Pingyangmycin-induced in vivo lumbar disc degeneration model of rhesus monkeys

Establishment of intervertebral disc degeneration models; A review of the currently used models

One of the frequent causes of low back pain is intervertebral disc degeneration (IDD), which is followed by discogenic pain. Some significant risk factors that have been linked to the onset and progression of IDD include age, mechanical imbalance, changes in nutrition and inflammation. According to recent studies, five types of animal models are established for producing IDD: the spontaneous models, the puncture models, the biomechanical models, the chemical models and the hybrid models. These models are crucial in studying and understanding IDD's natural history and identifying potential treatment targets for IDD. In our study, we'll talk about the technical aspects of these models, the time between model establishment and the apparition of observable degradation, and their potential in various research. Each animal model should be compared to the human natural IDD pathogenesis to guide future research efforts in this area. By improving knowledge and appropriate application of various animal models, we seek to raise awareness of this illness and further translational research.

A Chitosan Scaffold Supports the Enhanced and Prolonged Differentiation of HiPSCs into Nucleus Pulposus-like Cells

Intervertebral disc degeneration (IDD) is a progressive condition and stands as one of the primary causes of low back pain. Cell therapy that uses nucleus pulposus (NP)-like cells derived from human induced pluripotent stem cells (hiPSCs) holds great promise as a treatment for IDD. However, the conventional two-dimensional (2D) monolayer cultures oversimplify cell-cell interactions, leading to suboptimal differentiation efficiency and potential loss of phenotype. While three-dimensional (3D) culture systems like Matrigel improve hiPSC differentiation efficiency, they are limited by animal-derived materials for translation, poorly defined composition, short-term degradation, and high cost. In this study, we introduce a new 3D scaffold fabricated using medical-grade chitosan with a high degree of deacetylation. The scaffold features a highly interconnected porous structure, near-neutral surface charge, and exceptional degradation stability, benefiting iPSC adhesion and proliferation. This scaffold remarkably enhances the differentiation efficiency and allows uninterrupted differentiation for up to 25 days without subculturing. Notably, cells differentiated on the chitosan scaffold exhibited increased cell survival rates and upregulated gene expression associated with extracellular matrix secretion under a chemically defined condition mimicking the challenging microenvironment of intervertebral discs. These characteristics qualify the chitosan scaffold-cell construct for direct implantation, serving as both a structural support and a cellular source for enhanced stem cell therapy for IDD.

Shared and Compartment-Specific Processes in Nucleus Pulposus and Annulus Fibrosus During Intervertebral Disc Degeneration

Elucidating how cell populations promote onset and progression of intervertebral disc degeneration (IDD) has the potential to enable more precise therapeutic targeting of cells and mechanisms. Single-cell RNA-sequencing (scRNA-seq) is performed on surgically separated annulus fibrosus (AF) (19,978; 26,983 cells) and nucleus pulposus (NP) (20,884; 24,489 cells) from healthy and diseased human intervertebral discs (IVD). In both tissue types, depletion of cell subsets involved in maintenance of healthy IVD is observed, specifically the immature cell subsets - fibroblast progenitors and stem cells - indicative of an impairment of normal tissue self-renewal. Tissue-specific changes are also identified. In NP, several fibrotic populations are increased in degenerated IVD, indicating tissue-remodeling. In degenerated AF, a novel disease-associated subset is identified, which expresses disease-promoting genes. It is associated with pathogenic biological processes and the main gene regulatory networks include thrombospondin signaling and FOXO1 transcription factor. In NP and AF cells thrombospondin protein promoted expression of genes associated with TGFβ/fibrosis signaling, angiogenesis, and nervous system development. The data reveal new insights of both shared and tissue-specific changes in specific cell populations in AF and NP during IVD degeneration. These identified mechanisms and molecules are novel and more precise targets for IDD prevention and treatment.

Parathyroid hormone treatment partially reverses endplate remodeling and attenuates low back pain in animal models of spine degeneration

Low back pain (LBP) is one of the most prevalent diseases affecting quality of life, with no disease-modifying therapy. During aging and spinal degeneration, the balance between the normal endplate (EP) bilayers of cartilage and bone shifts to more bone. The aged/degenerated bony EP has increased porosity because of osteoclastic remodeling activity and may be a source of LBP due to aberrant sensory innervation within the pores. We used two mouse models of spinal degeneration to show that parathyroid hormone (PTH) treatment induced osteogenesis and angiogenesis and reduced the porosity of bony EPs. PTH increased the cartilaginous volume and improved the mechanical properties of EPs, which was accompanied by a reduction of the inflammatory factors cyclooxygenase-2 and prostaglandin E2. PTH treatment furthermore partially reversed the innervation of porous EPs and reversed LBP-related behaviors. Conditional knockout of PTH 1 receptors in the nucleus pulposus (NP) did not abolish the treatment effects of PTH, suggesting that the NP is not the primary source of LBP in our mouse models. Last, we showed that aged rhesus macaques with spontaneous spinal degeneration also had decreased EP porosity and sensory innervation when treated with PTH, demonstrating a similar mechanism of PTH action on EP sclerosis between mice and macaques. In summary, our results suggest that PTH treatment could partially reverse EP restructuring during spinal regeneration and support further investigation into this potentially disease-modifying treatment strategy for LBP.

Multifunctional injectable hydrogels with controlled delivery of bioactive factors for efficient repair of intervertebral disc degeneration

Millions of people worldwide suffer from intervertebral disc degeneration (IVDD), which imposes a significant socioeconomic burden on society. There is an urgent clinical demand for more effective treatments for IVDD because conventional treatments can only alleviate the symptoms rather than preventing the progression of IVDD. Hydrogels, a class of elastic biomaterials with good biocompatibility, are promising candidates for intervertebral disc repair and regeneration. In recent years, various hydrogels have been investigated in vitro and in vivo for the repair of intervertebral discs, some of which are ready for clinical testing. This review summarizes the latest findings and developments in using bioactive factors-released bioactive injectable hydrogels for the repair and regeneration of intervertebral discs. It focuses on the analysis and summary of the use of multifunctional injectable hydrogels to delivery bioactive factors (cells, exosomes, growth factors, genes, drugs) for disc regeneration, providing guidance for future study. Finally, we discussed and analyzed the optimal timing for the application of controlled-release hydrogels in the treatment of IVDD to meet the high standards required for intervertebral disc regeneration and precision medicine.

Constructing intervertebral disc degeneration animal model: A review of current models

Low back pain is one of the top disorders that leads to disability and affects disability-adjusted life years (DALY) globally. Intervertebral disc degeneration (IDD) and subsequent discogenic pain composed major causes of low back pain. Recent studies have identified several important risk factors contributing to IDD's development, such as inflammation, mechanical imbalance, and aging. Based on these etiology findings, three categories of animal models for inducing IDD are developed: the damage-induced model, the mechanical model, and the spontaneous model. These models are essential measures in studying the natural history of IDD and finding the possible therapeutic target against IDD. In this review, we will discuss the technical details of these models, the duration between model establishment, the occurrence of observable degeneration, and the potential in different study ranges. In promoting future research for IDD, each animal model should examine its concordance with natural IDD pathogenesis in humans. We hope this review can enhance the understanding and proper use of multiple animal models, which may attract more attention to this disease and contribute to translation research.

Preclinical in vivo animal models of intervertebral disc degeneration. Part 1: A systematic review

Intervertebral disc degeneration (IVDD), a widely recognized cause of lower back pain, is the leading cause of disability worldwide. A myriad of preclinical in vivo animal models of IVDD have been described in the literature. There is a need for critical evaluation of these models to better inform researchers and clinicians to optimize study design and ultimately, enhance experimental outcomes. The purpose of this study was to conduct an extensive systematic literature review to report the variability of animal species, IVDD induction method, and experimental timepoints and endpoints used in in vivo IVDD preclinical research. A systematic literature review of peer-reviewed manuscripts featured on PubMed and EMBASE databases was conducted in accordance with PRISMA guidelines. Studies were included if they reported an in vivo animal model of IVDD and included details of the species used, how disc degeneration was induced, and the experimental endpoints used for analysis. Two-hundred and fifty-nine (259) studies were reviewed. The most common species, IVDD induction method and experimental endpoint used was rodents(140/259, 54.05%), surgery (168/259, 64.86%) and histology (217/259, 83.78%), respectively. Experimental timepoint varied greatly between studies, ranging from 1 week (dog and rodent models), to >104 weeks in dog, horse, monkey, rabbit, and sheep models. The two most common timepoints used across all species were 4 weeks (49 manuscripts) and 12 weeks (44 manuscripts). A comprehensive discussion of the species, methods of IVDD induction and experimental endpoints is presented. There was great variability across all categories: animal species, method of IVDD induction, timepoints and experimental endpoints. While no animal model can replicate the human scenario, the most appropriate model should be selected in line with the study objectives to optimize experimental design, outcomes and improve comparisons between studies.

Oxidative Stress and Intervertebral Disc Degeneration: Pathophysiology, Signaling Pathway, and Therapy

Intervertebral disc degeneration (IDD), characterized as decreased proteoglycan content, ossification of endplate, and decreased intervertebral height, is one of the major reasons of low back pain, which seriously affects the quality of life and also brings heavy economic burden. However, the mechanisms leading to IDD and its therapeutic targets have not been fully elucidated. Oxidative stress refers to the imbalance between oxidation and antioxidant systems, between too many products of reactive oxygen species (ROS) and the insufficient scavenging function. Excessive ROS can damage cell lipids, nucleic acids and proteins, which has been proved to be related to the development of a variety of diseases. In recent years, an increasing number of studies have reported that oxidative stress is involved in the pathological process of IDD. Excessive ROS can accelerate the IDD process via inducing the pathological activities, such as inflammation, apoptosis, and senescence. In this review, we focused on pathophysiology and molecular mechanisms of oxidative stress-induced IDD. Moreover, the present review also summarized the possible ideas for the future therapy strategies of oxidative stress-related IDD.

Species variation in the cartilaginous endplate of the lumbar intervertebral disc

Backgrounds

Cartilaginous endplate (CEP) plays an essential role in intervertebral disc (IVD) health and disease. The aim was to compare the CEP structure of lumbar IVD and to reveal the detailed pattern of integration between the CEP and bony endplate (BEP) from different species.

Methods

A total of 34 IVDs (5 human, 5 goat, 8 pig, 8 rabbit, and 8 rat IVDs) were collected, fixed and midsagittally cut; in each IVD, one‐half was used for histological staining to observe the CEP morphology, and the other half was used for scanning electron microscopy (SEM) analysis to measure the diameters and distributions of collagen fibers in the central and peripheral CEP areas and to observe the pattern of CEP‐BEP integration from different species.

Results

The human, pig, goat, and rabbit IVDs had the typical BEP‐CEP structure, but the rat CEP was directly connected with the growth plate. Human CEP was the thickest (896.95 ± 87.71 μm) among these species, followed by pig, goat, rat, and rabbit CEPs. Additionally, the mean cellular density of the rabbit CEP was the highest, which was 930 ± 202 per mm², followed by the rat, goat, pig, and human CEPs. In all the species, the collagen fiber diameter in the peripheral area was much bigger than that in the central area. The collagen fiber diameters of CEP from the human, pig, goat, and rat were distributed between 35 nm and 65 nm. The BEP and CEP were connected by the collagen from the CEP, aggregating into bundles or cross links with each other to form a network, and anchored to BEP.

Conclusions

Significant differences in the thickness, cellular density, and collagen characterization of CEPs from different species were demonstrated; the integration of BEP‐CEP in humans, pigs, goats, and rabbits was mainly achieved by the collagen bundles anchoring system, while the typical BEP‐CEP interface did not exist in rats.

Single Impact Injury of Vertebral Endplates Without Structural Disruption, Initiates Disc Degeneration Through Piezo1 Mediated Inflammation and Metabolism Dysfunction

STUDY DESIGN

In vitro experimental study.

OBJECTIVE

To establish an axial impact injury model of intervertebral disc (IVD) and to investigate if a single impact injury without endplate structural disruption could initiate intervertebral disc degeneration (IDD), and what is the roles of Piezo1 in this process.

SUMMARY OF BACKGROUND DATA

Although IDD process has been confirmed to be associated with structural failures such as endplate fractures, whether a single impact injury of the endplates without structural disruption could initiate IDD remains controversial. Previous studies reported that Piezo1 mediated inflammation participated in the progression of IDD induced by mechanical stretch; however, the roles of Piezo1 in IVD impact injury remain unknown.

METHODS

Rats spinal segments were randomly assigned into Control, Low, and High Impact groups, which were subjected to pure axial impact loading using a custom-made apparatus, and cultured for 14 days. The degenerative process was investigated by using histomorphology, real-time Polymerase Chain Reaction(PCR), western-blot, immunofluorescence, and energy metabolism of IVD cell. The effects of Piezo1 were investigated by using siRNA transfection, real-time PCR, western-blot, and immunofluorescence.

RESULTS

The discs in both of the impact groups presented degenerative changes after 14 days, which showed significant up-regulation of Piezo1, NLRP3 inflammasome, the catabolic (MMP-9, MMP-13), and pro-inflammatory gene (IL-1β) expression than that of the control group (P < 0.05), accompanied by significantly increased release of ATP, lactate, nitric oxide (NO), and glucose consumption of IVD cells at first 7 days. Silencing Piezo1 reduced the activation of NLRP3 inflammasome and IL-1β expression in the nucleus pulposus induced by impact injury.

CONCLUSION

It demonstrated that not only fracture of the endplate but also a single impact injury without structural impairment could also initiate IDD, which might be mediated by activation of Piezo1 induced inflammation and abnormal energy metabolism of IVD cells.Level of Evidence: N/A.

Single-Cell RNA-Seq Analysis Reveals Macrophage Involved in the Progression of Human Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) has been considered as the primary pathological mechanism that underlies low back pain. Understanding the molecular mechanisms underlying human IDD is imperative for making strategies to treat IDD-related diseases. Herein, we report the molecular programs, lineage progression patterns, and paths of cellular communications during the progression of IDD using single-cell RNA sequencing (scRNA-seq) on nucleus pulposus (NP) cells from patients with different grades of IDD undergoing discectomy. New subtypes of cells and cell-type-specific gene signatures of the metabolic homeostatic NP cells (Met NPC), adhesive NP cells (Adh NPC), inflammatory response NP cells (IR NPC), endoplasmic reticulum stress NP cells (ERS NPC), fibrocartilaginous NP cells (Fc NPC), and CD70 and CD82+ progenitor NP cells (Pro NPC) were identified. In the late stage of IDD, the IR NPC and Fc NPC account for a large proportion of NPC. Importantly, immune cells including macrophages, T cells, myeloid progenitors, and neutrophils were also identified, and further analysis showed that significant intercellular interaction between macrophages and Pro NPC occurred via MIF (macrophage migration inhibitory factor) and NF-kB signaling pathways during the progression of IDD. In addition, dynamic polarization of macrophage M1 and M2 cell subtypes was found in the progression of IDD, and gene set functional enrichment analysis suggested a significant role of the macrophage polarization in regulating cell metabolism, especially the Pro NPC. Finally, we found that the NP cells in the late degenerative stage were mainly composed of the cell types related to inflammatory and endoplasmic reticulum (ER) response, and fibrocartilaginous activity. Our results provided new insights into the identification of NP cell populations at single-cell resolution and at the relatively whole-transcriptome scale, accompanied by cellular communications between immune cells and NP cells, and discriminative markers in relation to specific cell subsets. These new findings present clues for effective and functional manipulation of human IDD-related bioremediation and healthcare.

Cationic Polymer Brush-Modified Carbon Nanotube-Meditated eRNA LINC02569 Silencing Attenuates Nucleus Pulposus Degeneration by Blocking NF-κB Signaling Pathway and Alleviate Cell Senescence

Enhancer RNAs (eRNAs) are noncoding RNAs that synthesized at active enhancers. eRNAs have important regulatory characteristics and appear to be significant for maintenance of cell identity and information processing. Series of functional eRNAs have been identified as potential therapeutic targets for multiple diseases. Nevertheless, the role of eRNAs on intervertebral disc degeneration (IDD) is still unknown yet. Herein, we utilized the nucleus pulposus samples of patients and identified a key eRNA (LINC02569) with the Arraystar eRNA Microarray. LINC02569 mostly locates in nucleus and plays an important role in the progress of IDD by activating nuclear factor kappa-B (NF-κB) signaling pathway. We used a cationic polymer brush coated carbon nanotube (oCNT-pb)-based siRNA delivery platform that we previously designed, to transport LINC02569 siRNA (si-02569) to nucleus pulposus cells. The siRNA loaded oCNT-pb accumulated in nucleus pulposus cells with lower toxicity and higher transfection efficiency, compared with the traditional siRNA delivery system. Moreover, the results showed that the delivery of si-02569 significantly alleviated the inflammatory response in the nucleus pulposus cells via inhibiting P65 phosphorylation and preventing its transfer into the nucleus, and meanwhile alleviated cell senescence by decreasing the expression of P21. Altogether, our results highlight that eRNA (LINC02569) plays important role in the progression of IDD and could be a potential therapeutic target for alleviation of IDD.

Evaluation of Tissue Engineering Approaches for Intervertebral Disc Regeneration in Relevant Animal Models

Translation of tissue engineering strategies for the regeneration of intervertebral disc (IVD) requires a strong understanding of pathophysiology through the relevant animal model. There is no relevant animal model due to differences in disc anatomy, cellular composition, extracellular matrix components, disc physiology, and mechanical strength from humans. However, available animal models if used correctly could provide clinically relevant information for the translation into humans. In this review, we have investigated different types of strategies for the development of clinically relevant animal models to study biomaterials, cells, biomolecular or their combination in developing tissue engineering-based treatment strategies. Tissue engineering strategies that utilize various animal models for IVD regeneration are summarized and outcomes have been discussed. The understanding of animal models for the validation of regenerative approaches is employed to understand and treat the pathophysiology of degenerative disc disease (DDD) before proceeding for human trials. These animal models play an important role in building a therapeutic regime for IVD tissue regeneration, which can serve as a platform for clinical applications.

The Optimal Timing of Hydrogel Injection for Treatment of Intervertebral Disc Degeneration: Quantitative Analysis Based on T1ρ MR Imaging

STUDY DESIGN

Animal experimental study.

OBJECTIVE

The aim of this study was to investigate the optimal time of hydrogel injection for regenerating intervertebral disc degeneration (IDD) based on T1ρ magnetic resonance imaging (MRI).

SUMMARY OF BACKGROUND DATA

Currently, different approaches are being pursued to regenerate the IDD. However, the optimal timing for the regenerative intervention is unclear.

METHODS

The slowly, progressive IDD models were established in 18 rhesus monkeys. On the basis of the MR T1ρ values of the discs, the rhesus monkeys were divided into severe (T1ρ values: <81 ms), moderate (T1ρ values: 81∼95 ms), and mild (T1ρ values: 96∼110 ms) degeneration groups. Biocompatible hydrogel was injected into the central part of the nucleus pulposus of the discs under fluoroscopic guidance. Treatment effects were investigated using radiography, T1ρ MRI, and histology until 12 months postoperatively.

RESULTS

After injection, the T1ρ values of all the discs increased significantly at 1 month postoperatively, and then remained at approximately 110 ms in the mild and moderate groups during the whole observation period, with no significant difference compared to the values at 1 month (P > 0.05). However, in the severe group, the T1ρ values decreased significantly after 1 month and leveled at approximately 70 ms after 6 months, with significant difference compared to the values at 1 month (P < 0.05). In the mild and moderate groups, there were no significant differences between preoperative histological scores and those at 12 months (P > 0.05). However, the histological score in the severe group at 12 months was significantly higher than the preoperative scores (P < 0.05).

CONCLUSION

This study suggested that the moderate degenerative stage of IDD (T1ρ values from 95 to 80 ms) could be the optimal time for hydrogel injection aimed at the regenerative intervention, based on T1ρ-MR imaging technique and quantitative analysis.

LEVEL OF EVIDENCE

N/A.

Animal models of regenerative medicine for biological treatment approaches of degenerative disc diseases

Degenerative disc disease (DDD) is a painful, chronic and progressive disease, which is characterized by inflammation, structural and biological deterioration of the intervertebral disc (IVD) tissues. DDD is specified as cell-, age-, and genetic-dependent degenerative process that can be accelerated by environmental factors. It is one of the major causes of chronic back pain and disability affecting millions of people globally. Current treatment options, such as physical rehabilitation, pain management, and surgical intervention, can provide only temporary pain relief. Different animal models have been used to study the process of IVD degeneration and develop therapeutic options that may restore the structure and function of degenerative discs. Several research works have depicted considerable progress in understanding the biological basis of disc degeneration and the therapeutic potentials of cell transplantation, gene therapy, applications of supporting biomaterials and bioactive factors, or a combination thereof. Since animal models play increasingly significant roles in treatment approaches of DDD, we conducted an electronic database search on Medline through June 2020 to identify, compare, and discuss publications regarding biological therapeutic approaches of DDD that based on intradiscal treatment strategies. We provide an up-to-date overview of biological treatment strategies in animal models including mouse, rat, rabbit, porcine, bovine, ovine, caprine, canine, and primate models. Although no animal model could profoundly reproduce the clinical conditions in humans; animal models have played important roles in specifying our knowledge about the pathophysiology of DDD. They are crucial for developing new therapy approaches for clinical applications.

Cervical disc width index is a reliable parameter and consistent in young growing Dutch Warmblood horses

Intervertebral disc disease, as well as the associated alteration of the radiographic intervertebral disc space width, has been reported in horses. Disc height index (DHI) has proven to be an accurate and objective parameter in other species but data related to this parameter are lacking in horses. Therefore, the aims of this retrospective longitudinal diagnostic accuracy study were (a) to evaluate the reliability of measurements within and between observers of the equine Disc Width Index (EDWI) as a parameter for radiographic equine cervical intervertebral disc space width, and (b) to evaluate the sequential development of the EDWI over time. For this, EDWI from all intervertebral disc spaces between second cervical (C) to first thoracic (Th) vertebrae were obtained in a group of 39 Dutch Warmblood horses at 1, 5, and 18 months of age, by one European College of Veterinary Diagnostic Imaging (ECVDI) board-certified veterinary radiologist (S.V.) and two veterinary students. Bland-Altmann plots and intraclass Correlation Coefficient revealed a good intra- and interobserver agreement. A linear mixed-effect model did reveal that mean EDWI increases significantly toward the caudal cervical spine, but did not differ significantly for a certain location over time or between sexes. Spearman's rank test did show a significant correlation between the vertebral alignment angle induced by different head-neck positions and a normalized EDWI (ρ = 0.33, P < .0001). Student's t-test revealed that the presence of C6-C7 transposition of the transverse processes did not influence EDWI significantly. It was concluded that EDWI represents a reliable parameter for equine cervical radiographic intervertebral disc space width. Practical implementation of EDWI warrants monitoring in a group of adult horses while maintaining a standardized head-neck position.

Bioinformatics analysis integrating metabolomics of m6A RNA microarray in intervertebral disc degeneration

Aim: To explore the potential functions and mechanism of N⁶.methyladenosine (m⁶A) abnormality of RNAs in nucleus pulposus from the intervertebral disc degeneration (IDD). Materials & methods: We performed rat model, m⁶A epitranscriptomic microarray, bioinformatics analysis and metabolomics. Results: In IDD, most of the differentially methylated RNAs showed a significant demethylation situation. The competing endogenous RNA network LOC102555094/miR-431/GSK-3β combining downstream Wnt pathway were identified in bioinformatics analysis. For metabolomics, activation of Wnt pathway led to reprogramming of glucose metabolism and enzyme activation of PKM2. Finally, quantitative real-time PCR and methylated RNA immunoprecipitation coupled with quantitative real-time PCR revealed the positive correlation between demethylation of LOC102555094 and expression of both FTO and ZFP217. Conclusion: LOC102555094 might be demethylated by ZFP217, activating FTO and LOC102555094/miR-431/GSK-3β/Wnt played a crucial role in IDD.

Changes of the end plate cartilage are associated with intervertebral disc degeneration: A quantitative magnetic resonance imaging study in rhesus monkeys and humans

Background

The end plate plays an important role in intervertebral disc degeneration progression. The aim of the study was to examine the compositional and structural changes of the end plate with age and to investigate the correlation between end plate and disc degeneration by T1ρ and T2 map magnetic resonance imaging.

Methods

There were 12 young monkeys (6-7 years old), 20 aged monkeys (14-17 years old) and 12 human participants (30-50 years old) in this study. T1ρ or T2 map values of the nucleus pulposus and end plate cartilage were analyzed according to Pfirrmann grades and age. Afterwards, micro computed tomography and histological analysis were used to confirm the end plate changes in monkeys. Pearson’s correlation was performed to investigate the relationship between end plate and disc degeneration.

Results

In monkeys, T1ρ (r=-0.794, P<0.001) and T2 map values (r=-0.8, P<0.001) of the nucleus pulposus were negatively associated with Pfirrmann grades. Moreover, the T2 map was more suitable than T1ρ for the evaluation of end plate degeneration. Age was an important influence factor of end plate and disc degeneration, which was confirmed by microcomputed tomography, Safranin O/fast green staining, and collagen II staining. The T2 map value of lower end plate degeneration positively correlated with that of the intervertebral discs in monkeys (R²=0.3133, P<0.001) and humans (R²=0.2092, P<0.001).

Conclusion

This study suggests that the compositional and structural changes of the end plate can be quantitatively evaluated by T2 map. Furthermore, cartilage end plate degeneration is associated with disc degeneration during ageing.

The translational potential of this article

A better understanding of how the cartilage end plate affects disc degeneration is needed, which may propose a new clinical application using T2 map to evaluate end plate degeneration.

Contribution of the endplates to disc degeneration

Purpose of review

The endplates form the interface between the rigid vertebral bodies and compliant intervertebral discs. Proper endplate function involves a balance between conflicting biomechanical and nutritional demands. This review summarizes recent data that highlight the importance of proper endplate function and the relationships between endplate dysfunction, adjacent disc degeneration, and axial low back pain.

Recent findings

Changes to endplate morphology and composition that impair its permeability associate with disc degeneration. Endplate damage also associates with disc degeneration, and the progression of degeneration may be accelerated and the chronicity of symptoms heightened when damage coincides with evidence of adjacent bone marrow lesions.

Summary

The endplate plays a key role in the development of disc degeneration and low back pain. Clarification of the mechanisms governing endplate degeneration and developments in clinical imaging that enable precise evaluation of endplate function and dysfunction will distinguish the correlative vs. causative nature of endplate damage and motivate new treatments that target pathologic endplate function.

Biomaterials for intervertebral disc regeneration: Current status and looming challenges

A biomaterial-based strategy is employed to regenerate the degenerated intervertebral disc, which is considered a major generator of neck and back pain. Although encouraging enhancements in the anatomy and kinematics of the degenerative disc have been gained by biomaterials with various formulations in animals, the number of biomaterials tested in humans is rare. At present, most studies that involve the use of newly developed biomaterials focus on regeneration of the degenerative disc, but not pain relief. In this review, we summarise the current state of the art in the field of biomaterial-based regeneration or repair for the nucleus pulposus, annulus fibrosus, and total disc transplantation in animals and humans, and we then provide essential suggestions for the development and clinical translation of biomaterials for disc regeneration. It is important for researchers to consider the commonly neglected issues instead of concentrating solely on biomaterial development and fabrication.

CircularRNA_104670 plays a critical role in intervertebral disc degeneration by functioning as a ceRNA

This study was carried out to explore the roles of circular RNAs (circRNAs) in nucleus pulposus (NP) tissues in intervertebral disc degeneration (IDD). Differentially expressed circRNAs in IDD and normal NP tissues were identified based on the results of microarray analysis. Bioinformatics techniques were employed to predict the direct interactions of selected circRNAs, microRNAs (miR), and mRNAs. CircRNA_104670 was selected as the target circRNA due to its large multiplier expression in IDD tissues. After luciferase reporter and EGFP/RFP reporter assays, we confirmed that circRNA_104670 directly bound to miR-17-3p, while MMP-2 was the direct target of miR-17-3p. The receiver-operating characteristic (ROC) curve showed that circRNA_104670 and miR-17-3p had good diagnostic significance for IDD (AUC _{circRNA_104670} = 0.96; AUC _miRNA-17-3p = 0.91). A significant correlation was detected between the Pfirrmann grade and expression of circRNA_104670 (r = 0.63; p = 0.00) and miR-17-3p (r = −0.62; p = 0.00). Flow-cytometric analysis and the MTT assay showed that interfering with circRNA_104670 using small interfering RNA (siRNA) inhibited NP cell apoptosis (p < 0.01), and this inhibition was reduced by interfering with miR-17-3p. Interfering with circRNA_104670 suppressed MMP-2 expression and increased extracellular matrix (ECM) formation, which were also reduced by interfering with miR-17-3p. Finally, an MRI evaluation showed that circRNA_104670 inhibition mice had a lower IDD grade compared with control mice (p < 0.01), whereas circRNA_104670 and miRNA-17-3p inhibition mice had a higher IDD grade compared with circRNA_104670 inhibition mice (p < 0.05). CircRNA_104670 is highly expressed in the NP tissues of IDD and acts as a ceRNA during NP degradation.

‘RNA sponges’ may provoke lower back pain by soaking up regulatory RNAs that normally protect the protein infrastructure surrounding cells in intervertebral discs. Many people suffer from lower back pain arising from disc degeneration (IDD). A team led by Fei-Zou and Jian-Yuan Jiang at Fudan University, Shanghai, China set out to identify molecular mechanisms that might contribute to IDD. They focused on circular RNAs, non-protein coding RNAs that have been linked to a variety of diseases. The researchers learned that IDD is associated with strongly elevated expression of a circular RNA that acts as an ‘RNA sponge’, binding to and thereby inactivating other RNA molecules. This inactivation ultimately results in the excessive production of an enzyme that can damage the protein matrix that supports cells within spinal discs, potentially setting up the conditions for IDD.

Animal models for disc degeneration-an update

Intervertebral disc degeneration is considered a major cause of back pain that places a heavy burden on society, both because of its effect on the physiology of individuals and its consequences on the world economy. During the past few decades, research findings in the pre-clinical setting have led to a significant increase in the understanding of intervertebral disc degeneration, although many aspects of the disease remain unclear. The goal of this review is to summarize existing animal models for disc degeneration studies and the difficulties that are associated with the use of such models. A firm understanding of the cellular and molecular events that ensue as a result of injuries, as well as environmental factors, could be instrumental in the development of targeted therapies for the treatment of intervertebral disc degeneration.

The effects of intervertebral disc degeneration combined with osteoporosis on vascularization and microarchitecture of the endplate in rhesus monkeys

PURPOSE

To evaluate the influence of osteoporosis on the microarchitecture and vascularization of the endplate in rhesus monkeys with or without intervertebral disc (IVD) degeneration using micro-computerized tomography (micro-CT), and to further analyze the correlation between osteoporosis and IVD degeneration.

METHODS

Twelve rhesus monkeys were randomly divided into the ovariectomy (OVX, n = 6) and the sham group (n = 6). The subchondral bone adjacent to the lumbar IVDs (from L4/5 to L6/7) of each monkey was randomly injected with 4 ml pingyangmycin (PYM) solution (1.5 mg/ml, PYM), or 4 ml phosphate buffered saline (PBS) as vehicle treatment, or exteriorized but not injected anything as control (Cntrl). Degenerative and osteoporotic processes were evaluated at different time points. Micro-CT and histology were performed to analyze microarchitecture, calcification area and vascularization of the endplate.

RESULTS

OVX resulted in significant decrease of bone mineral density (BMD). PYM injection induced progressively IVD degeneration, which was more progressive when combined with OVX. There was a negative correlation between BMD and Pfirrmann grade in the subgroups with PYM injection. The micro-CT analysis showed the combination of osteoporosis and IVD degeneration led to more calcification of endplate than any one thereof. The decrease of vascular volume percent in the endplate of the OVX-PYM subgroup was significantly greater than that in the Sham-PYM subgroup, both of which showed significant less vascularization compared to the other subgroups.

CONCLUSION

In conclusion the osteoporosis could accumulate the calcification and decrease the vascularization in the endplates adjacent to the degenerated IVDs, which subsequently exacerbated degeneration of the degenerated IVDs.