Intervertebral disc cell chondroptosis elicits neutrophil response in Staphylococcus aureus spondylodiscitis

Causal relationship between molecular markers of biological aging and orthopedic diseases: A two-sample bidirectional Mendelian randomization study

BACKGROUND

Studies indicate an association between biological aging and orthopedic diseases, but the causality remains unclear.

AIMS

This study aims to investigate the bidirectional causal relationship between molecular markers of biological aging age and orthopedic conditions.

METHODS

A two-sample Mendelian randomization (MR) analysis based on a genome-wide association study (GWAS) was conducted to explore these causal relationships. Analysis methods included inverse variance weighted (IVW), MR-Egger, weighted median, and weighted mode. Sensitivity analyses involved Cochran's Q, MR-Egger, leave-one-out, and MR pleiotropy residual sum and outlier (MR-PRESSO) tests.

RESULTS

The forward MR analysis identified several causal relationships: granulocyte proportions influenced intervertebral disc degeneration (IVDD) (OR 0.2316, P = 0.0101) and low back pain (LBP) (OR 0.2624, P = 0.007); telomere length (TL) affected cervical spondylosis (C/S) (OR 0.8759, P = 0.0167) and IVDD (OR 0.9184, P = 0.023); fibroblast growth factor-23 (FGF-23) impacted frozen shoulder (FS) (OR 1.2424, P = 0.0316); and HannumAge influenced C/S (OR 0.9518, P = 0.0233). The reverse MR analysis found that FS influenced TL (OR 0.9582, P = 0.0002) and α-Klotho (OR 0.7592, P = 0.0256), while sciatica affected TL (OR 0.9344, P = 0.0055) and C/S impacted PhenoAge (OR 1.6583, P = 0.0131) after outlier exclusion. Cochran's Q indicated heterogeneity in certain analyses, and MR-Egger showed no horizontal pleiotropy in significant causal associations.

CONCLUSIONS

This study suggests a potential causal associations between molecular markers of biological aging and orthopedic diseases, suggesting avenues for future research into the underlying mechanisms.

A sonosensitive diphenylalanine-based broad-spectrum antimicrobial peptide

The antimicrobial effect of antimicrobial peptides is typically slow; they can be rapidly biodegraded and often have non-selective toxicity and elaborate sequences. Here we report a short peptide that is activated by ultrasound, that shows high broad-spectrum antibacterial efficiency (>99%) against clinically isolated methicillin-resistant bacteria (specifically, Staphylococcus aureus, Escherichia coli, Staphylococcus epidermidis, Enterobacter cancerogenus and Pseudomonas aeruginosa) with 15 min of ultrasound irradiation, and that has negligible toxicity and low self-antibacterial activity. We selected the peptide, FFRKSKEK (a segment from the human host-defence LL-37 peptide), from a library of peptides with piezoelectric diphenylalanine (FF) sequences, low toxicity, hydrophobicity and net positive charge. We show via all-atom molecular dynamics simulations that ultrasound amplifies the membrane-penetrating ability of peptides with FF sequences and that its piezoelectric polarization generates reactive-oxygen species and disturbs bacterial electron-transport chains. In a goat model of hard-to-treat intervertebral infection, the sonosensitive peptide led to better outcomes than vancomycin. Antimicrobial peptides activated by ultrasound may offer a clinically relevant strategy for combating antibiotic-resistant infections.

Efficacy of Naringenin against aging and degeneration of nucleus pulposus cells through IGFBP3 inhibition

Naringenin (NAR), a natural flavonoid, exerts anti-inflammatory and antioxidant pharmacology. However, the pharmacological mechanisms through which NAR prevents and treats intervertebral disc degeneration (IDD) remain unclear. We utilized bioinformatics, machine learning, and network pharmacology to identify shared targets among NAR, senescence, and IDD. Subsequently, molecular docking was conducted to evaluate NAR's binding affinity to common target. Additionally, we used IL-1β to induce senescence and degeneration in nucleus pulposus cells (NPCs) and conducted a series of cellular assays, including immunoblotting, immunofluorescence, β-galactosidase staining, cell proliferation, cell cycle analysis, and measurement of reactive oxygen species levels, to investigate NAR's impact on IL-1β-induced senescence and degeneration of NPCs. Our study revealed that Insulin-like growth factor binding protein 3 (IGFBP3) was the only common target. IGFBP3 exhibited significant differences between the IDD and healthy groups and proved to be an effective diagnostic marker for IDD. Molecular docking confirmed the binding between NAR and IGFBP3. In vitro experiments, we observed that Igfbp3 expression increased in the senescence and degeneration groups. Igfbp3 knockdown and NAR attenuated IL-1β-induced senescence and degenerative phenotypes in NPCs. In contrast, the effect of NAR was attenuated by recombinant IGFBP3 protein. In conclusion, our findings suggest that NAR plays a preventive and therapeutic role in IDD, likely achieved through the inhibition of Igfbp3 expression.

TRPV4 differentially controls inflammatory cytokine networks during static and dynamic compression of the intervertebral disc

Background

The ion channel transient receptor potential vanilloid 4 (TRPV4) critically transduces mechanical forces in the IVD, and its inhibition can prevent IVD degeneration due to static overloading. However, it remains unknown whether different modes of loading signals through TRPV4 to regulate the expression of inflammatory cytokines. We hypothesized that TRPV4 signaling is essential during static and dynamic loading to mediate homeostasis and mechanotransduction.

Methods

Mouse functional spine units were isolated and either cyclically compressed for 5 days (1 Hz, 1 h, 10% strain) or statically compressed (24 h, 0.2 MPa). Conditioned media were monitored at 6 h, 24 h, 2 days, and 5 days, with and without TRPV4 inhibition. Effects of TRPV4 activation was also evaluated without loading. The media was analyzed for a panel of 44 cytokines using a microbead array and then a correlative network was constructed to explore the regulatory relationships during loading and TRPV4 inhibition. After the loading regimen, the IVDs were evaluated histologically for degeneration.

Results

Activation of TRPV4 led to an increase interleukin-6 (IL-6) family of cytokines (IL-6, IL-11, IL-16, and leukemia inhibitory factor [LIF]) and decreased the T-cell (CCL3, CCL4, CCL17, CCL20, CCL22, and CXCL10) and monocyte (CCL2 and CCL12) recruiting chemokines by the IVD. Dynamic and static loading each provoked unique chemokine correlation networks. The inhibition of TRPV4 during dynamic loading dysregulated the relationship between LIF and other cytokines, while the inhibition of TRPV4 during static loading disrupted the connectivity of IL-16 and VEGFA.

Conclusions

We demonstrated that TRPV4 critically mediates the cytokine production following dynamic and static loading. The activation of TRPV4 upregulated a diverse set of cytokines that may suppress the chemotaxis of T-cells and monocytes, implicating the role of TRPV4 in maintaining the immune privilege of healthy IVD.

MAPK8 and CAPN1 as potential biomarkers of intervertebral disc degeneration overlapping immune infiltration, autophagy, and ceRNA

Background

Intervertebral disc degeneration (IDD) is one of the most common health problems in the elderly and a major causative factor in low back pain (LBP). An increasing number of studies have shown that IDD is closely associated with autophagy and immune dysregulation. Therefore, the aim of this study was to identify autophagy-related biomarkers and gene regulatory networks in IDD and potential therapeutic targets.

Methods

We obtained the gene expression profiles of IDD by downloading the datasets GSE176205 and GSE167931 from the Gene Expression Omnibus (GEO) public database. Subsequently, differentially expressed genes (DEGs) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene ontology (GO), and gene set enrichment analysis (GSEA) were performed to explore the biological functions of DEGs. Differentially expressed autophagy-related genes (DE-ARGs) were then crossed with the autophagy gene database. The hub genes were screened using the DE-ARGs protein-protein interaction (PPI) network. The correlation between the hub genes and immune infiltration and the construction of the gene regulatory network of the hub genes were confirmed. Finally, quantitative PCR (qPCR) was used to validate the correlation of hub genes in a rat IDD model.

Results

We obtained 636 DEGs enriched in the autophagy pathway. Our analysis revealed 30 DE-ARGs, of which six hub genes (MAPK8, CTSB, PRKCD, SNCA, CAPN1, and EGFR) were identified using the MCODE plugin. Immune cell infiltration analysis revealed that there was an increased proportion of CD8+ T cells and M0 macrophages in IDD, whereas CD4+ memory T cells, neutrophils, resting dendritic cells, follicular helper T cells, and monocytes were much less abundant. Subsequently, the competitive endogenous RNA (ceRNA) network was constructed using 15 long non-coding RNAs (lncRNAs) and 21 microRNAs (miRNAs). In quantitative PCR (qPCR) validation, two hub genes, MAPK8 and CAPN1, were shown to be consistent with the bioinformatic analysis results.

Conclusion

Our study identified MAPK8 and CAPN1 as key biomarkers of IDD. These key hub genes may be potential therapeutic targets for IDD.

Post-COVID-19 Spondylodiscitis: A Case Study and Review of the Literature

COVID-19 is currently a major health problem, leading to respiratory, cardiovascular and neurological complications, with additional morbidity and mortality. Spinal infections are rare, representing around 1% of all bone infections and comprising less than 2 per 10,000 of all hospitalizations in tertiary care centers. Spondylodiscitis is a complex disease, with challenging diagnosis and management. We report the case of a 45-year-old man, non-smoker hospitalized for severe COVID-19 disease with respiratory failure. Post-COVID-19, in the 8th week after discharge, he was diagnosed by magnetic resonance imaging with spondylodiscitis, but etiology was not confirmed by microbiological investigations. Antibiotics were used, considering the identification of MRSA from cultures of pleural fluid and nasal swab, but surgical intervention was not provided. Clinic, biologic and imagistic were improved, but rehabilitation and long term follow up are necessary. We concluded that spondylodiscitis with spinal abscess is a rare but severe complication post-COVID-19 disease, due to dysbalanced immune response related to the respiratory viral infection, endothelial lesions, hypercoagulation and bacterial superinfection.