Relationship between Investigative Biomarkers and Radiographic Grading in Patients with Knee Osteoarthritis

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

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

TGF-β1 and Mechanical-Stretch Induction of Lysyl-Oxidase and Matrix-Metalloproteinase Expression in Synovial Fibroblasts Requires NF-κB Pathways

The imbalance in the expression of matrix metalloproteinases (MMPs) and lysyl oxidases (LOXs) in synovial fibroblasts (SFs) caused by mechanical injury and inflammatory response prevents injured anterior cruciate ligaments (ACLs) from self-healing. However, research on the effect of growth factors on SFs on regulating the microenvironment is limited. In this study, mechanical injury and exogenous transform growth factor-β1 (TGF-β1) were employed to mimic a joint-cavity microenvironment with ACL trauma. The function of the NF-κB transcription factor was further studied. The study found that the gene expression of LOXs (except LOXL-1), MMP-1, -2, and -3 in SFs was promoted by the combination of injurious mechanical stretching and TGF-β1 and that the upregulation of MMPs was higher than that of LOXs. In addition, MMP-2 activity induced by the combination of injurious stretch and TGF-β1 was inhibited by NF-κB inhibitors such as Bay11-7082 and Bay11-7085. The findings concluded that the synovium was an important regulator of the knee joint-cavity microenvironment after ACL injury and that the NF-κB pathway mediated the regulation of MMP-2 in SFs via mechanical factors and TGF-β1.

Concentration of Selected Metalloproteinases and Osteocalcin in the Serum and Synovial Fluid of Obese Women with Advanced Knee Osteoarthritis

The aim of the study was to evaluate the levels of selected MMPs (matrix metalloproteinases) and osteocalcin in the serum and synovial fluid of obese women with osteoarthritis and their correlations with clinical status. The studied group consisted of 39 overweight females undergoing primary total knee arthroplasty due to osteoarthritis (OA). The staging of knee OA was evaluated according to the Ahlbӓck and Kellgren–Lawrence scores. Synovial fluid and peripheral blood samples were obtained. The levels of selected MMPs and osteocalcin were assessed using commercial ELISA kits. The mean value of MMP3 was significantly higher in patients with more advanced disease in both serum (p = 0.0067) and synovial fluid (p = 0.0328). The pro-MMP13 level tended to be higher in synovial fluid in the case of more advanced stages (p = 0.0882), with no tendency regarding the serum level (p = 0.9595). The synovial level of pro-MMP1 was significantly correlated with the synovial concentration of MMP9 and MMP3. The synovial level of MMP9 also showed a significant correlation with the synovial level of MMP3 and pro-MMP13. Furthermore, it was found that the serum level of MMP3 was significantly correlated with the synovial pro-MMP13 level. A correlation between the osteocalcin level in serum and its synovial level was determined. The serum MMP9 level showed a significant correlation with BMI, whereas the synovial MMP9 level was notably correlated with age. Our results showed that the levels of MMP3, MMP9, and pro-MMP13 increased in more advanced radiological stages of OA, indicating the underlying inflammatory process of OA.

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

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Moving toward targeting the right phenotype with the right platelet-rich plasma (PRP) formulation for knee osteoarthritis

Intra-articular injections of platelet-rich plasma (PRP) and other novel blood-derived products developed specifically for osteoarthritis (OA) can provide pain relief and potential benefits in disease progression. Meta-analyses show the clinical superiority of PRP compared with other intra-articular injections, but results are modest and the effect sizes are small. PRP injections in knee OA are performed indiscriminately, but the clinical response varies enormously between patients because of an array of mixed OA phenotypes. Subgroup analyses are scarce; some studies stratify patients according to radiographic severity and found better results in early OA, without consensus for more advanced stages of the condition. Parallel identification of soluble and imaging biomarkers is essential to personalise and leverage PRP therapies. The inflammatory phenotype is most interesting from the PRP perspective because PRPs modulate inflammation by releasing a large pool of chemokines and cytokines, which interact with synovial fibroblasts and macrophages; in addition, they can modulate the innate immune response. No soluble biomarkers have been discovered that have implications for OA research and PRP interventions. Clinical examination of patients based on their inflammatory phenotype and imaging identification of pain sources and structural alterations could help discern who will respond to PRP. Synovial inflammation and bone marrow lesions are sources of pain, and intra-articular injections of PRP combined with subchondral bone injection can enhance clinical outcomes. Further refining ultrasound phenotypes may aid in personalising PRP therapies. Intra-articular delivery combined with injections in altered ligamentous structures, medial and coronal ligaments or premeniscal pes anserinus showed positive clinical outcomes. Although the evidence supporting these approaches are weak, they merit further consideration to refine PRP protocols and target the right OA phenotypes.

An Evidence-Based Systematic Review of Human Knee Post-Traumatic Osteoarthritis (PTOA): Timeline of Clinical Presentation and Disease Markers, Comparison of Knee Joint PTOA Models and Early Disease Implications

Understanding the causality of the post-traumatic osteoarthritis (PTOA) disease process of the knee joint is important for diagnosing early disease and developing new and effective preventions or treatments. The aim of this review was to provide detailed clinical data on inflammatory and other biomarkers obtained from patients after acute knee trauma in order to (i) present a timeline of events that occur in the acute, subacute, and chronic post-traumatic phases and in PTOA, and (ii) to identify key factors present in the synovial fluid, serum/plasma and urine, leading to PTOA of the knee in 23-50% of individuals who had acute knee trauma. In this context, we additionally discuss methods of simulating knee trauma and inflammation in in vivo, ex vivo articular cartilage explant and in vitro chondrocyte models, and answer whether these models are representative of the clinical inflammatory stages following knee trauma. Moreover, we compare the pro-inflammatory cytokine concentrations used in such models and demonstrate that, compared to concentrations in the synovial fluid after knee trauma, they are exceedingly high. We then used the Bradford Hill Framework to present evidence that TNF-α and IL-6 cytokines are causal factors, while IL-1β and IL-17 are credible factors in inducing knee PTOA disease progresssion. Lastly, we discuss beneficial infrastructure for future studies to dissect the role of local vs. systemic inflammation in PTOA progression with an emphasis on early disease.

Investigation of Cytokine Changes in Osteoarthritic Knee Joint Tissues in Response to Hyperacute Serum Treatment

One option to fight joint degradation and inflammation in osteoarthritis is the injection of activated blood products into the synovial space. It has been demonstrated that hyperacute serum is the most proliferative among plasma products, so we investigated how the cytokine milieu of osteoarthritic knee joint reacts to hyperacute serum treatment in vitro. Cartilage, subchondral bone, and synovial membrane explanted from osteoarthritic knees were stimulated by interleukin-1 beta (IL-1β) and the concentration of 39 biomarkers was measured in the co-culture supernatant after hyperacute serum treatment. The IL-1β stimulation triggered a strong inflammatory response and enhanced the concentrations of matrix metalloproteinase 3 and 13 (MMP-3 and MMP-13), while hyperacute serum treatment reduced inflammation by decreasing the concentrations of IL-1β, tumor necrosis factor alpha (TNF-α), interleukin-6 receptor alpha (IL-6Rα), and by increasing the level of interleukin-1 antagonist (IL-1RA) Cell viability increased by day 5 in the presence of hyperacute serum. The level of MMPs-1, 2, and 9 were higher on day 3, but did not increase further until day 5. The concentrations of collagen 1 alpha 1 (COL1A1) and osteonectin were increased and receptor activator of nuclear factor kappa-B ligand (RANKL) was reduced in response to hyperacute serum. We concluded that hyperacute serum treatment induces cell proliferation of osteoarthritic joint tissues and affects the cytokine milieu towards a less inflamed state.

Cell Therapies in Tendon, Ligament, and Musculoskeletal System Repair

In the last few decades, several techniques have been used to optimize tendon, ligament, and musculoskeletal healing. The evidence in favor of these techniques is still not proven, and level I studies are lacking. We performed an analysis of the therapeutic strategies and tissue engineering projects recently published in this field. Here, we try to give an insight into the current status of cell therapies and the latest techniques of bioengineering applied to the field of orthopedic surgery. The future areas for research in the management of musculoskeletal injuries are outlined. There are emerging technologies developing into substantial clinical treatment options that need to be critically evaluated. Mechanical stimulation of the constructs reproduces a more propitious environment for effective healing.

Cellular pharmacodynamic effects of Pycnogenol® in patients with severe osteoarthritis: a randomized controlled pilot study

BACKGROUND

The standardized maritime pine bark extract (Pycnogenol®) has previously shown symptom alleviating effects in patients suffering from moderate forms of knee osteoarthritis (OA). The cellular mechanisms for this positive impact are so far unknown. The purpose of the present randomized pilot controlled study was to span the knowledge gap between the reported clinical effects of Pycnogenol® and its in vivo mechanism of action in OA patients.

METHODS

Thirty three patients with severe OA scheduled for a knee arthroplasty either received 100 mg of Pycnogenol® twice daily or no treatment (control group) three weeks before surgery. Cartilage, synovial fluid and serum samples were collected during surgical intervention. Relative gene expression of cartilage homeostasis markers were analyzed in the patients' chondrocytes. Inflammatory and cartilage metabolism mediators were investigated in serum and synovial fluid samples.

RESULTS

The oral intake of Pycnogenol® downregulated the gene expression of various cartilage degradation markers in the patients' chondrocytes, the decrease of MMP3, MMP13 and the pro-inflammatory cytokine IL1B were statistically significant (p ≤ 0.05). Additionally, protein concentrations of ADAMTS-5 in serum were reduced significantly (p ≤ 0.05) after three weeks intake of the pine bark extract.

CONCLUSIONS

This is the first report about positive cellular effects of a dietary supplement on key catabolic and inflammatory markers in patients with severe OA. The results provide a rational basis for understanding previously reported clinical effects of Pycnogenol® on symptom scores of patients suffering from OA.

TRIAL REGISTRATION

ISRCTN10754119 . Retrospectively registered 08/10/2015.

Platelet Rich Plasma and Culture Configuration Affect the Matrix Forming Phenotype of Bone Marrow Stromal Cells

We aim to examine the influence of platelet rich plasma (PRP) and spatial cues in cartilage/bone matrix forming proteins, and to evaluate the mitotic and chemotactic potential of PRP on human mesenchymal stem cells (hMSCs). Directed cell migration towards PRP gradients was assessed in chemotactic chambers, and recorded by time-lapse microscopy. hMSCs cultured in three-dimensional (3D) scaffolds were visualized by scanning electron microscopy; Hoechst dye was used to confirm cell confluence in 3D-constructs and monolayers before experimental treatment. MSCs were treated with 10% PRP lysate or 10% PRP lysate supplemented with TGF-β-based differentiation medium. The expression of cartilage (COL2A1, Sox9, ACAN, COMP), and bone (COL1A1, VEGF, COL10A1, Runx2) fundamental genes was assessed by real time PCR in monolayers and 3D-constructs. PRP had mitotic (p < 0.001), and chemotactic effect on hMSCs, Ralyleigh test p = 1.02E - 10. Two and three-week exposure of MSCs to PRP secretome in 3D-constructs or monolayers decreased Sox9 expression (p < 0.001 and p = 0.050) and COL2A1, (p = 0.011 and p = 0.019). MSCs in monolayers exposed to PRP showed increased ACAN (p = 0.050) and COMP (p < 0.001). Adding TGF-β-based differentiation medium to PRP increased COMP, and COL2A1 expression at gene and protein level, but merely in 3D-constructs, p < 0.001. TGF-β addition to monolayers reduced Sox9 (p < 0.001), aggrecan (p = 0.004), and VEGF (p = 0.004). Cells exposed to PRP showed no changes in hypertrophy associated genes in either monolayers or 3D-constructs. Our study suggests hMSCs have high-degree of plasticity having the potential to change their matrix-forming phenotype when exposed to PRP and according to spatial configuration.

Mesenchymal Stem Cells and Their Clinical Applications in Osteoarthritis

Osteoarthritis is a chronic degenerative joint disorder characterized by articular cartilage destruction and osteophyte formation. Chondrocytes in the matrix have a relatively slow turnover rate, and the tissue itself lacks a blood supply to support repair and remodeling. Researchers have evaluated the effectiveness of stem cell therapy and tissue engineering for treating osteoarthritis. All sources of stem cells, including embryonic, induced pluripotent, fetal, and adult stem cells, have potential use in stem cell therapy, which provides a permanent biological solution. Mesenchymal stem cells (MSCs) isolated from bone marrow, adipose tissue, and umbilical cord show considerable promise for use in cartilage repair. MSCs can be sourced from any or all joint tissues and can modulate the immune response. Additionally, MSCs can directly differentiate into chondrocytes under appropriate signal transduction. They also have immunosuppressive and anti-inflammatory paracrine effects. This article reviews the current clinical applications of MSCs and future directions of research in osteoarthritis.

The relationship between synovial fluid VEGF and serum leptin with ultrasonographic findings in knee osteoarthritis

AIM

This study aimed to determine synovial fluid and serum biomarkers which could accord with radiological and ultrasonographic findings in knee osteoarthritis.

METHODS

Thirty-four patients with knee osteoarthritis were detected with joint effusion by clinical examination. Both knee joints were examined using plain radiographs and ultrasonography. Questions were obtained for visual analog scale (VAS), Western Ontario McMaster Universities Osteoarthritis Index and Health Assessment Questionnaire (HAQ). Synovial fluid (SF) and serum levels of vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)-13, leptin, resistin and cartilage oligomeric matrix protein (COMP) were measured using enzyme-linked immunosorbent assay.

RESULTS

Synovial fluid VEGF level was positively correlated with Kellgren-Lawrence (KL) grades and it was higher in patients with KL grade 4 than those with KL grade 2. SF VEGF correlated with ultrasonographic findings, such as the length of medial osteophytes. The amount of effusion was positively correlated with SF resistin. Serum leptin level had positive correlation with HAQ and the length of medial osteophytes. MMP-13 or COMP levels were not correlated with radiographic or ultrasonographic findings.

CONCLUSION

Synovial fluid VEGF level was correlated with radiographic grading, ultrasonographic findings and functional statues in knee osteoarthritis, and serum leptin level also correlated with the ultrasonographic findings and functional status of knee osteoarthritis.

Biomarkers of cartilage and surrounding joint tissue

The identification and clinical demonstration of efficacy and safety of osteo- and chondro-protective drugs are met with certain difficulties. During the last few decades, the pharmaceutical industry has, in the field of rheumatology, experienced disappointments associated with the development of disease modification. Today, the vast amount of patients suffering from serious, chronic joint diseases can only be offered treatments aimed at improving symptoms, such as pain and acute inflammation, and are not aimed at protecting the joint tissue. This huge, unmet medical need has been the driver behind the development of improved analytical techniques allowing better and more efficient clinical trial design, implementation and analysis. With this review, we aim to provide a brief and general overview of biochemical markers of joint tissue, with special focus on neoepitopes. Furthermore, we highlight recent studies applying biochemical markers in joint degenerative diseases. These disorders, including osteoarthritis, rheumatoid arthritis and spondyloarthropathies, are the most predominant disorders in Europe and the USA, and have enormous socioeconomical impact.

Association of Cross Linked C-Telopeptide II Collagen and Hyaluronic Acid with Knee Osteoarthritis Severity

BACKGROUND: This study was carried out to investigate the association of Cross Linked C-Telopeptide Type I & II Collagen (CTX-I and II) and hyaluronic acid (HA) with knee osteoarthritis (OA) severity.METHODS: Sixty menopause women with primary knee OA were enrolled in this study during their visits to the Outpatient Department. Patients with knee pain during weight bearing, active or passive range of motion, or tenderness with Kellgren-Lawrence (KL) grade of more than I were included. Patients with injury, inflammatory and metabolic diseases were excluded. Patients were put in a 10-hour fasting prior to withdrawal of morning blood samples for examinations of HA, CTX-I, interleukin 1 beta (IL-1β), and high sensitivity C reactive protein (hs-CRP) level. Second void morning urine specimens were taken for CTXII assessment. HA, CTX-I and II levels were measured by enzyme-linked immunosorbent assay.RESULTS: Sixty menopausal female patients were included in this study, 35 with KL grade II, 17 grade III, and 8 grade IV. Means of CTX-II were significantly different between subjects KL grade IV and III (p=0.021). Correlation of KL grade was significant with CTX-II (p=0.001, r=0.412) and HA (p=0.0411, r=0.269). KL grades were not significantly associated with CTX-I (p=0.8364, r=-0.0272); IL-1β (p=0.5773, r=0.0853) and hs-CRP (p=0.2625, r=0.1470).CONCLUSION: CTX-II and HA were associated with severity of knee OA, suggesting that CTX-II and HA can be used as marker for knee OA severity.KEYWORDS: CTX-II, hyaluronic acid, otestoarthritis, knee

Platelet-rich plasma for managing pain and inflammation in osteoarthritis

Osteoarthritis (OA) is a common disease involving joint damage, an inadequate healing response and progressive deterioration of the joint architecture. Autologous blood-derived products, such as platelet-rich plasma (PRP), are key sources of molecules involved in tissue repair and regeneration. These products can deliver a collection of bioactive molecules that have important roles in fundamental processes, including inflammation, angiogenesis, cell migration and metabolism in pathological conditions, such as OA. PRP has anti-inflammatory properties through its effects on the canonical nuclear factor κB signalling pathway in multiple cell types including synoviocytes, macrophages and chondrocytes. PRP contains hundreds of different molecules; cells within the joint add to this milieu by secreting additional biologically active molecules in response to PRP. The net results of PRP therapy are varied and can include angiogenesis, the production of local conditions that favour anabolism in the articular cartilage, or the recruitment of repair cells. However, the molecules found in PRP that contribute to angiogenesis and the protection of joint integrity need further clarification. Understanding PRP in molecular terms could help us to exploit its therapeutic potential, and aid the development of novel treatments and tissue-engineering approaches, for the different stages of joint degeneration.

Mesenchymal stem cells in joint disease and repair

Osteoarthritis (OA), a prevalent chronic condition with a striking impact on quality of life, represents an enormous societal burden that increases greatly as populations age. Yet no approved pharmacological intervention, biologic therapy or procedure prevents the progressive destruction of the OA joint. Mesenchymal stem cells (MSCs)-multipotent precursors of connective tissue cells that can be isolated from many adult tissues, including those of the diarthrodial joint-have emerged as a potential therapy. Endogenous MSCs contribute to maintenance of healthy tissues by acting as reservoirs of repair cells or as immunomodulatory sentinels to reduce inflammation. The onset of degenerative changes in the joint is associated with aberrant activity or depletion of these cell reservoirs, leading to loss of chondrogenic potential and preponderance of a fibrogenic phenotype. Local delivery of ex vivo cultures of MSCs has produced promising outcomes in preclinical models of joint disease. Mechanistically, paracrine signalling by MSCs might be more important than differentiation in stimulating repair responses; thus, paracrine factors must be assessed as measures of MSC therapeutic potency, to replace traditional assays based on cell-surface markers and differentiation. Several early-stage clinical trials, initiated or underway in 2013, are testing the delivery of MSCs as an intra-articular injection into the knee, but optimal dose and vehicle are yet to be established.

Metabolic syndrome meets osteoarthritis

Metabolic osteoarthritis (OA) has now been characterized as a subtype of OA, and links have been discovered between this phenotype and metabolic syndrome (MetS)--both with individual MetS components and with MetS as a whole. Hypertension associates with OA through subchondral ischaemia, which can compromise nutrient exchange into articular cartilage and trigger bone remodelling. Ectopic lipid deposition in chondrocytes induced by dyslipidemia might initiate OA development, exacerbated by deregulated cellular lipid metabolism in joint tissues. Hyperglycaemia and OA interact at both local and systemic levels; local effects of oxidative stress and advanced glycation end-products are implicated in cartilage damage, whereas low-grade systemic inflammation results from glucose accumulation and contributes to a toxic internal environment that can exacerbate OA. Obesity-related metabolic factors, particularly altered levels of adipokines, contribute to OA development by inducing the expression of proinflammatory factors as well as degradative enzymes, leading to the inhibition of cartilage matrix synthesis and stimulation of subchondral bone remodelling. In this Review, we summarize the shared mechanisms of inflammation, oxidative stress, common metabolites and endothelial dysfunction that characterize the aetiologies of OA and MetS, and nominate metabolic OA as the fifth component of MetS. We also describe therapeutic opportunities that might arise from uniting these concepts.

Matrix metalloproteinase protein expression profiles cannot distinguish between normal and early osteoarthritic synovial fluid

Background

Osteoarthritis (OA) and Rheumatoid arthritis (RA) are diseases which result in the degeneration of the joint surface articular cartilage. Matrix Metalloproteinases (MMPs) are enzymes that aid in the natural remodelling of tissues throughout the body including cartilage. However, some MMPs have been implicated in the progression of OA and RA as their expression levels and activation states can change dramatically with the onset of disease. Yet, it remains unknown if normal and arthritic joints demonstrate unique MMPs expression profiles, and if so, can the MMP expression profile be used to identify patients with early OA. In this study, the synovial fluid protein expression levels for MMPs 1, 2, 3, 7, 8, 9, 12 & 13, as well as those for the Tissue Inhibitors of MMPs (TIMPs) 1, 2, 3, & 4 were examined in highly characterized normal knee joints, and knee joints with clinically diagnosed OA (early and advanced) or RA. The purpose of this study was to determine if normal, OA, and RA patients exhibit unique expression profiles for a sub-set of MMPs, and if early OA patients have a unique MMP expression profile that could be used as an early diagnostic marker.

Methods

Synovial fluid was aspirated from stringently characterized normal knee joints, and in joints diagnosed with either OA (early and advanced) or RA. Multiplexing technology was employed to quantify protein expression levels for 8 MMPs and 4 TIMPs in the synovial fluid of 12 patients with early OA, 17 patients diagnosed with advanced OA, 15 with RA and 25 normal knee joints. Principle component analysis (PCA) was used to reveal which MMPs were most influential in the distinction between treatment groups. K – means clustering was used to verify the visual grouping of subjects via PCA.

Results

Significant differences in the expression levels of MMPs and TIMPs were observed between normal and arthritic synovial fluids (with the exception of MMP 12). PCA demonstrated that MMPs 2, 8 & 9 can be used to effectively separate individuals diagnosed with advanced arthritis from early osteoarthritic and normal individuals, however, these MMP profiles do not separate early OA from normal synovial fluid. An apparent separation between advanced OA and RA subjects was also revealed through PCA. K-means clustering verified the presence of 3 clusters: normal joints clustered with early OA, and separate clusters of advanced OA or RA.

Conclusions

This study demonstrates that unique MMP and TIMP expression profiles are present within normal, advanced OA and RA synovial fluid. These MMP profiles can be used to distinguish advanced OA & RA synovial fluid from early OA & normal synovial fluid, and even between synovial fluid samples from OA and RA joints. Although this methodology cannot be used for the diagnosis of early OA, high throughput multiplex technology of MMPs and TIMPs in synovial fluid may prove useful in determining the severity of the disease state, and/or quantifying the response of individuals to disease interventions.

Interleukin-7 levels in synovial fluid increase with age and MMP-1 levels decrease with progression of osteoarthritis

BACKGROUND AND PURPOSE

Little is known about biochemical mediators that correlate with the initiation and progression of knee osteoarthritis (OA). We therefore valuated the roles of cytokines and metalloenzymes in knee OA in relation to OA grading, age, and BMI.

PATIENTS AND METHODS

A multiplex ELISA-based immunoassay (Luminex technology) was used to measure biochemical mediators in the synovial fluid (SF) of 82 patients undergoing knee surgery. All patients were classified according to age, BMI, and OA grade. 24 patients had no signs of OA (knee reconstruction surgeries). The mediators that were tested for included interleukins (IL-1Ra, IL-6, IL-7, and IL-18), chemokines (CCL2 (MCP-1), CCL3 (MIP-1a), and CXCL8 (IL-8)), growth factors (HGF and VEGF), and matrix metalloproteinases (MMP-1, MMP-2, MMP-9, and MMP-13).

RESULTS

There was a correlation between IL-7 levels in SF and age (p < 0.01). The 11 highest IL-7 levels were seen in patients who were aged between 59 and 72 but had different OA grades. In contrast, all patients who had severe OA in all 3 knee compartments (pan-OA) had only low or medium IL-7 levels. There was a negative correlation between MMP-1 levels in synovial fluid and grade of OA (p < 0.001). Correlation studies between pairs of mediators revealed two groups of mediators that are important in OA progression, dominated by MCP-1 and IL-1Ra.

INTERPRETATION

IL-7 levels in SF are elevated in elderly people suffering from OA of different grades, but they are depressed in patients with severe 3-compartment OA, possibly due to widely impaired chondrocytes embedded in the affected cartilage tissue. The observed decrease in MMP-1 levels in SF, which is dependent on the severity of OA, may be caused by deterioration of superficial cartilage layers during progression of OA.

Correlation between plasma and synovial fluid basic fibroblast growth factor with radiographic severity in primary knee osteoarthritis

PURPOSE

The aim of this study was to investigate plasma and synovial fluid basic fibroblast growth factor (bFGF) levels in patients with primary knee osteoarthritis (OA) and to evaluate the correlation between bFGF levels and disease severity.

METHODS

Thirty-five patients with knee OA and 15 healthy individuals were recruited into this study. Knee OA grading was performed according to the Kellgren-Lawrence classification. bFGF concentrations in both plasma and synovial fluid were determined using enzyme-linked immunosorbent assay.

RESULTS

Plasma and synovial fluid bFGF levels in knee OA patients were significantly higher than in controls (P < 0.001). Moreover, plasma and synovial fluid bFGF concentrations were positively correlated with radiographic severity (r = 0.535, P < 0.001 and r = 0.570, P < 0.001, respectively). Further analysis revealed that there was a positive correlation between plasma and synovial fluid bFGF levels (r = 0.674, P < 0.001).

CONCLUSIONS

Plasma and synovial fluid bFGF levels were significantly increased in OA patients, and these elevated levels were positively correlated with radiographic severity. These findings indicate that bFGF levels may be a monitor of disease severity and could play an essential part in the pathophysiology of degenerative process in OA.

The relationship between fibrogenic TGFβ1 signaling in the joint and cartilage degradation in post-injury osteoarthritis

OBJECTIVE

To review the literature on modulation of chondrocyte activities in the osteoarthritic joint, and to discuss these changes in relation to established hard and soft tissue repair paradigms, with an emphasis on transforming growth factor beta (TGFβ1)-mediated signaling which can promote either a chondrogenic or fibrogenic phenotype.

METHODS

Papers addressing the close relationship between repair in general, and the specific post-injury response of joint tissues are summarized. Different interpretations of the role of TGFβ1 in the emergence of an "osteoarthritic" chondrocyte are compared and the phenotypic plasticity of "reparative" progenitor cells is examined. Lastly, emerging data on a central role for A-Disintegrin-And-Metalloproteinase-with-Thrombospondin-like-Sequences-5 (ADAMTS5) activity in modulating TGFβ1 signaling through activin receptor-like kinase 1 (ALK1) and activin receptor-like kinase 5 (ALK5) pathways is discussed.

RESULTS

The review illustrates how a transition from ALK5-mediated fibrogenic signaling to ALK1-mediated chondrogenic signaling in joint cells represents the critical transition from a non-reparative to a reparative cell phenotype. Data from cell and in vivo studies illustrates the mechanism by which ablation of ADAMTS5 activity allows the transition to reparative chondrogenesis. Multiple large gene expression studies of normal and osteoarthritis (OA) human cartilages (CAs) also support an important role for TGFβ1-mediated pro-fibrogenic activities during disease progression.

CONCLUSIONS

We conclude that progressive articular CA damage in post-injury OA results primarily from biomechanical, cell biologic and mediator changes that promote a fibroblastic phenotype in joint cells. Since ADAMTS5 and TGFβ1 appear to control this process, agents which interfere with their activities may not only enhance endogenous CA repair in vivo, but also improve the properties of tissue-engineered CA for implantation.