Clusters of biochemical markers are associated with radiographic subtypes of osteoarthritis (OA) in subject with familial OA at multiple sites. The GARP study

Molecular mechanisms of the Guizhi decoction on osteoarthritis based on an integrated network pharmacology and RNA sequencing approach with experimental validation

Background: Our aim was to determine the potential pharmacological mechanisms of the Guizhi decoction (GZD) in the treatment of osteoarthritis (OA) through an integrated approach of network pharmacological analyses, RNA sequencing (RNA-seq), and experimental validation. Methods: The quality control and identification of bioactive compounds of the GZD were carried out by using ultra-performance liquid chromatography (UPLC), and their OA-related genes were identified through overlapping traditional Chinese medicine systems pharmacology database (TCMSP), DrugBank and SEA Search Server databases, and GeneCards. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were implemented after constructing the component-target network. RNA-seq was used to screen differentially expressed genes (DEGs) under intervention conditions with and without the GZD in vitro. The crossover signaling pathways between RNA-seq and network pharmacology were then analyzed. Accordingly, protein-protein interaction (PPI) networks, GO, and KEGG analysis were performed using the Cytoscape, STRING, or DAVID database. The OA rat model was established to further verify the pharmacological effects in vivo. Hematoxylin-eosin (H&E) and safranin O/fast green (S-O) staining were used to grade the histopathological features of the cartilage. We verified the mRNA and protein expressions of the key targets related to the TNF signaling pathways in vivo and in vitro by qPCR, Western blotting (WB), and immunofluorescence assay. In addition, we also detected inflammatory cytokines in the rat serum by Luminex liquid suspension chip, which included tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). Results: Eighteen compounds and 373 targets of the GZD were identified. A total of 2,356 OA-related genes were obtained from the GeneCards database. A total of three hub active ingredients of quercetin, kaempferol, and beta-sitosterol were determined, while 166 target genes associated with OA were finally overlapped. The RNA-seq analysis revealed 1,426 DEGs. In the KEGG intersection between network pharmacology and RNA-seq analysis, the closest screening relevant to GZD treatment was the TNF signaling pathway, of which TNF, IL-6, and IL-1β were classified as hub genes. In consistent, H&E and S-O staining of the rat model showed that GZD could attenuate cartilage degradation. When compared with the OA group in vivo and in vitro, the mRNA levels of TNF-α, IL-1β, IL-6, matrix metalloproteinase 3 (MMP3), and matrix metalloproteinase 9 (MMP9) were all downregulated in the GZD group (all p < 0.05). The expression levels of anabolic proteins (Col2α1 and SOX9) were all higher in the GZD group than in the OA group (p < 0.05), while the expression levels of the catabolic proteins (MMP9 and COX-2) and TNF-α in the GZD group were significantly lower than those in the OA group (p < 0.05). In addition, the expression levels of TNF, IL-6, and IL-1β were upregulated in the OA group, while the GZD group prevented such aberrations (p < 0.01). Conclusion: The present study reveals that the mechanism of the GZD against OA may be related to the regulation of the TNF signaling pathway and inhibition of inflammatory response.

Knee Osteoarthritis-How Close Are We to Disease-Modifying Treatment: Emphasis on Metabolic Type Knee Osteoarthritis

Osteoarthritis (OA) is a whole-joint disease that affects cartilage, bone, and synovium as well as ligaments, menisci, and muscles [...].

An osteoarthritis subtype characterized by synovial lipid metabolism disorder and fibroblast-like synoviocyte dysfunction

Background

The heterogeneity of osteoarthritis (OA) significantly limits the effectiveness of pharmacological treatments in an unselected patient population. In this context, the identification of OA subtypes is meaningful for the development of therapies that target specific types of OA pathogenesis.

Methods

Expression array profiles of 70 OA and 36 control synovial samples were extracted from the GEO database. Unsupervised consensus clustering was performed based on the most variable genes to identify OA subclusters. Next, Joint samples from OA patients were obtained. We divided the OA patient into two subpopulations according to synovial ADCY7 levels. Synovium and cartilage samples from different OA subpopulations were evaluated. In addition, we established a high-fat diet (HFD)-induced rat OA model. We evaluated OA progression, lipid metabolism, synovitis and fibroblast-like synoviocytes (FLS) function in this HFD-induced OA model.

Results

70 OA patients were categorized into three distinct subclusters. We noted that one subcluster was characterized by synovial lipid metabolism disorder GO terms. We further identified the most noticeable KEGG pathway “Regulation of lipolysis in adipocytes” in this subcluster as well as the most significantly differentially expressed gene, ADCY7. We found that the ADCY7 high expressing group (32.6%) exhibited features of synovial inflammatory lipolysis epithelial-mesenchymal transition (EMT) tendency, as well as faster join space narrowing. The HFD induced OA-like degeneration in rat joints. We observed similar synovial inflammatory lipolysis and EMT in FLS, characterized by higher proliferative and invasive activity and elevated proinflammatory and procatabolic properties. ADCY7 was highly expressed in the synovium of the HFD-OA model rats and the inhibition of ADCY7 effectively attenuated these HFD-induced degenerative changes as well as synovial inflammatory lipolysis and FLS dysfunction. In HFD-FLSs, ADCY7 promoted the phosphorylation of PKA as well as its downstream lipid droplet-associated protein PLIN1 and hormone-sensitive lipase (HSL). The inhibition of PKA largely alleviated ADCY7-mediated HFD-FLS dysfunction.

Conclusions

We described a synovial EMT and lipid metabolism disorder in the pathogenesis of OA. This novel mechanism may represent a currently undefined OA subtype. ADCY7 is a potential molecular marker of this pathomechanism.

The Translational potential of this article

Utilizing synovial samples from OA patients, we identified a subpopulation with high ADCY7 expression. This may represent a currently undefined OA subtype and explain the clinical phenomenon of more severe synovial inflammation in obese OA patients. In addition, we established an HFD-induced OA rat model and found an upregulation of ADCY7 in the synovium. We confirmed that the inhibition of ADCY7 could effectively attenuate HFD-induced degenerative changes as well as the inflammatory lipolysis and FLS dysfunction observed in the rat model. This suggests that ADCY7 and its downstream pathways are potential pharmacological targets for treating this lipid-metabolism-disorder-related OA mechanism.

Scoring Osteoarthritis Reliably in Large Joints and the Spine Using Whole-Body CT: OsteoArthritis Computed Tomography-Score (OACT-Score)

A standardized method to assess structural osteoarthritis (OA) burden thorough the body lacks from literature. Such a method can be valuable in developing personalized treatments for OA. We developed a reliable scoring system to evaluate OA in large joints and the spine-the OsteoArthritis Computed Tomography (OACT) score, using a convenience sample of 197 whole-body low-dose non-contrast CTs. An atlas, containing example images as reference points for training and scoring, are presented. Each joint was graded between 0-3. The total OA burden was calculated by summing scores of individual joints. Intra- and inter-observer reliability was tested 25 randomly selected scans (N = 600 joints). Intra-observer reliability and inter-observer reliability between three observers was assessed using intraclass correlation coefficient (ICC) and square-weighted kappa statistics. The square-weighted kappa for intra-observer reliability for OACT-score at joint-level ranged from 0.79 to 0.95; the ICC for the total OA grade was 0.97 (95%-CI, 0.94 to 0.99). Square-weighted kappa for interobserver reliability ranged from 0.48 to 0.95; the ICC for the total OA grade was 0.95 (95%-CI, 0.90 to 0.98). The OACT score, a new reproducible CT-based grading system reflecting OA burden in large joints and the spine, has a satisfactory reproducibility. The atlas can be used for research purposes, training, educational purposes and systemic grading of OA on CT-scans.

Serum fatty acid chain length associates with prevalent symptomatic end-stage osteoarthritis, independent of BMI

Higher body mass index (BMI) is associated with osteoarthritis (OA) in both weight-bearing and non-weight-bearing joints, suggesting a link between OA and poor metabolic health beyond mechanical loading. This risk may be influenced by systemic factors accompanying BMI. Fluctuations in concentrations of metabolites may mark or even contribute to development of OA. This study explores the association of metabolites with radiographic knee/hip OA prevalence and progression. A ¹H-NMR-metabolomics assay was performed on plasma samples of 1564 cases for prevalent OA and 2,125 controls collected from the Rotterdam Study, CHECK, GARP/NORREF and LUMC-arthroplasty cohorts. OA prevalence and 5 to 10 year progression was assessed by means of Kellgren-Lawrence (KL) score and the OARSI-atlas. End-stage knee/hip OA (TJA) was defined as indication for arthroplasty surgery. Controls did not have OA at baseline or follow-up. Principal component analysis of 227 metabolites demonstrated 23 factors, of which 19 remained interpretable after quality-control. Associations of factor scores with OA definitions were investigated with logistic regression. Fatty acids chain length (FALen), which was included in two factors which associated with TJA, was individually associated with both overall OA as well as TJA. Increased Fatty Acid chain Length is associated with OA.

Arthritis and the role of endogenous glucocorticoids

Rheumatoid arthritis and osteoarthritis, the most common forms of arthritis, are chronic, painful, and disabling conditions. Although both diseases differ in etiology, they manifest in progressive joint destruction characterized by pathological changes in the articular cartilage, bone, and synovium. While the potent anti-inflammatory properties of therapeutic (i.e., exogenous) glucocorticoids have been heavily researched and are widely used in clinical practice, the role of endogenous glucocorticoids in arthritis susceptibility and disease progression remains poorly understood. Current evidence from mouse models suggests that local endogenous glucocorticoid signaling is upregulated by the pro-inflammatory microenvironment in rheumatoid arthritis and by aging-related mechanisms in osteoarthritis. Furthermore, these models indicate that endogenous glucocorticoid signaling in macrophages, mast cells, and chondrocytes has anti-inflammatory effects, while signaling in fibroblast-like synoviocytes, myocytes, osteoblasts, and osteocytes has pro-inflammatory actions in rheumatoid arthritis. Conversely, in osteoarthritis, endogenous glucocorticoid signaling in both osteoblasts and chondrocytes has destructive actions. Together these studies provide insights into the role of endogenous glucocorticoids in the pathogenesis of both inflammatory and degenerative joint disease.

Functional analysis of synovial fluid from osteoarthritic knee and carpometacarpal joints unravels different molecular profiles

OBJECTIVE

In this work, we aimed to elucidate the molecular mechanisms driving primary OA. By studying the dynamics of protein expression in two different types of OA joints we searched for similarities and disparities to identify key molecular mechanisms driving OA.

METHODS

For this purpose, human SF samples were obtained from CMC-I OA and knee joint of OA patients. SF samples were analysed by label-free quantitative liquid chromatography mass spectrometry. Disease-relevant proteins identified in proteomics studies, such as clusterin, paraoxonase/arylesterase 1 (PON1) and transthyretin were validated by enzyme-linked immunosorbent assays, and on the mRNA level by droplet digital PCR. Functional studies were performed in vitro using primary chondrocytes.

RESULTS

Differential proteomic changes were observed in the concentration of 40 proteins including clusterin, PON1 and transthyretin. Immunoassay analyses of clusterin, PON1, transthyretin and other inflammatory cytokines confirmed significant differences in protein concentration in SF of CMC-I and knee OA patients, with primarily lower protein expression levels in CMC-I. Functional studies on chondrocytes unequivocally demonstrated that stimulation with SF obtained from knee OA, in contrast to CMC-I OA joint, caused a significant upregulation in pro-inflammatory response, cell death and hypertrophy.

CONCLUSION

This study demonstrates that differential expression of molecular players in SF from different OA joints evokes diverse effects on primary chondrocytes. The pathomolecular mechanisms of OA may significantly differ in various joints, a finding that brings a new dimension into the pathogenesis of primary OA.

A dual amylin and calcitonin receptor agonist inhibits pain behavior and reduces cartilage pathology in an osteoarthritis rat model

OBJECTIVES

Pain and disability are the main clinical manifestations of osteoarthritis, for which only symptomatic therapies are available. Hence, there is a need for therapies that can simultaneously alter disease progression and provide pain relief. KBP is a dual amylin- and calcitonin-receptor agonist with antiresorptive and chondroprotective properties. In this study we investigated the effect of KBP in a rat model of osteoarthritis.

METHODS

Medial meniscectomy (MNX) was performed in 39 rats, while 10 underwent sham surgery. Rats were treated with KBP and/or naproxen. Nociception was assessed by mechanical and cold allodynia, weight bearing asymmetry, and burrowing behavior. Blood samples were collected for biomarker measurements, and knees for histology. Cartilage histopathology was evaluated according to the advanced Osteoarthritis Research International (OARSI) score and KBPs in vitro antiresorptive effects were assessed using human osteoclasts cultured on bone.

RESULTS

The MNX animals displayed an increased nociceptive behavior. Treatment with KBP attenuated the MNX-induced osteoarthritis-associated joint pain. The cartilage histopathology was significantly lower in rats treated with KBP than in MNX animals. Bone and cartilage degradation, assessed by CTX-I and CTX-II plasma levels, were decreased in all KBP-treated groups and KBP potently inhibited bone resorption in vitro.

CONCLUSIONS

Our study demonstrates the effectiveness of KBP in ameliorating osteoarthritis-associated joint pain and in protecting the articular cartilage, suggesting KBP as a potential drug candidate for osteoarthritis.

Network Pharmacology Identifies the Mechanisms of Action of Shaoyao Gancao Decoction in the Treatment of Osteoarthritis

BACKGROUND Osteoarthritis (OA) affects the health and wellbeing of the elderly. Shaoyao Gancao decoction (SGD) is used in traditional Chinese medicine (TCM) for the treatment of OA and has two active components, shaoyao (SY) and gancao (GC). This study aimed to undertake a network pharmacology analysis of the mechanism of the effects of SGD in OA. MATERIAL AND METHODS The active compounds and candidates of SGD were obtained from the Traditional Chinese Medicine (TCM) Databases@Taiwan, the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, the STITCH database, the ChEMBL database, and PubChem. The network pharmacology approach involved network construction, target prediction, and module analysis. Significant signaling pathways of the cluster networks for SGD and OA were identified using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. RESULTS Twenty-three bioactive compounds were identified, corresponding to 226 targets for SGD. Also, 187 genes were closely associated with OA, of which 161 overlapped with the targets of SGD and were considered to be therapeutically relevant. Functional enrichment analysis suggested that SGD exerted its pharmacological effects in OA by modulating multiple pathways, including cell cycle, cell apoptosis, drug metabolism, inflammation, and immune modulation. CONCLUSIONS A novel approach was developed to systematically identify the mechanisms of the TCM, SGD in OA using network pharmacology analysis.

IL-37 diminishes proteoglycan loss in human OA cartilage: donor-specific link between IL-37 and MMP-3

OBJECTIVE

A hallmark of osteoarthritis (OA) is degradation of articular cartilage proteoglycans. In isolated human OA chondrocytes, the anti-inflammatory cytokine Interleukin-37 (IL-37) lowers the expression of the proteolytic MMP and ADAMTS enzymes, which mediate this degradation. Therefore, we investigated if IL-37 protects against proteoglycan loss in freshly obtained human OA explants.

MATERIAL AND METHODS

Human OA cartilage explants were incubated with IL-37. Release of sulphated proteoglycans (sGAGs) was measured with the dimethylmethylene-blue assay. Production and degradation of newly synthesized proteoglycans was measured using ³⁵S-sulphate. Proteoglycan and proteolytic enzyme expression were analyzed by qPCR and Western Blot. Proteolytic activity was determined by measuring MMP- and ADAMTS-generated aggrecan neo-epitopes with ELISA and by using MMP-3-, MMP-13- or ADAMTS-5-inhibitors.

RESULTS

Over time, a linear release of sGAGs from OA cartilage was measured. IL-37 reduced this release by 87 μg/ml (24%) 95%CI [21.04-141.4]. IL-37 did not affect ³⁵S-sulphate incorporation or proteoglycan gene expression. In contrast, IL-37 reduced loss of ³⁵S-sulphate labeled GAGs and reduced MMP-3 protein expression, indicating that IL-37 inhibits proteoglycan degradation. Remarkably, we observed two groups of patients; one group in which MMP-3-inhibition lowered sGAG release, and one group in which ADAMTS5-inhibition had this effect. Remarkably, IL-37 was only functional in the group of patients that responded to MMP-3-inhibition.

CONCLUSION

We identified a relationship between IL-37 and reduced sGAG loss in OA cartilage. Most likely, this effect is mediated by inhibition of MMP-3 expression. These results suggest that IL-37 could be applied as therapy in a subgroup of OA patients, in which cartilage degradation is mediated by MMP-3.

Is osteoarthritis one disease or a collection of many?

OA is a multifaceted and heterogeneous syndrome that may be amenable to tailored treatment. There has been an increasing focus within the OA research community on the identification of meaningful OA phenotypes with potential implications for prognosis and treatment. Experimental and clinical data combined with sophisticated statistical approaches have been used to characterize and define phenotypes from the symptomatic and structural perspectives. An improved understanding of the existing phenotypes based on underlying disease mechanisms may shed light on the distinct entities that make up the disease. This narrative review provides an updated summary of the most recent advances in this field as well as limitations from previous approaches that can be addressed in future studies.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Knee osteoarthritis phenotypes and their relevance for outcomes: a systematic review

OBJECTIVE

To systematically review the literature for studies investigating knee osteoarthritis (OA) phenotypes to examine what OA characteristics are relevant for phenotyping.

METHODS

A comprehensive search was performed in Medline, EMBASE, Web of Sciences, CINAHL, and Scopus databases from inception to September 2016. Inclusion was limited to observational studies of individuals with symptomatic knee OA that identified phenotypes based on any OA characteristics and assessed their association with clinically important outcomes. A descriptive synthesis of the data was performed.

RESULTS

Of the 2777 citations retrieved, 34 studies were included. Clinical phenotypes were investigated most frequently, followed by laboratory, imaging and aetiologic phenotypes. Eight studies defined subgroups based on outcome trajectories (pain, function and radiographic progression trajectories). Most studies used a single patient or disease characteristic to identify patients subgroups while five included characteristics from multiple domains. We found evidence from multiple studies suggesting that pain sensitization, psychological distress, radiographic severity, body mass index (BMI), muscle strength, inflammation and comorbidities are associated with clinically distinct phenotypes. Gender, obesity and other metabolic abnormalities, the pattern of cartilage damage, and inflammation may be implicated in delineating distinct structural phenotypes. Only a few studies investigated the external validity of the phenotypes or their prospective validity using longitudinal outcomes.

CONCLUSIONS

There is marked heterogeneity in the data selected by the studies investigating knee OA phenotypes. We identified the phenotypic characteristics that can be considered for a comprehensive phenotype classification in future studies. A framework for the investigation of phenotypes could be useful for future studies.

PROTOCOL REGISTRATION

PROSPERO CRD42016036220.

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

Objective

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

Methods

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

Results

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

Conclusions

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

Plasma vitamin D and osteo-cartilaginous markers in Italian males affected by intervertebral disc degeneration: Focus on seasonal and pathological trend of type II collagen degradation

OBJECTIVE

To evaluate plasma vitamin D and cross-linked C-telopeptides of type I (CTx-I) and type II (CTx-II) collagen concentrations in males with lumbar intervertebral disc degeneration (IVD) compared to healthy controls. Improved knowledge might suggest to optimize the vitamin D status of IVD patients and contribute to clarify mechanisms of cartilage degradation.

METHODS

79 Italian males with lumbar IVD assessed by Magnetic Resonance Imaging (MRI) and 79 age, sex and BMI-matched healthy controls were enrolled. Plasma 25hydroxyvitamin D (25(OH)D), CTx-I and CTx-II were measured by immunoassays. Circannual seasonality, correlation between biomarkers concentrations and clinical variables were assessed.

RESULTS

Overall subjects 25(OH)D and CTx-II showed month rhythmicity with acrophase in August/September and October/November, and nadir in February/March and April/May, respectively. An inverse correlation between 25(OH)D and CTx-I, and a direct correlation between CTx-II and CTx-I were observed. IVD patients, particularly with osteochondrosis, showed higher CTx-II than healthy controls.

CONCLUSIONS

Month of sampling may affect plasma 25(OH)D and CTx-II concentrations. The correlation between CTx-I and CTx-II suggests an interplay between the osteo-cartilaginous endplate and the fibro-cartilaginous disc. The results of this study highlighted that osteochondrosis associates with increased cartilaginous catabolism. Vitamin D supplementation seems more necessary in winter for lumbar IVD patients.

Physical activity levels and quality of life relate to collagen turnover and inflammation changes after running

The purpose of this study was to determine whether an association existed between self-reported symptom and function scores and tissue turnover or inflammatory biomarker changes after a running bout among individuals with and without an acute knee-injury history. A pre-test/post-test prospective cohort study design (Level II) of 22 participants was conducted. Eleven physically active individuals with a history of anterior cruciate ligament surgery and/or meniscus surgery within 4 years of study participation were matched to 11 healthy control participants. All participants completed self-reported outcome measures (Knee Osteoarthritis Outcomes Score and Tegner activity level) assessing knee symptoms and functional levels prior to the run. Blood samples were taken both pre- and post-30-minute run at a prescribed pace on a treadmill to determine serum biomarker concentration changes. Tegner activity levels were inversely related to type II collagen/type II collagen synthesis marker ratio biomarker changes after the run (r = -0.45, p = 0.01). Quality-of-life scores pre-exercise were inversely related to interleukin-1β changes after the run (r = -0.50, p = 0.02). No other correlation coefficients were statistically significant (r = -0.39 to 0.36). Ultimately, individuals with lower activity and quality-of-life scores experienced greater increases in collagen turnover and inflammation after a running bout, respectively. A gradual increase in activity (e.g., frequency, duration, intensity) may be warranted in this group prior to returning to activities that involve running. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:612-617, 2017.

Impact of physical activity and mechanical loading on biomarkers typically used in osteoarthritis assessment: current concepts and knowledge gaps

There is an ongoing need to develop prognostic and diagnostic biomarkers for osteoarthritis (OA). Understanding how biomarkers change in response to physical activity may be vital for understanding if a patient has a joint that is failing to adapt to a given loading stimulus. The purpose of this review is to describe how biomarker changes after joint loading may help detect early OA and determine prognosis. This may help to inform and more specifically target interventions and clinical trials. We conducted a critical review of the relevant literature that was published to January 2016. There is extensive OA biomarker research, specifically basal biomarker concentrations; however, there is limited research surrounding biomarker response to load. Some of this limited research includes the response of minimal biomarkers reflecting bone, synovium, inflammatory, and cartilage responses to load. Biomarker changes occur in bone and cartilage in response to a variety of activities and are influenced by variables such as body weight, load, vibration, and activity time. Biomarker responses to loading tasks may serve as a measure of overall joint health and be predictive of structural changes. Biomarkers adapt to training over time, and this may indicate a need for a gradual return to physical activity after an injury to allow time for joint tissues to adapt to load. Biomarker responses to physical activity may be monitored to determine appropriate loading levels and safety for return to activity.

Calcitonin attenuates cartilage degeneration and nociception in an experimental rat model of osteoarthritis: role of TGF-β in chondrocytes

We investigated the role of the calcitonin (Miacalcin) in the progression of osteoarthritis (OA) and in nociceptive behavior in an experimental rat model of OA and osteoporosis. OA was induced by anterior cruciate ligament transection (ACLT) of the right knee and by bilateral ovariectomy (OVX) in Wistar rats. Nociceptive behaviors (secondary mechanical allodynia and weight-bearing distribution of the hind paws) were analyzed prior to surgery and every week, beginning at 12 weeks after surgery, up to 20 weeks. At 20 weeks, histopathological studies were performed on the cartilage of the knee joints. Immunohistochemical analysis was performed to examine the effect of calcitonin on transforming growth factor (TGF)-β1 expression in articular cartilage chondrocytes. Rats subjected to ACLT + OVX surgery showed obvious OA changes in the joints. Animals subjected to ACLT + OVX and treated with calcitonin showed significantly less cartilage degeneration and improved nociceptive tests compared with animals subjected to ACLT + OVX surgeries alone. Moreover, calcitonin increased TGF-β1 expression in chondrocytes in ACLT + OVX-affected cartilage. Subcutaneous injection of calcitonin (1) attenuated the development of OA, (2) concomitantly reduced nociception, and (3) modulated chondrocyte metabolism, possibly by increasing cellular TGF-β1 expression.

DNA Methylation in Osteoarthritis

Osteoarthritis (OA) is a prevalent disease of articular joints and primarily characterized by degradation and calcification of articular cartilage. Presently, no effective treatment other than pain relief exists and patients ultimately need to undergo replacement surgery of the affected joint. During disease progression articular chondrocytes, the single cell type present in articular cartilage, show altered transcriptional profiles and undergo phenotypic changes that resemble the terminal differentiation route apparent in growth plate chondrocytes. Hence, given its prominent function in both regulating gene expression and maintaining cellular phenotypes, DNA methylation of CpG dinucleotides is intensively studied in the context of OA. An increasing number of studies have been published that employed a targeted approach on genes known to play a role in OA pathophysiology. As of such, it has become clear that OA responsive DNA methylation changes seem to mediate disease associated aberrant gene expression. Furthermore, established OA susceptibility alleles such as GDF5 and DIO2 appear to confer OA risk via DNA methylation and respective pathophysiological expression changes. In more recent years, genome wide profiling of DNA methylation in OA affected articular cartilage has emerged as a powerful tool to address the epigenetic changes in their entirety, which has resulted in the identification of putative patient subgroups as well as generic OA associated pathways.

Plasma levels of interleukin-1 receptor antagonist (IL1Ra) predict radiographic progression of symptomatic knee osteoarthritis

OBJECTIVE

Pro- and anti-inflammatory mediators, such as IL-1β and IL1Ra, are produced by joint tissues in osteoarthritis (OA), where they may contribute to pathogenesis. We examined whether inflammatory events occurring within joints are reflected in plasma of patients with symptomatic knee osteoarthritis (SKOA).

DESIGN

111 SKOA subjects with medial disease completed a 24-month prospective study of clinical and radiographic progression, with clinical assessment and specimen collection at 6-month intervals. The plasma biochemical marker IL1Ra was assessed at baseline and 18 months; other plasma biochemical markers were assessed only at 18 months, including IL-1β, TNFα, VEGF, IL-6, IL-6Rα, IL-17A, IL-17A/F, IL-17F, CRP, sTNF-RII, and MMP-2.

RESULTS

In cross-sectional studies, WOMAC (total, pain, function) and plasma IL1Ra were modestly associated with radiographic severity after adjustment for age, gender and body mass index (BMI). In addition, elevation of plasma IL1Ra predicted joint space narrowing (JSN) at 24 months. BMI did associate with progression in some but not all analyses. Causal graph analysis indicated a positive association of IL1Ra with JSN; an interaction between IL1Ra and BMI suggested either that BMI influences IL1Ra or that a hidden confounder influences both BMI and IL1Ra. Other protein biomarkers examined in this study did not associate with radiographic progression or severity.

CONCLUSIONS

Plasma levels of IL1Ra were modestly associated with the severity and progression of SKOA in a causal fashion, independent of other risk factors. The findings may be useful in the search for prognostic biomarkers and development of disease-modifying OA drugs.

Republished: Value of biomarkers in osteoarthritis: current status and perspectives

Osteoarthritis affects the whole joint structure with progressive changes in cartilage, menisci, ligaments and subchondral bone, and synovial inflammation. Biomarkers are being developed to quantify joint remodelling and disease progression. This article was prepared following a working meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis convened to discuss the value of biochemical markers of matrix metabolism in drug development in osteoarthritis. The best candidates are generally molecules or molecular fragments present in cartilage, bone or synovium and may be specific to one type of joint tissue or common to them all. Many currently investigated biomarkers are associated with collagen metabolism in cartilage or bone, or aggrecan metabolism in cartilage. Other biomarkers are related to non-collagenous proteins, inflammation and/or fibrosis. Biomarkers in osteoarthritis can be categorised using the burden of disease, investigative, prognostic, efficacy of intervention, diagnostic and safety classification. There are a number of promising candidates, notably urinary C-terminal telopeptide of collagen type II and serum cartilage oligomeric protein, although none is sufficiently discriminating to differentiate between individual patients and controls (diagnostic) or between patients with different disease severities (burden of disease), predict prognosis in individuals with or without osteoarthritis (prognostic) or perform so consistently that it could function as a surrogate outcome in clinical trials (efficacy of intervention). Future avenues for research include exploration of underlying mechanisms of disease and development of new biomarkers; technological development; the ‘omics’ (genomics, metabolomics, proteomics and lipidomics); design of aggregate scores combining a panel of biomarkers and/or imaging markers into single diagnostic algorithms; and investigation into the relationship between biomarkers and prognosis.

Heritability assessment of cartilage metabolism. A twin study on circulating procollagen IIA N-terminal propeptide (PIIANP)

OBJECTIVE

The aim of this investigation was to estimate the heritability of circulating collagen IIA N-terminal propeptide (PIIANP) by studying mono- and dizygotic healthy twin pairs at different age and both genders.

DESIGN

598 monozygotic (MZ) and dizygotic (DZ) twin individuals aged 18-59 years were recruited from the Danish Twin Registry. PIIANP was measured by competitive ELISA. The similarity of circulating PIIANP among MZ and DZ twins was assessed by intraclass correlations according to traits. The heritability was estimated by variance component analysis accounting for additive and dominant genetic factors as well as shared and non-shared environment but ignoring epistasis (genetic inter-locus interaction) and gene-environment interaction.

RESULTS

The intraclass correlation of PIIANP in MZ and DZ twins was 0.69 (0.60-0.76) and 0.46 (0.34-0.58) respectively indicating a significant genetic impact on PIIANP in serum. Additive genetic effects explained 45% (21-70%), shared environment 24% (7-53%) and non-shared environment 31% (24-39%) of the total variance. The heritability estimate did not differ across ages and between genders.

CONCLUSIONS

The study shows that approximately 45% of the collagen IIA synthesis as assessed by the collagen IIA N-terminal propeptide in serum is attributable to genetic effectors while individual and shared environment account for 24% and 31% respectively. The heritability does not differ between genders or according to age.

Meta-analysis identifies loci affecting levels of the potential osteoarthritis biomarkers sCOMP and uCTX-II with genome wide significance

BACKGROUND

Research for the use of biomarkers in osteoarthritis (OA) is promising, however, adequate discrimination between patients and controls may be hampered due to innate differences. We set out to identify loci influencing levels of serum cartilage oligomeric protein (sCOMP) and urinary C-telopeptide of type II collagen (uCTX-II).

METHODS

Meta-analysis of genome-wide association studies was applied to standardised residuals of sCOMP (N=3316) and uCTX-II (N=4654) levels available in 6 and 7 studies, respectively, from TreatOA. Effects were estimated using a fixed-effects model. Six promising signals were followed up by de novo genotyping in the Cohort Hip and Cohort Knee study (N = 964). Subsequently, their role in OA susceptibility was investigated in large-scale genome-wide association studies meta-analyses for OA. Differential expression of annotated genes was assessed in cartilage.

RESULTS

Genome-wide significant association with sCOMP levels was found for a SNP within MRC1 (rs691461, p = 1.7 × 10(-12)) and a SNP within CSMD1 associated with variation in uCTX-II levels with borderline genome-wide significance (rs1983474, p = 8.5 × 10(-8)). Indication for association with sCOMP levels was also found for a locus close to the COMP gene itself (rs10038, p = 7.1 × 10(-6)). The latter SNP was subsequently found to be associated with hip OA whereas COMP expression appeared responsive to the OA pathophysiology in cartilage.

CONCLUSIONS

We have identified genetic loci affecting either uCTX-II or sCOMP levels. The genome wide significant association of MRC1 with sCOMP levels was found likely to act independent of OA subtypes. Increased sensitivity of biomarkers with OA may be accomplished by taking genetic variation into account.

Associations between biomarkers of joint metabolism, hand osteoarthritis, and hand pain and function: the Johnston County Osteoarthritis Project

OBJECTIVE

To determine the associations between joint metabolism biomarkers and hand radiographic osteoarthritis [(rOA), based on Kellgren Lawrence (KL) grade ≥ 2], symptoms, and function.

METHODS

Cross-sectional data were available for 663 participants (mean age 63 yrs, 63% white, 49% women). Three definitions of hand rOA were considered: (1) a composite measure involving at least 3 hand joints distributed bilaterally with 2 of 3 in the same joint group, including ≥ 1 distal interphalangeal joint, without metacarpophalangeal (MCP) swelling; (2) rOA in at least 1 joint of a group; and (3) number of joints with KL ≥ 2. We assessed hand symptoms and the 15-item Australian Canadian Hand Osteoarthritis Index (AUSCAN; Likert format). We measured serum cartilage oligomeric matrix protein (sCOMP), hyaluronic acid (sHA), carboxy-terminal propeptide of type II collagen, type II collagen degradation product, urinary C-terminal crosslinked telopeptide of type II collagen, and urinary N-terminal crosslinked telopeptide. Linear regression models were performed to assess associations between each biomarker with hand rOA, AUSCAN, and symptoms, adjusting for age, sex, race, current smoking/drinking status, body mass index, and hip and knee rOA.

RESULTS

In adjusted analyses, MCP (p < 0.0001) and carpometacarpal rOA (p = 0.003), and a higher number of hand joints with rOA (p = 0.009), were associated with higher levels of sHA. Positive associations were seen between AUSCAN and hand symptoms and levels of sCOMP (p ≤ 0.003) and sHA (p ≤ 0.048).

CONCLUSION

Hand symptoms and higher AUSCAN scores were independently associated with higher levels of both sCOMP and sHA; hand rOA was associated only with sHA levels.

Role of hormones in cartilage and joint metabolism: understanding an unhealthy metabolic phenotype in osteoarthritis

OBJECTIVE

Joint health is affected by local and systemic hormones. It is well accepted that systemic factors regulate the metabolism of joint tissues, and that substantial cross-talk between tissues actively contributes to homeostasis. In the current review, we try to define a subtype of osteoarthritis (OA), metabolic OA, which is dependent on an unhealthy phenotype.

METHODS

Peer-reviewed research articles and reviews were reviewed and summarized. Only literature readily available online, either by download or by purchase order, was included.

RESULTS

OA is the most common joint disease and is more common in women after menopause. OA is a disease that affects the whole joint, including cartilage, subchondral bone, synovium, tendons, and muscles. The clinical endpoints of OA are pain and joint space narrowing, which is characterized by cartilage erosion and subchondral sclerosis, suggesting that cartilage is a central tissue of joint health. Thus, the joint, more specifically the cartilage, may be considered a target of endocrine function in addition to the well-described traditional risk factors of disease initiation and progression such as long-term loading of the joint due to obesity. Metabolic syndrome affects a range of tissues and may in part be molecularly described as a dysregulation of cytokines, adipokines, and hormones (e.g., estrogen and thyroid hormone). Consequently, metabolic imbalance may both directly and indirectly influence joint health and cartilage turnover, altering the progression of diseases such as OA.

CONCLUSIONS

There is substantial evidence for a connection between metabolic health and development of OA. We propose that more focus be directed to understanding this connection to improve the management of menopausal health and associated comorbidities.

Value of biomarkers in osteoarthritis: current status and perspectives

Osteoarthritis affects the whole joint structure with progressive changes in cartilage, menisci, ligaments and subchondral bone, and synovial inflammation. Biomarkers are being developed to quantify joint remodelling and disease progression. This article was prepared following a working meeting of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis convened to discuss the value of biochemical markers of matrix metabolism in drug development in osteoarthritis. The best candidates are generally molecules or molecular fragments present in cartilage, bone or synovium and may be specific to one type of joint tissue or common to them all. Many currently investigated biomarkers are associated with collagen metabolism in cartilage or bone, or aggrecan metabolism in cartilage. Other biomarkers are related to non-collagenous proteins, inflammation and/or fibrosis. Biomarkers in osteoarthritis can be categorised using the burden of disease, investigative, prognostic, efficacy of intervention, diagnostic and safety classification. There are a number of promising candidates, notably urinary C-terminal telopeptide of collagen type II and serum cartilage oligomeric protein, although none is sufficiently discriminating to differentiate between individual patients and controls (diagnostic) or between patients with different disease severities (burden of disease), predict prognosis in individuals with or without osteoarthritis (prognostic) or perform so consistently that it could function as a surrogate outcome in clinical trials (efficacy of intervention). Future avenues for research include exploration of underlying mechanisms of disease and development of new biomarkers; technological development; the ‘omics’ (genomics, metabolomics, proteomics and lipidomics); design of aggregate scores combining a panel of biomarkers and/or imaging markers into single diagnostic algorithms; and investigation into the relationship between biomarkers and prognosis.

Inhalation therapy of calcitonin relieves osteoarthritis of the knee

This study was conducted to determine if nasal salmon calcitonin has additional beneficial effects on clinical symptoms, serum NO, IL-1β, matrix metalloproteinase 3, urinary C-terminal telopeptide type II collagen (CTX-II) levels and MRI findings in knee osteoarthritis (OA) when used concomitantly with exercise therapy. Fifty female patients with knee OA were randomized into two groups. The first group (n = 30) received 200 IU/day nasal salmon calcitonin and a home exercise program; the second group (n = 20) received a home exercise program for 6 months. Compared with baseline,while significant improvements were observed in visual analogue scale (VAS), WOMAC pain, physical function scores, 20-m walking time (P < 0.001) and WOMAC stiffness score (P = 0.041) in the first group, walking and resting VAS, and WOMAC physical function scores were improved (P = 0.029) in the second group after treatment. Significantly increased levels of serum NO and urinary CTX-II (P < 0.001) and significant improvements in the area of medial femoral condyle (P < 0.05) were noted only in the first group. There were significant differences in VAS activation values (P = 0.032) and NO levels (P < 0.001) in the favor of the first group. In conclusion, nasal salmon calcitonin may have possible chondroprotective effects besides its known effects on symptoms in patients with knee OA.

Serological investigation of the collagen degradation profile of patients with chronic obstructive pulmonary disease or idiopathic pulmonary fibrosis

In both chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), abnormally high collagen remodeling occurs within the lung tissue. Matrix metalloproteinase (MMP)-degraded type I, III, IV, V and VI collagen and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-degraded type III collagen were assessed in serum of patients diagnosed with mild COPD (n = 10) or IPF (n = 30), and healthy controls (n = 15). The collagen degradation markers C1M, C3M, C5M and C6M were significantly elevated in serum of both mild COPD and IPF patients, versus controls. C3A and C4M were only elevated in patients with mild COPD, compared with controls. The most reliable indicators of mild COPD versus controls were: C1M (area under the receiver-operating characteristics (AUROC = 0.94, P < 0.0001), C3M (AUROC = 0.95, P < 0.0001), and C5M (AUROC = 0.95, P < 0.0001). The most reliable markers for the diagnosis of IPF were achieved by C1M (AUROC = 0.90, P < 0.0001) and C3M (AUROC = 0.93, P < 0.0001). Collagen degradation was highly up-regulated in patients with IPF and mild COPD, indicating that degradation fragments of collagens are potential markers of pulmonary diseases. Interestingly, C4M and C3A were only elevated in patients with mild COPD, indicating that these markers could be used to distinguish between the two pathologies.

Serum cartilage metabolites as biomarkers of degenerative lumbar scoliosis

Several biomarkers have been used to evaluate osteoarthritis of the limb joints. Here we evaluated the use of serum cartilage metabolites as biomarkers for degenerative lumbar scoliosis (DLS). Fifty-two DLS patients with Cobb angle > 10° were compared with 19 control patients. Serum levels of hyaluronic acid (HA), keratan sulfate (KS), cartilage oligomeric matrix protein (COMP), collagen type II cleavage (C2C), and procollagen type II C-propeptide (CPII) were measured. Serum levels of KS (DLS 1.20 ± 0.44 µg/ml vs. control 0.98 ± 0.33 µg/ml), CPII (DLS 1905.1 ± 948.2 ng/ml vs. control 1223.6 ± 884.4 ng/ml), and C2C (DLS 219.1 ± 59.2 ng/ml vs. control 177.7 ± 71.7 ng/ml) were significantly higher in DLS. There were no significant differences in the levels of HA or COMP. There was a significant positive correlation between the Cobb angle and CPII in DLS. This is the first study to evaluate the cartilage biomarkers in DLS. The results suggest DLS patients have higher levels of type II collagen synthesis and degradation, indicated by elevated serum CPII and C2C, respectively. As type II collagen is a major component of collagens in the nucleus pulposus and facet joint cartilages, its enhanced turnover may be related to the development and progression of DLS.

Biological markers in osteoarthritis

Osteoarthritis (OA) is considered as a chronic disease with a long "silent" period. The diagnosis is generally based on clinical symptoms and radiographic changes. However X-ray has a poor sensitivity and a relatively large precision error that does not allow an early detection of OA or the monitoring of joint damage progression. The limitations of the tools that are currently available for OA assessment have been the impetus to identify specific biological markers that reflect quantitative and dynamic variations in joint remodeling. Research has focused on the structural components of cartilage matrix, especially type II collagen degradation markers. In spite of a significant increase of some markers in individuals with early stage of OA, the large overlap with control subjects indicates that the current biomarkers used alone have limited diagnostic potential. However, the combination of specific markers seems to improve the prediction of disease progression at the individual level. Several types of treatment have been investigated but the lack of medications with definitively demonstrated chondroprotective activity has limited the assessment of the potential role of biomarkers for monitoring patients' responses to the treatment of OA. In this review, we will use the BIPED classification that appeared in 2006 for OA markers to describe the potential usage of a given marker [5]. This article is part of a Special Issue entitled "Osteoarthritis".

Intelligent data analysis to model and understand live cell time-lapse sequences

BACKGROUND

One important aspect of cellular function, which is at the basis of tissue homeostasis, is the delivery of proteins to their correct destinations. Significant advances in live cell microscopy have allowed tracking of these pathways by following the dynamics of fluorescently labelled proteins in living cells.

OBJECTIVES

This paper explores intelligent data analysis techniques to model the dynamic behavior of proteins in living cells as well as to classify different experimental conditions.

METHODS

We use a combination of decision tree classification and hidden Markov models. In particular, we introduce a novel approach to "align" hidden Markov models so that hidden states from different models can be cross-compared.

RESULTS

Our models capture the dynamics of two experimental conditions accurately with a stable hidden state for control data and multiple (less stable) states for the experimental data recapitulating the behaviour of particle trajectories within live cell time-lapse data.

CONCLUSIONS

In addition to having successfully developed an automated framework for the classification of protein transport dynamics from live cell time-lapse data our model allows us to understand the dynamics of a complex trafficking pathway in living cells in culture.

Recent progress in understanding molecular mechanisms of cartilage degeneration during osteoarthritis

Osteoarthritis (OA) is a highly prevalent disease affecting more than 20% of American adults. Predispositions include joint injury, heredity, obesity, and aging. Biomechanical alterations are commonly involved. However, the molecular mechanisms of this disease are complex, and there is currently no effective disease-modifying treatment. The initiation and progression of OA subtypes is a complex process that at the molecular level probably involves many cell types, signaling pathways, and changes in extracellular matrix. Ex vivo studies with tissue derived from OA patients and in vivo studies with mutant mice have suggested that pathways involving receptor ligands such as TGF-β1, WNT3a, and Indian hedgehog; signaling molecules such as Smads, β-catenin, and HIF-2a; and peptidases such as MMP13 and ADAMTS4/5 are probably involved to some degree. This review focuses on molecular mechanisms of OA development related to recent findings.

Increased interleukin-1β gene expression in peripheral blood leukocytes is associated with increased pain and predicts risk for progression of symptomatic knee osteoarthritis

OBJECTIVE

To evaluate whether gene expression profiles could serve as biomarkers of symptomatic knee osteoarthritis (OA) by examining gene expression profiles in peripheral blood leukocytes (PBLs) from patients with OA compared with those from non-OA controls, and to determine whether candidate genomic biomarkers (PBL expression of inflammatory genes) predict an increased risk of disease progression in patients with symptomatic radiographic knee OA.

METHODS

Three independent cohorts of patients with knee OA and non-OA control subjects were studied. Two cohorts (a learning cohort and a validation cohort) were recruited at New York University Hospital for Joint Diseases (NYUHJD), and 1 cohort (a validation cohort) was recruited at Duke University Medical Center. PBL gene expression was assessed using Affymetrix microarray and was confirmed by quantitative polymerase chain reaction (qPCR). Radiographic progression at 2 years was assessed in 86 patients.

RESULTS

We identified 173 genes that were significantly up-regulated or down-regulated (≥1.5-fold change) in OA PBLs, at a false discovery rate of 5%. Cluster analysis revealed 2 distinct subgroups among the patients with OA: those in whom the expression of interleukin-1β (IL-1β) was increased ≥2-fold compared with controls, and those in whom the expression of IL-1β was comparable with that in controls. Overexpression of IL-1β in these OA subclasses was validated using qPCR in all 3 cohorts. Patients with the inflammatory "IL-1β signature" had higher pain scores and decreased function and were at higher risk of radiographic progression of OA.

CONCLUSION

PBLs from patients with symptomatic knee OA display a characteristic transcriptome profile. Moreover, increased expression of IL-1β identifies a subset of patients with OA who have increased pain and are at higher risk of radiographic progression of OA.

Biochemical markers of ongoing joint damage in rheumatoid arthritis--current and future applications, limitations and opportunities

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease associated with potentially debilitating joint inflammation, as well as altered skeletal bone metabolism and co-morbid conditions. Early diagnosis and aggressive treatment to control disease activity offers the highest likelihood of preserving function and preventing disability. Joint inflammation is characterized by synovitis, osteitis, and/or peri-articular osteopenia, often accompanied by development of subchondral bone erosions, as well as progressive joint space narrowing. Biochemical markers of joint cartilage and bone degradation may enable timely detection and assessment of ongoing joint damage, and their use in facilitating treatment strategies is under investigation. Early detection of joint damage may be assisted by the characterization of biochemical markers that identify patients whose joint damage is progressing rapidly and who are thus most in need of aggressive treatment, and that, alone or in combination, identify those individuals who are likely to respond best to a potential treatment, both in terms of limiting joint damage and relieving symptoms. The aims of this review are to describe currently available biochemical markers of joint metabolism in relation to the pathobiology of joint damage and systemic bone loss in RA; to assess the limitations of, and need for additional, novel biochemical markers in RA and other rheumatic diseases, and the strategies used for assay development; and to examine the feasibility of advancement of personalized health care using biochemical markers to select therapeutic agents to which a patient is most likely to respond.

Osteoarthritis subpopulations and implications for clinical trial design

Treatment guidelines for osteoarthritis have stressed the need for research on clinical predictors of response to different treatments. However, identifying such clinical predictors of response is less easy than it seems, and there is not a given classification of osteoarthritis subpopulations. This review article highlights the key methodical issues when analyzing and designing clinical studies to detect important subgroups with respect to treatment effect. In addition, we discuss the main osteoarthritis subpopulations and give examples of how specific treatment effects in these subpopulations have been assessed.

Cartilage degradation biomarkers predict efficacy of a novel, highly selective matrix metalloproteinase 13 inhibitor in a dog model of osteoarthritis: confirmation by multivariate analysis that modulation of type II collagen and aggrecan degradation peptides parallels pathologic changes

OBJECTIVE

To demonstrate that the novel highly selective matrix metalloproteinase 13 (MMP-13) inhibitor PF152 reduces joint lesions in adult dogs with osteoarthritis (OA) and decreases biomarkers of cartilage degradation.

METHODS

The potency and selectivity of PF152 were evaluated in vitro using 16 MMPs, TACE, and ADAMTS-4 and ADAMTS-5, as well as ex vivo in human cartilage explants. In vivo effects were evaluated at 3 concentrations in mature beagles with partial medial meniscectomy. Gross and histologic changes in the femorotibial joints were evaluated using various measures of cartilage degeneration. Biomarkers of cartilage turnover were examined in serum, urine, or synovial fluid. Results were analyzed individually and in combination using multivariate analysis.

RESULTS

The potent and selective MMP-13 inhibitor PF152 decreased human cartilage degradation ex vivo in a dose-dependent manner. PF152 treatment of dogs with OA reduced cartilage lesions and decreased biomarkers of type II collagen (type II collagen neoepitope) and aggrecan (peptides ending in ARGN or AGEG) degradation. The dose required for significant inhibition varied with the measure used, but multivariate analysis of 6 gross and histologic measures indicated that all doses differed significantly from vehicle but not from each other. Combined analysis of cartilage degradation markers showed similar results.

CONCLUSION

This highly selective MMP-13 inhibitor exhibits chondroprotective effects in mature animals. Biomarkers of cartilage degradation, when evaluated in combination, parallel the joint structural changes induced by the MMP-13 inhibitor. These data support the potential therapeutic value of selective MMP-13 inhibitors and the use of a set of appropriate biomarkers to predict efficacy in OA clinical trials.

Biochemical markers identify influences on bone and cartilage degradation in osteoarthritis--the effect of sex, Kellgren-Lawrence (KL) score, body mass index (BMI), oral salmon calcitonin (sCT) treatment and diurnal variation

Background

Osteoarthritis (OA) involves changes in both bone and cartilage. These processes might be associated under some circumstances. This study investigated correlations between bone and cartilage degradation in patients with OA as a function of sex, Kellgren-Lawrence (KL) score, Body Mass Index (BMI), oral salmon calcitonin (sCT) treatment and diurnal variation.

Methods

This study was a 2-week, double-blind, double-dummy, randomized study including 37 postmenopausal women and 36 men, aged 57-75 years, with painful knee OA, and a KL-score of I - III. Subjects were allocated to one of three treatment arms: 0.6 mg or 0.8 mg oral sCT, or placebo given twice-daily for 14 days. Correlations between gender, KL score, or BMI and the bone resorption marker, serum C-terminal telopeptide of collagen type I (CTX-I), or the cartilage degradation marker, urine C-terminal telopeptide of collagen type II (CTX-II) were investigated.

Results

At baseline, biomarkers indicated women with OA experienced higher bone and cartilage degradation than men. CTX-I levels were significantly higher, and CTX-II levels only marginally higher, in women than in men (p = 0.04 and p = 0.06, respectively). Increasing KL score was not correlated with bone resorption, but was significantly associated with the cartilage degradation CTX-II marker in both men and women (p = 0.007). BMI was significantly and negatively correlated to the bone resorption marker CTX-I, r = -0.40 (p = 0.002), but showed only a borderline positive correlation to CTX-II, r = 0.25 (p = 0.12). Before morning treatments on days 1 and 14, no correlation was seen between CTX-I and CTX-II in either the sCT or placebo group. However, oral sCT and food intake induced a clear correlation between these bone and cartilage degradation markers. Four hours after the first sCT dose on treatment days 1 and 14, a significant correlation (r = 0.71, p < 0.001) between changes in both CTX-I and CTX-II was seen. In the placebo group a weakly significant correlation between changes in both markers was found on day 1 (r = 0.49, p = 0.02), but not on day 14.

Conclusion

Bone resorption was higher in females than males, while cartilage degradation was correlated with increasing KL-score and only weakly associated with BMI. Bone and cartilage degradation were not correlated in untreated individuals, but dosing with oral sCT with or without food, and a mid-day meal, decreased bone and cartilage degradation and induced a correlation between both markers. Changes in bone and cartilage markers may aid in the identification of potential new treatment opportunities for OA.

Trial Registration

Clinical trial registration number (EUDRACT2006-005532-24 & NCT00486369)

Targeting subchondral bone for treating osteoarthritis: what is the evidence?

Over the past few decades, significant progress has been made with respect to new concepts about the pathogenesis of osteoarthritis (OA). This article summarises some of the knowledge we have today on the involvement of the subchondral bone in OA. It provides substantial evidence that changes in the metabolism of the subchondral bone are an integral part of the OA disease process and that these alterations are not merely secondary manifestations, but are part of a more active component of the disease. Thus, a strong rationale exists for therapeutic approaches that target subchondral bone resorption and/or formation, and data evaluating the drugs targeting bone remodelling raise the hope that new treatment options for OA may become available.

Genome-wide linkage analysis of quantitative biomarker traits of osteoarthritis in a large, multigenerational extended family

OBJECTIVE

The genetic contributions to the multifactorial disorder osteoarthritis (OA) have been increasingly recognized. The goal of the current study was to use OA-related biomarkers of severity and disease burden as quantitative traits to identify genetic susceptibility loci for OA.

METHODS

In a large multigenerational extended family (n = 350), we measured 5 OA-related biomarkers: hyaluronan (HA), cartilage oligomeric matrix protein (COMP), N-propeptide of type IIA collagen (PIIANP), C-propeptide of type II procollagen (CPII), and type II collagen neoepitope (C2C). Single-nucleotide polymorphism markers (n = 6,090) covering the whole genome were genotyped using the Illumina HumanLinkage-12 BeadChip. Variance components analysis, as implemented in the Sequential Oligogenic Linkage Analysis Routines, was used to estimate heritabilities of the quantitative traits and to calculate 2-point and multipoint logarithm of odds (LOD) scores using a polygenic model.

RESULTS

After adjusting for age and sex, we found that 4 of the 5 biomarkers exhibited significant heritability (PIIANP 0.57, HA 0.49, COMP 0.43, C2C 0.30; P < or = 0.01 for all). Fourteen of the 19 loci that had multipoint LOD scores of >1.5 were near to or overlapped with previously reported OA susceptibility loci. Four of these loci were identified by more than 1 biomarker. The maximum multipoint LOD scores for the heritable quantitative biomarker traits were 4.3 for PIIANP (chromosome 8p23.2), 3.2 for COMP (chromosome 8q11.1), 2.0 for HA (chromosome 6q16.3), and 2.0 for C2C (chromosome 5q31.2).

CONCLUSION

Herein, we report the first evidence of genetic susceptibility loci identified by OA-related biomarkers in an extended family. Our results demonstrate that serum concentrations of PIIANP, HA, COMP, and C2C have substantial heritable components, and using these biomarkers, several genetic loci potentially contributing to the genetic diversity of OA were identified.

First qualification study of serum biomarkers as indicators of total body burden of osteoarthritis

Background

Osteoarthritis (OA) is a debilitating chronic multijoint disease of global proportions. OA presence and severity is usually documented by x-ray imaging but whole body imaging is impractical due to radiation exposure, time and cost. Systemic (serum or urine) biomarkers offer a potential alternative method of quantifying total body burden of disease but no OA-related biomarker has ever been stringently qualified to determine the feasibility of this approach. The goal of this study was to evaluate the ability of three OA-related biomarkers to predict various forms or subspecies of OA and total body burden of disease.

Methodology/Principal Findings

Female participants (461) with clinical hand OA underwent radiography of hands, hips, knees and lumbar spine; x-rays were comprehensively scored for OA features of osteophyte and joint space narrowing. Three OA-related biomarkers, serum hyaluronan (sHA), cartilage oligomeric matrix protein (sCOMP), and urinary C-telopeptide of type II collagen (uCTX2), were measured by ELISA. sHA, sCOMP and uCTX2 correlated positively with total osteophyte burden in models accounting for demographics (age, weight, height): R² = 0.60, R² = 0.47, R² = 0.51 (all p<10⁻⁶); sCOMP correlated negatively with total joint space narrowing burden: R² = 0.69 (p<10⁻⁶). Biomarkers and demographics predicted 35–38% of variance in total burden of OA (total joint space narrowing or osteophyte). Joint size did not determine the contribution to the systemic biomarker concentration. Biomarker correlation with disease in the lumbar spine resembled that in the rest of the skeleton.

Conclusions/Significance

We have suspected that the correlation of systemic biomarkers with disease has been hampered by the inability to fully phenotype the burden of OA in a patient. These results confirm the hypothesis, revealed upon adequate patient phenotyping, that systemic joint tissue concentrations of several biomarkers can be quantitative indicators of specific subspecies of OA and of total body burden of disease.

The effect of oral salmon calcitonin delivered with 5-CNAC on bone and cartilage degradation in osteoarthritic patients: a 14-day randomized study

BACKGROUND

The aim of this study was to investigate the pharmacokinetic and pharmacodynamic parameters of oral salmon calcitonin (oSCT) administered over 14 days to men and women presenting with osteoarthritis (OA).

MATERIALS AND METHODS

The study was a phase-I, 2-week, placebo-controlled, double-blind, double-dummy, randomized, gender-stratified study including 73 subjects aged 57-75 years. Patients had painful OA with a Kellgren and Lawrence index score of I-III. Treatment allocations were; 0.6 mg, 0.8 mg of oSCT, or placebo. Treatment was given twice daily for 14 days. The morning dose was administered between 07:00 and 08:00 at least 30 min before breakfast. The second dose was administered 30 min before evening dinner. On treatment day 1 and 14, the morning dose was followed by 5h of fasting, and blood samples and urine were collected immediately prior to dosing and according to the protocol. Study parameters were: plasma sCT levels, bone resorption by CTX-I (serum C-terminal telopeptide of collagen type I), bone formation by osteocalcin (serum OC), and cartilage degradation by CTX-II (urine C-terminal telopeptide of collagen type II) (clinicaltrials.gov identifier: NCT00486369).

RESULTS

Doses of 0.8 mg compared with 0.6 mg produced significantly higher C(max) and AUC(0-4 hrs), of calcitonin, P=0.03. This resulted in significant reductions in CTX-I and CTX-II, [P<0.0001; P=0.007]. No differences were observed between baseline and follow-up at day 14 in pharmacokinetic and pharmacodynamic parameters. Gender had no observable influence on results.

CONCLUSIONS

oSCT given twice daily with a pre-dinner and morning fasting dosing resulted in reductions in markers of bone resorption and cartilage degradation.

Whole-body bone scintigraphy provides a measure of the total-body burden of osteoarthritis for the purpose of systemic biomarker validation

OBJECTIVE

To evaluate the association of serum and synovial fluid cartilage oligomeric matrix protein (COMP) with systemic and local measures of osteoarthritis (OA) activity by bone scintigraphy.

METHODS

Samples of serum and knee joint synovial fluid (275 knees) were obtained from 159 patients with symptomatic OA of at least 1 knee. Bone scintigraphy using (99m)Tc-labeled methylene diphosphonate was performed, and early-phase knee scans and late-phase whole-body bone scans of 15 additional joint sites were scored semiquantitatively. To control for within-subject correlations of knee data, generalized linear modeling was used in the correlation of the bone scan scores with the COMP levels. Principal components analysis was used to explore the contribution of each joint site to the variance in serum COMP levels.

RESULTS

The correlation between synovial fluid and serum COMP levels was significant (r = 0.206, P = 0.006). Synovial fluid COMP levels correlated most strongly with the early-phase knee bone scan scores (P = 0.0003), even after adjustment for OA severity according to the late-phase bone scan scores (P = 0.015), as well as synovial fluid volumes (P < 0.0001). Serum COMP levels correlated with the total-body bone scan scores (r = 0.188, P = 0.018) and with a factor composed of the bone scan scores in the shoulders, spine, lateral knees, and sacroiliac joints (P = 0.0004).

CONCLUSION

Synovial fluid COMP levels correlated strongly with 2 indicators of knee joint inflammation: early-phase bone scintigraphic findings and synovial fluid volume. Serum COMP levels correlated with total-body joint disease severity as determined by late-phase bone scintigraphy, supporting the hypothesis that whole-body bone scintigraphy is a means of quantifying the total-body burden of OA for systemic biomarker validation.

Identification of progressors in osteoarthritis by combining biochemical and MRI-based markers

Introduction

At present, no disease-modifying osteoarthritis drugs (DMOADS) are approved by the FDA (US Food and Drug Administration); possibly partly due to inadequate trial design since efficacy demonstration requires disease progression in the placebo group. We investigated whether combinations of biochemical and magnetic resonance imaging (MRI)-based markers provided effective diagnostic and prognostic tools for identifying subjects with high risk of progression. Specifically, we investigated aggregate cartilage longevity markers combining markers of breakdown, quantity, and quality.

Methods

The study included healthy individuals and subjects with radiographic osteoarthritis. In total, 159 subjects (48% female, age 56.0 ± 15.9 years, body mass index 26.1 ± 4.2 kg/m²) were recruited. At baseline and after 21 months, biochemical (urinary collagen type II C-telopeptide fragment, CTX-II) and MRI-based markers were quantified. MRI markers included cartilage volume, thickness, area, roughness, homogeneity, and curvature in the medial tibio-femoral compartment. Joint space width was measured from radiographs and at 21 months to assess progression of joint damage.

Results

Cartilage roughness had the highest diagnostic accuracy quantified as the area under the receiver-operator characteristics curve (AUC) of 0.80 (95% confidence interval: 0.69 to 0.91) among the individual markers (higher than all others, P < 0.05) to distinguish subjects with radiographic osteoarthritis from healthy controls. Diagnostically, cartilage longevity scored AUC 0.84 (0.77 to 0.92, higher than roughness: P = 0.03). For prediction of longitudinal radiographic progression based on baseline marker values, the individual prognostic marker with highest AUC was homogeneity at 0.71 (0.56 to 0.81). Prognostically, cartilage longevity scored AUC 0.77 (0.62 to 0.90, borderline higher than homogeneity: P = 0.12). When comparing patients in the highest quartile for the longevity score to lowest quartile, the odds ratio of progression was 20.0 (95% confidence interval: 6.4 to 62.1).

Conclusions

Combination of biochemical and MRI-based biomarkers improved diagnosis and prognosis of knee osteoarthritis and may be useful to select high-risk patients for inclusion in DMOAD clinical trials.

The role of plasma cytokine levels, CRP and Selenoprotein S gene variation in OA

OBJECTIVE

Investigating the association between plasma levels of cytokines and chemokines, Selenoprotein S (SELS) gene variation and osteoarthritis (OA) subtypes.

METHODS

The genetics of osteoarthritis and progression (GARP) study consists of 191 sibling pairs with symptomatic OA at multiple joint sites. We have measured plasma levels of 17 cytokines and chemokines and genetic variation at the SELS gene.

RESULTS

Nine out of 17 serum markers could be assessed quantitatively, whereas eight markers were assessed qualitatively. Principal component analysis (PCA) on the quantitatively assessed markers and serum high sensitive C-reactive protein (S-HsCRP) revealed that three components underlie 61% of the total plasma variation. Three single nucleotide polymorphisms (SNPs) in the SELS gene revealed four common haplotypes, one of which, GAG (frequency 3.5%) showed significant association to an anti-inflammatory (P=0.019) and acute phase related (P=0.036) component. OA subtype analysis showed that one component (mainly representing chemokine variation) was significantly associated to hand OA and disc degeneration (P=0.029 and P=0.010 respectively) as well as a physical component score (PCS) (P=0.042). The CRP related component also showed a strong association to the PCS (P=0.007). SELS haplotypes showed no association to OA subtypes in the GARP study.

CONCLUSION

Genetic variation in the SELS gene associates to components representing inflammatory signaling. Another component, representing chemokine variation, showed association to hand OA and disc degeneration in the GARP study indicating chemokines may contribute to OA pathogenesis.

Effect of glucosamine sulphate on joint space narrowing, pain and function in patients with hip osteoarthritis; subgroup analyses of a randomized controlled trial

OBJECTIVE

Recently we reported that glucosamine sulphate (GS) did not have an effect on the symptoms and progression of primary care patients with hip osteoarthritis (OA). The aim of this present study was to investigate whether there are subgroups of patients with hip OA for whom GS might be an effective therapy.

METHOD

We randomized 222 patients with hip OA that met one of the American College of Rheumatology criteria to either 1500 mg of oral GS or placebo once daily for 2 years. Subgroup analyses were predefined for radiographic severity (Kellgren & Lawrence (KL)=1 vs >or=2) and for type of OA (localised vs generalised). Additional exploratory subgroup analyses focused on groups based on pain level, pain medication use, baseline joint space width (JSW), and concomitant knee OA at baseline. Primary outcome measures were Western Ontario MacMaster Universities (WOMAC) pain and function scores over 24 months, and joint space narrowing (JSN) after 24 months.

RESULTS

In the predefined subgroups based on radiographic severity and type of OA, the outcomes WOMAC pain, function and JSN were similar for the GS and placebo group.

CONCLUSION

GS was not significantly better than placebo in reducing symptoms and progression of hip OA in subgroups of patients.

Increased urinary excretion of C-telopeptides of type II collagen (CTX-II) predicts cartilage loss over 21 months by MRI

OBJECTIVE

Osteoarthritis (OA) is characterized by increased bone and cartilage metabolism leading to joint damage. The urinary excretion of C-telopeptides of type II collagen (CTX-II) has earlier predicted progression in radiographic OA (ROA)--useful for participant selection in clinical studies of potential disease modifying OA drugs (DMOADs). We investigated the longitudinal interrelationship between CTX-II and knee cartilage volume quantified from magnetic resonance imaging (MRI).

METHODS

We followed 158 subjects [48% females, 36 with knee ROA at baseline (BL)] for 21 months. The Kellgren and Lawrence (KL) index and joint space width were assessed from radiographs (acquired load-bearing, semi-flexed). MRI scans were acquired from a 0.18 T Esaote scanner (40 degrees flip angle (FA), TR 50 ms, TE 16 ms, scan time 10 min, resolution 0.7 mm x 0.7 mm x 0.8 mm) and medial tibial and femoral cartilage volume was quantified. Radiographs and MRI were acquired at BL and follow-up. Fasting morning urine samples (second void) were collected for BL CTX-II measurement.

RESULTS

CTX-II was 56% higher in ROA subjects (P=0.0001). In addition, elevated BL CTX-II was associated with radiographic progression (by KL or joint space narrowing) although not statistically significant. Contrarily, elevated BL CTX-II predicted longitudinal cartilage loss by MRI (middle/high tertiles had odds ratios 4.0/3.9, P<0.01) corresponding to 3.1% increased yearly cartilage loss.

CONCLUSION

Prognostic markers in study selection criteria must ensure that placebo-treated participants progress to enable efficacy demonstration. And efficacy markers must allow progression detection within the study period. Our results support applying CTX-II for selection of high risk subjects and applying the fully automatic MRI-based framework for quantification of cartilage loss.

Serum protein signatures detect early radiographic osteoarthritis

OBJECTIVE

To test the hypothesis that early knee and hand osteoarthritis (OA) development is characterized by detectable changes in serum proteins relevant to inflammation, cell growth, activation, and metabolism several years before OA becomes radiographically evident.

METHODS

Using microarray platforms that simultaneously test 169 proteins relevant to inflammation, cell growth, activation and metabolism, we conducted a case-control study nested within the Baltimore Longitudinal Study of Aging (BLSA). Subjects included 22 incident cases of OA and 66 age-, sex- and body mass index (BMI)-matched controls. Serum samples tested were obtained at the time of radiographic classification as either case or control, and up to 10 years earlier at a time when all participants were free of radiographic OA. Proteins with mean signal intensities fourfold higher than background were compared between cases and controls using multivariate techniques.

RESULTS

Sixteen proteins were different between OA cases compared to controls. Four of these proteins [matrix metalloproteinase (MMP)-7, interleukin (IL)-15, plasminogen activator inhibitor (PAI)-1 and soluble vascular adhesion protein (sVAP)-1] were already different in samples obtained 10 years before radiographic classification and remained different at the time of diagnosis. Six additional proteins were only associated with subsequent OA development and not with established OA.

CONCLUSIONS

Changes in serum proteins implicated in matrix degradation, cell activation, inflammation and bone collagen degradation products accompany early OA development and can precede radiographic detection by several years.

Biomarkers in the development of novel disease-modifying therapies for osteoarthritis

Identification and utilization of biomarkers is vitally important for the successful development of disease-modifying osteoarthritis drugs. Biochemical and imaging platforms hold great promise to deliver such biomarkers. Studies indicate a marked increase in biochemical products arising from the breakdown and biosynthesis of collagen, extracellular matrix and bone in osteoarthritis. These molecules have been associated with disease severity and may also have prognostic value as indicators of disease progression. However, issues including biological variability and lack of tissue specificity currently hinder the utility of these molecular markers in drug development. Imaging technologies hold great potential for sensitive and accurate measurement of disease-related structural damage. Drawbacks, including expense, need for validation and limited accessibility also limit the utility of these technologies. In this article, the potential value and challenges in developing and utilizing biomarkers in disease-modifying osteoarthritis drug development will be discussed.

Tibolone inhibits bone resorption without secondary positive effects on cartilage degradation

Background

Osteoarthritis is associated with increased bone resorption and increased cartilage degradation in the subchondral bone and joint. The objective of the present study was to determine whether Tibolone, a synthetic steroid with estrogenic, androgenic, and progestogenic properties, would have similar dual actions on both bone and cartilage turnover, as reported previously with some SERMS and HRT.

Methods

This study was a secondary analysis of ninety-one healthy postmenopausal women aged 52–75 yrs entered a 2-yr double blind, randomized, placebo-controlled study of treatment with either 1.25 mg/day (n = 36), or 2.5 mg/day Tibolone (n = 35), or placebo (n = 20), (J Clin Endocrinol Metab. 1996 Jul;81(7):2419–22) Second void morning urine samples were collected at baseline, and at 3, 6, 12, and 24 months. Urine CrossLaps^® ELISA (CTX-I) and Urine CartiLaps^® ELISA (CTX-II) was investigated as markers of bone resorption and cartilage degradation, respectively.

Results

Tibolone significantly (P < 0.001) suppressed bone resorption by approximately 60%. In contrast, no effect was observed on cartilage degradation.

Conclusion

These data suggest uncoupling of the bone and cartilage effects of the synthetic steroid, Tibolone. Bone resorption was significantly decreased, whereas cartilage degradation was unchanged. These effects are in contrast to those observed some SERMs with effects on both bone and cartilage degradation. These effects may in part be described by the complicated pharmacology of Tibolone on testosterone, estrogen and progesterone receptors.