A method for characterising human intervertebral disc glycosaminoglycan disaccharides using liquid chromatography-mass spectrometry with multiple reaction monitoring

Mechanobiology of Hyaluronan: Connecting Biomechanics and Bioactivity in Musculoskeletal Tissues

Hyaluronan (HA) plays well-recognized mechanical and biological roles in articular cartilage and synovial fluid, where it contributes to tissue structure and lubrication. An understanding of how HA contributes to the structure of other musculoskeletal tissues, including muscle, bone, tendon, and intervertebral discs, is growing. In addition, the use of HA-based therapies to restore damaged tissue is becoming more prevalent. Nevertheless, the relationship between biomechanical stimuli and HA synthesis, degradation, and signaling in musculoskeletal tissues remains understudied, limiting the utility of HA in regenerative medicine. In this review, we discuss the various roles and significance of endogenous HA in musculoskeletal tissues. We use what is known and unknown to motivate new lines of inquiry into HA biology within musculoskeletal tissues and in the mechanobiology governing HA metabolism by suggesting questions that remain regarding the relationship and interaction between biological and mechanical roles of HA in musculoskeletal health and disease.

Potential molecular targets and drugs for basement membranes-related intervertebral disk degeneration through bioinformatics analysis and molecular docking

BACKGROUND

Through bioinformatics analysis to identify the hub genes of Intervertebral disc degeneration (IVDD) associated with basement membranes (BMs) and find out the potential molecular targets and drugs for BMs-related annulus fibrosus (AF) degeneration based on bioinformatic analysis and molecular approach.

METHODS

Intervertebral disc degeneration (IVDD) related targets were obtained from GeneCards, DisGenet and OMIM databases. BMs related genes were obtained from Basement membraneBASE database. The intersection targets were identified and subjected to protein-to-protein interaction (PPI) construction via STRING. Hub genes were identified and conducted Gene ontology (GO) and pathway enrichment analysis through MCODE and Clue GO in Cytospace respectively. DSigDB database was retrieved to predict therapeutic drugs and molecular docking was performed through PyMOL, AutoDock 1.5.6 to verify the binding energy between the drug and the different expressed hub genes. Finally, GSE70362 from GEO database was obtained to verify the different expression and correlation of each hub gene for AF degeneration.

RESULTS

We identified 41 intersection genes between 3 disease targets databases and Basement membraneBASE database. PPI network revealed 25 hub genes and they were mainly enriched in GO terms relating to glycosaminoglycan catabolic process, the TGF-β signaling pathway. 4 core targets were found to be significant via comparison of microarray samples and they showed strong correlation. The molecular docking results showed that the core targets have strong binding energy with predicting drugs including chitosamine and retinoic acid.

CONCLUSIONS

In this study, we identified hub genes, pathways, potential targets, and drugs for treatment in BMs-related AF degeneration and IVDD.

The Dimethylmethylene Blue Assay (DMMB) for the Quantification of Sulfated Glycosaminoglycans

The 1,9-dimethylmethylene blue (DMMB) assay enables the detection of sulfated glycosaminoglycans (sGAGs). This assay can be used to quickly quantify the sGAG content in a large number of samples using spectrophotometry. While this widespread assay appears straightforward, there are certain pitfalls that need to be considered.

The impact of matrix age on intervertebral disc regeneration

With the lack of effective treatments for low back pain, the use of extracellular matrix (ECM)-based biomaterials have emerged with undeniable promise for IVD regeneration. Decellularized scaffolds can recreate an ideal microenvironment inducing tissue remodeling and repair. In particular, fetal tissues have a superior regenerative capacity given their ECM composition. In line with this, we unraveled age-associated alterations of the nucleus pulposus (NP) matrisome. Thus, the aim of the present work was to evaluate the impact of ECM donor age on IVD de/regeneration. Accordingly, we optimized an SDS (0.1 %, 1 h)-based decellularization protocol that preserves ECM cues in bovine NPs from different ages. After repopulation with adult NP cells, younger matrices showed the highest repopulation efficiency. Most importantly, cells seeded on younger scaffolds produced healthy ECM proteins suggesting an increased capacity to restore a functional IVD microenvironment. In vivo, only fetal matrices decreased neovessel formation, showing an anti-angiogenic potential. Our findings demonstrate that ECM donor age has a strong influence on angiogenesis and ECM de novo synthesis, opening new avenues for novel therapeutic strategies for the IVD. Additionally, more appropriate 3D models to study age-associated IVD pathology were unveiled.

Imaging of exercise-induced spinal remodeling in elite rowers

OBJECTIVES

As in-vivo knowledge of training-induced remodeling of intervertebral discs (IVD) is scarce, this study assessed how lumbar IVDs change as a function of long-term training in elite athletes and age-matched controls using compositional Magnetic Resonance Imaging (MRI).

DESIGN

Prospective case-control study.

METHODS

Prospectively, lumbar spines of 17 elite rowers (ERs) of the German national rowing team (mean age: 23.9 ± 3.3 years) were imaged on a clinical 3.0 T MRI scanner. ERs were imaged twice during the annual training cycle, i.e., at training intensive preseason preparations (t₀) and 6 months later during post-competition recovery (t₁). Controls (n = 22, mean age: 26.3 ± 1.9 years) were imaged once at corresponding time points (t₀: n = 11; t₁: n = 11). Segment-wise, the glycosaminoglycan (GAG) content of lumbar IVDs (n = 195) was determined using glycosaminoglycan chemical exchange saturation transfer (gagCEST). Linear mixed models were set up to assess the influence of cohort and other variables on GAG content.

RESULTS

During preseason, IVD GAG values of ERs were significantly higher than those of controls (ERs(t₀): 2.58 ± 0.27% (mean ± standard deviations); controls(t₀): 1.43 ± 0.36%; p ≤ 0.001), while during post-competition recovery, such differences were not present anymore (ERs(t₁): 2.11 ± 0.18%; controls(t₁): 1.89 ± 0.24%; p = 0.362).

CONCLUSIONS

Professional elite-level rowing is transiently associated with significantly higher gagCEST values, which indicate increased lumbar IVD-GAG content and strong remodeling effects in response to training. Beyond professional rowing, core-strengthening full-body exercise may help to enhance the resilience of the lumbar spine as a potential therapeutic target in treating back pain.

De novo neo-hyaline-cartilage from bovine organoids in viscoelastic hydrogels

Regenerative therapies for articular cartilage are currently clinically available. However, they are associated with several drawbacks that require resolution. Optimizing chondrocyte expansion and their assembly, can reduce the time and costs of these therapies and more importantly increase their clinical success. In this study, cartilage organoids were quickly mass produced from bovine chondrocytes with a new suspension expansion protocol. This new approach led to massive cell proliferation, high viability and the self-assembly of organoids. These organoids were composed of collagen type II, type VI, glycosaminoglycans, with Sox9 positive cells, embedded in a pericellular and interterritorial matrix similarly to hyaline cartilage. With the goal of producing large scale tissues, we then encapsulated these organoids into alginate hydrogels with different viscoelastic properties. Elastic hydrogels constrained the growth and fusion of the organoids inhibiting the formation of a tissue. In contrast, viscoelastic hydrogels allowed the growth and fusion of the organoids into a homogenous tissue that was rich in collagen type II and glycosaminoglycans. The encapsulation of organoids to produce in vitro neocartilage also proved to be superior to the conventional method of encapsulating 2D expanded chondrocytes. This study describes a multimodal approach that involves chondrocyte expansion, organoid formation and their assembly into neohyaline-cartilage which proved to be superior to the current standard approaches used in cartilage tissue engineering. STATEMENT OF SIGNIFICANCE: In this manuscript, we describe a new and simple methodology to quickly mass produce self-assembling cartilage organoids. Due to their matrix content and structure similarities with native cartilage, these organoids on their own have the potential to revolutionize cartilage research and the manner in which we study signaling pathways, disease progression, tissue engineering, drug development, etc. Furthermore, these organoids and their fast mass production were combined with a key relatively ignored hydrogel characteristic, viscoelasticity, to demonstrate their fusion into a neo-tissue. This has the potential to open the door for large scale cartilage regeneration such as for entire joint surfaces.

Analysis of the Glycosaminoglycan Chains of Proteoglycans

Glycosaminoglycans (GAGs) are heterogeneous, negatively charged, macromolecules that are found in animal tissues. Based on the form of component sugar, GAGs have been categorized into four different families: heparin/heparan sulfate, chondroitin/dermatan sulfate, keratan sulfate, and hyaluronan. GAGs engage in biological pathway regulation through their interaction with protein ligands. Detailed structural information on GAG chains is required to further understanding of GAG-ligand interactions. However, polysaccharide sequencing has lagged behind protein and DNA sequencing due to the non-template-driven biosynthesis of glycans. In this review, we summarize recent progress in the analysis of GAG chains, specifically focusing on techniques related to mass spectroscopy (MS), including separation techniques coupled to MS, tandem MS, and bioinformatics software for MS spectrum interpretation. Progress in the use of other structural analysis tools, such as nuclear magnetic resonance (NMR) and hyphenated techniques, is included to provide a comprehensive perspective.

Glycosaminoglycan remodeling during chondrogenic differentiation of human bone marrow-/synovial-derived mesenchymal stem/stromal cells under normoxia and hypoxia

Glycosaminoglycans (GAGs) are major components of cartilage extracellular matrix (ECM), which play an important role in tissue homeostasis not only by providing mechanical load resistance, but also as signaling mediators of key cellular processes such as adhesion, migration, proliferation and differentiation. Specific GAG types as well as their disaccharide sulfation patterns can be predictive of the tissue maturation level but also of disease states such as osteoarthritis. In this work, we used a highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to perform a comparative study in terms of temporal changes in GAG and disaccharide composition between tissues generated from human bone marrow- and synovial-derived mesenchymal stem/stromal cells (hBMSC/hSMSC) after chondrogenic differentiation under normoxic (21% O₂) and hypoxic (5% O₂) micromass cultures. The chondrogenic differentiation of hBMSC/hSMSC cultured under different oxygen tensions was assessed through aggregate size measurement, chondrogenic gene expression analysis and histological/immunofluorescence staining in comparison to human chondrocytes. For all the studied conditions, the compositional analysis demonstrated a notable increase in the average relative percentage of chondroitin sulfate (CS), the main GAG in cartilage composition, throughout MSC chondrogenic differentiation. Additionally, hypoxic culture conditions resulted in significantly different average GAG and CS disaccharide percentage compositions compared to the normoxic ones. However, such effect was considerably more evident for hBMSC-derived chondrogenic aggregates. In summary, the GAG profiles described here may provide new insights for the prediction of cartilage tissue differentiation/disease states and to characterize the quality of MSC-generated chondrocytes obtained under different oxygen tension culture conditions.

Inactivation of FAM20B causes cell fate changes in annulus fibrosus of mouse intervertebral disc and disc defects via the alterations of TGF-β and MAPK signaling pathways

Intervertebral disc (IVD) disorder is often caused by the defect of annulus fibrosus (AF), especially that of the outer AF. Studies about the mechanisms governing the development of the outer AF are needed for a better understanding of pathogenesis of IVD defects. Glycosaminoglycans (GAGs) are essential components of extracellular matrix (ECM) in AF. FAM20B is a newly identified xylose kinase that catalyzes the biosynthesis of GAGs. In this study, we created Fam20B conditional knockout (cKO) mice in which FAM20B was inactivated in type I collagen-expressing cells, the main type of cells in the outer AF of IVD. The cKO mice showed severe spine deformity and remarkable IVD defects associated with AF malformation. The AF of cKO mice had a lower level of chondroitin sulfate and heparan sulfate, and the outer AF cells lost their normal fibroblast-like morphology and acquired chondrocyte phenotypes, expressing a higher level of Sox 9 and type II collagen along with a reduced level of type I collagen. The level of phospho-Smad 2 and phospho-Smad 3, and that of scleraxis, a downstream target molecule of canonical TGF-β signaling pathway were significantly lower in the AF of cKO mice. The AF in cKO mice also manifested altered levels in the molecules associated with the activations of MAPK pathway; the changes included the increase of phospho-P38 and phospho-ERK and a decrease of phospho-JNK. These results indicate that FAM20B plays an essential role in the development of AF by regulating the TGF-β signaling and MAPK signaling pathways.

Expression and activity of hyaluronidases HYAL-1, HYAL-2 and HYAL-3 in the human intervertebral disc

PURPOSE

Hyaluronic acid plays an essential role in water retention of the intervertebral disc (IVD) and thus provides flexibility and shock absorbance in the spine. Hyaluronic acid gets degraded by hyaluronidases (HYALs), and some of the resulting fragments were previously shown to induce an inflammatory and catabolic response in human IVD cells. However, no data currently exist on the expression and activity of HYALs in IVD health and disease.

METHODS

Gene expression, protein expression and activity of HYALs were determined in human IVD biopsies with different degrees of degeneration (n = 50 total). Furthermore, freshly isolated human IVD cells (n = 23 total) were stimulated with IL-1β, TNF-α or H₂O₂, followed by analysis of HYAL-1, HYAL-2 and HYAL-3 gene expression.

RESULTS

Gene expression of HYAL-1 and protein expression of HYAL-2 significantly increased in moderate/severe disc samples when compared to samples with no or low IVD degeneration. HYAL activity was not significantly increased due to high donor-donor variation, but seemed overall higher in the moderate/severe group. An inflammatory environment, as seen during IVD disease, did not affect HYAL-1, HYAL-2 or HYAL-3 expression, whereas exposure to oxidative stress (100 µM H₂O₂) upregulated HYAL-2 expression relative to untreated controls.

CONCLUSION

Although HYAL-1, HYAL-2 and HYAL-3 are all expressed in the IVD, HYAL-2 seems to have the highest pathophysiological relevance. Nonetheless, further studies will be needed to comprehensively elucidate its significance and to determine its potential as a therapeutic target. These slides can be retrieved under Electronic Supplementary Material.

Radial variation in biochemical composition of the bovine caudal intervertebral disc

Bovine caudal discs have been widely used in spine research due to their increased availability, large size, and mechanical and biochemical properties that are comparable to healthy human discs. However, despite their extensive use, the radial variations in bovine disc composition have not yet been rigorously quantified with high spatial resolution. Previous studies were limited to qualitative analyses or provided limited spatial resolution in biochemical properties. Thus, the main objective of this study was to provide quantitative measurements of biochemical composition with higher spatial resolution than previous studies that employed traditional biochemical techniques. Specifically, traditional biochemical analyses were used to measure water, sulfated glycosaminoglycan, collagen, and DNA contents. Gravimetric water content was compared to data obtained through Raman spectroscopy and differential scanning calorimetry. Additionally, spatial distribution of lipids in the disc's collagen network was visualized and quantified, for the first time, using multi-modal second harmonic generation (SHG) and Coherent anti-Stokes Raman (CARS) microscopy. Some heterogeneity was observed in the nucleus pulposus, where the water content and water-to-protein ratio of the inner nucleus were greater than the outer nucleus. In contrast, the bovine annulus fibrosus exhibited a more heterogeneous distribution of biochemical properties. Comparable results between orthohydroxyproline assay and SHG imaging highlight the potential benefit of using SHG microscopy as a less destructive method for measuring collagen content, particularly when relative changes are of interest. CARS images showed that lipid deposits were distributed equally throughout the disc and appeared either as individual droplets or as clusters of small droplets. In conclusion, this study provided a more comprehensive assessment of spatial variations in biochemical composition of the bovine caudal disc.

Stem Cell Therapies for Treatment of Discogenic Low Back Pain: a Comprehensive Review

PURPOSE OF REVIEW

Discogenic low back pain (DLBP) stems from pathology in one or more intervertebral discs identified as the root cause of the pain. It is the most common type of chronic low back pain (LBP), representing 26-42% of attributable cases.

RECENT FINDINGS

The clinical presentation of DLBP includes increased pain when sitting, coughing, or sneezing, and experiencing relief when standing or ambulating. Dermatomal radiation of pain to the lower extremity and neurological symptoms including numbness, motor weakness, and urinary or fecal incontinence are signs of advanced disease with disc prolapse, nerve root compression, or spinal stenosis. Degenerative disc disease is caused by both a decrease in disc nutrient supply causing decreased oxygen, lowered pH, and lessened ability of the intervertebral disc (IVD) to respond to increased load or injury; moreover, changes in the extracellular matrix composition cause weakening of the tissue and skewing the extracellular matrix's (ECM) harmonious balance between catabolic and anabolic factors for cell turnover in favor of catabolism. Thus, the degeneration of the disc causes a shift from type II to type I collagen expression by NP cells and a decrease in aggrecan synthesis leads to dehydrated matrix cells ultimately with loss of swelling pressure needed for mechanical support. Cell-based therapies such as autologous nucleus pulposus cell re-implantation have in animal models and human trials shown improvements in LBP score, retention of hydration in IVD, and increased disc height. Percutaneously delivered multipotent mesenchymal stem cell (MSC) therapy has been proposed as a potential means to uniquely ameliorate discogenic LBP holistically through three mechanisms: mitigation of primary nociceptive disc pain, slow or reversal of the catabolic metabolism, and restoration of disc tissue. Embryonic stem cells (ESCs) can differentiate into cells of all three germ layers in vitro, but their use is hindered related to ethical concerns, potential for immune rejection after transplantation, disease, and teratoma formation. Another similar approach to treating back pain is transplantation of the nucleus pulposus, which, like stem cell therapy, seeks to address the underlying cause of intervertebral disc degeneration by aiming to reverse the destructive inflammatory process and regenerate the proteoglycans and collagen found in healthy disc tissue. Preliminary animal models and clinical studies have shown mesenchymal stem cell implantation as a potential therapy for IVD regeneration and ECM restoration via a shift towards favorable anabolic balance and reduction of pain.

Compositional and structural analysis of glycosaminoglycans in cell-derived extracellular matrices

The extracellular matrix (ECM) is a highly dynamic and complex meshwork of proteins and glycosaminoglycans (GAGs) with a crucial role in tissue homeostasis and organization not only by defining tissue architecture and mechanical properties, but also by providing chemical cues that regulate major biological processes. GAGs are associated with important physiological functions, acting as modulators of signaling pathways regulating several cellular processes such as cell growth and differentiation. Recently, in vitro fabricated cell-derived ECM have emerged as promising materials for regenerative medicine due to their ability of better recapitulate the native ECM-like composition and structure, without the limitations of availability and pathogen transfer risks of tissue-derived ECM scaffolds. However, little is known about the molecular and more specifically, GAG composition of these cell-derived ECM. In this study, three different cell-derived ECM were produced in vitro and characterized in terms of their GAG content, composition and sulfation patterns using a highly sensitive liquid chromatography-tandem mass spectrometry technique. Distinct GAG compositions and disaccharide sulfation patterns were verified for the different cell-derived ECM. Additionally, the effect of decellularization method on the GAG and disaccharide relative composition was also assessed. In summary, the method presented here offers a novel approach to determine the GAG composition of cell-derived ECM, which we believe is critical for a better understanding of ECM role in directing cellular responses and has the potential for generating important knowledge to use in the development of novel ECM-like biomaterials for tissue engineering applications.