Development, Pathogenesis, and Regeneration of the Intervertebral Disc: Current and Future Insights Spanning Traditional to Omics Methods

Multi-omics insights into bone tissue injury and healing: bridging orthopedic trauma and regenerative medicine

To preserve functionality, bone is an active tissue that can constantly reconstruct itself through modeling and remodeling. It plays critical roles in the body, including maintaining mineral homeostasis, serving as the adult human body's core site of hematopoiesis, and supporting the structures of the body's soft tissues. It possesses the natural regeneration capacity, but large and complex lesions often require surgical intervention. Multiple omics integrate proteomics, metabolomics, genomics, and transcriptomics to provide a comprehensive understanding of biological processes like bone tissue injury and healing in bone tissue regeneration and engineering. Recently, bone tissue engineering and regenerative medicines have offered promising tools for bone regeneration using a multi-omics approach. Thus, this article will highlight the role of multiple omics in understanding bone tissue injury and healing. It will discuss the role of bone tissue engineering in developing bone substitutes that can replace translational medicine. Lastly, new developments in bone tissue engineering and regenerative medicine, along with multi-omics approaches, offer promising tools for bone regeneration.

PDGF-Releasing Hydrogels for Enhanced Proliferation of Human Nucleus Pulposus Cells

Hydrogels offer a promising solution for sustained and controlled drug delivery and cell-tissue biocompatibility. In the intervertebral disc (IVD), delivering growth factors faces challenges due to the antagonistic inflammatory environment and continuous mechanical stress, which can degrade biological agents and may reduce their local activity. To address this, we investigated the prolonged release of platelet-derived growth factor isoforms BB (PDGF-BB) and AB (PDGF-AB) by using N-desulfated heparin methacrylamide (Hep-N) crosslinked within matrix-metalloproteinase sensitive poly(ethylene glycol) (PEG) hydrogels. Using electrostatic interactions between the heparin derivative and PDGF, we optimized a sustained release dose of PDGF-BB from the hydrogel in the presence of collagenase to mimic the in vivo environment. We then assessed the effects of PDGF released from PEG-hydrogel on human nucleus pulposus (NP) Cells. The MTT assay confirmed that 100 and 200 ng doses significantly increased cell viability by 2.52-fold and 2.46-fold on Day 3, respectively. RT-qPCR analysis revealed that PDGF-AB and PDGF-BB upregulated the expression of proliferation marker Ki-67 (MKI67) on both Day 3 and Day 5. Additionally, collagen type II alpha 1 chain (COL2A1) was significantly upregulated in the PDGF-AB group on Day 5, indicating potential anabolic effects. These findings could pave the way for long-term in vivo studies on sustainable PDGF treatment for IVD degeneration.

Engineering extracellular matrix-based hydrogels for intervertebral disc regeneration

Lower back pain (LBP) is a major health concern, especially in older adults. A key aetiological factor is intervertebral disc (IVD) degeneration. It is mediated by dysregulation of extracellular matrix (ECM) and inflammation. In recent years, regenerative therapies have garnered attention for their potential to restore disc function by addressing the underlying biological alterations within the IVD. This review focuses on the comprehensive understanding of the anatomy and physiology of the IVD, highlighting its life cycle from embryonic development, and maturation to degenerative phenotype. We describe current treatments for managing LBP caused by IVD degeneration. This review emphasizes on the recent advancements in hydrogel engineering, highlighting natural, synthetic, and composite hydrogels and their application in ECM-targeted regenerative therapy for IVD degeneration. By exploring innovations in hydrogel technology, including improvements in crosslinking techniques and controlled degradation rates-we discuss how these materials could enhance IVD regeneration and potentially be used for the management of LBP. With their enhanced biomimicry, hydrogel-based ECM mimics offer a promising pathway for developing effective, durable therapies that address the root causes of disc degeneration, providing new hope for individuals living with chronic LBP.

Advancements in Degenerative Disc Disease Treatment: A Regenerative Medicine Approach

Regenerative medicine represents a transformative approach to treating nucleus pulposus degeneration and offers hope for patients suffering from chronic low back pain due to disc degeneration. By focusing on restoring the natural structure and function of the nucleus pulposus rather than merely alleviating symptoms, these innovative therapies hold the potential to significantly improve patient outcomes. As research continues to advance in this field, we may soon witness a paradigm shift in how we approach spinal health and degenerative disc disease. The main purpose of this review is to provide an overview of the various regenerative approaches that target the restoration of the nucleus pulposus, a primary site for initiation of intervertebral disc degeneration.

In-silico proteomic analysis of the role of IL-4 and IL-10 in IVD degeneration: Protein-protein interaction networks for candidate prioritisation

Protein-protein interaction (PPI) networks provide a static map of functional protein interactions, which when combined with algorithms, can prioritize key protein candidates which experimental studies cannot capture. This study, aimed to construct knowledge-based nucleus pulposus (NP)-specific PPI networks which could be deployed to investigate complex protein interactions in human NP cells and tissues following IL-4 and IL-10 stimulation. NP-specific PPI networks were developed based on mass spectrometry (MS) and secretome datasets from human NP cells. These networks were validated using in vitro and ex vivo experimental data sets. Genes Underlying Inheritance Linked Disorders (GUILD) genome-wide network-based prioritization framework was employed for protein candidate prediction under no treatment baseline and IL-4, IL-10 and IL-1β single or combined stimulating scenarios. These secretome-based in vitro PPI networks were able to reproduce the no-treatment candidate prioritization baseline. Whereby within NP cells from discs isolated due to traumatic injury biglycan was identified whilst in degenerate samples decorin was highlighted. Furthermore, experimentally observed IL-4 pleiotropic behaviour was predicted by IL-1 receptor-like 1 prioritization. PPI network-based IL-4 and IL-10 conditions offered novel insights of potential candidates, including collagen IV and fibroblast growth factor intracellular binding protein (FIBP) as key candidates within IL-4 activation pathways, whereas urocortin 3 and neural growth factor were identified following IL-10 stimulation. Additionally, MS based PPI network propagation offered a more extensive, module-based structure networks with lower edge degree and biological variability. Overall, multiple proteomic experimental approaches are required to successfully validate in-silico prediction models to understand the complex interactions between the plethora of proteins involved in IVD degeneration.

Chitin nanocrystal-reinforced chitin/collagen composite hydrogels for annulus fibrosus repair after discectomy

Discectomy is a widely utilized approach for alleviating disc herniation; however, effective repair of postoperative annulus fibrosus (AF) defects remains a significant challenge. This study introduces a hydrogel patch with enhanced mechanical properties for AF repair fabricated using chitin (Ch), collagen (Col), and chitin nanocrystals (ChNCs) through a freeze-thaw cycling technique. The Ch and Col components constitute the matrix of the hydrogel patch, while uniformly dispersed ChNCs act as a nanofiller, markedly improving the mechanical performance (compression strain: 95 %; compression modulus: 0.27 MPa) of the resulting Ch/Col@ChNCs hydrogel patch. The patch demonstrates advantageous properties, including high porosity, superior water absorption, thermal stability, and biodegradability in simulated body fluid. In vitro assessments reveal excellent biocompatibility with AF cells and enhanced collagen deposition. Furthermore, in vivo studies confirm that the patch effectively repairs postoperative disc defects, exhibiting strong integration with surrounding tissues and facilitating the orderly regeneration of fibrous tissue. This innovative hydrogel patch, combining exceptional properties with a straightforward fabrication process, presents a viable strategy for advancing clinical biomaterials for postoperative AF repair.

Understanding the comorbidities among psychiatric disorders, chronic low-back pain, and spinal degenerative disease using observational and genetically informed analyses

Psychiatric disorders and symptoms are associated with differences in pain perception and sensitivity. These differences can have important implications in treating spinal degenerative disease (SDD) and chronic low-back pain (CLBP). Leveraging data from the UK Biobank (UKB) and the All of Us Research Program (AoU), we investigated the effects linking psychiatric disorders (alcohol use disorder, anxiety, attention deficit hyperactivity disorder, bipolar disorder, cannabis use disorder, depression, opioid use disorder, posttraumatic stress disorder, and schizophrenia) to SDD and CLBP. We applied multi-nominal regression models, polygenic risk scoring (PRS), and one-sample Mendelian randomization (MR) to triangulate the effects underlying the associations observed. We also performed gene ontology and drug-repurposing analyses to dissect the biology shared among mental illnesses, SDD, and CLBP. Comparing individuals affected only by SDD (UKB N=37,745, AoU N=3,477), those affected only by CLBP (UKB N=15,496, AoU N=23,325), and those affected by both conditions (UKB N=11,463, AoU N= 13,451) to controls (UKB N=337,362, AoU N= 117,162), observational and genetically informed analyses highlighted that the strongest effects across the three case groups were observed for alcohol use disorder, anxiety, depression, and posttraumatic stress disorder. Additionally, schizophrenia and its PRS appeared to have an inverse relationship with CLBP, SDD, and their comorbidity. One-sample MR highlighted a potential direct effect of internalizing disorders on the outcomes investigated that was particularly strong on SDD. Our drug-repurposing analyses identified histone deacetylase inhibitors as targeting molecular pathways shared among psychiatric disorders, SDD, and CLBP. In conclusion, these findings support that the comorbidity among psychiatric disorders, SDD, and CLBP is due to the contribution of direct effects and shared biology linking these health outcomes. These pleiotropic mechanisms together with sociocultural factors play a key role in shaping the SDD-CLBP comorbidity patterns observed across the psychopathology spectrum.

Revolutionizing the treatment of intervertebral disc degeneration: an approach based on molecular typing

BACKGROUND

Intervertebral disc degeneration (IVDD) is a significant cause of global disability, reducing labor productivity, increasing the burden on public health, and affecting socio-economic well-being. Currently, there is a lack of recognized clinical approaches for molecular classification and precision therapy.

METHODS

Chondrocyte differentiation and prognosis-related genes were extracted from single-cell RNA sequencing and multi-omics data in the Gene Expression Omnibus (GEO) database through chondrocyte trajectory analysis and non-parametric tests. Subsequently, a precise IVDD risk stratification system was developed using ConsensusClusterPlus analysis. The clinical significance of molecular typing was demonstrated through case-control trials involving IVDD patients. Specific inhibitors of molecular typing were predicted using the pRRophetic package in R language and then validated in vitro.

RESULTS

A stratified model for IVDD, considering chondrocyte differentiation and demonstrating high clinical relevance, was developed using a set of 44 chondrocyte fate genes. Extensive analyses of multi-omics data confirmed the clinical relevance of this model, indicating that cases in the High Chondrocyte Scoring Classification (HCSC) group had the most favorable prognosis, whereas those in the Low Chondrocyte Scoring Classification (LCSC) group had the worst prognosis. Additionally, clinical case-control studies provided evidence of the utility of IVDD molecular typing in translational medicine. A gene expression-based molecular typing approach was used to create a matrix identifying potential inhibitors specific to each IVDD subtype. In vitro experiments revealed that gefitinib, a drug designed for LCSC, not only had protective effects on chondrocytes but also could induce the conversion of LCSC into the HCSC subgroup. Therefore, IVDD molecular typing played a critical role in assisting clinicians with risk stratification and enabling personalized treatment decisions.

CONCLUSION

The results of the study have provided a comprehensive and clinically relevant molecular typing for IVDD, involving a precise stratification system that offers a new opportunity for customizing personalized treatments for IVDD.

HIF-1α protects nucleus pulposus cells from oxidative stress-induced mitochondrial impairment through PDK-1

The pathogenesis of intervertebral disc degeneration (IVDD) involves complex signaling networks and various effector molecules, and our understanding of the pathogenesis of IVDD is limited. Hypoxia inducible factor-1α (HIF-1α) is closely related to IVDD, and there is excessive oxidative stress concurrent with IVDD. In this study, we found that HIF-1α could protect nucleus pulposus cells from excessive oxidative stress by reversing the imbalance between oxidants and antioxidants and thus mitigating the oxidative stress-induced mitochondrial impairment. With further exploration, we found that pyruvate dehydrogenase kinase 1 (PDK-1) was involved in the protective effect of HIF-1α on nucleus pulposus cells under oxidative stress. We suggested that HIF-1α could preserve the mitochondrial integrity and activate glycolysis in nucleus pulposus cells via PDK-1, and the addition of DCA, a PDK-1 inhibitor, could blunt the protective effect of HIF-1α. In addition, the HIF-1α/PDK-1 regulatory axis was also confirmed in vivo through HIF-1α knockout mice model. Therefore, we propose that HIF-1α protects nucleus pulposus cells from excessive oxidative stress by maintaining the mitochondrial integrity and glycolysis via PDK-1, thus enriching the insight into the protective mechanism of HIF-1α against IVDD, and providing a novel therapeutic target for the treatment of IVDD.

Effect of patient-specific factors on regeneration in lumbar spine at healthy disc and total disc replacement. Computer simulation

BACKGROUND AND OBJECTIVE

Degenerative diseases of the spine have a negative impact on the quality of life of patients. This study presents the results of numerical modelling of the mechanical behaviour of the lumbar spine with patient-specific conditions at physiological loads. This paper aims to numerically study the influence of degenerative changes in the spine and the presence of an endoprosthesis on the creation of conditions for tissue regeneration.

METHODS

A numerical model of the mechanical behaviour of lumbar spine at healthy and after total disc replacement under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behaviour of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid. The nutritional pathways of the intervertebral disc in cases of healthy and osteoporotic bone tissues were predicted based on the analysis of the simulation results according to the mechanobiological principles.

RESULTS

Simulation of total disc replacement showed that osseointegration of the artificial disc plates occurs only in healthy bone tissue. With total disc replacement in a patient with osteoporosis, there is an area of increased risk of bone resorption in the near-contact area, approximately 1 mm wide, around the fixators. Dynamic loads may improve the osseointegration of the implant in pathological conditions of the bone tissue.

CONCLUSIONS

The results obtained in the case of healthy spine and osteoporotic bone tissues correspond to the experimental data on biomechanics and possible methods of IVD regeneration from the position of mechanobiological principles. The results obtained with an artificial disc (with keel-type fixation) showed that the use of this type of endoprosthesis in healthy bone tissues allows to reproduce the function of the natural intervertebral disc and does not contribute to the development of neoplastic processes. In the case of an artificial disc with osteoporosis of bone tissues, there is a zone with increased risk of tissue resorption and development of neoplastic processes in the area near the contact of the implant attachment. This circumstance can be compensated by increasing the loading level.

Perspective on Intradiscal Therapies for Lumbar Discogenic Pain: State of the Science, Knowledge Gaps, and Imperatives for Clinical Adoption

Specific clinical diagnostic criteria have established a consensus for defining patients with lumbar discogenic pain. However, if conservative medical management fails, these patients have few treatment options short of surgery involving discectomy often coupled with fusion or arthroplasty. There is a rapidly-emerging research effort to fill this treatment gap with intradiscal therapies that can be delivered minimally-invasively via fluoroscopically guided injection without altering the normal anatomy of the affected vertebral motion segment. Viable candidate products to date have included mesenchymal stromal cells, platelet-rich plasma, nucleus pulposus structural allograft, and other cell-based compositions. The objective of these products is to repair, supplement, and restore the damaged intervertebral disc as well as retard further degeneration. In doing so, the intervention is meant to eliminate the source of discogenic pain and avoid surgery. Methodologically rigorous studies are rare, however, and based on the best clinical evidence, the safety as well as the magnitude and duration of clinical efficacy remain difficult to estimate. Further, we summarize the US Food and Drug Administration's (FDA) guidance regarding the interpretation of the minimal manipulation and homologous use criteria, which is central to designating these products as a tissue or as a drug/device/biologic. We also provide perspectives on the core evidence and knowledge gaps associated with intradiscal therapies, propose imperatives for evaluating effectiveness of these treatments and highlight several new technologies on the horizon.

Development and Degeneration of the Intervertebral Disc-Insights from Across Species

Back pain caused by intervertebral disc (IVD) degeneration has a major socio-economic impact in humans, yet historically has received minimal attention in species other than humans, mice and dogs. However, a general growing interest in this unique organ prompted the expansion of IVD research in rats, rabbits, cats, horses, monkeys, and cows, further illuminating the complex nature of the organ in both healthy and degenerative states. Application of recent biotechnological advancements, including single cell RNA sequencing and complex data analysis methods has begun to explain the shifting inflammatory signaling, variation in cellular subpopulations, differential gene expression, mechanical loading, and metabolic stresses which contribute to age and stress related degeneration of the IVD. This increase in IVD research across species introduces a need for chronicling IVD advancements and tissue biomarkers both within and between species. Here we provide a comprehensive review of recent single cell RNA sequencing data alongside existing case reports and histo/morphological data to highlight the cellular complexity and metabolic challenges of this unique organ that is of structural importance for all vertebrates.

Recent developments in nanomaterials for upgrading treatment of orthopedics diseases

Nanotechnology has changed science in the last three decades. Recent applications of nanotechnology in the disciplines of medicine and biology have enhanced medical diagnostics, manufacturing, and drug delivery. The latest studies have demonstrated this modern technology's potential for developing novel methods of disease detection and treatment, particularly in orthopedics. According to recent developments in bone tissue engineering, implantable substances, diagnostics and treatment, and surface adhesives, nanomedicine has revolutionized orthopedics. Numerous nanomaterials with distinctive chemical, physical, and biological properties have been engineered to generate innovative medication delivery methods for the local, sustained, and targeted delivery of drugs with enhanced therapeutic efficacy and minimal or no toxicity, indicating a very promising strategy for effectively controlling illnesses. Extensive study has been carried out on the applications of nanotechnology, particularly in orthopedics. Nanotechnology can revolutionize orthopedics cure, diagnosis, and research. Drug delivery precision employing nanotechnology using gold and liposome nanoparticles has shown especially encouraging results. Moreover, the delivery of drugs and biologics for osteosarcoma is actively investigated. Different kind of biosensors and nanoparticles has been used in the diagnosis of bone disorders, for example, renal osteodystrophy, Paget's disease, and osteoporosis. The major hurdles to the commercialization of nanotechnology-based composite are eventually examined, thus helping in eliminating the limits in connection to some pre-existing biomaterials for orthopedics, important variables like implant life, quality, cure cost, and pain and relief from pain. The potential for nanotechnology in orthopedics is tremendous, and most of it looks to remain unexplored, but not without challenges. This review aims to highlight the up tp date developments in nanotechnology for boosting the treatment modalities for orthopedic ailments. Moreover, we also highlighted unmet requirements and present barriers to the practical adoption of biomimetic nanotechnology-based orthopedic treatments.

Isoginkgetin-loaded reactive oxygen species scavenging nanoparticles ameliorate intervertebral disc degeneration via enhancing autophagy in nucleus pulposus cells

Excessive reactive oxygen species (ROS) in nucleus pulposus cells (NPCs) promote extracellular matrix (ECM) degradation and cellular inflammatory responses by activating a variety of cellular pathways, ultimately inducing cell apoptosis and leading to the development of low back pain. Here, we designed and fabricated an isoginkgetin-loaded ROS-responsive delivery system (IGK@SeNP) based on diselenide block copolymers. Successfully encapsulated IGK was released intelligently and rapidly in a microenvironment with high ROS levels in degenerative disc. Controlled-release IGK not only efficiently scavenged ROS from the intervertebral disc together with diselenide block copolymers but also effectively enhanced autophagy in NPCs to inhibit ECM degradation and cell apoptosis, and showed significant therapeutic effects in the rat intervertebral disc degeneration (IDD) model. Overall, the synergistic effects of IGK@SeNP in ROS scavenging and autophagy enhancement endowed it with an attractive therapeutic strategy for IDD treatment.

Integrated proteome sequencing, bulk RNA sequencing and single-cell RNA sequencing to identify potential biomarkers in different grades of intervertebral disc degeneration

Low back pain (LBP) is a prevalent health problem worldwide that affects over 80% of adults during their lifetime. Intervertebral disc degeneration (IDD) is a well-recognized leading cause of LBP. IDD is classified into five grades according to the Pfirrmann classification system. The purpose of this study was to identify potential biomarkers in different IDD grades through an integrated analysis of proteome sequencing (PRO-seq), bulk RNA sequencing (bRNA-seq) and single-cell RNA sequencing (scRNA-seq) data. Eight cases of grade I-IV IDD were obtained. Grades I and II were considered non-degenerative discs (relatively normal), whereas grades III and IV were considered degenerative discs. PRO-seq analysis was performed to identify differentially expressed proteins (DEPs) in various IDD grades. Variation analysis was performed on bRNA-seq data to differentiate expressed genes (DEGs) in normal and degenerated discs. In addition, scRNA-seq was performed to validate DEGs in degenerated and non-degenerated nucleus pulposus (NP). Machine learning (ML) algorithms were used to screen hub genes. The receiver operating characteristic (ROC) curve was used to validate the efficiency of the screened hub genes to predict IDD. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to analyze function enrichment and signaling pathways. Protein-protein interaction (PPI) network was used to prioritize disease-related proteins. SERPINA1, ORM2, FGG and COL1A1 were identified through PRO-seq as the hub proteins involved in regulating IDD. ML algorithms selected ten hub genes, including IBSP, COL6A2, MMP2, SERPINA1, ACAN, FBLN7, LAMB2, TTLL7, COL9A3, and THBS4 in bRNA-seq. Since serine protease inhibitor clade A member 1 (SERPINA1) was the only common gene, its accuracy in degenerated and non-degenerated NP cells was validated using scRNA-seq. Then, the rat degeneration model of caudal vertebra was established. The expression of SERPINA1 and ORM2 was detected using immunohistochemical staining of human and rat intervertebral discs. The results showed that SERPINA1 was poorly expressed in the degenerative group. We further explored the potential function of SERPINA1 by Gene Set Enrichment Analysis (GSEA) and cell-cell communication. Therefore, SERPINA1 can be used as a biomarker to regulate or predict the progress of disc degeneration.

Platelet-derived extracellular vesicles ameliorate intervertebral disc degeneration by alleviating mitochondrial dysfunction

Mitochondrial dysfunction causes the production of reactive oxygen species (ROS) and oxidative damage, and oxidative stress and inflammation are considered key factors causing intervertebral disc degeneration (IVDD). Thus, restoring the mitochondrial dysfunction is an attractive strategy for treating IVDD. Platelet-derived extracellular vesicles (PEVs) are nanoparticles that target inflammation. Moreover, the vesicles produced by platelets (PLTs) have considerable anti-inflammatory effects. We investigate the use of PEVs as a therapeutic strategy for IVDD in this study. We extract PEVs and evaluate their properties; test their effects on H2O2-induced oxidative damage of nucleus pulposus (NP) cells; verify the role of PEVs in repairing H2O2-induced cellular mitochondrial dysfunction; and demonstrate the therapeutic effects of PEVs in a rat IVDD model. The results confirm that PEVs can restore impaired mitochondrial function, reduce oxidative stress, and restore cell metabolism by regulating the sirtuin 1 (SIRT1)-peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α)-mitochondrial transcription factor A (TFAM) pathway; in rat models, PEVs retard the progression of IVDD. Our results demonstrate that the injection of PEVs can be a promising strategy for treating patients with IVDD.

Maltol ameliorates intervertebral disc degeneration through inhibiting PI3K/AKT/NF-κB pathway and regulating NLRP3 inflammasome-mediated pyroptosis

OBJECTIVES

As one of the major causes of low back pain, intervertebral disc degeneration (IDD) has caused a huge problem for humans. Increasing evidence indicates that NLRP3 inflammasome-mediated pyroptosis of NP cells displays an important role in the progression of IDD. Maltol (MA) is a flavoring agent extracted from red ginseng. Due to its anti-inflammatory and antioxidant effects, MA has been widely considered by researchers. Therefore, we hypothesized that MA may be a potential IVD protective agent by regulating NP cells and their surrounding microenvironment.

METHODS

In vitro, qRT-PCR, and Western blot were used to explore the effect of MA on the transcription and protein expression of the anabolic protein (ADAMTS5, MMP3, MMP9) catabolic protein (Aggrecan), and pro-inflammatory factor (iNOS COX-2). Next, the effects of MA on PI3K/AKT/NF-κB pathway and pyroptosis pathway were analyzed by Western blot and immunofluorescence. Molecular docking was used to investigate the relationship between PI3K and MA. Moreover, ELISA was also used to detect the effects of MA on inflammatory factors (TNF-α, PGE2, IL-1β, and IL-18). In vivo, the effects of MA on the vertebral structure of IDD mice were studied by HE and SO staining and the effects of MA on ECM and PI3K/AKT/NF-κB and pyroptosis pathway of IDD mice were studied by immunohistochemical staining.

RESULTS

MA can ameliorate intervertebral disc degeneration in vivo and in vitro. Specifically, the molecular docking results showed that the binding degree of MA and PI3K was significant. Second, in vitro studies showed that MA inhibited the degradation of ECM and inflammatory response by inhibiting the PI3K/AKT/NF-κB pathway and the pyroptosis mediated by NLRP3 inflammasome, which increased the expression of anabolic proteins, decreased the expression of catabolic proteins, and decreased the secretion of inflammatory mediators such as IL-18 and IL-1β. In addition, according to the study results of the mouse lumbar instability model, MA also improved the tissue disorder and degradation of the intervertebral disc, reduced the loss of proteoglycan and glycosaminoglycan, and inhibited intervertebral disc inflammation, indicating that MA has a protective effect on the intervertebral disc to intervertebral disc in mice.

CONCLUSIONS

Our results suggest that MA slowed IDD development through the PI3K/AKT/NF-κB signaling pathway and NLRP3 inflammasome-mediated pyroptosis, indicating that MA appeared to be a viable medication for IDD treatment.

Red Light-Mediated Photoredox Catalysis Triggers Nitric Oxide Release for Treatment of Cutibacterium Acne Induced Intervertebral Disc Degeneration

Intervertebral disc degeneration (IVDD) has been known as a highly prevalent and disabling disease, which is one of the main causes of low back pain and disability. Unfortunately, there is no effective cure to treat this formidable disease, and surgical interventions are typically applied. Herein, we report that the local administration of nitric oxide (NO)-releasing micellar nanoparticles can efficiently treat IVDD associated with Modic changes in a rat model established by infection with Cutibacterium acnes (C. acnes). By covalent incorporation of palladium(II) meso-tetraphenyltetrabenzoporphyrin photocatalyst and coumarin-based NO donors into the core of micellar nanoparticles, we demonstrate that the activation of the UV-absorbing coumarin-based NO donors can be achieved under red light irradiation via photoredox catalysis, although it remains a great challenge to implement photoredox catalysis reactions in biological conditions due to the complex microenvironments. Notably, the local delivery of NO can not only efficiently eradicate C. acnes pathogens but also inhibit the inflammatory response and osteoclast differentiation in the intervertebral disc tissues, exerting antibacterial, anti-inflammatory, and antiosteoclastogenesis effects. This work provides a feasible means to efficiently treat IVDD by the local administration of NO signaling molecules without resorting to a surgical approach.

Glis1 and oxaloacetate in nucleus pulposus stromal cell somatic reprogramming and survival

Regenerative medicine aims to repair degenerate tissue through cell refurbishment with minimally invasive procedures. Adipose tissue (FAT)-derived stem or stromal cells are a convenient autologous choice for many regenerative cell therapy approaches. The intervertebral disc (IVD) is a suitable target. Comprised of an inner nucleus pulposus (NP) and an outer annulus fibrosus (AF), the degeneration of the IVD through trauma or aging presents a substantial socio-economic burden worldwide. The avascular nature of the mature NP forces cells to reside in a unique environment with increased lactate levels, conditions that pose a challenge to cell-based therapies. We assessed adipose and IVD tissue-derived stromal cells through in vitro transcriptome analysis in 2D and 3D culture and suggested that the transcription factor Glis1 and metabolite oxaloacetic acid (OAA) could provide NP cells with survival tools for the harsh niche conditions in the IVD.

Nutritional deficiency induces nucleus pulposus cell apoptosis via the ATF4-PKM2-AKT signal axis

Background

The intervertebral disc is the largest avascular tissue in the human body. The nucleus pulposus (NP) consumes glucose and oxygen to generate energy to maintain cellular metabolism via nutrients that diffuse from the cartilage endplate. The microenvironment in the intervertebral disc becomes nutritionally deficient during degeneration, and nutritional deficiency has been shown to inhibit the viability and proliferation of NP cells.

Methods

To investigate the molecular mechanism by which nutritional deficiency reduces viability and decreases proliferation, we created an in vitro model by using decreasing serum concentration percentages.

Results

In this study, we found that nutritional deficiency reduced NP cell viability and increased cell apoptosis and that the upregulation of ATF4 expression and the downregulation of PKM2 expression were involved in this process. Moreover, we found that PKM2 inhibition can reduce the cell apoptosis induced by ATF4 silence under nutritional deficiency.

Conclusion

Our findings revealed that PKM2 inhibition reduces the cell apoptosis induced by ATF4 silence under nutritional deficiency by inhibiting AKT phosphate. Revealing the function and mechanism of NP cell development under nutritional deficiency will provide new insights into the etiology, diagnosis, and treatment of intervertebral disc and related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05853-1.

Development of a Computational Model of the Mechanical Behavior of the L4-L5 Lumbar Spine: Application to Disc Degeneration

Degenerative changes in the lumbar spine significantly reduce the quality of life of people. In order to fully understand the biomechanics of the affected spine, it is crucial to consider the biomechanical alterations caused by degeneration of the intervertebral disc (IVD). Therefore, this study is aimed at the development of a discrete element model of the mechanical behavior of the L4-L5 spinal motion segment, which covers all the degeneration grades from healthy IVD to its severe degeneration, and numerical study of the influence of the IVD degeneration on stress state and biomechanics of the spine. In order to analyze the effects of IVD degeneration on spine biomechanics, we simulated physiological loading conditions using compressive forces. The results of modeling showed that at the initial stages of degenerative changes, an increase in the amplitude and area of maximum compressive stresses in the disc is observed. At the late stages of disc degradation, a decrease in the value of intradiscal pressure and a shift in the maximum compressive stresses in the dorsal direction is observed. Such an influence of the degradation of the geometric and mechanical parameters of the tissues of the disc leads to the effect of bulging, which in turn leads to the formation of an intervertebral hernia.