Some highlights in the emergence of modern concepts of osteoarthritis

Osteoarthritis

The clinical appearance and radiological pattern of osteoarthritis have been identified in the skeletons of dinosaurs some 50-70 million years old, and in Egyptian mummies, and in ancient skeletons in England. Osteoarthritis patterns of joint involvement, often referred to as primary osteoarthritis, can be seen in the hands, spinal facet joints, hips, knees and feet, but can also be termed secondary osteoarthritis when seen in any joint that has had trauma, sepsis, surgery or metabolic insult. The prevalence of osteoarthritis increases with age. The histology and pathophysiology both demonstrate an inflammatory process. While there have been studies of genetic predisposition, the basic cause of primary osteoarthritis has not been determined.

Inflammation in osteoarthritis: is it time to dampen the alarm(in) in this debilitating disease?

Osteoarthritis (OA) is the most common joint disease that strongly reduces the quality of life in patients; However, no disease-modifying therapy is available. For a long time, OA was considered a non-inflammatory disease that was the result of 'wear-and-tear' and abnormal mechanics, and therefore many considered the term 'osteoarthritis' a misnomer. However, during the last decades the notion arose that inflammation is not only present in the majority of OA patients but, rather, actively involved in the progression of the disease. Influx of immune cells is observed in the synovium and a plethora of inflammatory mediators is present in tissues and fluids from OA patients. These mediators cause the production of degrading enzymes that break down the cartilage matrix, which is the main hallmark of OA. Alarmins, which belong to the group of danger signals, have been implicated in many inflammatory diseases. They are among the first factors to be released upon cell stress due to, for example, infection, damage and inflammation. They attract and activate cells of the immune system and therefore lie at the base of the inflammatory reaction. In this narrative review, an overview of the history of OA, the evolving concept of inflammation as important factor in the OA pathogenesis, and particularly the central role that alarmins play in the initiation and maintenance of the low-grade inflammatory response in OA, is provided. Moreover, the targeting of alarmins as a promising approach to dampen the inflammation in OA is highlighted.

Stem cell therapy for joint problems using the horse as a clinically relevant animal model

Research into articular cartilage is a surprisingly recent endeavour and much remains to be learned about the normal development of the synovial joint and its components that interplay in osteoarthritis and focal cartilage defects. Stem cell research is likely to contribute to the understanding of the developmental biology of synovial joints and their pathologies. Before human clinical trials are undertaken, stem cell-based therapies for non-life threatening disorders should be evaluated for their safety and efficacy using animal models of spontaneous disease and not solely by the existing laboratory models of experimentally induced lesions. The horse lends itself as a good animal model of spontaneous joint disorders that are clinically relevant to similar human disorders. Equine stem cell and tissue engineering studies may be financially feasible to principal investigators and small biotechnology companies if the equine industry is successfully engaged in the research process.

Electrical impedance signal analysis in assessing the possibility of non-invasive diagnosis of knee osteoarthritis

Knee osteoarthritis (OA) is a degenerating disorder that leads to pain, disability and dependence. Although significant numbers of elderly people are affected by this irreversible damage, not many non-invasive methods have been found that can detect onset of OA. The traditional x-ray has the disadvantage of detecting a problem only after many changes have taken place. Others, such as MRI and ultrasound, are either expensive or unsuitable for mass screening and repeated use. In this paper, an attempt has been made to study the usefulness of electrical impedance plethysmography (EIP) in non-invasive diagnosis of knee OA. In two experiments on 10 OA knees and eight control knees in groups aged 45 - 65 years (OA group: 62.40 +/- 3.47 years, controls: 53.38 +/- 8.55 years), knee swing (active flexion and extension of leg in sitting position, KS) and normal walking (WN) electrical impedance changes (DeltaZ) around the knee were analysed. The results indicate that there is significant difference in amplitudes of signals. Difference in mean of variances of two groups was significant (p < 0.05) for KS and WN. The difference in the mean rms values was also significant (p < 0.05) for KS and WN. Impedance changes suggest that EIP signal around the knee have the potential for non-invasive diagnosis of knee OA.

Binding and localization of recombinant lubricin to articular cartilage surfaces

Lubricin is a secreted, cytoprotective glycoprotein that contributes to the essential boundary lubrication mechanisms necessary for maintaining low friction levels at articular cartilage surfaces. Diminishment of lubricin function is thereby implicated as an adverse contributing factor in degenerative joint diseases such as osteoarthritis. Lubricin occurs as a soluble component of synovial fluid, and is synthesized and localized in the superficial layer of articular cartilage (and thus has also been described as "superficial zone protein", or SZP); however, defined interactions responsible for lubricin retention at this site are not well characterized. In the current studies, we identified molecular determinants that enable lubricin to effectively bind to articular cartilage surfaces. Efficient and specific binding to the superficial zone was observed for synovial lubricin, as well as for recombinant full-length lubricin and a protein construct comprising the lubricin C-terminal (hemopexin-like) domain (LUB-C, encoded by exons 7-12). A construct representing the N-terminal region of lubricin (LUB-N, encoded by exons 2-5) exhibited no appreciable cartilage-binding ability, but displayed the capacity to dimerize, and thus potentially influence lubricin aggregation. Disulfide bond disruption significantly attenuated recombinant lubricin and LUB-C binding to cartilage surfaces, demonstrating a requirement for protein secondary structure in facilitating the appropriate localization of lubricin at relevant tissue interfaces. These findings help identify additional key attributes contributing to lubricin functionality, which would be expected to be instrumental in maintaining joint homeostasis.

Viscosupplementation for the treatment of osteoarthritis of the knee

BACKGROUND

Osteoarthritis (OA) is the most prevalent chronic joint disorder worldwide and is associated with significant pain and disability.

OBJECTIVES

To assess the effects of viscosupplementation in the treatment of OA of the knee. The products were hyaluronan and hylan derivatives (Adant, Arthrum H, Artz (Artzal, Supartz), BioHy (Arthrease, Euflexxa, Nuflexxa), Durolane, Fermathron, Go-On, Hyalgan, Hylan G-F 20 (Synvisc Hylan G-F 20), Hyruan, NRD-101 (Suvenyl), Orthovisc, Ostenil, Replasyn, SLM-10, Suplasyn, Synject and Zeel compositum).

SEARCH STRATEGY

MEDLINE (up to January (week 1) 2006 for update), EMBASE, PREMEDLINE, Current Contents up to July 2003, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched. Specialised journals and reference lists of identified randomised controlled trials (RCTs) and pertinent review articles up to December 2005 were handsearched.

SELECTION CRITERIA

RCTs of viscosupplementation for the treatment of people with a diagnosis of OA of the knee were eligible. Single and double-blinded studies, placebo-based and comparative studies were eligible. At least one of the four OMERACT III core set outcome measures had to be reported (Bellamy 1997).

DATA COLLECTION AND ANALYSIS

Each trial was assessed independently by two reviewers for its methodological quality using a validated tool. All data were extracted by one reviewer and verified by a second reviewer . Continuous outcome measures were analysed as weighted mean differences (WMD) with 95% confidence intervals (CI). However, where different scales were used to measure the same outcome, standardized mean differences (SMD) were used. Dichotomous outcomes were analyzed by relative risk (RR).

MAIN RESULTS

Seventy-six trials with a median quality score of 3 (range 1 to 5) were identified. Follow-up periods varied between day of last injection and eighteen months. Forty trials included comparisons of hyaluronan/hylan and placebo (saline or arthrocentesis), ten trials included comparisons of intra-articular (IA) corticosteroids, six trials included comparisons of nonsteroidal anti-inflammatory drugs (NSAIDs), three trials included comparisons of physical therapy, two trials included comparisons of exercise, two trials included comparisons of arthroscopy, two trials included comparisons of conventional treatment, and fifteen trials included comparisons of other hyaluronans/hylan. The pooled analyses of the effects of viscosupplements against 'placebo' controls generally supported the efficacy of this class of intervention. In these same analyses, differential efficacy effects were observed for different products on different variables and at different timepoints. Of note is the 5 to 13 week post injection period which showed a percent improvement from baseline of 28 to 54% for pain and 9 to 32% for function. In general, comparable efficacy was noted against NSAIDs and longer-term benefits were noted in comparisons against IA corticosteroids. In general, few adverse events were reported in the hyaluronan/hylan trials included in these analyses.

AUTHORS' CONCLUSIONS

Based on the aforementioned analyses, viscosupplementation is an effective treatment for OA of the knee with beneficial effects: on pain, function and patient global assessment; and at different post injection periods but especially at the 5 to 13 week post injection period. It is of note that the magnitude of the clinical effect, as expressed by the WMD and standardised mean difference (SMD) from the RevMan 4.2 output, is different for different products, comparisons, timepoints, variables and trial designs. However, there are few randomised head-to-head comparisons of different viscosupplements and readers should be cautious, therefore, in drawing conclusions regarding the relative value of different products. The clinical effect for some products, against placebo, on some variables at some timepoints is in the moderate to large effect-size range. Readers should refer to relevant tables to review specific detail given the heterogeneity in effects across the product class and some discrepancies observed between the RevMan 4.2 analyses and the original publications. Overall, the analyses performed are positive for the HA class and particularly positive for some products with respect to certain variables and timepoints, such as pain on weight bearing at 5 to 13 weeks postinjection. In general, sample-size restrictions preclude any definitive comment on the safety of the HA class of products; however, within the constraints of the trial designs employed no major safety issues were detected. In some analyses viscosupplements were comparable in efficacy to systemic forms of active intervention, with more local reactions but fewer systemic adverse events. In other analyses HA products had more prolonged effects than IA corticosteroids. Overall, the aforementioned analyses support the use of the HA class of products in the treatment of knee OA.

Osteoarthritis cartilage histopathology: grading and staging

OBJECTIVE

Current osteoarthritis (OA) histopathology assessment methods have difficulties in their utility for early disease, as well as their reproducibility and validity. Our objective was to devise a more useful method to assess OA histopathology that would have wide application for clinical and experimental OA assessment and would become recognized as the standard method.

DESIGN

An OARSI Working Group deliberated on principles, standards and features for an OA cartilage pathology assessment system. Using current knowledge of the pathophysiology of OA morphologic features, a proposed system was presented at OARSI 2000. Subsequently, this was widely circulated for comments amongst experts in OA pathology.

RESULTS

An OA cartilage pathology assessment system based on six grades, which reflect depth of the lesion and four stages reflecting extent of OA over the joint surface was developed.

CONCLUSIONS

The OARSI cartilage OA histopathology grading system appears consistent and simple to apply. Further studies are required to confirm the system's utility.

Biomarkers in osteoarthritis

PURPOSE OF REVIEW

Biomarker discovery and validation for osteoarthritis have accelerated over the past several years, coincident with an evolving understanding of joint tissue molecules and their complex interactions, and the compelling need for improved osteoarthritis outcome measures in clinical trials. This review highlights advances in osteoarthritis-related biomarker research within the past year.

RECENT FINDINGS

The studies in the past year involving biochemical markers in humans can be assigned to one of four categories: new approaches and new biomarkers, exploratory studies in specialized disease subsets, large cross-sectional validation studies, and longitudinal studies, with and without an intervention.

SUMMARY

Most these studies have examined the association of a biomarker with some aspect of the natural history of osteoarthritis. As illustrated by the six studies reviewed here that included therapeutic interventions, however, several biomarkers are emerging that display credible association with disease modification. The expanding pool of informative osteoarthritis-related biomarkers is expected to positively impact the development of therapeutics for this disease and, it is hoped, ultimately clinical care.

Viscosupplementation for the treatment of osteoarthritis of the knee

BACKGROUND

Osteoarthritis (OA) is the most prevalent chronic joint disorder worldwide and is associated with significant pain and disability.

OBJECTIVES

To assess the effects of viscosupplementation in the treatment of OA of the knee. The products were hyaluronan and hylan derivatives (Adant, Arthrum H, Artz (Artzal, Supartz), BioHy (Arthrease), Durolane, Fermathron, Go-On, Hyalgan, Hylan G-F 20 (Synvisc Hylan G-F 20), NRD-101, Orthovisc, Ostenil, Replasyn, SLM-10, Suplasyn, Synject and Zeel compositum).

SEARCH STRATEGY

MEDLINE, EMBASE, PREMEDLINE, Current Contents up to July 2003, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched. Specialised journals and reference lists of identified randomised controlled trials (RCTs) and pertinent review articles up to April 2004 were handsearched.

SELECTION CRITERIA

RCTs of viscosupplementation for the treatment of people with a diagnosis of OA of the knee were eligible. Single and double-blinded studies, placebo-based and comparative studies were eligible. At least one of the four OMERACT III core set outcome measures had to be reported (Bellamy 1997).

DATA COLLECTION AND ANALYSIS

Each trial was assessed independently by two reviewers (NB, JC) for its methodological quality using a validated tool. All data were extracted by one reviewer (JC) and verified by a second reviewer (VR). Continuous outcome measures were analysed as weighted mean differences (WMD) with 95% confidence intervals (CI). Dichotomous outcomes were analyzed by relative risk (RR).

MAIN RESULTS

Sixty-three trials with a median quality score of 3 (range 1 to 5) were identified. Follow-up periods varied between day of last injection and one year. Thirty-seven trials included comparisons of hyaluronan/hylan and placebo, nine trials included comparisons of intra-articular (IA) corticosteroids, and five trials included comparisons of nonsteroidal anti-inflammatory drugs (NSAIDs). The pooled analyses of the effects of viscosupplements against 'placebo' controls generally supported the efficacy of this class of intervention. In these same analyses, differential efficacy effects were observed for different products on different variables and at different timepoints. Of note is the 5 to 13 week post injection period which showed a percent improvement from baseline of 11 to 54% for pain and 9 to 15% for function. In general, comparable efficacy was noted against NSAIDs and longer-term benefits were noted in comparisons against IA corticosteroids. In general, few adverse events were reported in the hyaluronan/hylan trials included in these analyses.

AUTHORS' CONCLUSIONS

Based on the aforementioned analyses, viscosupplementation is an effective treatment for OA of the knee with beneficial effects: on pain, function and patient global assessment; and at different post injection periods but especially at the 5 to 13 week post injection period. It is of note that based on non-randomised groups, the magnitude of the clinical effect, as expressed by the WMD and standardised mean difference (SMD) from the RevMan 4.1 output, is different for different products, comparisons, timepoints, variables and trial designs. However, there are few randomised head-to-head comparisons of different viscosupplements and readers should be cautious, therefore, in drawing conclusions regarding the relative value of different products. The clinical effect for some products, against placebo, on some variables at some timepoints is in the moderate to large effect-size range. Readers should refer to relevant tables to review specific detail given the heterogeneity in effects across the product class and some discrepancies observed between the RevMan 4.1 analyses and the original publications. Overall, the analyses performed are positive for the HA class and particularly positive for some products with respect to certain variables and timepoints, such as pain on weight bearing at 5 to 13 weeks postinjection. In general, sample-size restrictions preclude any definitive comment on the safety of the HA class of products; however, within the constraints of the trial designs employed no major safety issues were detected. In some analyses viscosupplements were comparable in efficacy to systemic forms of active intervention, with more local reactions but fewer systemic adverse events. In other analyses HA products had more prolonged effects than IA corticosteroids. Overall, the aforementioned analyses support the use of the HA class of products in the treatment of knee OA.

Physical indicators of cartilage health: the relevance of compliance, thickness, swelling and fibrillar texture

This study uses a bovine patella model to compare the relative merits of on-bone compliance and thickness measurements, free-swelling behaviour, and structural imaging with differential interference contrast (DIC) light microscopy to assess the biomechanical normality of the cartilage matrix. The results demonstrate that across a spectrum of cartilage tissues from immature, mature, through to mildly degenerate, and all with intact articular surfaces, there is a consistent pattern of increased free swelling of the isolated general matrix with age and degeneration. High swelling was always associated with major structural alterations of the general matrix that were readily imaged using DIC light microscopy. Conversely, for all tissue groups, no relationship was observed between thickness vs. compliance and compliance vs. general matrix swelling. Only in the proximal aspects of the normal mature and degenerate tissues was there a correlation between thickness and general matrix swelling. Free-swelling measurements combined with fibrillar texture imaging using DIC light microscopy are therefore recommended as providing a reliable and quick method of assessing the biomechanical condition of the cartilage general matrix.

Immune regulation in adjuvant disease and other arthritis models: relevance to pathogenesis of chronic arthritis

Experimental models of arthritis and their human counterparts fall into three distinct classes: (a) responses of T cells to disseminated microbial antigens (Ags) as such; (b) responses of T cells to cartilage autoAgs; and (c) responses of T cells to major histocompatibility complex (HLA-B27, DRB1) or other membrane components (LFA-1) expressed on bone marrow-derived cells. The primary immune response is driven, in naturally occurring disease, by microbial infection, e.g. with streptococci, enteric gram-negative rods or spirochetes, or is experimentally induced with mycobacterial and other adjuvants. The response to cartilage components, such as collagen type-II and various proteoglycans, may be driven by cross-reactive microbial Ags, heat shock proteins (HSPs) in particular, or the adjuvant effect of intense primary joint inflammation, as in rheumatoid arthritis and the spondyloarthropathies. Adjuvant disease appears to be purely T-cell-mediated, whereas both T cells and antibody play a role in collagen and many other forms of arthritis. Experimental evidence suggests a pathogenetic role for T-cell receptor gammadelta T cells in some lesions. Arthritis may be regulated by microbial and tissue HSPs, when these are administered by a nonimmunizing route or as altered peptide ligands, by anti-idiotypic responses that block the action of effector T cells, and by competing Ags. Immune regulation involving natural killer (NK), NK T and certain subsets of gammadelta and alphabeta T cells, which may affect the occurrence, localization and character of this group of diseases, presents a challenge for further investigation.