The bacteria-positive proportion in the disc tissue samples from surgery: a systematic review and meta-analysis

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

STUDY DESIGN

Animal laboratory study.

OBJECTIVE

This study investigated the effects of Cutibacteriumacnes and Staphylococcusepidermidis on the lumbar discs of rabbits, as well as the outcomes of combined infection.

SUMMARY OF BACKGROUND DATA

Many studies have indicated that bacterial infections are associated with lumbar disc degeneration (LDD). The most commonly cultured bacteria from disc tissues are C. acnes and S. epidermidis .

METHODS

New Zealand white rabbits (n=40) were randomly divided into control, C. acnes , S. epidermidis , and C. acnes plus S. epidermidis ( i.e. , combined) groups. All groups except the control were injected with 25 μL of saline at L4-L5 and 25 μL of bacteria (1×10 7 CFU/mL) at L5-L6. All injections were performed under x-ray guidance. Weight measurements, haematological evaluations, and magnetic resonance imaging were performed after 4, 8, and 12 weeks. Histological examination and gene expression detection were performed 12 weeks after surgery.

RESULTS

Inflammatory factors in the blood and weight did not differ among the groups after 4, 8, and 12 weeks ( P >0.05). However, after 4 weeks, LDD occurred in the C. acnes group, and discitis occurred in the S. epidermidis and combined groups, all of which worsened after 8 weeks. After 12 weeks, the nucleus pulposus (NP) protruded and compressed the spinal cord in the C. acnes group, and tissue staining showed decreased NP tissue and cartilaginous endplate fracture. In the S. epidermidis and combined groups, the discitis was more confined, but tissue staining revealed a significant decrease in NP tissue, and loss of the normal disc structure.

CONCLUSIONS

In the early stage of infection in rabbits, C. acnes caused LDD, and S. epidermidis caused discitis. Coinfection with C. acnes and S. epidermidis caused discitis but was more limited in scope than infection with S. epidermidis alone.

Landscape of the Lumbar Cartilaginous End Plate Microbiota and Metabolites in Patients with Modic Changes

BACKGROUND

Modic changes (MCs), vertebral end plate and bone marrow damage observed by magnetic resonance imaging, are an independent risk factor for low back pain. The compositions of and interaction between microbiota and metabolites in the lumbar cartilaginous end plates (LCEPs) of patients with MCs have not been identified.

METHODS

Patients with lumbar disc degeneration who were undergoing lumbar spinal fusion surgery were recruited between April 2020 and April 2021. LCEPs were collected for 16S rRNA sequencing and liquid chromatography-mass spectrometry (LC/MS)-based targeted metabolomic profiling. Of the 54 patients recruited, 24 had no MCs and 30 had changes classified as Modic type 2 or 3. The primary goal was to identify specific genera of microbiota associated with MCs, and secondary goals included investigating differences in metabolites between patients with and without MCs and exploring the correlation between these metabolites and microorganisms.

RESULTS

Investigation of the microbiota community structure revealed that both alpha diversity and beta diversity were significantly different between patients with and without MCs, and the abundances of 26 genera were significantly different between these 2 groups. Metabolomic analysis revealed that 26 metabolites were significantly different between the 2 groups. The unsaturated fatty acid pathway was found to be the main pathway related to MCs. Multiomic correlation analysis suggested that Caulobacteraceae (unclassified) and Mycobacterium, Clostridium, Blautia, and Bifidobacterium at the genus level were linked to dysregulation of fatty acid metabolism, contributing to the pathogenesis of MCs.

CONCLUSIONS

Our study represents a foundational effort to examine the landscape of the microbiota and metabolites in patients with MCs, informing future studies on the pathogenesis of and targeted therapy for MCs.

LEVEL OF EVIDENCE

Prognostic Level II . See Instructions for Authors for a complete description of levels of evidence.

Risk factors associated with low-grade virulent infection in intervertebral disc degeneration: a systematic review and meta-analysis

BACKGROUND

An increasing number of research indicates an association between low-grade bacterial infections, particularly those caused by Propionibacterium acnes (P. acnes), and the development of intervertebral disc degeneration (IDD). However, no previous meta-analysis has systematically assessed the risk factors for low-grade bacterial infections that cause IDD.

PURPOSE

This study reviewed the literature to evaluate the risk factors associated with low-grade bacterial infection in patients with IDD.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

The systematic literature review was conducted using the PubMed, Web of Science, Embase, and Cochrane Library databases. Eligible articles explicitly identified the risk factors for low-grade bacterial infections in IDD patients. Patient demographics and total bacterial infection rates were extracted from each study. Meta-analysis was performed using random- or fixed-effects models, with statistical analyses conducted using Review Manager (RevMan) 5.4 software.aut.

RESULTS

Thirty-three studies involving 4,109 patients were included in the meta-analysis. The overall pooled low-grade bacterial infection rate was 30% (range, 24%-37%), with P. acnes accounting for 25% (range, 19%-31%). P. acnes constituted 66.7% of bacteria-positive discs. Fourteen risk factors were identified, of which 8 were quantitatively explored. Strong evidence supported male sex (odds ratio [OR] = 2.15; 95% confidence interval [CI]=1.65-2.79; p<.00001) and Modic changes (MCs) (OR=3.59; 95% CI=1.68-7.76; p=.0009); moderate evidence of sciatica (OR=2.31; 95% CI=1.33-4.00; p=.003) and younger age (OR=-3.47; 95% CI=-6.42 to -0.53; p=.02). No evidence supported previous disc surgery, MC type, Pfirrmann grade, smoking, or diabetes being risk factors for low-grade bacterial infections in patients with IDD.

CONCLUSIONS

Current evidence highlights a significant association between IDD and low-grade bacterial infections, predominantly P. acnes being the most common causative agent. Risk factors associated with low-grade bacterial infections in IDD include male sex, MCs, sciatica, and younger age.

Bacterial growth in patients with low back pain and Modic changes: protocol of a multicentre, case-control biopsy study

INTRODUCTION

Bacterial infection and Modic changes (MCs) as causes of low back pain (LBP) are debated. Results diverged between two randomised controlled trials examining the effect of amoxicillin with and without clavulanic acid versus placebo on patients with chronic LBP (cLBP) and MCs. Previous biopsy studies have been criticised with regard to methods, few patients and controls, and insufficient measures to minimise perioperative contamination. In this study, we minimise contamination risk, include a control group and optimise statistical power. The main aim is to compare bacterial growth between patients with and without MCs.

METHODS AND ANALYSIS

This multicentre, case-control study examines disc and vertebral body biopsies of patients with cLBP. Cases have MCs at the level of tissue sampling, controls do not. Previously operated patients are included as a subgroup. Tissue is sampled before antibiotic prophylaxis with separate instruments. We will apply microbiological methods and histology on biopsies, and predefine criteria for significant bacterial growth, possible contamination and no growth. Microbiologists, surgeons and pathologist are blinded to allocation of case or control. Primary analysis assesses significant growth in MC1 versus controls and MC2 versus controls separately. Bacterial disc growth in previously operated patients, patients with large MCs and growth from the vertebral body in the fusion group are all considered exploratory analyses.

ETHICS AND DISSEMINATION

The Regional Committees for Medical and Health Research Ethics in Norway (REC South East, reference number 2015/697) has approved the study. Study participation requires written informed consent. The study is registered at ClinicalTrials.gov (NCT03406624). Results will be disseminated in peer-reviewed journals, scientific conferences and patient fora.

TRIAL REGISTRATION NUMBER

NCT03406624.

Pyogenic spondylodiscitis in HIV-positive patients under antiretroviral therapy: A case series

Background: The incidence of pyogenic spondylodiscitis has been increasing in countries of Europe and North America, probably due to an increasing number of persons with risk factors for this infection. It is unclear whether HIV infection in the era of antiretroviral therapy (ART) increases the risk for spondylodiscitis. Method: We present 7 cases of pyogenic spondylodiscitis of the cervical, thoracic, and lumbar spine in six individuals living with HIV under ART with suppressed viral load. Results: All patients presented with severe non-radicular pain and elevated inflammatory markers. Diagnosis was confirmed by magnetic resonance imaging (MRI) scan and isolation of the pathogen. Staphylococcus aureus was the causative pathogen in five patients. One patient suffered from an infection with Klebsiella pneumoniae followed by a mixed infection with Cutibacterium acnes and Bacillus circulans 18 months later. All patients needed surgical intervention, and the mean duration of antibiotic treatment was 17 weeks (range 12-26). Five patients recovered fully, including two persons who also suffered from endocarditis. One patient died from multi-organ failure. Conclusion: Spondylodiscitis may be seen more frequently in persons living with HIV as they grow older and suffer from comorbidities which put them at risk for this infection. HIV physicians should be aware of the infection and its risk factors.

Modic change is associated with increased BMI but not autoimmune diseases in TwinsUK

PURPOSE

Low back pain (LBP) is one of the largest causes of morbidity worldwide. The aetiology of LBP is complex, and many factors contribute to the onset. Bone marrow lesions within the vertebra adjacent to an intervertebral degenerate disc named Modic change (MC) have been suggested as a diagnostic subgroup of LBP. Autoimmune response has been proposed to be one of the causes that promote the development of MC. The aim of the current investigation is to assess prevalence and severity of MC and LBP in participants with an autoimmune disease diagnosis in a well-documented cohort of adult twin volunteers.

METHODS

Multivariate generalized mixed linear models (GLMM) were implemented in order to calculate the association between having an autoimmune disorder and MC prevalence, width and severe and disabling LBP. The model was corrected for family structure as well as for covariates such as age, BMI and smoking.

RESULTS

No association was found between diagnosis of autoimmune disorder and MC. Interestingly, BMI was independently associated with MC width but not to MC prevalence. These results help to shed light on the relationship between MC and autoimmunity as well as the role of BMI in the development of the lesions.

CONCLUSION

This study is the first to examine autoimmune disorders and MC prevalence in a large, population-based female cohort. The study was well powered to detect a small effect. No association was found between having a diagnosis of one or more autoimmune conditions and MC prevalence, width or LBP.

Colonization of intervertebral discs by Cutibacterium acnes in patients with low back pain: Protocol for an analytical study with microbiological, phenotypic, genotypic, and multiomic techniques

Lumbar disc degeneration (LDD) and low back pain (LBP) are two conditions that are closely related. Several studies have shown Cutibacterium acnes colonization of degenerated discs, but whether and how these finding correlates with LBP is unknown. A prospective study was planned to identify molecules present in lumbar intervertebral discs (LLIVD) colonized by C. acnes in patients with LDD and LBP and correlate them with their clinical, radiological, and demographic profiles. The clinical manifestations, risk factors, and demographic characteristics of participants undergoing surgical microdiscectomy will be tracked. Samples will be isolated and pathogens found in LLIVD will be characterized phenotypically and genotypically. Whole genome sequencing (WGS) of isolated species will be used to phylotype and detect genes associated with virulence, resistance, and oxidative stress. Multiomic analyses of LLIVD colonized and non-colonized will be carried out to explain not only the pathogen's role in LDD, but also its involvement in the pathophysiology of LBP. This study was approved by the Institutional Review Board (CAAE 50077521.0.0000.5258). All patients who agree to participate in the study will sign an informed consent form. Regardless of the study's findings, the results will be published in a peer-reviewed medical journal. Trials registration number NCT05090553; pre-results.

Wogonin, a Bioactive Ingredient from Huangqi Guizhi Formula, Alleviates Discogenic Low Back Pain via Suppressing the Overexpressed NGF in Intervertebral Discs

Purpose

To investigate whether wogonin, a key bioactive ingredient of Huangqi Guizhi formula (HQGZ formula; a Traditional Chinese Medicine herbal formula) according to network pharmacology analysis, has analgesic effects on discogenic low back pain (LBP) via regulating the nerve growth factor (NGF) in intervertebral discs (IVDs).

Methods

The lumbar IVDs of rats were punctured to discogenic LBP, and the therapeutic effect of orally administrated HQGZ for discogenic LBP was investigated by measuring mechanical and cold allodynia and histological analysis. A network pharmacology analysis was conducted to search for bioactive ingredients from the HQGZ formula, and wogonin was suggested to be the most possible bioactive ingredient for LBP treatment. Subsequently, the analgesic effect of wogonin was investigated in the LBP model, and the gene expression of propain peptides in the bilateral dorsal root ganglia was analyzed using RT-PCR. Finally, immunohistochemical staining was performed for NGF expression of NGF in the IVDs to determine whether wogonin treatment would ameliorate NGF-induced LBP.

Results

Oral administration of HQGZ for two weeks significantly ameliorated puncture-induced IVD degeneration (IDD) and LBP. In addition, the network pharmacology analysis revealed that wogonin, quercetin, and kaempferol were the potential candidate components of HQGZ for LBP treatment. Furthermore, we proved that wogonin had significant analgesic effects in the LBP model. Finally, wogonin was demonstrated to suppress the upregulated NGF in the IVD and ameliorate NGF-induced LBP in rats.

Conclusions

The HQGZ formula has significant analgesic effects for LBP. In addition, the bioactive ingredient of wogonin was extracted from HQGZ and ameliorated LBP by suppressing the overexpressed NGF in degenerated IVDs. Therefore, wogonin has potential to be alternative treatment for LBP in clinical.

Comparative metagenomic analysis of human intervertebral disc nucleus pulposus and cartilaginous end plates

Study design

The diversity of microflora inhabiting endplate (EP) and nucleus pulposus (NP) tissues of human intervertebral disc (IVD) was profiled through NGS-supported 16S rRNA amplicon sequencing. Sixteen EP and their corresponding NP were excised from the brain-dead voluntary organ donors with no clinical history of low back pain, and 12 herniated and 8 degenerated NP tissues isolated from the patients undergoing spinal surgery were subjected to study the alteration in the microbial diversity.

Objective(s)

To understand in normal IVD, whether the colonization of bacteria to the NP is through the EP in discs with intact annulus fibrosus. To identify significantly differing microbial population(s) between normal and diseased IVD (NP).

Background of the study

There is increasing evidence for subclinical infection by fastidious low, growing bacteria to be a cause of disc degeneration. Although the presence of bacteria in NP has been reported well in literature, the source of bacteria is not clearly proved as the disc is avascular in healthy condition. Documentation of similar bacterial populations in the EP and NP may add proof that bacterial inoculation of NP occurs via the EP.

Materials and methods

Sixteen EP and their corresponding NP excised from brain-dead voluntary organ donors with no history of back pain and 20 diseased discs collected from patients undergoing microdiscectomy/fusion surgery were used for profiling microbiome through 16S rRNA amplicon sequencing using primers specific for V1-V9 hypervariable regions. Changes in bacterial diversity and abundance were analysed to identify the key microbial populations in normal IVD NP and EP tissues and those significantly altered in diseased IVD (NP).

Results

NP and EP shared a similar spectrum of microbiome but with varying abundance. The five dominant phyla identified were Proteobacteria, Firmicutes, Actinobacteria, OD1, and Bacteroidetes. Proteobacteria was found to be the most abundant phyla in both NP (62%) and EP (53%) of the normal IVD. This was followed by Firmicutes (16%), Actinobacteriota (11%), OD1 (Parcubacteria) (7.6%), and Bacteroidetes (2%) in NP and Firmicutes (23.4%), OD1 (Parcubacteria) (17.6%), Actinobacteriota (2.8%), and Bacteroidetes (2.6%) in EP, respectively. Under diseased conditions, Proteobacteria (68%) was dominant when compared with other phyla. However, there was no significant difference in the abundance of Proteobacteria between the normal and diseased discs. Interestingly, the other dominant phyla such as Firmicutes (Normal-NP: 16.2%; Diseased-NP: 4.02%) and Actinobacteria (Normal-NP: 11%; Diseased-NP: 0.99%) showed a significant reduction in degenerated discs. To understand the key microbial populations that are significantly altered during disease, correlation analysis was performed among the three phyla, which revealed a negative correlation in the ratio of Actinobacteria + Firmicutes vs. Proteobacteria (p = 0.001) in DD.

Conclusion

Results of our study clearly demonstrated a similar bacterial diversity but with varying abundance between the EP and NP, suggesting the existence of the endplate–nucleus pulposus axis in the normal IVD microbiome. Further, our results have indicated that the changes in the abundance of Actinobacteria + Firmicutes vs. Proteobacteria during DDD need further investigation.

Anaerobic spondylodiscitis: a retrospective analysis

Background

This retrospective study analyzed the clinical characteristics and outcomes of patients with anaerobic spondylodiscitis.

Methods

From a total of 382 patients with infectious spondylodiscitis, nine patients (2.4%; two male and seven female with an average age of 67 years) with anaerobic spondylodiscitis between March 2003 and March 2017 were analyzed.

Results

Most of the patients (77.8%) initially presented with afebrile back pain. Hematogenous spread occurred in seven patients and postoperative infection in two patients. Bacteroid fragilis was the most common pathogen isolated from three patients. Atypical radiographic characteristics, including a vertebral fracture with the preservation of disk height or coexisting spondylolytic spondylolisthesis, occurred in four patients with hematogenous anaerobic spondylodiscitis. The eradication rate of anaerobic infection was significantly higher in the patients with hematogenous infection than in those with postoperative infection (100% vs. 0%, p = 0.0476). Anaerobic spondylodiscitis accounted for 2.4% of cases of infectious spondylodiscitis and predominantly affected the female patients.

Conclusions

Diagnostic delay may occur because of atypical spinal radiographs if the patient reports only back pain but no fever. Anaerobic infection following elective spinal instrumentation has a higher recurrence rate.

Intervertebral Disc Degeneration and Low Back Pain Depends on Duration and Magnitude of Axial Compression

Purpose

The pathological role of axial stress in intervertebral disc degeneration (IDD) is controversial, and there was no quantified study until now. Here, we tried to clarify the correlation between IDD or low back pain (LBP) and axial stress at different duration and magnitude in vitro and in vivo.

Method

In vitro, the gene expression of aggrecan, matrix metalloproteinase-3 (MMP3), calcitonin gene-related peptide (CGRP), and substance P (SP) was measured when nucleus pulposus cells (NPCs) were compressed under gradual severity. In vivo, a measurable Ilizarov-type compression apparatus was established for single coccygeal (Co) intervertebral disc (IVD) compression of Co7-8 in mouse. Gradient stress was placed at 0.4 Mpa (mild), 0.8 Mpa (moderate), and 1.2 Mpa (severe) for three days to investigate the effect of the magnitude of axial stress. Additionally, mild compression with 3, 7, and 14 days was used to determine the effect of the duration of axial stress. Subsequently, we evaluated the severity of IDD and LBP by radiological X-ray film; histological examination with H&E staining; immunohistochemical analysis with collagen II, aggrecan, and CGRP staining; and western blot analysis with collagen II, aggrecan, MMP-3, and interleukin-1β (IL-1β).

Results

When NPCs suffered gradual increased mechanical stress, the cells exhibited gradual downregulated expression of extracellular matrix (ECM)-related gene of aggrecan, upregulated expression of IDD-related gene of MMP3, and LBP-related gene of CGRP and SP. In the meantime, with different magnitudes of axial stress, the IVD showed progressively severe IDD and LBP, with gradual narrowing intervertebral height, destruction of IVD anatomy, decreased ECM, and increased catabolic factors and proalgesic peptides.

Conclusion

Axial compression is one of the critical pathological factors to cause IDD and LBP, and there was a strong positive correlation depended on the duration and magnitude of compression.

Evidence for infection in intervertebral disc degeneration: a systematic review

Purpose

Back pain is a major problem worldwide and is linked to intervertebral disc degeneration and Modic change. Several studies report growth of bacteria following extraction of degenerate discs at spine surgery. A pathophysiological role for infection in back pain has been proposed.

Method

We conducted a PRISMA systematic review. MEDLINE, PubMed, Scopus and Web of Science were searched with the terms Modic change, intervertebral dis*, bacteria, microb*, and infect*. Date limits of 2001–2021 were set. Human studies investigating the role of bacteria in disc degeneration or Modic change in vertebrae were included.

Results

Thirty-six articles from 34 research investigations relating to bacteria in human degenerate discs were found. Cutibacterium acnes was identified in pathological disc material. A ‘candidate bacterium’ approach has been repeatedly adopted which may have biased results to find species a priori, with disc microbial evidence heavily weighted to find C. acnes.

Conclusion

Evidence to date implicates C. acnes identified through culture, microscopy and sequencing, with some suggestion of diverse bacterial colonisation in the disc. This review found studies which used culture methods and conventional PCR for bacterial detection.

Further agnostic investigation using newer methods should be undertaken.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00586-021-07062-1.

Influence of endplate avulsion and Modic changes on the inflammation profile of herniated discs: a proteomic and bioinformatic approach

PURPOSE

The aim of this observational radiographic and proteomic study is to explore the influence of both Modic change (MC) and endplate avulsion (EPA) on the inflammation profile of herniated discs using a proteomic and bioinformatics approach.

METHODS

Fifteen nucleus pulposus (NP) harvested from surgery underwent LC-MS/MC analysis, the proteome was subsequently scanned for inflammatory pathways using a bioinformatics approach. All proteins that were identified in inflammatory pathways and Gene Ontology and present in > 7 samples were integrated in a multiple regression analysis with MC and EPA as predictors. Significant proteins were imputed in an interaction and pathway analysis.

RESULTS

Compared to annulus fibrosus tear (AFT), six proteins were significantly altered in EPA: catalase, Fibrinogen beta chain, protein disulfide-isomerase, pigment epithelium-derived factor, osteoprotegerin and lower expression of antithrombin-III, all of which corresponded to an upregulation of pathways involved in coagulation and detoxification of reactive oxygen species (ROS). Moreover, the presence of MC resulted in a significant alteration of nine proteins compared to patients without MC. Patients with MC showed a significantly higher expression of clusterin and lumican, and lower expression of catalase, complement factor B, Fibrinogen beta chain, protein disulfide-isomerase, periostin, Alpha-1-antitrypsin and pigment epithelium-derived factor. Together these altered protein expressions resulted in a downregulation of pathways involved in detoxification of ROS, complement system and immune system. Results were verified by Immunohistochemistry with CD68 cell counts.

CONCLUSION

Both EPA and MC status significantly influence disc inflammation. The beneficial inflammatory signature of EPA illustrates that endplate pathology does not necessarily have to worsen the outcome, but the pathological inflammatory state is dependent on the presence of MC.

Study protocol: effect of infection, Modic and inflammation on clinical outcomes in surgery for radiculopathy (EIMICOR)

BACKGROUND

Evidence indicates that inflammatory processes are involved in radicular pain as well as in resorption of herniated disc tissue. Furthermore there are indications that the presence of vertebral end plate pathology (Modic changes; MC) is associated with a negative effect on inflammation. It is hypothesized that in patients with MC, the (possibly bacterial induced) inflammation will be accompanied by pro inflammatory cytokines that worsen the outcome, and that in patients without MC, the inflammation is accompanied by cytokines that induce a resorption process to accelerate recovery.

METHODS

This prospective cohort study will include 160 lumbar and 160 cervical patients (total of 320), which are scheduled for surgery for either a lumbar or cervical herniated disc with ages between 18 and 75. The main and interaction effects of local bacterial infection (culture), inflammatory cells in disc material (immunohistology), MC (MRI), and blood biomarkers indicating inflammation or infection (blood sample evaluation) will be evaluated. Clinical parameters to be evaluated are leg pain on the 11 point NRS pain scale, Oswestry (lumbar spine) or Neck (cervical spine) Disability Index, Global Perceived Recovery, Womac Questionnaire, and medication status, at baseline, and after 6, 16, 26 and 52 weeks.

DISCUSSION

Gaining insight in the aetiology of pain and discomfort in radiculopathy caused by a herniated disc could lead to more effective management of patients. If the type of inflammatory cells shows to be of major influence on the rate of recovery, new immunomodulating treatment strategies can be developed to decrease the duration and intensity of symptoms. Moreover, identifying a beneficial inflammatory response in the disc through a biomarker in blood could lead to early identification of patients whose herniations will resorb spontaneously versus those that require surgery.

TRIAL REGISTRATION

prospectively enrolled at trialregister.nl, ID: NL8464 .

Propionibacterium acnes Accelerates Intervertebral Disc Degeneration by Inducing Pyroptosis of Nucleus Pulposus Cells via the ROS-NLRP3 Pathway

Our previous study verified the occurrence of Propionibacterium acnes (P. acnes), a low-virulence anaerobic bacterium, latently residing in degenerated intervertebral discs (IVDs), and the infection had a strong association with IVD degeneration. We explored whether P. acnes induces nucleus pulposus cell (NPC) pyroptosis, a more dangerous cell death process than apoptosis, and accelerates IVD degeneration via the pyroptotic products interleukin- (IL-) 1β and IL-18. After coculturing with P. acnes, human NPCs showed significant upregulation of NOD-like receptor 3 (NLRP3), cleaved IL-1β, cleaved caspase-1, and cleaved gasdermin D in response to the overexpression of IL-1β and IL-18 in a time- and dose-dependent manner. In addition, the gene expression of inflammatory factors and catabolic enzymes significantly increased in normal NPCs when cocultured with pyroptotic NPCs in a transwell system, and the adverse effects were inhibited when NPC pyroptosis was suppressed. Furthermore, inoculation of P. acnes into the IVDs of rats caused significant pyroptosis of NPCs and remarkable IVD degeneration. Finally, coculture of NPCs with P. acnes induced the overexpression of reactive oxygen species (ROS) and NLRP3, while inhibition of both factors reduced NPC pyroptosis. Therefore, P. acnes induces NPC pyroptosis via the ROS-NLRP3 signaling pathway, and the pyroptotic NPCs cause an IVD degeneration cascade. Targeting the P. acnes-induced pyroptosis of NPCs may become an alternative treatment strategy for IVD degeneration in the future.

Icariin Ameliorates Lower Back Pain in Rats via Suppressing the Secretion of Cytokine-Induced Neutrophil Chemoatractant-1

Purpose

To investigate whether icariin (ICA), a well-known medicine extracted from the stem and leaf of Epimedium brevicornum Maxim, had analgesic effect on lower back pain (LBP) in rats.

Methods

In a puncture-induced LBP rat model, the severity of LBP was quantified using the paw/foot withdrawal threshold method after intragastric administration of ICA at a dosage of 50 mg/kg/d or 100 mg/kg/d. The pain-related peptides of substance P (SP) and calcitonin gene-related peptide (CGRP) were also measured in intervertebral disc (IVD) tissue using RT-PCR after ICA treatment. In addition, the expression of cytokine-induced neutrophil chemoattractant-1 (CINC-1) in IVD was quantified using RT-PCR and ELISA examination.

Results

ICA treatment resulted in a significant amelioration of mechanical allodynia in a dose-response manner, and the analgesic effect could last for two weeks even during the washout period. More importantly, the mechanism of analgesic pharmacological effect in ICA was to suppress the upregulated CINC-1, the homolog of IL-8 in rats, which is a crucial proalgesic factor contributing to LBP, in IVDs.

Conclusion

ICA is a novel herbal extract to relieve LBP, and it may be a promising alternative pain killer in the future.