Aims. This study was performed to explore the effect of melatonin on pyroptosis in nucleus pulposus cells (NPCs) and the underlying mechanism of that effect. Methods. This experiment included three patients diagnosed with lumbar disc herniation who failed conservative treatment. Nucleus pulposus tissue was isolated from these patients when they underwent surgical intervention, and primary NPCs were isolated and cultured. Western blotting, reverse transcription polymerase chain reaction, fluorescence staining, and other methods were used to detect changes in related signalling pathways and the ability of cells to resist pyroptosis. Results. Western blot analysis confirmed the expression of cleaved CASP-1 and melatonin receptor (MT-1A-R) in NPCs. The cultured NPCs were identified by detecting the expression of CD24, collagen type II, and aggrecan. After treatment with hydrogen peroxide, the pyroptosis-related proteins NLR family pyrin domain containing 3 (NLRP3), cleaved CASP-1, N-terminal fragment of gasdermin D (GSDMD-N), interleukin (IL)-18, and IL-1β in NPCs were upregulated, and the number of propidium iodide (PI)-positive cells was also increased, which was able to be alleviated by pretreatment with melatonin. The protective effect of melatonin on pyroptosis was blunted by both the melatonin receptor antagonist luzindole and the nuclear factor erythroid 2–related factor 2 (Nrf2) inhibitor ML385. In addition, the expression of the transcription factor Nrf2 was up- or downregulated when the melatonin receptor was activated or blocked by melatonin or luzindole, respectively. Conclusion. Melatonin protects NPCs against reactive oxygen species-induced pyroptosis by upregulating the transcription factor Nrf2 via melatonin receptors. Cite this article: Bone Joint Res 2023;12(3):202–211

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

The aim of this study is to clarify the implication of ciliary pathway on the onset of the spinal curvature that occurs in Adolescent Idiopathic Scoliosis (AIS) patients through functional studies of two genes: POC5 and TTLL11. Since the genetic implication for AIS is accepted, many association and candidate gene analysis revealed the implication of ciliary genes. The characterisation of these two proteins was assessed by qPCR, WB and immunofluorescence in vitro using control cells and cells derived from AIS patients. The impact of genetic modification of these genes on the functionality of the proteins in vitro and in vivo was analysed in zebrafish model created by CRISPR/Cas9 using microCT and histologic analysis. Our study revealed that mutant cells, for both gene, were less ciliated and the primary cilia was significantly shorter compared to control cells. We also observed a default in cilia glutamylation by immunofluorescence and Western Blot. Moreover, we observed in both zebrafish model, a 3D spine curvature similar to the spinal deformation in AIS. Interestingly, our preliminary results of immunohistology showed a retinal defect, especially at the cone cell layer level. This study strongly supports the implication of the ciliary pathway in the onset of AIS and this is the first time that a mechanism is described for AIS. Indeed, we show that shorter cilia could be less sensitive to environmental factors due to lower glutamylation and result in altered signalling pathway. Identifying the biological mechanism involved is crucial for elucidating AIS pathogenesis

Background. Currently, there is a focus on the development of cell based therapies to treat intervertebral disc (IVD) degeneration, particularly for regenerating/repairing the central region, the nucleus pulposus (NP). Recently, we demonstrated that GDF6 promotes NP-like differentiation in mesenchymal stem cells (MSCs). However, bone marrow- (BM-MSCs) and adipose- (Ad-MSCs) showed differential responses to GDF6, with Ad-MSCs adopting a more NP-like phenotype. Here, we investigated GDF6 signalling in BM-MSCs and Ad-MSCs, with the aim to improve future IVD stem cell therapies. Methods. GDF6 receptor expression in patient-matched BM-MSCs and Ad-MSCs (N=6) was profiled through western blot and immunocytochemistry (ICC). GDF6 signal transduction was investigated through stimulation with 100 ng ml. −1. GDF6 for defined time periods. Subsequently smad1/5/9 phosphorylation and alternative non-smad pathway activation (phospho-p38; phospho-Erk1/2) was analysed (western blot, ELISA). Their role in inducing NP-like gene expression in Ad-MSCs was examined through pathway specific inhibitors. Results. Western blot and ICC established that BMPR profiles differed between MSC populations; specifically, BMPR2 (a GDF6 receptor) expression, was significantly higher in Ad-MSCs (p<0.05). ELISA and western blot analysis showed that smad1/5/9 phosphorylation was significantly higher in Ad-MSCs following GDF6 stimulation (p<0.05). GDF6 stimulation also phosphorylated p38 and Erk1/2 pathways. Blocking of both smad and non-smad pathways resulted in variation of GDF6 induced NP-like gene expression. Conclusions. The upregulation of BMPR2 in Ad-MSCs and corresponding differences in smad1/5/9 and non-smad pathway phosphorylation in response to GDF6 indicates an enhanced discogenic potential in Ad-MSCs, suggesting they may be more suitable for GDF6 mediated cellular IVD regeneration. Conflicts of interest. No conflicts of interest. Sources of funding. We would like to acknowledge UKRMP Acellular Hub, MRC, NIHR Musculoskeletal BRU and The Rosetrees Trust for funding this research

Aims

In this investigation, we administered oxidative stress to nucleus pulposus cells (NPCs), recognized DNA-damage-inducible transcript 4 (DDIT4) as a component in intervertebral disc degeneration (IVDD), and devised a hydrogel capable of conveying small interfering RNA (siRNA) to IVDD.

Background. Degeneration of the intervertebral disc (IVD) is a leading cause of lower back pain, and a significant clinical problem. Inflammation mediated by IL-1β and TNF-α drives IVD degeneration through promoting a phenotypic switch in the resident nucleus pulposus (NP) cells towards a more catabolic state, resulting in extracellular matrix degradation. Bone marrow mesenchymal stem cells (MSCs) produce bioactive factors that modulate local tissue microenvironments and their anti-inflammatory potential has been shown in numerous disease models. Thus MSCs offer a potential therapy for IVD degeneration. In a clinical setting, adipose-derived stem cells (ASCs) might represent an alternative and perhaps more appealing cell source. However, their anti-inflammatory properties remain poorly understood. Methods. Here we assess the anti-inflammatory properties of donor-matched human ASCs and MSCs using qPCR and western blotting. Results. We demonstrate that stimulating ASCs or MSCs with IL-1β and/or TNF-α elicits a strong anti-inflammatory response with increased expression of IL-1 receptor antagonist (IL-1Ra), cyclooxygenase-2 (COX-2) and the tissue protective protein tumour-necrosis factor stimulated gene-6 (TSG-6). ASCs produced significantly higher levels of IL-1Ra and TSG-6 than their matched MSCs at both gene and protein levels, indicating that ASCs are potentially a more potent anti-inflammatory cell type. This anti-inflammatory response was also observed upon co-culture with degenerate NP cells without exogenous cytokine. Signalling analyses suggested this difference between cell types might be mediated through differences in the activation of inflammation-associated transcription factors. Conclusion. These data indicate that the anti-inflammatory properties of ASCs may be useful in developing future therapies for IVD degeneration. No conflicts of interest. Sources of funding: EPSRC-MRC Centre for Doctoral Training in Regenerative Medicine (EP/L014904/1)

Aims

Non-coding microRNA (miRNA) in extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) may promote neuronal repair after spinal cord injury (SCI). In this paper we report on the effects of MSC-EV-microRNA-381 (miR-381) in a rodent model of SCI.

Background. Signalling by growth differentiation factor 6 (GDF6/BMP13) has been implicated in the development and maintenance of healthy NP cell phenotypes and GDF6 mutations are associated with defective vertebral segmentation in Klippel-Feil syndrome. GDF6 may thus represent a promising biologic for treatment of IVD degeneration. This study aimed to investigate the effect of GDF6 in human NP cells and critical signal transduction pathways involved. Methods. BMP receptor expression profile of non-degenerate and degenerate human NP cells was determined through western blot, immunofluorescence and qPCR. Phosphorylation statuses of Smad1/5/9 and non-canonical p38 MAPK and Erk1/2 were assessed in the presence/absence of pathway blockers. NP marker and matrix degrading enzyme gene expression was determined by qPCR following GDF6 stimulation. Glycosaminoglycan and collagen production were assessed through DMMB-assay and histochemical staining. Results. NP cells expressed all GDF6 receptor subunits, with receptor subunits BMPR-1A and BMPR2 displaying the highest expression and highest binding affinity. GDF6 stimulation significantly upregulated the expression of NP specific marker genes but had no significant effect on the expression of matrix degrading enzymes. Total glycosaminoglycan and collagen production was also significantly increased following GDF6 stimulation. Smad1/5/9, p38 MAPK and Erk1/2 pathways were phosphorylated following GDF6 stimulation and could be effectively blocked. Conclusions. These findings enhance our understanding of both the effects of GDF6 in NP cells and the mechanisms of GDF6 signal transduction that are critical to promote NP phenotype and cellular function. This knowledge is important for the effective use of GDF6 as a therapeutic molecule for treatment of IVD degeneration. Conflicts of interest. No conflicts of interest. Sources of funding. We would like to acknowledge UKRMP Acellular Hub, MRC, NIHR Musculoskeletal BRU and The Rosetrees Trust for funding this research

Aims

Inflammatory response plays a pivotal role in the pathophysiological process of intervertebral disc degeneration (IDD). A20 (also known as tumour necrosis factor alpha-induced protein 3 (TNFAIP3)) is a ubiquitin-editing enzyme that restricts nuclear factor-kappa B (NF-κB) signalling. A20 prevents the occurrence of multiple inflammatory diseases. However, the role of A20 in the initiation of IDD has not been elucidated. The aim of the study was to investigate the effect of A20 in senescence of TNF alpha (TNF-α)-induced nucleus pulposus cells (NPCs).

Introduction. From the many human studies that attempt to identify genes for adolescent idiopathic scoliosis (AIS), the view emerging is that AIS is a complex genetic disorder with many predisposing genes exhibiting complex phenotypes through environmental interactions. Although advancements in genomic technology are transforming how we undertake genetic and genomic studies, only some success has been reached in deciphering complex diseases such as AIS. Moreover, the present challenge in AIS research is to understand the causative and correlative effects of discovered genetic perturbations. An important limitation to such investigations has been the absence of a method that can easily stratify patients with AIS. To overcome these challenges, we have developed a functional test that allows us to stratify patients with AIS into three functional subgroups, representing specific endophenotypes. Interestingly, in families with multiple cases of AIS, a specific endophenotype is shared among the affected family members, indicating that such a transmission is inherited. Moreover, increased vulnerability to AIS could be attributable to sustained exposure to osteopontin (OPN), a multifunctional cytokine that appears to be at the origin of the Gi-coupled receptor signalling dysfunction discovered in AIS. We examined the molecular expression profiles of patients with AIS and their response to OPN. Methods. Osteoblasts isolated from patients with AIS were selected for each functional subgroup and compared with osteoblasts obtained from healthy matched controls. We used the latest gene chip human genome array Affymetrix (HuU133 Plus 2.0 array) that allows for the analysis of the expression level of 38 000 well characterised human genes. Raw data were normalised with robust multiarray analysis method. Statistical analysis was done by the EB method with FlexArray software. Selection criteria for in-depth analysis include the magnitude of change in expression (at least □} 3-fold) and 5% false discovery rate as stringency selection. Validation of selected candidate genes was done by qPCR and at the protein level by Western blot and ELISA methods. Plasma OPN concentrations were measured by ELISA on a group of 683 consecutive patients with AIS and were compared with 262 healthy controls and 178 asymptomatic offspring, born from at least one scoliotic parent, and thus considered at risk of developing the disorder. The regulation of OPN signalling pathway in normal and AIS cells were validated in vitro by cellular dielectric spectroscopy (CDS). Results. Of 38 000 human genes tested, we have found eight genes specifically associated with the functional subgroup 1, 16 genes with the functional subgroup 2, and 11 genes with the functional subgroup 3. Interestingly, only 19 genes were shared and affected to the same extent in all AIS functional subgroups exhibiting a similar curve pattern (double major), suggesting their role in the formation of this curve pattern. Indeed, most of these genes encode for regulatory proteins such as transcription factors regulating axial skeleton, somite development, and extracellular matrix proteins. Mean plasma OPN concentrations were significantly increased in patients with AIS and correlated with disease severity. Increased plasma OPN concentrations were also detected in the asymptomatic at-risk group, suggesting that these changes precede scoliosis onset. CDS experiments clearly showed that OPN exposure triggers a Gi-coupled receptor signalling dysfunction, which is exacerbated by oestrogens. Conclusions. Our data further support our functional method of stratification of patients with AIS and allow the identification of genes triggering scoliosis onset versus those predisposing to the development of a specific curve pattern. Furthermore, our clinical and experimental data show that OPN is essential for scoliosis onset and curve progression, thus offering a first molecular concept to explain the pathomechanism leading to the asymmetrical growth of the spine in AIS. Acknowledgments. This research project was supported by grants from La Fondation Yves Cotrel de l'Institut de France, Canadian Institutes of Health Research, and Paradigm Spine LLC

We determined the frequency, rate and extent of development of scoliosis (coronal plane deformity) in wheelchair-dependent patients with Duchenne muscular dystrophy (DMD) who were not receiving steroid treatment. We also assessed kyphosis and lordosis (sagittal plane deformity). The extent of scoliosis was assessed on sitting anteroposterior (AP) spinal radiographs in 88 consecutive non-ambulatory patients with DMD. Radiographs were studied from the time the patients became wheelchair-dependent until the time of spinal fusion, or the latest assessment if surgery was not undertaken. Progression was estimated using a longitudinal mixed-model regression analysis to handle repeated measurements.

Scoliosis ≥ 10° occurred in 85 of 88 patients (97%), ≥ 20° in 78 of 88 (89%) and ≥ 30° in 66 of 88 patients (75%). The fitted longitudinal model revealed that time in a wheelchair was a highly significant predictor of the magnitude of the curve, independent of the age of the patient (p <  0.001). Scoliosis developed in virtually all DMD patients not receiving steroids once they became wheelchair-dependent, and the degree of deformity deteriorated over time.

In general, scoliosis increased at a constant rate, beginning at the time of wheelchair-dependency (p < 0.001). In some there was no scoliosis for as long as three years after dependency, but scoliosis then developed and increased at a constant rate. Some patients showed a rapid increase in the rate of progression of the curve after a few years – the clinical phenomenon of a rapidly collapsing curve over a few months.

A sagittal plane kyphotic deformity was seen in 37 of 60 patients (62%) with appropriate radiographs, with 23 (38%) showing lumbar lordosis (16 (27%) abnormal and seven (11%) normal).

This study provides a baseline to assess the effects of steroids and other forms of treatment on the natural history of scoliosis in patients with DMD, and an approach to assessing spinal deformity in the coronal and sagittal planes in wheelchair-dependent patients with other neuromuscular disorders.

Cite this article: Bone Joint J 2014;96-B:100–5.