Uncoupling of type II collagen synthesis and degradation predicts progression of joint damage in patients with knee osteoarthritis

Phenotype and energy metabolism differ between osteoarthritic chondrocytes from male compared to female patients: Implications for sexual dimorphism in osteoarthritis development?

OBJECTIVES

The prevalence and severity of knee osteoarthritis (OA) are greater in females than males. The purpose of this study was to determine whether there is an underlying difference in the biology of OA chondrocytes between males and females.

METHODS

Chondrocytes were obtained following knee arthroplasty from male and female patients with primary OA. Phenotype marker expression, glucose and fat consumption, and rates of glycolysis and oxidative phosphorylation were compared between females and males. RNAi was used to determine the consequences of differential expression of Sry-box transcription factor 9 (SOX9) and PGC1α between males and females.

RESULTS

OA chondrocytes from male donors showed elevated ribonucleic acid (RNA) and protein levels of SOX9, elevated COL2A1 protein synthesis, higher glucose consumption, and higher usage of glycolysis compared to females. OA chondrocytes from females had higher PGC1α protein levels, higher fat consumption, and higher oxidative energy metabolism than males. Knockdown of SOX9 reduced expression of COL2A1 to a greater extent in male OA chondrocytes than females whereas knockdown of PGC1α reduced COL2A1 expression in females but not males. Expression of ACAN and the glycolytic enzyme PGK1 was also reduced in males but not females following SOX9 knockdown.

CONCLUSIONS

OA chondrocyte phenotype and energy metabolism differ between males and females. Our results indicate transcriptional control of COL2A1 differs between the two. Differences in chondrocyte biology between males and females imply the underlying mechanisms involved in OA may also differ, highlighting the need to consider sex and gender when investigating pathogenesis and potential treatments for OA.

Current knowledge of hybrid nanoplatforms composed of exosomes and organic/inorganic nanoparticles for disease treatment and cell/tissue imaging

Exosome-nanoparticle hybrid nanoplatforms, can be prepared by combining exosomes with different types of nanoparticles. The main purpose of combining exosomes with nanoparticles is to overcome the limitations of using each of them as drug delivery systems. Using nanoparticles for drug delivery has some limitations, such as high immunogenicity, poor cellular uptake, low biocompatibility, cytotoxicity, low stability, and rapid clearance by immune cells. However, using exosomes as drug delivery systems also has its own drawbacks, such as poor encapsulation efficiency, low production yield, and the inability to load large molecules. These limitations can be addressed by utilizing hybrid nanoplatforms. Additionally, the use of exosomes allows for targeted delivery within the hybrid system. Exosome-inorganic/organic hybrid nanoparticles may be used for both therapy and diagnosis in the future. This may lead to the development of personalized medicine using hybrid nanoparticles. However, there are a few challenges associated with this. Surface modifications, adding functional groups, surface charge adjustments, and preparing nanoparticles with the desired size are crucial to the possibility of preparing exosome-nanoparticle hybrids. Additional challenges for the successful implementation of hybrid platforms in medical treatments and diagnostics include scaling up the manufacturing process and ensuring consistent quality and reproducibility across various batches. This review focuses on various types of exosome-nanoparticle hybrid systems and also discusses the preparation and loading methods for these hybrid nanoplatforms. Furthermore, the potential applications of these hybrid nanocarriers in drug/gene delivery, disease treatment and diagnosis, and cell/tissue imaging are explained.

Determinants of joint effusion in tarsocrural osteochondrosis of yearling Standardbred horses

Tarsocrural osteochondrosis (OCD) is a developmental orthopedic disease commonly affecting young Standardbreds, with different fragment localization and size. Clinically, it is characterized by variable synovial effusion in the absence of lameness, whose determinants are ill-defined. We hypothesized that localization and physical characteristics of the osteochondral fragments like dimensions, multifragmentation, and instability influence joint effusion and correlate with synovial markers of cartilage degradation and inflammation. Clinical data, synovial fluid and intact osteochondral fragments were collected from 79 Standardbred horses, aged between 12 and 18 months, operated for tarsocrural OCD. The severity of tarsocrural joint effusion was assessed semi-quantitatively. The osteochondral fragment site was defined radiographically at the distal intermediate ridge of the tibia (DIRT), medial malleolus (MM) of the tibia, and/or lateral trochlear ridge (LTR) of the talus. Size, stability, and arthroscopic appearance (unique or multi-fragmented aspect) of the fragments were determined intra-operatively. Synovial concentrations of C-terminal cross-linked telopeptides of type II collagen (CTX-II), leukotriene B4 (LTB4), and prostaglandin E2 (PGE2) were quantified. Tarsocrural synovial effusion was significantly affected by localization and stability of the fragments, with MM-located and unstable fragments being associated with highest joint effusion. Concentrations of CTX-II, LTB4, and PGE2 positively correlated with the severity of synovial effusion. This study underlines characteristics of the osteochondral fragments determining higher synovial effusion in OCD-affected tarsocrural joints and suggests both inflammation and extra-cellular matrix degradation are active processes in OCD pathology.

Plasma Cartilage Acidic Protein 1 Measured by ELISA Is Associated With the Progression to Total Joint Replacement in Postmenopausal Women

OBJECTIVE

To investigate the association of plasma cartilage acidic protein 1 (CRTAC1), a novel biochemical marker of osteoarthritis (OA), and total joint replacement (TJR) in postmenopausal women.

METHODS

The association of plasma CRTAC1 with the incidence of TJR was investigated in a prospective cohort including 478 postmenopausal women. A total of 38 women underwent a TJR for OA during a median follow-up of 18 years. Every one of the TJR cases were age- and BMI (kg/m2)-matched with 2 controls with no TJR from the same cohort. Plasma CRTAC1 was measured before TJR. The association between CRTAC1 and TJR incidence was investigated by conditional logistic regression.

RESULTS

Increased CRTAC1 was associated with a higher risk of TJR with an odds ratio (OR) of 1.80 (95% CI 1.11-2.92) for 1 SD increase, which remained significant after adjusting for Western Ontario and McMaster Universities Osteoarthritis Index, knee OA baseline severity (Kellgren-Lawrence grade), hip OA, and hip bone mineral density. Urinary crosslinked C-telopeptide of type II collagen (CTX-II) was also associated with a higher risk of TJR with an adjusted OR of 1.83 (95% CI 1.11-3.00). When CRTAC1 and CTX-II were included in the same model, both markers were significantly associated with TJR with similar ORs.

CONCLUSION

CRTAC1 is a new risk indicator of TJR for OA in postmenopausal women. Combined with knee and hip OA and CTX-II, it may help to identify subjects at risk for TJR.

Changes in the Subchondral Bone, Visfatin, and Cartilage Biomarkers after Pharmacological Treatment of Experimental Osteoarthritis with Metformin and Alendronate

Subchondral bone that has intense communication with the articular cartilage might be a potential target for pharmacological treatment in the early stages of osteoarthritis (OA). Considering the emerging data about the role of adipokines in the pathogenesis of OA, the administration of drugs that influence their level is also intriguing. Metformin and alendronate were administered in mice with collagenase-induced OA (CIOA) as a monotherapy and in combination. Safranin O staining was used for the assessment of changes in subchondral bone and articular cartilage. Before and after treatment, serum levels of visfatin and biomarkers of cartilage turnover (CTX-II, MMP-13, and COMP) were assessed. In the current study, the combined administration of alendronate and metformin in mice with CIOA led to the protection against cartilage and subchondral bone damage. In mice with CIOA, metformin led to a decrease in visfatin level. In addition, treatment with metformin, alendronate, or their combination lowered the level of cartilage biomarkers (CTX-II and COMP), while the level of MMP-13 was not influenced. In conclusion, personalized combination treatment in OA according to clinical phenotype, especially in the early stages of the disease, might lead to the identification of a successful disease-modifying therapeutic protocol in OA.

Differential Effects of Hypoxia versus Hyperoxia or Physoxia on Phenotype and Energy Metabolism in Human Chondrocytes from Osteoarthritic Compared to Macroscopically Normal Cartilage

Chondrocyte phenotype and energy metabolism are altered in osteoarthritis (OA). However, most studies characterising the change in human chondrocyte behaviour in OA have been conducted in supraphysiological oxygen concentrations. The purpose of this study was to compare phenotype and energy metabolism in chondrocytes from macroscopically normal (MN) and OA cartilage maintained in 18.9% (standard tissue culture), 6% (equivalent to superficial zone of cartilage in vivo) or 1% oxygen (equivalent to deep zone of cartilage in vivo). MMP13 production was higher in chondrocytes from OA compared to MN cartilage in hyperoxia and physoxia but not hypoxia. Hypoxia promoted SOX9, COL2A1 and ACAN protein expression in chondrocytes from MN but not OA cartilage. OA chondrocytes used higher levels of glycolysis regardless of oxygen availability. These results show that differences in phenotype and energy metabolism between chondrocytes from OA and MN cartilage differ depending on oxygen availability. OA chondrocytes show elevated synthesis of cartilage-catabolising enzymes and chondrocytes from MN cartilage show reduced cartilage anabolism in oxygenated conditions. This is relevant as a recent study has shown that oxygen levels are elevated in OA cartilage in vivo. Our findings may indicate that this elevated cartilage oxygenation may promote cartilage loss in OA.

Intra-osseous infiltration of adipose mesenchymal stromal cells and plasma rich in growth factors to treat acute full depth cartilage defects in a rabbit model: Serum osteoarthritis biomarkers and macroscopical assessment

Introduction

Intra-articular infiltration of plasma rich in growth factors (PRGF) and adipose mesenchymal stromal cells (AMSCs) are known to inhibit osteoarthritis progression. However, in severely affected patients, the treatment cannot reach the deeper layers of the articular cartilage; thus, its potential is limited. To overcome this limitation, intra-osseous infiltrations have been suggested. The purpose of this study is to assess the impact of intra-osseous infiltration therapies on serum biomarkers of osteoarthritis and to assess cartilage regeneration macroscopically.

Materials and methods

A total of 80 rabbits were divided into four groups based on the intra-osseous treatment administered on the day of surgery: control, PRGF, AMSCs and a combination of PRGF + AMSCs. In addition, all groups received a single intra-articular administration of PRGF on the same day. Serum biomarker levels were measured before infiltration and 28-, 56-, and 84-days post infiltration, and macroscopical assessment was conducted at 56- and 84-days follow-up post infiltration.

Results

In the PRGF + AMSCs group, significantly lower concentrations of hyaluronic acid and type II collagen cleavage neoepitope were recorded at all time points during the study, followed by PRGF, AMSCs and control groups. Regarding macroscopical assessment, lower scores were obtained in PRGF + AMSCs group at all study times.

Discussion

The results suggest that the combination of intra-articular PRGF with intra-osseous PRGF or AMSCs achieves better results in rabbits with acute chondral defects and that intra-osseous infiltration is a safe procedure.

The current state of the osteoarthritis drug development pipeline: a comprehensive narrative review of the present challenges and future opportunities

In this narrative review article, we critically assess the current state of the osteoarthritis (OA) drug development pipeline. We discuss the current state-of-the-art in relation to the development and evaluation of candidate disease-modifying OA drugs (DMOADs) and the limitations associated with the tools and methodologies that are used to assess outcomes in OA clinical trials. We focus on the definition of DMOADs, highlight the need for an updated definition in the form of a consensus statement from all the major stakeholders, including academia, industry, regulatory agencies, and patient organizations, and provide a summary of the results of recent clinical trials of novel DMOAD candidates. We propose that DMOADs should be more appropriately targeted and investigated according to the emerging clinical phenotypes and molecular endotypes of OA. Based on the findings from recent clinical trials, we propose key topics and directions for the development of future DMOADs.

Clinical monitoring in osteoarthritis: Biomarkers

OBJECTIVE

The purpose of this overview of osteoarthritis (OA) biomarkers is to provide the non-specialist with a toolbox, based on experience acquired by biomarker researchers over many years, to understand biomarkers in general and their use in the OA field.

METHODS

We provide an update on this subject since the OARSI Primer on osteoarthritis (OA) nearly a decade ago.

RESULTS

Since the last update, the importance of molecular biomarkers has been increasingly recognized in the field, but no OA-related biomarkers have been adopted for routine use in clinical practice. The current lack of chondroprotective treatments for OA impairs the assessment, validation and qualification of the potential role of biomarkers as tools for monitoring disease status and patient responses to treatment of OA. Yet there is no lack of an evolving compendium of OA-related biomarkers, ever more fit-for-purpose, that could currently facilitate drug development for OA. We provide an abbreviated update and overview of specific soluble OA-related biomarkers for this new OARSI Primer on OA with OA-relevant examples encompassing the concepts of biomarker nomenclature, qualification, interpretation, measurement, reporting requirements, application to research, drug discovery and clinical care, and future needs for biomarker advancement.

CONCLUSION

Appropriate biomarkers should play a role at all stages of OA diagnosis, prognosis, drug development, and treatment. The future of OA biomarker research and development holds great promise as its foundation is increasingly robust.

Chondrocyte-specific genomic editing enabled by hybrid exosomes for osteoarthritis treatment

Rationale: A cell-specific delivery vehicle is required to achieve gene editing of the disease-associated cells, so the hereditable genome editing reactions are confined within these cells without affecting healthy cells. A hybrid exosome-based nano-sized delivery vehicle derived by fusion of engineered exosomes and liposomes will be able to encapsulate and deliver CRISPR/Cas9 plasmids selectively to chondrocytes embedded in articular cartilage and attenuate the condition of cartilage damage. Methods: Chondrocyte-targeting exosomes (CAP-Exo) were constructed by genetically fusing a chondrocyte affinity peptide (CAP) at the N-terminus of the exosomal surface protein Lamp2b. Membrane fusion of the CAP-Exo with liposomes formed hybrid CAP-exosomes (hybrid CAP-Exo) which were used to encapsulate CRISPR/Cas9 plasmids. By intra-articular (IA) administration, hybrid CAP-Exo/Cas9 sgMMP-13 entered the chondrocytes of rats with cartilage damages that mimicked the condition of osteoarthritis. Results: The hybrid CAP-Exo entered the deep region of the cartilage matrix in arthritic rats on IA administration, delivered the plasmid Cas9 sgMMP-13 to chondrocytes, knocked down the matrix metalloproteinase 13 (MMP-13), efficiently ablated the expression of MMP-13 in chondrocytes, and attenuated the hydrolytic degradation of the extracellular matrix proteins in the cartilage. Conclusion: Chondrocyte-specific knockdown of MMP-13 mitigates or prevents cartilage degradation in arthritic rats, showing that hybrid CAP-Exo/Cas9 sgMMP-13 may alleviate osteoarthritis.

Biochemical, clinical, demographic and imaging biomarkers for disease progression in knee osteoarthritis

Aim: To identify prognostic biomarker(s) for knee osteoarthritis (OA) in the Osteoarthritis Initiative (OAI) cohort. Methods: Multilevel regression was used to determine the association between baseline biomarkers and change in biomarkers from baseline to 24 months with clinical and radiographic OA progression over 48 months of follow-up. Results: Higher values of baseline urinary CTXII were consistently associated with an increased risk of OA disease progression outcomes: Kellgren & Lawrence grade (odds ratio [OR]: 1.15, 95% CI: 1.03-1.28); medial joint space narrowing (OR: 1.06, 95% CI: 1.02-1.10); lateral osteophytes (OR: 1.05, 95% CI: 1.01-1.10); joint space width (regression coefficient: -0.005, 95% CI: -0.008-0.001); and Western Ontario and McMaster Universities Arthritis Index pain scores (OR: 1.02, 95% CI: 1.01-1.04). Changes in serum PIIANP and serum COMP over 24 months were associated with clinical disease progression. Conclusion: Urinary CTXII showed stronger associations with radiographic OA and appears to be a reliable prognostic marker, while changes in other biomarkers were found in early symptomatic OA, supporting the phasic nature of OA.

Associations between serum biomarkers of cartilage metabolism and serum hyaluronic acid, with risk factors, pain categories, and disease severity in knee osteoarthritis: a pilot study

BACKGROUND

Specific serum biomarkers of cartilage metabolism such as cartilage oligomeric matrix protein (sCOMP) and procollagen type II C-terminal propeptide (sPIICP) as well as hyaluronan (sHA), a biomarker of synovitis, have been implicated in the pathophysiology of knee osteoarthritis (OA). However, the associations of these biomarkers with the severity of the disease and OA risk factors, including age and obesity remain inconclusive. This analysis examines the associations between these serum biomarkers and the radiographic severity of OA and knee pain, as wells as obesity, the age and gender of the participants, and other OA risk factors.

METHODS

From 44 patients with early knee OA and 130 patients with late knee OA we analyzed the radiographic severity of the disease using the Kellgren and Lawrence (KL) grading system. Moreover, 38 overweight healthy individuals were used as a control group. Specific information was collected from all participants during their recruitment. The levels of the three serum biomarkers were quantified using commercially available ELISA kits. Serum biomarkers were analyzed for associations with the average KL scores and pain in both knees, as well as with specific OA risk factors.

RESULTS

The levels of sCOMP were elevated in patients with severe late OA and knee pain and correlated weakly with OA severity. A weakly correlation of sHA levels and OA severity OA was observed. We demonstrated that only sPIICP levels were markedly decreased in patients with late knee OA suggesting the alterations of cartilage metabolism in this arthritic disease. Moreover, we found that sPIICP has the strongest correlation with obesity and the severity of OA, as well as with the knee pain at rest and during walking regardless of the severity of the disease. ROC analysis showed that the area under the ROC curve (AUC) was 0.980 (95% CI: 0.945-0.995; p < 0.0001), suggesting high diagnostic accuracy of sPIICP. Interestingly, gender and age had also an effect on the levels of sPIICP.

CONCLUSION

This study revealed the potential of serum PIICP to be used as a biomarker to monitor the progression of knee OA, however, further studies are warranted to elucidate its clinical implication.

Editorial Commentary: Serum Cartilage Oligomeric Matrix Protein Appears to Be the Most Useful Biomarker for Tracking Early Osteoarthritis of the Knee in Anterior Cruciate Ligament Deficient Patients (But May Also Reflect Synovitis)

Owing to chondral or meniscal pathology sustained at the time of injury, patients who sustain anterior cruciate ligament injury are at risk of knee osteoarthritis (OA). Thus, recognition of early OA is critical. Detection of joint space narrowing on radiography has been described as outdated, and furthermore, the different descriptions of the Kellgren-Lawrence criteria have an impact on the classification of OA of the lowest grade (Kellgren-Lawrence grade ≥ 1). Serum cartilage oligomeric matrix protein (COMP) may allow detection of early OA in patients with anterior cruciate ligament deficiency because significantly higher levels have been observed in patients with early OA than in patients with non-early OA. Serum COMP appears to be the most useful of the biomarkers studied. Prior studies have shown correlations with OA in animal models and via magnetic resonance imaging evaluation. However, I would be hesitant about widespread use. It is possible that the serum COMP level reflects not only cartilage damage but also synovitis. This may be particularly misleading in patients with diagnoses of rheumatologic disorders and/or undiagnosed genetic HLA-B27 variants.

Serum Cartilage Oligomeric Matrix Protein Detects Early Osteoarthritis in Patients With Anterior Cruciate Ligament Deficiency

PURPOSE

To investigate the ability of serum cartilage oligomeric matrix protein (COMP) to detect early osteoarthritis (OA) (International Cartilage Research Society [ICRS] grade 1 or 2 cartilage lesions) in patients with anterior cruciate ligament (ACL)-deficient patients.

METHODS

Patients with an ACL injury of Kellgren-Lawrence grade 0 or 1 were enrolled. Serum samples for COMP measurement were obtained before surgery. The cartilage surfaces of 6 compartments were classified using the ICRS grading system. The patients were divided into groups with and without early OA according to the cartilage findings and diagnostic criteria for early OA.

RESULTS

In total, 98 patients (mean age 23.7 years; range 12 to 49) were included, with 30 patients (30.6%) in the early OA group and 68 (69.4%) in the no early OA group. The 2 groups significantly differed in age, body mass index, preoperative Tegner activity scale, and serum COMP level. The cutoff value of serum COMP for the presence of early OA arthroscopic cartilage lesions was 152.0 ng/mL. Multiple logistic regression analysis revealed age (odds ratio 1.09; 95% confidence interval [CI] 1.02 to 1.16; P = .01) and serum COMP (odds ratio 1.02; 95% CI 1.01 to 1.04; P < .001) to be independent factors for the presence of early OA arthroscopic cartilage findings.

CONCLUSIONS

The incidence of early OA arthroscopic cartilage findings was ∼30% in patients with ACL deficiency, and serum COMP levels were significantly higher in the early OA group than in the no early OA group. The optimum cutoff value for serum COMP was 152 ng/mL. Serum COMP can be used to detect early cartilage change in patients with ACL deficiency.

LEVEL OF EVIDENCE

Ⅲ, retrospective comparative study.

Blood and urine biomarkers in osteoarthritis - an update on cartilage associated type II collagen and aggrecan markers

PURPOSE OF REVIEW

Osteoarthritis (OA) is a painful disease for which drug development has proven difficult. One major reason for this is the heterogeneity of the disease and the current lack of operationalized means to distinguish various disease endotypes (molecular subtypes). Biomarkers measured in blood or urine, reflecting joint tissue turnover, have been developed and tested during the last decades. In this narrative review, we provide highlights on biomarkers derived from the two most studied and abundant cartilage proteins - type II collagen and aggrecan.

RECENT FINDINGS

Multiple biomarkers assessing type II collagen degradation and formation, and aggrecan turnover have been developed. Several markers, such as uCTX-II, have been validated for their association with disease severity and prognosis, as well as pharmacodynamically used to describe the mode of action and efficacy of drugs in development. There is a great need for biomarkers for subdividing patients (i.e., endotyping) and recent scientific advances have not yet come closer to achieving this goal.

SUMMARY

There is strong support for using biomarkers for understanding OA, reflecting degradation and formation of the joint tissues, focused on type II collagen and aggrecan. There is still a lack of in vitro diagnostics, in all contexts of use.

Treating Full Depth Cartilage Defects with Intraosseous Infiltration of Plasma Rich in Growth Factors: An Experimental Study in Rabbits

OBJECTIVE

Intraarticular (IA) administration of platelet-rich plasma (PRP) has been proposed as a new strategy to halt osteoarthritis (OA) progression. In patients with severe OA, its potential is limited because it is unable to reach the subchondral bone, so a new strategy is needed, and intraosseous (IO) infiltration has been suggested. The purpose is to assess the impact of IA together with IO infiltration of plasma rich in growth factors (PRGF) in serum hyaluronic acid (HA) and type II collagen cleavage neoepitope (C2C) levels.

DESIGN

A total of 32 rabbits were included in the study and randomly divided into 2 groups: control and treatment. A 4-mm chondral defect was created in the medial femoral condyle and IA followed by IO infiltration were performed. Serum C2C and HA levels were measured using enzyme-linked immunosorbent assay (ELISA) tests before infiltration and 28, 56, and 84 days post-infiltration.

RESULTS

Significant lower C2C serum levels were obtained in treatment group (IA + IO infiltration of PRGF) at 84 days post-infiltration than in control group (IA infiltration of PRGF + IO infiltration of saline solution), while no significant differences between groups were reported at any other study times. Regarding HA, at 56 days post-infiltration, greater significant levels were seen in the treatment group. However, at 84 days post-infiltration, no significant differences were obtained, although lower levels were reported in the treatment group.

CONCLUSIONS

Despite inconclusive, the results suggest that the combination of IA and IO infiltration with PRGF may enhance cartilage and subchondral bone regeneration, but further studies are needed.

Increased serum AXL is associated with radiographic knee osteoarthritis severity

Objective

To investigate the expression and clinical significance of serum soluble AXL in patients with radiographic knee osteoarthritis (KOA).

Methods

There were 183 patients with KOA who were selected and divided based on the Kellgren‐Lawrence (KL) score into KL 0 subgroups (n = 42), KL I‐II subgroups (n = 90), and KL III‐IV subgroups (n = 51). Healthy volunteers (n = 170) in our hospital were selected with matched age and gender as the control group. AXL level in serum was detected by enzyme‐linked immunosorbent assay. The correlation between serum AXL with severity and clinical indicators of osteoarthritis was analyzed.

Results

The level of serum AXL was significantly higher in the osteoarthritis group than that in the control group (P < .05). In the osteoarthritis patients, serum AXL level was increased with the increase of KL score. Serum AXL level was positively correlated with age, body mass index, erythrocyte sedimentation rate, serum C‐reactive protein, cartilage oligomeric protein, matrix metalloproteinase‐13, and transforming growth factor‐β1 levels. The cut‐off value for serum AXL was determined as 33.375 ng/mL by receiver operating curve analysis.

Conclusion

The level of serum AXL in patients with osteoarthritis is significantly higher than in healthy controls, and is closely related to the severity of radiographic osteoarthritis.

A novel model of a biomechanically induced osteoarthritis-like cartilage for pharmacological in vitro studies

Excessive pressure or overload induces and aggravates osteoarthritic changes in articular cartilage, but the underlying biomechanical forces are largely ignored in existing pharmacological in vitro models that are used to investigate drugs against osteoarthritis (OA). Here, we introduce a novel in vitro model to perform pathophysiological and pharmacological investigations, in which cartilage explants are subjected to intermittent cyclic pressure, and characterize its ability to mimic OA‐like tissue reactivity. Mechanical loading time‐dependently increased the biosynthesis, content and retention of fibronectin (Fn), whereas collagen metabolism remained unchanged. This protocol upregulated the production and release of proteoglycans (PGs). The release of PGs from explants was significantly inhibited by a matrix metalloproteinase (MMP) inhibitor, suggesting the involvement of such proteinases in the destruction of the model tissue, similar to what is observed in human OA cartilage. In conclusion, the metabolic alterations in our new biomechanical in vitro model are similar to those of early human OA cartilage, and our pharmacological prevalidation with an MMP‐inhibitor supports its value for further in vitro drug studies.

Biomarkers of joint metabolism and bone mineral density are associated with early knee osteoarthritis in premenopausal females

INTRODUCTION

Biomarkers of bone and cartilage metabolism were proposed as early diagnosis indicators for knee osteoarthritis (OA), however, which were influenced by disease stage, age, and menopause state. Accurate diagnosis indicators are eagerly awaited. The current study aims to investigate associations of joint metabolism biomarkers and bone mineral density (BMD) with early knee OA in males and premenopausal females before age 50 years.

METHOD

A total of 189 patients aged before 50 years with early knee OA and 152 healthy participants were enrolled. Levels of bone biomarkers (PINP, OC, and CTX-I) and cartilage biomarkers (PIIANP, COMP, CTX-II, and MMP-3) were assessed. BMD was measured at the lumbar, femoral neck, and hip. Multivariate regression analyses were performed to evaluate the relationship between biomarkers, BMD, and early knee OA.

RESULTS

Serum COMP, urine CTX-II and BMD at femoral neck and hip were increased in premenopausal patients as compared to control; with serum PINP and OC reduced. Meanwhile, serum COMP, urine CTX-II, and BMD at femoral neck and hip showed positive associations with premenopausal early knee OA, while serum PINP had negative association. However, in male patients, only serum COMP was higher than control, and no association of biomarkers or BMD was found with early knee OA.

CONCLUSIONS

The joint metabolism biomarkers and BMD showed multiple associations with early knee OA in premenopausal females, but not in males aged before 50 years. It was suggested that sex differences should be taken into account when evaluating cartilage and bone metabolism in early knee OA. Key Points • The joint metabolism biomarkers and BMD are associated with early knee OA in premenopausal females, but not in males aged before 50 years. • Sex differences should be taken into account when evaluating cartilage and bone metabolism in early knee OA.

Soluble biological markers in osteoarthritis

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

Angiotensin II triggers knee joint lesions in experimental osteoarthritis

OBJECTIVES

This study aimed to evaluate the involvement of Angiotensin II (Ang II) in joint lesions associated with osteoarthritis (OA) in vitro and in vivo.

METHODS

Chondrocyte cultures were obtained from knee joints of neonatal rats and stimulated with Ang II/MIA/ACE inhibitors. In vivo, rats treated or not with the ACE inhibitor captopril, received daily injections of Ang II or sodium monoiodoacetate (MIA) in knee joints for evaluation of cartilage, bone, and synovial lesions.

RESULTS

Cultured chondrocytes expressed the mRNA for Ace, Agtr1, Agtr2, and Mas1. Stimulating cells with Ang II reduced chondrocyte viability and metabolism. Accordingly, in vivo Ang II injection into the knees of rats triggered hyperalgesia, joint edema, increased the number of leukocytes in the joint cavity, and induced cartilage lesions associated with OA alterations. In further experiments, Ang II synthesis was prevented with the ACE inhibitor Captopril in the context of MIA-induced OA. Ang II inhibition with captopril improved the OARSI score, induced chondroprotection, and reduced the leukocyte recruitment from synovium after MIA. Additionally, captopril prevented MIA-induced bone resorption, by decreasing the number of osteoclasts and increasing the expression of IL-10 in the bone. In vitro, inhibiting Ang II synthesis decreased MIA-induced chondrocyte death and increased Col2a1 transcription.

CONCLUSION

Ang II induces chondrocyte death and joint tissue damages associated with OA and its modulation can be a therapeutic strategy in osteoarthritis.

Biomarkers of Joint Damage in Osteoarthritis: Current Status and Future Directions

Osteoarthritis (OA) is a disease of the whole joint organ, characterized by the loss of cartilage, and structural changes in bone including the formation of osteophytes, causing disability and loss of function. It is also associated with systemic mediators and low-grade inflammation. Currently, there is negligible/no availability of specific biomarkers that can be used to facilitate the diagnosis and treatment of OA. The most unmet clinical need is, however, related to the monitoring of disease progression over a short period that can be used in clinical trials. In this review, the value of biomarkers identified over the past decade has been highlighted. These biomarkers are associated with the synthesis and breakdown of cartilage, including collagenous and noncollagenous biomarkers, inflammatory and anti-inflammatory biomarkers, expressed in the biological fluid such as serum, synovial fluid, and urine. Broad validation of novel and clinically applicable biomarkers and their involvement in the pathways are particularly needed for early-stage diagnosis, monitoring disease progression, and severity and examining new drugs to mitigate the effects of this highly prevalent and debilitating condition.

A low cartilage formation and repair endotype predicts radiographic progression of symptomatic knee osteoarthritis

Background

Osteoarthritis (OA) is a disease with multiple endotypes. A hallmark of OA is loss of cartilage; however, it is evident that the rate of cartilage loss differs among patients, which may partly be attributed to differential capacity for cartilage repair. We hypothesize that a low cartilage repair endotype exists and that such endotypes are more likely to progress radiographically. The aim of this study is to examine the associations of level of cartilage formation with OA severity and radiographic OA progression. We used the blood-based marker PRO-C2, reflecting type II collagen formation, to assess levels of cartilage formation.

Materials and methods

The type II collagen propeptide PRO-C2 was measured in the serum/plasma of knee OA subjects from New York University (NYU, n = 106) and a subcohort of the phase III oral salmon calcitonin (sCT) trial SMC021-2301 (SMC, n = 147). Risk of radiographic medial joint space narrowing (JSN) over 24 months was compared between quartiles (very low, low, moderate, and high) of PRO-C2. Associations were adjusted for age, gender, BMI, race, baseline pain levels, and baseline joint space width.

Results

In both the NYU and SMC cohorts, subjects with low PRO-C2 levels had greater JSN compared with subjects with high PRO-C2. Mean difference in JSN between subjects with very low and high levels of PRO-C2 was 0.65 mm (p = 0.002), corresponding to a 3.4 (1.4–8.6)-fold higher risk of progression. There was no significant effect of sCT treatment, compared with placebo, on JSN over 2 years before stratification based on baseline PRO-C2. However, there were proportionately fewer progressors in the sCT arm of the very low/low PRO-C2 group compared with the moderate/high group (Chi squared = 6.5, p = 0.011).

Conclusion

Serum/plasma level of type II collagen formation, PRO-C2, may be an objective indicator of a low cartilage repair endotype, displaying radiographic progression and superior response to a proanabolic drug.

Level of evidence

Level III post hoc exploratory analysis of one longitudinal cohort and a sub-study from one phase III clinical trial.

Decreased Expression of Heat Shock Protein 47 Is Associated with T-2 Toxin and Low Selenium-Induced Matrix Degradation in Cartilages of Kashin-Beck Disease

Recent evidence suggests a role of type II collagen in Kashin-Beck disease (KBD) degeneration. We aimed to assess the abnormal expression of heat shock protein 47 (HSP47) which is associated with a decrease in type II collagen and an increase in cartilage degradation in KBD. Hand phalange cartilages were collected from KBD and healthy children. Rats were administered with T-2 toxin under the selenium (Se)-deficient diet. ATDC5 cells were seeded on bone matrix gelatin to construct engineered cartilaginous tissue. C28/I2 and ATDC5 cells and engineered tissue were exposed to different concentrations of T-2 toxin with or without Se. Cartilage degeneration was determined through histological evaluation. The distribution and expression of type II collagen and HSP47 were investigated through immunohistochemistry, western blotting, and real-time PCR. KBD cartilages showed increased chondronecrosis and extracellular matrix degradation in deep zone with decreased type II collagen and HSP47 expression. The low-Se + T-2 toxin animal group showed a significantly lower type II collagen expression along with decreased HSP47 expression. Decreased type II collagen and HSP47 in C28/I2 and ATDC5 cells induced by T-2 toxin showed a dose-dependent manner. Hyaline-like cartilage with zonal layers was developed in engineered cartilaginous tissues, with decreased type II collagen and HSP47 expression found in T-2 toxin-treated group. Se-supplementation partially antagonized the inhibitory effects of T-2 toxin in chondrocytes and cartilages. HSP47 plays a role in the degenerative changes of KBD and associated with T-2 toxin-induced decreased type II collagen expression, further promoting matrix degradation.

Relationships among bedding materials, bedding bacterial composition and lameness in dairy cows

Objective

Bedding materials directly contact hooves of dairy cows and they may serve as environmental sources of lameness-associated pathogen. However, the specific composition of bacteria hidden in bedding materials is still not clear. The aim of this study was to determine the effect bedding material and its bacterial composition has on lameness of Holstein heifers.

Methods

Forty-eight Holstein heifers with similar body weights were randomly assigned into three groups including sand bedding (SB), concrete floor (CF), and compost bedding (CB). Hock injuries severity and gait performance of dairy cows were scored individually once a week. Blood samples were collected at the end of the experiment and bedding material samples were collected once a week for Illumina sequencing.

Results

The CF increased visible hock injuries severity and serum biomarkers of joint damage in comparison to SB and CB groups. Besides, Illumina sequencing and analysis showed that the bacterial community of CB samples had higher similarity to that of SB samples than CF samples. Bacteria in three bedding materials were dominated by gastrointestinal bacteria and organic matter-degrading bacteria, such as Actinobacteria, Firmicutes, and norank JG30-KF-cM45. Lameness-associated Spirochaetaceae and Treponeme were only detected in SB and CB samples with a very low relative abundance (0% to 0.08%).

Conclusion

The bacterial communities differed among bedding materials. However, the treponemes pathogens involved in the pathogenesis of lameness may not be a part of microbiota in bedding materials of dairy cows.

The emerging landscape of nanotheranostic-based diagnosis and therapy for osteoarthritis

Osteoarthritis (OA) is a common degenerative disease involving numerous joint tissues and cells, with a growing rate in prevalence that ultimately results in a negative social impact. Early diagnosis, OA progression monitoring and effective treatment are of significant importance in halting OA process. However, traditional imaging techniques lack sensitivity and specificity, which lead to a delay in timely clinical intervention. Additionally, current treatments only slow the progression of OA but have not meet the largely medical need for disease-modifying therapy. In order to overcome the above-mentioned problems and improve clinical efficacy, nanotheranostics has been proposed on OA remedy, which has confirmed success in animal models. In this review, different imaging targets-based nanoprobe for early and timely OA diagnosis is first discussed. Second, therapeutic strategies delivered by nanosystem are summarized as much as possible. Their advantages and the potential for clinical translation are detailed discussed. Third, nanomedicine simultaneously combined with the imaging for OA treatment is introduced. Nanotheranostics dynamically tracked the OA treatment outcomes to timely and individually adjust therapy. Finally, future prospects and challenges of nanotechnology-based OA diagnosis, imaging and treatment are concluded and predicted. It is believed that nanoprobe and nanomedicine will become prospective in OA therapeutic revolution.

C-Terminal Cross-Linked Telopeptides of Type II Collagen as Biomarker for Radiological Knee Osteoarthritis: A Meta-Analysis

BACKGROUND

C-terminal cross-linked telopeptides of type II collagen (CTX-II) are one of the most frequently assessed markers for osteoarthritis (OA) diagnosis. The aim of this meta-analysis was to confirm the diagnostic value of urinary CTX-II in knee OA.

MATERIALS AND METHODS

PubMed, ScienceDirect, and EMBASE were searched for studies measured urinary CTX-II in patients with knee OA and in healthy controls. Urinary CTX-II levels were compared between knee OA patients and controls. Differences between groups were expressed as standardized mean differences (SMD) when individual outcomes were measured with different scales. Otherwise, outcomes were presented as mean differences (MD). Subgroup analyses were also conducted to compare efficiency of urinary CTX-II between Kellgren-Lawrence (KL) classification, genders, ethnicities, and study size.

RESULTS

Thirteen studies involved a total of 2856 participants were included. Pooled SMD showed that urinary CTX-II levels were significantly elevated in knee OA group compared to controls (SMD 0.82; 95% CI 0.41-1.24; P < 0.0001). For KL 3 to 4 versus KL 2, higher urinary CTX-II levels were found in severe knee OA patients. Subgroup analyses revealed that urinary CTX-II performed better in females as compared with males and in European subjects as compared with Asian population. Also, study size did not influence the statistic results.

CONCLUSION

This is the largest scale meta-analysis assessing the diagnostic performance of urinary CTX-II levels as biomarker for knee OA. According to our findings, urinary CTX-II levels have a potential to distinguish knee OA patients from healthy controls which can serve as biomarker for knee OA.

Serological CTX-II does not measure the same as urinary CTX-II

Objective

Type II collagen is the most abundant protein of articular cartilage. The urinary cross-linked C-terminal telopeptide of type II collagen (uCTX-II) is a matrix metalloproteinase (MMP) cleaved fragment and may be the most well-validated biomarker in osteoarthritis. The aim was to develop a serological immunoassay of CTX-II (sCTX-II) and evaluated both sCTX-II and uCTX-II levels in a cross-sectional osteoarthritis cohort.

Methods

The biological relevance of sCTX-II was validated in bovine cartilage explants cultured in the presence of Oncostatin M and tumor necrosis factor alpha (OT) or OT supplemented with GM6001 for 3 weeks. Serum and urine samples from an osteoarthritis cohort were assayed using sCTX-II and uCTX-II, respectively. Spearman's correlation was performed to evaluate the correlation between sCTX-II and uCTX-II. The association between the level of biomarkers and clinical variables was also investigated.

Results

The supernatant analyzed in sCTX-II showed significant higher CTX-II levels in the end phases of explant culture compared to the vehicle group. The release of CTX-II was completely suppressed by GM6001. The sCTX-II levels in serum were not associated with uCTX-II in urine although sCTX-II levels in urine were significantly correlated with uCTX-II. uCTX-II correlated with age and gender while sCTX-II did not. sCTX-II cannot demonstrate any clinical relevance in a cross-sectional OA cohort as uCTX-II did.

Conclusion

The sCTX-II assay can reflect the MMP-mediated type II collagen degradation in bovine cartilage explants. However, sCTX-II and uCTX-II assays show different patterns suggesting the presence of CTX-II in blood may be different from that of urine.

Genetic correlations between cartilage regeneration and degeneration reveal an inverse relationship

OBJECTIVE

The etiology of osteoarthritis (OA) is unknown, however, there appears to be a significant contribution from genetics. We have identified recombinant inbred strains of mice derived from LG/J (large) and SM/J (small) strains that vary significantly in their ability to repair articular cartilage and susceptibility to post-traumatic OA due to their genetic composition. Here, we report cartilage repair phenotypes in the same strains of mice in which OA susceptibility was analyzed previously, and determine the genetic correlations between phenotypes.

DESIGN

We used 12 recombinant inbred strains, including the parental strains, to test three phenotypes: ear-wound healing (n = 263), knee articular cartilage repair (n = 131), and post-traumatic OA (n = 53) induced by the surgical destabilization of the medial meniscus (DMM). Genetic correlations between various traits were calculated as Pearson's correlation coefficients of strain means.

RESULTS

We found a significant positive correlation between ear-wound healing and articular cartilage regeneration (r = 0.71; P = 0.005). We observed a strong inverse correlation between articular cartilage regeneration and susceptibility to OA based on maximum (r = -0.54; P = 0.036) and summed Osteoarthritis Research Society International (OARSI) scores (r = -0.56; P = 0.028). Synovitis was not significantly correlated with articular cartilage regeneration but was significantly positively correlated with maximum (r = 0.63; P = 0.014) and summed (r = 0.70; P = 0.005) OARSI scores. Ectopic calcification was significantly positively correlated with articular cartilage regeneration (r = 0.59; P = 0.021).

CONCLUSIONS

Using recombinant inbred strains, our study allows, for the first time, the measurement of genetic correlations of regeneration phenotypes with degeneration phenotypes, characteristic of OA (cartilage degeneration, synovitis). We demonstrate that OA is positively correlated with synovitis and inversely correlated with the ability to repair cartilage. These results suggest an addition to the risk paradigm for OA from a focus on degeneration to regeneration.

Predicting Incident Radiographic Knee Osteoarthritis in Middle-Aged Women Within Four Years: The Importance of Knee-Level Prognostic Factors

OBJECTIVE

To develop and internally validate risk models and a clinical risk score tool to predict incident radiographic knee osteoarthritis (RKOA) in middle-aged women.

METHODS

We analyzed 649 women in the Chingford 1,000 Women study. The outcome was incident RKOA, defined as Kellgren/Lawrence grade 0-1 at baseline and ≥2 at year 5. We estimated predictors' effects on the outcome using logistic regression models. Two models were generated. The clinical model considered patient characteristics, medication, biomarkers, and knee symptoms. The radiographic model considered the same factors, plus radiographic factors (e.g., angle between the acetabular roof and the ilium's vertical cortex [hip α-angle]). The models were internally validated. Model performance was assessed using calibration and discrimination (area under the receiver characteristic curve [AUC]).

RESULTS

The clinical model contained age, quadriceps circumference, and a cartilage degradation marker (C-terminal telopeptide of type II collagen) as predictors (AUC = 0.692). The radiographic model contained older age, greater quadriceps circumference, knee pain, knee baseline Kellgren/Lawrence grade 1 (versus 0), greater hip α-angle, greater spinal bone mineral density, and contralateral RKOA at baseline as predictors (AUC = 0.797). Calibration tests showed good agreement between the observed and predicted incident RKOA. A clinical risk score tool was developed from the clinical model.

CONCLUSION

Two models predicting incident RKOA within 4 years were developed, including radiographic variables that improved model performance. First-time predictor hip α-angle and contralateral RKOA suggest OA origins beyond the knee. The clinical tool has the potential to help physicians identify patients at risk of RKOA in routine practice, but the tool should be externally validated.

Evaluation of the articular cartilage in the knees of rats with induced arthritis treated with curcumin

This study was designed to evaluate the anti-inflammatory effects of a curcumin treatment on the knee of rats with induced osteoarthritis. Fifteen adult rats were used and divided in three groups: the osteoarthritis group (OAG), control group (CG-without induction of osteoarthritis), and curcumin-treated osteoarthritis group (COAG). Osteoarthritis was induced in the right knee of rats in the OAG and COAG by administering an intra-articular injection of 1 mg of zymosan. Fourteen days after induction, 50 mg/kg curcumin was administered by gavage daily for 60 days to the COAG. After the treatment period, rats from all groups were euthanized. Medial femoral condyles were collected for light microscopy and immunohistochemical staining. The expression of SOX-5, IHH, MMP-8, MMP-13, and collagen 2 (Col2) was analyzed. The COAG exhibited an increase in the number of chondrocytes in the surface and middle layers compared with that of the OAG and CG, respectively. The COAG also showed a decrease in the thicknesses of the middle and deep layers compared with those of the OAG, and an increase in Col2 expression was observed in all articular layers (surface, middle, and deep) in the COAG compared with that in the OAG. SOX-5 expression was increased in the surface and deep layers of the COAG compared with those in the OAG and CG. Based on the results of this study, the curcumin treatment appeared to exert a protective effect on cartilage, as it did not result in an increase in cartilage thickness or in MMP-8 and MMP-13 expression but led to increased IHH, Col2, and SOX-5 expression and the number of chondrocytes.

Proteomic fingerprints of damage in extracellular matrix assemblies

In contrast to the dynamic intracellular environment, structural extracellular matrix (ECM) proteins with half-lives measured in decades, are susceptible to accumulating damage. Whilst conventional approaches such as histology, immunohistochemistry and mass spectrometry are able to identify age- and disease-related changes in protein abundance or distribution, these techniques are poorly suited to characterising molecular damage. We have previously shown that mass spectrometry can detect tissue-specific differences in the proteolytic susceptibility of protein regions within fibrillin-1 and collagen VI alpha-3. Here, we present a novel proteomic approach to detect damage-induced “peptide fingerprints” within complex multi-component ECM assemblies (fibrillin and collagen VI microfibrils) following their exposure to ultraviolet radiation (UVR) by broadband UVB or solar simulated radiation (SSR). These assemblies were chosen because, in chronically photoaged skin, fibrillin and collagen VI microfibril architectures are differentially susceptible to UVR. In this study, atomic force microscopy revealed that fibrillin microfibril ultrastructure was significantly altered by UVR exposure whereas the ultrastructure of collagen VI microfibrils was resistant. UVR-induced molecular damage was further characterised by proteolytic peptide generation with elastase followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Peptide mapping revealed that UVR exposure increased regional proteolytic susceptibility within the protein structures of fibrillin-1 and collagen VI alpha-3. This allowed the identification of UVR-induced molecular changes within these two key ECM assemblies. Additionally, similar changes were observed within protein regions of co-purifying, microfibril-associated receptors integrins αv and β1. This study demonstrates that LC-MS/MS mapping of peptides enables the characterisation of molecular post-translational damage (via direct irradiation and radiation-induced oxidative mechanisms) within a complex in vitro model system. This peptide fingerprinting approach reliably allows both the identification of UVR-induced molecular damage in and between proteins and the identification of specific protein domains with increased proteolytic susceptibility as a result of photo-denaturation. This has the potential to serve as a sensitive method of identifying accumulated molecular damage in vivo using conventional mass spectrometry data-sets.

•

Mass spectrometry “peptide fingerprinting” can detect post-translational damage within extracellular matrix proteins.

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UVR-induced FBN1 and COL6A3 peptide fingerprints are reproducibly identified from purified microfibrils.

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Peptide mapping reveals increased regional susceptibilities to proteolysis in FBN1 and COL6A3 proteins.

•

Regional changes are also observed in protein structures of microfibril-associated receptor integrins αv and β1.

•

This “peptide fingerprinting” approach is applicable to conventional LC-MS/MS datasets.

Mitochondrial Genetics and Epigenetics in Osteoarthritis

During recent years, the significant influence of mitochondria on osteoarthritis (OA), the most common joint disease, has been consistently demonstrated. Not only mitochondrial dysfunction but also mitochondrial genetic polymorphisms, specifically the mitochondrial DNA haplogroups, have been shown to have an important influence on different OA-related features, including the prevalence, severity, incidence, and progression of the disease. This influence could probably be mediated by the role of mitochondria in the regulation of different processes involved in the pathogenesis of OA, such as energy production, the generation of reactive oxygen and nitrogen species, apoptosis, and inflammation. The regulation of these processes is at least partially controlled by the bi-directional communication between the nucleus and mitochondria, which permits the regulation of adaptation to a wide range of stressors and the maintenance of cellular homeostasis. This bi-directional communication consists of an “anterograde regulation” by which the nucleus regulates mitochondrial biogenesis and activity and a “retrograde regulation” by which both mitochondria and mitochondrial genetic variation exert a regulatory signaling control over the nuclear epigenome, which leads to the modulation of nuclear genes. Throughout this mini review, we will describe the evidence that demonstrates the profound influence of the mitochondrial genetic background in the pathogenesis of OA, as well as its influence on the nuclear DNA methylome of the only cell type present in the articular cartilage, the chondrocyte. This evidence leads to serious consideration of the mitochondrion as an important therapeutic target in OA.

Blood and urinary collagen markers in osteoarthritis: markers of tissue turnover and disease activity

Introduction: The need for diagnostic markers in osteoarthritis (OA) is acute and immediate, as sensitive and precise tools that monitor disease activity and treatment response are lacking. Collagens - types I, II, and III - are the skeleton of the extracellular matrix of joint tissues. Joint collagens are generally turned over at a low rate, but the balance between formation and degradation is disturbed, leading to the loss of, for example, cartilage.Areas covered: We discuss the markers reflecting collagen turnover and provide examples of how they have been applied in OA research, as well as how we believe these should be used in the future. We have searched PubMed for full-text articles written in English using different combinations of the following terms: OA, biomarker, and collagen. The result is a narrative review that gives examples from the literature.Expert opinion: Collagen markers show promise, as they are direct measures of tissue balance. Until now, collagen markers have mainly been tested in observational cohorts, which may provide insights into the association between the candidate marker and clinical variables; however, these do not advance the development of qualified markers that can be used for drug development or in clinical practice.

Extracellular matrix turnover and inflammation in chemically-induced TMJ arthritis mouse models

The temporomandibular joint (TMJ) is a fibrocartilaginous tissue critical for chewing and speaking. In patients with temporomandibular disorders (TMDs), permanent tissue loss can occur. Recapitulating the complexity of TMDs in animal models is difficult, yet critical for the advent of new therapies. Synovial fluid from diseased human samples revealed elevated levels of tumor necrosis factor alpha (TNF-alpha). Here, we propose to recapitulate these findings in mice by subjecting murine TMJs with TNF-alpha or CFA (Complete Freund’s Adjuvant) in mandibular condyle explant cultures and by local delivery in vivo using TMJ intra-articular injections. Both TNF-alpha and CFA delivery to whole mandibular explants and in vivo increased extracellular matrix deposition and increased cartilage thickness, while TNF-alpha treated explants had increased expression of inflammatory cytokines and degradative enzymes. Moreover, the application of TNF-alpha or CFA in both models reduced cell number. CFA delivery in vivo caused soft tissue inflammation, including pannus formation. Our work provides two methods of chemically induced TMJ inflammatory arthritis through a condyle explant model and intra-articular injection model that replicate findings seen in synovial fluid of human patients, which can be used for further studies delineating the mechanisms underlying TMJ pathology.

The Effects of Well-Rounded Exercise Program on Systemic Biomarkers Related to Cartilage Metabolism

Nonsurgical treatment such as exercise is the preferred method for management of knee osteoarthritis (OA). A combination of aerobic, muscle strengthening, and flexibility exercises is recommended for older adults. However, effects of the exercise intervention on cartilage metabolism remain unclear. This study used biomarkers to investigate the effects of well-rounded exercise program on cartilage metabolism in 42 women (mean age: 59 years). Participants started a weekly supervised exercise program and continued for 12 weeks. Before and after the program, we measured physical performance on the Timed Up-and-Go Test, 3-Minute Walk Test, and 30-Second Chair Stand Test. We collected serum and urine samples at the start of the program until 24 weeks and measured the concentrations of 4 biomarkers related to type II collagen metabolism: serum cartilage type II procollagen carboxy propeptide (sPIICP), urine C-terminal telopeptide of collagen type II (uCTX-II), urine cleavage of type II collagen by collagenases (uC2C), and serum cartilage oligomeric matrix protein (sCOMP). Participants were divided into pre-OA and OA groups based on X-ray findings. The pre-OA group showed significant increases and decreases in sPIICP and uCTX-II concentrations with improved physical performance, respectively. sCOMP concentrations significantly increased in both groups. The exercise also improved physical performance with no detrimental effect on type II collagen metabolism in the OA group. Thus, well-rounded exercise may not only improve physical capacity but also have beneficial effects on type II collagen metabolism, especially in people without radiological OA.

Biomarkers of Hand Osteoarthritis Are Detectable after Mechanical Exercise

BACKGROUND

Hand osteoarthritis (OA) is one of the most common joint diseases, but studies on biomarkers are rare. The aim of this explorative study was (a) to evaluate potential biomarkers of hand OA, (b) to identify an optimal time point to sample venous blood, and (c) to correlate biomarker levels with radiological and clinical scores.

METHODS

Four female cohorts were investigated. One with a more Heberden-accentuated OA and one with a more Bouchard-accentuated hand OA, and two symptom-free control groups aged 20-30 or 50-75 years. The venous blood was sampled before and at eight time points after mechanical exercise of the OA hand. X-rays of OA hands were assessed using the Kellgren and Lawrence as well as Kallman scores. Participants were evaluated clinically using the AUSCAN™ Index, visual analog scale (VAS), and Health Assessment Questionnaire (HAQ). Serum levels of seven biomarkers were measured by ELISA.

RESULTS

The concentrations of CPII, COMP, IL-15, sVCAM-1, NGAL, and PIIANP were significantly increased within 15 min after exercise. PIIANP was markedly elevated in the Heberden-accentuated OA group as compared to both control groups, but did not correlate with any radiological or clinical score. Analysis of the probabilistic index further revealed that CPII can distinguish between Bouchard's OA and premenopausal controls whereas COMP can discriminate between Bouchard's and Heberden's OA.

CONCLUSIONS

This study demonstrates that even previously undetectable biomarkers can be quantified in serum after mechanical exercise. Future larger studies are needed to determine specificity and sensitivity of these markers and their ability to diagnose even pre-radiological OA.

The differentiating ability of four plasma biomarkers in canine hip dysplasia

BACKGROUND

The accumulation of cartilage breakdown products in body fluids has been extensively investigated to assess the accuracy of molecular biomarkers from a diagnostic, prognostic, and therapeutic perspective. Nevertheless, to the authors' knowledge, there is a lack of information about spontaneous models of hip osteoarthritis and the differentiating ability of collagen, noncollagen, and inflammatory biomarkers.

OBJECTIVES

We aimed to assess the accuracy of four plasma biomarkers that could differentiate between healthy dogs and dogs with hip dysplasia.

METHODS

Twenty-four dogs were used in this institutionally approved study (12 in the mild to severe hip dysplasia group; 12 in the control group). Plasma concentrations of biomarkers were compared. The ability of each marker to differentiate control from diseased dogs was assessed using an independent t-test, logistic regression, and receiving operating characteristics (ROC) analysis.

RESULTS

Three biomarkers were significantly different between the two groups. The collagen marker procollagen type II propeptide (PIICP) was useful in differentiating between control and diseased dogs with the best combination of sensitivity and specificity. The four biomarkers showed high area under the curve (AUC) values.

CONCLUSIONS

The results indicate that plasma biomarkers can be used as a screening tool for canine hip dysplasia. Although the cutoff values and diagnostic ability of the biomarkers used in this study show promising results, the sources of individual variability should be addressed. Future studies with larger groups of dogs are needed to correlate plasma levels in serum and synovial fluid during clinical disease.

A Novel High Sensitivity Type II Collagen Blood-Based Biomarker, PRO-C2, for Assessment of Cartilage Formation

N-terminal propeptide of type II collagen (PIINP) is a biomarker reflecting cartilage formation. PIINP exists in two main splice variants termed as type IIA and type IIB collagen NH₂-propeptide (PIIANP, PIIBNP). PIIANP has been widely recognized as a cartilage formation biomarker. However, the utility of PIIBNP as a marker in preclinical and clinical settings has not been fully investigated yet. In this study, we aimed to characterize an antibody targeting human PIIBNP and to develop an immunoassay assessing type II collagen synthesis in human blood samples. A high sensitivity electrochemiluminescence immunoassay, hsPRO-C2, was developed using a well-characterized antibody against human PIIBNP. Human cartilage explants from replaced osteoarthritis knees were cultured for ten weeks in the presence of growth factors, insulin-like growth factor 1 (IGF-1) or recombinant human fibroblast growth factor 18 (rhFGF-18). The culture medium was changed every seven days, and levels of PIIBNP, PIIANP, and matrix metalloproteinase 9-mediated degradation of type II collagen (C2M) were analyzed herein. Serum samples from a cross-sectional knee osteoarthritis cohort, as well as pediatric and rheumatoid arthritis samples, were assayed for PIIBNP and PIIANP. Western blot showed that the antibody recognized PIIBNP either as a free fragment or attached to the main molecule. Immunohistochemistry demonstrated that PIIBNP was predominately located in the extracellular matrix of the superficial and deep zones and chondrocytes in both normal and osteoarthritic articular cartilage. In addition, the hsPRO-C2 immunoassay exhibits acceptable technical performances. In the human cartilage explants model, levels of PIIBNP, but not PIIANP and C2M, were increased (2 to 7-fold) time-dependently in response to IGF-1. Moreover, there was no significant correlation between PIIBNP and PIIANP levels when measured in knee osteoarthritis, rheumatoid arthritis, and pediatric serum samples. Serum PIIBNP was significantly higher in controls (KL0/1) compared to OA groups (KL2/3/4, p = 0.012). The hsPRO-C2 assay shows completely different biological and clinical patterns than PIIANP ELISA, suggesting that it may be a promising biomarker of cartilage formation.

Developing a toolkit for the assessment and monitoring of musculoskeletal ageing

The complexities and heterogeneity of the ageing process have slowed the development of consensus on appropriate biomarkers of healthy ageing. The Medical Research Council–Arthritis Research UK Centre for Integrated research into Musculoskeletal Ageing (CIMA) is a collaboration between researchers and clinicians at the Universities of Liverpool, Sheffield and Newcastle. One of CIMA’s objectives is to ‘Identify and share optimal techniques and approaches to monitor age-related changes in all musculoskeletal tissues, and to provide an integrated assessment of musculoskeletal function’—in other words to develop a toolkit for assessing musculoskeletal ageing. This toolkit is envisaged as an instrument that can be used to characterise and quantify musculoskeletal function during ‘normal’ ageing, lend itself to use in large-scale, internationally important cohorts, and provide a set of biomarker outcome measures for epidemiological and intervention studies designed to enhance healthy musculoskeletal ageing. Such potential biomarkers include: biochemical measurements in biofluids or tissue samples, in vivo measurements of body composition, imaging of structural and physical properties, and functional tests. This review assesses candidate biomarkers of musculoskeletal ageing under these four headings, details their biological bases, strengths and limitations, and makes practical recommendations for their use. In addition, we identify gaps in the evidence base and priorities for further research on biomarkers of musculoskeletal ageing.

Select Biomarkers on the Day of Anterior Cruciate Ligament Reconstruction Predict Poor Patient-Reported Outcomes at 2-Year Follow-Up: A Pilot Study

Background

The majority of patients develop posttraumatic osteoarthritis within 15 years of anterior cruciate ligament (ACL) injury. Inflammatory and chondrodegenerative biomarkers have been associated with both pain and the progression of osteoarthritis; however, it remains unclear if preoperative biomarkers differ for patients with inferior postoperative outcomes.

Hypothesis/Purpose

The purpose of this pilot study was to compare biomarkers collected on the day of ACL reconstruction between patients with “good” or “poor” 2-year postoperative outcomes. We hypothesized that inflammatory cytokines and chondrodegenerative biomarker concentrations would be significantly greater in patients with poorer outcomes.

Study Design

Prospective cohort design.

Methods

22 patients (9 females, 13 males; age = 19.5 ± 4.1 years; BMI = 24.1 ± 3.6 kg/m²) previously enrolled in a randomized trial evaluating early anti-inflammatory treatment after ACL injury. Biomarkers of chondrodegeneration and inflammation were assessed from synovial fluid (sf) samples collected on the day of ACL reconstruction. Participants completed Knee Injury and Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee (IKDC) questionnaires two years following surgery. Patients were then categorized based on whether their KOOS Quality of Life (QOL) score surpassed the Patient Acceptable Symptom State (PASS) threshold of 62.5 points or the IKDC PASS threshold of 75.9 points.

Results

Patients that failed to reach the QOL PASS threshold after surgery (n = 6, 27%) had significantly greater sf interleukin-1 alpha (IL-1α; p = 0.004), IL-1 receptor antagonist (IL-1ra; p = 0.03), and matrix metalloproteinase-9 (MMP-9; p = 0.01) concentrations on the day of surgery. Patients that failed to reach the IKDC PASS threshold (n = 9, 41%) had significantly greater sf IL-1α (p = 0.02).

Conclusion

These pilot data suggest that initial biochemical changes after injury may be an indicator of poor outcomes that are not mitigated by surgical stabilization alone. Biological adjuvant treatment in addition to ACL reconstruction may be beneficial; however, these data should be used for hypothesis generation and more definitive randomized clinical trials are necessary.

Characterizing human subchondral bone properties using near-infrared (NIR) spectroscopy

Degenerative joint conditions are often characterized by changes in articular cartilage and subchondral bone properties. These changes are often associated with subchondral plate thickness and trabecular bone morphology. Thus, evaluating subchondral bone integrity could provide essential insights for diagnosis of joint pathologies. This study investigates the potential of optical spectroscopy for characterizing human subchondral bone properties. Osteochondral samples (n = 50) were extracted from human cadaver knees (n = 13) at four anatomical locations and subjected to NIR spectroscopy. The samples were then imaged using micro-computed tomography to determine subchondral bone morphometric properties, including: plate thickness (Sb.Th), trabecular thickness (Tb.Th), volume fraction (BV/TV), and structure model index (SMI). The relationship between the subchondral bone properties and spectral data in the 1^st (650–950 nm), 2^nd (1100–1350 nm) and 3^rd (1600–1870 nm) optical windows were investigated using partial least squares (PLS) regression multivariate technique. Significant correlations (p < 0.0001) and relatively low prediction errors were obtained between spectral data in the 1^st optical window and Sb.Th (R² = 92.3%, error = 7.1%), Tb.Th (R² = 88.4%, error = 6.7%), BV/TV (R² = 83%, error = 9.8%) and SMI (R² = 79.7%, error = 10.8%). Thus, NIR spectroscopy in the 1^st tissue optical window is capable of characterizing and estimating subchondral bone properties, and can potentially be adapted during arthroscopy.

NLRP3 as a potentially novel biomarker for the management of osteoarthritis

Osteoarthritis (OA) was previously thought of as 'wear and tear' as humans age, however there is increasing evidence to support an inflammatory theory. The nucleotide-binding and oligomerization domain-like receptor containing protein 3 (NLRP3) inflammasome has been implicated in the pathogenesis of a number of arthritic disorders, producing proinflammatory cytokines and degradative enzymes such as Interleukin-1 beta (IL-1β), Tumour necrosis factor alpha (TNF-α) and Matrix metalloproteinase-3 (MMP-3) which drive cartilage degeneration and synovial inflammation. This review aims to summarise the evidence of NLRP3 involvement in OA. Currently, treatment options focus on management of the disease and to date there is no cure. The development of novel biomarkers for OA could improve diagnosis, treatment and management. Importantly, this review provides detail on the involvement of the NLRP3 inflammasome in OA pathology and how its members could act as potential biomarkers to assist clinical decisions.

Serum N-propeptide of collagen IIA (PIIANP) as a marker of radiographic osteoarthritis burden

OBJECTIVE

Cartilage homeostasis relies on a balance of catabolism and anabolism of cartilage matrix. Our goal was to evaluate the burden of radiographic osteoarthritis and serum levels of type IIA procollagen amino terminal propeptide (sPIIANP), a biomarker representing type II collagen synthesis, in osteoarthritis.

METHODS

OA burden was quantified on the basis of radiographic features as total joint faces with an osteophyte, joint space narrowing, or in the spine, disc space narrowing. sPIIANP was measured in 1,235 participants from the Genetics of Generalized Osteoarthritis study using a competitive enzyme-linked immunosorbent assay. Separate multivariable linear regression models, adjusted for age, sex, and body mass index and additionally for ipsilateral osteophytes or joint/disc space narrowing, were used to assess the independent association of sPIIANP with osteophytes and with joint/disc space narrowing burden in knees, hips, hands and spine, individually and together.

RESULTS

After full adjustment, sPIIANP was significantly associated with a lesser burden of hip joint space narrowing and knee osteophytes. sPIIANP was associated with a lesser burden of hand joint space narrowing but a greater burden of hand osteophytes; these results were only evident upon adjustment for osteoarthritic features in all other joints. There were no associations of sPIIANP and features of spine osteoarthritis.

CONCLUSIONS

Higher cartilage collagen synthesis, as reflected in systemic PIIANP concentrations, was associated with lesser burden of osteoarthritic features in lower extremity joints (knees and hips), even accounting for osteoarthritis burden in hands and spine, age, sex and body mass index. These results suggest that pro-anabolic agents may be appropriate for early treatment to prevent severe lower extremity large joint osteoarthritis.

Diagnostic value of combined serum marker changes and quantitative MRI evaluation of cartilage volume of tibial plateau in a surgically-induced osteoarthritis dog model

Objective

To evaluate the combined diagnostic value of two serum osteoarthritis (OA) markers and quantitative magnetic resonance imaging (MRI) evaluation of the cartilage volume of the tibial plateau in a canine model of experimental OA.

Methods

A total of 18 male Beagle dogs were used in this longitudinal study. OA was surgically induced via anterior cruciate ligament transection (ACLT) of the right knee in 10 dogs. The remaining eight dogs formed the sham operation control group and underwent the same procedure without ACLT. At various times after surgery, enzyme-linked immunosorbent assay was used to measure serum C-telopeptide of type II collagen (CTX-II) and type X collagen (ColX) levels. Quantitative evaluation of the tibial plateau volume was undertaken using MRI and ImageJ software.

Results

The serum CTX-II levels were significantly higher in the OA group at weeks 8, 12 and 16 after surgery, but not at week 4, compared with the control group. The serum ColX levels in the OA group were significantly higher than in the control group at weeks 8 and 12. The tibial plateau cartilage volumes in the OA group were significantly lower than in the control group at weeks 8 and 16.

Conclusion

Serum CTX-II and ColX levels combined with quantitative MRI evaluation of the tibial plateau cartilage volume in a canine model of OA demonstrated the potential to detect and monitor OA progression.

Meta-analysis of urinary C-terminal telopeptide of type II collagen as a biomarker in osteoarthritis diagnosis

Objective

This study aims to discover that the urinary C-terminal telopeptide of type II collagen (uCTX-II) levels differ between osteoarthritis (OA) patients and healthy individuals (controls). According to this difference, we may conclude that uCTX-II can be a biomarker for OA diagnosis.

Methods

We searched MEDLINE and EMBASE databases updated to 2014 to find literature on OA biomarkers. We retrieved the publications that met the required criterion. Literature quality was assessed according to the Newcastle-Ottawa Scale. Publication bias was assessed by Begg's test and Egger's test with the software STATA version 12.0. The weighted mean difference (WMD) was calculated, and the subgroup analysis was completed using STATA 12.0.

Results

Six publications were included in our analysis. The WMD for OA patients versus the controls was 83.05, which was within the 95% confidence interval. For subgroup analysis, the WMD of patients with severe OA was 119.92, whereas that of patients with mild OA was 28.07.

Conclusions

uCTX-II levels were higher in OA patients than in controls, subgroup analysis revealed that the uCTX-II levels rised with the OA severity, the heterogeneity originated from different levels of OA severity, These results showed that uCTX-II would be a promising clinical biomarker in OA diagnosis.