Aims. The presence of facet tropism has been correlated with an elevated susceptibility to lumbar disc pathology. Our objective was to evaluate the impact of facet tropism on chronic lumbosacral discogenic pain through the analysis of clinical data and finite element modelling (FEM). Methods. Retrospective analysis was conducted on clinical data, with a specific focus on the spinal units displaying facet tropism, utilizing FEM analysis for motion simulation. We studied 318 intervertebral levels in 156 patients who had undergone provocation discography. Significant predictors of clinical findings were identified by univariate and multivariate analyses. Loading conditions were applied in FEM simulations to mimic biomechanical effects on intervertebral discs, focusing on maximal displacement and intradiscal pressures, gauged through alterations in disc morphology and physical stress. Results. A total of 144 discs were categorized as ‘positive’ and 174 discs as ‘negative’ by the results of provocation discography. The presence of defined facet tropism (OR 3.451, 95% CI 1.944 to 6.126) and higher Adams classification (OR 2.172, 95% CI 1.523 to 3.097) were important predictive parameters for discography-‘positive’ discs. FEM simulations showcased uneven stress distribution and significant disc displacement in tropism-affected discs, where loading exacerbated stress on facets with greater angles. During varied positions, notably increased stress and displacement were observed in discs with tropism compared to those with normal facet structure. Conclusion. Our findings indicate that facet tropism can contribute to disc herniation and changes in intradiscal pressure, potentially exacerbating disc degeneration due to altered force distribution and increased mechanical stress. Cite this article: Bone Joint Res 2024;13(9):452–461

A key cause of low back pain is the degeneration of the intervertebral disc (IVD). Causality between infection of the IVD and its degenerative process gained great interest over the last decade. Granville Smith et al. (2021) identified 36 articles from 34 research studies investigating bacteria in human IVDs. Bacteria was identified in 27 studies, whereas 9 attributed bacterial presence to contamination. Cutibacterium acnes was the most abundant, followed by coagulase-negative staphylococcus. However, whether bacteria identified were present in vivo or represent perioperative contamination remains unclear. This study investigated whether bacteria are present in IVDs and what potential effects they may have on native disc cells. Immunohistochemical staining for Gram positive bacteria was performed on human IVD tissue to identify presence and characterise bacterial species. Nucleus pulposus (NP) cells in monolayer and 3D alginate were stimulated with LPS and Peptidoglycan (0.1-50 µg/ml) for 48hrs. Following stimulation qPCR for factors associated with disc degeneration including matrix genes, matrix degrading enzymes, cytokines, neurotrophic factors and angiogenic factors and conditioned media collected for ELISA and luminex analysis. Gram positive bacteria was detected within human IVD tissue. Internalisation of bacteria by NP cells influenced the cell and nuclei morphology. Preliminary results of exposure of NP cells to bacterial components indicate that LPS as well as Peptidoglycan increase IL-8 and ADAMTS-4 gene expression following 48 hours of stimulation with a dose response seen for IL-8 induction by peptidoglycan compared to the control group. Underlining these results, IL-8 protein release was increased for treated groups compared to non-treated control. Further analysis is underway investigating other output measures and additional biological repeats. This study has demonstrated bacteria are present within IVD cells within IVD tissue removed from degenerate IVD and is determining the potential influence of these on disc degeneration

Using deep learning and image processing technology, a standardized automatic quantitative analysis systerm of lumbar disc degeneration based on T2MRI is proposed to help doctors evaluate the prognosis of intervertebral disc (IVD) degeneration. A semantic segmentation network BianqueNet with self-attention mechanism skip connection module and deep feature extraction module is proposed to achieve high-precision segmentation of intervertebral disc related areas. A quantitative method is proposed to calculate the signal intensity difference (SI) in IVD, average disc height (DH), disc height index (DHI), and disc height-to-diameter ratio (DHR). According to the correlation analysis results of the degeneration characteristic parameters of IVDs, 1051 MRI images from four hospitals were collected to establish the quantitative ranges for these IVD parameters in larger population around China. The average dice coefficients of the proposed segmentation network for vertebral bodies and intervertebral discs are 97.04% and 94.76%, respectively. The designed parameters of intervertebral disc degeneration have a significant negative correlation with the Modified Pfirrmann Grade. This procedure is suitable for different MRI centers and different resolution of lumbar spine T2MRI (ICC=.874~.958). Among them, the standard of intervertebral disc signal intensity degeneration has excellent reliability according to the modified Pfirrmann Grade (macroF1=90.63%~92.02%). we developed a fully automated deep learning-based lumbar spine segmentation network, which demonstrated strong versatility and high reliability to assist residents on IVD degeneration grading by means of IVD degeneration quantitation

Stem cell therapy for the intervertebral disc (IVD) is highly debated but holds great promises. From previous studies, it is known that notochordal cells are highly regenerative and may stimulate other differentiated cells to produce more matrix. Lately, a particular tissue-specific progenitor cell population has been identified in the centre of the intervertebral disc (IVD. The current hope is that these nucleus pulposus progenitor cells (NPPC) could play a particular role in IVD regeneration. Current evidence confirms the presence of these cells in murine, canine, bovine and in the human fetal/surgical samples. Noteworthy, one of the main markers to identify these cells, i.e., Tie2, is a typical marker for endothelial cells. Thus, it is not very clear what their origin and their role might be in the context of developmental biology. In human surgical specimens, their presence is, even more, obscured depending on the donor's age and the condition of the IVD and other yet unknown factors. Here, I revisit the recent literature on regenerative cells identified for the IVD in the past decades. Current evidence how these NPPC can be isolated and detected in various species and tissues will be recapitulated. Future directions will be provided on how these progenitor cells could be used for regenerative medicine and tissue engineering

Monomeric C reactive protein (mCRP) presents important proinflammatory effects in endothelial cells, leukocytes, or chondrocytes. However, CRP in its pentameric form exhibits weak anti-inflammatory activity. It is used as a biomarker to follow severity and progression in infectious or inflammatory diseases, such as intervertebral disc degeneration (IVDD). This work assesses for the first time the mCRP effects in human intervertebral disc cells, trying to verify the pathophysiological relevance and mechanism of action of mCRP in the etiology and progression of IVD degeneration. We demonstrated that mCRP induces the expression of multiple proinflammatory and catabolic factors, like nitric oxide synthase 2 (NOS2), cyclooxygenase 2 (COX2), matrix metalloproteinase 13 (MMP13), vascular cell adhesion molecule 1 (VCAM1), interleukin (IL)-6, IL-8, and lipocalin 2 (LCN2), in human annulus fibrosus (AF) and nucleus pulposus (NP) cells. We also showed that nuclear factor-κβ (NF-κβ), extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphoinositide 3-kinase (PI3K) are at play in the intracellular signaling of mCRP. Our results indicate that the effect of mCRP is persistent and sustained, regardless of the proinflammatory environment, as it was similar in healthy and degenerative human primary AF cells. This is the first article that demonstrates the localization of mCRP in intravertebral disc cells of the AF and NP and that provides evidence for the functional activity of mCRP in healthy and degenerative human AF and NP disc cells

Aims. CRP is an acute-phase protein that is used as a biomarker to follow severity and progression in infectious and inflammatory diseases. Its pathophysiological mechanisms of action are still poorly defined. CRP in its pentameric form exhibits weak anti-inflammatory activity. The monomeric isoform (mCRP) exerts potent proinflammatory properties in chondrocytes, endothelial cells, and leucocytes. No data exist regarding mCRP effects in human intervertebral disc (IVD) cells. This work aimed to verify the pathophysiological relevance of mCRP in the aetiology and/or progression of IVD degeneration. Methods. We investigated the effects of mCRP and the signalling pathways that are involved in cultured human primary annulus fibrosus (AF) cells and in the human nucleus pulposus (NP) immortalized cell line HNPSV-1. We determined messenger RNA (mRNA) and protein levels of relevant factors involved in inflammatory responses, by quantitative real-time polymerase chain reaction (RT-qPCR) and western blot. We also studied the presence of mCRP in human AF and NP tissues by immunohistochemistry. Results. We demonstrated that mCRP increases nitric oxide synthase 2 (NOS2), cyclooxygenase 2 (COX2), matrix metalloproteinase 13 (MMP13), vascular cell adhesion molecule 1 (VCAM1), interleukin (IL)-6, IL-8, and Lipocalin 2 (LCN2) expression in human AF and NP cells. We also showed that nuclear factor-κβ (NF-κβ), extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphoinositide 3-kinase (PI3K) are at play in the intracellular signalling of mCRP. Finally, we demonstrated the presence of mCRP in human AF and NP tissues. Conclusion. Our results indicate, for the first time, that mCRP can be localized in IVD tissues, where it triggers a proinflammatory and catabolic state in degenerative and healthy IVD cells, and that NF-κβ signalling may be implicated in the mediation of this mCRP-induced state. Cite this article: Bone Joint Res 2023;12(3):189–198

Introduction. Multiple studies have identified Cutibacterium acnes (C.acnes) and other microbes in intervertebral disc tissue using 16S DNA Sequencing and microbial cultures. However, it remains unclear whether these bacteria are native to the discs or result from perioperative contamination. Our study aimed to detect Gram-positive bacteria in non-herniated human disc samples and explore correlations with Toll-like receptors (TLR) 2, TLR4, NLRP3, and Gasdermin D. Methods. Immunohistochemical staining was conducted on 75 human IVD samples for Gram-positive bacteria, S. aureus, C.acnes, TLR2, TLR4, NLRP3, and Gasdermin D. Cell detection and classification were performed using QuPath. NP cells were treated with Lipopolysaccharide (LPS) and Peptidoglycan (PGN) in monolayer and alginate beads for up to 72 hours, followed by secretome analysis using Luminex. Statistical analysis included Kruskal-Wallis, Dunn's multiple comparison test, and Pearson correlation. Results. Immunohistochemical staining revealed Gram-positive bacteria exclusively within cells, with C. acnes positivity ranging from 5–99% and correlating with patient age (r=0.41, p= 0.007). TLR2 positivity ranged from 5–99% and TLR4 from 3–72%, showing a strong correlation (r= 0.62, p= 1.5e-006). Females with mid-degenerative grades exhibited significantly decreased TLR2 expression compared to those without degeneration signs. Treatment with LPS and PGN increased catabolic cyto- and chemokines associated with IVD degeneration. Conclusion. In conclusion, this study confirms Gram-positive bacteria presence in non-herniated human disc samples and highlights their role in triggering a catabolic response in disc cells. No conflicts of interest.  . Sources of funding. This project is part of the Disc4All Training network to advance integrated computational simulations in translational medicine, applies to intervertebral disc degeneration and funded by Horizon 2020 (H2020-MSCA-ITN-ETN-2020 GA: 955735)

Intervertebral disc degeneration can lead to physical disability and significant pain, while the present therapeutics still fail to biochemically and biomechanically restore the tissue. Stem cell-based therapy in treating intervertebral disc (IVD) degeneration is promising while transplanting cells alone might not be adequate for effective regeneration. Recently, gene modification and 3D-printing strategies represent promising strategies to enhanced therapeutic efficacy of MSC therapy. In this regard, we hypothesized that the combination of thermosensitive chitosan hydrogel and adipose derived stem cells (ADSCs) engineered with modRNA encoding Interleukin − 4 (IL-4) can inhibit inflammation and promote the regeneration of the degenerative IVD. Rat ADSCs were acquired from adipose tissue and transfected with modRNAs. First, the kinetics and efficacy of modRNA-mediated gene transfer in mouse ADSCs were analyzed in vitro. Next, we applied an indirect co-culture system to analyze the pro-anabolic potential of IL-4 modRNA engineered ADSCs (named as IL-4-ADSCs) on nucleus pulposus cells. ModRNA transfected mouse ADSCs with high efficiency and the IL-4 modRNA-transfected ADSCs facilitated burst-like production of bio-functional IL-4 protein. In vitro, IL-4-ADSCs induced increased anabolic markers expression of nucleus pulposus cells in inflammation environment compared to untreated ADSCs. These findings collectively supported the therapeutic potential of the combination of thermosensitive chitosan hydrogel and IL-4-ADSCs for intervertebral disc degeneration management. Histological and in vivo validation are now being conducted

Aims. This study aimed, through bioinformatics analysis and in vitro experiment validation, to identify the key extracellular proteins of intervertebral disc degeneration (IDD). Methods. The gene expression profile of GSE23130 was downloaded from the Gene Expression Omnibus (GEO) database. Extracellular protein-differentially expressed genes (EP-DEGs) were screened by protein annotation databases, and we used Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) to analyze the functions and pathways of EP-DEGs. STRING and Cytoscape were used to construct protein-protein interaction (PPI) networks and identify hub EP-DEGs. NetworkAnalyst was used to analyze transcription factors (TFs) and microRNAs (miRNAs) that regulate hub EP-DEGs. A search of the Drug Signatures Database (DSigDB) for hub EP-DEGs revealed multiple drug molecules and drug-target interactions. Results. A total of 56 EP-DEGs were identified in the differential expression analysis. EP-DEGs were enriched in the extracellular structure organization, ageing, collagen-activated signalling pathway, PI3K-Akt signalling pathway, and AGE-RAGE signalling pathway. PPI network analysis showed that the top ten hub EP-DEGs are closely related to IDD. Correlation analysis also demonstrated a significant correlation between the ten hub EP-DEGs (p＜0.05), which were selected to construct TF–gene interaction and TF–miRNA coregulatory networks. In addition, ten candidate drugs were screened for the treatment of IDD. Conclusion. The findings clarify the roles of extracellular proteins in IDD and highlight their potential as promising novel therapeutic targets. Cite this article: Bone Joint Res 2023;12(9):522–535

Degeneration of the intervertebral disc (IVD), and subsequent low back pain, is an almost inevitable cause of disability. The underlying mechanisms are complex and current therapeutic strategies mainly focus on symptomatic relief rather than on the intrinsic regeneration of the IVD. This talk will provide an overview of special anatomical features and the composition of the IVD as well as its cellular microenvironment. Selected promising conceptional regenerative approaches will be discussed

Intervertebral disc degeneration is a common cause of low-back pain, the musculoskeletal disorder with the largest impact world-wide. The complex disease is however not yet well understood, and no treatment is available. This is somewhat in contrast with osteoarthritis, a subject of more extensive research. Intervertebral disc degeneration may though be a type of osteoarthritis, as other vertebrates have a diarthrodial joint instead of an intervertebral disc. We describe the parallel in view of the anatomy, composition and degeneration of the intervertebral disc and articular joint. Not only different embryonic origin and anatomy suggest significant differences between the intervertebral disc and the synovial joint, but their biomechanical properties also partly differ, as articulation is one of the key properties of a synovial joint and does not occur in the intervertebral disc. However, both tissues provide flexibility and are able to endure compressive loads, and both cell behavior and extracellular matrix appear much the same, mainly existing of chondrocytes, proteoglycans and collagen type II, suggesting that the environment of the cell is more important to its behavior than embryonic origin. Moreover, great similarities are found in the inflammatory cytokines, which are mainly IL-1β and TNF-α, and matrix-degrading factors (i.e. MMPs and ADAMTSs) involved in the cascade of degeneration, resulting in overlapping clinical and radiological features such as loss of joint space, subchondral sclerosis, and the formation of osteophytes, causing pain and morning stiffness. Therefore, we state that disc degeneration can result in the osteoarthritic intervertebral disc. This point of view may enhance the synergy between both fields of research, and potentially provide new regenerative strategies for intervertebral disc degeneration

The use of mesenchymal stem cell (MSCs) for intervertebral disc (IVD) regeneration has been extensively explored in the last two decades. MSCs are potent cell types that can be easily and safely harvested due to their abundancy and availability. Moreover, they are characterized by the capacity to differentiate towards IVD cells as well as release growth factors to support resident cell metabolism and recruit local progenitor cells to induce endogenous repair of degenerated IVDs. This talk will outline the characteristics of the main MSC sources and their effect towards IVD regeneration based on available preclinical and clinical evidence. In addition, innovative aspects of MSC-derived cell-free therapies will also be discussed

Low back pain (LBP) is the main cause of disability worldwide and is primarily triggered by intervertebral disc degeneration (IDD). Although several treatment options exist, no therapeutic tool has demonstrated to halt the progressive course of IDD. Therefore, several clinical trials are being conducted to investigate different strategies to regenerate the intervertebral disc, with numerous studies not reaching completion nor being published. The aim of this study was to analyze the publication status of clinical trials on novel regenerative treatments for IDD by funding source and identify critical obstacles preventing their conclusion. Prospective clinical trials investigating regenerative treatments for IDD and registered on . ClinicalTrials.gov. were included. Primary outcomes were publication status and investigational treatment funding. Fisher's exact test was utilized to test the association for categorical variables between groups. 25 clinical trials were identified. Among these, only 6 (24%) have been published. The most common source of funding was university (52%), followed by industry (36%) and private companies (12%). Investigational treatments included autologous (56%) or allogeneic (12%) products alone or in combination with a carrier or delivery system (32%). The latter were more likely utilized in industry or privately funded studies (Fig. 1, p=0.0112). No significant difference was found in terms of funding regarding the publication status of included trials (Table 1, p=0.9104). Most clinical trials investigating regenerative approaches for the treatment of IDD were never completed nor published. This is likely due to multiple factors, including difficult enrollment, high dropout rate, and publication bias. 3. More accurate design and technical support from stakeholders and clinical research organization (CROs) may likely increase the quality of future clinical trials in the field. For any figures or tables, please contact the authors directly

Despite promising results in attempting intervertebral disc regeneration, intradiscal cell transplantation is affected by several drawbacks, including poor viability in the harsh disc environment, low cost-effectiveness, and immunogenic/tumorigenic concerns. Recently, the development of cell-free approaches is gaining increasing interest in the field, with a particular regard towards extracellular vesicles (EVs). Nucleus pulposus cell (NPC) progenitors characterized by Tie2 expression have shown a higher chondrogenic differentiation potential compared to MSCs. The aim of this study was to investigate the putative regenerative effects of EVs isolated from Tie2-overexpressing NPC progenitors on degenerative NPCs. NPCs were isolated from young donors and underwent an optimized culture protocol to maximize Tie2 expression (NPCs. Tie2+. ) or a standard protocol (NPCs. STD. ). Following EV characterization, NPC isolated from patients affected by intervertebral disc degeneration (IDD) were treated with either NPCs. Tie2+. -EVs or NPCs. STD. -EVs. Cell proliferation and viability were assessed with the CCK-8 assay. Cell apoptosis and necrosis were evaluated with the Annexin V/PI assay. Cell senescence was investigated with b-galactosidase staining. EV uptake was assessed with PKH26 staining of EVs under confocal microscopy. Treatment with EVs isolated from young NPC donors significantly increased degenerative NPC viability, especially in samples treated with NPCs. Tie2+. -EVs. Likewise, NPCs. Tie2+. -EVs significantly reduced cell senescence and did not show to exert necrotic nor apoptotic effects on recipient cells. Furthermore, EV uptake was successfully observed in all treated cells. NPCs. Tie2+. -EVs demonstrated to significantly enhance degenerative NPC viability, senescence and apoptosis. The use of committed progenitors naturally residing the in the nucleus pulposus may optimize EV regenerative properties and constitute the basis for a new therapy for IDD

Abstract. Objectives. Develop a methodology to assess the long term mechanical behavior of intervertebral discs by utilizing novel sequential state testing. Methods. Bovine functional spinal units were sequentially mechanically tested in (1) native (n=8), (2) degenerated (n=4), and (3) treated states (n=4). At stage (2), artificial degeneration was created using rapid enzymatic degeneration, followed by a 24 hour hold period under static load at 42°C. At stage (3), nucleus augmentation treatments were injected with a hydrogel or a ‘sham’ (water, chondroitin sulfate) injection. The mechanical protocol employed applied a static load hold period followed by cyclic compressive loading between ∼350 and 750 N at 1 Hz. 1000 cycles were applied at each stage, and the final test on each specimen was extended up to 20000 cycles. To verify if test time can be reduced, functions were fitted using stiffness data up to 100, 1000, 2500, 5000, 10000 and 20000 cycles. Linear regression for the native specimens comparing the stiffness at various cycles to the stiffness at 20000 cycles was completed. Results. Independent of the disc state, as the number of cycles increased, the hysteresis decreased and the stiffness increased. The degenerated specimen stiffness was greater than the healthy and treated stiffness and the degenerate hysteresis loops were smaller. A mathematical model was found to successfully predict the high cycle behaviour of the disc reaching a root mean squared (RMS) error below 10% when using 5000 or more cycles. The linear regression gave a RMS error below 7.5% at 1000 cycles. Conclusions. A method was developed to consistently determine intervertebral disc mechanics through sequential testing. A shortened cyclic testing period was shown to be viable as a method to reduce preliminary test time for novel hydrogels, compared to currently literature. The methodology permits rapid preliminary assessment of intervertebral disc mechanics and treatments. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Intervertebral disc (IVD) degeneration is responsible for severe clinical symptoms including chronic back pain. Galectins are a family of carbohydrate-binding proteins, some of which can induce functional disease markers in IVD cells and other musculoskeletal diseases. Galectins −4 and −8 were shown to trigger disease-promoting activity in chondrocytes but their effects on IVD cells have not been investigated yet. This study elucidates the role of galectin-4 and −8 in IVD degeneration. Immunohistochemical evidence for the presence of galectin-4 and −8 in the IVD was comparatively provided in specimens of 36 patients with spondylochondrosis, spondylolisthesis, or spinal deformity. Confocal microscopy revealed co-localization of galectin-4 and −8 in chondrocyte clusters of degenerated cartilage. The immunohistochemical presence of galectin-4 correlated with histopathological and clinical degeneration scores of patients, whereas galectin-8 did not show significant correlations. The specimens were separated into annulus fibrosus (AF), nucleus pulposus (NP) and endplate, which was confirmed histologically. Separate cell cultures of AF and NP (n=20) were established and characterized using cell type-specific markers. Potential binding sites for galectins including sialylated N-glycans and LacdiNAc structures were determined in AF and NP cells using LC/ESI-MS-MS. To assess galectin functions, cell cultures were treated with recombinant galectin-4 or −8, in comparison to IL-1β, and analyzed using RT-qPCR and In-cell Western blot. In vitro, both galectins triggered the induction of functional disease markers (CXCL8 and MMP3) on mRNA level and activated the nuclear factor-kB pathway. NP cells were significantly more responsive to galectin-8 and Il-1β than AF cells. Phosphorylation of p-65 was time-dependently induced by both galectins in both cell types to a comparable extent. Taken together, this study provides evidence for a functional role of glycobiological processes in IVD degeneration and highlights galectin-4 and −8 as regulators of pro-inflammatory and degrative processes in AF and NP cells

Intervertebral disc (IVD) degeneration is the most frequent cause of Low Back Pain (LBP) affecting nearly 80% of the population [1]. Current treatments fail to restore a functional IVD or to provide a long-term solution, so, there is an urgent need for novel therapeutic strategies. We have defined the IVD extracellular matrix (ECM) profile, showing that the pro-regenerative molecules Collagen type XII and XIV, are uniquely expressed during fetal stages [2]. Now we propose the first fetal injectable biomaterial to regenerate the IVD. Fetal decellularized IVD scaffolds were recellularized with adult IVD cells and further implanted in vivo to evaluate their anti-angiogenic potential. Young decellularized IVD scaffolds were used as controls. Finally, a large scale protocol to produce a stable, biocompatible and easily injectable fetal IVD-based hydrogel was developed. Fetal scaffolds were more effective at promoting Aggrecan and Collagen type II expression by IVD cells. In a Chorioallantoid membrane assay, only fetal matrices showed an anti-angiogenic potential. The same was observed in vivo when the angiogenesis was induced by human NP cells. In this context, human NP cells were more effective in GAG synthesis within a fetal microenvironment. Vaccum-assisted perfusion decellularized IVDs were obtained, with high DNA removal and sGAG retention. Hydrogel pre-solution passed through 21-30G needles. IVD cells seeded on the hydrogels initially decreased metabolic activity, but increased up to 70% at day 7, while LDH assay revealed cytotoxicity always below 30%. This study will open new avenues for the establishment of a disruptive treatment for IVD degeneration with a positive impact on the angiogenesis associated with LBP, and on the improvement of patients’ quality of life. Acknowledgements: Financial support was obtained from EUROSPINE, ON Foundation and FCT (Fundação para a Ciência e a Tecnologia)

Intervertebral disc degeneration (IDD) affects more than 80% of the population all over the world. Current strategies for the treatment of IDD are based on conservative or surgical procedures with the aim of relieving pain. Mesenchymal stem cell (MSC) transplantation has emerged as a promising therapy in recent decades, but studies showed that the particularly hostile microenvironment in the intervertebral disc (IVD) can compromise cells survival rate. The use of exosomes, extracellular vesicles released by various cell types, possess considerable economic advantages including low immunogenicity and toxicity. Exosomes allow intercellular communication by conveying functional proteins, RNA, miRNA and lipids between cells. The purpose of this study is to assess the therapeutic effects of exosomes derived from Wharton Jelly mesenchymal stromal cells (WJ-MSC) on human nucleuspulposus cells (hNPC) in an in vitro 3D culture model. Exosomes (exos) were isolated by tangential flow filtration of WJ-MSC conditioned media and characterized by: quantification with BCA test; morphological observation with TEM, surface marker expression by WB and size evaluation by NTA. Confocal microscopy has been used to identify exosomes marked with PKH26 and monitor fusion and/or incorporation in hNPC. hNPC were isolated from waste surgical material from patients undergoing discectomy (n = 5), expanded, encapsulated in alginate beads and treated with: culture medium (control group); WJ-MSC exos (WJ-exos) at different concentrations (10 μg/ml, 50 μg/ml and 100 μg/ml). They were then analysed for: cell proliferation (Trypan Blu); viability (Live/Dead Assay); quantification of nitrites (Griess) and glycosaminoglycans, GAG (DMBB). The hNPC in alginate beads treated for 7 days were included in paraffin and histologically analysed to determine the presence of extracellular matrix (ECM) components. Finally, the expression levels of catabolic and anabolic genes were evaluated through real-time polymerase chain reaction (qPCR). All concentrations of WJ-exos under exam were capable to induce a significant increase in cell proliferation after 10 and 14 days of treatment (p < 0.01 and p < 0.001, respectively). Live/Dead assay showed a decrease in cell death at 50 μg/ml of WJ-exos (p < 0.05). While cellular oxidative stress indicator, nitrite production, was reduced in a dose-dependent way and statistically significant only with 100 μg/ml of WJ-exos (p < 0.05). WJ-exos at 10 and 100 μg/ml induced a significant increase in GAG content (p < 0.05; p < 0.01, respectively) confirmed by Alcian Blu staining. Exos derived from WJ-MSC modulated gene expression levels by increasing expression of ACAN and SOX-9 genes and reducing significantly of IL-6, MMP-1, MMP-13 and ADAMTS-5 levels (p < 0.05; p < 0.01) compared to the control group. Our results supported the potential use of exosomes from WJ-MSC for the treatment of IDD. Exosomes improved hNPC growth, attenuated ECM degradation and reduced oxidative stress and inflammation. This study offers a new scenario in IVD regeneration, promoting the potential use of extracellular vesicles as an alternative strategy to cell therapy

Intervertebral disc (IVD) degeneration is a pathological process often associated with chronic back pain and considered a leading cause of disability worldwide. 1. During degeneration, progressive structural and biochemical changes occur, leading to blood vessel and nerve ingrowth and promoting discogenic pain. 2. In the last decades, several cytokines have been applied to IVD cells in vitro to investigate the degenerative cascade. Particularly, IL-10 and IL-4 have been predicted as important anabolic factors in the IVD according to a regulatory network model based in silico approach. 3. Thus, we aim to investigate the potential presence and anabolic effect of IL-10 and IL-4 in human NP cells (in vitro) and explants (ex vivo) under hypoxia (5% O2) after a catabolic induction. Primary human NP cells were expanded, encapsulated in 1.2% alginate beads (4 × 106 cells/ml) and cultured for two weeks in 3D for phenotype recovery while human NP explants were cultured for five days. Afterwards, both alginate and explant cultures were i) cultured for two days and subsequently treated with 10 ng/ml IL-10 or IL-4 (single treatments) or ii) stimulated with 0.1 ng/ml IL-1β for two days and subsequently treated with 10 ng/ml IL-10 or IL-4 (combined treatments). The presence of IL-4 receptor, IL-4 and IL-10 was confirmed in human intact NP tissue (Fig 1). Additionally, IL-4 single and combined treatments induced a significant increase of proinflammatory protein secretion in vitro (Fig. 2A-C) and ex vivo (Fig. 2D and E). In contrast, no significant differences were observed in the secretome between IL-10 single and combined treatments compared to control group. Overall, IL-4 containing treatments promote human NP cell and explant catabolism in contrast to previously reported IL-4 anti-inflammatory performance. 4. Thus, a possible pleiotropic effect of IL-4 could occur depending on the IVD culture and environmental condition. Acknowledgements: This project was supported by the Marie Skłodowska Curie International Training Network “disc4all” under the grant agreement #955735. For any figures and tables, please contact the authors directly

Mechanical loading is important to maintain the homeostasis of the intervertebral disc (IVD) under physiological conditions but can also accelerate cell death and tissue breakdown in a degenerative state. Bioreactor loaded whole organ cultures are instrumental for investigating the effects of the mechanical environment on the IVD integrity and for preclinical testing of new therapies under simulated physiological conditions. Thereby the loading parameters that determine the beneficial or detrimental reactions largely depend on the IVD model and its preparation. Within this symposium we are discussing the use of bovine caudal IVD culture models to reproduce tissue inflammation or matrix degradation with or without bioreactor controlled mechanical loading. Furthermore, the outcome parameters that define the degenerative state of the whole IVD model will be outlined. Besides the disc height, matrix integrity, cell viability and phenotype expression, the tissue secretome can provide indications about potential interactions of the IVD with other cell types such as neurons. Finally, a novel multiaxial bioreactor setup capable of mimicking the six degrees-of-freedom loading environment of IVDs will be introduced that further advances the relevance of preclinical ex-vivo testing