Osteoarthritis year in review 2015: soluble biomarkers and the BIPED criteria

Cartilage Collagen Neoepitope C2C Expression in the Articular Cartilage and Its Relation to Joint Tissue Damage in Patients with Knee Osteoarthritis

Pathological cleavage of type II collagen (Col2) and generation of Col2 neoepitopes can serve as useful molecular markers of the progression of osteoarthritis (OA). One of such potential biomarkers is type II collagen neoepitope C2C. The aim of this study was to correlate the degree of articular cartilage damage in OA patients with C2C expression in histological samples of tissues removed during total knee replacement. Cartilage samples were obtained from 27 patients ranging in age from 55 to 66 years. In each patient, medial and lateral tibia plateau samples were analyzed according to the OARSI histopathology grading system. The C2C expression was evaluated on histological slides by semi-quantitative analysis using ImageJ Fiji 2.14.0 software. Spearman's rank correlation analysis revealed a positive weak correlation (rho = 0.289, p = 0.0356) between the histological grade of tissue damage and the percentage of C2C staining. In addition, a highly significant positive correlation (rho = 0.388, p = 0.0041) was discovered between the osteoarthritis score (combining the histological grade of damage with the OA macroscopic stage) and the percentage of C2C staining in the samples. The C2C expression was detected in all the regions of the articular cartilage (i.e., the superficial zone, mid zone, deep zone and tidemark area, and the zone of calcified cartilage). Our findings imply that local expression of C2C correlates with the articular cartilage damage in OA-affected knees. This confirms that C2C can be used as a prospective marker for assessing pathological changes in the OA course and OA clinical trials.

Impact of diabetes mellitus on osteoarthritis: a scoping review on biomarkers

Osteoarthritis (OA) commonly affects the knee and hip joints and accounts for 19.3% of disability-adjusted life years and years lived with disability worldwide (Refs , ). Early management is important in order to avoid disability uphold quality of life (Ref. ). However, a lack of awareness of subclinical and early symptomatic stages of OA often hampers early management (Ref. ). Moreover, late diagnosis of OA among those with severe disease, at a stage when OA management becomes more complicated is common (Refs , , , ). Established risk factors for the development and progression of OA include increasing age, female, history of trauma and obesity (Ref. ). Recent studies have also drawn a link between OA and metabolic syndrome, which is characterized by insulin resistance, dyslipidaemia and hypertension (Refs , ).

Immobilization by 21 days of bed rest results in type II collagen degradation in healthy individuals

OBJECTIVE

To investigate the effects of 21 days of bed rest immobilization (with and without exercise and nutrition interventions) on type II collagen biomarker concentrations in healthy individuals.

DESIGN

Twelve healthy male participants (age 34.2 ± 8.3 years; body mass index 22.4 ± 1.7 kg/m²) were exposed to 6 days ambulatory baseline data collection (BDC), 21 days head-down-tilt bed rest (HDT, CON) + interventions (HDT + resistive vibration exercise (2 times/week, 25 minutes): RVE; HDT + RVE + whey protein (0.6 g/kg body weight/day) and bicarbonate supplementation (90 mmol KHCO3/day: NeX), and 6 days of re-ambulation (R) in a cross-over designed study. The starting HDT condition was randomized (CON-RVE-NEX, RVE-NEX-CON, NEX-CON-RVE). Blood and urine samples were collected before, during, and after HDT. Serum concentrations (s) of CPII, C2C, C1,2C, and urinary concentrations (u) of CTX-II and Coll2-1NO2 were measured.

RESULTS

Twenty-one days of HDT resulted in increased sCPII (p < 0.001), sC2C (p < 0.001), and sC1,2C (p = 0.001) (highest increases: sCPII (+24.2% - HDT5), sC2C (+24.4% - HDT7), sC1,2C (+13.5% - HDT2). sC2C remained elevated at R+1 (p = 0.002) and R+6 (p < 0.001) compared to baseline. NeX led to lower sCPII (p < 0.001) and sC1,2C (p = 0.003) compared to CON. uCTX-II (second void and 24-hour urine) increased during HDT (p < 0.001, highest increase on HDT21: second void +82.8% (p < 0.001); 24-hour urine + 77.8% (p < 0.001). NeX resulted in lower uCTX-II concentrations in 24-hour urine (p = 0.012) compared to CON.

CONCLUSIONS

Twenty-one days of bed rest immobilization results in type II collagen degradation that does not recover within 6 days of resuming ambulation. The combination of resistive vibration exercise and protein/bicarbonate supplementation minimally counteracted this effect.

From biochemical markers to molecular endotypes of osteoarthritis: a review on validated biomarkers

INTRODUCTION

Osteoarthritis (OA) affects over 500 million people worldwide. OA patients are symptomatically treated, and current therapies exhibit marginal efficacy and frequently carry safety-risks associated with chronic use. No disease-modifying therapies have been approved to date leaving surgical joint replacement as a last resort. To enable effective patient care and successful drug development there is an urgent need to uncover the pathobiological drivers of OA and how these translate into disease endotypes. Endotypes provide a more precise and mechanistic definition of disease subgroups than observable phenotypes, and a panel of tissue- and pathology-specific biochemical markers may uncover treatable endotypes of OA.

AREAS COVERED

We have searched PubMed for full-text articles written in English to provide an in-depth narrative review of a panel of validated biochemical markers utilized for endotyping of OA and their association to key OA pathologies.

EXPERT OPINION

As utilized in IMI-APPROACH and validated in OAI-FNIH, a panel of biochemical markers may uncover disease subgroups and facilitate the enrichment of treatable molecular endotypes for recruitment in therapeutic clinical trials. Understanding the link between biochemical markers and patient-reported outcomes and treatable endotypes that may respond to given therapies will pave the way for new drug development in OA.

Molecular Assessment of Healthy Pathological Articular Cartilages in Physically Active People: A Scoping Review

Physiological aging triggers a cascade of negative effects on the human body and the human joint is only one of the several compartments affected by this irreversible and natural process. Osteoarthritis and cartilage degeneration can cause pain and disability; therefore, identifying the molecular processes underlying these phenomena and the biomarkers produced during physical activity is of critical importance. In the present review, the main goal was to identify and discuss the articular cartilage biomarkers analyzed in studies in which physical or sports activities were adopted and eventually to propose a standard operating procedure for the assessment. Articles collected from Pubmed, Web of Science, and Scopus were scrutinized to detect reliable cartilage biomarkers. The principal articular cartilage biomarkers detected in these studies were cartilage oligomeric matrix protein, matrix metalloproteinases, interleukins, and carboxy-terminal telopeptide. The articular cartilage biomarkers identified in this scoping review may aid in a better comprehension of where research on the topic is heading and offer a viable instrument for streamlining investigations on cartilage biomarker discovery.

Correlation between Bone Mineral Density and Progression of Hip Osteoarthritis in Adult Men and Women in Bulgaria-Results from a 7-Year Study

Changes in clinical presentation, radiographic progression (RP), bone mineral density (BMD), bone turnover (BT), and cartilage turnover (CT) markers were compared in two groups of patients with hip osteoarthritis (HOA) over a period of 7 years. Each group consisted of 150 patients, including a control group on standard-of-care therapy (SC) with simple analgesics and physical exercises, and a study group (SG) on standard-of-care therapy supplemented by vitamin D3 and intravenous administration of zoledronic acid (5 mg) yearly for 3 consecutive years. Patient groups were homogenized regarding the following: (1) radiographic grade (RG), including 75 patients with hip OA RG II according to the Kellgren-Lawrence grading system (K/L), and 75 with RG III on K/L; (2) radiographic model (RM), as each of the K/L grades was subdivided into three subgroups consisting of 25 patients of different RMs: atrophic ('A'), intermediate ('I'), and hypertrophic ('H'); (3) gender-equal ratio of men and women in each subgroup (Female/Male = 15/10). The following parameters were assessed: (1) clinical parameters (CP), pain at walking (WP-VAS 100 mm), functional ability (WOMAC-C), and time to total hip replacement (tTHR); (2) radiographic indicators(RI)-joint space width (JSW) and speed of joint space narrowing (JSN), changes in BMD (DXA), including proximal femur (PF-BMD), lumbar spine (LS-BMD), and total body (TB-BMD); (3) laboratory parameters (LP)-vitamin D3 levels and levels of BT/CT markers. RV were assessed every 12 months, whereas CV/LV were assessed every 6 months. Results: Cross-sectional analysis (CsA) at baseline showed statistically significant differences (SSD) at p < 0.05 in CP (WP, WOMAC-C); BMD of all sites and levels of CT/BT markers between the 'A' and 'H' RM groups in all patients. Longitudinal analysis (LtA) showed SSD (p < 0.05) between CG and SG in all CP (WP, WOMAC-C, tTHR) parameters of RP (mJSW, JSN), BMD of all sites, and levels of CT/BT markers for all 'A' models and in 30% of 'I'-RMs (those with elevated markers for BT/CT at baseline and during the observation period). Conclusion: The presence of SSD at baseline ('A' vs. 'H') supported the thesis that at least two different subgroups of HOA exist: one associated with 'A' and the other with 'H' models. D3 supplementation and the intravenous administration of bisphosphonate were the treatment strategies that slowed down RP and postponed tTHR by over 12 months in the 'A' and 'I' RM with elevated BT/CT markers.

Soluble and EV-Associated Diagnostic and Prognostic Biomarkers in Knee Osteoarthritis Pathology and Detection

Osteoarthritis (OA) is the most common degenerative disease of the connective tissue of the human musculoskeletal system. Despite its widespread prevalence, there are many limitations in its diagnosis and treatment. OA diagnosis currently relies on the presence of clinical symptoms, sometimes accompanied by changes in joint X-rays or MRIs. Biomarkers help not only to diagnose early disease progression but also to understand the process of OA in many ways. In this article, we briefly summarize information on articular joints and joint tissues, the pathogenesis of OA and review the literature about biomarkers in the field of OA, specifically inflammatory cytokines/chemokines, proteins, miRNA, and metabolic biomarkers found in the blood, synovial fluid and in extracellular vesicles.

Human Mesenchymal Stem Cell-Derived Miniature Joint System for Disease Modeling and Drug Testing

Diseases of the knee joint such as osteoarthritis (OA) affect all joint elements. An in vitro human cell-derived microphysiological system capable of simulating intraarticular tissue crosstalk is desirable for studying etiologies/pathogenesis of joint diseases and testing potential therapeutics. Herein, a human mesenchymal stem cell-derived miniature joint system (miniJoint) is generated, in which engineered osteochondral complex, synovial-like fibrous tissue, and adipose tissue are integrated into a microfluidics-enabled bioreactor. This novel design facilitates different tissues communicating while still maintaining their respective phenotypes. The miniJoint exhibits physiologically relevant changes when exposed to interleukin-1β mediated inflammation, which are similar to observations in joint diseases in humans. The potential of the miniJoint in predicting in vivo efficacy of drug treatment is confirmed by testing the "therapeutic effect" of the nonsteroidal anti-inflammatory drug, naproxen, as well as four other potential disease-modifying OA drugs. The data demonstrate that the miniJoint recapitulates complex tissue interactions, thus providing a robust organ chip model for the study of joint pathology and the development of novel therapeutic interventions.

Location-Dependent Human Osteoarthritis Cartilage Response to Realistic Cyclic Loading: Ex-Vivo Analysis on Different Knee Compartments

Objective: Osteoarthritis (OA) is a multifactorial musculoskeletal disorder affecting mostly weight-bearing joints. Chondrocyte response to load is modulated by inflammatory mediators and factors involved in extracellular cartilage matrix (ECM) maintenance, but regulatory mechanisms are not fully clarified yet. By using a recently proposed experimental model combining biomechanical data with cartilage molecular information, basally and following ex-vivo load application, we aimed at improving the understanding of human cartilage response to cyclic mechanical compressive stimuli by including cartilage original anatomical position and OA degree as independent factors. Methods: 19 mono-compartmental Knee OA patients undergoing total knee replacement were recruited. Cartilage explants from four different femoral condyles zones and with different degeneration levels were collected. The response of cartilage samples, pooled according to OA score and anatomical position was tested ex-vivo in a bioreactor. Mechanical stimulation was obtained via a 3-MPa 1-Hz sinusoidal compressive load for 45-min to replicate average knee loading during normal walking. Samples were analysed for chondrocyte gene expression and ECM factor release. Results: Non parametric univariate and multivariate (generalized linear mixed model) analysis was performed to evaluate the effect of compression and IL-1β stimulation in relationship to the anatomical position, local disease severity and clinical parameters with a level of significance set at 0.05. We observed an anti-inflammatory effect of compression inducing a significant downmodulation of IL-6 and IL-8 levels correlated to the anatomical regions, but not to OA score. Moreover, ADAMTS5, PIICP, COMP and CS were upregulated by compression, whereas COL-2CAV was downmodulated, all in relationship to the anatomical position and to the OA degree. Conclusion: While unconfined compression testing may not be fully representative of the in-vivo biomechanical situation, this study demonstrates the importance to consider the original cartilage anatomical position for a reliable biomolecular analysis of knee OA metabolism following mechanical stimulation.

Relationship between different serum cartilage biomarkers in the acute response to running and jumping in healthy male individuals

The effect of physical activity on serum cartilage biomarkers is largely unknown. The purpose of the study was to systematically analyze the acute effect of two frequently used exercise interventions (running and jumping) on the correlation of seven serum biomarkers that reflect cartilage extracellular matrix metabolism. Fifteen healthy male volunteers (26 ± 4 years, 181 ± 4 cm, 77 ± 6 kg) participated in the repeated measurement study. In session 1, the participants accomplished 15 × 15 series of reactive jumps within 30 min. In session 2, they ran on a treadmill (2.2 m/s) for 30 min. Before and after both exercise protocols, four blood samples were drawn separated by 30 min intervals. Serum concentrations of seven biomarkers were determined: COMP, MMP-3, MMP-9, YKL-40, resistin, Coll2-1 and Coll2-1 NO₂. All biomarkers demonstrated an acute response to mechanical loading. Both the COMP and MMP-3 responses were significantly (p = 0.040 and p = 0.007) different between running and jumping (COMP: jumping + 31%, running + 37%; MMP-3: jumping + 14%, running + 78%). Resistin increased only significantly (p < 0.001) after running, and Coll2-1 NO₂ increased significantly (p = 0.001) only after jumping. Significant correlations between the biomarkers were detected. The relationships between individual serum biomarker concentrations may reflect the complex interactions between degrading enzymes and their substrates in ECM homeostasis.

Associations between biomarkers and histological assessment in individual animals in a destabilization of the medial meniscus (DMM) model of osteoarthritis (OA)

To date, the use of biomarkers for assessing individual severity of osteoarthritis (OA) is limited, and the correlation of histological scores with biomarkers for individual animals in the destabilization of the medial meniscus (DMM) model of OA has not been well investigated. Accordingly, this study investigated how well representative biomarkers in the DMM model reflected specific changes in individual animals. Rats were randomly divided into the OA group and the sham group. OA model was established by destabilization of the medial meniscus (DMM). After 2,4,6,8,10 and 12 weeks (n=14, each week), the concentrations of CTXII, COMP, C2C, and OC in serum were measured, and cartilage degeneration, osteophytes, and synovial membrane inflammation, typical of OA, were scored using Osteoarthritis Research Society International (OARSI) scoring system. Additionally, the correlation between each biomarker and the specific changes in osteoarthritis was analyzed for individual animals using the Generalized Estimating Equation (GEE). Statistical analysis showed a low correlation between CTXII and osteophyte score of the medial femur (coefficient = -0.0088, p= 0.0103), COMP and osteophyte score of the medial tibia (coefficient = -0.0911, p= 0.0003), and C2C and synovial membrane inflammation scores of the medial femoral (coefficient = 0.054, p= 0.0131). These results suggest that representative OA bio- markers in individual animals in the DMM model did not reflect histological scores well.

Synovial Fluid Cytokines, Chemokines and MMP Levels in Osteoarthritis Patients with Knee Pain Display a Profile Similar to Many Rheumatoid Arthritis Patients

Background: There are currently no effective disease-modifying drugs to prevent cartilage loss in osteoarthritis and synovial fluid is a potentially valuable source of biomarkers to understand the pathogenesis of different types of arthritis and identify drug responsiveness. The aim of this study was to compare the differences between SF cytokines and other proteins in patients with OA (n = 21) to those with RA (n = 27) and normal knees (n = 3). Methods: SF was obtained using ultrasound (US) guidance and an external pneumatic compression device. RA patients were categorized as active (n = 20) or controlled (n = 7) based upon SF white blood cell counts (> or <300 cells/mm³). Samples were cryopreserved and analyzed by multiplex fluorescent bead assays (Luminex). Between-group differences of 16 separate biomarker proteins were identified using ANOVA on log10-transformed concentrations with p values adjusted for multiple testing. Results: Only six biomarkers were significantly higher in SF from active RA compared to OA—TNF-α, IL-1-β IL-7, MMP-1, MMP-2, and MMP-3. Only MMP-8 levels in RA patients correlated with SF WBC counts (p < 0.0001). Among OA patients, simultaneous SF IL-4, IL-6, IL-8, and IL-15 levels were higher than serum levels, whereas MMP-8, MMP-9, and IL-18 levels were higher in serum (p < 0.05). Conclusion: These results support the growing evidence that OA patients have a pro-inflammatory/catabolic SF environment. SF biomarker analysis using multiplex testing and US guidance may distinguish OA phenotypes and identify treatment options based upon targeted inflammatory pathways similar to patients with RA.

Evidence of acrolein in synovial fluid of dogs with osteoarthritis as a potential inflammatory biomarker

BACKGROUND

Acrolein is a known pro-inflammatory toxic aldehyde, propagating cellular damage and tissue inflammation in humans and animal models of various diseases. Osteoarthritis (OA) has a significant inflammatory component; however, presence of acrolein in synovial fluid of joints with OA has not been previously reported. The first aim of this study was to evaluate evidence of acrolein in the synovial fluid of dogs with OA as well as in Control joints. The second aim was to determine if evidence of acrolein can be detected in synovial fluid samples that have been in a frozen state for long periods of time.

METHODS

In this pilot clinical study, synovial fluid samples were prospectively collected (i.e., New samples) from a single joint of both clinically healthy (New Control, n = 5) and dogs with OA (New OA, n = 16) and frozen until the time of analysis. Additionally, frozen synovial fluid samples from a biobank (i.e., Old samples) were used to evaluate ability to detect evidence of acrolein in long-term stored samples (median of 4.89 years) in Old Control (n = 5) and Old OA (n = 5) samples. Measurements of acrolein in all synovial fluid samples was based on detection of its major protein adduct, N ε - (3-formyl-3, 4-dehydropiperidino)lysine (FDP-lysine), using the western blot method. Synovial fluid matrix metalloproteinase 2 (MMP2) was measured in all samples using the western blot method as a positive control of OA inflammation.

RESULTS

Acrolein-lysine adduct was detected in both Control (n = 10) and OA (n = 21) groups in both Old and New samples. Acrolein-lysine adduct and MMP2 were detectable at a lower level in the Old compared to New synovial fluid samples; however, the differences were not statistically significant (p > 0.1). The measured MMP2 levels were significantly higher in the OA compared to Control group samples (p = 0.033), but not for acrolein-lysine adduct (p = 0.30).

CONCLUSIONS

This study confirmed evidence of acrolein in canine synovial fluid of both OA and Control groups. Freezing of synovial fluid for up to 5 years does not appear to significantly affect the ability to detect acrolein-lysine adduct and MMP2 in these samples.

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.

Osteoarthritis: Current Molecular Biomarkers and the Way Forward

The ultimate hope of researchers and patients is a pathway to development of treatments for osteoarthritis to modify the disease process in addition to the symptoms. However, development of disease modifying drugs requires objective endpoints such as measures of joint structure, joint tissue homeostasis and/or joint survival-measures such as provided by imaging biomarkers, molecular biomarkers and joint replacement frequency, respectively. Although biomarkers supporting investigational drug use and drug approval include surrogate endpoints that may not necessarily reflect or directly correlate with the clinical outcome of interest, a formal biomarker qualification process currently exists that is a rigorous three stage process that yields biomarker approvals (or denials) for specific contexts of use. From a cost perspective, biochemical biomarkers are the 'ones to beat'; however, even well-validated biomarkers may not cross the translation gaps for eventual use in healthcare unless they offer an advantage in terms of cost per quality adjusted life year. This review summarizes the case FOR and AGAINST biomarkers in drug development and highlights the current data for a subset of biomarkers in the osteoarthritis research field informing on cartilage homeostasis, joint inflammation and altered subchondral bone remodeling.

Considerations for understanding protein measurements: Identification of formation, degradation and more pathological relevant epitopes

OBJECTIVES

There is a need for precision medicine and an unspoken promise of an optimal approach for identification of the right patients for value-based medicine based on big data. However, there may be a misconception that measurement of proteins is more valuable than measurement of fewer selected biomarkers. In population-based research, variation may be somewhat eliminated by quantity. However, this fascination of numbers may limit the attention to and understanding of the single. This review highlights that protein measurements (with collagens as examples) may mean different things depending on the targeted epitope - formation or degradation of tissues, and even signaling potential of proteins.

DESIGN AND METHODS

PubMed was searched for collagen, neo-epitope, biomarkers.

RESULTS

Ample examples of assays with specific epitopes, either pathological such as HbA1c, or domain specific such as pro-peptides, which total protein arrays would not have identified were evident.

CONCLUSIONS

We suggest that big data may be considered as the funnel of data points, in which most important parameters will be selected. If the technical precision is low or the biological accuracy is limited, and we include suboptimal quality of biomarkers, disguised as big data, we may not be able to fulfill the promise of helping patients searching for the optimal treatment. Alternatively, if the technical precision of the total protein quantification is high, but we miss the functional domains with the most considerable biological meaning, we miss the most important and valuable information of a given protein. This review highlights that measurements of the same protein in different ways may provide completely different meanings. We need to understand the pathological importance of each epitope quantified to maximize protein measurements.

Decision Support Systems in Temporomandibular Joint Osteoarthritis: A review of Data Science and Artificial Intelligence Applications

With the exponential growth of computational systems and increased patient data acquisition, dental research faces new challenges to manage a large quantity of information. For this reason, data science approaches are needed for the integrative diagnosis of multifactorial diseases, such as Temporomandibular joint (TMJ) Osteoarthritis (OA). The Data science spectrum includes data capture/acquisition, data processing with optimized web-based storage and management, data analytics involving in-depth statistical analysis, machine learning (ML) approaches, and data communication. Artificial intelligence (AI) plays a crucial role in this process. It consists of developing computational systems that can perform human intelligence tasks, such as disease diagnosis, using many features to help in the decision-making support. Patient's clinical parameters, imaging exams, and molecular data are used as the input in cross-validation tasks, and human annotation/diagnosis is also used as the gold standard to train computational learning models and automatic disease classifiers. This paper aims to review and describe AI and ML techniques to diagnose TMJ OA and data science approaches for imaging processing. We used a web-based system for multi-center data communication, algorithms integration, statistics deployment, and process the computational machine learning models. We successfully show AI and data-science applications using patients' data to improve the TMJ OA diagnosis decision-making towards personalized medicine.

Protein Levels and Microstructural Changes in Localized Regions of Early Cartilage Degeneration Compared with Adjacent Intact Cartilage

OBJECTIVE

It was hypothesized that the respective protein profiles of bovine cartilage from sites of localized mild to moderate (GI to GII) degeneration versus adjacent sites of intact tissue would vary in accordance with the tissue microstructural changes associated with a pre-osteoarthritic state.

METHODS

A total of 15 bovine patellae were obtained for this study. Paired samples of tissue were collected from the lateral region of each patella. If the patella contained a site of degeneration, a paired tissue set involved taking one sample each from the degenerated site and the intact tissue adjacent to it. Sufficient tissue was collected to facilitate 2 arms of investigation: microstructural imaging and proteome analysis. The microstructural analysis used a bespoke tissue preparation technique imaged with differential interference contrast optical microscopy to assess fibrillar scale destructuring and underlying bone spicule formation. An iTRAQ-based proteome analysis was performed using liquid chromatography-tandem mass spectrometry to identify the differential levels of proteins across the intact and degenerated cartilage and further, the results were validated with multiple reaction monitoring assay.

RESULTS

In the healthy cartilage pairs, there was no significant variation in protein profiles between 2 adjacent sample sites. In pairs of tissue that contained a sample of GI/GII tissue, there were both significant microstructural changes as well as the difference in abundance levels of 24 proteins.

CONCLUSIONS

From the known functions of the 24 proteins, found to be strongly aligned with the specific microstructural changes observed, a unique "proteins ensemble" involved in the initiation and progression of early cartilage degeneration is proposed.

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.

Intra-articular collagenase in the spinal facet joint induces pain, DRG neuron dysregulation and increased MMP-1 absent evidence of joint destruction

Degeneration is a hallmark of painful joint disease and is mediated by many proteases that degrade joint tissues, including collagenases. We hypothesized that purified bacterial collagenase would initiate nociceptive cascades in the joint by degrading the capsular ligament's matrix and activating innervating pain fibers. Intra-articular collagenase in the rat facet joint was investigated for its effects on behavioral sensitivity, joint degeneration, and nociceptive pathways in the peripheral and central nervous systems. In parallel, a co-culture collagen gel model of the ligament was used to evaluate effects of collagenase on microscale changes to the collagen fibers and embedded neurons. Collagenase induced sensitivity within one day, lasting for 3 weeks (p < 0.001) but did not alter ligament structure, cartilage health, or chondrocyte homeostasis. Yet, nociceptive mediators were increased in the periphery (substance P, pERK, and MMP-1; p ≤ 0.039) and spinal cord (substance P and MMP-1; p ≤ 0.041). The collagen loss (p = 0.008) induced by exposing co-cultures to collagenase was accompanied by altered neuronal activity (p = 0.002) and elevated neuronal MMP-1 (p < 0.001), suggesting microscale collagen degradation mediates sensitivity in vivo. The induction of sustained sensitivity and nociception without joint damage may explain the clinical disconnect in which symptomatic joint pain patients present without radiographic evidence of joint destruction.

The effect of running on knee joint cartilage: A systematic review and meta-analysis

OBJECTIVE

Although running causes inevitable stress to the joints, data regarding its effect on the cartilage of the knee are conflicting. This systematic review and meta-analysis aimed to evaluate the effect of running on knee joint cartilage.

METHODS

PubMed, EMBASE, SportDiscus, and Cochrane Library databases were searched to identify randomized controlled trials (RCTs) and cohort studies. The outcome indicators were cartilage oligomeric matrix protein (COMP), cartilage volume and thickness, and T2.

RESULTS

A total of two RCTs and 13 cohort studies were included. There was no significant difference in cartilage volume between the running and control groups (MD, -115.88 U/I; 95% CI, -320.03 to 88.27; p = 0.27). However, running would decrease cartilage thickness (MD, -0.09 mm; 95%CI, -0.18 to -0.01; p = 0.03) and T2 (MD, -2.78 ms; 95% CI, -4.12 to -1.45; p < 0.001). Subgroup analysis demonstrated that COMP immediately or at 0.5 h after running was significantly increased, but there were no significant changes at 1 h or 2 h.

CONCLUSIONS

Running has advantages in promoting nutrition penetrating into the cartilage as well as squeezing out the metabolic substance, such as water. Our study found that running had a short-term adverse effect on COMP and did not affect cartilage volume or thickness.

Synovial fluid peptidase activity as a biomarker for knee osteoarthritis clinical progression

AIMS

To analyze the potential role of synovial fluid peptidase activity as a measure of disease burden and predictive biomarker of progression in knee osteoarthritis (KOA).

METHODS

A cross-sectional study of 39 patients (women 71.8%, men 28.2%; mean age of 72.03 years (SD 1.15) with advanced KOA (Ahlbäck grade ≥ 3 and clinical indications for arthrocentesis) recruited through the (Orthopaedic Department at the Complejo Asistencial Universitario de León, Spain (CAULE)), measuring synovial fluid levels of puromycin-sensitive aminopeptidase (PSA), neutral aminopeptidase (NAP), aminopeptidase B (APB), prolyl endopeptidase (PEP), aspartate aminopeptidase (ASP), glutamyl aminopeptidase (GLU) and pyroglutamyl aminopeptidase (PGAP).

RESULTS

Synovial fluid peptidase activity varied significantly as a function of clinical signs, with differences in levels of PEP (p = 0.020), ASP (p < 0.001), and PGAP (p = 0. 003) associated with knee locking, PEP (p = 0.006), ASP (p = 0.001), GLU (p = 0.037), and PGAP (p = 0.000) with knee failure, and PEP (p = 0.006), ASP (p = 0.001), GLU (p = 0.037), and PGAP (p < 0.001) with knee effusion. Further, patients with the greatest functional impairment had significantly higher levels of APB (p = 0.005), PEP (p = 0.005), ASP (p = 0.006), GLU (p = 0.020), and PGAP (p < 0.001) activity, though not of NAP or PSA, indicating local alterations in the renin-angiotensin system. A binary logistic regression model showed that PSA was protective (p = 0.005; Exp (B) 0.949), whereas PEP (p = 0.005) and GLU were risk factors (p = 0.012).

CONCLUSION

These results suggest synovial fluid peptidase activity could play a role as a measure of disease burden and predictive biomarker of progression in KOA. Cite this article: Bone Joint Res 2020;9(11):789-797.

Impact of knee joint loading on fragmentation of serum cartilage oligomeric matrix protein

The aim of the study was to examine the effect of mechanical knee joint loading on the fragmentation pattern of serum cartilage oligomeric matrix protein (COMP). Ten healthy men ran with knee orthoses that were passive or active (+30.9 N·m external flexion moments) on a treadmill (30 minute; v = 2.2 m/s). Lower-limb mechanics, serum COMP levels, and fragmentation patterns (baseline; 0, 0.5, 1, 2 hours postrunning) were analyzed. Running with active orthoses enhanced knee flexion moments, ankle dorsiflexion, and knee flexion angles (P < .05). There was an increase in serum COMP (+25%; pre: 8.9 ± 2.4 U/l; post: 10.7 ± 1.9 U/l, P = .001), COMP pentamer/tetramer (+88%; 1.88 ± 0.81, P = .007), trimer (+209%; 3.09 ± 2.65, P = .005), and monomer (+78%; 1.78 ± 0.85, P = .007) after running with passive orthoses and in serum COMP (+41%; pre: 8.5 ± 2.7 U/l; post: 11.3 ± 2.1 U/l, P < .001), COMP pentamer/tetramer (+57%; 1.57 ± 0.39, P = .007), trimer (+86%; 1.86 ± 0.47, P = .005), and monomer (+19%; 1.19 ± 0.34, P = .114) after running with active orthoses. Increased fragmentation might indicate COMP release from cartilage while running. Interestingly, 0.5 h up to 2 hours after running with passive orthoses, trimer (0.5 hour: 2.73 ± 3.40, P = .029; 2 hours: 2.33 ± 2.88, P = .037), and monomer (0.5 hour: 2.23 ± 2.33, P = .007; 1 hour: 2.55 ± 1.96, P = .012; 2 hours: 2.65 ± 2.50, P = .009) increased while after running with active orthoses, pentamer/tetramer (1 hour: 0.79 ± 0.28, P = .029), and trimer (1 hour: 0.63 ± 0.14, P = .005; 2 hours: 0.68 ± 0.34, P = .047) decreased. It seems that COMP degradation and clearance vary depending on joint loading characteristics.

Recent advances in understanding the phenotypes of osteoarthritis

Recent research in the field of osteoarthritis (OA) has focused on understanding the underlying molecular and clinical phenotypes of the disease. This narrative review article focuses on recent advances in our understanding of the phenotypes of OA and proposes that the disease represents a diversity of clinical phenotypes that are underpinned by a number of molecular mechanisms, which may be shared by several phenotypes and targeted more specifically for therapeutic purposes. The clinical phenotypes of OA supposedly have different underlying etiologies and pathogenic pathways and they progress at different rates. Large OA population cohorts consist of a majority of patients whose disease progresses slowly and a minority of individuals whose disease may progress faster. The ability to identify the people with relatively rapidly progressing OA can transform clinical trials and enhance their efficiency. The identification, characterization, and classification of molecular phenotypes of rapidly progressing OA, which represent patients who may benefit most from intervention, could potentially serve as the basis for precision medicine for this disabling condition. Imaging and biochemical markers (biomarkers) are important diagnostic and research tools that can assist with this challenge.

Guggulipid ameliorates adjuvant-induced arthritis and liver oxidative damage by suppressing inflammatory and oxidative stress mediators

BACKGROUND

Arthritis is a common degenerative joint disease characterized by deterioration of articular cartilage, subchondral bone, and associated with immobility, pain and inflammation. The incessant action of reactive oxygen species (ROS) during progressive arthritis causes severe oxidative damage to vital organs and circulatory system.

PURPOSE

In this study we investigated the ability of guggulipid (GL), a lipid rich extract from the gum resin of the plant Commiphora whighitii to suppress the progressive arthritis and associated liver oxidative stress both in vivo and in vitro.

STUDY DESIGN/METHODS

The anti-arthritic ability of GL was demonstrated in vitro using IL-1β stimulated bovine nasal cartilage model and in vivo Freund's complete adjuvant-induced arthritic rat model. Collagen/proteoglycan degradation and pro-inflammatory mediators were monitored in the harvested culture medium of nasal cartilage by estimating the levels of matrix metalloproteinases (MMPs), hydroxy proline, glycosaminoglycans and inflammatory mediators. Further, anti-arthritic ability of GL was evaluated in vivo by measuring enzymatic and non-enzymatic mediators of cartilage degradation, inflammation and oxidative stress markers.

RESULTS

GL significantly inhibited the IL-1β stimulated cartilage degradation in vitro by mitigating the MMPs activity, collagen degradation and secretion of pro-inflammatory mediators. Further, GL significantly reduced the adjuvant-induced paw swelling and body weight loss in vivo. GL remarkably reduced the MMPs and hyaluronidases activities in serum and bone homogenate along with altered hematological parameters. GL also mitigated the elevated bone resorbing enzymes cathepsins, exoglycosidases and phosphatases. Additionally, GL effectively mitigated ROS and oxidative stress-mediators recuperating the altered serum/liver oxidative stress and liver damage incurred during arthritic progression.

CONCLUSION

In summary, the study clearly demonstrates the protective efficacy of GL against arthritis and its associated oxidative stress, particularly, liver oxidative damage. Hence, GL could be a potential alternative and complementary medicine to treat inflammatory joint diseases.

Association of UCMA levels in serum and synovial fluid with severity of knee osteoarthritis

AIM

Osteoarthritis (OA) is one of the most common joint diseases causing physical disability in the aged population. OA pathogenesis is not fully known and yet there are no effective therapeutic options against OA. Upper Zone of Growth Plate and Cartilage Matrix Associated (UCMA) is a member of vitamin K-dependent protein family, and is involved in inflammation, cardiovascular diseases, cancer, and OA. In the present study, our aim was to detect serum and synovial fluid (SF) levels of UCMA and to analyze their correlation with radiographic findings and symptomatic severity in OA patients as well as the correlation between oxidative stress levels and SF UCMA levels.

METHODS

Forty OA patients with cartilage degeneration and 20 patients with other knee joint disorders (non-OA control) were included in the present study. We used the Kellgren-Lawrence (KL) classification and Western Ontario McMaster University Osteoarthritis Index (WOMAC) scores to assess radiographic grading and symptomatic severity of OA, respectively. UCMA levels were measured in SF and serum. And also oxidative stress markers were analyzed in SF.

RESULTS

SF UCMA levels of OA patients were higher compared to those of the non-OA control group and were positively correlated with radiographic finding and symptomatic severity of OA. However, there was no significant correlation between oxidative markers of SF and the KL grade, WOMAC scores, and SF UCMA levels in OA patients.

CONCLUSION

There is a close connection between UCMA SF levels and symptomatic and radiographic severities of knee OA. Therefore, UCMA can be a promising biomarker in the diagnosis and/or prognosis of OA disease.

Articular fibrocartilage - Why does hyaline cartilage fail to repair?

Once damaged, articular cartilage has a limited potential to repair. Clinically, a repair tissue is formed, yet, it is often mechanically inferior fibrocartilage. The use of monolayer expanded versus naïve cells may explain one of the biggest discrepancies in mesenchymal stromal/stem cell (MSC) based cartilage regeneration. Namely, studies utilizing monolayer expanded MSCs, as indicated by numerous in vitro studies, report as a main limitation the induction of type X collagen and hypertrophy, a phenotype associated with endochondral bone formation. However, marrow stimulation and transfer studies report a mechanically inferior collagen I/II fibrocartilage as the main outcome. Therefore, this review will highlight the collagen species produced during the different therapeutic approaches. New developments in scaffold design and delivery of therapeutic molecules will be described. Potential future directions towards clinical translation will be discussed. New delivery mechanisms are being developed and they offer new hope in targeted therapeutic delivery.

Bone Marrow Mesenchymal Stromal Cell Treatment in Patients with Osteoarthritis Results in Overall Improvement in Pain and Symptoms and Reduces Synovial Inflammation

Patients with late‐stage Kellgren‐Lawrence knee osteoarthritis received a single intra‐articular injection of 1, 10, or 50 million bone marrow mesenchymal stromal cells (BM‐MSCs) in a phase I/IIa trial to assess safety and efficacy using a broad toolset of analytical methods. Besides safety, outcomes included patient‐reported outcome measures (PROMs): Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); contrast‐enhanced magnetic resonance imaging (MRI) for cartilage morphology (Whole Organ MRI Scores [WORMS]), collagen content (T2 scores), and synovitis; and inflammation and cartilage turnover biomarkers, all over 12 months. BM‐MSCs were characterized by a panel of anti‐inflammatory markers to predict clinical efficacy. There were no serious adverse events, although four patients had minor, transient adverse events. There were significant overall improvements in KOOS pain, symptoms, quality of life, and WOMAC stiffness relative to baseline; the 50 million dose achieved clinically relevant improvements across most PROMs. WORMS and T2 scores did not change relative to baseline. However, cartilage catabolic biomarkers and MRI synovitis were significantly lower at higher doses. Pro‐inflammatory monocytes/macrophages and interleukin 12 levels decreased in the synovial fluid after MSC injection. The panel of BM‐MSC anti‐inflammatory markers was strongly predictive of PROMs over 12 months. Autologous BM‐MSCs are safe and result in significant improvements in PROMs at 12 months. Our analytical tools provide important insights into BM‐MSC dosing and BM‐MSC reduction of synovial inflammation and cartilage degradation and provide a highly predictive donor selection criterion that will be critical in translating MSC therapy for osteoarthritis. stem cells translational medicine2019;8:746&757

Serum cartilage oligomeric matrix protein (COMP) expression in individuals who sustained a youth sport-related intra-articular knee injury 3-10 years previously and uninjured matched controls

OBJECTIVE

This study investigates the relationship between a youth sport-related intra-articular knee injury and cartilage oligomeric matrix protein (COMP), a biomarker of cartilage turnover.

DESIGN

Participants included a sub-sample (n = 170) of the Alberta Youth Prevention of Early Osteoarthritis (PrE-OA) study group. Specifically, 85 individuals with a 3-10 year history of sport-related intra-articular knee injury and 85 age, sex and sport-matched controls. COMP levels were investigated in serum. Between group differences in COMP levels, COMP fragmentation patterns and, the relationship between serum COMP and clinical outcomes (i.e., Magnetic Resonance Imaging (MRI) Osteoarthritis Knee Score; MOAKS, Knee Osteoarthritis Outcome Score; KOOS, Fat mass index; FMI) were examined.

RESULTS

Participant median age was 22.3 years (range 16-26) and 63% were female. Although there was no difference in COMP levels between previously injured and uninjured females, previously injured males demonstrated an ∼15% greater (171.5 ng/ml, 95% CI 11.0-428.0, P = 0.04) serum COMP level than uninjured males. However after controlling for FMI, this difference was absent. Within the injured participants, COMP levels were associated with MOAKS_SYNOVITIS and FMI. Furthermore, COMP fragmentation patterns were distinct between injured and uninjured individuals.

CONCLUSIONS

In this study group, serum COMP levels were greater in injured males, but not females, compared to matched controls. However, after controlling for FMI, no differences in COMP were observed. A unique COMP fragmentation pattern was observed in injured vs uninjured participants. These results further the hypothesis that COMP levels and/or degradation of the protein may be a marker of cartilage injury which could predispose to later OA.

Dose-response relationship between ambulatory load magnitude and load-induced changes in COMP in young healthy adults

OBJECTIVE

To determine the dose-response relationship between ambulatory load magnitude during a walking stress test and load-induced changes in serum concentration of cartilage oligomeric matrix protein (sCOMP) in healthy subjects.

DESIGN

sCOMP was assessed before and after a 30-min walking stress test performed on three test days by 24 healthy volunteers. In each walking stress test, one of three ambulatory loads was applied in a block randomized crossover design: normal body weight (BW) (100%BW = normal load); reduced BW (80%BW = reduced load); increased BW (120%BW = increased load). Knee kinematics and ground reaction force (GRF) were measured using an inertial sensor gait analysis system and a pressure plate embedded in the treadmill.

RESULTS

Load-induced increases in sCOMP rose with increasing ambulatory load magnitude. Mean sCOMP levels increased immediately after the walking stress test by 26.8 ± 12.8%, 28.0 ± 13.3% and 37.3 ± 18.3% for the reduced, normal or increased load condition, respectively. Lower extremity kinematics did not differ between conditions.

CONCLUSIONS

The results of this study provide important evidence of a dose-response relationship between ambulatory load magnitude and load-induced changes in sCOMP. Our data suggests that in normal weight persons sCOMP levels are more sensitive to increased than to reduced load. The experimental framework presented here may form the basis for studying the relevance of the dose-response relationship between ambulatory load magnitude and load-induced changes in biomarkers involved in metabolism of healthy articular cartilage and after injury.

Influence of a periodized circuit training protocol on intermuscular adipose tissue of patients with knee osteoarthritis: protocol for a randomized controlled trial

BACKGROUND

The objective of this study is to analyze the influence of a 14-week periodized circuit training protocol on patients with knee osteoarthritis (OA), in randomized intervention groups, on thigh intermuscular adipose tissue (interMAT), body composition, systemic inflammation, cartilage degradation, and its repercussion on pain, functional performance and quality of life.

METHODS

This study presents a protocol for a randomized controlled trial. Sixty selected participants diagnosed with knee OA grades II and III, 40-65 years old and BMI < 30 kg/m2, will be randomly divided into three groups:periodized circuit training, strength training, and educational protocol. The circuit training and strength training protocols consist of 14-week training protocols conducted 3 times a week. The circuit training group will perform selected exercises previously stratified as light, moderate, and intense, arranged progressively in a circuit model, the strength group will perform regular strength exercises, and the educational protocol group will participate in a 14-week protocol with lectures twice a month about healthy lifestyles. Baseline and follow-up evaluations will be conducted for thigh interMAT (computed tomography), body composition (DXA), inflammation (IL-1β, IL-6, IL-10, TNF-α, leptin, and adiponectin), and joint degradation biomarkers (uCTX-II and sCOMP), performance-based tests (30s Chair Stand Test, 40 m Fast-paced Walk Test and Stair Climb Test), quadriceps and hamstring maximal isometric voluntary contraction (MIVC), and questionnaires (WOMAC and pain catastrophizing scale). Repeated measures ANOVA will be used to compare differences between groups (circuit training X strength training X educational protocol) at the different times of assessment (baseline x follow-up or baseline x during protocol x follow-up) for each of the dependent variables. When significant main effects were found, the pots hoc Bonferroni test will be used to identify statistical differences. A significance level of 5% (p < 0.05) will be adopted.

DISCUSSION

This will be the first randomized controlled trial to assess the effects of a circuit training protocol on patients with knee OA on thigh intermuscular adipose tissue (interMAT). Given the prevalence and impact of OA and the widespread availability of this intervention, assessing the efficacy of a low-cost, non-pharmacological, and non-invasive treatment for knee OA patients has the potential for immediate and high clinical impact.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02761590 , registered in May 4, 2016.

Cartilage oligomeric matrix protein: COMPopathies and beyond

Cartilage oligomeric matrix protein (COMP) is a large pentameric glycoprotein that interacts with multiple extracellular matrix proteins in cartilage and other tissues. While, COMP is known to play a role in collagen secretion and fibrillogenesis, chondrocyte proliferation and mechanical strength of tendons, the complete range of COMP functions remains to be defined. COMPopathies describe pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED), two skeletal dysplasias caused by autosomal dominant COMP mutations. The majority of the mutations are in the calcium binding domains and compromise protein folding. COMPopathies are ER storage disorders in which the retention of COMP in the chondrocyte ER stimulates overwhelming cellular stress. The retention causes oxidative and inflammation processes leading to chondrocyte death and loss of long bone growth. In contrast, dysregulation of wild-type COMP expression is found in numerous diseases including: fibrosis, cardiomyopathy and breast and prostate cancers. The most exciting clinical application is the use of COMP as a biomarker for idiopathic pulmonary fibrosis and cartilage degeneration associated osteoarthritis and rheumatoid and, as a prognostic marker for joint injury. The ever expanding roles of COMP in single gene disorders and multifactorial diseases will lead to a better understanding of its functions in ECM and tissue homeostasis towards the goal of developing new therapeutic avenues.

Soluble biochemical markers of osteoarthritis: Are we close to using them in clinical practice?

Osteoarthritis (OA) is the most common form of arthritis and a major cause of pain and disability. Recent work suggests that the global burden of OA is increasing, and costs associated with treatment are expected to increase dramatically as the aging human population expands. OA is currently diagnosed using radiography, but this technique is an indirect and insensitive measure of alterations in articular cartilage and fails to measure dynamic inflammatory processes in the joint. Radiographic changes detected overtime are small and occur in only a subset (progressors) of patients with OA. Therefore, we diagnose patients with OA on the basis of a diagnostic classification that is outdated. We also use the same tools and approaches for assessing the efficacy of new pharmacological and nonpharmacological interventions. In this review, we discuss the utility of soluble biochemical markers as biomarkers of OA and discuss whether we are close to using them in clinical practice. Combining patient information, functional imaging and carefully selected panels of biomarkers can help in achieving enhanced patient stratification and lead to better designed clinical trials. Biomarkers can be used for molecular endotyping and for developing more effective and more personalized treatments that will enhance clinical care for patients with OA.

GPR120 is an important inflammatory regulator in the development of osteoarthritis

Background

The aim of this study was to investigate the regulatory role of G-protein coupled receptor 120 (GPR120) in the development and progression of osteoarthritis (OA).

Methods

GPR120 knockout (KO) and wild-type (WT) mice were used to create an animal model of OA by means of anterior cruciate ligament transection (ACLT) surgery. The severity of OA was staged and evaluated by histological examination, microcomputed tomography scan and enzyme-linked immunosorbent assay (ELISA). The anti-inflammatory effects of the GPR120 agonist docosahexaenoic acid (DHA) on human chondrocytes were further evaluated by specific inflammatory markers. In addition, the healing progression of a skin defect model was determined with histological assays.

Results

The GPR120-KO mice displayed an accelerated development of OA after ACLT. The secondary inflammation, cartilage degeneration, and subchondral bone aberrant changes were significantly elevated in the early phase of OA in KO mice relative to those in WT mice. In addition, we found that GPR120 levels were downregulated in OA patients compared with control subjects, whereas GPR120 activation with DHA exhibited anti-inflammatory effects in primary human chondrocytes in vitro. Moreover, results from the skin defect model showed that GPR120 agonism with DHA enhanced wound repair in mice, as shown by the downregulation of the number of CD68⁺ cells.

Conclusions

Our study suggests that GPR120 is an important inflammatory mediator during the development of OA, and that it is a potential marker for the diagnosis of high-risk patients with OA.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1660-6) contains supplementary material, which is available to authorized users.

Effect of increased mechanical knee joint loading during running on the serum concentration of cartilage oligomeric matrix protein (COMP)

The purpose of the study was to investigate the effect of an increase in mechanical knee joint loading during running on the serum COMP level. On two different test days, 20 healthy men ran with knee orthoses for 30 min on a treadmill (v = 2.2 m/s). On day 1, the orthoses were passive, whereas on day 2 they were pneumatically driven (active) and thus increased the external knee flexion moments (+30.9 Nm) during stance phase. Lower-limb mechanics and serum COMP levels (baseline; 0, 0.5, 1, 2 h post running) were analyzed. COMP levels increased immediately after running with passive (+35%; pre: 7.5 U/l, 95%CI: 6.4, 8.7, post: 9.8 U/l, 95%CI: 8.8, 10.8, p < 0.001) and active orthoses (+45%; pre: 7.6 U/l; 95%CI: 6.4, 8.8, post: 10.3 U/l, 95%CI: 9.2, 11.5, p < 0.001), but they did not differ between interventions. While running with active orthoses, greater ankle dorsiflexion angles, knee flexion angles, and moments occurred (p < 0.05). Comparing both interventions, the Δ COMP pre-post, meaning the difference (Δ) between running with active and passive orthoses in pre to post COMP level change (=level after (post) running minus level before (pre) running), correlated negatively with Δ COMP baseline (difference between the baseline COMP level before running with active and passive orthoses, r = -0.616; p = 0.004), and with a positive tendence with the Δ maximum knee flexion (r = 0.388; p = 0.091). Therefore, changes in COMP concentration after physical activity seem to be highly influenced by the COMP baseline level. In addition, correlation analysis indicates that modifications in knee joint kinematics have a greater effect on cartilage metabolism than an increase in joint moments. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1937-1946, 2018.

Research methodology for orthopaedic surgeons, with a focus on outcome

Since improving the patient's condition is the ultimate goal of clinical care and research, this review of research methodology focuses on outcomes in the musculoskeletal field.This paper provides an overview of conceptual models, different types of outcomes and commonly assessed outcomes in orthopaedics as well as epidemiological and statistical aspects of outcomes determination, measurement and interpretation.Clinicians should determine the outcome(s) most important to patients and/or public health in collaboration with the patients, epidemiologists/statisticians and other stakeholders.Key points in outcome choice are to evaluate both the benefit and harm of a health intervention, and to consider short- and longer-term outcomes including patient-reported outcomes.Outcome estimation should aim at identifying a clinically important difference (not the same as a statistically significant difference), at presenting measures of effects with confidence intervals and at taking the necessary steps to minimize bias. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170064.

Effects of dietary weight loss with and without exercise on interstitial matrix turnover and tissue inflammation biomarkers in adults with knee osteoarthritis: the Intensive Diet and Exercise for Arthritis trial (IDEA)

OBJECTIVE

To examine the effects of dietary weight loss, with and without exercise, on selected soluble biomarkers in overweight and obese older adults with symptomatic knee osteoarthritis (OA).

DESIGN

Blood samples were analyzed from 429 participants in the Intensive Diet and Exercise for Arthritis (IDEA) trial randomized to either an 18 month exercise control group (E), weight loss diet (D), or D + E. C1M, C2M, C3M and CRPM biomarkers and interleukin-6 (IL-6) were quantitated using ELISAs. Radiographic progression was defined as a decrease in joint space width of ≥0.7 mm. Statistical modeling of group means and associations used mixed models adjusted for visit, baseline body mass index (BMI), gender, and baseline values of the outcome.

RESULTS

Compared to the E control group, C1M was significantly lower in the D and D + E groups at both 6 and 18 months while C3M was significantly lower in D and D + E at 6 months and in D + E at 18 months. C2M did not change in any group. Using data from all groups, change in C1M (P < 0.0001), C3M (P < 0.0001), as well as CRPM (P = 0.0004) from baseline to 18 months was positively associated with change in weight. No marker was associated with change in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain or radiographic progression. C3M (P = 0.008) and CRPM (P = 0.028) were positively associated with change in WOMAC function. Change in IL-6 was positively associated with change in C1M, C3M, and CRPM.

CONCLUSION

Overweight and obese adults with knee OA who lost weight from diet and diet plus exercise reduced serum markers of interstitial matrix turnover and inflammation but not type II collagen degradation.

The Role of Sirtuins in Cartilage Homeostasis and Osteoarthritis

The past decade has witnessed many advances in the understanding of sirtuin biology and related regulatory circuits supporting the capacity of these proteins to serve as energy-sensing molecules that contribute to healthspan in various tissues, including articular cartilage. Hence, there has been a significant increase in new investigations that aim to elucidate the mechanisms of sirtuin function and their roles in cartilage biology, skeletal development, and pathologies such as osteoarthritis (OA), rheumatoid arthritis (RA), and intervertebral disc degeneration (IVD). The majority of the work carried out to date has focused on SIRT1, although SIRT6 has more recently become a focus of some investigations. In vivo work with transgenic mice has shown that Sirt1 and Sirt6 are essential for maintaining cartilage homeostasis and that the use of sirtuin-activating molecules such as resveratrol may have beneficial effects on cartilage anabolism. Current thinking is that SIRT1 exerts positive effects on cartilage by encouraging chondrocyte survival, especially under stress conditions, which may provide a mechanism supporting the use of sirtuin small-molecule activators (STACS) for future therapeutic interventions in OA and other degenerative pathologies of joints, especially those that involve articular cartilage.

The Multifunctional Role of the Chemokine System in Arthritogenic Processes

PURPOSE OF REVIEW

The involvement of chemokines and their receptors in the genesis and perpetuation of rheumatoid arthritis, spondyloarthritis, and osteoarthritis has been clearly recognized for a long time. Nevertheless, the complexity of their contribution to these diseases is now becoming evident and this review focuses on published evidence on their mechanism of action.

RECENT FINDINGS

Studies performed on patients and in vivo models have identified a number of chemokine-mediated pathways involved in various aspects of arthritogenic processes. Chemokines promote leukocyte infiltration and activation, angiogenesis, osteoclast differentiation, and synoviocyte proliferation and activation and participate to the generation of pain by regulating the release of neurotransmitters. A number of chemokines are expressed in a timely controlled fashion in the joint during arthropathies, regulating all the aspects of inflammation as well as the equilibrium between damage and repair and between relief and pain. Thus, the targeting of specific chemokine/chemokine receptor interactions is considered a promising tool for therapeutic intervention.

Senescent cells: an emerging target for diseases of ageing

Chronological age represents the single greatest risk factor for human disease. One plausible explanation for this correlation is that mechanisms that drive ageing might also promote age-related diseases. Cellular senescence, which is a permanent state of cell cycle arrest induced by cellular stress, has recently emerged as a fundamental ageing mechanism that also contributes to diseases of late life, including cancer, atherosclerosis and osteoarthritis. Therapeutic strategies that safely interfere with the detrimental effects of cellular senescence, such as the selective elimination of senescent cells (SNCs) or the disruption of the SNC secretome, are gaining significant attention, with several programmes now nearing human clinical studies.

Preoperative ultraviolet B inflammation in skin: Modelling individual differences in acute postoperative pain and neuro-immune interactions

BACKGROUND

Neuroimmune interactions play a vital role in many of the most common pain conditions, such as arthritis. There have been many attempts to derive clinically predictive information from an individual's inflammatory response in order to gauge subsequent pain perception.

OBJECTIVES

Here, we wanted to test whether this effort could be enhanced and complemented by the use of a model system which takes into account the function of not just circulating, but also tissue-resident immune cells: ultraviolet B (UVB) irradiation of the skin.

METHODS

We conducted psychophysical and transcriptional analysis of hyperalgesia arising as a result of UVB-induced inflammation in patients before total knee arthroplasty (TKA, n = 23). Levels of acute postoperative pain were assessed and correlated with preoperative data.

RESULTS

Cytokine and chemokine responses after UVB irradiation were found to be inversely correlated with the level of pain experienced after surgery (Spearman's ρ = -0.498).

CONCLUSION

It may be possible to use this simple model to study and predict the nature of neuro-immune responses at more remote, clinically relevant sites.

SIGNIFICANCE

A simple model of UVB inflammation in the skin might predict the degree of a patient's neuro-immune response and the extent of their postoperative pain after total knee arthroplasty.

Quantification of cartilage oligomeric matrix protein (COMP) and a COMP neoepitope in synovial fluid of patients with different joint disorders by novel automated assays

OBJECTIVE

To develop automated immunoassays for the quantification of Cartilage Oligomeric Matrix Protein (COMP) and a COMP neoepitope in synovial fluid and to investigate their diagnostic potential in different joint conditions.

METHODS

Two sandwich immunoassays were developed for the quantification of COMP and a COMP neoepitope, using an automated analyser (IDS-iSYS, Immunodiagnostic Systems, Boldon, UK). Assay performance was evaluated in terms of sensitivity, recovery, linearity, and intra- and inter-assay precision. Clinical performance was evaluated by analysing synovial fluid from patients diagnosed with rheumatoid arthritis (RA), reactive arthritis (ReA), osteoarthritis (OA) or acute trauma (AT).

RESULTS

Both automated assays showed good performance for all parameters tested. Quantification of these biomarkers showed the highest median values for Total COMP in the OA group, followed by the AT group, the ReA group, and the RA group. For the COMP neoepitope the AT group showed the highest median value, followed by the ReA group, the OA group, and the RA group. The ratio COMP neoepitope/Total COMP showed distinct differences between the patients groups, as well as between RA patients with slow or rapid progression of joint damage.

CONCLUSIONS

The newly developed automated assays have a good technical performance, can reliably quantify different epitopes on the COMP molecule and show different levels of the two biomarkers in synovial fluid in patients with different joint diseases. The combination of these two assays, measuring their ratio, shows promise for early detection of patients with RA with different prognosis regarding progression of joint damage.

Systems approaches in osteoarthritis: Identifying routes to novel diagnostic and therapeutic strategies

Systems orientated research offers the possibility of identifying novel therapeutic targets and relevant diagnostic markers for complex diseases such as osteoarthritis. This review demonstrates that the osteoarthritis research community has been slow to incorporate systems orientated approaches into research studies, although a number of key studies reveal novel insights into the regulatory mechanisms that contribute both to joint tissue homeostasis and its dysfunction. The review introduces both top-down and bottom-up approaches employed in the study of osteoarthritis. A holistic and multiscale approach, where clinical measurements may predict dysregulation and progression of joint degeneration, should be a key objective in future research. The review concludes with suggestions for further research and emerging trends not least of which is the coupled development of diagnostic tests and therapeutics as part of a concerted effort by the osteoarthritis research community to meet clinical needs. © 2017 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1573-1588, 2017.

Levels of serum biomarkers from a two-year multicentre trial are associated with treatment response on knee osteoarthritis cartilage loss as assessed by magnetic resonance imaging: an exploratory study

Background

There is an obvious need to identify biomarkers that could predict patient response to an osteoarthritis (OA) treatment. This post hoc study explored in a 2-year randomized controlled trial in patients with knee OA, the likelihood of some serum biomarkers to be associated with a better response to chondroitin sulfate in reducing cartilage volume loss.

Methods

Eight biomarkers were studied: hyaluronic acid (HA), C reactive protein (CRP), adipsin, leptin, N-terminal propeptide of collagen IIα (PIIANP), C-terminal crosslinked telopeptide of type I collagen (CTX-1), matrix metalloproteinase-1 (MMP-1), and MMP-3. Patients were treated with chondroitin sulfate (1200 mg/day; n = 57) or celecoxib (200 mg/day; n = 62). Serum biomarkers were measured at baseline. The cartilage volume at baseline and its loss at 2 years were assessed by quantitative magnetic resonance imaging (MRI). Statistical analysis included analysis of covariance.

Results

As data from the original MOSAIC trial showed no differences in cartilage volume and loss in the lateral compartment of the knee joint between the two treatment groups in any comparison, only the medial compartment and its subregions were studied. Stratification according to the median biomarker levels was used to discriminate treatment effect. In patients with levels of biomarkers of inflammation (HA, leptin and adipsin) lower than the median, those treated with chondroitin sulfate demonstrated less cartilage volume loss in the medial compartment, condyle, and plateau (p ≤ 0.047). In contrast, patients treated with chondroitin sulfate with higher levels of MMP-1 and MMP-3, biomarkers of cartilage catabolism, had less cartilage volume loss in the medial compartment, condyle, and plateau (p ≤ 0.050). Patients with higher levels of PIIANP and CTX-1, biomarkers related to collagen anabolism and bone catabolism, respectively, had reduced cartilage volume loss in the medial condyle (p ≤ 0.026) in the chondroitin sulfate group.

Conclusion

This study is suggestive of a potentially greater response to chondroitin sulfate treatment on cartilage volume loss in patients with knee OA with low level of inflammation and/or greater level of cartilage catabolism.

Trial registration

This is a post hoc study. Original trial registration: ClinicalTrials.gov, NCT01354145. Registered on 13 May 2011. 

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1377-y) contains supplementary material, which is available to authorized users.