Serum and urinary biochemical markers for knee and hip-osteoarthritis: a systematic review applying the consensus BIPED criteria

Blood and urine biomarkers for the diagnosis of early stages of knee osteoarthritis: A systematic review

Purpose

To identify biomarkers in human blood or urine at an early stage of knee osteoarthritis (OA) and to elucidate if any can accurately differentiate between healthy controls and early knee OA patients and be considered as a candidate for widespread clinical use for early diagnosis of the disease.

Methods

Medline, Embase and Web of Science were screened to identify comparative studies measuring differences in blood or urine biomarkers between healthy controls and knee OA patients at an early stage (grade 1 or 2 Kellgren-Laurence). Two independent reviewers screened the abstracts for eligibility, reviewed the full texts, assessed the methodological quality and extracted the data. The Joanna Briggs Institute critical appraisal tool for diagnostic test accuracy studies was used to assess the quality of the included studies. Due to relevant heterogeneity, meta-analysis was not appropriate.

Results

Five studies met the eligibility criteria. The examined biomarkers were adropin, collagen type II metabolite, C-terminal cross-linked telopeptide of type II collagen, C-terminal cross-linked telopeptide of type I collagen, cartilage oligomeric matrix protein, matrix metalloproteinase 3, N-terminal propeptide of procollagen type IIA, type I procollagen N-terminal propeptides, N-terminal osteocalcin, angiopoietin-2, follistatin, granulocyte colony-stimulating factor, hepatocyte growth factor, interleukin-8, leptin, platelet-derived growth factor-BB, platelet endothelial cell adhesion molecule-1, vascular endothelial growth factor and calprotectin and totalling 19 biomarkers. All of the biomarkers were studied only once in the selected papers.

Conclusions

There is no reliable biomarker available to differentiate between early knee OA in patients and healthy controls, but a potential role of a cluster of biomarkers to close this gap. There are several limitations, including inappropriate study designs, small sample sizes, nonconsecutive patient groups and inadequate statistical methods for evaluating biomarker performance in studies included.

Level of Evidence

Level III.

Endophenotypes of Primary Osteoarthritis of the Hip Joint in the Bulgarian Population over 60 Years Old

Aim. To identify subgroups of patients with primary osteoarthritis of the hip joint (pHOA) with similar imaging and laboratory findings, disease evolution, and response to conventional therapies. Methods. We performed further statistical analyses on patient data from two published, double-blind, randomized, and placebo-controlled studies (DB-RCTs), which examined the effects of intra-articular corticosteroids (ia-CSs), hyaluronic acid (ia-HA)-KИ-109-3-0008/14.01.2014, and intravenous bisphosphonates (iv-BPs) -KИ- 109-3-0009/14.01.2014 compared to the country's standard pHOA therapy. The data span an 8-year follow-up of 700 patients with pHOA, including: 1. Clinical parameters (WOMAC-A, B, C, and T; PtGA). 2. Laboratory markers (serum calcium and phosphate levels; 25-OH-D and PTH, markers for bone sCTX-I and cartilage uCTX-II turnover). 3. Radiological indicators: X-ray stage (Kellgren-Lawrence (K/L) and model (Bombelli/OOARSI), width (mJSW), speed (JSN mm/year), and zone of maximum narrowing of the joint space (max-JSN)-determining the type of femoral head migration (FHM). 4. DXA indicators: bone geometry (HAL; NSA; and MNW); changes in regional and total bone mineral density (TH-BMD, LS-BMD, and TB-BMD). 5. Therapeutic responses (OARSI/MCII; mJSW; JSNmm/yearly) to different drug regimens (iv-BP -zoledronic acid (ZA/-5 mg/yearly for 3 years)); ia-CS 40 mg methylprednisolone acetate, twice every 6 months; and ia-HA with intermediate molecular weight (20 mg/2 mL × 3 weekly applications, two courses every 6 months) were compared to standard of care therapy (Standard of Care/SC/), namely D3-supplementation according to serum levels (20-120 ng/mL; target level of 60 ng/mL), simple analgesics (paracetamol, up to 2.0 g/24 h), and physical exercises. The abovementioned data were integrated into a non-supervised hierarchical agglomerative clustering analysis (NHACA) using Ward's linkage method and the squared Euclidean distance to identify different endophenotypes (EFs). Univariate and multivariate multinomial logistic regression analyses were performed to determine the impact of sex and FHM on clinical and radiographic regression of pHOA. Results. A baseline cluster analysis using incoming (M0) patient data identified three EFs: hypertrophic H-HOA, atrophic A-HOA, and intermediate I-HOA. These EFs had characteristics that were similar to those of patients grouped by radiographic stage and pattern ('H'-RPs, 'I'-RPs, and 'A'-RPs), p < 0.05). The repeated cluster analysis of M36 data identified four EF pHOAs: 1. Hypertrophic (slow progressors, the influence of the type of femoral head migration (FHM) outweighing the influence of sex on progression), progressing to planned total hip replacement (THR) within 5 (K/LIII) to 10 (K/LII) years. 2. Intermediate (sex is more important than the FHM type for progression) with two subgroups: 2#: male-associated (slow progressors), THR within 4 (K/LIII) to 8 years. (K/LII). 2* Female-associated (rapid progressors), THR within 3 (K/LIII) to 5 (K/LII) years. 3. Atrophic (rapid progressors; the influence of FHM type outweighs that of sex), THR within 2 (K/LIII) to 4 (K/LII) years. Each EF, in addition to the patient's individual progression rate, was also associated with a different response to the aforementioned therapies. Conclusions. Clinical endophenotyping provides guidance for a personalized approach in patients with pHOA, simultaneously assisting the creation of homogeneous patient groups necessary for conducting modern genetic and therapeutic scientific studies.

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.

Role of Serum Micro-RNA-122-5p Expression as a Circulatory Biomarker in People Having Both Knee Osteoarthritis and Osteoporosis: A Case-Control Study

Background Although knee osteoarthritis (KOA) and osteoporosis (OP) manifest distinct pathophysiologies, they share numerous similarities. These health conditions are commonly found in older individuals, particularly among women. The objective of this study is to explore the expression of micro-RNA (miRNA) 122-5p (miR-122-5p) in people affected by both KOA and OP. The main aim is to identify diagnostic biomarkers and potential therapeutic targets, which could help develop personalized treatment approaches. Methods As part of the study, a total of 268 serum samples were collected from the participants, who were divided into four groups: KOA, OP, KOA and OP, and controls, with 67 subjects per group. The miRNA species-containing total RNA was isolated from the serum samples using an miRNeasy serum/plasma kit by QIAGEN (Hilden, Germany). The expression of miR-122-5p was examined in each group using real-time quantitative polymerase chain reaction. Results Expression of miR-122-5p in all three groups (KOA, OP, and common group of KOA and OP) was significantly upregulated, and the fold change value was much higher in the group having both diseases. Conclusions These results might contribute to the identification of cases at risk, early diagnosis, and development, and might also contribute to the development of therapeutic targets in subjects having both KOA and OP.

An osteoarthritis pathophysiological continuum revealed by molecular biomarkers

We aimed to identify serum biomarkers that predict knee osteoarthritis (OA) before the appearance of radiographic abnormalities in a cohort of 200 women. As few as six serum peptides, corresponding to six proteins, reached AUC 77% probability to distinguish those who developed OA from age-matched individuals who did not develop OA up to 8 years later. Prediction based on these blood biomarkers was superior to traditional prediction based on age and BMI (AUC 51%) or knee pain (AUC 57%). These results identify a prolonged molecular derangement of joint tissue before the onset of radiographic OA abnormalities consistent with an unresolved acute phase response. Among all 24 protein biomarkers predicting incident knee OA, the majority (58%) also predicted knee OA progression, revealing the existence of a pathophysiological "OA continuum" based on considerable similarity in the molecular pathophysiology of the progression to incident OA and the progression of established OA.

Serum proteomic biomarkers diagnostic of knee osteoarthritis

OBJECTIVE

To better understand the pathogenesis of knee osteoarthritis (OA) through identification of serum diagnostics.

DESIGN

We conducted multiple reaction monitoring mass spectrometry analysis of 107 peptides in baseline sera of two cohorts: the Foundation for National Institutes of Health (NIH) (n = 596 Kellgren-Lawrence (KL) grade 1-3 knee OA participants); and the Johnston County Osteoarthritis Project (n = 127 multi-joint controls free of radiographic OA of the hands, hips, knees (bilateral KL=0), and spine). Data were split into (70%) training and (30%) testing sets. Diagnostic peptide and clinical data predictors were selected by random forest (RF); selection was based on association (p < 0.05) with OA status in multivariable logistic regression models. Model performance was based on area under the curve (AUC) of receiver operating characteristic (ROC) and precision-recall (PR) curves.

RESULTS

RF selected 23 peptides (19 proteins) and body mass index (BMI) as diagnostic of OA. BMI weakly diagnosed OA (ROC-AUC 0.57, PR-AUC 0.812) and only symptomatic OA cases. ACTG was the strongest univariable predictor (ROC-AUC 0.705, PR-AUC 0.897). The final model (8 serum peptides) was highly diagnostic (ROC-AUC 0.833, 95% confidence interval [CI] 0.751, 0.905; PR-AUC 0.929, 95% CI 0.876, 0.973) in the testing set and equally diagnostic of non-symptomatic and symptomatic cases (AUCs 0.830-0.835), and not significantly improved with addition of BMI. The STRING database predicted multiple high confidence interactions of the 19 diagnostic OA proteins.

CONCLUSIONS

No more than 8 serum protein biomarkers were required to discriminate knee OA from non-OA. These biomarkers lend strong support to the involvement and cross-talk of complement and coagulation pathways in the development of OA.

Intra-articular injection of platelet lysate-derived extracellular vesicles recovers from knee osteoarthritis in an in vivo rat model

Objective

MSCs and Platelet-Rich Plasma are the main focus in the study of new regenerative treatments aimed to reverse Osteoarthritis (OA). However, extracellular vesicles (EVs) present several advantages to cell-based treatments. Thus, the aim of this study was to compare and evaluate the regenerative potential of MSC-derived EVs (cEVs) and platelet-derived EVs (pEVs) in an OA cartilage rat model.

Design

OA in vivo model was established through injection of 6 mg MIA in the rat knee joints. After 14 and 21 days, OA knee joints were treated with 1 × 1010 particles of pEVs or cEVs. At day 28, the animals were sacrificed, plasma was collected to quantify CTX-II and knee joints were excised to be evaluated by Cone Beam Computed Tomography (CBCT). After decalcification, histology was used to determine the OARSI score and to visualize collagen and glycosaminoglycan content.

Results

pEVs and cEVs samples did not show significant differences per se but they did in terms of regenerative effects on OA knee joints. pEVs-treated knee joints showed better subchondral bone integrity in CT-analysed parameters when compared to cEVs or OA group, showing similar values to the healthy control group. Moreover, OARSI score indicated that pEVs showed a greater OA reversion in knee joints, especially in female rats, and so indicated the analysed histological images.

Conclusions

pEVs are proposed as a viable regeneration treatment for OA since they are not only capable of exerting their regenerative potential on osteoarthritic cartilage, but also outperform cEVs in terms of efficacy, particularly in females.

Significance statement

Osteoarthritis (OA) is one of the most age-related diseases. It is estimated that 500 million people suffer from OA worldwide, representing the principal cause of chronic disability in adults. In the present study we evaluated the therapeutic effect of extracellular vesicles (EVs) from different sources (platelet lysate and human umbilical cord mesenchymal stromal cells) in an in vivo rat model. Our results demonstrate that platelet-derived EVs (pEVs) induce an OA reversion in knee joints, thus evidencing the therapeutic potential of pEVs as cell-free regenerative agents for OA treatment.

The translational potential of this article

Platelet-derived extracellular vesicles (pEVs) offer a promising cell-free therapy option for OA treatment. Their production could be easily standardized and reproduced without extensive platelet harvesting and amplification, thus paving the way for their clinical translation.

Association of biochemical markers with bone marrow lesion changes on imaging-data from the Foundation for the National Institutes of Health Osteoarthritis Biomarkers Consortium

BACKGROUND

To assess the prognostic value of short-term change in biochemical markers as it relates to bone marrow lesions (BMLs) on MRI in knee osteoarthritis (OA) over 24 months and, furthermore, to assess the relationship between biochemical markers involved with tissue turnover and inflammation and BMLs on MRI.

METHODS

Data from the Foundation for the National Institutes of Health OA Biomarkers Consortium within the Osteoarthritis Initiative (n = 600) was analyzed. BMLs were measured according to the MRI Osteoarthritis Knee Score (MOAKS) system (0-3), in 15 knee subregions. Serum and urinary biochemical markers assessed were as follows: serum C-terminal crosslinked telopeptide of type I collagen (CTX-I), serum crosslinked N-telopeptide of type I collagen (NTX-I), urinary CTX-Iα and CTX-Iβ, urinary NTX-I, urinary C-terminal cross-linked telopeptide of type II collagen (CTX-II), serum matrix metalloproteinase (MMP)-degraded type I, II, and III collagen (C1M, C2M, C3M), serum high sensitivity propeptide of type IIb collagen (hsPRO-C2), and matrix metalloproteinase-generated neoepitope of C-reactive protein (CRPM). The association between change in biochemical markers over 12 months and BMLs over 24 months was examined using regression models adjusted for covariates. The relationship between C1M, C2M, C3M, hsPRO-C2, and CRPM and BMLs at baseline and over 24 months was examined.

RESULTS

Increases in serum CTX-I and urinary CTX-Iβ over 12 months were associated with increased odds of changes in the number of subregions affected by any BML at 24 months. Increase in hsPRO-C2 was associated with decreased odds of worsening in the number of subregions affected by any BML over 24 months. C1M and C3M were associated with BMLs affected at baseline.

CONCLUSIONS

Short-term changes in serum CTX-I, hsPRO-C2, and urinary CTX-Iβ hold the potential to be prognostic of BML progression on MRI. The association of C1M and C3M with baseline BMLs on MRI warrants further investigation.

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.

Associations between biomarkers of matrix metabolism and inflammation with pain and fatigue in participants suspected of early hip and or knee osteoarthritis: data from the CHECK study

OBJECTIVES

To assess the associations of biomarkers in serum [highsensitivity C-reactive protein (hs-CRP), serum cartilage oligomeric protein (sCOMP), serum propeptide of type I procollagen (sPINP) and serum osteocalcin (sOC)] and urine [urinary type II collagen telopeptide (uCTX-2)] with the extent and progression of nocturnal pain, pain while walking, and fatigue in participants with hip and/or knee pain suspected to be early stage osteoarthritis (OA).

METHODS

hs-CRP, uCTX-2, sCOMP, sPINP and sOC were measured at baseline in 1,002 participants of the Cohort Hip and Cohort Knee (CHECK). Nocturnal pain, pain while walking and fatigue were assessed by self-reported questionnaires at baseline and 2-year follow-up. Associations between these biomarkers and symptoms were examined using logistic and linear regression analyses.

RESULTS

hs-CRP was significantly associated with mild nocturnal pain (OR 1.18 95% CI 1.01-1.37), with mild and moderate pain while walking (OR 1.17 95% CI 1.01-1.35 and OR 1.56 95% CI 1.29-1.90, respectively) and with progression of nocturnal pain (OR 1.25 95% CI 1.07-1.46). uCTX-2 was associated with mild nocturnal pain (OR 1.40 95% CI 1.05-1.85) and with mild and severe-extreme pain while walking (OR 1.35 95% CI 1.04-1.75 and OR 2.55 95% CI 1.03-6.34, respectively). sPINP was associated with severe-extreme nocturnal pain (OR 0.45 95% CI 0.25-0.82). No significant associations were found for sCOMP and sOC, nor for any of the biomarkers and fatigue.

CONCLUSION

This study of biomarkers in a large cohort of participants with hip and/or knee pain suspected to reflect early stage hip and/or knee OA suggests that inflammation and cartilage matrix degeneration play a role in pain, but not in fatigue.

Identification of susceptibility modules and hub genes of osteoarthritis by WGCNA analysis

Osteoarthritis (OA) is a major cause of pain, disability, and social burden in the elderly throughout the world. Although many studies focused on the molecular mechanism of OA, its etiology remains unclear. Therefore, more biomarkers need to be explored to help early diagnosis, clinical outcome measurement, and new therapeutic target development. Our study aimed to retrieve the potential hub genes of osteoarthritis (OA) by weighted gene co-expression network analysis (WGCNA) and assess their clinical utility for predicting OA. Here, we integrated WGCNA to identify novel OA susceptibility modules and hub genes. In this study, we first selected 477 and 834 DEGs in the GSE1919 and the GSE55235 databases, respectively, from the Gene Expression Omnibus (GEO) website. Genes with p-value&lt;0.05 and | log2FC | &gt; 1 were included in our analysis. Then, WGCNA was conducted to build a gene co-expression network, which filtered out the most relevant modules and screened out 23 overlapping WGCNA-derived hub genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses elucidated that these hub genes were associated with cell adhesion molecules pathway, leukocyte activation, and inflammatory response. In addition, we conducted the protein–protein interaction (PPI) network in 23 hub genes, and the top four upregulated hub genes were sorted out (CD4, SELL, ITGB2, and CD52). Moreover, our nomogram model showed good performance in predicting the risk of OA (C-index = 0.76), and this model proved to be efficient in diagnosis by ROC curves (AUC = 0.789). After that, a single-sample gene set enrichment (ssGSEA) analysis was performed to discover immune cell infiltration in OA. Finally, human primary synoviocytes and immunohistochemistry study of synovial tissues confirmed that those candidate genes were significantly upregulated in the OA groups compared with normal groups. We successfully constructed a co-expression network based on WGCNA and found out that OA-associated susceptibility modules and hub genes, which may provide further insight into the development of pre-symptomatic diagnosis, may contribute to understanding the molecular mechanism study of OA risk genes.

Boswellia serrata Extract, 5-Loxin®, Prevents Joint Pain and Cartilage Degeneration in a Rat Model of Osteoarthritis through Inhibition of Inflammatory Responses and Restoration of Matrix Homeostasis

Osteoarthritis (OA) is a chronic, progressive joint disease associated with pain, functional impairment, and diminished quality of life in affected individuals. At a societal level, it also has a high economic burden. Boswellia serrata has been reported to have potent anti-inflammatory, antiarthritic, and analgesic effects. The aim of this study was to explore the therapeutic potential and possible underlying mechanism of 5-Loxin®, a standardized Boswellia serrata extract, in a rat model of OA. The OA model was established by the intra-articular injection of 50 μL of monosodium iodoacetate (MIA) (60 mg/mL). 5-Loxin® was administered orally, and efficacy was evaluated through serum analysis, real-time polymerase chain reaction (PCR), histologic staining, and micro-computed tomography (micro-CT). Results indicated that administration of 5-Loxin® can relieve OA joint pain through inhibition of both inflammatory processes and cartilage degeneration. In the group of rats treated with 5-Loxin®, the suppression of inflammatory enzymes such as cyclooxygenase (COX)-2 and 5-lipoxygenase (LOX) resulted in a significant reduction in the prostaglandin (PG) E₂ and leukotriene (LT) B₄ levels. Moreover, 5-Loxin® ameliorated the deterioration of the main components of the articular extracellular matrix (ECM), such as glycosaminoglycans (GAGs) and aggrecan, through the downregulation of matrix metalloproteinases (MMPs). These findings suggest that 5-Loxin® may be a potential therapeutic agent for the treatment of OA.

Cartilage Acidic Protein 1 in Plasma Associates With Prevalent Osteoarthritis and Predicts Future Risk as Well as Progression to Joint Replacements: Results From the UK Biobank Resource

OBJECTIVE

The level of cartilage acidic protein 1 (CRTAC1) in plasma was recently discovered to be associated with osteoarthritis (OA) risk and progression to joint replacement in Iceland. This study was undertaken to validate these findings in an independent population.

METHODS

In this study, 1,462 plasma proteins were measured in 54,265 participants from the UK Biobank on the Olink Explore platform. We analyzed the association of plasma proteins with prevalent OA, incident OA, and progression to joint replacement. We assessed the specificity of OA association through comparison of associations with inflammatory joint diseases and with previous joint replacement.

RESULTS

The CRTAC1 protein showed the strongest association with prevalent knee OA (odds ratio [OR] 1.34 [95% confidence interval (95% CI) 1.27, 1.41]) and was associated with hip OA (OR 1.19 [95% CI 1.11, 1.28]). It predicted incident diagnosis of OA in the knee (hazard ratio [HR] 1.40 [95% CI 1.35, 1.46]) and hip (HR 1.25 [95% CI 1.19, 1.31]), as well as progression to joint replacement (HR 1.20 [95% CI 1.08, 1.33] for the knee and HR 1.22 [95% CI 1.08, 1.38] for the hip), while no association was found with inflammatory joint diseases. Individuals in the highest quintile of risk based on CRTAC1 level, age, sex, and body mass index had a 10-fold risk of knee or hip OA within 5 years compared to those in the lowest quintile. Adding aggrecan core protein (ACAN) and neurocan core protein (NCAN) to the model improved the prediction of OA but not joint replacement. Furthermore, we replicated the association of CUB domain-containing protein 1 with prior joint replacement.

CONCLUSION

Plasma CRTAC1 is a specific biomarker for OA and a predictor of OA risk and progression to joint replacement. Adding ACAN and NCAN protein levels to the CRTAC1 model improved the prediction of OA.

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.

Towards Precision Medicine for Osteoarthritis: Focus on the Synovial Fluid Proteome

Osteoarthritis (OA) is a joint degenerative disease that most affects old age. The study of proteomics in synovial fluid (SF) has the task of providing additional elements to diagnose and predict the progress of OA. This review aims to identify the most significant biomarkers in the study of OA and to stimulate their routine use. Some of the major components of the ECM, such as proteoglycan aggrecan and decorin, were found considerably reduced in OA. Some biomarkers have proved useful for staging the temporality of OA: Periostin was found to be increased in early OA, while CRTA1 and MMPs were found to be increased in late OA. In its natural attempt at tissue regeneration, Collagen III was found to be increased in early OA while decreased in late OA. Some molecules studied in other areas, such as ZHX3 (oncological marker), LYVE1, and VEGF (lymph and angiogenesis markers), also have been found to be altered in OA. It also has been recorded that alteration of the hormonal pathway, using a dosage of PPAR-γ and RETN, can influence the evolution of OA. IL-1, one of the most investigated biomarkers in OA-SF, is not as reliable as a target of OA in recent studies. The study of biomarkers in SF appears to be, in combination with the clinical and radiological aspects, an additional weapon to address the diagnosis and staging of OA. Therefore, it can guide us more appropriately towards the indication of arthroplasty in patients with OA.

Dose-response relationship of in vivo ambulatory load and mechanosensitive cartilage biomarkers—The role of age, tissue health and inflammation: A study protocol

Objective

To describe a study protocol for investigating the in vivo dose-response relationship between ambulatory load magnitude and mechanosensitive blood markers of articular cartilage, the influence of age, cartilage tissue health and presence of inflammation on this relationship, and its ability to predict changes in articular cartilage quality and morphology within 2 years.

Design

Prospective experimental multimodal (clinical, biomechanical, biological) data collection under walking stress and three different load conditions varied in a randomized crossover design.

Experimental protocol

At baseline, equal numbers of healthy and anterior cruciate ligament injured participants aged 20–30 or 40–60 years will be assessed clinically and complete questionnaires regarding their knee health. Biomechanical parameters (joint kinetics, joint kinematics, and surface electromyography) will be recorded while performing different tasks including overground and treadmill walking, single leg balance and hopping tasks. Magnetic resonance images (MRI) of both of knees will be obtained. On separate stress test days, participants will perform a 30-minute walking stress with either reduced (80% body weight (BW)), normal (100%BW) or increased (120%BW) load. Serum blood samples will be taken immediately before, immediately after, 30, 120 and 210 minutes after the walking stress. Concentration of articular cartilage blood biomarkers will be assessed using enzyme linked immunosorbent assays. At 24-month follow-up, participants will be again assessed clinically, undergo an MRI, complete questionnaires, and have a blood sample taken.

Conclusion

The study design provides a standardized set up that allows to better understand the influence of ambulatory load on articular cartilage biomarkers and thereby extend current knowledge on in vivo cartilage metabolism and mechanosensitivity. Further, this study will help to elucidate the prognostic value of the load-induced cartilage biomarker response for early articular cartilage degeneration.

Trial registration

The protocol was approved by the regional ethics committee and has been registered at clinicaltrials.gov (NCT04128566).

Effect of Pulsed Low-Intensity Ultrasonography on Symptom Relief and Tibiofemoral Articular Cartilage Thickness Among Veterans Affairs Enrollees With Knee Osteoarthritis: A Randomized Clinical Trial

IMPORTANCE

Osteoarthritis (OA) is a major cause of disability in the US, with no approved treatments to slow progression, but animal models suggest that pulsed low-intensity ultrasonography (PLIUS) may promote cartilage growth.

OBJECTIVE

To evaluate the efficacy of PLIUS in providing symptom reduction and decreased loss of tibiofemoral cartilage thickness in patients with knee OA.

DESIGN, SETTING, AND PARTICIPANTS

A phase 2A, sham-controlled, parallel, double-blind randomized clinical trial was conducted at 2 Veterans Affairs hospitals in Salt Lake City, Utah, and San Diego, California, from May 22, 2015, to January 31, 2019. Data were analyzed from June 27, 2020, to October 20, 2020. Participants recruited through the US Department of Veterans Affairs (N = 132) with clinical and radiographic evidence of early knee OA were randomly assigned to receive PLIUS or a sham device, self-administered for 20 minutes daily over the medial compartment of the knee. All enrollees participated in a 4-week prerandomization sham run-in period, followed by a 48-week treatment period. Randomization was stratified by study site and Kellgren-Lawrence grades 1 (n = 15), 2 (n = 51), and 3 (n = 66).

INTERVENTION

Participants either received 48 weeks of PLIUS or sham ultrasonography.

MAIN OUTCOMES AND MEASURES

The trial incorporated 2 coprimary outcomes: symptomatic improvement assessed by Outcome Measures in Rheumatology Clinical Trials-Osteoarthritis Research Society International Responder Criteria (ie, met if either >50% improvement in pain and function with at least a 20% absolute improvement of at least 2 of the following 3 factors: improvement by at least 20% [pain, function, and patient global assessment] with at least a 10-mm absolute improvement), and cartilage preservation assessed as change in central medial femoral condyle cartilage thickness by magnetic resonance imaging. Intention-to-treat analysis was used.

RESULTS

The mean (SD) participant age was 63.6 (10.7) years and 119 were men (90.2%). The mean (SD) duration of OA symptoms was 13.4 (12.3) years. In the PLIUS group, 70.4% (95% CI, 58.2%-82.6%) of the participants experienced symptomatic improvement, compared with 67.3% (95% CI, 54.9%-79.7%) of participants in the sham group (P = .84); there was no statistically significant difference in response rates between the treatment groups, and the between-group rate difference of 3.1% (95% CI, -14.3% to 20.5%) did not meet the predefined 10% threshold for clinically significant symptomatic improvement from application of PLIUS. At 48 weeks of treatment, central medial femoral condyle cartilage thickness decreased by a mean (SD) of 73.8 (168.1) μm in the PLIUS group and by 42.2 (297.0) μm in the sham group. This 48-week mean change between the 2 groups did not reach statistical significance (P = .44), and the between-group 48-week difference of -31.7 μm (95% CI, -129.0 μm to 65.7 μm) did not meet the predefined threshold. There were 99 nonserious adverse events in the PLIUS group and 89 in the sham group during the trial. No serious adverse events were deemed related to the study device.

CONCLUSIONS AND RELEVANCE

PLIUS, as implemented in this study, demonstrated neither symptomatic benefit nor a decrease in loss of tibiofemoral cartilage thickness in knee OA.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02034409.

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.

Early Detection of Cartilage Degradation Among Heavy Manual Workers Using Serum Level of Collagen Type II Metabolite

BACKGROUND

Work-related musculoskeletal disorders are common health problems in brick manufacturers, where mechanical load leads to degenerative joint diseases. Collagen type II metabolite (C2C) is a small peptide excreted in urine, and its serum concentration can directly reflect articular cartilage decomposition.

OBJECTIVE

Early detection of musculoskeletal disorders among brick workers, using serum C2C as a biomarker of cartilage damage.

METHODS

This study involved 88 male brick workers in Arab Abu Saed matched to 88 age- and sex-matched controls. Full history taking, pain assessment using the Standardized Nordic Questionnaire, and complete clinical examination were done for both groups. Serum C2C was measured using a competitive immunoassay method.

RESULTS

Brick workers involved in the study were of a mean age 30.66 ± 7.90 years and mean work duration 14.80 ± 7.89 years, matched to 88 controls. The majority of the participants (77.3%) were of normal body mass index. An increase in pain/discomfort was found among the exposed group. Serum C2C had an increased mean among the exposed group compared with the control. Pearson correlation between serum C2C level, body mass index, age, and years of employment showed no correlation.

CONCLUSIONS

Musculoskeletal disorders are prevalent among brick workers who adopt specific awkward postures, unhealthy working conditions, and nonexistent safety procedures, for prolonged periods. Detection of serum C2C level can be used as a predictive biomarker for the early detection of musculoskeletal disorders among brick workers.

Joint distraction for osteoarthritis: clinical evidence and molecular mechanisms

Joint distraction, the prolonged mechanical separation of the bones at a joint, has emerged as a joint-preserving treatment for end-stage osteoarthritis, with the gradually growing promise of implementation in regular clinical practice. Joint distraction of the knee has been most extensively studied, with these studies showing prolonged symptomatic improvement in combination with repair of cartilage tissue in degenerated knee joints, supporting the concept that cartilage repair can translate into real clinical benefit. The reversal of tissue degeneration observed with joint distraction could be the result of one or a combination of various proposed mechanisms, including partial unloading, synovial fluid pressure oscillation, mechanical and biochemical changes in subchondral bone, adhesion and chondrogenic commitment of joint-derived mesenchymal stem cells or a change in the molecular milieu of the joint. The overall picture that emerges from the combined evidence is relevant for future research and treatment-related improvements of joint distraction and for translation of the insights gained about tissue repair to other joint-preserving techniques. It remains to be elucidated whether optimizing the biomechanical conditions during joint distraction can actually cure osteoarthritis rather than only providing temporary symptomatic relief, but even temporary relief might be relevant for society and patients, as it will delay joint replacement with a prosthesis at an early age and thereby avert revision surgery later in life. Most importantly, improved insights into the underlying mechanisms of joint repair might provide new leads for more targeted treatment options.

Associations Between Physical Activity, Self-reported Joint Function, and Molecular Biomarkers in Working Age Individuals With Hip and/or Knee Osteoarthritis

Objective:

Previous research has suggested an association between physical activity (PA), joint function, and molecular biomarkers, but more studies are needed. The aim of this study was to explore the associations between PA or self-reported joint function and molecular biomarkers of cartilage and inflammation in individuals with hip and/or knee osteoarthritis (OA). Specific objectives were to explore the correlations between (1) the change over 3 months in self-reported PA/joint function and the change in molecular biomarkers (2) objectively measured PA and molecular biomarkers measured at 3-month follow-up.

Design:

Working age participants (n = 91) were recruited from a cluster randomized controlled trial. Self-reported PA, joint function, and serum samples were collected at baseline and after 3 months. Serum concentrations of the inflammatory marker C-reactive protein (CRP) and the cartilage markers Alanine-Arginine-Glycine-Serine (ARGS)-aggrecan, cartilage oligomeric matrix protein (COMP), and type II collagen C2C were analyzed by immunoassays. Objectively measured PA (steps/day) was collected during 12 weeks from activity trackers used by 53 participants. Associations were analyzed with Spearman’s rank correlation.

Results:

There was a weak negative correlation between the change in self-reported PA and the change in COMP (r_s = −0.256, P = .040) but not for the other molecular biomarkers. There were no correlations between the change in self-reported joint function and the change in molecular biomarkers or between the average steps/day and the molecular biomarkers at follow-up (r_s ⩽ −0.206, P ⩾ .06).

Conclusion:

In general, no or only weak associations were found between PA/joint function and molecular biomarkers. Future research recommends including participants with lower PA, extend the follow-up, and use a design that allows comparisons.

Synovial Fluid Biomarkers in Knee Osteoarthritis: A Systematic Review and Quantitative Evaluation Using BIPEDs Criteria

OBJECTIVE

The aim of this systematic review was to analyze the evidence about the efficacy of the several synovial fluid (SF) biomarkers proposed for knee osteoarthritis (OA), categorizing them by both molecular characteristics and clinical use according to the BIPEDs criteria, to provide a comprehensive and structured overview of the current literature.

DESIGN

A systematic review was performed in May 2020 on PubMed, Cochrane Library, and Embase databases about SF biomarkers in patients with knee OA. The search was limited to articles in the last 20 years on human studies, involving patients with knee OA, reporting SF biomarkers. The evidence for each selected SF biomarker was quantified according to the 6 categories of BIPEDs classification.

RESULTS

A total of 159 articles were included in the qualitative data synthesis and 201 different SF biomarkers were identified. Among these, several were investigated multiple times in different articles, for a total of 373 analyses. The studies included 13,557 patients with knee OA. The most promising SF biomarkers were C4S, IL-6, IL-8, Leptin, MMP-1/3, TIMP-1, TNF-α, and VEGF. The "burden of disease" and "diagnostic" categories were the most represented with 132 and 106 different biomarkers, respectively.

CONCLUSIONS

The systematic review identified numerous SF biomarkers. However, despite the high number of studies on the plethora of identified molecules, the evidence about the efficacy of each biomarker is supported by limited and often conflicting findings. Further research efforts are needed to improve the understanding of SF biomarkers for a better management of patients with knee OA.

Mesenchymal Stem Cell-Derived Exosomes: A Potential Therapeutic Avenue in Knee Osteoarthritis

Knee osteoarthritis is the leading cause of functional disability in adults. The goals of knee osteoarthritis management are directed toward symptomatic pain relief along with the attainment of the functional quality of life. The treatment strategy ranges from conservative to surgical management with reparative and restorative techniques. The emergence of cell-based therapies has paved the way for the usage of mesenchymal stem cells (MSCs) in cartilage disorders. Currently, global researchers are keen on their research on nanomedicine and targeted drug delivery. MSC-derived exosomes act as a directed therapy to halt the disease progression and to provide a pain-free range of movements with increased quality of cartilage on regeneration. International Society for Extracellular Vesicles and the European Network on Microvesicles and Exosomes in Health and Disease have formed guidelines to foster the use of the growing therapeutic potential of exosomal therapy in osteoarthritis. Although regenerative therapies with MSC are being seen to hold a future in the management of osteoarthritis, extracellular vesicle-based technology holds the key to unlock the potential toward knee preservation and regeneration. The intricate composition and uncertain functioning of exosomes are inquisitive facets warranting further exploration.

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.

Immunomodulatory Actions of Mesenchymal Stromal Cells (MSCs) in Osteoarthritis of the Knee

Cellular therapy offers regeneration which curbs osteoarthritis of the knee. Among cellular therapies, mesenchymal stromal cells (MSCs) are readily isolated from various sources as culture expanded and unexpanded cellular population which are used as therapeutic products. Though MSCs possess a unique immunological and regulatory profile through cross-talk between MSCs and immunoregulatory cells (T cells, NK cells, dendritic cells, B cells, neutrophils, monocytes, and macrophages), they provide an immunotolerant environment when transplanted to the site of action. Immunophenotypic profile allows MSCs to escape immune surveillance and promotes their hypoimmunogenic or immune-privileged status. MSCs do not elicit a proliferative response when co-cultured with allogeneic T cells in vitro. MSCs secrete a wide range of anti-inflammatory mediators such as PGE-2, IDO, IL-1Ra, and IL-10. They also stimulate the resilient chondrogenic progenitors and enhance the chondrocyte differentiation by secretion of BMPs and TGFβ1. We highlight the various mechanisms of MSCs during tissue healing signals, their interaction with the immune system, and the impact of their lifespan in the management of osteoarthritis of the knee. A better understanding of the immunobiology of MSC renders them as an efficient therapeutic product for the management of osteoarthritis of the knee.

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.

The CRTAC1 protein in plasma associates with osteoarthritis and predicts progression to joint replacements: a large-scale proteomics scan in Iceland

Objective

Biomarkers for diagnosis and progression of osteoarthritis (OA) are lacking. This study was undertaken to identify circulating biomarkers for OA that could predict disease occurrence and/or progression to joint replacement.

Methods

Using the SomaScan platform, we measured 4,792 proteins in plasma from 37,278 individuals, of whom 12,178 individuals had OA and 2,524 had undergone joint replacement. We performed a case–control study for identification of potential protein biomarkers for hip, knee, and/or hand OA, and a prospective study for identification of biomarkers for joint replacement.

Results

Among the large panel of plasma proteins assessed, cartilage acidic protein 1 (CRTAC1) was the most strongly associated with both OA diagnosis (odds ratio 1.46 [95% confidence interval 1.41–1.52] for knee OA, odds ratio 1.36 [95% confidence interval 1.29–1.43] for hip OA, and odds ratio 1.33 [95% confidence interval 1.26–1.40] for hand OA) and progression to joint replacement (hazard ratio 1.40 [95% confidence interval 1.30–1.51] for knee replacement and hazard ratio 1.31 [95% confidence interval 1.19–1.45] for hip replacement). Patients with OA who were in the highest quintile of risk of joint replacement, based on known risk factors (i.e., age, sex, and body mass index) and plasma CRTAC1 level, were 16 times more likely to undergo knee replacement within 5 years of plasma sample collection than those in the lowest quintile, and 6.5 times more likely to undergo hip replacement. CRTAC1 was not associated with other types of inflammatory arthritis. A specific protein profile was identified in those patients who had undergone joint replacement prior to plasma sample collection.

Conclusion

Through a hypothesis‐free approach, we identified CRTAC1 in plasma as a novel promising candidate biomarker for OA that is both associated with occurrence of OA and predictive of progression to joint replacement. This biomarker might also be useful in the selection of suitable patients for clinical trial enrollment.

Usefulness of serum hyaluronic acid levels as a predictor of incidence of hand osteoarthritis analyzed by longitudinal analysis from the Iwaki cohort

The factors predicting hand osteoarthritis (HOA) in patients remain unknown. We aimed to investigate the usefulness of serum hyaluronic acid (sHA) levels in predicting HOA progression from a 6-year longitudinal epidemiological study. A total of 417 participants in the Iwaki cohort were followed-up over 6 years. Hand and knee radiographs taken at baseline and follow-up were scored according to Kellgren–Lawrence grades and Kallman score. Participants were classified into the HOA group and the non-HOA group. sHA levels at baseline were determined by ELISA. Correlations between sHA levels, the number of involved joints, and Kallman score were estimated. Factors related to the incidence or progression of HOA over 6 years were analyzed. The prevalence of HOA was 19.9% at baseline, and 3.6 ± 2.1 joints were involved. sHA levels in the HOA group at baseline were significantly higher than in the non-HOA group (p < 0.001) and correlated with the number of involved joints (r = 0.399, p < 0.001) and Kallman score (r = 0.540, p < 0.001). The incidence rate was 14.5%, and the progression rate was 46.1% over 6 years. Higher sHA levels at baseline were the risk factor of HOA incidence. Thus, sHA levels predicted the incidence of HOA over 6 years.

Genetic markers of osteoarthritis: early diagnosis in susceptible Pakistani population

Background and aim

Osteoarthritis (OA) is a multiple factorial disease with unidentified specific markers. The alternate method such as biochemical and genetic markers for the diagnosis of osteoarthritis is an undeniable need of the current era. In the present study, we aimed to investigate the association of interleukin-6 (IL-6)(IL-6-174G/C), transforming growth factor-β1 (TGF-beta1-29C/T), and calmodulin 1 gene-16C/T (CALM1-16C/T) polymorphism in clinically definite Pakistani OA patients and matching controls.

Methods

The study design was based on biochemical analysis of OA via serum hyaluronic acid (HA) enzyme-linked immunosorbent assay (ELISA) test and genetic analysis based on amplification refractory mutation system (ARMS) PCR. Statistical evaluations of allele probabilities were carried through chi-squared test. This study includes 295 subjects including 100 OA patients, 105 OA susceptible, and 90 controls.

Results

HA levels obtained were distinct for all the populations: patients with a mean value of ± 5.15, susceptible with mean value of ± 2.27, and control with mean value of ± 0.50. The prevalent genotypes in OA were GG genotype for IL-6-174G/C, CT genotypes for TGF β1-29C/T, and TT genotype for CALM1-16C/T polymorphism. A significant P value of 0.0152 is obtained as a result of the comparison among the patients and controls on the number of individuals possessing the disease-associated genotypes.

Conclusions

The positive association of GG genotype for IL-6-174G/C, TT genotype for CALM1-16C/T polymorphism in OA while high prevalence of CT TGF β1-29 C/T genotypes in susceptible population in our study group implies these polymorphisms can serve as susceptible marker to OA and genetic factors for screening OA patients in Pakistan. There might be other factors that may influence disease susceptibility. However, further investigations on larger population are required to determine the consequences of genetic variations for prediagnosis of OA.

Bone phenotypes in rheumatology - there is more to bone than just bone

Osteoarthritis, rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis, all have one clear common denominator; an altered turnover of bone. However, this may be more complex than a simple change in bone matrix and mineral turnover. While these diseases share a common tissue axis, their manifestations in the area of pathology are highly diverse, ranging from sclerosis to erosion of bone in different regions. The management of these diseases will benefit from a deeper understanding of the local versus systemic effects, the relation to the equilibrium of the bone balance (i.e., bone formation versus bone resorption), and the physiological and pathophysiological phenotypes of the cells involved (e.g., osteoblasts, osteoclasts, osteocytes and chondrocytes). For example, the process of endochondral bone formation in chondrocytes occurs exists during skeletal development and healthy conditions, but also in pathological conditions. This review focuses on the complex molecular and cellular taxonomy of bone in the context of rheumatological diseases that alter bone matrix composition and maintenance, giving rise to different bone turnover phenotypes, and how biomarkers (biochemical markers) can be applied to potentially describe specific bone phenotypic tissue profiles.

Emerging Technologies and Platforms for the Immunodetection of Multiple Biochemical Markers in Osteoarthritis Research and Therapy

Biomarkers, especially biochemical markers, are important in osteoarthritis (OA) research, clinical trials, and drug development and have potential for more extensive use in therapeutic monitoring. However, they have not yet had any significant impact on disease diagnosis and follow-up in a clinical context. Nevertheless, the development of immunoassays for the detection and measurement of biochemical markers in OA research and therapy is an active area of research and development. The evaluation of biochemical markers representing low-grade inflammation or extracellular matrix turnover may permit OA prognosis and expedite the development of personalized treatment tailored to fit particular disease severities. However, currently detection methods have failed to overcome specific hurdles such as low biochemical marker concentrations, patient-specific variation, and limited utility of single biochemical markers for definitive characterization of disease status. These challenges require new and innovative approaches for development of detection and quantification systems that incorporate clinically relevant biochemical marker panels. Emerging platforms and technologies that are already on the way to implementation in routine diagnostics and monitoring of other diseases could potentially serve as good technological and strategic examples for better assessment of OA. State-of-the-art technologies such as advanced multiplex assays, enhanced immunoassays, and biosensors ensure simultaneous screening of a range of biochemical marker targets, the expansion of detection limits, low costs, and rapid analysis. This paper explores the implementation of such technologies in OA research and therapy. Application of novel immunoassay-based technologies may shed light on poorly understood mechanisms in disease pathogenesis and lead to the development of clinically relevant biochemical marker panels. More sensitive and specific biochemical marker immunodetection will complement imaging biomarkers and ensure evidence-based comparisons of intervention efficacy. We discuss the challenges hindering the development, testing, and implementation of new OA biochemical marker assays utilizing emerging multiplexing technologies and biosensors.

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.

The perspectives of intra-articular therapy in the management of osteoarthritis

Management of Osteoarthritis (OA) still is a challenge for clinicians. Taking into account a multidisciplinary approach including pharmacological and non-pharmacological treatments, intra-articular (IA) injection could be considered as an effective local therapy. Areas covered This review provides a new perspective of IA treatment going beyond current available IA agents. We describe novel biological targets for developing new IA agents and innovative modalities of delivery systems. Additional topics include predictors of response for a better choice of IA agents for each patient, diagnostic and prognostic role of biomarkers, accuracy of IA injection, and cost-effectiveness of IA injection. Expert opinion IA treatments seem to be very promising for the management of OA. Identifying clinical and biochemical predictive factors could drive clinician to the appropriate therapeutic approach. To date, there is a gap regarding the benefit of IA treatments in the 'real practice' once they have been adopted. However, considering these promising effects of IA approach, several open questions remain not clarified.

Metabolic Syndrome and Its Effects on Cartilage Degeneration vs Regeneration: A Pilot Study Using Osteoarthritis Biomarkers

BACKGROUND

Osteoarthritis (OA) of the knee is one of the leading causes of disability characterized by degeneration of hyaline cartilage combined with reparative processes. Its strong association with metabolic syndrome is postulated to be due to both mechanical and biochemical factors. Our study aims to study differential effect of metabolic risk factors on cartilage degeneration and regeneration at biomarker level.

DESIGN

After screening 281 patients presenting with knee pain, 41 patients who met the selection criteria were included and were divided into metabolic (MetS) OA and non-metabolic (Non-MetS) OA phenotypes using National Cholesterol Education Programme-Adult Treatment Panel-III (NCEP-ATP-III) criteria for metabolic syndrome. Serum Cartilage Oligomeric Matrix Protein (COMP) and Procollagen type IIA N terminal Propeptide (PIIANP) levels were used as tools to assess cartilage degeneration and regeneration, respectively.

RESULTS

22 among 41 patients (53.66%) had metabolic syndrome. Covariates like age, gender, Kellgren Lawrence (KL) grades were comparable in both groups. MetS-OA group showed significant increase in serum COMP levels (p = 0.03) with no significant effect on serum PIIANP levels (p = 0.46). Hypertriglyceridemia showed independent association with both cartilage anabolism (p = 0.03) and catabolism (p = 0.03).

CONCLUSION

Metabolic syndrome, though has no effect on cartilage regeneration tends to shift cartilage homeostasis towards degeneration with hypertriglyceridemia showing significant independent effect on cartilage metabolism.

Single cell sequencing revealed the underlying pathogenesis of the development of osteoarthritis

Osteoarthritis (OA) is a chronic degenerative change with high incidence and leads to a lower quality of life and a larger socioeconomic burden. This study aimed to explore potential crucial genes and pathways associated with OA that can be used as potential biomarkers forearly treatment. Single-cell gene expression profile of 1464 chondrocytes and 192 fibroblasts in OA were downloaded from the public database (GSE104782 and GSE109449) for subsequent analysis. A total of eight clusters in chondrocytes and three clusters in fibroblasts of OA were identified using the Seurat pipeline and the "SingleR" package for cell-type annotation. Moreover, 44 common marker-genes between fibroblastic-like chondrocytes and fibroblasts were identified and the focal adhesions pathway was further identified as a significant potential mechanism of OA via functional enrichment analysis. Further, the reverse transcription quantitative real-time PCR (RT-qPCR) experiments at tissue's and cellular level confirmed that two key marker-genes (COL6A3 and ACTG1) might participate in the progression of OA. Summarily, we inferred that chondrocytes in OA might up-regulate the expression of COL6A3 and ACTG1 to complete fibroblasts transformation through the focal adhesion pathway. These findings are expected to gain a further insight into the development of OA fibrosis process and provide a promising target for treatment for early OA.

Exosomes: roles and therapeutic potential in osteoarthritis

Exosomes participate in many physiological and pathological processes by regulating cell-cell communication, which are involved in numerous diseases, including osteoarthritis (OA). Exosomes are detectable in the human articular cavity and were observed to change with OA progression. Several joint cells, including chondrocytes, synovial fibroblasts, osteoblasts, and tenocytes, can produce and secrete exosomes that influence the biological effects of targeted cells. In addition, exosomes from stem cells can protect the OA joint from damage by promoting cartilage repair, inhibiting synovitis, and mediating subchondral bone remodeling. This review summarizes the roles and therapeutic potential of exosomes in OA and discusses the perspectives and challenges related to exosome-based treatment for OA patients in the future.

Joint remodeling outcome of serum levels of Dickkopf-1 (DKK1), cartilage oligomeric matrix protein (COMP), and C-telopeptide of type II collagen (CTXII) in rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) is the most widespread chronic inflammatory rheumatic disease over the world. It is characterized by chronic proliferation of synovium, cartilage destruction, and periarticular erosion/bone loss. We investigated the serum levels of the C-telopeptide of type II collagen (CTX-II), Dickkopf-1 (DKK1), and cartilage oligomeric matrix protein (COMP) in relationship to the disease activity.

Material and methods

Serum COMP, CTX-II, and DKK1 levels were measured in 63 RA patients and 50 person age and gender matched as a healthy controls by ELISA test. Disease activity score (DAS) were calculated.

Results

The mean level of and COMP and CTX-II were significantly higher in patients with RA than in healthy controls (5.71 ±7.04 vs. 2.70 ±1.31 ng/ml, and 0.45 ±0.27 vs. 0.23 ±0.16 ng/ml, respectively; p < 0.001). Also, DKK1 serum levels were significantly higher in patients with RA than in healthy controls (6970.68 ±7566.68 vs. 3276.96 ±1306.77 pg/m; p < 0.001). There was a positive significant correlation between DKK1 and swollen joint (r = 0.42, p < 0.001). There were no significant differences in the number of patients, gender, the duration of RA disease, DAS, and RF. Sensitivity was 58.7% and specificity was 85.7% at a cut-off point (> 3.6 ng/ml) for serum COMP in RA patients, while, sensitivity was 100% and specificity was 52.4% at a cut-off point (> 0.15 ng/ml) for serum CTX-II and sensitivity was 68.3% and specificity was 95.2 % at a cut-off point (> 4876 pg/ml) for serum DKK1.

Conclusions

Measurement of some serological biomarkers such as CTX-II, COMP, and DKK1 that reflect bone and cartilage destruction in RA patients could be used to indicate disease activity and early joint affection.

Impact of Exercise Therapy on Molecular Biomarkers Related to Cartilage and Inflammation in Individuals at Risk of, or With Established, Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

To investigate the impact of exercise therapy on molecular biomarkers related to cartilage and inflammation in individuals at risk of, or with established, knee osteoarthritis by conducting a systematic review of randomized controlled trials (RCTs).

METHODS

We conducted a literature search up to September 2017 in 5 major databases with no restriction on publication year or language. Data were extracted from the first available follow-up time point, and we performed a narrative synthesis for the effect of exercise therapy on molecular biomarkers related to cartilage and inflammation. A subset of studies reporting sufficient data was combined in a meta-analysis, using an adjusted random-effects model.

RESULTS

Twelve RCTs involving 57 study comparisons at 4 to 24 weeks following an exercise-therapy intervention were included. Exercise therapy decreased molecular biomarkers in 17 study comparisons (30%), had no effect in 36 (63%), and increased molecular biomarkers in 4 study comparisons (7%). Meta-analyses of 9 biomarkers showed that exercise therapy was associated with nonsignificant reductions of the C-reactive protein level, C-terminal crosslinking telopeptide of type II collagen, tumor necrosis factor (TNF), soluble TNF receptors 1 and 2, C2C neoepitope of type II collagen, and cartilage oligomeric matrix protein, compared to nonexercising control groups, and exercise therapy had no effect on interleukin-6 and soluble interleukin-6 receptor.

CONCLUSION

Exercise therapy is not harmful, because it does not increase the concentration of molecular biomarkers related to cartilage turnover and inflammation, implicated in osteoarthritis progression. The overall quality of evidence was downgraded to low because of the limited number of RCTs available.

FlexPro MD®, a Combination of Krill Oil, Astaxanthin and Hyaluronic Acid, Reduces Pain Behavior and Inhibits Inflammatory Response in Monosodium Iodoacetate-Induced Osteoarthritis in Rats

Osteoarthritis (OA) is a degenerative joint disease and a leading cause of adult disability. Since there is no cure for OA and no effective treatment to slow its progression, current pharmacologic treatments, such as analgesics and non-steroidal anti-inflammatory drugs (NSAIDs), only alleviate symptoms, such as pain and inflammation, but do not inhibit the disease process. Moreover, chronic intake of these drugs may result in severe adverse effects. For these reasons, patients have turned to the use of various complementary and alternative approaches, including diverse dietary supplements and nutraceuticals, in an effort to improve symptoms and manage or slow disease progression. The present study was conducted to evaluate the anti-osteoarthritic effects of FlexPro MD^® (a mixture of krill oil, astaxanthin, and hyaluronic acid; FP-MD) in a rat model of OA induced by monosodium iodoacetate (MIA). FP-MD significantly ameliorated joint pain and decreased the severity of articular cartilage destruction in rats that received oral supplementation for 7 days prior to MIA administration and for 21 days thereafter. Furthermore, FP-MD treatment significantly reduced serum levels of the articular cartilage degeneration biomarkers cartilage oligomeric matrix protein (COMP) and crosslinked C-telopeptide of type II collagen (CTX-II), and the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6), as well as mRNA expression levels of inflammatory mediators, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and matrix-degrading enzymes, matrix metalloproteinase (MMP)-2 and MMP-9, in the knee joint tissue. Our findings suggest that FP-MD is a promising dietary supplement for reducing pain, minimizing cartilage damage, and improving functional status in OA, without the disadvantages of previous dietary supplements and medicinal agents, including multiple adverse effects.

Can urinary CTX-II be a biomarker for knee osteoarthritis?

Background

Early diagnosis of knee osteoarthritis (OA) remains a diagnostic challenge. Urinary C-terminal cross-linked telopeptide of type II collagen (urinary CTX-II) is one of the potential OA biomarkers. However, conclusive evidence regarding the use of this biomarker as a tool for early diagnosis is still lacking. The purposes of this study were to compare urinary CTX-II levels in patients with knee OA and in healthy controls, to evaluate the correlation between urinary CTX-II levels, radiographic severity of OA, and patient-reported outcomes and to evaluate the effect of age and gender on urinary CTX-II levels in the Asian populations.

Methods

Two groups were studied. The OA group included 78 patients with knee OA aged > 40 years who met the diagnostic criteria for knee OA described by the American College of Rheumatology (ACR). The control group consisted of 51 healthy participants age > 40 years without clinical or radiographic evidence of knee OA. Bilateral knee radiographs were taken and classified according to the Kellgren and Lawrence (KL) grading system. Urinary CTX-II was measured using a competitive ELISA test and Western Ontario and Mcmaster Universities Arthritis Index (WOMAC) was also recorded in all participants.

Results

Urinary CTX-II was significantly higher in the OA group than in the control group (p < 0.001). The severe knee OA group (KL grade 3 and 4) had higher urinary CTX-II levels than mild knee OA group (KL grade 2) but the difference did not reach statistical significance (p = 0.2). There was a moderate correlation between urinary CTX-II levels and KL grades (r = 0.405, p < 0.001) and a weak correlation between urinary CTX-II levels and WOMAC index scores (r = 0.367, p < 0.001). Multiple regression analysis showed that urinary CTX-II was independently associated with KL grades. Whereas age, gender, and WOMAC index had no statistically significant influence on the urinary CTX-II levels.

Conclusions

Patients with knee OA had higher urinary CTX-II levels than healthy controls. Moreover, levels of urinary CTX-II were independently correlated with radiographic severity of knee OA. Age, gender, and patient-reported outcomes exerted no effect on the urinary CTX-II levels.

Level of evidence

Diagnostic Level III.

Molecular taxonomy of osteoarthritis for patient stratification, disease management and drug development: biochemical markers associated with emerging clinical phenotypes and molecular endotypes

PURPOSE OF REVIEW

This review focuses on the molecular taxonomy of osteoarthritis from the perspective of molecular biomarkers. We discuss how wet biochemical markers may be used to understand disease pathogenesis and progression and define molecular endotypes of osteoarthritis and how these correspond to clinical phenotypes.

RECENT FINDINGS

Emerging evidence suggests that osteoarthritis is a heterogeneous and multifaceted disease with multiple causes, molecular endotypes and corresponding clinical phenotypes. Biomarkers may be employed as tools for patient stratification in clinical trials, enhanced disease management in the primary care centres of the future and for directing more rational and targeted osteoarthritis drug development. Proximal molecular biomarkers (e.g synovial fluid) are more likely to distinguish between molecular endotypes because there is less interference from systemic sources of biomarker noise, including comorbidities.

SUMMARY

In this review, we have focused on the molecular biomarkers of four distinct osteoarthritis subtypes including inflammatory, subchondral bone remodelling, metabolic syndrome and senescent age-related endotypes, which have corresponding phenotypes. Progress in the field of osteoarthritis endotype and phenotype research requires a better understanding of molecular biomarkers that may be used in conjunction with imaging, pain and functional assessments for the design of more effective, stratified and individualized osteoarthritis treatments.

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.

Coll2-1 and Coll2-1NO2 as exemplars of collagen extracellular matrix turnover - biomarkers to facilitate the treatment of osteoarthritis?

Introduction: Osteoarthritis (OA) is the most common form of arthritis. However, there are no structure or disease-modifying OA drugs (DMOADs). Introducing personalized healthcare to patients and health-care practitioners is a high priority for the management of arthritic and musculoskeletal diseases. However, there are no biomarker tools that can be used for patient stratification, disease management, and drug development. Biomarkers are capable of diagnosing and prognosing some arthritic and musculoskeletal diseases. Cartilage-based biomarkers have the potential to be used in this context to guide the precision treatment of OA. Areas covered: The aim of this review is to focus on the pre-clinical and clinical utility of the Coll2-1 and Coll2-1NO2 biomarkers as unique cartilage-based biomarkers that can guide the development of new treatments for OA. This expert report will begin with a background to collagens and their important biomechanical roles in the musculoskeletal system, but particularly cartilage, before exploring the data and scientific evidence to support the utility of Coll2-1 and Coll2-1NO2 as unique biomarkers. Expert opinion: This review summarises the authors' expert view on the pre-clinical and clinical utility of the Coll2-1 and Coll2-1NO2 biomarkers and their potential for use as drug development tools.

Biomarkers as drug development tools: discovery, validation, qualification and use

The 21st Century Cures Act, approved in the USA in December 2016, has encouraged the establishment of the national Precision Medicine Initiative and the augmentation of efforts to address disease prevention, diagnosis and treatment on the basis of a molecular understanding of disease. The Act adopts into law the formal process, developed by the FDA, of qualification of drug development tools, including biomarkers and clinical outcome assessments, to increase the efficiency of clinical trials and encourage an era of molecular medicine. The FDA and European Medicines Agency (EMA) have developed similar processes for the qualification of biomarkers intended for use as companion diagnostics or for development and regulatory approval of a drug or therapeutic. Biomarkers that are used exclusively for the diagnosis, monitoring or stratification of patients in clinical trials are not subject to regulatory approval, although their qualification can facilitate the conduct of a trial. In this Review, the salient features of biomarker discovery, analytical validation, clinical qualification and utilization are described in order to provide an understanding of the process of biomarker development and, through this understanding, convey an appreciation of their potential advantages and limitations.

Establishing outcome measures in early knee osteoarthritis

The classification and monitoring of individuals with early knee osteoarthritis (OA) are important considerations for the design and evaluation of therapeutic interventions and require the identification of appropriate outcome measures. Potential outcome domains to assess for early OA include patient-reported outcomes (such as pain, function and quality of life), features of clinical examination (such as joint line tenderness and crepitus), objective measures of physical function, levels of physical activity, features of imaging modalities (such as of magnetic resonance imaging) and biochemical markers in body fluid. Patient characteristics such as adiposity and biomechanics of the knee could also have relevance to the assessment of early OA. Importantly, research is needed to enable the selection of outcome measures that are feasible, reliable and validated in individuals at risk of knee OA or with early knee OA. In this Perspectives article, potential outcome measures for early symptomatic knee OA are discussed, including those measures that could be of use in clinical practice and/or the research setting.