Human Lumbar Discs Research Articles

Three-dimensional fiber patterning in the annulus fibrosus can be derived from vertebral endplate topography.

The annulus fibrosus (AF) of the Intervertebral disc (IVD) is composed of concentric lamellae of helically wound collagen fibers. Understanding the spatial variation of collagen fiber orientations in these lamellae, and the resulting material anisotropy, is crucial to predicting the mechanical behavior of the complete IVD. This study builds on a prior model predicated on path-independent displacement of fiber endpoints during vertebral body growth to predict a complete, three-dimensional annulus fibrosus fiber network from a small number of subject-independent input parameters and vertebral endplate topographies obtained from clinical imaging. To evaluate the model, it was first fit to mid-plane fiber orientations obtained using polarized light microscopy in a population of bovine caudal discs for which computed tomography images vertebral endplates were also available. Additionally, the model was used to predict the trajectories based on human lumbar disc geometries and results were compared to previously reported data. Finally, the model was employed to investigate potential disc-related variations in fiber angle distributions. The model was able to accurately predict experimentally measured fiber distributions in both bovine and human discs using only endplate topography and three input parameters. Critically, the model recapitulated previously observed asymmetry between the inclinations of right- and left-handed fibers in the posterolateral aspect of the human AF. Level to level variation of disc height and aspect ratio in the human lumbar spine was predicted to affect absolute values of fiber inclination, but not this asymmetry. Taken together these results suggest that patient-specific distributions of AF fiber orientation may be readily incorporated into computational models of the spine using only disc geometry and a small number of subject-independent parameters.

ISSLS prize in clinical/bioengineering science 2024: How standing and supine positions influence nutrient transport in human lumbar discs?-A serial post-contrast MRI study evaluating interplay between convection and diffusion.

The intervertebral disc being avascular depends on diffusion and load-based convection for essential nutrient supply and waste removal. There are no reliable methods to simultaneously investigate them in humans under natural loads. For the first time, present study aims to investigate this by strategically employing positional MRI and post-contrast studies in three physiological positions: supine, standing and post-standing recovery. A total of 100 healthy intervertebral discs from 20 volunteers were subjected to a serial post-contrast MR study after injecting 0.3mmol/kg gadodiamide and T1-weighted MR images were obtained at 0, 2, 6, 12 and 24h. At each time interval, images were obtained in three positions, i.e. supine, standing and post-standing recovery supine. The signal intensity values at endplate zone and nucleus pulposus were measured. Enhancement percentages were calculated and analysed comparing three positions. During unloaded supine position, there was slow gradual increase in enhancement reaching peak at 6h. When the subjects assumed standing position, there was immediate loss of enhancement at nucleus pulposus which resulted in reciprocal increase in enhancement at endplate zone (washout phenomenon). Interestingly, when subjects assumed the post-standing recovery position, the nucleus pulposus regained the enhancement and endplate zone showed reciprocal loss (pumping-in phenomenon). For the first time, present study documented acute effects of physiological loading and unloading on nutrition of human discs in vivo. While during rest, solutes diffused gradually into disc, the diurnal short loading and unloading redistribute small solutes by convection. Standing caused rapid solute depletion but promptly regained by assuming resting supine position.

Lipid Peroxidation, Reduced Glutathione, and Glutathione Peroxidase Levels in Intervertebral Discs of Patients with Lumbar Degenerative Disc Disease.

BACKGROUND Either a reduction in antioxidant levels or an accumulation of reactive oxygen species can heighten susceptibility to oxidative damage in disc cells. To date, no research has investigated the levels of lipid peroxidation products (thiobarbituric acid reactive substances [TBARs]), reduced glutathione (GSH), and glutathione peroxidase (GPx) in excised human lumbar disc tissues affected by degenerative disease. Therefore, this study aimed to evaluate lipid peroxidation products in excised disc tissues from patients with degenerative disc disease. MATERIAL AND METHODS Forty-two patients were enrolled. Patients were divided into lumbar disc degeneration (LDD) and nonlumbar disc degeneration (nonLDD) groups according to Pfirrmann classification. Intervertebral discs were obtained from all patients during the operation and were homogenized for analysis. TBARs levels were measured using fluorometry. GSH levels and GPx activity were quantified spectrophotometrically using a kinetic method. RESULTS TBARs levels in excised discs from LDD patients (5.18±4.14) were significantly higher than those from nonLDD patients (2.56±1.23, P=0.008). The levels of TBARs tended to increase with the severity of degeneration according to the Pfirrmann classification. However, these 2 groups showed no significant differences in reduced glutathione levels or glutathione peroxidase activity (P>0.05). Patients with LDD exhibited a worse health-related quality of life, reflected in lower utility and EQ-VAS scores and higher Oswestry disability index scores. CONCLUSIONS There was a notable increase in lipid peroxidation products in the excised intervertebral discs of patients with LDD. This finding suggests that oxidative stress may contribute to the development of disc degeneration.

The Safety and Effectiveness of Orthobiologic Injections for Discogenic Chronic Low Back Pain: A Multicenter Prospective, Crossover, Randomized Controlled Trial with 12 Months Follow-up

BACKGROUND: Chronic low back pain is one of the most common causes of disability, affecting more than 600 million people worldwide with major social and economic costs. Current treatment options include conservative, surgical, and minimally invasive interventional treatment approaches. Novel therapeutic treatment options continue to develop, targeting the biological cascades involved in the degenerative processes to prevent invasive spinal surgical procedures. Both intradiscal platelet-rich plasma (PRP) and bone marrow concentrate (BMC) applications have been introduced as promising regenerative treatment procedures. OBJECTIVES: The primary objective of this study is to assess the safety and effectiveness of an orthobiologic intradiscal injection, PRP or BMC, when compared to control patients. The secondary objectives are to measure: patient satisfaction and incidence of hospitalization, emergency room visit and spine surgery at predetermined follow-up intervals. STUDY DESIGN: A multicenter, prospective, crossover, randomized, controlled trial. SETTING: Comprehensive Spine and Sports Center and participating centers. METHODS: Forty patients were randomized into saline trigger point injection, intradiscal PRP, or BMC. Follow-up was 1, 3, 6, and 12 months posttreatment. Placebo patients were randomized to PRP and BMC injection if < 50% decrease in numeric rating scale (NRS) scores in 3 months, while PRP and BMC patients to the other active group if < 50% decrease in NRS scores in 6 months. RESULTS: Both PRP and BMC demonstrated statistically significant improvement in pain and function. All the placebo patients reported < 50% pain relief and crossed to the active arm. None of the patients had any adverse effects, hospitalization, or surgery up to 12 months posttreatment. LIMITATIONS: The limitations of our study were the small number of patients and open-label nature of the study. CONCLUSION: This is the only human lumbar disc study that evaluates both PRP and BMC in the same study and compares it to placebo. PRP and BMC were found to be superior to placebo in improving pain and function; however, larger randomized clinical trials are needed to answer further questions on the comparative effectiveness of various biologics as well as to identify outcome differences specific to disc pathology. KEY WORDS: Low back pain, disc, mesenchymal stem cells, platelet-rich plasma, biologics, back pain, degenerative disc disease, intradiscal biologics, lumbar spine, low back, regenerative treatment spine, radiculopathy

Cytokine Inhibitors Upregulate Extracellular Matrix Anabolism of Human Intervertebral Discs under Alginate Beads and Alginate-Embedded Explant Cultures.

We investigated the effects of the cytokine inhibitors IL-1 receptor antagonist (IL-1Ra) and soluble tumor necrosis factor receptor-1 (sTNFR1) on the extracellular matrix metabolism of human intervertebral discs (IVDs) and the roles of IL-1β and TNF in the homeostasis of IVD cells. The 1.2% alginate beads and the explants obtained from 35 human lumbar discs were treated with cytokine inhibitors. Extracellular matrix metabolism was evaluated by proteoglycan (PG) and collagen syntheses and IL-1β, TNF, and IL-6 expressions after three days of culture in the presence or absence of IL-1Ra, sTNFR1, and cycloheximide. Simultaneous treatment with IL-1Ra and sTNFR1 stimulated PG and collagen syntheses in the NP and AF cells and explants. The IL-1β concentration was significantly correlated to the relative increase in PG synthesis in AF explants after simultaneous cytokine inhibitor treatment. The relative increase in PG synthesis induced by simultaneous cytokine treatment was significantly higher in an advanced grade of MRI. Expressions of IL-1β and TNF were upregulated by each cytokine inhibitor, and simultaneous treatment suppressed IL-1β and TNF productions. In conclusion, IL-1Ra and sTNFR1 have the potential to increase PG and collagen synthesis in IVDs. IL-1β and TNF have a feedback pathway to maintain optimal expression, resulting in the control of homeostasis in IVD explants.

Bioinspired Intervertebral Disc with Multidirectional Stiffness Prepared via Multimaterial Additive Manufacturing

AbstractDegenerative disc disease (DDD) has become a significant public health issue worldwide. This can result in loss of spinal function affecting patient health and quality of life. Artificial total disc replacement (A‐TDR) is an effective approach for treating symptomatic DDD that compensates for lost functionality and helps patients perform daily activities. However, because current A‐TDR devices lack the unique structure and material characteristics of natural intervertebral discs (IVDs), they fail to replicate the multidirectional stiffness needed to match physiological motions and characterize anisotropic behavior. It is still unclear how the multidirectional stiffness of the disc is affected by structural parameters and material characteristics. Herein, a bioinspired intervertebral disc (BIVD‐L) based on a representative human lumbar segment is developed. The proposed BIVD‐L reproduces the multidirectional stiffness needed for the most common physiological kinematic behaviors. The results demonstrate that the multidirectional stiffness of the BIVD‐L can be regulated by structural and material parameters. The results of this research deepen knowledge of the biomechanical behavior of the human lumbar disc and may provide new inspirations for the design and fabrication of A‐TDR devices for both engineering and functional applications.

Artificial neural network supported design of a lattice-based artificial spinal disc for restoring patient-specific anisotropic behaviors

To tackle the challenge in artificial spinal disc (ASD) design of restoring the mechanics of a natural disc, this study proposes an innovative lattice-based ASD for reproducing a patient-specific anisotropic rotational response, inspired by the design freedom provided by lattice structures. Motivated by the great potential of machine learning to improve computational design processes, a method is proposed for computationally efficient topology optimization using artificial neural networks (ANNs) and a subsequent member sizing for automating the design of patient-specific ASDs. The results reported in this study show a good match between the optimized ASDs’ six rotational stiffnesses with those of both L2-L3 and L4-L5 human lumbar discs. Additionally, the fast convergence rate of the optimization verifies the application of ANNs and the proposed strategy to reduce the design space by formulating the design problem as optimizing the unit-cell distribution in a predefined grid. Therefore, the study demonstrates that a lattice-based ASD is able to reproduce patient-specific anisotropic rotational response and that a machine-learning-based method improves the computational efficiency of an automated design process to produce personalized ASD designs.

Bacteria in human lumbar discs – subclinical infection or contamination? Metabolomic evidence for colonization, multiplication, and cell-cell cross-talk of bacteria

The accumulating evidence associating sub-clinical infection with disc degeneration (DD) and the controversy of contamination versus infection mandates a further understanding of the microbial activity in the disc and host-microbiome interaction. To utilize a novel approach of metabolomics to probe the presence of bacterial metabolites involved in colonization, survival, and replication in human lumbar intervertebral discs (LIVD). An observational case-control study. Nucleus pulposus from the LIVD of three brain-dead voluntary organ donors (MRI normal and classified as controls) and of three patients undergoing surgery for disc degeneration (DD) (cases) were utilized. Untargeted metabolite profiling was carried out in six discs (3-controls and 3-cases) after extraction using methanol: acetonitrile: water (2:2:1) solvent system and acquired through HPLC-MS/MS platform using C18 reversed-phase column. From the total IVD metabolome, microbial metabolites were filtered by mapping against HMDB, ChEBI, SigMol, Siderophore database, ecdmb database, and PaMet databases. The biological functions of the metabolites were then studied by MSEA pipeline from Metaboanalyst, and the enrichment ratio, p-value, and Variably Importance Projection scores of the metabolites were calculated. Degeneration responsive changes in the abundance of the microbial metabolites were calculated based on the peak intensities between the control and cases. Mass spectrometry identified a total of 17601 and 15003 metabolites, respectively, in the control and degenerated discs. Preliminary mapping of the above metabolites against HMDB indicated the multiple sources, and of these, 64 metabolites were of microbial origin, accounting for 1.6% of the total IVD metabolome. Principle Component Analysis and Orthogonal Partial Least Square-Discriminant Analysis (OPLS-DA) showed distinct clustered patterns between control and disc degene`ration, indicating a strong variation in concentration, peak, and spectral values of the 64 metabolites between controls and cases. After the exclusion of metabolites that were also associated with humans, drugs, and food, 39 metabolites specific to bacteria were isolated. Nine were primary metabolites related to bacterial growth and survival, and the remaining 30 were secondary metabolites related to different environmental stress response activities. The three significant pathways (p<.001) which were predominant in the bacterial metabolites were autoinducer-2 biosynthesis, peptidoglycan biosynthesis, and chorismate pathway. In addition, a significant fold change of >1.0 was found for nine metabolites which included (S)-14-Methyilhexadecanoic acid related to P. acnes, 9-OxoODE, and 13-OxoODE related to gut flora, vibriobactin - a siderophore, tuberculosinol and iso-tuberculosinol, virulence factors of M. tuberculosis. There was also upregulation of Autoinducer- 2, an important "Quorum sensing molecule" involved in bacterial cross-talk. We identified several bacterial-specific metabolites participating in bacterial growth, survival, and cross-talk pathways. These were found in both groups but up-regulated in degenerated discs. The presence of Quorum sensing molecules and cell-cell interactions provides firm proof of colonization and growth. These findings indicate that the bacterial presence may not be mere contamination but could be colonization with a possible role in infection-mediated inflammation in DD. Proof of subclinical infection as an initiator of DD and documentation of exact germ and drug sensitivity will change the way millions of patients with non-specific low back pain (NSLBP) are treated across the world.

A fully three-dimensional model of interpenetrating collagen fibrillar networks for intervertebral disc mechanics

In this work, a fully three-dimensional model of the human intervertebral disc is proposed within a purely analytical framework in the final goal to create time and cost-efficient patient-specific models. The constitutive representation considers the deformation-induced damage along with the hydration effects on the regional disc mechanics. Special functions are introduced to generate versatile and anatomically accurate disc geometries taking into account morphology regional variation. The complex interpenetrating collagen fibrillar networks are explicitly introduced in the three-dimensional model considering the regional variation throughout the disc. A quantitative evaluation of the predictive capabilities of a human lumbar disc model shows a good agreement with compression and torsion experiments from the literature both for the overall disc stiffness and for the direct MRI kinematic fields. Model predictions are then performed and critically discussed on axially/torsionally loaded human lumbar discs.

Emerging Issues Questioning the Current Treatment Strategies for Lumbar Disc Herniation.

Lumbar disc herniation is among the common phenotypes of degenerative lumbar spine diseases, significantly affecting patients' quality of life. The practice pattern is diverse. Choosing conservative measures or surgical treatments is still controversial in some areas. For those who have failed conservative treatment, surgery with or without instrumentation is recommended, causing significant expenditures and frustrating complications, that should not be ignored. In the article, we performed a literature review and summarized the evidence by subheadings to unravel the cons of surgical intervention for lumbar disc herniation. There are tetrad critical issues about surgical treatment of lumbar disc herniation, i.e., favorable natural history, insufficient evidence in a recommendation of fusion surgery for patients, metallosis, and implant removal. Firstly, accumulating evidence reveals immune privilege and auto-immunity hallmarks of human lumbar discs within the closed niche. Progenitor cells within human discs further expand the capacity with the endogenous repair. Clinical watchful follow-up studies with repeated diagnostic imaging reveal spontaneous resolution for lumbar disc herniation, even calcified tissues. Secondly, emerging evidence indicates long-term complications of lumbar fusion, such as adjacent segment disease, pseudarthrosis, implant failure, and sagittal spinal imbalance, which get increasing attention. Thirdly, systemic and local reactions (metallosis) for metal instrumentation have been noted with long-term health concerns and toxicity. Fourthly, the indications and timing for spinal implant removal have not reached a consensus. Other challenging issues include postoperative lumbar stiffness. The review provided evidence from a negative perspective for surgeons and patients who attempt to choose surgical treatment. Collectively, the emerging underlying evidence questions the benefits of traditional surgery for patients with lumbar disc herniation. Therefore, the long-term effects of surgery should be closely observed. Surgical decisions should be made prudently for each patient.

Isolation of Brucella abortus biovar 1 from human lumbar disc bulging: a case report of brucellar discitis

BackgroundBrucellosis is an endemic zoonotic disease with rising health and economic concerns in many areas worldwide. Musculoskeletal pains are among the main complications of human brucellosis, which are often difficult to diagnose due to the variability of clinical symptoms. Brucellar discitis is a very disabling problem in some chronic forms of the disease which may lead to serious vertebral and neurological consequences.Case presentationIn this case report, we reported the isolation of Brucella abortus from lumbar disc bulging in a woman who had rheumatoid arthritis and diabetes mellitus as underlying conditions. The patient had several negative brucellosis serological tests and dorsolumbar pains with urinary incontinence over a 2-month period. The diagnosis was confirmed by magnetic resonance imaging (MRI) examination of lumbar spine as well as disc culture. MRI examination was performed without intravenous contrast and revealed the presence of disc bulging, left foraminal narrowing at L5-S1, left foraminal narrowing, anterolisthesis grade II at L4-L5. The diagnosis was also confirmed by isolation of B. abortus biovar 1 from bulging disc culture. The isolate was characterized by AMOS PCR, Bruce-ladder PCR and biotyping, resulting in the identification of B. abortus from L4-L5 and L5-S1 disc bulging regions. The patient was treated with two drugs i.e. doxycycline and rifampin for 3 months. In the follow-up, in addition to improving the patient’s general condition, low-back pain was also significantly reduced.ConclusionsMRI, serology, cultural and molecular test along with patient history are important to make a rapid diagnosis of brucellosis’ discitis, thereby decreasing the delay for the brucellosis treatment. The present report suggests that the infection by Brucella spp. should be fundamentally considered among the causative agents of back pain especially in the endemic areas of Brucella infections.

Prediction of biomechanical responses of human lumbar discs - a stochastic finite element model analysis

Background Accurate biomechanical investigation of human intervertebral discs (IVDs) is difficult because of their complicated structural and material features. Aim To investigate probabilistic distributions of the biomechanical responses of the IVD by considering varying nonlinear structural and material properties using a stochastic finite element (FE) model. Methods A FE model of a L3-4 disc was reconstructed, including the nucleus pulposus (NP), annular matrix and fibers. A Monte Carlo method was used to randomly generate 500 sets of the nonlinear material properties and fiber orientations of the disc that were implemented into the FE model. The FE model was analyzed under seven loading conditions: a 500 N compressive force, a 7.5Nm moment simulating flexion, extension, left-right lateral bending, and left-right axial rotation, respectively. The distributions of the ranges of motion (ROMs), intradiscal pressures (IDP), fiber stresses and matrix strains of the disc were analyzed. Results Under the compressive load, the displacement varied between 0.29 mm and 0.76 mm. Under the 7.5Nm moment, the ROMs varied between 3.0° and 6.0° in primary rotations. The IDPs varied within 0.3 MPa under all the loading conditions. The maximal fiber stress (3.22 ± 0.64 MPa) and matrix strain (0.27 ± 0.12%) were observed under the flexion and extension moments, respectively. Conclusion The IVD biomechanics could be dramatically affected by the structural and material parameters used to construct the FE model. The stochastic FE model that includes the probabilistic distributions of the structural and material parameters provides a useful approach to analyze the statistical ranges of the biomechanical responses of the IVDs.

Analysis of the influence of species, intervertebral disc height and Pfirrmann classification on failure load of an injured disc using a novel disc herniation model

Background ContextAnnular repair devices offer a solution to recurrent disc herniations by closing an annular defect and lowering the risk of reherniation. Given the significant risk of neurologic injury from device failure it is imperative that a reliable preclinical model exists to demonstrate a high load to failure for the disc repair devices. PurposeTo establish a preclinical model for disc herniation and demonstrate how changes in species, intervertebral disc height and Pfirrmann classification impacts failure load on an injured disc. We hypothesized that: (1) The force required for disc herniation would be variable across disc morphologies and species, and (2) for human discs the force to herniation would inversely correlate with the degree of disc degeneration. Study designAnimal and human cadaveric biomechanical model of disc herniation. MethodsWe tested calf lumbar spines, bovine tail segments and human lumbar spines. We first divided individual lumbar or tail segments to include the vertebral bodies and disc. We then hydrated the specimens by placing them in a saline bath overnight. A magnetic resonance images were acquired from human specimens and a Pfirrmann classification was made. A stab incision measuring 25% of the diameter of the disc was then done to each specimen along the posterior intervertebral disc space. Each specimen was placed in custom test fixtures on a servo-hydraulic test frame (MTS, Eden Prarie, MN) such that the superior body was attached to a 10,000 lb load cell and the inferior body was supported on the piston. A compressive ramping load was placed on the specimen in load control at 4 MPa/sec stopping at 75% of the disc height. Load was recorded throughout the test and failure load calculated. Once the test was completed each specimen was sliced through the center of the disc and photos were taken of the cut surface. ResultsFifteen each of calf, human, and bovine tail segments were tested. The failure load varied significantly between specimens (p<.001) with human specimens having the highest average failure load (8154±2049 N). Disc height was higher for lumbar/bovine tail segments as compared to calf specimens (p<.001) with bovine tails having the highest disc height (7.1±1.7 mm). Similarly, human lumbar discs had a cross sectional area that was greater than both bovine tail/calf lumbar spines (p<.001). There was no correlation between disc height and failure load within each individual species (p>.05). Cross sectional area and failure load did not correlate with failure load for human lumbar spine and bovine tails (p>.05) but did correlate with calf spine (r=0.53, p=.04). There was a statistically significant inverse correlation between disc height and Pfirrmann classification for human lumbar spines (r=−0.84, p<.001). There was also a statistically significant inverse relationship between Pfirrmann classification and failure load (r=−0.58, p=.02). ConclusionsWe have established a model for disc herniation and have shown how results of this model vary between species, disc morphology, and Pfirrmann classification. Both hypotheses were accepted: The force required for disc herniation was variable across species, and the force to herniation for human spines was inversely correlated with the degree of disc degeneration. We recommend that models using human intervertebral discs should include data on Pfirrmann classification, while biomechanical models using calf spines should report cross sectional area. Failure loads do not vary based on dimensions for bovine tails. Clinical SignificanceOur analysis of models for disc herniation will allow for quicker, reliable comparisons of failure forces required to induce a disc herniation. Future work with these models may facilitate rapid testing of devices to repair a torn/ruptured annulus.

Level-wise differences in in vivo lateral bending moment are associated with microstructural alterations in bovine caudal intervertebral discs.

Despite its common use as a laboratory model, little is known about the in vivo forces and moments applied to the bovine caudal intervertebral disc. Such aspects are crucial, as intervertebral disc tissue is known to remodel in response to repeated loading. We hypothesized that the magnitude of loading from muscle contraction during a typical lateral bending motion varies between caudal levels and is accompanied by variations in tissue microstructure. This hypothesis was tested by estimating level-wise forces and bending moments using two independent approaches: a dynamic analytical model of the motion and analysis of muscle cross-sections obtained via computed tomography. Microstructure was assessed by measuring the collagen fiber crimp period in the annulus fibrosus, and composition was assessed via quantitative histology. Both the analytical model and muscle cross-sections indicated peak bending moments of over 3 N m and peak compressive force of over 125 N at the c1c2 level, decreasing distally. There was a significant downward trend from proximal to distal in the outer annulus fibrosus collagen crimp period in the anterior and posterior regions only, suggesting remodeling in response to the highest lateral bending moments. There were no observed trends in composition. Our results suggest that although the proximal discs in the bovine tail are subjected to forces and moments from muscle contraction that are comparable (relative to disc size) to those acting on human lumbar discs, the distal discs are not. The resulting pattern of microstructural alterations suggests that level-wise differences should be considered when using bovine discs as a research model.

Systematic identification of lncRNAs and circRNAs-associated ceRNA networks in human lumbar disc degeneration

ABSTRACTLumbar disc degeneration (LDD) is a common cause of low back and neck pain. The molecular mechanisms underlying LDD, however, are unclear. Noncoding RNAs have been reported to participate in human diseases. We investigated a series of public datasets (GSE67566, GSE56081 and GSE63492) and identified 568 mRNAs, 55 microRNAs (miRNAs), 765 long noncoding RNAs (lncRNAs), and 586 circular RNAs (circRNAs) that were expressed differently in LDD than in normal discs. We constructed lncRNAs and circRNAs regulated competing endogenous RNAs (ceRNA) networks in LDD. Four lncRNAs, DANCR, CASK-AS1, SCARNA2, and LINC00638), and three circRNAs, hsa_circ_0005139, hsa_circ_0037858, and hsa_circ_0087890, were identified as key regulators of LDD progression. We found that hsa-miR-486-5p regulated the crosstalk among circRNA hsa_circ_0000189, lncRNA DANCR and 6 mRNAs, PYCR2, TOB1, ARHGAP5, RBPJ, CD247, SLC34A1. Gene ontology (GO) analysis demonstrated that these differently expressed lncRNAs and circRNAs were involved in cellular component organization or biogenesis, gene expression and negative regulation of metabolic processes. Our findings provide useful information for exploring new mechanisms for LDD and candidates for therapeutic targets.

Normal aging in human lumbar discs: An ultrastructural comparison.

The normal aging of the extracellular matrix and collagen content of the human lumbar intervertebral disc (IVD) remains relatively unknown despite vast amounts of basic science research, partly because of the use of inadequate surrogates for a truly normal, human IVD. Our objective in this study was to describe and compare the morphology and ultrastructure of lumbar IVDs in 2 groups of young (G1—<35 years) and elderly (G2—>65 years). Thirty L4-5 and L5-S1 discs per group were obtained during autopsies of presumably-asymptomatic individuals and analyzed with magnetic resonance imaging (MRI), a morphological grading scale, light microscopy, scanning electron microscopy (SEM) and immunohistochemistry (IHC) for collagen types I, II, III, IV, V, VI, IX and X. As expected, a mild to moderate degree of degeneration was present in G1 discs and significantly more advanced in G2. The extracellular matrix of G2 discs was significantly more compact with an increase of cartilaginous features such as large chondrocyte clusters. Elastic fibers were abundant in G1 specimens and their presence correlated more with age than with degeneration grade, being very rare in G2. SEM demonstrated persistence of basic structural characteristics such as denser lamellae with Sharpey-type insertions into the endplates despite advanced age or degeneration grades. Immunohistochemistry revealed type II collagen to be the most abundant type followed by collagen IV. All collagen types were detected in every disc sector except for type X collagen. Statistical analysis demonstrated a general decrease in collagen expression from G1 to G2 with an annular- and another nuclear-specific pattern. These results suggest modifications of IVD morphology do not differ between the anterior or posterior annulus but are more advanced or happen earlier in the posterior areas of the disc. This study finally describes the process of extracellular matrix modification during disc degeneration in an unselected, general population and demonstrates it is similar to the same process in the cervical spine as published previously.

A growth-based model for the prediction of fiber angle distribution in the intervertebral disc annulus fibrosus.

There is a growing interest in the development of patient-specific finite element models of the human lumbar spine for both the assessment of injury risk and the development of treatment strategies. A current challenge in implementing these models is that the outer annulus fibrosus of the disc is composed of concentric sheets of aligned collagen fibers, the helical angles of which vary spatially. In finite element models, fiber angle is typically assumed to be constant, based on average experimental measurements from a small number of locations. The present study hypothesized that the full spatial distribution of fiber angles in the annulus fibrosus may be predicted for any disc geometry by assuming growth from a thin cylinder with constant fiber angle. This hypothesis was tested by developing an analytical model of disc growth and calibrating it with fiber angle measurements of adult bovine caudal discs. The calibrated model was then run on a representative human lumbar disc geometry. The model was able to accurately predict fiber angle distributions in both the experimental bovine caudal disc measurements and literature-reported human lumbar disc measurements. Despite its theoretical basis in development, the model requires only mature state geometry, making it practical for implementation in patient-specific finite element analyses, in which disc geometry is obtained from clinical imaging.

Effects of diurnal loading on the transport of charged antibiotics into intervertebral discs

The objective of this study was to quantitatively analyze the effect of diurnal loading on the transport of various charged antibiotics into negatively charged human intervertebral disc (IVD). Transport of charged antibiotics into a human lumbar disc was analyzed using a 3D finite element model. The valence (z) of the electrical charge of antibiotics varied from z = +2 (positively charged) to z = −2 (negatively charged). An uncharged antibiotic (z = 0) was used as a control. Cases with transient antibiotic concentration at disc boundaries [to mimic intravenous (IV) infusion] were simulated. Our results showed that diurnal compression increased the concentrations in the nucleus pulposus (NP) region, but degreased the concentrations in the annulus fibrosus (AF) region for all charged or non-charged drugs. The overall concentration (averaged over disc) increased with diurnal compression. The diurnal compression had more effects on negatively charged antibiotics than positively charged ones. For example, at day 5 with diurnal compression, the diurnal compression increased the concentration of negatively charged drug (z = −1) in NP by 18.3%, but only by 6.6% for positively charged one (z = +1). In AF, diurnal compression decreased the concentration by 13.2% for negatively charged drug (z = −1) versus 1.2% for positively charged one (z = +1). Note these percentages are the averaged values over day 5. This study provides quantitative information on understanding the mechanisms of charged drug transport in human IVDs.

Comparison of human lumbar disc pressure characteristics during simulated spinal manipulation vs. spinal mobilization.

The present study aimed to investigate the differences in human lumbar intradiscal pressure (IDP) characteristics during simulated spinal manipulation and spinal mobilization. A total of 12 adult fresh lumbar spinal specimens (T12‑S2) were randomly divided into two groups. The parameters of simulated spinal mobilization were as follows: Preload angle, 15˚ (speed, 3˚/sec); maximum angle, 20˚ (speed, 1˚/sec); and 9N horizontal force to the L5 spinous process. The parameters of simulated spinal manipulation were as follows: Preload angle, 15˚ (speed, 3˚/sec); impulse angle, 20˚ (impulse speed, 33˚/sec) and 22N horizontal force to the L5 spinous process. The maximal IDP during both techniques was greater than the initial and end pressures (P<0.01). There was no difference between the initial and end IDP (P>0.05). The maximal IDP on the rotating side was greater than that on the contralateral side during the two techniques (P<0.05). There was no difference in both initial and end IDPs between the two sides (P>0.05). There was no difference in the maximal IDP between the two techniques (P>0.05). The ascending speed of IDP during manipulation was faster than during mobilization (P<0.01), while there was no difference in the descending speed between the two techniques (P>0.05). The maximal IDP on the rotating side was greater than the contralateral side during simulated spinal mobilization and manipulation (P<0.05). The ascending speed of IDP was faster during manipulation than mobilization (P<0.01). Therefore, thrust manipulation may have more instant impact to discs than mobilization.

Roles of SDF-1/CXCR4 axis in cartilage endplate stem cells mediated promotion of nucleus pulposus cells proliferation

Stem cells transplantation has shown considerable promise in intervertebral disc repair and low-back pain release. Cartilage endplate stem cells (CESCs) also showed potential for nucleus pulposus (NP) regeneration in a rabbit disc degeneration model, the precise mechanism was unclear. Here we investigated the effects of CESCs on NP cells (NPCs) proliferation and the mechanism in vitro. CESCs and NPCs were isolated from surgical specimens of degenerative human lumbar disc. NPCs were co-cultured with CESCs at a 1:1 ratio or cultured in CESCs conditioned medium (CESCs-CM). NPCs proliferation was evaluated by Ki-67 staining, CCK-8 assay and cell cycle analysis. Gene expressions were detected by qRT-PCR and activation of Akt and ERK1/2 was detected by western blot. CXCR4 antagonist AMD3100 was used to block SDF-1/CXCR4 axis. ERK1/2 and Akt inhibitors were used to block Akt and ERK1/2 activation. Results showed that NPCs proliferation was promoted by direct-contact co-culturing with CESCs as well as culturing in CESCs-CM. SDF-1 expression level in CESCs was significantly higher than that in NPCs, while CXCR4 was the opposite. Promotion of NPCs proliferation mediated by CESCs-CM could be partially attenuated by AMD3100. CESCs-CM activated both Akt and ERK1/2 in NPCs, while rhSDF-1 scarcely activated Akt but obviously activated ERK1/2. Akt and ERK1/2 inhibitors could partially inhibited CESCs-CM mediated promotion of NPCs proliferation and showed cumulative effect, while ERK1/2 inhibitor and AMD3100 could significantly abrogate SDF-1 mediated promotion of NPCs proliferation. Our results suggested that CESCs might promote NPCs proliferation in a paracrine pathway, which was partially mediated by SDF-1/CXCR4 axis via ERK1/2 signaling transduction pathway.