Differences in biomarkers of type II collagen in atrophic and hypertrophic osteoarthritis of the hip: implications for the differing pathobiologies

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.

Are Bone Mineral Density and Fractures Related to the Incidence and Progression of Radiographic Osteoarthritis of the Knee, Hip, and Hand in Elderly Men and Women? The Rotterdam Study

OBJECTIVE

To examine the longitudinal relationship between bone mineral density (BMD) and the incidence and progression of knee, hip, and hand osteoarthritis (OA), and to examine the relationship between prevalent vertebral and nonvertebral fractures and the incidence and progression of OA in elderly men and women in the Rotterdam Study.

METHODS

Age- and sex-specific quartiles of baseline femoral neck BMD data were constructed for 4,154 subjects. Radiographs were scored for incidence and progression of knee and hip OA, and for incidence of hand OA. Prevalent vertebral fractures were scored using the McCloskey/Kanis method, and prevalent nonvertebral fractures were reported by baseline interview.

RESULTS

Subjects in the highest quartile of femoral neck BMD had an increased risk of incident radiographic knee OA (ROA) (odds ratio [OR] 1.58 [95% confidence interval (95% CI) 1.14-2.18]), and an increased risk of incident hip ROA (OR 1.57 [95% CI 1.06-2.32]), compared to the lowest quartile. No significant relationship was found between high femoral neck BMD and progression of knee or hip ROA or the incidence of hand ROA. Prevalent vertebral and nonvertebral fractures were not related to an increase in the incidence or progression of knee or hip ROA. However, vertebral fractures were associated with incident hand ROA (OR 1.74 [95% CI 1.02-2.98]).

CONCLUSION

Results from the present study confirm earlier findings and thus provide strong evidence that high femoral neck BMD is a prognostic risk factor for the development of knee and hip ROA. Vertebral fractures were found to be a risk factor for incident hand ROA.

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

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

Presence of IL-17 in synovial fluid identifies a potential inflammatory osteoarthritic phenotype

Purpose

Osteoarthritis (OA) is a common and heterogeneous arthritic disorder. Patients suffer pain and their joints are characterized by articular cartilage loss and osteophyte formation. Risk factors for OA include age and obesity with inflammation identified as a key mediator of disease pathogenesis. Interleukin-17A (IL-17) is a pro-inflammatory cytokine that has been implicated in inflammatory diseases such as rheumatoid arthritis. IL-17 can upregulate expression of inflammatory cytokines and adipocytokines. The aim of this study was to evaluate IL-17 levels in the synovial fluid of patients with end-stage knee and hip OA in relation to inflammation- and pain-related cytokines and adipocytokines in synovial fluid and serum, and clinical and radiographic disease parameters.

Methods

This is a cross-sectional study of 152 patients undergoing total hip and knee arthroplasty for OA. IL-17, IL-6, leptin, adiponectin, visfatin, resistin, C-C Motif Chemokine Ligand 2 (CCL2), C-C Motif Chemokine Ligand 7 (CCL7) and nerve growth factor (NGF) protein levels were measured in synovial fluid and serum using enzyme-linked immunosorbent assay (ELISA). Baseline characteristics included age, sex, body mass index, co-morbidities, pain and function, and radiographic analyses (OA features, K&L grade, minimal joint space width).

Results

14 patients (9.2%) had detectable IL-17 in synovial fluid. These patients had significantly higher median concentrations of IL-6, leptin, resistin, CCL7 and NGF. Osteophytes, sclerosis and minimum joint space width were significantly reduced in patients with detectable IL-17 in synovial fluid. No differences were found in pain, function and comorbidities. IL-17 concentrations in synovial fluid and serum were moderately correlated (r = 0.482).

Conclusion

The presence of IL-17 in the synovial fluid therefore identifies a substantial subset of primary end-stage OA patients with distinct biological and clinical features. Stratification of patients on the basis of IL-17 may identify those responsive to therapeutic targeting.

Clinico-radiological diagnosis and grading of rapidly progressive osteoarthritis of the hip

Due to the current lack of standard definitions for rapidly progressive osteoarthritis of the hip (RPOH) in the literature, this observational study aimed to describe new diagnostic criteria and a grading system for the disease.From a consecutive series of patients undergoing total hip replacement, 2 groups were selected: 1 with RPOH and 1 with primary hip osteoarthritis (POH), and their clinical, paraclinical, and demographic data were compared. The newly proposed clinico-radiological diagnostic criteria are based on characteristics of pain, joint mobility, and radiological assessment. The radiological grading system's inter- and intraobserver reliability was assessed through serial evaluations by 2 blinded reviewers.From the total 863 cases, 82 cases (9.5%) of RPOH were identified and compared with 107 cases of POH. Mean age and disease bilaterality were similar, with a predominance of female patients in the RPOH group (P = 0.03). There were significant differences between the 2 groups in disease onset and aggravation, and intraoperative blood loss. The grading system showed significant inter- and intraobserver agreement (weighted kappa 0.93, and 0.89).Our study presents distinctive, easily recognizable clinico-radiological characteristics of RPOH and confirmed the inter- and intraobserver reliability of the newly proposed grading system.

What is the utility of biomarkers for assessing the pathophysiology of hip osteoarthritis? A systematic review

BACKGROUND

Innovations in biologics offer great promise in the treatment of patients with orthopaedic conditions and in advancing our ability to monitor underlying disease pathophysiology. Our understanding of the pathophysiology of hip osteoarthritis (OA) has improved significantly in the last decade. Femoroacetabular impingement (FAI) and hip dysplasia are increasingly recognized and treated as forms of prearthritic hip disease, yet the inability of radiographic and MR imaging to identify patients before the onset of irreversible articular cartilage injury limits their use for early diagnosis and treatment of patients with these conditions. Molecular biomarkers, as objectively measureable indicators of the pathophysiology of hip OA, have the potential to improve diagnosis, disease staging, and prognosis of hip OA and prearthritic hip disease. Although research into molecular biomarkers of hip OA has been conducted, investigations in prearthritic hip disease have only recently begun.

QUESTIONS/PURPOSES

The purpose of our review was to assess the use of molecular biomarkers in the pathophysiology of hip OA, including (1) diagnosis; (2) disease staging; and (3) prognosis. We additionally aimed to summarize the available literature investigating the use of biomarkers in (4) prearthritic hip disease, including FAI and hip dysplasia.

METHODS

We conducted a systematic review of molecular biomarkers associated with hip OA or prearthritic hip disease by searching four major electronic databases for keywords "hip", "osteoarthritis", "biomarker", and all synonyms. The search terms "femoroacetabular impingement" and "hip dysplasia" were also included. The biologic source of biomarkers was limited to serum, plasma, urine, and synovial fluid. The literature search yielded a total of 2740 results. Forty studies met all criteria and were included in our review. Studies were categorized regarding their relevance to (1) diagnosis; (2) disease staging; (3) prognosis; and/or (4) prearthritic hip disease.

RESULTS

Biomarker studies were characterized as relevant to diagnosis (16 studies), disease staging (15 studies), prognosis (11 studies), and prearthritic hip disease (three studies). Sixteen different biomarkers demonstrated associations relevant to the diagnosis of hip OA, 16 biomarkers demonstrated similar associations for disease staging, and six for prognosis. Six biomarkers seemed to be the most promising, demonstrating associations with hip OA in multiple studies, including: urinary level of type II collagen telopeptide (n = 5 studies), serum cartilage oligomeric protein (n = 4 studies), and serum C-reactive protein (n = 4 studies). Only three studies investigated the role of biomarkers in prearthritic hip disease, including two in FAI and one in unspecified etiology of pain. There were no studies about biomarkers in hip dysplasia.

CONCLUSIONS

Molecular biomarkers are increasingly investigated for their use in evaluating the pathophysiology of hip OA, but less so for prearthritic hip disease. Several biomarkers have demonstrated significant associations with hip OA across multiple studies. Further validation of these biomarkers is needed to assess their clinical use and potential application to prearthritic hip disease.

Distinct subtypes of knee osteoarthritis: data from the Osteoarthritis Initiative

OBJECTIVE

OA is suspected to be a collection of distinct subtypes, each with different aetiology and clinical characteristics. We aimed to explore the existence of different subtypes of knee OA, using cluster analysis of the data of the OA Initiative.

METHODS

We used latent class cluster analysis (LCA) to cluster baseline data of 518 subjects of the OA Initiative progression cohort. Data included radiographic scores of OA features per compartment, regional quantitative MRI measures of cartilage quantity and denuded bone, and self-reported clinical scores on knee symptoms. To ensure that the clusters were found independently of OA severity, the LCA model was corrected with a measure of OA severity. The resulting clusters were compared with respect to the presence of risk factors and progression.

RESULTS

LCA resulted in four clusters containing 47%, 27%, 15% and 12% of the subjects. Clusters 1, 2 and 4 showed OA features at the medial compartment, while cluster 3 only showed lateral OA features. Clusters 3 and 4 showed severe increases in areas of denuded bone, whereas no denuded bone was present in cluster 1. Prevalence of OA progression over 24 months was highest in clusters 3 and 4 and lowest in cluster 1. The clusters also differed significantly in BMI, knee alignment and prevalence of reported trauma.

CONCLUSION

LCA confirmed the existence of distinct subtypes of knee OA with clear differences in structural degradation and symptoms. The fact that subtypes also differed in risk factors suggests that different causes lead to different types of knee OA.

Radiographic evaluation of posttraumatic osteoarthritis of the ankle: the Kellgren-Lawrence scale is reliable and correlates with clinical symptoms

OBJECTIVE

To assess reliability and construct validity of the Kellgren-Lawrence (K&L) scale in posttraumatic ankle osteoarthritis (OA); additionally evaluate the validity of including tibiotalar tilting in the scale.

METHOD

One-hundred and fifty ankle radiographs (75 patients, unilateral malleolar fractures) evaluated at average of 18 years after surgery. American Orthopaedic Foot & Ankle Society (AOFAS) ankle-hindfoot (HF) score and pain (visual analog scale) were recorded. Grading of OA according to K&L criteria and identification of OA features was performed on standardized radiographs by four physicians. Minimal joint space width, sclerosis, and talar tilt angle were quantified by digital measurements. A modified K&L scale including talar tilting is presented. Validity of original and modified scale was evaluated and expressed as ability to (1) Identify those with clinical symptoms of ankle OA; and (2) Distinguish between different degrees of fracture severity.

RESULTS

Inter- and intra-observer reliability of OA assessment according to K&L were good (ICC 0.61 and 0.75). Original and modified K&L grades significantly increased with decreasing AOFAS ankle-HF scores and greater pain. A talar-tilt angle > 2° compared with ≤ 2° in grade 3 was associated with significantly higher pain levels (VAS pain 4.2 vs 1.4, respectively; mean difference 2.8, 95% CI 0.5-5.1). More severe fracture patterns at time of surgery were more often in patients with the highest K&L grades.

CONCLUSIONS

The K&L scale is a valid and reliable radiographic grading system for assessment of ankle OA. Inclusion of the talar tilt angle might allow for better differentiation with respect to clinical outcomes.

Prevalence of radiographic hip osteoarthritis is increased in high bone mass

OBJECTIVE

Epidemiological studies have shown an association between increased bone mineral density (BMD) and osteoarthritis (OA), but whether this represents cause or effect remains unclear. In this study, we used a novel approach to investigate this question, determining whether individuals with High Bone Mass (HBM) have a higher prevalence of radiographic hip OA compared with controls.

DESIGN

HBM cases came from the UK-based HBM study: HBM was defined by BMD Z-score. Unaffected relatives of index cases were recruited as family controls. Age-stratified random sampling was used to select further population controls from the Chingford and Hertfordshire cohort studies. Pelvic radiographs were pooled and assessed by a single observer blinded to case-control status. Analyses used logistic regression, adjusted for age, gender and body mass index (BMI).

RESULTS

530 HBM hips in 272 cases (mean age 62.9 years, 74% female) and 1702 control hips in 863 controls (mean age 64.8 years, 84% female) were analysed. The prevalence of radiographic OA, defined as Croft score ≥3, was higher in cases compared with controls (20.0% vs 13.6%), with adjusted odds ratio (OR) [95% CI] 1.52 [1.09, 2.11], P = 0.013. Osteophytes (OR 2.12 [1.61, 2.79], P < 0.001) and subchondral sclerosis (OR 2.78 [1.49, 5.18], P = 0.001) were more prevalent in cases. However, no difference in the prevalence of joint space narrowing (JSN) was seen (OR 0.97 [0.72, 1.33], P = 0.869).

CONCLUSIONS

An increased prevalence of radiographic hip OA and osteophytosis was observed in HBM cases compared with controls, in keeping with a positive association between HBM and OA and suggesting that OA in HBM has a hypertrophic phenotype.

Early effect of hyaluronic acid intra-articular injections on serum and urine biomarkers in patients with knee osteoarthritis: An open-label observational prospective study

The aim of the study was to investigate the effect of hyaluronic acid (HA) intra articular injections (IA) on osteoarthritis (OA) biomarkers in patients with knee OA. Prospective open label study. Fifty-one patients with unilateral symptomatic K-OA received IA injections of 2mL of HA on days (D) 1, 7, 14 and were followed 3 months. At D-15 patients were examined and X-rays performed, to exclude patients with bilateral K-OA, or those with more than three symptomatic OA joints. From 15 days (D-15) before the first injection to D90 concomitant therapies were unchanged. Walking pain (WP) on VAS was obtained at each visit. Urine (U) and serum (S) samples were obtained at D-15, D1, D30, and D90. S-C2C, S-Cartilage oligomeric matrix protein, S-HA, S-CS 846 epitope, S-type II collagen propeptide, and U-type II collagen C telopeptide (U-CTX II/creatinin) were assayed. Predictive factors of response were analyzed using logistic regression. Correlations between variables were obtained using Spearman test. Forty-five patients were analyzed. Between D-15 and D1 there was no difference for any biomarkers At D1, WP (SD) was correlated with U-CTX II/creat (p = 0.006). Between D1 and D90: U-CTX II/creat decreased significantly. After adjustment for confounding variables there was a significant correlation between clinical response and U-CTX II/creat variation. U-CTX II and S-HA at baseline were independently predictive of clinical response. This study showed that 90 days after HA IA injections, U-CTX II levels significantly decrease compared to baseline, suggesting a slowdown of type II collagen degradation.

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.

Computed tomography of subchondral bone and osteophytes in hip osteoarthritis: the shape of things to come?

Bone is a fundamental component of the disordered joint homeostasis seen in osteoarthritis, a disease that has been primarily characterized by the breakdown of articular cartilage accompanied by local bone changes and a limited degree of joint inflammation. In this review we consider the role of computed tomography imaging and computational analysis in osteoarthritis research, focusing on subchondral bone and osteophytes in the hip. We relate what is already known in this area to what could be explored through this approach in the future in relation to both clinical research trials and the underlying cellular and molecular science of osteoarthritis. We also consider how this area of research could impact on our understanding of the genetics of osteoarthritis.

Associations of horse age, joint type, and osteochondral injury with serum and synovial fluid concentrations of type II collagen biomarkers in Thoroughbreds

OBJECTIVE

To determine the effects of horse age, osteochondral injury, and joint type on a synthesis biomarker and 3 degradative biomarkers of type II collagen in Thoroughbreds.

ANIMALS

Healthy rested adult (3- to 12-year-old) Thoroughbreds (n = 19), yearling (1- to 2-year-old) Thoroughbreds (40), and Thoroughbred racehorses (2 to 7 years old) undergoing arthroscopic surgery for removal of osteochondral fragments that resulted from training or racing (41).

PROCEDURES

Samples of blood and metacarpophalangeal, metatarsophalangeal, or carpal joint synovial fluid (SF) were collected from all horses. Commercially available assays were used to analyze SF and serum concentrations of type II collagen biomarkers of synthesis (carboxy propeptide of type II collagen [CPII]) and degradation (cross-linked C-telopeptide fragments of type II collagen [CTX II], neoepitope generated by collagenase cleavage of type I and II collagen [C1,2C], and neoepitope generated by collagenase cleavage of type II collagen [C2C]).

RESULTS

Osteochondral injury affected concentrations of CPII, CTX II, C1,2C, and C2C in SF, serum, or both, compared with concentrations in healthy adult horses. Compared with adult horses, yearling horses had increased SF or serum concentrations of degradative biomarkers (CTX II, C1,2C, and C2C). Concentrations were higher in carpal than metacarpophalangeal or metatarsophalangeal joints for all biomarkers in osteochondral-injured horses. Variable differences in SF concentrations between joint types were detected in healthy adult and yearling horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Horse age, osteochondral injury, and joint type all significantly affected type II collagen biomarker concentrations in SF and serum of Thoroughbreds.

Subchondral bone microstructural damage by increased remodelling aggravates experimental osteoarthritis preceded by osteoporosis

Introduction

Osteoporosis (OP) increases cartilage damage in a combined rabbit model of OP and osteoarthritis (OA). Accordingly, we assessed whether microstructure impairment at subchondral bone aggravates cartilage damage in this experimental model.

Methods

OP was induced in 20 female rabbits, by ovariectomy and intramuscular injections of methylprednisolone hemisuccinate for four weeks. Ten healthy animals were used as controls. At week 7, OA was surgically induced in left knees of all rabbits. At 22 weeks, after sacrifice, microstructure parameters were assessed by micro-computed tomography, and osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), alkaline phosphatase (ALP) and metalloproteinase 9 (MMP9) protein expressions were evaluated by Western Blot at subchondral bone. In addition, cartilage damage was estimated using the histopathological Mankin score. Mann-Whitney and Spearman statistical tests were performed as appropriate, using SPSS software v 11.0. Significant difference was established at P < 0.05.

Results

Subchondral bone area/tissue area, trabecular thickness and polar moment of inertia were diminished in OPOA knees compared with control or OA knees (P < 0.05). A decrease of plate thickness, ALP expression and OPG/RANKL ratio as well as an increased fractal dimension and MMP9 expression occurred at subchondral bone of OA, OP and OPOA knees vs. controls (P < 0.05). In addition, the severity of cartilage damage was increased in OPOA knees vs. controls (P < 0.05). Remarkably, good correlations were observed between structural and remodelling parameters at subchondral bone, and furthermore, between subchondral structural parameters and cartilage Mankin score.

Conclusions

Microstructure impairment at subchondral bone associated with an increased remodelling aggravated cartilage damage in OA rabbits with previous OP. Our results suggest that an increased subchondral bone resorption may account for the exacerbation of cartilage damage when early OA and OP coexist simultaneously in same individuals.

Cartilage biomarkers in hemodialysis patients and the effect of beta2-microglobulin on articular chondrocytes

OBJECTIVE

Dialysis-related amyloidosis (DRA) is a severe complication of maintenance hemodialysis (HD). Given the predominant deposition of beta(2)-microglobulin (beta2m) fibrils on articular cartilage in early DRA, we investigated the significance of beta2m and its relationship to distinct cartilage biomarkers in early DRA diagnosis in HD patients. Furthermore, we assessed the effects of beta2m on articular chondrocytes in vitro.

METHODS

Serum samples from 133 patients were collected before and after HD. Type II collagen cleavage product (C2C), procollagen II c-propeptide (CPII), aggrecan chondroitin sulfate 846 epitope (CS-486) and cartilage oligomeric matrix protein (COMP) levels were determined by enzyme-linked immunosorbent assay. Primary bovine articular chondrocytes were cultured as monolayers and incubated with beta2m at 1.5mg/l and 20mg/l. Cartilage glucosaminoglycan synthesis was measured by [(35)S]sulfate incorporation. mRNA expression of interleukin (IL)-1beta, matrix metalloproteinases (MMPs)-3 and -9 was measured by reverse-transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Incubation with beta2m at 20mg/l significantly decreased matrix biosynthesis. PCR analysis revealed an increase of IL-1beta, as well as MMPs-3 and -9 on the mRNA level. C2C/CPII, CS-486 and COMP levels were increased only in a subset of patients without a significant correlation with beta2m concentrations. A subgroup analysis elucidated an increase in type II collagen degradation during the first years of HD, as shown by the elevation of C2C/CPII ratio.

CONCLUSION

beta2m exerted anti-anabolic effects on articular chondrocytes in vitro and might be involved in cartilage degradation in HD patients. beta2m serum levels, however, did not reflect cartilage degradation in DRA. The assessment of C2C/CPII, CS-486 or COMP concentrations apparently has minor relevance in DRA diagnosis in HD patients. However, the increased type II collagen breakdown within 5 years after HD onset possibly mirrors the early stages of DRA. Thus, the C2C/CPII ratio could be employed in longitudinal studies, since it may reflect a risk for DRA related arthropathy development in a subset of patients.

Extracellular matrix and pathogenic mechanisms in osteoarthritis

Osteoarthritis (OA) is a heterogeneous condition of joint degeneration characterized by structural changes in extracellular matrices such as subchondral bone and cartilage. Research has identified many diverse ways of initiating OA, varying from mechanical disruption to gene mutations in structural proteins. A frequent end point is cartilage loss, which can occur irrespective of the initiating mechanism. Of the mechanisms responsible for cartilage matrix damage, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5 was identified as of key importance in knockout mice, but work with human cartilage has suggested that ADAMTS-4 was also involved. A transgenic mouse expressing aggrecan lacking a key aggrecanase site clearly showed that loss of aggrecan from cartilage was an important step in both inflammatory and trauma-induced joint degeneration. In OA, cartilage chondrocytes show changes in gene expression, and it remains to be resolved if this reflects adaptive responses to changes in biological, physical, and mechanical signaling rather than any form of differentiation.

Biomarkers, type II collagen, glucosamine and chondroitin sulfate in osteoarthritis follow-up: the "Magenta osteoarthritis study"

Background

The purpose of the present study was to determine relationship between disease activity, systemic markers of cartilage degradation, urinary C-terminal cross-linking telopeptides of type II collagen (uCTX-II), and bone degradation, urinary C-terminal cross-linking telopeptides of type I collagen (uCTX-I), structural progression of osteoarthritis (OA) and potential therapeutic efficacy of type II collagen (COLLII) in combination with glucosamine and chondroitin sulfate (GC).

Materials and methods

An observational retrospective study, 1-year follow-up, on 104 patients with OA (nodular osteoarthritis of the hand, erosive osteoarthritis of the hand, EOA, osteoarthritis of the knee or hip) who were treated with GC or glucosamine, chondroitin sulfate and collagen type II (GCC). The following information was collected at entry: demographics, BMI, characteristics of OA, patient global assessment (VAS), C-terminal cross-linking telopeptides of collagen types I (uCTX-I) and II (uCTX-II) and radiographs. After 6 months: VAS, uCTX-I and uCTX-II. After 1 year: VAS, uCTX-I, uCTX-II and radiographs.

Results

After 6 months and 1 year of treatment VAS, uCTX-I and uCTX-II mean values were significantly lower than the baseline. 57 were treated with GCC and 47 with GC. The group that received GCC showed a similar VAS mean value after 6 months and 1 year when compared with the group treated with GC. uCTX-I and uCTX-II mean level was lower in the group treated with GCC (P < 0.05). Radiological score (Kellgren and Lawrence summarized score for hands) after 1 year showed a reduced progression compared to the baseline in the hand osteoarthritis group, especially after GCC treatment (P < 0.05). Finally, uCTX-I has better correlation with radiological score and with GC in the EOA subgroup (Pearson index: R = 0.44).

Conclusions

(a) uCTX-I and uCTX-II proved to be useful biomarkers in OA monitoring; (b) uCTX-I is better correlated with hand EOA and could represent a potential further marker to assess the evolution of EOA bone damage; (c) GC slow down OA progression; (d) finally COLLII could represent a further protective factor in OA cartilage.