (LBP), as a leading cause of disability, is a common musculoskeletal disorder that results in major social and economic burdens. Recent research has identified inflammation and related signaling pathways as important factors in the onset and progression of disc degeneration, a significant contributor to LBP. Inflammatory mediators also play an indispensable role in discogenic LBP. The suppression of LBP is a primary goal of clinical practice but has not received enough attention in disc research studies. Here, an overview of the advances in inflammation-related pain in disc degeneration is provided, with a discussion on the role of inflammation in IVD degeneration and pain induction. Puncture models, mechanical models, and spontaneous models as the main animal models to study painful disc degeneration are discussed, and the underlying signaling pathways are summarized. Furthermore, potential drug candidates, either under laboratory investigation or undergoing clinical trials, to suppress discogenic LBP by eliminating inflammation are explored. We hope to attract more research interest to address inflammation and pain in IDD and contribute to promoting more translational research.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

Small molecule-based treatment approaches for intervertebral disc degeneration: Current options and future directions

Low back pain (LBP) is a major reason for disability, and symptomatic intervertebral disc (IVD) degeneration (IDD) contributes to roughly 40% of all LBP cases. Current treatment modalities for IDD include conservative and surgical strategies. Unfortunately, there is a significant number of patients in which conventional therapies fail with the result that these patients remain suffering from chronic pain and disability. Furthermore, none of the current therapies successfully address the underlying biological problem - the symptomatic degenerated disc. Both spinal fusion as well as total disc replacement devices reduce spinal motion and are associated with adjacent segment disease. Thus, there is an unmet need for novel and stage-adjusted therapies to combat IDD. Several new treatment options aiming to regenerate the IVD are currently under investigation. The most common approaches include tissue engineering, growth factor therapy, gene therapy, and cell-based treatments according to the stage of degeneration. Recently, the regenerative activity of small molecules (low molecular weight organic compounds with less than 900 daltons) on IDD was demonstrated. However, small molecule-based therapy in IDD is still in its infancy due to limited knowledge about the mechanisms that control different cell signaling pathways of IVD homeostasis. Small molecules can act as anti-inflammatory, anti-apoptotic, anti-oxidative, and anabolic agents, which can prevent further degeneration of disc cells and enhance their regeneration. This review pursues to give a comprehensive overview of small molecules, focusing on low molecular weight organic compounds, and their potential utilization in patients with IDD based on recent in vitro, in vivo, and pre-clinical studies.

Intrathecal Injection of SIRT1-modified Human Mesenchymal Stem Cells Alleviates Neuropathic Pain in Rat

Accumulating evidence has elucidated that human mesenchymal stem cells (hMSCs) exert profound analgesic effects on numerous animal models of neuropathic pain, including drug-induced peripheral nerves, diabetes-induced neuropathy, and chronic constriction injury. We aimed to address whether forcing expression of sirtuin 1 (SIRT1) can enhance the efficacy of hMSCs on alleviation of pain sensation. A rat model of chronic constriction injury (CCI) mimicking peripheral nerve injury was incorporated in the study. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) testing were used to measure pain-related behavior. Our results demonstrated that SIRT1 was decreased post-CCI surgery. Compared to hMSCs-control implantation, the hMSCs-SIRT1 (hMSCs overexpressing SIRT1) implantation exhibited superior effects on reducing pro-inflammatory cytokine levels in serum and spinal dorsal horn, while ameliorating neuropathic pain in CCI rat. Engineering hMSCs such as overexpressing SIRT1 may serve as a promising strategy for the treatment of patients with neuropathic pain.

Resveratrol protects against apoptosis induced by interleukin-1β in nucleus pulposus cells via activating mTOR/caspase-3 and GSK-3β/caspase-3 pathways

Objective: The purpose of the present study was to investigate the specific downstream signaling pathway mediated by PI3K/Akt in resveratrol (RES) anti-apoptosis of nucleus pulposus cells (NPCs).

Materials and methods: Human NPCs were cultured and divided into six groups. Interleukin (IL)-1β was used to induce apoptosis and RES to inhibit apoptosis. Fluorescence-activated cell sorting (FACS) analysis was used to test apoptotic incidence of NPCs, cell counting kit-8 (CCK-8) assay was performed to detect cell viability, The expression level of caspase-3 mRNA was detected by RT-qPCR, and protein levels were determined by Western blot.

Results: Flow cytometry analysis showed that IL-1β increased the apoptosis rate of NPCs in each group, and RES significantly decreased the apoptosis rate, while rapamycin (RAPA) and SB216763 inhibited the effect of RES and increased the apoptosis rate again. Similarly, CCK-8 showed that IL-1β decreased activity of NPCs in each group, while RES increased cell activity, RAPA and SB216763 inhibited the effect of RES and decreased cell activity. RT-qPCR results showed IL-1β significantly increased the level of caspase-3 expression, but it was significantly decreased by using RES, RAPA and SB216763 respectively attenuated effects of RES. Western blot results showed that activated caspase-3 was inhibited by RES effect, and was up-regulated again after the addition of RAPA and SB216763. In addition, p-mTOR and p-GSK-3β were up-regulated by RES and down-regulated by RAPA and SB216763.

Conclusion: RES can inhibit apoptosis induced by IL-1β in human NPCs. PI3K/Akt/mTOR/caspase-3 and PI3K/Akt/GSK-3β/caspase-3 pathways are potential mechanisms underlying this process.

Sirtuins and intervertebral disc degeneration: Roles in inflammation, oxidative stress, and mitochondrial function

Intervertebral disc degeneration (IDD) is one of the main causes of low back pain, which seriously reduces the quality of life of patients and places a heavy economic burden on their families. Cellular senescence is considered to be an important factor leading to IDD, and inflammatory response, oxidative stress, and mitochondrial dysfunction are closely related to intervertebral disc (IVD) senescence. Therefore, inhibition of the inflammatory response and oxidative stress, along with maintaining mitochondrial function, may be useful in treating IDD. The sirtuins are a family of evolutionarily conserved nicotinamide adenine dinucleotide (NAD⁺)-dependent histone deacetylases, which are the major molecules mediating life extension or delay of aging-related diseases. The sirtuin protein family consist of seven members (SIRT1 - 7), which are mainly involved in various aging-related diseases by regulating inflammation, oxidative stress, and mitochondrial function. Among them, SIRT1, SIRT2, SIRT3, and SIRT6 are closely related to IDD. In addition, some activators of sirtuin proteins, such as resveratrol, melatonin, magnolol, 1,4-dihydropyridine (DHP), SRT1720, and nicotinamide mononucleotide (NMN), have been evaluated in preclinical studies for their effects in preventing IDD. This review described the biological functions of sirtuins and the important roles of SIRT1, SIRT2, SIRT3, and SIRT6 in IDD by regulating oxidative stress, inflammatory response, and mitochondrial function. In addition, we introduce the status of some sirtuin activators in IDD preclinical studies. This review will provide a background for further clarification of the molecular mechanism underlying IDD and the development of potential therapeutic drugs.

Melatonin Protects Intervertebral Disc from Degeneration by Improving Cell Survival and Function via Activation of the ERK1/2 Signaling Pathway

Melatonin, a neuroendocrine hormone secreted by the pineal body, has a positive effect on intervertebral disc degeneration. The present study is aimed at investigating the biological role of melatonin in intervertebral disc degeneration and its underlying mechanism. A human nucleus pulposus cell (NPC) line was exposed to melatonin at different concentrations. Cell proliferation was measured by CCK-8 assay. Cell cycle and apoptosis were analyzed by flow cytometry. Western blot was performed to measure the protein expression of indicated genes. A rabbit model of intervertebral disc degeneration was established to detect the role and mechanism of melatonin on intervertebral disc degeneration. Our study showed that melatonin promoted NPC viability and inhibited cell arrest. Furthermore, melatonin treatment led to the upregulation of collagen II and aggrecan and downregulation of collagen X. Moreover, melatonin significantly elevated the activity of the ERK signaling pathway. Inhibition of the ERK1/2 signals reversed the role of melatonin in the regulation of NPCs both in vitro and in vivo. Melatonin increased NPC viability through inhibition of cell cycle arrest and apoptosis. Moreover, melatonin promoted the secretion of functional factors influencing the nucleus pulposus cell physiology and retarded cell degeneration. Our results suggest that melatonin activated the ERK1/2 signaling pathway, thereby affecting the biological properties of the intervertebral disc degeneration.

Acetaminophen combined with tramadol is more effective than acetaminophen or tramadol to reduce neuropathic root pain: an experimental study with application of nucleus pulposus in a rat model

INTRODUCTION

Various drugs are used to treat patients with neuropathic pain; however, optimal treatment using acetaminophen (A) and/or tramadol (T) remains unclear. The evidence supporting the drug choice and the timing of administration is insufficient. Therefore, the objective of the present study was to investigate the effect of T and/or A on pain-related behavior in a nucleus pulposus (NP) rat model.

MATERIALS AND METHODS

Sprague-Dawley rats (n = 180) were divided into NP-A (52 mg/kg), NP-T (6 mg/kg), NP-AT (combined A and T), NP-S (saline), and sham groups (n = 36 per group). The rats received 0.2 mL of treatment solution orally once daily for 7 days after application of NP on the left L5 dorsal root ganglion (DRG). Behavioral testing and immunohistochemistry analysis for some markers' expressions in DRGs and the spinal cord were performed.

RESULTS

Pain thresholds in the NP-AT group did not significantly differ from the sham at all time points, while those were significantly lower in the NP-A and in the NP-T groups at D7 and/or D14 (p < 0.05). Tumor necrosis factor-α in the NP-S group was significantly higher at D2 and D7 (p < 0.05). Among the three treatment groups, activating transcriptional factor 3 and growth-associated protein 43 showed a tendency toward an increase at D7-D21.

CONCLUSION

Combined administration of acetaminophen and tramadol maintained in the pain threshold in the rat NP model. These findings suggest that the combination of acetaminophen and tramadol might be a potential therapeutic modality for patients with lumbar disc herniation. These slides can be retrieved under Electronic Supplementary Material.

Dietary polyphenols as a safe and novel intervention for modulating pain associated with intervertebral disc degeneration in an in-vivo rat model

Developing effective therapies for back pain associated with intervertebral disc (IVD) degeneration is a research priority since it is a major socioeconomic burden and current conservative and surgical treatments have limited success. Polyphenols are naturally occurring compounds in plant-derived foods and beverages, and evidence suggests dietary supplementation with select polyphenol preparations can modulate diverse neurological and painful disorders. This study tested whether supplementation with a select standardized Bioactive-Dietary-Polyphenol-Preparation (BDPP) may alleviate pain symptoms associated with IVD degeneration. Painful IVD degeneration was surgically induced in skeletally-mature rats by intradiscal saline injection into three consecutive lumbar IVDs. Injured rats were given normal or BDPP-supplemented drinking water. In-vivo hindpaw mechanical allodynia and IVD height were assessed weekly for 6 weeks following injury. Spinal column, dorsal-root-ganglion (DRG) and serum were collected at 1 and 6 weeks post-operative (post-op) for analyses of IVD-related mechanical and biological pathogenic processes. Dietary BDPP significantly alleviated the typical behavioral sensitivity associated with surgical procedures and IVD degeneration, but did not modulate IVD degeneration nor changes of pro-inflammatory cytokine levels in IVD. Gene expression analyses suggested BDPP might have an immunomodulatory effect in attenuating the expression of pro-inflammatory cytokines in DRGs. This study supports the idea that dietary supplementation with BDPP has potential to alleviate IVD degeneration-related pain, and further investigations are warranted to identify the mechanisms of action of dietary BDPP.

Temporal and Spatial Changes of μ-Opioid Receptors in the Brain, Spinal Cord and Dorsal Root Ganglion in a Rat Lumbar Disc Herniation Model

STUDY DESIGN

Controlled, interventional, animal study.

OBJECTIVE

To investigate the spatial and temporal changes of μ-opioid receptor (MOR) expression in a rat lumbar disc herniation (LDH) model.

SUMMARY OF BACKGROUND DATA

MORs widely express in the peripheral and central nervous systems, and opioid drugs produce an analgesic effect through their activation. However, the efficacy of opioid drugs is sometimes inadequate in several pathological conditions of pain. MORs in the brain as well as the spinal cord (SC) and dorsal root ganglion (DRG) are thought to be associated with pain-related behavior, but the underlying mechanisms are not completely understood.

METHODS

In all, 91 adult female Sprague-Dawley rats were used. Autologous nucleus pulposus (NP) was applied onto the left L5 DRG in the NP group rats. Rats were divided into two surgical groups, the NP and the sham group. The von Frey test of left hind paw was performed before surgery, and 2, 7, 14, 21 and 28 days after surgery. Immunohistochemistry and immunoblotting in the DRG, SC, Caudate putamen, nucleus accumbens (NAc) and periaqueductal grey matter were performed before surgery, and 2, 7, 14, 21 and 28 days after surgery.

RESULTS

The thresholds in the NP group were significantly lower than those in the sham group from day 2 onwards. At days 7 and 14, MOR expression in the injured-side SC and DRG were significantly lower than those in the sham group. At day 21, MOR in the NAc was significantly decreased compared to that in the sham group.

CONCLUSION

Changes of MOR expression in the NAc, SC and DRG were associated with pain-related behavior. This result might show the underling pathogenesis of the resistance to MOR agonists in the patient with LDH.

LEVEL OF EVIDENCE

N/A.

Propionibacterium acnes induces discogenic low back pain via stimulating nucleus pulposus cells to secrete pro-algesic factor of IL-8/CINC-1 through TLR2-NF-κB p65 pathway

Latent infection of Propionibacterium acnes was considered as a new pathogeny for low back pain (LBP); however, there is no credible animal evidence or mechanism hypothesis. This study proved that P. acnes is a causative pathogen of bacteria-induced LBP and investigated its underlying mechanism. For this, P. acnes was firstly identified in patients' degenerated intervertebral disc (IVDs) samples. The results of patients' Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), Japanese Orthopaedic Association (JOA), and Oswestry Disability Index (ODI) scores indicated that P. acnes-positive patients showed more severe LBP and physical disability. Then, a P. acnes-inoculated lumbar IVDs model was established in rats. The results of paw/foot withdrawal threshold and qRT-PCR indicated that P. acnes-inoculated rats had obvious LBP in behavioral evaluation and over-expression of substance P (SP) and calcitonin gene-related peptide (CGRP) in IVDs. Subsequently, enzyme-linked immunosorbent assay (ELISA) results demonstrated that increased expression of IL-8 or CINC-1 (the homolog of IL-8 in rats) in the P. acnes-positive IVDs of human and rats. The CINC-1 injected animal model proved that the cytokines were able to induce LBP. Finally, the co-culture experiments showed that nucleus pulposus cells (NPCs) were able to respond to P. acnes and secreted IL-8/CINC-1 via TLR-2/NF-κB p65 pathway. In conclusion, P. acnes had strong association with LBP by stimulating NPCs to secrete pro-algesic factor of IL-8/CINC-1 via TLR2/NF-κBp65 pathway. The finding may provide a promising alternative therapy strategy for LBP in clinical. KEY MESSAGES: Patients with P. acnes-positive IVDs tended to have more severe LBP, physical disability, and increased IL-8 expressions. P. acnes can induce LBP via IL-8/CINC-1 in IVDs. P. acnes stimulate the NPCs to secrete pro-algesic factor of IL-8/CINC-1 via TLR2/NF-κBp65 pathway.

Resveratrol displays anti-inflammatory properties in an ex vivo model of immune mediated inflammatory arthritis

Background

Resveratrol is a natural polyphenol found in berries, roots and wine that is well known to have anti-inflammatory and anti-oxidative properties. The anti-inflammatory effect has been reported for both immune cells and connective tissues, but only few studies have investigated effects on immune mediated inflammatory arthritis. None of which have studied this effect when combining resveratrol with methotrexate or adalimumab, two major drugs in the treatment of immune mediated inflammatory arthritis.

We therefore aimed to investigate the anti-inflammatory effect of resveratrol alone and in combination with methotrexate or adalimumab in ex vivo models of immune mediated inflammatory arthritis. We furthermore aimed to describe any variations in this effect based on disease activity and cellular composition of the synovial fluid infiltrate.

Methods

Synovial fluid mononuclear cells from patients with rheumatoid arthritis (n = 7) and spondyloarthritis (n = 7) were cultured for either 48 h or 21 days. In both models, synovial fluid mononuclear cells were treated with resveratrol alone or in combination with methotrexate or adalimumab. Monocyte chemoattractant protein 1, matrix metalloproteinase 3 and tartrate resistant acidic phosphatase were measured to quantify inflammation, enzymatic degradation and osteoclast differentiation, respectively.

Results

Resveratrol reduced monocyte chemoattractant protein 1 production by synovial fluid mononuclear cells significantly (p = 0.005) compared to untreated controls. The effect of resveratrol was greatest in cultures from patients with low disease activity, i.e. DAS28CRP ≤ 3.2 (p = 0.022), and in cultures dominated by lymphocytes (p = 0.03). Further, the combination of methotrexate and resveratrol significantly reduced monocyte chemoattractant protein 1 levels compared with methotrexate alone in cultures from patients with low disease activity (p = 0.016), and in cultures with high lymphocyte count (p = 0.011). Resveratrol did not significantly affect matrix metalloproteinase 3 and tartrate resistant acidic phosphatase production.

Conclusion

Resveratrol has anti-inflammatory properties in our ex vivo model of immune mediated inflammatory arthritis. Results show an additive effect of resveratrol, when combined with methotrexate in samples dominated by lymphocytes and samples from patients with low disease activity. This suggests further investigations in vitro and whether this effect may also be present in a clinical setting.

Electronic supplementary material

The online version of this article (10.1186/s41927-018-0036-5) contains supplementary material, which is available to authorized users.

Resveratrol delivery by ultrasound-mediated nanobubbles targeting nucleus pulposus cells

Aim: To improve nucleus pulposus cell-targeted therapy for intervertebral disc degeneration (IDD) by fabricating a novel kind of ultrasound (US)-mediated poly(lactic-co-glycolic acid) nanobubbles (NBs) as a means of targeted drug delivery. Materials & methods: The resveratrol (RES)-embedded NBs were synthesized using a double-emulsion method. The active NP cell-targeting biomarker CDH2 antibody (AbCDH2) was further conjugated to the NBs using a carbodiimide method. Then, this RES/AbCDH2 NBs were examined by physical properties, specifc cell-targeting ability, anticatabolism effect in vitro and in vivo. Results: RES/AbCDH2 NBs exhibited high RES-loading efficiency, and US triggered accelerated RES release. Furthermore, RES/AbCDH2 NB treatment exhibited excellent anticatabolic ability in vitro; and in an IDD rabbit model, US-mediated RES/AbCDH2 NB injection effectively retarded the degenerative process of the intervertebral disc in vivo. Conclusion: The combination of US irradiation and drug delivery through RES/AbCDH2 NBs can be considered as a novel treatment option for IDD.

The potential of CRISPR/Cas9 genome editing for the study and treatment of intervertebral disc pathologies

The CRISPR/Cas9 system has emerged as a powerful tool for mammalian genome engineering. In basic and translational intervertebral disc (IVD) research, this technique has remarkable potential to answer fundamental questions on pathway interactions, to simulate IVD pathologies, and to promote drug development. Furthermore, the precisely targeted CRISPR/Cas9 gene therapy holds promise for the effective and targeted treatment of degenerative disc disease and low back pain. In this perspective, we provide an overview of recent CRISPR/Cas9 advances stemming from/with transferability to IVD research, outline possible treatment approaches for degenerative disc disease, and discuss current limitations that may hinder clinical translation.

Resveratrol protects against sodium nitroprusside induced nucleus pulposus cell apoptosis by scavenging ROS

Oxidative stress induced disc cell apoptosis plays an important role in intervertebral disc (IVD) degeneration. The present study aims to investigate effects of resveratrol (RV), a natural polyphenol compound, on sodium nitroprusside (SNP) induced nucleus pulposus (NP) cell apoptosis and related mechanism. Rat NP cells were pretreated with RV, N-acetyl cysteine (NAC) and carboxy-PTIO (PTIO) before SNP treatment. Cell Counting Kit-8 assay was carried out for cell viability evaluation. Annexin V/propidium iodide (PI), Hoechst 33258 and Actin‑Tracker Green and Tubulin-Tracker Red staining were conducted to detect NP cell apoptosis and apoptotic structural changes. Mitochondrial membrane potential (ΔΨm) was analyzed with tetramethylrhodamine methyl ester staining. DCFH-DA and DAF-FM DA staining was used to determine intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels. An ex vivo experiment was also carried out followed by TUNEL assay of sections of discs. SNP induced NP cell apoptosis, excessive production of intracellular ROS and NO, reduction of ΔΨm as well as disruption of cytoskeletal and morphological structure. Meanwhile, organ culture results showed that SNP induced NP cell apoptosis ex vivo. RV and NAC siginificantly inhibited SNP induced NP cell apoptosis, production of intracellular ROS, deline of ΔΨm as well as disruption of cytoskeletal and morphological structure, while RV did not suppress NO production. RV and NAC could also suppress SNP induced NP cell apoptosis ex vivo. However, PTIO did not prevent SNP induced NP cell apoptosis, though it scavenged NO significantly. In conclusion, RV protects against SNP induced NP cell apoptosis by scavenging ROS but not NO, suggesting a promising prospect of RV in IVD degeneration retardation.

Association Between Neurotrophic Factor Expression and Pain-Related Behavior Induced by Nucleus Pulposus Applied to Rat Nerve Root

STUDY DESIGN

An experimental animal study.

OBJECTIVE

To investigate the relationship between pain-related behavior and the expression of neurotrophic factors in the dorsal root ganglion (DRG) and spinal cord (SC) using a nucleus pulposus (NP) rat model.

SUMMARY OF BACKGROUND DATA

Neurotrophic factors are released from activated glial cells and are associated with pain-related behavior. Nerve growth factor (NGF) is a neurotrophic factor that is induced by inflammation.

METHODS

Rats were divided into an NP group (n = 94) and a sham-operated group (n = 46). NP harvested from the tail was applied to the left L5 DRG. Rats in the NP group were then divided into five subgroups: one non-treatment and four treatment groups. In the treatment groups, a dose of anti-NGF antibody or phosphate-buffered saline was administered into the DRG. Behavioral testing was performed to investigate the mechanical withdrawal threshold of the left hind paw for all groups. Immunohistochemical localization of NGF, phosphorylated p38 (p38), and brain-derived neurotrophic factor (BDNF) in the DRGs and SCs was performed, and the numbers of immunoreactive (IR) cells were counted.

RESULTS

The withdrawal threshold in the nontreatment NP group was significantly decreased for 35 days, and that of the middle- and high-dose treatment rats was significantly higher than the phosphate-buffered saline group values. In the DRG, NGF-IR, p38-IR, and BDNF-IR cells were increased for days 21. In the SC, BDNF-IR, and p38-IR cells were increased from days 7 to 21.

CONCLUSION

In the DRG, NGF expression increased, mechanical thresholds were reduced, and p38 and BDNF expression was increased in the NP group. p38 and BDNF expression was increased in SC neurons during the same period. Inhibition of NGF may be a potential treatment for neuropathic pain due to lumbar disc herniation.

LEVEL OF EVIDENCE

5.

Inflammatory Processes Associated with Canine Intervertebral Disc Herniation

Intervertebral disc herniation (IVDH) is an important pathology in humans and also in dogs. While the molecular disease mechanisms are well investigated in humans, little is known about the inflammatory mediators in naturally occurring canine IVDH. The objective of this study was to investigate whether the involved proinflammatory cytokines in human IVDH are also key cytokines in canine IVDH and thus to elucidate the suitability of the dog as a model for human trials. 59 samples from 25 dogs with surgically confirmed thoracolumbar IVDH were collected and classified in three subgroups: herniated (H), affected non-herniated (NH) disc, and adjacent non-affected (NA) disc. Discs from 11 healthy dogs acted as controls (C). Samples were analyzed for IL-1, IL-6, IL-8, and TNF-α expression (qPCR/ELISA) as well as cell infiltration and activation of the MAP kinase pathways (immunohistochemistry). Gene and protein expression of all key cytokines could be detected in IVDH affected dogs. Canine IVDH was significantly associated with a higher gene expression of IL-6 (H > C, NH > C) and TNF-α (H > C, NH > C, NA > C) and a significant down-regulation of IL-1β (H < C). Dogs with spontaneous pain had significantly higher IL-6 mRNA compared to those with pain arising only upon palpation. An inter-donor comparison (H and HN relative to NA) revealed a significant increase of IL-6 gene expression (H > NA, NH > NA). IL-8 (H > C, NA > C) and TNF-α (NH > C) protein levels were significantly increased in diseased dogs while inversely, IL-6 protein levels were significantly higher in patients with better clinical outcome. Aside from resident IVD cells, mostly monocytes and macrophages were found in extruded material, with concomitant activation of extracellular signal-regulated kinase p38 in the majority of samples. Dogs with spontaneous IVDH might provide a useful model for human disc diseases. Although the expression of key cytokines found in human IVDH was also demonstrated in canine tissue, the inflammatory mechanisms accompanying canine IVDH diverges partially from humans, which will require further investigations in the future. In dogs, IL-6 seems to play an important pathological role and may represent a new potential therapeutic target for canine patients.

Extracellular matrix alterations in senescent cells and their significance in tissue homeostasis

Normal cells after a defined number of successive divisions or after exposure to genotoxic stresses are becoming senescent, characterized by a permanent growth arrest. In addition, they secrete increased levels of pro-inflammatory and catabolic mediators, collectively termed "senescence-associated secretory phenotype". Furthermore, senescent cells exhibit an altered expression and organization of many extracellular matrix components, leading to specific remodeling of their microenvironment. In this review we present the current knowledge on extracellular matrix alterations associated with cellular senescence and critically discuss certain characteristic examples, highlighting the ambiguous role of senescent cells in the homeostasis of various tissues under both normal and pathologic conditions.

Effect of an Acid-sensing Ion Channels Inhibitor on Pain-related Behavior by Nucleus Pulposus Applied on the Nerve Root in Rats

STUDY DESIGN

Controlled, interventional animal study.

OBJECTIVE

To examine the effect of an inhibitor of acid-sensing ion channel 3 (ASIC3) on pain-related behavior induced by application of the nucleus pulposus (NP) onto the dorsal root ganglion (DRG) in rats.

SUMMARY OF BACKGROUND DATA

ASIC3 is associated with acidosis pain in inflamed or ischemic tissues and is expressed in sensory neurons and NP cells. The ASIC3 inhibitor, APETx2, increases the mechanical threshold of pain in models of knee osteoarthritis or postoperative pain. However, the efficacy of APETx2 for pain relief in the NP application model remains unknown.

METHODS

Autologous NP was applied to the left L5 nerve root of 183 adult female Sprague-Dawley rats. The DRGs were treated with NP plus one of the following four treatments: saline solution (SM), low (0.01 μg: LD), medium (0.1 μg: MD), or high dose (1.0 μg: HD) of APETx2. Behavioral testing was performed to investigate the mechanical withdrawal threshold using von Frey hairs. Expression of nerve growth factor, hypoxia-inducible factor-1α (HIF1α), activating transcription factor-3, and ionized calcium-binding adaptor molecule-1 was evaluated using immunohistochemistry. Statistical differences among multiple groups were assessed using the Steel test, the Tukey-Kramer test, and the Dunnett test. P < 0.05 were considered significant.

RESULTS

The thresholds in the HD group were higher than those in the SM group at Days 14 and 21 (P < 0.05). In the MD group, the threshold was higher than in the SM group at Day 14 (P < 0.05). High doses of APETx2 reduced the expression of HIF1α after Day 14 compared with the SM group (P < 0.05).

CONCLUSION

APETx2 significantly improved pain-related behavior in a dose-dependent manner. APETx2 may inhibit ASIC3 and partly inhibit Nav1.8 channels. This ASIC3 channel inhibitor may be a potential therapeutic agent in early-stage lumbar disc herniation.

LEVEL OF EVIDENCE

N/A.

A Histopathological Scheme for the Quantitative Scoring of Intervertebral Disc Degeneration and the Therapeutic Utility of Adult Mesenchymal Stem Cells for Intervertebral Disc Regeneration

The purpose of this study was to develop a quantitative histopathological scoring scheme to evaluate disc degeneration and regeneration using an ovine annular lesion model of experimental disc degeneration. Toluidine blue and Haematoxylin and Eosin (H&E) staining were used to evaluate cellular morphology: (i) disc structure/lesion morphology; (ii) proteoglycan depletion; (iii) cellular morphology; (iv) blood vessel in-growth; (v) cell influx into lesion; and (vi) cystic degeneration/chondroid metaplasia. Three study groups were examined: 5 × 5 mm lesion; 6 × 20 mm lesion; and 6 × 20 mm lesion plus mesenchymal stem cell (MSC) treatment. Lumbar intervertebral discs (IVDs) were scored under categories (i-vi) to provide a cumulative score, which underwent statistical analysis using STATA software. Focal proteoglycan depletion was associated with 5 × 5 mm annular rim lesions, bifurcations, annular delamellation, concentric and radial annular tears and an early influx of blood vessels and cells around remodeling lesions but the inner lesion did not heal. Similar features in 6 × 20 mm lesions occurred over a 3-6-month post operative period. MSCs induced a strong recovery in discal pathology with a reduction in cumulative histopathology degeneracy score from 15.2 to 2.7 (p = 0.001) over a three-month recovery period but no recovery in carrier injected discs.

ROS: Crucial Intermediators in the Pathogenesis of Intervertebral Disc Degeneration

Excessive reactive oxygen species (ROS) generation in degenerative intervertebral disc (IVD) indicates the contribution of oxidative stress to IVD degeneration (IDD), giving a novel insight into the pathogenesis of IDD. ROS are crucial intermediators in the signaling network of disc cells. They regulate the matrix metabolism, proinflammatory phenotype, apoptosis, autophagy, and senescence of disc cells. Oxidative stress not only reinforces matrix degradation and inflammation, but also promotes the decrease in the number of viable and functional cells in the microenvironment of IVDs. Moreover, ROS modify matrix proteins in IVDs to cause oxidative damage of disc extracellular matrix, impairing the mechanical function of IVDs. Consequently, the progression of IDD is accelerated. Therefore, a therapeutic strategy targeting oxidative stress would provide a novel perspective for IDD treatment. Various antioxidants have been proposed as effective drugs for IDD treatment. Antioxidant supplementation suppresses ROS production in disc cells to promote the matrix synthesis of disc cells and to prevent disc cells from death and senescence in vitro. However, there is not enough in vivo evidence to support the efficiency of antioxidant supplementation to retard the process of IDD. Further investigations based on in vivo and clinical studies will be required to develop effective antioxidative therapies for IDD.

[Effect of Melittin on collagen type II expression of rat endplate chondrocytes induced by interleukin 1β]

Objective

To observe the effect of Melittin on collagen type II (Col-II) expression of rat endplate chondrocytes (EPCs) induced by interleukin 1β (IL-1β).

Methods

Primary EPCs from the lumbar vertebra of 4-week-old Sprague Dawley rats were cultured in vitro and identified by morphological observation, toluidine blue staining and Col-II immunofluorescence staining. Then, MTT assay was used to determine the optimal concentration of IL-1 and Melittin. Next, EPCs at passage 3 were randomly divided into 4 groups: no treatment was done in group A as control group; the optimal concentration of IL-1β, Melittin, and both IL-1β and Melittin were used in groups B, C, and D respectively. The expression of Col-II was detected by Western blot after 48 hours intervention.

Results

Under inverted microscope, the first generation EPCs were polygonal; cell proliferation decreased after fifth generation, and cell morphology changed into fusiform. The acidic mucosubstance in the cytoplasm (such as Aggrecan) was stained dark blue by toluidine blue. After marking Col-II by immunofluorescence, the positive expression of cytoskeleton (green fluorescence) could be observed. MTT assay showed that IL-1β and Melittin could inhibit the EPCs in a dose-dependent manner after intervention of 24 and 48 hours, and the optimal concentrations of IL-1β and Melittin intervention were 10 ng/mL and 1.0 μg/mL respectively. Compared with group A, the expression of Col-II was significantly reduced in group B, and was significantly increased in group C by Western blot assay, but there was no significant difference between group D and group A. The Col-II expression levels of groups A, B, C, and D were 0.991±0.024, 0.474±0.127, 1.913±0.350, and 1.159±0.297 respectively, showing significant difference between the other groups ( P<0.05) except between group A and group D ( P>0.05).

Conclusion

Melittin has a protective effect on endplate cartilage, and the research results provide experimental basis for the prevention and treatment of spinal degenerative disease.

ROS: Crucial Intermediators in the Pathogenesis of Intervertebral Disc Degeneration

Excessive reactive oxygen species (ROS) generation in degenerative intervertebral disc (IVD) indicates the contribution of oxidative stress to IVD degeneration (IDD), giving a novel insight into the pathogenesis of IDD. ROS are crucial intermediators in the signaling network of disc cells. They regulate the matrix metabolism, proinflammatory phenotype, apoptosis, autophagy, and senescence of disc cells. Oxidative stress not only reinforces matrix degradation and inflammation, but also promotes the decrease in the number of viable and functional cells in the microenvironment of IVDs. Moreover, ROS modify matrix proteins in IVDs to cause oxidative damage of disc extracellular matrix, impairing the mechanical function of IVDs. Consequently, the progression of IDD is accelerated. Therefore, a therapeutic strategy targeting oxidative stress would provide a novel perspective for IDD treatment. Various antioxidants have been proposed as effective drugs for IDD treatment. Antioxidant supplementation suppresses ROS production in disc cells to promote the matrix synthesis of disc cells and to prevent disc cells from death and senescence in vitro. However, there is not enough in vivo evidence to support the efficiency of antioxidant supplementation to retard the process of IDD. Further investigations based on in vivo and clinical studies will be required to develop effective antioxidative therapies for IDD.

The Changes in the Expression of NF-KB in a Degenerative Human Intervertebral Disc model

We aim at determining the changes in the expression of NF-kB signaling pathway in degenerative intervertebral discs. We collected normal and degenerated intervertebral discs tissues. The normal and degenerated cells were cultivated and their histopathology and immunofluoresence studies were used to observe the position of NF-kB p65 in the cell. We also treated the nucleus pulposus cells with inflammatory factors and inhibitors. Western blot was used to analyze the expression of different proteins. Real time fluorescence-based quantitative PCR was used for observation of NF-kB regulation of change in gene expression. Immunofluorescence showed that in the non-degenerative group the p65 was found in the cytoplasm of the nucleus pulposus cell while in the degenerated cell group the p65 protein was found in the nucleus of the cell. The expression of p65 increased with increase in the degree of degenerative change of the nucleus pulposus cell. RT-PCR showed that the expression of matrix metalloproteinases, aggrecanases and IL-6 was higher in the degenerative group. The amount of aggrecan and type II collagen was significantly decreased in the degenerative group. IL-1β was able to upregulate the activation of NF-kB and the expression of MMP-13 and ADAMTS-4 was also significantly increased. The effect of these proteins can be inhibited by the NF-kB inhibitor, BAY11-7082. The activation of the NK-kB signaling pathway in a degenerative intervertebral disc is gradually increased, regulating the over-expression of matrix-degrading enzymes. It plays an important role in the degradation of extracellular matrix.

Protective effects of resveratrol on autologous nucleus pulposus model of radiculopathy

Nucleus pulposus (NP) has been suggested to trigger an autoimmune response if exposed to the immune system, which plays a key role in neuropathic pain. Therefore, appropriate suppression of inflammation is a key factor for treating the radiculopathy caused by intervertebral disk (IVD) degeneration. Resveratrol, a key component of red wine, has been suggested to exhibit anti-inflammatory properties in vitro and in vivo. However, the effects of resveratrol on NP-mediated pain in vivo have not been studied. The aim of the present study was to investigate whether resveratrol may be useful in treating NP-mediated pain in an autologous NP model of radiculopathy. A total of 36 adult male Sprague-Dawley rats were allocated randomly into sham (group I), saline-treated (group II) and resveratrol-treated (group III) groups. Animal behavior in response to non-noxious mechanical stimulation with von Frey filaments was compared at days 0 (baseline), 3, 7, 14 and 21 following surgery. The expression of proinflammatory cytokines such as tumor necrosis factor α (TNF-α) and interleukin-1 (IL-1) were assessed at days 7 and 14. The data showed that resveratrol exhibited an anti-inflammatory effect on the expression of proinflammatory cytokines. Compared with group II, the expression of TNF-α and IL-1 was significantly decreased at each time point in group III. In addition, resveratrol significantly reduced pain behavior triggered by the application of NP tissue on the dorsal root ganglion for up to 14 days. These data suggest that resveratrol has potential for the treatment of NP-mediated pain, indicating a potential clinical application.

An Inflammatory Nucleus Pulposus Tissue Culture Model to Test Molecular Regenerative Therapies: Validation with Epigallocatechin 3-Gallate

Organ cultures are practical tools to investigate regenerative strategies for the intervertebral disc. However, most existing organ culture systems induce severe tissue degradation with only limited representation of the in vivo processes. The objective of this study was to develop a space- and cost-efficient tissue culture model, which represents degenerative processes of the nucleus pulposus (NP). Intact bovine NPs were cultured in a previously developed system using Dyneema jackets. Degenerative changes in the NP tissue were induced either by the direct injection of chondroitinase ABC (1-20 U/mL) or by the diffusion of interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) (both 100 ng/mL) from the culture media. Extracellular matrix composition (collagens, proteoglycans, water, and DNA) and the expression of inflammatory and catabolic genes were analyzed. The anti-inflammatory and anti-catabolic compound epigallocatechin 3-gallate (EGCG, 10 µM) was employed to assess the relevance of the degenerative NP model. Although a single injection of chondroitinase ABC reduced the proteoglycan content in the NPs, it did not activate cellular responses. On the other hand, IL-1β and TNF-α significantly increased the mRNA expression of inflammatory mediators IL-6, IL-8, inducible nitric oxide synthase (iNOS), prostaglandin-endoperoxide synthase 2 (PTGS2) and matrix metalloproteinases (MMP1, MMP3, and MMP13). The cytokine-induced gene expression in the NPs was ameliorated with EGCG. This study provides a proof of concept that inflammatory NP cultures, with appropriate containment, can be useful for the discovery and evaluation of molecular therapeutic strategies against early degenerative disc disease.

Resveratrol attenuates neuropathic pain through balancing pro-inflammatory and anti-inflammatory cytokines release in mice

Anti-inflammatory activity of resveratrol has been widely studied, while its beneficial effect on the management of neuropathic pain, a refractory chronic syndrome with pro-inflammation implicated in, is very little investigated. In the present study, the effects of different doses and various time window of administration of resveratrol were explored in a neuropathic mouse model of chronic constriction injury (CCI) of the sciatic nerve. It was demonstrated that pretreatment of resveratrol (5, 10, 20 and 40 mg/kg) for 7 consecutive days before CCI did not alleviate neuropathic pain, while it clearly relieved the pain when administrated after CCI and such pain relief effect was more pronounced when administrated right after the peak of pain symptom at day 7 after CCI, as evidenced by the alleviation of thermal hyperalgesia and mechanical allodynia. Such a beneficial effect of resveratrol was in a dose-dependent manner. Mechanistic study showed that resveratrol repressed the expression of pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6, and promoted the expression of anti-inflammatory cytokine IL-10 at the same time, which was further confirmed in a cell model of microglia. It was also shown that neuropathic pain inversely correlated with pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6, but not with anti-inflammatory cytokine IL-10 in all experimental mice from Spearman correlation coefficient. Our study reveals that resveratrol displays a significant neuropathic pain relief effect and paved a way for novel treatment of chronic pain.

Combined effect of 17β-estradiol and resveratrol against apoptosis induced by interleukin-1β in rat nucleus pulposus cells via PI3K/Akt/caspase-3 pathway

Background: In previous studies, both 17β-estradiol (E2) and resveratrol (RES) were reported to protect intervertebral disc cells against aberrant apoptosis. Given that E2 has a better anti-apoptotic effect with more cancer risk and RES has an anti-apoptotic effect with less cancer risk, the combined use of E2 with RES is promising in developing clinical therapies to treat apoptosis-related diseases such as intervertebral disc degeneration in the future. Objective: The purpose of this study was to explore the combined effect of E2 with RES on rat nucleus pulposus cells and the underlying mechanisms. Methods: TUNEL assay and FACS analysis were used to determine apoptotic incidence of nucleus pulposus cells. MTS assay was used to determine cell viability, and cellular binding assay was used to determine cell-ECM (extracellular matrix) ability. Real-time quantitative RT-PCR was to determine mRNA level of target genes. And Western blot was used to determine the protein level. Results: Both E2 and RES decreased apoptotic incidence when used singly; interestingly, they decreased apoptosis more efficiently when used combinedly. Meanwhile, E2 and RES combined together against the decrease of cell viability and binding ability resulting from IL-1β cytotoxicity. As well, activated caspase-3 was suppressed by the combined effect. Furthermore, IL-1β downregulated expression level of type II collagen and aggrecan (standing for anabolism), while upregulated MMP-3 and MMP-13 (standing for catabolism). However, the combined use of E2 with RES effectively abolished the above negative effects caused by IL-1β, better than either single use. Finally, it turned out to be that E2 and RES combined together against apoptosis via the activation of PI3K/Akt/caspase-3 pathway. Conclusion: This study presented that IL-1β induced aberrant apoptosis, which was efficiently resisted by the combined use of E2 with RES via PI3K/Akt/caspase-3 pathway.

Thalidomide represses inflammatory response and reduces radiculopathic pain by inhibiting IRAK-1 and NF-κB/p38/JNK signaling

Intervertebral disc (IVD) disease, the most common cause of disc failure and low back pain, is characterized by age-related changes in the adult disc. In this study we aimed to analyze the potential of thalidomide for the treatment of IVD disease, through identifying and explaining its anti-inflammatory and anti-catabolic activity in both in vitro IVD cell culture and in vivo animal model. Inflammatory response was induced by IL-1β, then the activity and expression of inflammatory mediators and pathways were assessed in the presence or absence of thalidomide. The p38 inhibitor SB203580 was also used to investigate the involvement of the MAPK pathway in the observed effects. Moreover the analgesic properties of thalidomide were analyzed by the von Frey filament test in Sprague-Dawley rats. Our results indicated that thalidomide significantly inhibited the expression of pro-inflammatory mediators and matrix metalloproteinases in vitro, as well as radiculopathic pain in vivo, most probably by modulation of the activity of IRAK-1 and its downstream effectors p38, JNK and NF-κB. Our current study strongly supports the potential of thalidomide for the treatment of pain and inflammation in degenerative disc disease.

Excessive reactive oxygen species are therapeutic targets for intervertebral disc degeneration

INTRODUCTION

Oxidative stress has been reported to be involved in numerous human diseases, including musculoskeletal disorders such as osteoarthritis. However, the interaction between intervertebral disc (IVD) degeneration and oxidative stress is not well understood. The purpose of the present study was to elucidate the contribution of oxidative stress to IVD degeneration and the efficacy of antioxidant treatment for degenerative discs.

METHODS

The expression level of an oxidative stress marker, nitrotyrosine, was assessed by immunohistochemistry and Western blotting. For evaluating intracellular reactive oxygen species (ROS) levels and oxidative stress in rat annulus fibrosus (AF) cells, flow cytometry and luciferase assay with an OKD48 construct were performed. The grade of IVD degeneration was assessed by magnetic resonance imaging and histological analysis.

RESULTS

A high frequency of nitrotyrosine-positive cells was observed in rat and human degenerative discs. mRNA expression of catabolic factors such as tumor necrosis factor-alpha (TNF-alpha), matrix metalloprotease-3 (MMP-3), and cyclooxygenase-2 (COX-2) was significantly induced by treatment with H2O2 or buthionine sulfoximine, whereas that of aggrecan, an important chondrogenic proteoglycan, was reduced in a dose-dependent manner. Treatment with mitogen-activated protein kinase (MAPK) inhibitors blocked the inductive effect of excessive ROS on COX-2 mRNA expression. Western blotting confirmed the phosphorylation of MAPKs in H2O2 and BSO-treated AF cells. Conversely, we showed that TNF-α induced oxidative stress with increased intracellular ROS levels in AF cells. Treatment with the antioxidant N-acetyl cysteine (NAC) abrogated the catabolic effect of excessive ROS and TNF-alpha in vitro. Finally, we showed that oral administration of NAC prevented IVD degeneration in rat degenerative model.

CONCLUSIONS

A positive feedback loop was formed between excessive ROS and TNF-alpha in AF cells. Thus, oxidative stress contributes to the progression of IVD degeneration and NAC can be a therapeutic option for IVD degeneration.

IL-1β promotes ADAMTS enzyme-mediated aggrecan degradation through NF-κB in human intervertebral disc

Background

The purpose of this study is to investigate IL-1β regulation of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4 and ADAMTS-5) expression through nuclear factor kappa B (NF-κB) in human nucleus pulposus (NP) cells.

Methods

qRT-PCR and Western blot were used to measure ADAMTS expression. Transfections and gene silencing were used to determine the role of NF-κB on cytokine-mediated ADAMTS expression and its role in aggrecan degradation.

Results

IL-1β increased ADAMTS expression in NP cells. Treatment with NF-κB inhibitors abolished the inductive effect of the cytokines on ADAMTS expression. Silencing of p65 confirmed their role in IL-1β-dependent ADAMTS-4 and ADAMTS-5 expression and aggrecan degradation.

Conclusions

By controlling the activation of NF-κB signaling, IL-1β modulates the expression of ADAMTS in NP cells. To our knowledge, this is the first study that shows the contribution of both ADAMTS-4 and ADAMTS-5 to aggrecan degradation in human NP cells.

Inflammation in intervertebral disc degeneration and regeneration

Intervertebral disc (IVD) degeneration is one of the major causes of low back pain, a problem with a heavy economic burden, which has been increasing in prevalence as populations age. Deeper knowledge of the complex spatial and temporal orchestration of cellular interactions and extracellular matrix remodelling is critical to improve current IVD therapies, which have so far proved unsatisfactory. Inflammation has been correlated with degenerative disc disease but its role in discogenic pain and hernia regression remains controversial. The inflammatory response may be involved in the onset of disease, but it is also crucial in maintaining tissue homeostasis. Furthermore, if properly balanced it may contribute to tissue repair/regeneration as has already been demonstrated in other tissues. In this review, we focus on how inflammation has been associated with IVD degeneration by describing observational and in vitro studies as well as in vivo animal models. Finally, we provide an overview of IVD regenerative therapies that target key inflammatory players.