Modic type 1 changes (MC1) are painful vertebral bone marrow lesions frequently found in patients suffering from chronic low-back pain. Marrow fibrosis is a hallmark of MC1. Bone marrow stromal cells (BMSCs) are key players in other fibrotic bone marrow pathologies, yet their role in MC1 is unknown. The present study aimed to characterise MC1 BMSCs and hypothesised a pro-fibrotic role of BMSCs in MC1. BMSCs were isolated from patients undergoing lumbar spinal fusion from MC1 and adjacent control vertebrae. Frequency of colony-forming unit fibroblast (CFU-F), expression of stem cell surface markers, differentiation capacity, transcriptome, matrix adhesion, cell contractility as well as expression of pro-collagen type I alpha 1, α-smooth muscle actin, integrins and focal adhesion kinase (FAK) were compared. More CFU-F and increased expression of C-X-C-motif-chemokine 12 were found in MC1 BMSCs, possibly indicating overrepresentation of a perisinusoidal BMSC population. RNA sequencing analysis showed enrichment in extracellular matrix proteins and fibrosis-related signalling genes. Increases in pro-collagen type I alpha 1 expression, cell adhesion, cell contractility and phosphorylation of FAK provided further evidence for their pro-fibrotic phenotype. Moreover, a leptin receptor high expressing (LEPRhigh) BMSC population was identified that differentiated under transforming growth factor beta 1 stimulation into myofibroblasts in MC1 but not in control BMSCs. In conclusion, pro-fibrotic changes in MC1 BMSCs and a LEPRhigh MC1 BMSC subpopulation susceptible to myofibroblast differentiation were found. Fibrosis is a hallmark of MC1 and a potential therapeutic target. A causal link between the pro-fibrotic phenotype and clinical characteristics needs to be demonstrated.

Purpose The aim of this work is to evaluate the effectiveness of training with the low-fidelity ArthroBox ® regarding performance of different basic arthroscopy tasks using a validated high-fidelity virtual reality simulator of the knee. Methods Nineteen volunteers (14 females and 5 males) without any previous experience in arthroscopy were randomly assigned either to the ArthroBox ® training group (n =10) or the non-training group (n =9). The training group underwent a supervised ArthroBox ® training consisting of a daily 60-min session for three consecutive days. Both groups completed the basic and the final assessment using a validated virtual reality-based passive haptic knee arthroscopy simulator (ArthroS, VirtaMed™). The following three factors were measured in different exercises (explained in "Materials and methods"): amount of time to finish the task, length of camera and scope path within the joint. Furthermore, the volunteers' demographics (age, sex, dexterity, video game experience, sport activities and profession) was assessed but showed no differences between the groups. Results There were no significant differences between the training and non-training group regarding the above-mentioned demographic factors. However, the training group showed significant improvement from baseline to follow-up in most activities (e.g. task performance time in seconds, intra-articular camera and grasp distance in centimetres; see Table 1) in comparison to the non-training group. Conclusions The results from this study demonstrate that training for three consecutive days using a portable and versatile low-fidelity simulator significantly improves arthroscopy performance when using a validated high-fidelity virtual knee simulator. Arthroscopic triangulation training outside the operating theatre with a portable, low-cost simulator has proven to be a valuable educational tool to improve the arthroscopic skills of trainee surgeons. Level of evidence Diagnostic study, Level II.

Background:Modic type 1 changes (MC1) are vertebral bone marrow lesions associated with non-specific low back pain (LBP). The pathophysiology of MC1 includes inflammation, fibrosis, and high bone turnover. Bone marrow stromal cells (BMSCs) are key regulators of these processes: BMSCs contribute to inflammation by regulating myelopoiesis/osteoclastogenesis; BMSCs can differentiate into osteoblasts contributing to high bone turnover, and BMSCs can differentiate into pro-fibrotic myofibroblasts.Objectives:To identify dysregulated biological processes in MC1 BMSCs contributing to the pathobiology of MC1.Methods:Bone marrow aspirates were obtained from LBP patients with MC1 undergoing lumbar spinal fusion. Aspirates were taken prior to screw insertion. From each patient, a MC1 and a healthy control (HC) aspirate from the adjacent vertebral body was collected. BMSCs were isolated by plastic adherence and expanded. RNA from BMSCs passage 3 was sequenced (n=3 + 3) (Illumina Novaseq) and gene ontology of significantly dysregulated genes (p-value < 0.05) was analyzed. Specificity and rate of BMSC matrix adhesion were quantified: BMSCs (n=8 + 8) were seeded on fibronectin-coated, collagen-I-coated, and non-coated plastic dishes. BMSC adhesion was evaluated from 15min to 30min (Δ 30min - 15min). Percentage of adherent cells of MC1 and HC BMSC was compared with paired t-test. In order to identify integrins responsible for dysregulated cell-matrix adhesion, gene expression of 15 relevant integrins was measured by quantitative real-time PCR (qPCR). Normalized expressions were compared between MC1 and HC BMSC with paired t-test. Integrin β1 protein level was semi quantitatively analyzed by Western Blot (n = 5 + 5) and normalized to β-Actin expression.Results:By RNA sequencing, 154 genes were differentially expressed between MC1 and HC BMSCs (p-value ≤ 0.01; log2-ratio ≥ 0.5). Gene ontology enrichment analysis revealed an overrepresentation of the biological process “cell-matrix adhesion” among all significantly regulated genes (p-value < 9.3e-13). A change in cell adhesion was corroborated with adhesion assay. Binding (Δ 30min - 15min) to collagen I (MC1 + 16%, HC +10%, p-value = 0.10), fibronectin (MC1 + 17%, HC +6%, p-value = 0.03), and non-coated surface (MC1 + 46%, HC +35%, p-value = 0.05) was increased in MC1 (Figure 1). Integrin gene expression analysis revealed significant upregulation of integrin beta-1 gene (ITGB1) in MC1 vs. HC (fold change = 1.24, p-value = 0.047), whereas there was no significant difference between the other integrins tested. On protein level, integrin β1 was upregulated in MC1 in four out of five patients (Figure 2).Figure 1.Adhesion assay.Figure 2.Western Blot analysis.Conclusion:Adhesion of BMSCs to matrix and integrin β1 expression are increased in MC1. Integrin β1 is essential for cell-matrix adhesion and an important contributor to the initiation and progression of tissue fibrosis, a hallmark of MC1. Therefore, BMSCs and integrin β1 might be relevant novel targets for the treatment of MC1.Disclosure of Interests: :Irina Heggli: None declared, Susanne Epprecht: None declared, Tamara Mengis: None declared, Astrid Juengel: None declared, Michael Betz: None declared, Jose Spirig: None declared, Florian Wanivenhaus: None declared, Florian Brunner: None declared, Mazda Farshad: None declared, Oliver Distler Grant/research support from: Grants/Research support from Actelion, Bayer, Boehringer Ingelheim, Competitive Drug Development International Ltd. and Mitsubishi Tanabe; he also holds the issued Patent on mir-29 for the treatment of systemic sclerosis (US8247389, EP2331143)., Consultant of: Consultancy fees from Actelion, Acceleron Pharma, AnaMar, Bayer, Baecon Discovery, Blade Therapeutics, Boehringer, CSL Behring, Catenion, ChemomAb, Curzion Pharmaceuticals, Ergonex, Galapagos NV, GSK, Glenmark Pharmaceuticals, Inventiva, Italfarmaco, iQvia, medac, Medscape, Mitsubishi Tanabe Pharma, MSD, Roche, Sanofi and UCB, Speakers bureau: Speaker fees from Actelion, Bayer, Boehringer Ingelheim, Medscape, Pfizer and Roche, Stefan Dudli: None declared