Propionibacterium acnes Incubation in the Discs Can Result in Time-Dependent Modic Changes: A Long-Term Rabbit Model

Mrgprb2-mediated mast cell activation exacerbates Modic changes by regulating immune niches

Modic changes are radiographic features associated with microfracture, low-virulence organism infection and chronic inflammation with inflammatory cell infiltration in the vertebral endplate region. Mast cells, as innate immune cells similar to macrophages, are present in painful degenerated intervertebral discs. However, the involvement and mechanisms of mast cells in the development of Modic changes remain unclear. Herein, we found increased mast cell infiltration in samples from patients with Modic changes and in mouse models of Modic changes. To clarify the role of mast cells in the progression of Modic changes, we used mast cell-deficient (KITW-SH/W-SH) mice to construct a model of Modic changes and found that the severity of Modic changes in KITW-SH/W-SH mice was significantly lower than that in WT mice. These findings were further supported by the use of a mast cell-specific activator (compound 48/80) and a stabilizer (cromolyn). Furthermore, we found that mast cells were not activated via the classic IgE pathway in the Modic change models and that Mrgprb2 is the specific receptor for mast cell activation reported in recent studies. Then, we utilized Mrgprb2 knockout mice to demonstrate that Mrgprb2 knockout inhibited mast cell activation and thus reduced the degree of Modic changes. Transcriptomic sequencing revealed aberrant PI3K-AKT and MAPK pathway activation in the Mrgprb2-deficient mast cells. Additionally, Mrgpbrb2-activated mast cells regulate immune niches by recruiting macrophages, promoting M1 polarization and reducing M2 polarization, thereby promoting the progression of Modic changes. These findings suggest that mast cells may serve as a novel therapeutic target for addressing Modic changes.

Induction of cervical disc degeneration and discogenic pain by low concentration Propionibacterium acnes infection: an in vivo animal study

BACKGROUND

Although cervical intervertebral disc (IVD) degeneration is closely associated with neck pain, its cause remains unclear. In this study, an animal model of cervical disc degeneration and discogenic neck pain induced by a low concentration of Propionibacterium acnes (P. acnes-L) is investigated to explore the possible mechanisms of cervical discogenic pain.

METHODS

Cervical IVD degeneration and discitis was induced in 8-week-old male rats in C3-C6 IVDs through the anterior intervertebral puncture with intradiscal injections of low and high concentrations of P. acnes (P. acnes-L, n = 20 and P. acnes-H, n = 15) or Staphylococcus aureus (S. aureus, n = 15), compared to control (injection with PBS, n = 20). The structural changes in the cervical IVD using micro-CT, histological evaluation, and gene expression assays after MRI scans at 2 and 6 weeks post-modeling. The P. acnes-L induced IVD degeneration model was assessed for cervical spine MRI, histological degeneration, pain-like behaviors (guarding behavior and forepaw von Frey), nerve fiber growth in the IVD endplate region, and DRG TNF-α and CGRP.

RESULTS

IVD injection with P. acnes-L induced IVD degeneration with decreased IVD height and MRI T2 values. IVD injection with P. acnes-H and S. aureus both lead to discitis-like changes on T2-weighted MRI, trabecular bone remodeling on micro-CT, and osseous fusion after damage in the cartilage endplate adjacent to the injected IVD. Eventually, rats in the P. acnes-L group exhibited significant nociceptive hypersensitivity, nerve fiber ingrowth was observed in the IVD endplate region, inflammatory activity in the DRG was significantly increased compared to the control group, and the expression of the pain neurotransmitter CGRP was significantly upregulated.

CONCLUSION

P. acnes-L was validated to induce cervical IVD degeneration and discogenic pain phenotype, while P. acnes-H induced was identified to resemble septic discitis comparable to those caused by S. aureus infection.

Cartilaginous endplates: A comprehensive review on a neglected structure in intervertebral disc research

The cartilaginous endplates (CEP) are key components of the intervertebral disc (IVD) necessary for sustaining the nutrition of the disc while distributing mechanical loads and preventing the disc from bulging into the adjacent vertebral body. The size, shape, and composition of the CEP are essential in maintaining its function, and degeneration of the CEP is considered a contributor to early IVD degeneration. In addition, the CEP is implicated in Modic changes, which are often associated with low back pain. This review aims to tackle the current knowledge of the CEP regarding its structure, composition, permeability, and mechanical role in a healthy disc, how they change with degeneration, and how they connect to IVD degeneration and low back pain. Additionally, the authors suggest a standardized naming convention regarding the CEP and bony endplate and suggest avoiding the term vertebral endplate. Currently, there is limited data on the CEP itself as reported data is often a combination of CEP and bony endplate, or the CEP is considered as articular cartilage. However, it is clear the CEP is a unique tissue type that differs from articular cartilage, bony endplate, and other IVD tissues. Thus, future research should investigate the CEP separately to fully understand its role in healthy and degenerated IVDs. Further, most IVD regeneration therapies in development failed to address, or even considered the CEP, despite its key role in nutrition and mechanical stability within the IVD. Thus, the CEP should be considered and potentially targeted for future sustainable treatments.

Choosing the right animal model for osteomyelitis research: Considerations and challenges

Osteomyelitis is a debilitating bone disorder characterized by an inflammatory process involving the bone marrow, bone cortex, periosteum, and surrounding soft tissue, which can ultimately result in bone destruction. The etiology of osteomyelitis can be infectious, caused by various microorganisms, or noninfectious, such as chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO). Researchers have turned to animal models to study the pathophysiology of osteomyelitis. However, selecting an appropriate animal model that accurately recapitulates the human pathology of osteomyelitis while controlling for multiple variables that influence different clinical presentations remains a significant challenge. In this review, we present an overview of various animal models used in osteomyelitis research, including rodent, rabbit, avian/chicken, porcine, minipig, canine, sheep, and goat models. We discuss the characteristics of each animal model and the corresponding clinical scenarios that can provide a basic rationale for experimental selection. This review highlights the importance of selecting an appropriate animal model for osteomyelitis research to improve the accuracy of the results and facilitate the development of novel treatment and management strategies.

"Are we barking up the wrong tree? Too much emphasis on Cutibacterium acnes and ignoring other pathogens"- a study based on next-generation sequencing of normal and diseased discs

BACKGROUND

The majority of literature on bacterial flora in the disc stands disadvantaged in utilizing traditional culture methods and targeting a single bacterium, Cutibacterium acnes.

PURPOSE

Our objective was to document the diversity in the bacterial flora between normal and degenerated discs for shortlisting potential pathogens using next-generation genomic tools.

STUDY DESIGN

Experimental case-control study.

METHODS

Researchers employed 16S metagenome sequencing to profile bacterial diversity in magnetic resonance imaging normal healthy discs from brain-dead organ voluntary donors (n=20) and 40 degenerated disc samples harvested during surgery (Modic [MC]=20 and non-Modic [NMC]=20). The V3-V4 region was amplified using universal bacterial primers 341F and 806R, and the libraries were sequenced using Illumina NovoSeq 6000 platform. Statistical significance was set at bacteria with a minimum of 100 operational taxonomic unit (OTU) and present in at least 70% of the samples. The quality check-filtered reads were processed using the QIIME-2 pipeline. The OTU clustering and taxonomic classification were carried out for the merged reads using the Greengenes/SILVA reference database. Validation was done by identification of bacterial metabolites in samples using the liquid chromatography-mass spectrometry approach.

RESULTS

Abundant bacteria differing widely in diversity, as evidenced by Alfa and Beta diversity analysis, were present in all control and degenerative samples. The number of bacterial genera was 27 (14-gram-positive: 13-gram-negative) in the control group, 23 (10-gram-positive: 11-gram-negative) in the Modic group, and 16 (11-gram-positive: 5-gram-negative) in the non-Modic group. In the Modic group, gram-negative bacteria OTUs were found to be predominant (more than 50% of the total bacteria identified), whereas in control and non-Modic groups the OTUs of gram-positive bacteria were predominant. Species-level analysis revealed an abundance of opportunistic gram-negative pathogens like Pseudomonas aeruginosa, Sphingomonos paucibacillus, and Ochrobactrum quorumnocens in the discs with Modic changes, more than in non-Modic discs. The presence of bacterial metabolites and quorum-sensing molecules like N-decanoyl-L-homoserine lactone, 6-hydroxynicotinic acid, 2-aminoacetophenone, 4-hydroxy-3-polyprenylbenzoate, PE (16:1(9Z)/18:0) and phthalic acid validated the colonization and cell-cell communication of bacteria in disc ruling out contamination theory. Cutibacterium acnes was not the predominant bacteria in any of the three groups of discs and in fact was in the 16th position in the order of abundance in the control discs (0.72%), seventh position in the Modic discs (1.41%), and 12th position (0.53%) in the non-Modic discs.

CONCLUSION

This study identified a predominance of gram-negative bacteria in degenerated discs and highlights that Cutibacterium acnes may not be the only degeneration-causing bacteria. This may be attributed to the environment, diet, and lifestyle habits of the sample population. Though the study does not reveal the exact pathogen, it may pave the way for future studies on the subject.

CLINICAL SIGNIFICANCE

These findings invite further investigation into causal relationships of bacterial profile with disc degeneration phenotypes as well as phenotype-driven clinical treatment protocols.

The Effect of Cutibacterium acnes Infection on Nerve Penetration in the Annulus Fibrosus of Lumbar Intervertebral Discs via Suppressing Oxidative Stress

Modic changes (MCs) and low back pain are highly correlated and an economic burden to the society. Previous studies have shown that Cutibacterium acnes (C. acnes) infection can lead to MCs. The purpose of this study was to clarify whether and how C. acnes contributes to oxidative stress and nerve growth that potentially leads to low back pain. Neurons from the hippocampus or dorsal root ganglion (DRG) of Sprague-Dawley (SD) rats were cocultured with annulus fibrosus cells (AFCs) with or without the presence of the C. acnes supernatant in vitro. Cell viability, neurite length, oxidative stress, and neuro-related gene expression were examined. Furthermore, samples from the patients with MCs and SD rat model of MCs were used to validate the nerve growth results. Neurons from both the hippocampus and DRG showed neurites when cocultured with AFCs in the environment with/without the C. acnes supernatant. The average neurite length was significantly longer when exposed to the C. acnes supernatant in the hippocampal neuron (217.1 ± 90.0 μm versus 150.1 ± 68.1 μm in the control group) and in the DRG neuron (229.1 ± 91.3 μm versus 149.2 ± 64.8 μm in the control group). Hippocampal neurons showed upregulated expression levels of NeuN, Map2, and Psd95, while upregulation was only seen in Tuj-1 in DRG neurons. Suppressed oxidative stress could be observed using axon growth symbols. Degenerated disc structures and abnormal bone remodelling were found in animal models and clinical samples of MCs, with astrocytes, microglia, and neurons in the disc. Therefore, C. acnes infection was found to cause back pain in the presence of MCs by promoting nerve penetration into the annulus fibrosus by suppressing oxidative stress.

Sheep as a Potential Model of Intradiscal Infection by the Bacterium Cutibacterium acnes

The anaerobic bacterium Cutibacterium acnes has been increasingly linked to the development of degenerative disc disease (DDD), although causality is yet to be conclusively proven. To better study how this organism could contribute to the aetiology of DDD, improved animal models that are more reflective of human disc anatomy, biology and mechanical properties are required. Against this background, our proof-of concept study aimed to be the first demonstration that C. acnes could be safely administered percutaneously into sheep intervertebral discs (IVDs) for in vivo study. Following our protocol, two sheep were successfully injected with a strain of C. acnes (8.3 × 10⁶ CFU/disc) previously recovered from a human degenerative disc. No adverse reactions were noted, and at one-month post inoculation all triplicate infected discs in our first animal grew C. acnes, albeit at a reduced load (5.12 × 10⁴ to 6.67 × 10⁴ CFU/disc). At six months, no growth was detected in discs from our second animal indicating bacterial clearance. This pilot study has demonstrated the feasibility of safe percutaneous injection of C. acnes into sheep IVDs under fluoroscopic guidance. The design of follow-up sheep studies to investigate the potential of C. acnes to drive pathological changes within infected discs should now be pursued.

Pro-Inflammatory and Neurotrophic Factor Responses of Cells Derived from Degenerative Human Intervertebral Discs to the Opportunistic Pathogen Cutibacterium acnes

Previously, we proposed the hypothesis that similarities in the inflammatory response observed in acne vulgaris and degenerative disc disease (DDD), especially the central role of interleukin (IL)-1β, may be further evidence of the role of the anaerobic bacterium Cutibacterium (previously Propionibacterium) acnes in the underlying aetiology of disc degeneration. To investigate this, we examined the upregulation of IL-1β, and other known IL-1β-induced inflammatory markers and neurotrophic factors, from nucleus-pulposus-derived disc cells infected in vitro with C. acnes for up to 48 h. Upon infection, significant upregulation of IL-1β, alongside IL-6, IL-8, chemokine (C-C motif) ligand 3 (CCL3), chemokine (C-C motif) ligand 4 (CCL4), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), was observed with cells isolated from the degenerative discs of eight patients versus non-infected controls. Expression levels did, however, depend on gene target, multiplicity and period of infection and, notably, donor response. Pre-treatment of cells with clindamycin prior to infection significantly reduced the production of pro-inflammatory mediators. This study confirms that C. acnes can stimulate the expression of IL-1β and other host molecules previously associated with pathological changes in disc tissue, including neo-innervation. While still controversial, the role of C. acnes in DDD remains biologically credible, and its ability to cause disease likely reflects a combination of factors, particularly individualised response to infection.

Cutibacterium acnes is an intracellular and intra-articular commensal of the human shoulder joint

BACKGROUND

Cutibacterium acnes (C acnes) is a mysterious member of the shoulder microbiome and is associated with chronic postoperative complications and low-grade infections. Nevertheless, it is unclear whether it represents a contaminant or whether it accounts for true infections. Because it can persist intracellularly in macrophages at several body sites, it might in fact be an intra-articular commensal of the shoulder joint.

METHODS

In 23 consecutive, otherwise healthy patients (17 male, 6 female; 58 years) who had no previous injections, multiple specimens were taken from the intra-articular tissue during first-time arthroscopic and open shoulder surgery. The samples were investigated by cultivation, genetic phylotyping, and immunohistochemistry using C acnes-specific antibodies and confocal laser scanning microscopy.

RESULTS

In 10 patients (43.5%), cultures were C acnes-positive. Phylotype IA1 dominated the subcutaneous samples (71%), whereas type II dominated the deep tissue samples (57%). Sixteen of 23 patients (69.6%) were C acnes-positive by immunohistochemistry; in total, 25 of 40 samples were positive (62.5%). Overall, 56.3% of glenohumeral immunohistochemical samples, 62.5% of subacromial samples, and 75% of acromioclavicular (AC) joint samples were positive. In 62.5% of the tested patients, C acnes was detected immunohistochemically to reside intracellularly within stromal cells and macrophages.

DISCUSSION

These data indicate that C acnes is a commensal of the human shoulder joint, where it persists within macrophages and stromal cells. Compared with culture-based methods, immunohistochemical staining can increase C acnes detection. Phylotype II seems to be most prevalent in the deep shoulder tissue. The high detection rate of C acnes in osteoarthritic AC joints might link its intra-articular presence to the initiation of osteoarthritis.

Osteal Tissue Macrophages Are Involved in Endplate Osteosclerosis through the OSM-STAT3/YAP1 Signaling Axis in Modic Changes

Modic changes (MCs) are radiographic manifestations of lumbar degenerative diseases. Various types of MCs are often associated with endplate osteosclerosis. Osteal tissue macrophages (Osteomacs) were reported to be crucial for bone homeostasis and bone repair, but whether osteomacs participate in the endplate osteosclerosis in MCs remained unclear. In this study, we tried to explore the critical role of osteomacs in regulating osteogenesis in MCs. We collected MCs from patient samples and developed a Propionibacterium acnes-induced rat MCs model, using microcomputed tomography and immunohistochemistry to detect the endplate bone mass and distribution of osteomacs. In patients' MCs, osteomacs increased in endplate subchondral bone, especially in Modic type II. Endplate in Modic type III presented a stable osteosclerosis. In rat MCs model, osteomacs increased in the bone hyperplasia area but not in the inflammation area of the endplate region, whereas the distribution of osteomacs was consistent with the area of osteosclerosis. To further explore the functions of osteomacs in vitro, we isolated osteomacs using MACS technology and found osteomacs secreted oncostatin M (OSM) and strongly promoted osteoblast differentiation rather than osteoclast through the mechanism of OSM-mediated tyrosine phosphorylation and interaction of STAT3 and Yes-associated protein 1 (YAP1). STAT3 phosphorylation inhibition or YAP1 knockdown attenuated OSM-mediated osteoblast differentiation. Finally, we confirmed that blockade of OSM in vivo using anti-OSM-neutralizing Ab prevented endplate osteosclerosis in rat MCs model. Taken together, these findings confirmed that endplate osteosclerosis in MCs was accompanied by an increased number of osteomacs, which regulated osteogenesis via the OSM-STAT3/YAP1 signaling axis.

Propionibacterium acnes induces cartilaginous endplate degeneration by promoting MIF expression via the NF-κB pathway

Background

Propionibacterium acnes (P. acnes) is a novel pathogenic factor that contributes to cartilaginous endplate (CEP) degeneration. However, the underlying mechanism of P. acnes-induced CEP degeneration remains unclear. The objective of this study is to investigate the underlying mechanism of P. acnes-induced CEP degeneration.

Methods

We first examined MIF expression in degenerated human CEP samples by immunohistochemistry. We developed a P. acnes-induced rat model and detected MIF expression using immunohistochemistry. Additionally, we investigated the mechanism of P. acnes-induced CEP degeneration in CEP cells using western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

Results

We found that compared with the normal human CEP, the expression of MIF was increased in the degenerated human CEP. In a rat model, P. acnes induced CEP degeneration and upregulated MIF expression significantly. More importantly, we revealed the underlying mechanism of P. acnes-induced CEP degeneration in the rat CEP cells. Firstly, P. acnes induced the expression of MIF in a concentration-dependent manner. Then, MIF upregulated the expression of MMP-13 and promoted the secretion of IL-6 and IL-1β. Finally, P. acnes may promote MIF expression via NF-κB pathway rather than ERK1/2 pathway.

Conclusion

P. acnes-induced MIF expression via NF-κB pathway may be the underlying mechanism of CEP degeneration.

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

PURPOSE

The role of bacteria, especially Propionibacterium acnes (P. acnes), in human intervertebral disc diseases has raised attention in recent years. However, limited sample size of these studies and diverse bacteria-positive proportion made this topic still controversial. We aimed to review related articles and summarize the bacteria-positive proportion in these studies.

METHODS

We searched the PubMed, Cochrane Library, Embase for related literature from January 2001 to May 2018, and the reference articles were also searched. The random effects or fixed effects meta-analysis was used to pool the overall positive proportion or odds ratio of these studies.

RESULTS

We found 16 relevant articles and 2084 cases of the bacteria culture from surgery. Within the 16 included studies, 12 studies' results supported the infection in the discs. The pooled bacterial infection rate was 25.3%. The pooled P. acnes infection rate was 15.5%. The overall pooled P. acnes proportion in bacteria-positive discs was 56.4%. We also found that the presence of bacteria may contribute to the development of Modic change with the odds ratio as 1.27 (95% CI: 0.44-3.64), but this result is not significant due to heterogeneity, so further study is needed.

CONCLUSION

The existence of bacteria in the intervertebral discs was proved by many studies. However, the variety in sample collecting and culture methods is still obvious and the positive rate also fluctuated within the studies. Standardized and reliable methods should be taken to promote the study in the future. These slides can be retrieved under Electronic Supplementary Material.

The Relationship Between Low-Grade Infection and Degenerative Disk Disease: A Review of Basic Science and Clinical Data

Low back pain resulting from intervertebral disk degeneration is a cause of substantial disability and productivity loss. Over the past few years, growing evidence exists which suggests that low-grade bacterial infection, particularly infection with Cutibacterium acnes, may be associated with degenerative disk disease in the lumbar spine. Positive cultures are obtained in approximately 30% of intervertebral disk specimens removed at the time of surgery. In addition, one randomized trial has shown that antibiotic therapy for low back pain in patients with disk degeneration can slow the progression of degeneration and improve pain and disability levels. Although these results are encouraging, the link between infection and disk degeneration remains controversial. Investigators have attempted to address the limitations of clinical research by using translational methods and animal models. These methods have shown that seeding of the disk with bacteria can lead to increased local inflammation and an in vivo phenotype that is similar to human disk degeneration. This review seeks to provide an overview of the clinical, translational, and animal model data linking infection to disk degeneration. We review mechanisms for disk degeneration in the setting of infection and explore areas for future investigation.

Association between Modic changes and endplate sclerosis: Evidence from a clinical radiology study and a rabbit model

Purpose

To analyse the presence of endplate sclerosis in patients with various types of Modic changes (MCs) and to confirm the results using a rabbit model.

Methods

Participants in the clinical study included 1023 consecutive inpatients with lumbar degenerative disease who attended the Department of Orthopaedics between August 2011 and August 2015. All patients underwent computed tomography (CT) and magnetic resonance imaging of the lumbar spine. In those patients with MCs, endplate sclerosis was evaluated from sagittally reconstructed CT images. In addition to the clinical study, MCs type I, II and III were initiated using a previously developed rabbit model of MCs. Specimens of MCs type I, II and III and normal endplates were harvested, bone mineral density and bone volume/tissue volume of “treated” vertebrae were evaluated using μCT and osteogenic protein expressions of runt-related transcription factor 2 and osteocalcin were assessed using immunohistochemical staining. Measurements were compared between vertebrae with normal endplates and those with different types of MCs.

Results

Of 1023 patients, 214 (20.9%) had MCs in one or more endplates; these changes affected 1044 (10.2%) of 10230 endplates. Type I, II and III MCs were seen in 164 (1.6%), 838(8.2%) and 40 (0.4%) endplates, respectively. Of 1044 endplates with MCs, 274 (26.2%) showed evidence of sclerosis on CT images including: 26/164 endplates (15.8%) with type I MCs, 208/838 (24.8%) with type II and 40/40 (100%) with type III. HU (CT value) ratios for sclerotic and nonsclerotic endplates with MCs were 2.0 ± 0.3 and 1.1 ± 0.1, respectively. In the animal study, the bone mineral density, bone volume/tissue volume and expression of runt-related transcription factor 2 and osteocalcin of endplates with type I and II MCs were higher than those of normal endplates and lower than those of endplates with type III MCs.

Conclusion

Sclerosis can occur in endplates with any type of MCs. However, the clinical and animal study suggests that sclerosis is greatest in endplates showing type III MCs.

The translational potential of this article

The study showed that sclerosis can occur in endplates with MCs type I, II and III. In patients with endplate sclerosis on plain radiographs or CT scans, the endplate can still represent an inflammatory process associated with chronic lower back pain.

Is IL-1β Further Evidence for the Role of Propionibacterium acnes in Degenerative Disc Disease? Lessons From the Study of the Inflammatory Skin Condition Acne Vulgaris

The pathogenesis of degenerative disc disease is a complex and multifactorial process in which genetics, mechanical trauma, altered loading and nutrition present significant etiological factors. Infection of the intervertebral disc with the anaerobic bacterium Propionibacterium acnes is now also emerging as a potentially new etiological factor. This human commensal bacterium is well known for its long association with the inflammatory skin condition acne vulgaris. A key component of inflammatory responses to P. acnes in acne appears to be interleukin (IL)-1β. Similarly, in degenerative disc disease (DDD) there is compelling evidence for the fundamental roles of IL-1β in its pathology. We therefore propose that P. acnes involvement in DDD is biologically very plausible, and that IL-1β is the key inflammatory mechanism driving the host response to P. acnes infection. Since there is a solid theoretical basis for this phenomenon, we further propose that the relationship between P. acnes infection and DDD is causal.

Low virulence bacterial infections in cervical intervertebral discs: a prospective case series

STUDY DESIGN

A prospective cross-sectional case series study.

OBJECTIVE

To investigate the prevalence of low virulence disc infection and its associations with characteristics of patients or discs in the cervical spine.

BACKGROUND

Low virulence bacterial infections could be a possible cause of intervertebral disc degeneration and/or back pain. Controversies are continuing over whether these bacteria, predominantly Propionibacterium acnes (P. acnes), represent infection or contamination. However, the current studies mainly focus on the lumbar spine, with very limited data on the cervical spine.

METHODS

Thirty-two patients (20 men and 12 women) who underwent anterior cervical fusion for degenerative cervical spondylosis or traumatic cervical cord injury were enrolled. Radiological assessments included X-ray, CT, and MRI of the cervical spine. Endplate Modic changes, intervertebral range of motion, and disc herniation type were evaluated. Disc and muscle tissues were collected under strict sterile conditions. Samples were enriched in tryptone soy broth and subcultured under anaerobic conditions, followed by identification of the resulting colonies by the PCR method.

RESULTS

Sixty-six intervertebral discs were excised from thirty-two patients. Positive disc cultures were noted in eight patients (25%) and in nine discs (13.6%). The muscle biopsy (control) cultures were negative in 28 patients and positive in 4 patients (12.5%); three of whom had a negative disc culture. Seven discs (10.6%) were positive for coagulase-negative Staphylococci (CNS) and two discs were positive for P. acnes (3.0%). A younger patient age and the extrusion or sequestration type of disc herniation, which represented a complete annulus fibrous failure, were associated with positive disc culture.

CONCLUSIONS

Our data show that CNS is more prevalent than P. acnes in degenerative cervical discs. The infection route in cervical discs may be predominantly through an annulus fissure. Correlation between these infections and clinical symptoms is uncertain; therefore, their clinical significance needs to be investigated in the future. These slides can be retrieved under Electronic Supplementary Material.

Association between chronic inflammation and latent infection of Propionibacterium acnes in non-pyogenic degenerated intervertebral discs: a pilot study

PURPOSE

Propionibacterium acnes may be considered a new pathogeny for disc degeneration, but its pathological role has remained unclear. This study was designed to determine whether the latent infection of P. acnes was associated with chronic inflammation in degenerated intervertebral discs via quantification of the levels of a series of cytokines and neutrophils.

METHODS

Here, 76 degenerated intervertebral discs were harvested from patients with lower back pain and/or sciatica. Discs with and without P. acnes infection were distinguished and identified using anaerobic culture combined with 16S rDNA PCR and histological examination. Then, cytokines of TNF-α, IL-1β, IL-6, IL-8, MCP-1, MIP-1α, and IP-10, and the numbers of neutrophils were quantified and compared. The severity of disc degeneration and the prevalence of Modic changes were also evaluated between discs with and without P. acnes.

RESULTS

After anaerobic culture and PCR examination, 15 intervertebral discs were placed in the P. acnes-positive group. Another 15 discs were selected from the remaining bacteria-free samples and formed a matched P. acnes-negative group. IL-8, MIP-1α, MCP-1, IP-10, TNF-α, and neutrophils were much higher in P. acnes-positive group than that in the matched P. acnes-negative group. However, only IL-8, MIP-1α, and neutrophils were statistically significant. Furthermore, 7 of 15 P. acnes-positive samples were histologically positive and a subgroup analysis suggested that both histological and PCR-positive samples had the highest concentrations of cytokines of IL-8, MIP-1α, TNF-α, and MCP-1 and the greatest numbers of neutrophils. PCR-positive but histologically negative samples showed the second-greatest, and matched P. acnes-negative samples showed the fewest. However, the difference was only statistically significant between samples found positive under both histology and PCR and samples found negative for P. acnes. Finally, P. acnes-positive group had significantly lower height of intervertebral discs and there was a trend with higher proportion of Modic changes in P. acnes-positive group, but without statistical results.

CONCLUSIONS

Latent P. acnes infection was associated with chronic inflammation in degenerated intervertebral discs, especially in the samples with visible bacteria in histology, which manifested as increased numbers of cytokines and neutrophils. Discs with P. acnes infection had much severer disc degeneration and P. acnes-associated chronic inflammation may be the reason.