Heparan Sulfate Proteoglycan Synthesis Is Dysregulated in Human Osteoarthritic Cartilage

Syndecan-4 inhibition attenuates cartilage degeneration in temporomandibular joint osteoarthritis

BACKGROUND

Syndecan 4 (SDC4), a type I transmembrane proteoglycan, serves as a critical link between chondrocytes and the extracellular matrix.

OBJECTIVE

This study aimed to explore the role of SDC4 in cartilage degeneration of temporomandibular joint osteoathritis (TMJOA).

METHODS

Condylar chondrocytes were stimulated with varying concentrations of recombinant rat interleukin-1β (rrIL-1β) and SDC4 small interfering RNA (si-SDC4). Anti-SDC4 ectodomain-specific antibodies or IgG were intra-articularly administrated in a TMJOA model rats. SDC4 conditional knockout (SDC4-cKO) and Sdc4flox/flox mice were induced TMJOA. Cartilage degeneration was assessed using haematoxylin & eosin (H&E) and safranin O (SO) staining. Protein levels of SDC4, matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with a thrombospondin motifs 5 (ADAMTS5), tumour necrosis factor α (TNFα), type II collagen (Col-II), aggrecan (ACAN), cleaved caspase 3 (CASP3), Ki67 and related pathways in condylar cartilage were evaluated by immunohistochemical (IHC) staining or western blot assays.

RESULTS

SDC4 expression was evidently increased in MIA-model animals compared to control groups. rrIL-1β stimulation increased the expression of SDC4, MMP3 and ADAMTS5 expression in chondrocytes, while decreasing the expression of Col-II. These effects were reversed by si-SDC4 in vitro. In vivo, SDC4 blockade reduced the death of chondrocytes and the loss of cartilage matrix, which was evidenced by increased expression of Col-II and ACAN, and a decrease in SDC4, MMP13 and cleaved-CASP3-positive cells. Furthermore, the protein levels of ACAN and Ki67 were elevated, and the ERK1/2 and P38 signalling pathways were activated following SDC4 inhibition.

CONCLUSIONS

SDC4 inhibition significantly ameliorates condylar cartilage degeneration, which was mediated, at least partly, through P38 and ERK1/2 signalling. Inhibition of SDC4 may be of great value for the treatment of TMJOA.

The extracellular heparan sulfatase SULF2 limits myeloid IFNβ signaling and Th17 responses in inflammatory arthritis

Heparan sulfate (HS) proteoglycans are important regulators of cellular responses to soluble mediators such as chemokines, cytokines and growth factors. We profiled changes in expression of genes encoding HS core proteins, biosynthesis enzymes and modifiers during macrophage polarisation, and found that the most highly regulated gene was Sulf2, an extracellular HS 6-O-sulfatase that was markedly downregulated in response to pro-inflammatory stimuli. We then generated Sulf2+/- bone marrow chimeric mice and examined inflammatory responses in antigen-induced arthritis, as a model of rheumatoid arthritis. Resolution of inflammation was impaired in myeloid Sulf2+/- chimeras, with elevated joint swelling and increased abundance of pro-arthritic Th17 cells in synovial tissue. Transcriptomic and in vitro analyses indicated that Sulf2 deficiency increased type I interferon signaling in bone marrow-derived macrophages, leading to elevated expression of the Th17-inducing cytokine IL6. This establishes that dynamic remodeling of HS by Sulf2 limits type I interferon signaling in macrophages, and so protects against Th17-driven pathology.

Syndecans, Exostosins and Sulfotransferases as Potential Synovial Inflammation Moderators in Patients with Hip Osteoarthritis

The gradual deterioration of articular cartilage was thought to be the central event in osteoarthritis (OA), but recent studies demonstrated the importance of low-grade synovitis in the progression of OA. The Syndecan (SDC) family of membrane proteoglycans is known to be involved in the regulation of inflammation, but there is limited evidence considering the role of syndecans in OA synovitis. Our study aimed to investigate the hip OA synovial membrane expression patterns of SDC1, SDC2 and SDC4, as well as exostosins and sulfotransferases (enzymes involved in the polymerisation and modification of syndecans' heparan sulphate chains). Synovial membrane samples of patients with OA (24) were divided into two groups according to their Krenn synovitis score severity. The immunohistochemical expressions of SDC1, SDC2, SDC4, EXT1, EXT2, NDST1 and NDST2 in synovial intima and subintima were then analysed and compared with the control group (patients with femoral neck fracture). According to our study, the immunoexpression of SDC1, NDST1 and EXT2 is significantly increased in the intimal cells of OA synovial membrane in patients with lower histological synovitis scores and SDC4 in patients with higher synovitis scores, in comparison with non-OA controls. The difference in the expression of SDC2 among the OA and non-OA groups was insignificant. SDC1, SDC4, NDST1 and EXT2 seem to be involved as inflammation moderators in low-grade OA synovitis and, therefore, should be further investigated as potential markers of disease progression and therapeutic goals.

Genome-wide association study of growth curve parameters reveals novel genomic regions and candidate genes associated with metatarsal bone traits in chickens

The growth and development of chicken bones have an enormous impact on the health and production performance of chickens. However, the development pattern and genetic regulation of the chicken skeleton are poorly understood. This study aimed to evaluate metatarsal bone growth and development patterns in chickens via non-linear models, and to identify the genetic determinants of metatarsal bone traits using a genome-wide association study (GWAS) based on growth curve parameters. Data on metatarsal length (MeL) and metatarsal circumference (MeC) were obtained from 471 F2 chickens (generated by crossing broiler sires, derived from a line selected for high abdominal fat, with Baier layer dams) at 4, 6, 8, 10, and 12 weeks of age. Four non-linear models (Gompertz, Logistic, von Bertalanffy, and Brody) were used to fit the MeL and MeC growth curves. Subsequently, the estimated growth curve parameters of the mature MeL or MeC (A), time-scale parameter (b), and maturity rate (K) from the non-linear models were utilized as substitutes for the original bone data in GWAS. The Logistic and Brody models displayed the best goodness-of-fit for MeL and MeC, respectively. Single-trait and multi-trait GWASs based on the growth curve parameters of the Logistic and Brody models revealed 4 618 significant single nucleotide polymorphisms (SNPs), annotated to 332 genes, associated with metatarsal bone traits. The majority of these significant SNPs were located on Gallus gallus chromosome (GGA) 1 (167.433-176.318 Mb), GGA2 (96.791-103.543 Mb), GGA4 (65.003-83.104 Mb) and GGA6 (64.685-95.285 Mb). Notably, we identified 12 novel GWAS loci associated with chicken metatarsal bone traits, encompassing 35 candidate genes. In summary, the combination of single-trait and multi-trait GWASs based on growth curve parameters uncovered numerous genomic regions and candidate genes associated with chicken bone traits. The findings benefit an in-depth understanding of the genetic architecture underlying metatarsal growth and development in chickens.

Investigation of Glycosaminoglycans in Urine and Their Alteration in Patients with Juvenile Idiopathic Arthritis

(1) Background: In this study, we evaluated the modulation of urine glycosaminoglycans (GAGs), which resulted from etanercept (ETA) therapy in patients with juvenile idiopathic arthritis (JIA) in whom methotrexate therapy failed to improve their clinical condition. (2) Methods: The sulfated GAGs (sGAGs, by complexation with blue 1,9-dimethylmethylene), including chondroitin-dermatan sulfate (CS/DS) and heparan sulfate (HS), as well as non-sulfated hyaluronic acid (HA, using the immunoenzymatic method), were determined in the blood of 89 children, i.e., 30 healthy children and 59 patients with JIA both before and during two years of ETA treatment. (3) Results: We confirmed the remodeling of the urinary glycan profile of JIA patients. The decrease in the excretion of sGAGs (p < 0.05), resulting from a decrease in the concentration of the dominant fraction in the urine, i.e., CS/DS (p < 0.05), not compensated by an increase in the concentration of HS (p < 0.000005) and HA (p < 0.0005) in the urine of patients with the active disease, was found. The applied biological therapy, leading to clinical improvement in patients, at the same time, did not contribute to normalization of the concentration of sGAGs (p < 0.01) in the urine of patients, as well as CS/DS (p < 0.05) in the urine of sick girls, while it promoted equalization of HS and HA concentrations. These results indicate an inhibition of the destruction of connective tissue structures but do not indicate their complete regeneration. (4) Conclusions: The metabolisms of glycans during JIA, reflected in their urine profile, depend on the patient's sex and the severity of the inflammatory process. The remodeling pattern of urinary glycans observed in patients with JIA indicates the different roles of individual types of GAGs in the pathogenesis of osteoarticular disorders in sick children. Furthermore, the lack of normalization of urinary GAG levels in treated patients suggests the need for continued therapy and continuous monitoring of its effectiveness, which will contribute to the complete regeneration of the ECM components of the connective tissue and thus protect the patient against possible disability.

ALKBH5-mediated m6A demethylation of HS3ST3B1-IT1 prevents osteoarthritis progression

HS3ST3B1-IT1 was identified as a downregulated long noncoding RNA in osteoarthritic cartilage. However, its roles and mechanisms in the pathogenesis of osteoarthritis (OA) are unclear. In this study, we demonstrated that the expressions of HS3ST3B1-IT1 and its maternal gene HS3ST3B1 were downregulated and positively correlated in osteoarthritic cartilage. Overexpression of HS3ST3B1-IT1 significantly increased chondrocyte viability, inhibited chondrocyte apoptosis, and upregulated extracellular matrix (ECM) proteins, whereas HS3ST3B1-IT1 knockdown had the opposite effects. In addition, HS3ST3B1-IT1 significantly ameliorated monosodium-iodoacetate-induced OA in vivo. Mechanistically, HS3ST3B1-IT1 upregulated HS3ST3B1 expression by blocking its ubiquitination-mediated degradation. Knockdown of HS3ST3B1 reversed the effects of HS3ST3B1-IT1 on chondrocyte viability, apoptosis, and ECM metabolism. AlkB homolog 5 (ALKBH5)-mediated N6-methyladenosine (m6A) demethylation stabilized HS3ST3B1-IT1 RNA. Together, our data revealed that ALKBH5-mediated upregulation of HS3ST3B1-IT1 suppressed OA progression by elevating HS3ST3B1 expression, suggesting that HS3ST3B1-IT1/HS3ST3B1 may serve as potential therapeutic targets for OA treatment.

Efficient platform for synthesizing comprehensive heparan sulfate oligosaccharide libraries for decoding glycosaminoglycan-protein interactions

Glycosaminoglycans (GAGs) are abundant, ubiquitous carbohydrates in biology, yet their structural complexity has limited an understanding of their biological roles and structure-function relationships. Synthetic access to large collections of well defined, structurally diverse GAG oligosaccharides would provide critical insights into this important class of biomolecules and represent a major advance in glycoscience. Here we report a new platform for synthesizing large heparan sulfate (HS) oligosaccharide libraries displaying comprehensive arrays of sulfation patterns. Library synthesis is made possible by improving the overall synthetic efficiency through universal building blocks derived from natural heparin and a traceless fluorous tagging method for rapid purification with minimal manual manipulation. Using this approach, we generated a complete library of 64 HS oligosaccharides displaying all possible 2-O-, 6-O- and N-sulfation sequences in the tetrasaccharide GlcN-IdoA-GlcN-IdoA. These diverse structures provide an unprecedented view into the sulfation code of GAGs and identify sequences for modulating the activities of important growth factors and chemokines.

Transcriptomic changes in porcine articular cartilage one year following disruption of the anterior cruciate ligament

To determine the transcriptomic changes seen in early- to mid-stage posttraumatic osteoarthritis (PTOA) development, 72 Yucatan minipigs underwent transection of the anterior cruciate ligament. Subjects were randomized to no further intervention, ligament reconstruction, or ligament repair, followed by articular cartilage harvesting and RNA-sequencing at three different postoperative timepoints (1, 4, and 52 weeks). Six additional subjects received no ligament transection and provided cartilage tissue to serve as controls. Differential gene expression analysis between post-transection cartilage and healthy cartilage revealed an initial increase in transcriptomic differences at 1 and 4 weeks followed by a stark reduction in transcriptomic differences at 52 weeks. This analysis also showed how different treatments genetically modulate the course of PTOA following ligament disruption. Specific genes (e.g., MMP1, POSTN, IGF1, PTGFR, HK1) were identified as being upregulated in the cartilage of injured subjects across all timepoints regardless of treatment. At the 52-week timepoint, 4 genes (e.g., A4GALT, EFS, NPTXR, ABCA3) that-as far as we know-have yet to be associated with PTOA were identified as being concordantly differentially expressed across all treatment groups when compared to controls. Functional pathway analysis of injured subject cartilage compared to control cartilage revealed overarching patterns of cellular proliferation at 1 week, angiogenesis, ECM interaction, focal adhesion, and cellular migration at 4 weeks, and calcium signaling, immune system activation, GABA signaling, and HIF-1 signaling at 52 weeks.

Syndecan-4 is correlated with disease activity and serological characteristic of rheumatoid arthritis

Objectives

To describe the feature of expression of syndecan-4 in serum, synovial fluid (SF) and synovium in rheumatoid arthritis (RA) patients, and to analyze the correlation of syndecan-4 with disease activity and serological characteristic of RA.

Methods

Syndecan-4 in sera of 60 RA patients, 20 osteoarthritis (OA) patients, 20 healthy controls, and in SF of 25 RA patients and 25 OA patients were tested by enzyme linked immunosorbant assay. The expressions of syndecan-4 in synovium of RA and OA patients were detected by immunohistochemistry. The expression of syndecan-4 on synovial fibroblasts from RA and OA patients were detected by immunofluorescence. The correlation between serum syndecan-4 concentration and disease activity were analyzed in RA patients.

Results

The serum syndedcan-4 concentration was significantly higher in RA patients than in OA patients and healthy controls, and was higher in rheumatoid factor (RF)-positive RA patients than in RF-negative ones. Syndecan-4 concentration in SF of RA patients was comparable with OA patients. Syndecan-4 expression in synovial tissue was similar between RA and OA patients. The syndecan-4 concentration was significantly lower in SF than in serum of RA and OA patients. Syndecan-4 concentration in both serum and SF was positively correlated with disease activity of RA patients.

Conclusion

The serum syndecan-4 concentration was higher in RA patients than in OA patients, and significantly higher in RF-positive RA patients than in RF-negative ones. Syndecan-4 concentration in both serum and SF was positively correlated with disease activity of RA patients.

Perlecan: Roles in osteoarthritis and potential treating target

Osteoarthritis (OA) is the most common joint disease, affecting hundreds of millions of people globally, which leads to a high cost of treatment and further medical care and an apparent decrease in patient prognosis. The recent view of OA pathogenesis is that increased vascularity, bone remodeling, and disordered turnover are influenced by multivariate risk factors, such as age, obesity, and overloading. The view also reveals the gap between the development of these processes and early stage risk factors. This review presents the latest research on OA-related signaling pathways and analyzes the potential roles of perlecan, a typical component of the well-known protective structure against osteoarthritic pericellular matrix (PCM). Based on the experimental results observed in end-stage OA models, we summarized and analyzed the role of perlecan in the development of OA. In normal cartilage, it plays a protective role by maintaining the integrin of PCM and sequesters growth factors. Second, perlecan in cartilage is required to not only activate vascular epithelium growth factor receptor (VEGFR) signaling of endothelial cells for vascular invasion and catabolic autophagy, but also for different signaling pathways for the catabolic and anabolic actions of chondrocytes. Finally, perlecan may participate in pain sensitization pathways.

Serotype-specific transduction of canine joint tissue explants and cultured monolayers by self-complementary adeno-associated viral vectors

A formal screening of self-complementary adeno-associated virus (scAAV) vector serotypes in canine joint tissues has not been performed to date. Selecting appropriate serotypes is crucial for successful treatment due to their varying levels of tissue tropism. The objective of this study is to identify the most optimal scAAV vector serotype that maximizes transduction efficiencies in canine cell monolayer cultures (chondrocytes, synoviocytes, and mesenchymal stem cells) and tissue explant cultures (cartilage and synovium). Transduction efficiencies of scAAV serotypes 1, 2, 2.5, 3, 4, 5, 6, 8, and 9 were evaluated in each culture type in three different vector concentrations by encoding a green fluorescent protein. It was found that scAAV2 and 2.5 showed the overall highest transduction efficiency among serotypes with dose-response. Since possible immune response against conventional AAV2 was previously reported in dogs, the chimeric scAAV2.5 may be more suitable to use. Evaluation of the safety and efficacy of the scAAV2.5 vector with an appropriate therapeutic gene in vivo is indicated.

Heparan Sulfate Glycosaminoglycan Is Predicted to Stabilize Inflammatory Infiltrate Formation and RANKL/OPG Ratio in Severe Periodontitis in Humans

Since chronically inflamed periodontal tissue exhibits extracellular matrix (ECM) degradation, the possible alternative to standard periodontitis treatment is to restore ECM by supplementing its components, including heparan sulfate glycosaminoglycan (HS GAG). Supplementation of the degraded ECM with synthetic derivatives of HS GAGs has been shown to be effective for periodontal tissue regeneration in experimental animal models of periodontitis. However, the potential of HS GAG supplementation for the treatment of periodontal disease in humans is still unknown. Here, we used a statistical model to investigate the role of HS GAG on inflammatory infiltrate formation and alveolar bone resorption in humans with severe periodontitis. The model was based on data from immunofluorescence staining (IF) of human gingiva samples, and reconstruction of a subset of HS GAG -related proteins from STRING reactome database. According to predictions, increased expression of native HS GAG might stabilize the accumulation of gingival inflammatory infiltrate (represented by the general inflammatory cell marker CD45) and alveolar bone resorption (represented by Receptor Activator of Nuclear ΚΒ ligand (RANKL) and osteoprotegerin (OPG) ratio) but could not restore them to healthy tissue levels. Therefore, supplementation of native HS GAG may be of limited benefits for the treatment of sever periodontitis in humans.

Design and Synthesis of 1-O- and 6′-C-Modified Heparan Sulfate Trisaccharides as Human Endo-6-O-Sulfatase 1 Inhibitors

The extracellular human endo-6-O-sulfatases (Sulf-1 and Sulf-2) are responsible for the endolytic cleavage of the 6-sulfate groups from the internal D-glucosamine residues in the highly sulfated subdomains of heparan sulfate proteoglycans. A trisaccharide sulfate, IdoA2OS-GlcNS6S-IdoA2OS, was identified as the minimal size of substrate for Sulf-1. In order to study the complex structure with Sulf-1 for developing potential drugs, two trisaccharide analogs, IdoA2OS-GlcNS6OSO₂NH₂-IdoA2OS-OMe and IdoA2OS-GlcNS6NS-IdoA2OS-OMe, were rationally designed and synthesized as the Sulf-1 inhibitors with IC₅₀ values at 0.27 and 4.6 μM, respectively.

Pericellular heparan sulfate proteoglycans: Role in regulating the biosynthetic response of nucleus pulposus cells to osmotic loading

Background

Daily physiologic loading causes fluctuations in hydration of the intervertebral disc (IVD); thus, the embedded cells experience cyclic alterations to their osmotic environment. These osmotic fluctuations have been described as a mechanism linking mechanics and biology, and have previously been shown to promote biosynthesis in chondrocytes. However, this phenomenon has yet to be fully interrogated in the IVD. Additionally, the specialized extracellular matrix surrounding the cells, the pericellular matrix (PCM), transduces the biophysical signals that cells ultimately experience. While it is known that the PCM is altered in disc degeneration, whether it disrupts normal osmotic mechanotransduction has yet to be determined. Thus, our objectives were to assess: (1) whether dynamic osmotic conditions stimulate biosynthesis in nucleus pulposus cells, and (2) whether pericellular heparan sulfate proteoglycans (HSPGs) modulate the biosynthetic response to osmotic loading.

Methods

Bovine nucleus pulposus cells isolated with retained PCM were encapsulated in 1.5% alginate beads and treated with or without heparinase III, an enzyme that degrades the pericellular HSPGs. Beads were subjected to 1 h of daily iso-osmotic, hyper-osmotic, or hypo-osmotic loading for 1, 2, or 4 weeks. At each timepoint the total amount of extracellular and pericellular sGAG/DNA were quantified. Additionally, whether osmotic loading triggered alterations to HSPG sulfation was assessed via immunohistochemistry for the heparan sulfate 6-O-sulfertransferase 1 (HS6ST1) enzyme.

Results

Osmotic loading significantly influenced sGAG/DNA accumulation with a hyper-osmotic change promoting the greatest sGAG/DNA accumulation in the pericellular region compared with iso-osmotic conditions. Heparanase-III treatment significantly reduced extracellular sGAG/DNA but pericellular sGAG was not affected. HS6ST1 expression was not affected by osmotic loading.

Conclusion

Results suggest that hyper-osmotic loading promotes matrix synthesis and that modifications to HSPGs directly influence the metabolic responses of cells to osmotic fluctuations. Collectively, results suggest degeneration-associated modifications to pericellular HSPGs may contribute to the altered mechanobiology observed in disease.

The Extracellular Matrix of Articular Cartilage Controls the Bioavailability of Pericellular Matrix-Bound Growth Factors to Drive Tissue Homeostasis and Repair

The extracellular matrix (ECM) has long been regarded as a packing material; supporting cells within the tissue and providing tensile strength and protection from mechanical stress. There is little surprise when one considers the dynamic nature of many of the individual proteins that contribute to the ECM, that we are beginning to appreciate a more nuanced role for the ECM in tissue homeostasis and disease. Articular cartilage is adapted to be able to perceive and respond to mechanical load. Indeed, physiological loads are essential to maintain cartilage thickness in a healthy joint and excessive mechanical stress is associated with the breakdown of the matrix that is seen in osteoarthritis (OA). Although the trigger by which increased mechanical stress drives catabolic pathways remains unknown, one mechanism by which cartilage responds to increased compressive load is by the release of growth factors that are sequestered in the pericellular matrix. These are heparan sulfate-bound growth factors that appear to be largely chondroprotective and displaced by an aggrecan-dependent sodium flux. Emerging evidence suggests that the released growth factors act in a coordinated fashion to drive cartilage repair. Thus, we are beginning to appreciate that the ECM is the key mechano-sensor and mechano-effector in cartilage, responsible for directing subsequent cellular events of relevance to joint health and disease.

Regulation of FGF-2, FGF-18 and Transcription Factor Activity by Perlecan in the Maturational Development of Transitional Rudiment and Growth Plate Cartilages and in the Maintenance of Permanent Cartilage Homeostasis

The aim of this study was to highlight the roles of perlecan in the regulation of the development of the rudiment developmental cartilages and growth plate cartilages, and also to show how perlecan maintains permanent articular cartilage homeostasis. Cartilage rudiments are transient developmental templates containing chondroprogenitor cells that undergo proliferation, matrix deposition, and hypertrophic differentiation. Growth plate cartilage also undergoes similar changes leading to endochondral bone formation, whereas permanent cartilage is maintained as an articular structure and does not undergo maturational changes. Pericellular and extracellular perlecan-HS chains interact with growth factors, morphogens, structural matrix glycoproteins, proteases, and inhibitors to promote matrix stabilization and cellular proliferation, ECM remodelling, and tissue expansion. Perlecan has mechanotransductive roles in cartilage that modulate chondrocyte responses in weight-bearing environments. Nuclear perlecan may modulate chromatin structure and transcription factor access to DNA and gene regulation. Snail-1, a mesenchymal marker and transcription factor, signals through FGFR-3 to promote chondrogenesis and maintain Acan and type II collagen levels in articular cartilage, but prevents further tissue expansion. Pre-hypertrophic growth plate chondrocytes also express high Snail-1 levels, leading to cessation of Acan and CoI2A1 synthesis and appearance of type X collagen. Perlecan differentially regulates FGF-2 and FGF-18 to maintain articular cartilage homeostasis, rudiment and growth plate cartilage growth, and maturational changes including mineralization, contributing to skeletal growth.

Proteoglycans and Glycosaminoglycans in Stem Cell Homeostasis and Bone Tissue Regeneration

Stem cells maintain a subtle balance between self-renewal and differentiation under the regulatory network supported by both intracellular and extracellular components. Proteoglycans are large glycoproteins present abundantly on the cell surface and in the extracellular matrix where they play pivotal roles in facilitating signaling transduction and maintaining stem cell homeostasis. In this review, we outline distinct proteoglycans profiles and their functions in the regulation of stem cell homeostasis, as well as recent progress and prospects of utilizing proteoglycans/glycosaminoglycans as a novel glycomics carrier or bio-active molecules in bone regeneration.

Circ_0128846/miR-140-3p/JAK2 Network in Osteoarthritis Development

Circular RNAs (circRNAs) titrate the function of microRNAs (miRNAs), regulate transcription, and interfere with splicing. This study attempted to confirm the role of a novel circRNA circ_0128846 during osteoarthritis (OA) progression. Tissues and chondrocytes were isolated from OA patients. Overexpression and knockdown of target genes were generated using cell transfection and siRNA interference. Expression levels of genes were measured by qRT-PCR, Western blot, and immunohistochemistry, respectively. The interactions among circ_0128846, miR-140-3p, and JAK2 were verified by bioinformatics prediction, a dual-luciferase reporter assay, and RNA immunoprecipitation assay. The role of circ_0128846 in vivo was confirmed by the construction of experimental OA rats. Pathological changes were evaluated by hematoxylin and eosin and Safranin O staining. In OA patients, the level of circ_0128846 and JAK2 were up-regulated with down-regulated level of miR-140-3p. Circ_0128846 was principally located in the cytoplasm. Circ_0128846 silence enhanced cells viability, but reduced apoptosis rate and inflammatory response, which was obviously reversed by miR-140-3p knockdown. The overexpression of JAK2 reversed the effects of miR-140-3p on cell phenotypes. Circ_0128846 silence suppressed the level of MMP-13 and promoted the expression of collagen II by up-regulating miR-140-3p and down-regulating JAK2 in OA cells. Results of animal experiments demonstrated that circ_0128846 silence promoted collagen II expression and attenuated the OA progression by regulating the miR-140-3p/JAK2 axis. Circ_0128846 contributes to OA development through acting as a sponge RNA for miR-140-3p and thereby increasing JAK2 expression. Results indicated that targeting circ_0128846 may have the potential to alleviate OA progression.Abbreviations:circRNAs: Circular RNAs; miRNAs: microRNAs; OA: osteoarthritis; RIP: RNA immunoprecipitation; H&E: hematoxylin and eosin; ncRNAs: noncoding RNAs; ceRNA: competitive endogenous RNA; DMEM: Dulbecco's modified Eagle's medium; PBS: phosphate buffered saline; OE-circ_0128846: overexpression vector for circ_0128846; pcDNA3.1-JAK2: pcDNA3.1 overexpression vector for Janus kinase 2; NC: negative control; CCK-8: Cell Counting Kit-8; PI: propidium iodide; WT: Wild-type; mutants (MUT); SD rats: Sprague Dawley rats; DMM: destabilization of medial meniscus; IHC: immunohistochemistry; DAB: diaminobenzene; pre-Mrna: precursor mRNA.

The first human induced pluripotent stem cell line of Kashin-Beck disease reveals involvement of heparan sulfate proteoglycan biosynthesis and PPAR pathway

Kashin-Beck disease (KBD) is an endemic osteochondropathy. Due to a lack of suitable animal or cellular disease models, the research progress on KBD has been limited. Our goal was to establish the first disease-specific human induced pluripotent stem cell (hiPSC) cellular disease model of KBD, and to explore its etiology and pathogenesis exploiting transcriptome sequencing. HiPSCs were reprogrammed from dermal fibroblasts of two KBD and one healthy control donor via integration-free vectors. Subsequently, hiPSCs were differentiated into chondrocytes through three-week culture. Gene expression profiles in KBD, normal primary chondrocytes, and hiPSC-derived chondrocytes were defined by RNA sequencing. A Venn diagram was constructed to show the number of shared differentially expressed genes (DEGs) between KBD and normal. Gene oncology and Kyoto Encyclopedia of Genes and Genomes annotations were performed, and six DEGs were further validated in other individuals by RT-qPCR. KBD cellular disease models were successfully established by generation of hiPSC lines. Seventeen consistent and significant DEGs present in all compared groups (KBD and normal) were identified. RT-qPCR validation gave consistent results with the sequencing data. Glycosaminoglycan biosynthesis-heparan sulfate/heparin; PPAR signaling pathway; and cell adhesion molecules (CAMs) were identified to be significantly altered in KBD. Differentiated chondrocytes derived from KBD-origin hiPSCs provide the first cellular disease model for etiological studies of KBD. This study also provides new sights into the pathogenesis and etiology of KBD and is likely to inform the development of targeted therapeutics for its treatment.

Serpins in cartilage and osteoarthritis: what do we know?

Serpins (serine proteinase inhibitors) are an ancient superfamily of structurally similar proteins, the majority of which use an elegant suicide inhibition mechanism to target serine proteinases. Despite likely evolving from a single common ancestor, the 36 human serpins have established roles regulating diverse biological processes, such as blood coagulation, embryonic development and extracellular matrix (ECM) turnover. Genetic mutations in serpin genes underpin a host of monogenic disorders — collectively termed the ‘serpinopathies’ — but serpin dysregulation has also been shown to drive pathological mechanisms in many common diseases. Osteoarthritis is a degenerative joint disorder, characterised by the progressive destruction of articular cartilage. This breakdown of the cartilage is driven by the metalloproteinases, and it has long been established that an imbalance of metalloproteinases to their inhibitors is of critical importance. More recently, a role for serine proteinases in cartilage destruction is emerging; including the activation of latent matrix metalloproteinases and cell-surface receptors, or direct proteolysis of the ECM. Serpins likely regulate these processes, as well as having roles beyond serine proteinase inhibition. Indeed, serpins are routinely observed to be highly modulated in osteoarthritic tissues and fluids by ‘omic analysis, but despite this, they are largely ignored. Confusing nomenclature and an underappreciation for the role of serine proteinases in osteoarthritis (OA) being the likely causes. In this narrative review, serpin structure, biochemistry and nomenclature are introduced, and for the first time, their putative importance in maintaining joint tissues — as well as their dysregulation in OA — are explored.

Heparan Sulfate Deficiency in Cartilage: Enhanced BMP-Sensitivity, Proteoglycan Production and an Anti-Apoptotic Expression Signature after Loading

Osteoarthritis (OA) represents one major cause of disability worldwide still evading efficient pharmacological or cellular therapies. Severe degeneration of extracellular cartilage matrix precedes the loss of mobility and disabling pain perception in affected joints. Recent studies showed that a reduced heparan sulfate (HS) content protects cartilage from degradation in OA-animal models of joint destabilization but the underlying mechanisms remained unclear. We aimed to clarify whether low HS-content alters the mechano-response of chondrocytes and to uncover pathways relevant for HS-related chondro-protection in response to loading. Tissue-engineered cartilage with HS-deficiency was generated from rib chondrocytes of mice carrying a hypomorphic allele of Exostosin 1 (Ext1), one of the main HS-synthesizing enzymes, and wildtype (WT) littermate controls. Engineered cartilage matured for 2 weeks was exposed to cyclic unconfined compression in a bioreactor. The molecular loading response was determined by transcriptome profiling, bioinformatic data processing, and qPCR. HS-deficient chondrocytes expressed 3-6% of WT Ext1-mRNA levels. Both groups similarly raised Sox9, Col2a1 and Acan levels during maturation. However, HS-deficient chondrocytes synthesized and deposited 50% more GAG/DNA. TGFβ and FGF2-sensitivity of Ext1^gt/gt chondrocytes was similar to WT cells but their response to BMP-stimulation was enhanced. Loading induced similar activation of mechano-sensitive ERK and P38-signaling in WT and HS-reduced chondrocytes. Transcriptome analysis reflected regulation of cell migration as major load-induced biological process with similar stimulation of common (Fosl1, Itgα5, Timp1, and Ngf) as well as novel mechano-regulated genes (Inhba and Dhrs9). Remarkably, only Ext1-hypomorphic cartilage responded to loading by an expression signature of negative regulation of apoptosis with pro-apoptotic Bnip3 being selectively down-regulated. HS-deficiency enhanced BMP-sensitivity, GAG-production and fostered an anti-apoptotic expression signature after loading, all of which may protect cartilage from load-induced erosion.

Targeting Cartilage Degradation in Osteoarthritis

Osteoarthritis is a common, degenerative joint disease with significant socio-economic impact worldwide. There are currently no disease-modifying drugs available to treat the disease, making this an important area of pharmaceutical research. In this review, we assessed approaches being explored to directly inhibit metalloproteinase-mediated cartilage degradation and to counteract cartilage damage by promoting growth factor-driven repair. Metalloproteinase-blocking antibodies are discussed, along with recent clinical trials on FGF18 and Wnt pathway inhibitors. We also considered dendrimer-based approaches being developed to deliver and retain such therapeutics in the joint environment. These may reduce systemic side effects while improving local half-life and concentration. Development of such targeted anabolic therapies would be of great benefit in the osteoarthritis field.

Perlecan in the Natural and Cell Therapy Repair of Human Adult Articular Cartilage: Can Modifications in This Proteoglycan Be a Novel Therapeutic Approach?

Articular cartilage is considered to have limited regenerative capacity, which has led to the search for therapies to limit or halt the progression of its destruction. Perlecan, a multifunctional heparan sulphate (HS) proteoglycan, promotes embryonic cartilage development and stabilises the mature tissue. We investigated the immunolocalisation of perlecan and collagen between donor-matched biopsies of human articular cartilage defects (n = 10 × 2) that were repaired either naturally or using autologous cell therapy, and with age-matched normal cartilage. We explored how the removal of HS from perlecan affects human chondrocytes in vitro. Immunohistochemistry showed both a pericellular and diffuse matrix staining pattern for perlecan in both natural and cell therapy repaired cartilage, which related to whether the morphology of the newly formed tissue was hyaline cartilage or fibrocartilage. Immunostaining for perlecan was significantly greater in both these repair tissues compared to normal age-matched controls. The immunolocalisation of collagens type III and VI was also dependent on tissue morphology. Heparanase treatment of chondrocytes in vitro resulted in significantly increased proliferation, while the expression of key chondrogenic surface and genetic markers was unaffected. Perlecan was more prominent in chondrocyte clusters than in individual cells after heparanase treatment. Heparanase treatment could be a means of increasing chondrocyte responsiveness to cartilage injury and perhaps to improve repair of defects.

Heparan sulfate functions are altered in the osteoarthritic cartilage

BACKGROUND

Heparan sulfate (HS) proteoglycans (PG) may be found at the chondrocyte surface and in the pericellular cartilage matrix, and are involved in cell-cell and cell-matrix interactions. An important function of HS chains is to regulate cell fate through specific interactions with heparin-binding proteins (HBP) modulated by their complex sulfation pattern. Osteoarthritis (OA) is a joint disorder characterized by the degradation of articular cartilaginous extracellular matrix. The aim of this study was to investigate HS structure and functions in osteoarthritic cartilages compared to normal cartilages (controls).

METHODS

Glycosaminoglycans (GAG) were extracted from human macroscopically normal cartilages (controls, n = 7) and (OA cartilages n = 11). HS were isolated and quantified using the DMMB quantification method. Their structure and functions were then compared using respectively a HPLC analysis and HBP binding tests and their phenotypic effects on murine chondrocytes were studied by RQ-PCR. Statistical analyzes were performed using a one-way ANOVA followed by a Dunnett's test or a t test for pairwise comparisons.

RESULTS

In OA, HS were characterized by increased sulfation levels compared to controls. Moreover, the capacity of these HS to bind HBP involved in the OA pathophysiological process such as FGF2 and VEGF was reduced. Chondroitin sulfates and keratan sulfates regulated these binding properties. Finally, HS from OA cartilages induced the mRNA levels of catabolic markers such as MMP3, MMP13, and TS4 and inhibited the mRNA levels of anabolic markers such as COL2, ACAN, SOX9, and VEGF in murine articular chondrocytes.

CONCLUSION

The sulfation of HS chains was increased in OA cartilages with changes in HBP binding properties and biological effects on chondrocyte phenotypes. Thus, modified HS present in altered cartilages could be a novel therapeutic target in OA.

Interleukin 13 (IL-13)-regulated expression of the chondroprotective metalloproteinase ADAM15 is reduced in aging cartilage

Objective

The adamalysin metalloproteinase 15 (ADAM15) has been shown to protect against development of osteoarthritis in mice. Here, we have investigated factors that control ADAM15 levels in cartilage.

Design

Secretomes from wild-type and Adam15^−/− chondrocytes were compared by label-free quantitative mass spectrometry. mRNA was isolated from murine knee joints, either with or without surgical induction of osteoarthritis on male C57BL/6 mice, and the expression of Adam15 and other related genes quantified by RT-qPCR. ADAM15 in human normal and osteoarthritic cartilage was investigated similarly and by fluorescent immunohistochemistry. Cultured HTB94 chondrosarcoma cells were treated with various anabolic and catabolic stimuli, and ADAM15 mRNA and protein levels evaluated.

Results

There were no significant differences in the secretomes of chondrocytes from WT and Adam15^−/− cartilage. Expression of ADAM15 was not altered in either human or murine osteoarthritic cartilage relative to disease-free controls. However, expression of ADAM15 was markedly reduced upon aging in both species, to the extent that expression in joints of 18-month-old mice was 45-fold lower than in that 4.5-month-old animals. IL-13 increased expression of ADAM15 in HTB94 ​cells by 2.5-fold, while modulators of senescence and autophagy pathways had no effect. Expression of Il13 in the joint was reduced with aging, suggesting this cytokine may control ADAM15 levels in the joint.

Conclusion

Expression of the chondroprotective metalloproteinase ADAM15 is reduced in aging human and murine joints, possibly due to a concomitant reduction in IL-13 expression. We thus propose IL-13 as a novel factor contributing to increased osteoarthritis risk upon aging.

Interaction between C/EBPβ and RUNX2 promotes apoptosis of chondrocytes during human lumbar facet joint degeneration

The pathophysiological changes in cartilage are a crucial feature of lumbar facet joint (LFJ) degeneration and arthritis. However, the molecular mechanism of human LFJ degeneration remains largely defined. This study aimed to examine the changes in chondrocytes at different stages of degenerative LFJ using hematoxylin and eosin and Safranin O staining. The significant loss of chondrocytes in grades 2 and 3 of LFJs was observed. The expression levels of CCAAT enhancer binding protein β (C/EBPβ), Runt-related transcription factor 2 (RUNX2), and matrix metalloproteinase 13 (MMP13) also increased with the aggravation of degeneration (4.89, 5.77, and 6.3 times by Western blot). In vitro, chondrocytes scraped from the LFJs during surgery were stimulated by interleukin (IL)-1β to establish the injury model. The association of C/EBPβ and RUNX2 with active caspase-3 on chondrocytes was analyzed. The high expression level of C/EBPβ, RUNX2, and MMP13 was consistent with that of caspase-3, which reached a peak after 36 h of stimulation. Immunofluorescence suggested that C/EBPβ, RUNX2, and MMP13 co-labeled with active caspase-3. Moreover, immunoprecipitation data prompted that C/EBPβ was able to interact with RUNX2. The knockdown of C/EBPβ significantly decreased the expression levels of MMP13 and active caspase-3 (2.48 and 2.89 times as detected by Western blot analysis) and inhibited chondrocyte apoptosis, which was further demonstrated using flow cytometry. Taken together, the findings of this study uncovered that C/EBPβ could interact with RUNX2 to induce chondrocyte apoptosis in human LFJ degeneration by regulating the expression of MMP13.

An altered heparan sulfate structure in the articular cartilage protects against osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is a progressive degenerative disease of the articular cartilage caused by an unbalanced activity of proteases, cytokines and other secreted proteins. Since heparan sulfate (HS) determines the activity of many extracellular factors, we investigated its role in OA progression.

METHODS

To analyze the role of the HS level, OA was induced by anterior cruciate ligament transection (ACLT) in transgenic mice carrying a loss-of-function allele of Ext1 in clones of chondrocytes (Col2-rtTA-Cre;Ext1e2fl/e2fl). To study the impact of the HS sulfation pattern, OA was surgically induced in mice with a heterozygous (Ndst1+/-) or chondrocyte-specific (Col2-Cre;Ndst1fl/fl) loss-of-function allele of the sulfotransferase Ndst1. OA progression was evaluated using the OARSI scoring system. To investigate expression and activity of cartilage degrading proteases, femoral head explants of Ndst1+/- mutants were analyzed by qRT-PCR, Western Blot and gelatin zymography.

RESULTS

All investigated mouse strains showed reduced OA scores (Col2-rtTA-Cre;Ext1e2fl/e2fl: 0.83; 95% HDI 0.72-0.96; Ndst1+/-: 0.83, 95% HDI 0.74-0.9; Col2-Cre;Ndst1fl/fl: 0.87, 95% HDI 0.76-1). Using cartilage explant cultures of Ndst1 animals, we detected higher amounts of aggrecan degradation products in wildtype samples (NITEGE 4.24-fold, 95% HDI 1.05-18.55; VDIPEN 1.54-fold, 95% HDI 1.54-2.34). Accordingly, gelatin zymography revealed lower Mmp2 activity in mutant samples upon RA-treatment (0.77-fold, 95% HDI: 0.60-0.96). As expression of major proteases and their inhibitors was not altered, HS seems to regulate cartilage degeneration by affecting protease activity.

CONCLUSION

A decreased HS content or a reduced sulfation level protect against OA progression by regulating protease activity rather than expression.

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.

Heparanase: A Potential Therapeutic Target in Sarcomas

Sarcomas comprise a heterogeneous group of rare malignancies of mesenchymal origin including more than 70 subtypes. They may arise in muscle, bone, cartilage and other connective tissues. Their high histological and genetic heterogeneity makes diagnosis and treatment very challenging. Deregulation of heparanase has been found in several sarcoma subtypes and high expression levels have been correlated with poor prognosis in Ewing's sarcoma and osteosarcoma. Altered expression of specific heparan sulfate proteoglycans and heparan sulfate biosynthetic enzymes has also been observed. Advances in molecular pathogenesis of sarcomas have evidenced the critical role of several heparan sulfate binding growth factors and receptor tyrosine kinases, highly interconnected with the microenvironment, in sustaining tumor growth and progression. Interference with heparanase/heparan sulfate functions represents a potential therapeutic approach in sarcoma. In this chapter, we summarize the current knowledge about the biological significance of heparanase expression and its potential as a therapeutic target in subtypes of both soft tissue and bone sarcomas. Particular emphasis is given to the involvement of heparan sulfate proteoglycans and their synthesizing and modifying enzymes in bone physiology and disorders leading up to the pathobiology of bone sarcomas. The chapter also describes the cooperation between exostin loss-of-function and heparanase upregulation in hereditary Multiple Osteochondroma syndrome as a paradigmatic example of constitutive alteration of the heparanase/heparan sulfate proteoglycan system which may contribute to progression to malignant secondary chondrosarcoma. Preclinical evidence of the role of heparanase as a promising therapeutic target in various sarcoma subtypes is finally resumed.

Syndecans and Enzymes for Heparan Sulfate Biosynthesis and Modification Differentially Correlate With Presence of Inflammatory Infiltrate in Periodontitis

Periodontitis is a common degenerative disease initiated by the bacteria in subgingival biofilm. The exposure to bacterial biofilm triggers host inflammatory response whose dysregulation is ultimately responsible for the destruction of hard and soft periodontal tissues resulting in tooth loss. To date, significant effort has been invested in the research of the involvement of host cells and inflammatory mediators in regulation of inflammatory response in periodontitis. Syndecans (Sdcs) belong to a four-member family of heparan sulfate proteoglycans (HSPGs). Sdcs are compound molecules comprised of the core protein to which several heparan sulfate (HS) glycosaminoglycan (GAG) chains are attached. The role of Sdcs in pathogenesis of periodontitis is poorly investigated despite the numerous reports from experimental studies about the critical involvement of these factors in modulation of various aspects of inflammatory response, such as the formation of inflammatory mediators gradients, leukocyte recruitment and extracellular matrix remodeling in resolution of inflammation. Most of these functions of Sdcs are HS-related and, thus, dependent upon the structure of HS. This, in turn, is determined by the combinatorial action of enzymes for biosynthesis and modification of HS such as exostosis (EXTs), sulfotransferases (NDSTs), and heparanase 1 (HPSE1). The data presented in this study clearly indicate that some Sdcs display different expression profiles in healthy and diseased periodontal tissue. Additionally, the differences in expression profiles of HS GAG biosynthesis and modification enzymes (EXTs, NDSTs, and HPSE1) in healthy and diseased periodontal tissue imply that changes in HS GAG content and structure might also take place during periodontitis. Most notably, expression profiles of Sdcs, EXTs, NDSTs, and HPSE1 differentially correlate with the presence of inflammatory infiltrate in healthy and diseased periodontal tissue, which might imply that these factors could also be involved in modulation of inflammatory response in periodontitis.

Heparan sulfate proteoglycans: The sweet side of development turns sour in mucopolysaccharidoses

Heparan sulfate proteoglycans (HSPGs) are complex carbohydrate-modified proteins ubiquitously expressed on cell surfaces, extracellular matrix and basement membrane of mammalian tissues. Beside to serve as structural constituents, they regulate multiple cellular activities. A critical involvement of HSPGs in development has been established, and perturbations of HSPG-dependent pathways are associated with many human diseases. Recent evidence suggest a role of HSPGs in the pathogenesis of mucopolysaccharidoses (MPSs) where the accumulation of undigested HS results in the loss of cellular functions, tissue damage and organ dysfunctions accounting for clinical manifestations which include central nervous system (CNS) involvement, degenerative joint disease and reduced bone growth. Current therapies are not curative but only ameliorate the disease symptoms. Here, we highlight the link between HSPG functions in the development of CNS and musculoskeletal structures and the etiology of some MPS phenotypes, suggesting that HSPGs may represent potential targets for the therapy of such incurable diseases.

Serglycin as part of IL-1β induced inflammation in human chondrocytes

Serglycin (SRGN) is an intracellular proteoglycan produced and secreted by several cell types. The increased expression of SRGN was associated with greater aggressiveness in cancer and inflammation. In this study, we demonstrated that SRGN is increased in human chondrocytes after IL-β stimulation. Furthermore, we found that secreted SRGN was able to bind the CD44 receptor thus participating in the extension of the inflammatory response. Using SRGN knockdown cells we observed a significantly decrease in specific inflammatory markers and NF-kB activation. Similar results were observed by blocking the CD44 receptor. These data provide further evidences for a direct involvement of SRGN in the mechanisms regulating the non-infectious chondrocytes damage, and the consequent joint inflammation and cartilage destruction in arthritis.