Crystals, inflammation, and osteoarthritis

An objective diagnosis of gout and calcium pyrophosphate deposition disease with machine learning of Raman spectra acquired in a point-of-care setting

OBJECTIVE

Raman spectroscopy is proposed as a next-generation method for the identification of monosodium urate (MSU) and calcium pyrophosphate (CPP) crystals in synovial fluid. As the interpretation of Raman spectra requires specific expertise, the method is not directly applicable for clinicians. We developed an approach to demonstrate that the identification process can be automated with the use of machine learning techniques. The developed system is tested in a point-of-care-setting at our outpatient rheumatology department.

METHODS

We collected synovial fluid samples from 446 patients with various rheumatic diseases from three centres. We analysed all samples with our Raman spectroscope and used 246 samples for training and 200 samples for validation. Trained observers classified every Raman spectrum as MSU, CPP or other. We designed two one-against-all classifiers, one for MSU and one for CPP. These classifiers consisted of a principal component analysis model followed by a support vector machine.

RESULTS

The accuracy for classification of CPP using the 2023 ACR/EULAR CPPD classification criteria was 96.0% (95% CI: 92.3, 98.3), while the accuracy for classification of MSU using the 2015 ACR/EULAR gout classification criteria was 92.5% (95% CI: 87.9, 95.7). Overall, the accuracy for classification of pathological crystals was 88.0% (95% CI: 82.7, 92.2). The model was able to discriminate between pathological crystals, artifacts and other particles such as microplastics.

CONCLUSION

We here demonstrate that potentially complex Raman spectra from clinical patient samples can be successfully classified by a machine learning approach, resulting in an objective diagnosis independent of the opinion of the medical examiner.

Synovial fluid dual-biomarker algorithm accurately differentiates osteoarthritis from inflammatory arthritis

Osteoarthritis (OA) prevalence increases as the population ages. Diagnosing osteoarthritis often occurs in the late stages when cartilage degradation is severe, making it difficult to distinguish from other types of arthritis. Accurate differentiation of primary osteoarthritis from other arthritic conditions is crucial for effective treatment planning. A new diagnostic test has been developed that uses a dual-biomarker algorithm to inform osteoarthritis diagnosis. Synovial fluid from patients with confirmed primary osteoarthritis showed elevated levels of cartilage oligomeric matrix protein. However, this biomarker alone could not distinguish primary osteoarthritis from other inflammatory conditions that also cause cartilage deterioration. Therefore, a combinatorial algorithm using cartilage oligomeric matrix protein and Interleukin-8 concentrations was developed to differentiate primary osteoarthritis from inflammatory arthritis. Clinical decision limits for cartilage oligomeric matrix protein concentration and the cartilage oligomeric matrix protein to Interleukin-8 ratio were established and validated using 171 human knee synovial fluid specimens. The osteoarthritis algorithm demonstrated clinical sensitivity and specificity of 87.0% and 88.9%, respectively. This is the first report of a biomarker test that can differentiate primary osteoarthritis from inflammatory arthritis with a high degree of accuracy.

Interplay of calcium pyrophosphate crystals, oxidative stress, and clinical features on knee osteoarthritis severity

BACKGROUND

Deposition of calcium pyrophosphate (CPP) crystals is observed in most joints affected by severe osteoarthritis (OA). CPP may cause local damage by inducing an inflammatory process and oxidative stress (OS).

OBJECTIVES

To evaluate inflammation and OS induced by CPP deposition and their association with the degree of knee OA.

METHODS

Synovial fluid (SF) from patients with OA classified as grade 3 and 4 (ACR criteria) was analyzed. Reactive oxygen species (ROS) and H2O2 levels were quantified, and inflammation by white blood cell (WBC) count. CPPs were detected by polarized light microscopy. Multifactorial dimensionality reduction (MDR) was used to visualize possible interactive effects between variables.

RESULTS

Fifty-six SF were analyzed, 22 (39.28%) were in moderate OA and 34 (60.71%) in severe OA. CPPs were identified in 17 moderate OA and 18 severe OA samples. In the moderate OA, ROS levels were significantly higher in the CPP + group (5.0% vs 2.0%, P = 0.03). Body mass index and CPP were significantly correlated (r =  - 0.439, P = 0.041). In the severe OA group, there were significant correlations of age with WBC (r =  - 0.431, P = 0.011), WBC with H2O2 (r = 0.454, P = 0.007), and ROS with H2O2 (r = 0.387, P = 0.024). MDR analysis revealed strong synergistic interactions between H2O2 and sex (6.68%) for moderate OA, while for severe OA, there were interactions between sex and ROS (6.99%) and between sex and inflammation (4.39%).

CONCLUSION

ROS and inflammation may be factors that potentiate damage in knee OA, and this may help in the development of antioxidant interventions for CPP-associated OA. Key Points • This study evaluated CPP crystal-induced oxidative stress and inflammation and their effect on OA severity. • In the moderate OA phenotype, CPP crystals modify ROS levels. • ROS and inflammation are factors that increase damage in knee OA, especially when CPP crystals are present.

Autoantibodies cause nociceptive sensitization in a mouse model of degenerative osteoarthritis

ABSTRACT

Previous preclinical and translational studies suggest that tissue trauma related to bony fracture and intervertebral disk disruption initiates the formation of pronociceptive antibodies that support chronic musculoskeletal pain conditions. This study tested this hypothesis in the monosodium iodoacetate (MIA) mouse model of osteoarthritis (OA) and extended the findings using OA patient samples. Monosodium iodoacetate was injected unilaterally into the knees of male and female wild-type (WT) and muMT mice (lacking B cells) to induce articular cartilage damage. Repeated nociceptive behavioral testing was performed, and serum was collected for antibody isolation and passive transfer experiments. Serum antibodies collected from patients with OA were tested in MIA-treated muMT mice. Biochemical analyses were performed on knee joint tissues. Monosodium iodoacetate-treated WT mice developed chronic ipsilateral hindlimb allodynia, hyperalgesia, and unweighting, but these pain behaviors were absent in MIA-treated muMT mice, indicating that cartilage injury-induced pain is B-cell dependent. IgM accumulation was observed in the knee tissues of MIA-treated mice, and intra-articular injection of IgM from MIA-treated mice into MIA-treated muMT mice caused nociceptive sensitization. Similarly, intra-articular injection of IgM from patients with OA was pronociceptive in muMT MIA mice and control subject IgM had no effect. Monosodium iodoacetate-injected joints demonstrate elevated levels of complement component 5a (C5a) and C5a receptor blockade using intra-articular PMX-53-reduced sensitization. These data suggest that MIA-treated mice and patients with OA generate pronociceptive antibodies, and further support the pronociceptive autoimmunity hypothesis for the transition from tissue injury to chronic musculoskeletal pain.

Discovery of calcite as a new pro-inflammatory calcium-containing crystal in human osteoarthritic synovial fluid

OBJECTIVE

We aimed to characterize calcium-containing crystals present in synovial fluid from patients with knee osteoarthritis (OA) using Raman spectroscopy, and specifically investigate the biological effects of calcite crystals.

DESIGN

Thirty-two synovial fluid samples were collected pre-operatively from knee OA patients undergoing total joint arthroplasty. An integrated Raman polarized light microscope was used for identification of crystals in synovial fluid. Human peripheral blood mononuclear cells (PBMC's), human OA articular chondrocytes (HACs) and fibroblast-like synoviocytes (FLSs) were exposed to calcite crystals. Expression of relevant cytokines and inflammatory genes were measured using enzyme-linked immuno sorbent assay (ELISA) and real-time polymerase chain reaction (PCR).

RESULTS

Various calcium-containing crystals were identified, including calcium pyrophosphate (37.5 %) and basic calcium phosphate (21.8 %), but they were never found simultaneously in the same OA synovial fluid sample. For the first time, we discovered the presence of calcite crystals in 93.8 % of the samples, while dolomite was detected in 25 % of the cases. Characterization of the cellular response to calcite crystal exposure revealed increased production of innate immune-derived cytokines by PBMC's, when co-stimulated with lipopolysaccharide (LPS). Additionally, calcite crystal stimulation of HACs and FLSs resulted in enhanced secretion of pro-inflammatory molecules and alterations in the expression of extracellular matrix remodeling enzymes.

CONCLUSIONS

This study highlights the unique role of Raman spectroscopy in OA crystal research and identified calcite as a novel pro-inflammatory crystal type in OA synovial fluid. Understanding the role of specific crystal species in the OA joint may open new avenues for pharmacological interventions and personalized approaches to treating OA.

Titanium Dioxide Promotes the Growth and Aggregation of Calcium Phosphate and Monosodium Urate Mixed Crystals

The increased utilization of titanium dioxide (TiO2) nanoparticles (TNPs) in various industrial and consumer products has raised concerns regarding its harmful effect due to its accumulation within the different systems of the human body. Here, we focused on the influence of TNPs on the growth and aggregation of two crucial crystalline substances, calcium phosphate (CaP) and monosodium urate (MSU), particularly its implications in gout disease. In this study, we adopted microscopic techniques and generated kinetic models to examine the interactions between TNPs, CaP and MSU, and crystallization, under controlled laboratory conditions. Our findings reveal that TNPs not only facilitate the growth of these crystals but also promote their co-aggregations. Crystal dissolution kinetics also exhibit that an increase in TNPs concentration corresponds to a reduction in the dissolution rate of CaP and MSU crystals in presence of the dissoluting agent hydroxycitrate (Hcit). These observations suggest that TNPs can stabilize CaP+MSU mixed crystals, which underscores the significance of TNPs' exposure in the pathogenesis of gout disease.

Anti-osteoarthritis, Bone Protective and Antiinflammatory Effect of Lusianthridin against Monosodium Iodoacetate Induced Osteoarthritis via Suppression of Inflammatory Pathway

Osteoarthritis (OA) is characterized by the gradual deterioration and worsening of the knee joint, leading to both pain and deformity. The current research exhibited the anti-osteoarthritis effect of lusianthridin against monosodium iodoacetate (MIA) induced OA in rats. RAW cells were used for the cell viability. The inflammatory cytokines and mediators were estimated in the cell lines after the lipopolysaccharide (LPS) treatment. For the in vivo study, the rats were received the intraperitoneal administration of MIA (3 mg/kg) for the induction of OA. The rats were received the oral administration of lusianthridin (5, 10 and 20 mg/kg) and the body and organ weight estimated. Antioxidant, cytokines, inflammatory and matrix metalloproteinases (MMP) level were also estimated. The mRNA expression of MMP were also estimated. The lusianthridin treatment remarkably suppressed the cell viability. LPS induced RAW cell suppressed the level of nitrate, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), cyclooxygenase-2 (COX-2), prostaglandin (PGE2), MMP-2 and MMP-9 level. Lusianthridin remarkably altered the level of body weight and organ weight (liver, spleen, renal and heart weight). lusianthridin suppressed the oxidative stress via altered the level of antioxidant parameters. Lusianthridin significantly (p < 0.001) decreased the level of cartilage oligometrix matrix protein (COMP) and c-reactive protein (CRP); cytokines such as TNF-α, IL-1β, IL-6, IL-10; inflammatory parameters include 5- Lipoxygenase (5-LOX), COX-2, leukotriene B4 (LTB4), PGE2; transforming growth factor beta (TGF-β); MMP level like MMP-1, 3, 9, 13, respectively. Lusianthridin significantly suppressed the mRNA expression of MMP. Collectively, the result of the study showed that antiosteoarthritis effect of lusianthridin via suppression of inflammatory parameters.

Synovial Fluid from Patients with Osteoarthritis Shows Different Inflammatory Features Depending on the Presence of Calcium Pyrophosphate Crystals

The role of calcium pyrophosphate (CPP) crystals in osteoarthritis (OA) is still a matter of debate. With this study we aimed to investigate the inflammatory features of synovial fluid (SF) collected from patients with OA with CPP crystals compared with those without crystals. We also explored the effect of OA SF on monocytes response. SFs were collected from adult patients with OA and subdivided according to the presence of crystals. Local cellular and humoral inflammatory mediators were analysed in the SF samples. The expression levels of IL-1β, IL-18, CASP-1, NLRP3, and GAPDH were measured by RT-PCR in the cells obtained by pelleting the SF samples. For the in vitro study, a monocytic cell line was treated with selected SF samples. SF with CPP crystals showed a significant increase in inflammatory cellular indices and higher levels of IL-1β, IL-8, and caspase-1 transcript with respect to SF without crystals. Higher concentrations of VEGF were also observed in the early stages of the whole OA patients. THP-1 cells stimulated with OA SF released a significant amount of IL-1 β in culture supernatants. This study demonstrated that SF collected from patients with OA shows different inflammatory features depending on the presence of CPP crystals.

Anti-Osteoarthritis Mechanism of the Nrf2 Signaling Pathway

Osteoarthritis (OA) is a chronic degenerative disease and the primary pathogenic consequence of OA is inflammation, which can affect a variety of tissues including the synovial membrane, articular cartilage, and subchondral bone. The development of the intra-articular microenvironment can be significantly influenced by the shift of synovial macrophages between pro-inflammatory and anti-inflammatory phenotypes. By regulating macrophage inflammatory responses, the NF-κB signaling route is essential in the therapy of OA; whereas, the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway appears to manage the relationship between oxidative stress and inflammation. Additionally, it has been demonstrated that under oxidative stress and inflammation, there is a significant interaction between transcriptional pathways involving Nrf2 and NF-κB. Studying how Nrf2 signaling affects inflammation and cellular metabolism may help us understand how to treat OA by reprogramming macrophage behavior because Nrf2 signaling is thought to affect cellular metabolism. The candidates for treating OA by promoting an anti-inflammatory mechanism by activating Nrf2 are also reviewed in this paper.

B-cell capacity for expansion and differentiation into plasma cells are altered in osteoarthritis

OBJECTIVE

Autoantibody (autoAbs) production in osteoarthritis (OA), coupled with evidence of disturbed B-cell homoeostasis, suggest a potential role for B-cells in OA. B-cells can differentiate with T-cell help (T-dep) or using alternative Toll like recptor (TLR) co-stimulation (TLR-dep). We analysed the capacity for differentiation of B-cells in OA versus age-matched healthy controls (HCs) and compared the capacity of OA synovitis-derived stromal cells to provide support for plasma cell (PC) maturation.

METHODS

B-cells were isolated from OA and HC. Standardised in vitro models of B-cell differentiation were used comparing T-dep (CD40 (cluster of differentiation-40/BCR (B-cell receptor)-ligation) versus TLR-dep (TLR7/BCR-activation). Differentiation marker expression was analysed by flow-cytometry; antibody secretion (immunnoglobulins IgM/IgA/IgG) by ELISA (enzyme-linked immunosorbent assay), gene expression by qPCR (quantitative polymerase chain reaction).

RESULTS

Compared to HC, circulating OA B-cells showed an overall more mature phenotype. The gene expression profile of synovial OA B-cells resembled that of PCs. Circulating B-cells differentiated under both TLR-dep and T-dep, however OA B-cells executed differentiation faster in terms of change in surface marker and secreted more antibody at Day 6, while resulting in similar PC numbers at Day 13, with an altered phenotype at Day 13 in OA. The main difference was reduced early B-cells expansion in OA (notably in TLR-dep) and reduced cell death. Stromal cells support from OA-synovitis allowed better PC survival compared to bone marrow, with an additional population of cells and higher Ig-secretion.

CONCLUSION

Our findings suggest that OA B-cells present an altered capacity for proliferation and differentiation while remaining able to produce antibodies, notably in synovium. These findings may partly contribute to autoAbs development as recently observed in OA synovial fluids.

Arthroscopic Implantation of Adipose-Derived Stromal Vascular Fraction Improves Cartilage Regeneration and Pain Relief in Patients With Knee Osteoarthritis

Purpose

To compare the pain relief and cartilage repair status of patients with knee osteoarthritis who received arthroscopic treatment with or without stromal vascular fraction (SVF) implantation.

Methods

We retrospectively evaluated the patients who were examined with 12-month follow-up magnetic resonance imaging (MRI) after arthroscopic treatment for knee osteoarthritis from September 2019 to April 2021. Patients were included in this study if they had grade 3 or 4 knee osteoarthritis according to the Outerbridge classification in MRI. The visual analog scale (VAS) was used for pain assessment over the follow-up period (baseline and at 1-, 3-, 6-, and 12-month follow-ups). Cartilage repair was evaluated using follow-up MRIs based on Outerbridge grades and the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system.

Results

Among 97 patients who received arthroscopic treatment, 54 patients received arthroscopic treatment alone (conventional group) and 43 received arthroscopic treatment along with SVF implantation (SVF group). In the conventional group, the mean VAS score decreased significantly at 1-month post-treatment compared with baseline (P < .05), and gradually increased from 3 to 12 months' post-treatment (all P < .05). In the SVF group, the mean VAS score decreased until 12 months post-treatment compared with baseline (all P < .05 except P = .780 in 1-month vs 3-month follow-ups). Significantly greater pain relief was reported in the SVF group than in the conventional group at 6 and 12 months' post-treatment (all P < .05). Overall, Outerbridge grades were significantly greater in the SVF group than in the conventional group (P < .001). Similarly, mean Magnetic Resonance Observation of Cartilage Repair Tissue scores were significantly greater (P < .001) in the SVF group (70.5 ± 11.1) than in the conventional group (39.7 ± 8.2).

Conclusions

The results regarding pain improvement and cartilage regeneration and the significant correlation between pain and MRI outcomes at 12-months follow-up indicate that the arthroscopic SVF implantation technique may be useful for repairing cartilage lesions in knee osteoarthritis.

Level of Evidence

Level III, retrospective comparative study.

Ablation of TRPC3 disrupts Ca2+ signaling in salivary ductal cells and promotes sialolithiasis

Clinical studies and structural analyses of salivary stones strongly suggest a linkage between higher saliva calcium (Ca2+) and salivary stone formation, sialolithiasis; however, the process and the mechanism leading to Ca2+ overload during sialolithiasis is not well understood. Here, we show that TRPC3 null (-/-) mice presented with a reduction in Ca2+ entry and current in ductal cells with higher saliva [Ca2+] suggesting diminished transepithelial Ca2+ flux across the salivary ductal cells, leaving more Ca2+ in ductal fluid. Significantly, we found that TRPC3 was expressed in mice and human salivary ductal cells, while intraductal stones were detected in both mice (TRPC3-/-) and patient (sialolithiasis) salivary glands. To identify the mechanism, we found that TRPC3 was crucial in preventing the expression of calcification genes (BMP2/6, Runx2) in ductal cells which may be due to higher extracellular Ca2+ in SMG tissues. Similarly, inflammatory (IL6, NLRP3), fibrotic (FN1, TGFβ1) and apoptotic (Bax1/Bcl2) markers were also elevated, suggesting that the loss of TRPC3 induces genetic changes that leads to salivary gland cell death and induction of inflammatory response. Overall, ablation of TRPC3-/- leads to higher saliva [Ca2+], along with elevated detrimental gene expressions, altogether contributing to salivary gland stone formation.

Chondrocyte Hypertrophy in Osteoarthritis: Mechanistic Studies and Models for the Identification of New Therapeutic Strategies

Articular cartilage shows limited self-healing ability owing to its low cellularity and avascularity. Untreated cartilage defects display an increased propensity to degenerate, leading to osteoarthritis (OA). During OA progression, articular chondrocytes are subjected to significant alterations in gene expression and phenotype, including a shift towards a hypertrophic-like state (with the expression of collagen type X, matrix metalloproteinases-13, and alkaline phosphatase) analogous to what eventuates during endochondral ossification. Present OA management strategies focus, however, exclusively on cartilage inflammation and degradation. A better understanding of the hypertrophic chondrocyte phenotype in OA might give new insights into its pathogenesis, suggesting potential disease-modifying therapeutic approaches. Recent developments in the field of cellular/molecular biology and tissue engineering proceeded in the direction of contrasting the onset of this hypertrophic phenotype, but knowledge gaps in the cause-effect of these processes are still present. In this review we will highlight the possible advantages and drawbacks of using this approach as a therapeutic strategy while focusing on the experimental models necessary for a better understanding of the phenomenon. Specifically, we will discuss in brief the cellular signaling pathways associated with the onset of a hypertrophic phenotype in chondrocytes during the progression of OA and will analyze in depth the advantages and disadvantages of various models that have been used to mimic it. Afterwards, we will present the strategies developed and proposed to impede chondrocyte hypertrophy and cartilage matrix mineralization/calcification. Finally, we will examine the future perspectives of OA therapeutic strategies.

Low-Grade Inflammation in the Pathogenesis of Osteoarthritis: Cellular and Molecular Mechanisms and Strategies for Future Therapeutic Intervention

Osteoarthritis (OA) is a musculoskeletal disease characterized by cartilage degeneration and stiffness, with chronic pain in the affected joint. It has been proposed that OA progression is associated with the development of low-grade inflammation (LGI) in the joint. In support of this principle, LGI is now recognized as the major contributor to the pathogenesis of obesity, aging, and metabolic syndromes, which have been documented as among the most significant risk factors for developing OA. These discoveries have led to a new definition of the disease, and OA has recently been recognized as a low-grade inflammatory disease of the joint. Damage-associated molecular patterns (DAMPs)/alarmin molecules, the major cellular components that facilitate the interplay between cells in the cartilage and synovium, activate various molecular pathways involved in the initiation and maintenance of LGI in the joint, which, in turn, drives OA progression. A better understanding of the pathological mechanisms initiated by LGI in the joint represents a decisive step toward discovering therapeutic strategies for the treatment of OA. Recent findings and discoveries regarding the involvement of LGI mediated by DAMPs in OA pathogenesis are discussed. Modulating communication between cells in the joint to decrease inflammation represents an attractive approach for the treatment of OA.

Histone Deacetylase Inhibitors Downregulate Calcium Pyrophosphate Crystal Formation in Human Articular Chondrocytes

Calcium pyrophosphate (CPP) deposition disease (CPPD) is a form of CPP crystal-induced arthritis. A high concentration of extracellular pyrophosphate (ePPi) in synovial fluid is positively correlated with the formation of CPP crystals, and ePPi can be upregulated by ankylosis human (ANKH) and ectonucleotide pyrophosphatase 1 (ENPP1) and downregulated by tissue non-specific alkaline phosphatase (TNAP). However, there is currently no drug that eliminates CPP crystals. We explored the effects of the histone deacetylase (HDAC) inhibitors (HDACis) trichostatin A (TSA) and vorinostat (SAHA) on CPP formation. Transforming growth factor (TGF)-β1-treated human primary cultured articular chondrocytes (HC-a cells) were used to increase ePPi and CPP formation, which were determined by pyrophosphate assay and CPP crystal staining assay, respectively. Artificial substrates thymidine 5′-monophosphate p-nitrophenyl ester (p-NpTMP) and p-nitrophenyl phosphate (p-NPP) were used to estimate ENPP1 and TNAP activities, respectively. The HDACis TSA and SAHA significantly reduced mRNA and protein expressions of ANKH and ENPP1 but increased TNAP expression in a dose-dependent manner in HC-a cells. Further results demonstrated that TSA and SAHA decreased ENPP1 activity, increased TNAP activity, and limited levels of ePPi and CPP. As expected, both TSA and SAHA significantly increased the acetylation of histones 3 and 4 but failed to block Smad-2 phosphorylation induced by TGF-β1. These results suggest that HDACis prevented the formation of CPP by regulating ANKH, ENPP1, and TNAP expressions and can possibly be developed as a potential drug to treat or prevent CPPD.

The role of inflammation in mesenchymal stromal cell therapy in osteoarthritis, perspectives for post-traumatic osteoarthritis: a review

OA is a complex and highly prevalent degenerative disease affecting the whole joint, in which factors like genetic predisposition, gender, age, obesity and traumas contribute to joint destruction. ∼50-80% of OA patients develop synovitis. OA-associated risk factors contribute to joint instability and the release of cartilage matrix fragments, activating the synovium to release pro-inflammatory factors and catabolic enzymes in turn damaging the cartilage and creating a vicious circle. Currently, no cure is available for OA. Mesenchymal stromal cells (MSCs) have been tested in OA for their chondrogenic and anti-inflammatory properties. Interestingly, MSCs are most effective when administered during synovitis. This review focusses on the interplay between joint inflammation and the immunomodulation by MSCs in OA. We discuss the potential of MSCs to break the vicious circle of inflammation and describe current perspectives and challenges for clinical application of MSCs in treatment and prevention of OA, focussing on preventing post-traumatic OA.

The Damage-Associated Molecular Patterns (DAMPs) as Potential Targets to Treat Osteoarthritis: Perspectives From a Review of the Literature

During the osteoarthritis (OA) process, activation of immune systems, whether innate or adaptive, is strongly associated with low-grade systemic inflammation. This process is initiated and driven in the synovial membrane, especially by synovium cells, themselves previously activated by damage-associated molecular patterns (DAMPs) released during cartilage degradation. These fragments exert their biological activities through pattern recognition receptors (PRRs) that, as a consequence, induce the activation of signaling pathways and beyond the release of inflammatory mediators, the latter contributing to the vicious cycle between cartilage and synovial membrane. The primary endpoint of this review is to provide the reader with an overview of these many molecules categorized as DAMPs and the contribution of the latter to the pathophysiology of OA. We will also discuss the different strategies to control their effects. We are convinced that a better understanding of DAMPs, their receptors, and associated pathological mechanisms represents a decisive issue for degenerative joint diseases such as OA.

Recent Advances in Clinical Translation of Intra-Articular Osteoarthritis Drug Delivery Systems

Osteoarthritis (OA) is a degenerative disease of the joints and a leading cause of physical disability in adults. Intra-articular (IA) therapy is a popular treatment strategy for localized, single-joint OA; however, small-molecule drugs such as corticosteroids do not provide prolonged relief. One possible reason for their lack of efficacy is high clearance rates from the joint through constant lymphatic drainage of the synovial tissues and synovial fluid and also by their exchange via the synovial vasculature. Advanced drug delivery strategies for extended release of therapeutic agents in the joint space is a promising approach to improve outcomes for OA patients. Broadly, the basic principle behind this strategy is to encapsulate therapeutic agents in a polymeric drug delivery system (DDS) for diffusion- and/or degradation-controlled release, whereby degradation can occur by hydrolysis or tied to relevant microenvironmental cues such as pH, reactive oxygen species (ROS), and protease activity. In this review, we highlight the development of clinically tested IA therapies for OA and highlight recent systems which have been investigated preclinically. DDS strategies including hydrogels, liposomes, polymeric microparticles (MPs) and nanoparticles (NPs), drug conjugates, and combination systems are introduced and evaluated for clinical translational potential.

Degenerative osteoarthritis a reversible chronic disease

Osteoarthritis (OA) is the most common chronic musculoskeletal disorder. It can affect any joint and is the most frequent single cause of disability in older adults.

OA is a progressive degenerative disease involving the entire joint structure in a vicious circle that includes the capsule-bursa tissue inflammation, synovial fluid modifications, cartilage breakdown and erosions, osteochondral inflammatory damage leading to bone erosion and distortion.

Research has identified the initial inflammatory-immunologic process that starts this vicious cycle leading to so-called early OA. Research has also identified the role played in the disease advancement by synoviocytes type A and B, chondrocytes, extracellular matrix, local immune-inflammatory mediators and proteases.

This article investigates the joint-resident MSCs that play an essential local homeostatic role and regulate cell turn over and tissue repair. Resident MSCs establish and maintain a local regenerative microenvironment.

The understanding of OA physiopathology clarifies the core mechanisms by which minimally invasive interventions might be able to halt and reverse the course of early stage OA. Interventions employing PRP, MSCs and exosomes are considered in this article.

An emerging role for Toll-like receptors at the neuroimmune interface in osteoarthritis

Osteoarthritis (OA) is a chronic progressive, painful disease of synovial joints, characterized by cartilage degradation, subchondral bone remodeling, osteophyte formation, and synovitis. It is now widely appreciated that the innate immune system, and in particular Toll-like receptors (TLRs), contributes to pathological changes in OA joint tissues. Furthermore, it is now also increasingly recognized that TLR signaling plays a key role in initiating and maintaining pain. Here, we reviewed the literature of the past 5 years with a focus on how TLRs may contribute to joint damage and pain in OA. We discuss biological effects of specific damage-associated molecular patterns (DAMPs) which act as TLR ligands in vitro, including direct effects on pain-sensing neurons. We then discuss the phenotype of transgenic mice that target TLR pathways, and provide evidence for a complex balance between pro- and anti-inflammatory signaling pathways activated by OA DAMPs. Finally, we summarize clinical evidence implicating TLRs in OA pathogenesis, including polymorphisms and surrogate markers of disease activity. Our review of the literature led us to propose a model where multi-directional crosstalk between connective tissue cells (chondrocytes, fibroblasts), innate immune cells, and sensory neurons in the affected joint may promote OA pathology and pain.

Vitamin K as a Powerful Micronutrient in Aging and Age-Related Diseases: Pros and Cons from Clinical Studies

Vitamin K is a multifunctional micronutrient implicated in age-related diseases such as cardiovascular diseases, osteoarthritis and osteoporosis. Although vitamin K-dependent proteins (VKDPs) are described to have a crucial role in the pathogenesis of these diseases, novel roles have emerged for vitamin K, independently of its role in VKDPs carboxylation. Vitamin K has been shown to act as an anti-inflammatory by suppressing nuclear factor κB (NF-κB) signal transduction and to exert a protective effect against oxidative stress by blocking the generation of reactive oxygen species. Available clinical evidences indicate that a high vitamin K status can exert a protective role in the inflammatory and mineralization processes associated with the onset and progression of age-related diseases. Also, vitamin K involvement as a protective super-micronutrient in aging and ‘inflammaging’ is arising, highlighting its future use in clinical practice. In this review we summarize current knowledge regarding clinical data on vitamin K in skeletal and cardiovascular health, and discuss the potential of vitamin K supplementation as a health benefit. We describe the clinical evidence and explore molecular aspects of vitamin K protective role in aging and age-related diseases, and its involvement as a modulator in the interplay between pathological calcification and inflammation processes.

An open-label, prospective, multicenter, clinical study to evaluate efficacy of Ayuartis capsules in patients suffering from osteoarthritis of the knee(s)

Background

The management of chronic degenerative joint disorders such as osteoarthritis (OA) with ayurvedic medicines provides a safe and effective alternative. Ayurvedic medicines possess analgesic, anti-inflammatory, anti-oxidant and immunomodulator activities.

Aims

The main aim of the study was to assess the efficacy of Ayuartis capsule in patients suffering from OA of the knee(s).

Materials and Methods

Thirty-one patients suffering from OA knee(s) were recruited after evaluating them as per inclusion/exclusion criteria. Patients were advised to take two Ayuartis capsules twice daily orally for 90 days. Knee joint(s) pain was assessed on the Visual Analog Scale. Patients' joint pain, stiffness, and physical functions were assessed on the Western Ontario McMaster University Osteoarthritis (WOMAC) index. Quality of life (QOL) and the time required to walk 50 feet was evaluated. Patients were called for follow-up visits on every 15^th day till 90 days. Adverse events and vitals were recorded at every visit. Safety laboratory investigations were done before and after the completion of trial.

Statistical Analysis

Data describing quantitative measures are expressed as mean ± standard deviation. The comparison of variables representing categorical data was performed using pair t-test.

Results

The mean joint pain reduced significantly by 53.82% on day 90. The mean WOMAC combined score, pain score, stiffness score and difficulty score reduced significantly by 50.88%, 54.96%, 58.76% and 49.02%, respectively on day 90. A significant improvement was observed in mean QOL of patients. A significant reduction in mean time required to walk 50 feet was observed. Majority of the patients had shown good overall improvement and excellent tolerability to the trial drug.

Conclusion

Ayuartis capsule is a safe and effective medicine for the treatment of OA of the knee(s).

Inflammation in osteoarthritis: is it time to dampen the alarm(in) in this debilitating disease?

Osteoarthritis (OA) is the most common joint disease that strongly reduces the quality of life in patients; However, no disease-modifying therapy is available. For a long time, OA was considered a non-inflammatory disease that was the result of 'wear-and-tear' and abnormal mechanics, and therefore many considered the term 'osteoarthritis' a misnomer. However, during the last decades the notion arose that inflammation is not only present in the majority of OA patients but, rather, actively involved in the progression of the disease. Influx of immune cells is observed in the synovium and a plethora of inflammatory mediators is present in tissues and fluids from OA patients. These mediators cause the production of degrading enzymes that break down the cartilage matrix, which is the main hallmark of OA. Alarmins, which belong to the group of danger signals, have been implicated in many inflammatory diseases. They are among the first factors to be released upon cell stress due to, for example, infection, damage and inflammation. They attract and activate cells of the immune system and therefore lie at the base of the inflammatory reaction. In this narrative review, an overview of the history of OA, the evolving concept of inflammation as important factor in the OA pathogenesis, and particularly the central role that alarmins play in the initiation and maintenance of the low-grade inflammatory response in OA, is provided. Moreover, the targeting of alarmins as a promising approach to dampen the inflammation in OA is highlighted.

Autologous liquid platelet rich fibrin: A novel drug delivery system

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. Substantial work to date has focused on the potential role of these biomolecules during the healing process, and the carrier system utilized is a key factor in their effectiveness. Platelet rich fibrin (PRF) is a naturally derived fibrin scaffold that is easily obtained from peripheral blood following centrifugation. Slower centrifugation speeds have led to the commercialization of a liquid formulation (liquid-PRF) resulting in an upper plasma layer composed of liquid fibrinogen/thrombin prior to clot formation that remains in its liquid phase for approximately 15 min until injected into bodily tissues. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules. Potential target molecules including large (growth factors/cytokines and morphogenetic/angiogenic factors), as well as small (antibiotics, peptides, gene therapy and anti-osteoporotic) molecules are considered potential candidates for enhanced bone/cartilage tissue regeneration. Furthermore, liquid-PRF is introduced as a potential carrier system for various cell types and nano-sized particles that are capable of limiting/by-passing the immune system and minimizing potential foreign body reactions within host tissues following injection.

STATEMENT OF SIGNIFICANCE

There is currently widespread interest within the biomaterial field to locally deliver biomolecules for bone and cartilage regeneration. This review article focuses on the use of a liquid version of platelet rich fibrin (PRF) composed of liquid fibrinogen/thrombin as a drug delivery system. Herein, we introduce the use of liquid PRF as an advanced local delivery system for small and large biomolecules including growth factors, cytokines and morphogenetic/angiogenic factors, as well as antibiotics, peptides, gene therapy and anti-osteoporotic molecules as potential candidates for enhanced bone/cartilage tissue regeneration.

Emergent nanotherapies in microcrystal-induced arthritis

The anti-inflammatory and immunomodulatory effects of nanoparticles in several chronic diseases have been extensively researched. The aim of this review is to examine how nanoparticles modulate the inflammatory pathways that characterize the most prevalent forms of microcrystal-induced arthritis, including gout, pseudogout, and BCP-induced arthritis. The nanoparticles of chitosan-coated calcium phosphate, uricase, aceclofenac, and gold have been investigated in crystal-inducedarthritis. The most important results of the studies outlined in this review show that nanoparticles can inhibit the expression and the release of some pro-inflammatory mediators and proteolytic enzymes, and the activity of different transcriptional factors in vitro, as well as decrease the uric acid levels in several studies of in vitro and in vivo models of gout, which show interesting results in terms of decreasing the amount of crystals and tissue damage, respectively. In view of their multiple beneficial effects, nanoparticles can be considered a valuable therapy that contributes to the pharmacological treatment in crystalinduced arthritis.

Calcium-Containing Crystals and Osteoarthritis: an Unhealthy Alliance

PURPOSE OF REVIEW

Osteoarthritis (OA) is the most common form of joint disease globally and is associated with significant morbidity and disability. Increasing evidence points to an important inflammatory component in the development and progression of OA. The precise pathways involved in OA inflammatory processes remain to be clarified. Basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPP) crystals can induce inflammation and arthritis and recent studies point to a potential pathogenic role in OA. In the light of this evidence, we explore the relationship and potential mechanistic pathways linking calcium-containing crystals and OA.

RECENT FINDINGS

CPP crystals induce inflammation through the NLRP3 inflammasome while BCP crystals mediate both NLRP3 dependent and independent effects. BCP crystals have been demonstrated to induce key mitogenic and inflammatory pathways and contribute to cartilage degradation. Calcium-containing crystals induce key inflammatory pathways and may represent an attractive novel target in OA, a condition devoid of effective treatments.

Calcium-phosphate complex increased during subchondral bone remodeling affects earlystage osteoarthritis

An activation of osteoclasts and subchondral bone remodeling is a major histologic feature of early-stage osteoarthritis (OA), which can be accompanied by an increase of calcium (Ca) and phosphate (Pi) level in the subchondral milieu. Considering articular cartilage gets most of nutrition from subchondral bone by diffusion, these micro-environmental changes in subchondral bone can affect the physiology of articular chondrocytes. Here, we have shown that Ca is increased and co-localized with Pi in articular cartilage of early-stage OA. The Ca-Pi complex increased the production of MMP-3 and MMP-13 in the hypertrophic chondrocytes, which was dependent on nuclear factor-kappa B (NF-kB), p38 and extracellular signal-regulated kinase (Erk) 1/2 mitogen-activated protein (MAP) kinase and Signal transducer and activator of transcription 3 (STAT3) signaling. The Ca-Pi complexes increased the expression of endocytosis markers, and the inhibition of the formation of the Ca-Pi complex ameliorated the Ca-Pi complex-mediated increases of MMPs expression in hypertrophic chondrocytes. Our data provide insight regarding the Ca-Pi complex as a potential catabolic mediator in the subchondral milieu and support the pathogenic role of subchondral bone in the early stages of cartilage degeneration.

Association between ultrasound-detected synovitis and knee pain: a population-based case-control study with both cross-sectional and follow-up data

BACKGROUND

An important role for synovial pathology in the initiation and progression of knee osteoarthritis has been emphasised recently. This study aimed to examine whether ultrasonography-detected synovial changes associate with knee pain (KP) in a community population.

METHODS

A case-control study was conducted to compare people with early KP (n = 298), established KP (n = 100) or no KP (n = 94) at baseline. Multinomial logistic regression was used to estimate the odds ratio (OR) and 95% confidence interval (CI) between groups adjusted for radiographic osteoarthritis (ROA) severity and other confounding factors. After 1 year, 255 participants with early and established KP completed the follow-up questionnaire for changes in KP. Logistic regression with adjustment was used to determine predictors of KP worsening.

RESULTS

At baseline, effusion was associated with early KP (OR 2.64, 95% CI 1.57-4.45) and established KP (OR 5.07, 95% CI 2.74-9.38). Synovial hypertrophy was also associated with early KP (OR 5.43, 95% CI 2.12-13.92) and established KP (OR 13.27, 95% CI 4.97-35.43). The association with effusion diminished when adjusted for ROA. Power Doppler signal was uncommon (early KP 3%, established KP 2%, controls 0%). Baseline effusion predicted worsening of KP at 1 year (OR 1.95, 95% CI 1.05-3.64). However, after adjusting for ROA, the prediction was insignificant (adjusted OR 0.95, 95% CI 0.44-2.02).

CONCLUSIONS

Ultrasound effusion and synovial hypertrophy are associated with KP, but only effusion predicts KP worsening. However, the association/prediction is not independent from ROA. Power Doppler signal is uncommon in people with KP. Further study is needed to understand whether synovitis is directly involved in different types of KP.

Microcalcification of lumbar spine intervertebral discs and facet joints is associated with cartilage degeneration, but differs in prevalence and its relation to age

Cartilage calcification (CC) is associated with degeneration in non-vertebral joints, but little is known about CC and lumbar vertebral joints. The goal of this study was to analyze the prevalence of CC in lumbar facet joints (FJ) and intervertebral discs (IVD) and its relation to cartilage degeneration and age in a non-selected cohort of the general population. The segment L4/5 of 85 consecutive donors (mean age 61.9 years) was analyzed by high-resolution imaging digital-contact radiography (DCR). Quantification was achieved by measuring CC in % of total cartilage area. Histological degeneration of FJs and IVDs was determined by OARSI and Boos scores. Prevalence of CC was 36.5% for FJ (95%CI (0.26, 0.48)) and 100% for IVD (95%CI (0.96, 1.00)). The amount of IVD CC (3.36% SD ± 7.14) was 16.3 times higher (p < 0.001) than that of the FJ (0.23% SD ± 0.53) and independent of each other (p = 0.07). The amount of FJ CC correlated significantly with FJ and IVD degeneration (FJ r = 0.44, p = 0.01, IVD r = 0.49, p = 0.006) while the amount of IVD CC correlated only with IVD degeneration (r = 0.54, p < 0.001). Age correlated with IVD CC (r_s  = 0.35, p < 0.001), but not FJ CC (r_s  = 0.04, p = 0.85). We conclude that IVD fibrocartilage is particularly prone to calcification. A causal relationship between lumbar CC and degeneration is possible, but the clear differences in IVD fibrocartilage CC and FJ synovial joint CC in regard to prevalence and in relation to age point to a differential role of CC in single compartments of the respective motion segment in lumbar spine degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2692-2699, 2017.

What drives osteoarthritis?-synovial versus subchondral bone pathology

Subchondral bone and the synovium play an important role in the initiation and progression of OA. MRI often permits an early detection of synovial hypertrophy and bone marrow lesions, both of which can precede cartilage damage. Newer imaging modalities including CT osteoabsorptiometry and hybrid SPECT-CT have underlined the importance of bone in OA pathogenesis. The subchondral bone in OA undergoes an uncoupled remodelling process, which is notably characterized by macrophage infiltration and osteoclast formation. Concomitant increased osteoblast activity leads to spatial remineralization and osteosclerosis in end-stage disease. A plethora of metabolic and mechanical factors can lead to synovitis in OA. Synovial tissue is highly vascularized and thus exposed to systemic influences such as hypercholesterolaemia or low grade inflammation. This review aims to describe the current understanding of synovitis and subchondral bone pathology and their connection in OA.

Comparison of Meniscal Cell-Mediated and Chondrocyte-Mediated Calcification

Background:

Chondrocytes have been traditionally thought to be responsible for calcium crystal deposits within osteoarthritic knees. Increasing recent experimental evidence suggests that menisci may also play a role. However, the calcifying potential of chondrocytes and meniscal cells derived from same OA patients, and the genes associated with meniscal calcification have never been fully examined.

Objective:

Examine and compare the calcifying potential of articular chondrocytes and meniscal cells derived from same OA patients and identify the calcium crystal type(s) and selected gene expression in OA menisci.

Methods:

Chondrocytes and meniscal cells were isolated from articular cartilage and menisci of OA patients undergoing total knee arthroplasty. Chondrocyte- and meniscal cell-mediated calcification was examined using both monolayer and micromass culture-based assays. Crustal types were examined with histological staining. Levels of Type X Collagen, MMP-13, and ANKH in OA menisci were examined using immunohistochemistry.

Results:

Primary human OA meniscal cells produced calcified deposits at a similar rate compared to OA chondrocytes in-vitro. Histological examinations indicate that both BCP crystals and CPPD crystals are present in the meniscal tissue. Type X collagen, MMP-13, and ANKH were found in human OA menisci and their levels increased with OA severity. In addition, type X collagen was co-localized with calcium crystals.

Conclusion:

These findings suggest that OA meniscal cells have a similar calcifying potential as OA chondrocytes, supporting a pathogenic role of OA menisci in OA.

Increased expression of damage-associated molecular patterns (DAMPs) in osteoarthritis of human knee joint compared to hip joint

Osteoarthritis (OA) is a degenerative disease characterized by the destruction of cartilage. The greatest risk factors for the development of OA include age and obesity. Recent studies suggest the role of inflammation in the pathogenesis of OA. The two most common locations for OA to occur are in the knee and hip joints. The knee joint experiences more mechanical stress, cartilage degeneration, and inflammation than the hip joint. This could contribute to the increased incidence of OA in the knee joint. Damage-associated molecular patterns (DAMPs), including high-mobility group box-1, receptor for advanced glycation end products, and alarmins (S100A8 and S100A9), are released in the joint in response to stress-mediated chondrocyte and cartilage damage. This facilitates increased cartilage degradation and inflammation in the joint. Studies have documented the role of DAMPs in the pathogenesis of OA; however, the comparison of DAMPs and its influence on OA has not been discussed. In this study, we compared the DAMPs between OA knee and hip joints and found a significant difference in the levels of DAMPs expressed in the knee joint compared to the hip joint. The increased levels of DAMPs suggest a difference in the underlying pathogenesis of OA in the knee and the hip and highlights DAMPs as potential therapeutic targets for OA in the future.

Detection of Calcium Crystals in Knee Osteoarthritis Synovial Fluid: A Comparison Between Polarized Light and Scanning Electron Microscopy

BACKGROUND

The identification of calcium crystals in synovial fluid (SF) of patients with osteoarthritis (OA) represents an important step in understanding the role of these crystals in synovial inflammation and disease progression.

OBJECTIVES

This study aimed to investigate the presence of calcium pyrophosphate (CPP) and basic calcium phosphate (BCP) crystals in SF collected from patients with symptomatic knee OA by scanning electron microscopy (SEM) coupled to x-ray energy dispersive spectroscopy, compensated polarized light microscopy (CPLM), and alizarin red staining.

METHODS

Seventy-four patients with knee OA were included in the study. Synovial fluid samples were collected after arthrocentesis and examined under CPLM for the assessment of CPP crystals. Basic calcium phosphate crystals were evaluated by alizarin red staining. All the samples were examined by SEM. The concordance between the 2 techniques was evaluated by Cohen κ agreement coefficient.

RESULTS

Calcium pyrophosphate and BCP crystals were found, respectively, in 23 (31.1%) and 13 (17.5%) of 74 OA SFs by SEM analysis. Calcium pyrophosphate crystals were identified in 23 (31.1%) of 74 samples by CPLM, whereas BCP crystals were suspected in 27 (36.4%) of 74 samples. According to κ coefficient, the concordance between CPLM and SEM was 0.83 for CPP, and that between alizarin red and SEM was 0.68 for BCP.

CONCLUSIONS

The results of our study showed a high level of concordance between the 2 microscope techniques as regards CPP crystal identification and a lower agreement for BCP crystals. Although this finding highlights the difficulty in identifying BCP crystals by alizarin red staining, the use of SEM remains unsuitable to apply in the clinical setting. Because of the in vitro inflammatory effect of BCP crystals, further work on their analysis in SF could provide important information about the OA process.

Does long term colchicine prevent degradation of collagen fiber network in osteoarthritis?

AIM

Several studies have shown that colchicine exhibits an improvement in the symptoms of knee osteoarthritis (OA) but its effect on disease progression is unknown. To clarify the mechanism of action this study was done to see if colchicine prevents degradation of collagen fiber network in OA by studying serum cartilage oligomeric matrix protein (COMP) levels, a marker of cartilage turnover, over a period of 1 year.

METHODS

Seventy-five patients received colchicine plus paracetamol and 75 received placebo alone for the same time period. Serum COMP assays were done at baseline, 2 months and 1 year by enzyme-linked immunosorbent assay. These markers were compared between visits using repeated measures analysis of variance.

RESULTS

Serum COMP levels in the paracetamol-alone group did not show significant change between baseline and 2 months; however, there was a significant increase in serum COMP levels from 2 months to 1 year, suggesting increased uncoupling of proteoglycans from collagen and disease progression. No such change was seen in the colchicine group, signifying lack of progression of disease in this group.

CONCLUSION

Colchicine may act as a disease-modifying agent in OA.

Articular cartilage calcification of the hip and knee is highly prevalent, independent of age but associated with histological osteoarthritis: evidence for a systemic disorder

OBJECTIVES

Based on the concept of a systemic predisposition for articular cartilage calcification (CC), the aim of this study was to determine the prevalence and amount of bilateral CC of hip and knee joints in an unselected sample cohort by high-resolution digital contact radiography (DCR) and to analyze the association of CC with histological OA.

METHODS

Both hip and knee joints of 87 donors (48 m and 39 f; mean age 62) were analyzed by DCR in this post-mortem study of an unselected cohort of donors. Histological OA (OARSI) of the main load bearing area of femoral heads and medial femoral condyles was determined.

RESULTS

The prevalence of CC of the femoral head was 96.6%, of the knee 94.3%. Bilateral calcification was detected in 79.3% of hips and 86.2% of knees. Concomitant CC of all four joints was detected in 69.0% of donors. There was no difference between the amount of CC of hips and knees (P = 0.47). The amount of CC of any given hip or knee correlated with that of the contralateral hip (r_s = 0.54, P < 0.001) or knee (r_s = 0.50, P < 0.001). There was a correlation between the amount of CC and histological OA (hips r_s = 0.48, P < 0.001, knees r_s = 0.30, P = 0.004), but not between CC and age (hips r_s = -0.09, P = 0.42; knees r_s = 0.10, P = 0.34).

CONCLUSIONS

These data support the concept that articular CC occurs as the result of a systemic disorder. CC appears to be an early element of hip and knee OA pathogenesis independent of age.

Hyaline cartilage calcification of the first metatarsophalangeal joint is associated with osteoarthritis but independent of age and BMI

Background

Hyaline cartilage calcification (CC) is associated with osteoarthritis (OA) in hip and knee joints. The first metatarsophalangeal joint (1^stMTPJ) is frequently affected by OA, but it is unclear if CC occurs in the 1^stMTPJ. The aim of the present study was to analyze the prevalence of CC of the 1^stMTPJ in the general population by high-resolution digital contact radiography (DCR) and to determine its association with histological OA severity, age and body mass index (BMI).

Methods

168 metatarsal heads of 84 donors (n = 47 male, n = 37 female; mean age 62.73 years, SD ±18.8, range 20–93) were analyzed by DCR for the presence of CC. Histological OA grade (hOA) by OARSI was analyzed in the central load-bearing zone of the first metatarsal head (1^st MH). Structural equation modeling (SEM) was performed to analyze the interrelationship between CC, hOA, age and BMI.

Results

The prevalence of CC of 1^stMH was 48.8 % (41/84) (95 %-CI [37.7 %, 60.0 %]), independent of the affected side (p = 0.42), gender (p = 0.41) and BMI (p = 0.51). The mean amount of CC of one MH correlated significantly with that of the contralateral side (r_s = 0.4, 95 %-CI [0.26, 0.52], p < 0.001). The mean amount of CC (in % of total cartilage area) of the MH correlated significantly with the severity of hOA (r_s = 0.51, 95 %-CI [0.32, 0.65], p < 0.001). SEM revealed significant associations between CC and hOA (r = 0.74, p < 0.001) and between hOA and age (β = 0.62, p = 0.001), but not between CC and age (p = 0.15). There was no significant influence of BMI on either CC (p = 0.37) or hOA (p = 0.16).

Conclusion

The observation that CC of the 1^stMH is significantly associated with the severity of OA but independent of age and BMI, suggests an intimate relationship between CC and the pathogenesis of OA, the exact nature of which will have to be explored by future studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1324-0) contains supplementary material, which is available to authorized users.

Articular cartilage calcification of the humeral head is highly prevalent and associated with osteoarthritis in the general population

Articular cartilage calcification is considered a pathological albeit incompletely understood process which is known to be associated with osteoarthritis of the knee and hip. The goal of this study was to determine the prevalence of articular cartilage calcification of the shoulder as a non-weight-bearing joint and to analyze the interrelationship of calcification with age and histological severity of shoulder osteoarthritis in the general population. In a cross-sectional study of 180 humeral heads from 90 donors (n = 49 male, n = 41 female; mean age 62.7 years [20-93]), cartilage calcification of the humeral head was quantified by digital contact radiography (DCR). Histological OA grade (OARSI) was determined and structural equation modeling (SEM) was used to analyze the interrelationship of cartilage calcification, OARSI and age. The prevalence of articular cartilage calcification was 98.9% (95%CI: [93.96%, 99.97%]) and was independent of gender (p = 0.55). Cartilage calcification of one shoulder correlated significantly with that of the contralateral side (r = 0.61, 95%CI: [0.46, 0.73], p < 0.001). SEM demonstrated significant associations between histological OA grade and cartilage calcification (r = 0.55, p = 0.039), between histological OA grade and age (β = 0.59, p < 0.001) but not between age and cartilage calcification (β = 0.24, p = 0.116). In conclusion, the prevalence of shoulder cartilage calcification in the general population is higher than anticipated. The high prevalence, its concomitant bilateral manifestation and the association between the amount of cartilage calcification and OA severity, but not age, suggest that cartilage calcification is a systemically driven process with early onset in life and may be a causative factor in the pathogenesis of OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1984-1990, 2016.

Low-grade inflammation as a key mediator of the pathogenesis of osteoarthritis

Osteoarthritis (OA) has long been viewed as a degenerative disease of cartilage, but accumulating evidence indicates that inflammation has a critical role in its pathogenesis. Furthermore, we now appreciate that OA pathogenesis involves not only breakdown of cartilage, but also remodelling of the underlying bone, formation of ectopic bone, hypertrophy of the joint capsule, and inflammation of the synovial lining. That is, OA is a disorder of the joint as a whole, with inflammation driving many pathologic changes. The inflammation in OA is distinct from that in rheumatoid arthritis and other autoimmune diseases: it is chronic, comparatively low-grade, and mediated primarily by the innate immune system. Current treatments for OA only control the symptoms, and none has been FDA-approved for the prevention or slowing of disease progression. However, increasing insight into the inflammatory underpinnings of OA holds promise for the development of new, disease-modifying therapies. Indeed, several anti-inflammatory therapies have shown promise in animal models of OA. Further work is needed to identify effective inhibitors of the low-grade inflammation in OA, and to determine whether therapies that target this inflammation can prevent or slow the development and progression of the disease.

Use of the Microparticle Nanoscale Silicon Dioxide as an Adjuvant To Boost Vaccine Immune Responses against Influenza Virus in Neonatal Mice

Neonates are at a high risk of infection, but vaccines are less effective in this age group; tailored adjuvants could potentially improve vaccine efficacy. Increased understanding about danger sensing by the innate immune system has led to the rational design of novel adjuvants. But differences in the neonatal innate immune response, for example, to Toll-like receptor (TLR) agonists, can reduce the efficacy of these adjuvants in early life. We therefore targeted alternative danger-sensing pathways, focusing on a range of compounds described as inflammasome agonists, including nanoscale silicon dioxide (NanoSiO2), calcium pyrophosphate dihydrate (CPPD) crystals, and muramyl tripeptide (M-Tri-DAP), for their ability to act as adjuvants.In vitro, these compounds induced an interleukin 1-beta (IL-1β) response in the macrophage-like cell line THP1.In vivo, adult CB6F1 female mice were immunized intramuscularly with H1N1 influenza vaccine antigens in combination with NanoSiO2, CPPD, or M-Tri-DAP and subsequently challenged with H1N1 influenza virus (A/England/195/2009). The adjuvants boosted anti-hemagglutinin IgG and IgA antibody levels. Both adult and neonatal animals that received NanoSiO2-adjuvanted vaccines lost significantly less weight and recovered earlier after infection than control animals treated with antigen alone. Administration of the adjuvants led to an influx of activated inflammatory cells into the muscle but to little systemic inflammation measured by serum cytokine levels. Blocking IL-1β or caspase 1 in vivo had little effect on NanoSiO2 adjuvant function, suggesting that it may work through pathways other than the inflammasome. Here we demonstrate that NanoSiO2 can act as an adjuvant and is effective in early life.

IMPORTANCE

Vaccines can fail to protect the most at-risk populations, including the very young, the elderly, and the immunocompromised. There is a gap in neonatal immunity between the waning of maternal protection and routine infant immunization schedules, exacerbated by the failure of vaccines to work in the first months of life. One approach is to design age-specific formulations, with more-effective adjuvants, based on our understanding of the nature of the neonatal immune response. We chose to target the inflammasome, a molecular complex capable of detecting infection and cell damage and of triggering IL-1β-driven inflammation. We screened a range of compounds in vitro and in vivo and identified three lead candidates: NanoSiO2, CPPD, and M-Tri-DAP. Of these, NanoSiO2 was the most effective and boosted the anti-influenza virus response in both adult and neonatal mice. This finding is important for the development of age-specific vaccines, designed using our knowledge of the neonatal immune response.

Gla-rich protein is involved in the cross-talk between calcification and inflammation in osteoarthritis

Osteoarthritis (OA) is a whole-joint disease characterized by articular cartilage loss, tissue inflammation, abnormal bone formation and extracellular matrix (ECM) mineralization. Disease-modifying treatments are not yet available and a better understanding of osteoarthritis pathophysiology should lead to the discovery of more effective treatments. Gla-rich protein (GRP) has been proposed to act as a mineralization inhibitor and was recently shown to be associated with OA in vivo. Here, we further investigated the association of GRP with OA mineralization-inflammation processes. Using a synoviocyte and chondrocyte OA cell system, we showed that GRP expression was up-regulated following cell differentiation throughout ECM calcification, and that inflammatory stimulation with IL-1β results in an increased expression of COX2 and MMP13 and up-regulation of GRP. Importantly, while treatment of articular cells with γ-carboxylated GRP inhibited ECM calcification, treatment with either GRP or GRP-coated basic calcium phosphate (BCP) crystals resulted in the down-regulation of inflammatory cytokines and mediators of inflammation, independently of its γ-carboxylation status. Our results strengthen the calcification inhibitory function of GRP and strongly suggest GRP as a novel anti-inflammatory agent, with potential beneficial effects on the main processes responsible for osteoarthritis progression. In conclusion, GRP is a strong candidate target to develop new therapeutic approaches.

The human knee: A window on the microvasculature

In synovial joints, the lining cells do not have tight junctions with their neighboring cells and they have no underlying basement membrane. Therefore, the synovial fluid within the articular cavity is continuous with the interstitial fluid of the synovial intima. These features, combined with ready access to the space via arthrocentesis, permit quantitative studies of microvascular function in the knees of unanesthetized, volunteer, human subjects both with and without chronic arthritis. This brief article reviews the principal findings of such work over ∼40 years at the University of Washington. Examined variables include bidirectional fenestral diffusion of small solutes, effective blood flow, lymphatic drainage, and endothelial pore size and permeability. The latter work introduced a new method using gel filtration chromatography of paired synovial fluid (SF) and serum (S) to obtain essentially continuous SF/S ratios over a range of radii between 1 and 12 nanometers.

IL-1ß and IL-8 are scavenged by the hexadecylamide derivative of hyaluronic acid: a new mechanism

This study aimed to investigate, using an in vitro model, the mechanisms involved in the effects linked to a novel hexadecylamide derivative of hyaluronic acid (HA), HYADD®4 (HS), on some inflammatory aspects related to the osteoarthritis process. The human leukemic monocytic cell line THP-1 was stimulated with calcium pyrophosphate (CPP) crystals or lipopolysaccaride (LPS) and cultured in the presence of HS or two unmodified HAs (500-730 kDa and >1500 kDa, respectively). The effects of the three HA derivatives were compared by examining the inhibition of IL-1ß and IL-8 release, the phagocytic capacity of THP-1, and HA's physical interference with the cytokines and their biological activity. Adding HS simultaneously with the stimuli led to a marked (nearly 100%) decrease in cytokine release and biological activity with respect to the two unmodified HAs. The effect was not altered when a CD44 function-blocking monoclonal antibody was used. Incubation of the three derivatives with IL-1ß and IL-8 led to a reduced bioavailability of the cytokines in the medium in the presence of HS but not of unmodified HA. This study examines a novel mechanism inhibiting cytokine bioactivity. The HA hexadecylamide derivative was found to suppress, in vitro, the inflammatory response induced by CPP crystals and LPS by reducing the bioavailability of the two cytokines that were analyzed.

Cellular and molecular mechanisms of cartilage damage and repair

Cartilage breakdown is the disabling outcome of rheumatic diseases, whether prevalently inflammatory such as rheumatoid arthritis or prevalently mechanical such as osteoarthritis (OA). Despite the differences between immune-mediated arthritides and OA, common mechanisms drive cartilage breakdown. Inflammation, chondrocyte phenotype and homeostatic mechanisms have recently been the focus of research and will be summarised in this review.

Calcium phosphate particulates increase friction in the rat knee joint

OBJECTIVE

Basic calcium phosphate (BCP) particulates are commonly found in cartilage and synovial fluid of osteoarthritis (OA) joints with the amount of BCP correlating with knee OA severity. How cartilage mineralization affects joint degeneration has yet to be determined. The objective of this study was to determine whether BCP in the synovial fluid affects the rat knee joint coefficient of friction (COF).

METHODS

The COFs of knees from both hind limbs of four mature male rats were measured post mortem using a pendulum apparatus with an infrared tracking system. The three conditions evaluated were (1) the naïve state, (2) after the injection of 100 μL of phosphate buffered saline (PBS) (sham) and (3) after the injection of 100 μL of a 1 mg/mL BCP suspension. The decrease in the pendulum amplitude (decay) was fit using two friction models: (1) a one parameter Stanton linear decay model and (2) a two parameters combination Stanton linear decay and viscous damping exponential decay model.

RESULTS

The COF increased 17.6% after injection of BCP compared to the naïve (P = 0.0012) and 16.0% compared to the saline injected (P = 0.0018) joints as derived from the one parameter model. The COF did not differ between naïve and saline injected joints. Results from the two parameters model showed a similar increase in COF after injection of BCP while the viscous damping was not significantly different between conditions.

CONCLUSIONS

The increased joint friction with BCP particulates suggests BCPs may play a role in articular surface degradation and OA development.

Arthroscopic washout of the knee: a procedure in decline

BACKGROUND

Osteoarthritis (OA) of the knee is a chronic, progressive condition which often requires surgical intervention. The evidence for the benefits of arthroscopic debridement or washout for knee OA is weak and arthroscopy is currently only indicated in the UK if there is a history of mechanical locking of the knee.

OBJECTIVES

To investigate whether there has been any change in the number of arthroscopies performed in the UK since the 2007 NICE guidance on knee arthroscopy and the 2008 Cochrane review of arthroscopic debridement for OA of the knee.

METHODS

We interrogated data from the Hospital Episodes Statistics (HES) database with Office of Population Censuses and Surveys-4 (OPSC-4) codes pertaining to therapeutic endoscopic operations in the 60-74 year old and 75 and over age groups.

RESULTS

The number of arthroscopic knee interventions in the UK decreased overall from 2000 to 2012, with arthroscopic irrigations decreasing the most by 39.6 per 100,000 population (80%). However, the number of arthroscopic meniscal resections increased by 105.3 per 100,000 (230%) population. These trends were mirrored in both the 60-74 and 75 and over age groups.

CONCLUSIONS

Knee arthroscopy in the 60-74 and 75 and over age groups appears to be decreasing but there is still a large and increasing number of arthroscopic meniscal resections being performed.

Comorbidities in patients with crystal diseases and hyperuricemia

Crystal arthropathies are among the most common causes of painful inflammatory arthritis. Gout, the most common example, has been associated with cardiovascular and renal disease. In recent years, evidence for these associations and those involving other comorbidities, such as the metabolic syndrome, have emerged, and the importance of asymptomatic hyperuricemia has been established. In this review, an update on evidence, both experimental and clinical, is presented, and associations between hyperuricemia, gout, and several comorbidities are described. Causality regarding calcium pyrophosphate arthropathy and associated comorbidities is also reviewed.