Scholarly article on topic 'Plasma and synovial osteopontin levels, are they associated with disease severity of primary knee osteoarthritis in Egyptian patients?'

Plasma and synovial osteopontin levels, are they associated with disease severity of primary knee osteoarthritis in Egyptian patients? Academic research paper on "Clinical medicine"

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{"Knee osteoarthritis" / Osteopontin / Radiography / "Magnetic resonance"}

Abstract of research paper on Clinical medicine, author of scientific article — Hala M. Haider, Irene R. Amin, Khaled A. Ahmad

Abstract Aim of the work The aim of this study was to examine osteopontin (OPN) levels in both plasma and synovial fluid of patients with primary knee osteoarthritis (OA) and to investigate their relationship with severity of the disease. Patients and methods Fifty patients with primary knee OA were compared to twenty-five apparently healthy controls. OPN levels in plasma and synovial fluid were measured using enzyme-linked immunosorbent assay. Severity of knee pain was assessed by the Western Ontario and McMaster Universities osteoarthritis index. Radiographic grading of knee OA was performed by Kellgren–Lawrence criteria. Magnetic resonance imaging (MRI) was also performed on painful knees. Results Plasma OPN was higher in patients (159.65±28.56ng/ml) than controls (90.45±23.63ng/ml). OPN in plasma and synovial fluid was correlated with severity of knee pain (r =0.878, r =0.795, P <0.001). Cartilage loss, marginal osteophytes and subchondral bone cyst were the commonest MRI findings in knee OA. MRI detected also patients with early knee OA that were not detected by plain radiography. Conclusion OPN serves as a biochemical marker of disease severity in knee OA. It also could be predictive to the progression of disease.

Academic research paper on topic "Plasma and synovial osteopontin levels, are they associated with disease severity of primary knee osteoarthritis in Egyptian patients?"

The Egyptian Rheumatologist (2014) xxx, xxx-xxx

Egyptian Society for Joint Diseases and Arthritis The Egyptian Rheumatologist

www.rheumatology.eg.net www.sciencedirect.com

ORIGINAL ARTICLE

Plasma and synovial osteopontin levels, are they associated with disease severity of primary knee osteoarthritis in Egyptian patients?

Hala M. Haider a *, Irene R. Amin a, Khaled A. Ahmad b

a Physical Medicine, Rheumatology and Rehabilitation Department, Faculty of Medicine, Ain Shams University, Egypt b Radiodiagnosis Department, Faculty of Medicine, Ain Shams University, Egypt

Received 17 April 2014; accepted 3 May 2014

KEYWORDS

Knee osteoarthritis; Osteopontin; Radiography; Magnetic resonance

Abstract Aim of the work: The aim of this study was to examine osteopontin (OPN) levels in both plasma and synovial fluid of patients with primary knee osteoarthritis (OA) and to investigate their relationship with severity of the disease.

Patients and methods: Fifty patients with primary knee OA were compared to twenty-five apparently healthy controls. OPN levels in plasma and synovial fluid were measured using enzyme-linked immunosorbent assay. Severity of knee pain was assessed by the Western Ontario and McMaster Universities osteoarthritis index. Radiographic grading of knee OA was performed by Kellgren-Lawrence criteria. Magnetic resonance imaging (MRI) was also performed on painful knees.

Results: Plasma OPN was higher in patients (159.65 ± 28.56 ng/ml) than controls (90.45 ± 23.63 ng/ml). OPN in plasma and synovial fluid was correlated with severity of knee pain (r = 0.878, r = 0.795, P < 0.001). Cartilage loss, marginal osteophytes and subchondral bone cyst were the commonest MRI findings in knee OA. MRI detected also patients with early knee OA that were not detected by plain radiography.

Conclusion: OPN serves as a biochemical marker of disease severity in knee OA. It also could be predictive to the progression of disease.

© 2014 Production and hosting by Elsevier B.V. on behalf of Egyptian Society for Joint Diseases and

Arthritis.

1. Introduction

* Corresponding author. Tel.: +20 1068637029. E-mail address: hala_haider@yahoo.com (H.M. Haider). Peer review under responsibility of Egyptian Society for Joint Diseases and Arthritis.

Osteoarthritis (OA) is the most widespread joint affecting disease characterized by articular cartilage degeneration, subchondral bone sclerosis, osteophyte formation, and synovial inflammation [1].

OA is the most common arthritis of the elderly and may lead to severe symptoms like pain, malformation of the joint and disability [2]. All joints may be affected, but the knee is

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the most clinically significant site of primary OA involvement [3].

Although OA is generally assessed using standard radiographic images in clinical practice, biochemical markers can be used to detect the disease and determine its severity.

Osteopontin (OPN) is an extracellular matrix glycoprotein that is a potential inflammatory cytokine [4]. As the name implies, OPN may have a role in bone metabolism. In vitro, it stimulates the adhesion of osteoclasts to bone, and bone resorption is blocked by inhibition of this interaction [5]. OPN may also contribute directly to the regulation of mineral crystal formation and growth. It binds hydroxy-apatite and suppresses crystal formation both in vitro and in vivo [6,7]. OPN is also a regulator of inflammation. It regulates macrophage differentiation and recruitment [8]. It also functions as a chemotactic factor and co-stimulator of T cells [9].

Plasma OPN concentrations were significantly higher in systemic lupus erythematosus (SLE) patients with renal impairment and in SLE patients than controls. Increase in OPN correlated significantly with SLE disease activity index in all patients. OPN production could be associated with the inflammatory process of SLE development and may serve as a potential disease marker of SLE [10]. Plasma OPN was elevated fourfold in patients with systemic sclerosis (n = 70, 89.1 ± 52.4 ng/ml) compared with healthy controls (n = 21, 23.8 ± 3.7 ng/ml) and 1.4-fold compared with patients with idiopathic pulmonary hypertension (n = 59, 63.4 ± 44.2 ng/ ml). The possibility of using OPN inhibitors as a novel therapeutic target of T-cell chemotaxis could be, because of monoclonal OPN antibodies used with great success in collagen-induced arthritis. Furthermore, OPN measurement would be an attractive tool for early detection of pulmonary fibrosis [11].

The polymorphisms of the OPN gene 443C/T and the —66/ T were significantly associated with the OA risk and radiographic severity in 750 patients with primary knee OA [12]. Dong et al. [13] found that serum OPN and thrombin cleaved OPN to OPN ratio of synovial fluid were correlated with OA severity.

The standard diagnostic investigation is the plain radiograph for knee OA which lacks sensitivity [14]. Magnetic resonance imaging (MRI) detected more cases of knee OA than radiograph as concluded by Schiphof et al. [15]. MRI could detect early structural changes of knee OA besides signs of disease progression.

The aim of the present work was to investigate osteopontin levels in both plasma and synovial fluid of patients with primary knee osteoarthritis and study their relationship with severity of the disease.

2. Patients and methods

Fifty primary knee osteoarthritis female patients were included in the study at the Physical Medicine, Rheumatology and Rehabilitation Department, Ain Shams University Hospitals. The diagnosis of patients met the American College of Rheumatology Criteria for diagnosis of knee OA [16]. Twenty-five apparently healthy females were also enrolled as controls in this study.

The local ethical committee approved this study and an informed consent was obtained from subjects sharing in the study.

2.1. Clinical evaluation

Patients were subjected to full medical history taking and thorough clinical examination with stress on age, weight, height and body mass index (BMI). Knee pain was graded from 0 to 4 (0 = none, 1 = slight, 2 = moderate, 3 = very and 4 = extremely) on the basis of visual analogue scale. This was calculated for five different activities (on walking, stair climbing, nocturnal, rest and weight bearing) quoted from the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [17].

2.2. Radiological assessment

1-Plain radiographs, anteroposterior weight bearing standing position for both knees, were taken. The radiographic grading of OA was performed by using the Kellgren-Lawrence criteria (K-L) [18,19].

2.3. 2-Magnetic resonance imaging (MRI)

MRI was performed with a 1.5 Tesla scanner (Philips Medical Systems, Japan). Images from pulse sequence were used in the assessment of knee OA features: axial, sagittal and coronal fat saturated, proton density weighted dual spin echo images. Evaluation of tibiofemoral joint (tibial plateau, central weight bearing and posterior portions of femoral condyles) was according to the presence or absence of certain features in painful knees. These features include cartilage loss, marginal osteophytes, meniscal lesion, subchondral bone cyst, subchon-dral bone sclerosis, bone marrow edema, synovial effusion, ligamentous abnormalities, Baker's cyst and bone attrition. For statistical purpose, absence of each specific feature was graded zero and its presence was graded one.

2.4. Osteopontin measurement

Osteopontin (OPN) levels in plasma for patients and controls and in synovial fluid for patients only were measured by enzyme-linked immunosorbent assay (ELISA) (Quantkine ELISA kit D 05T00 USA). Plasma samples were collected using EDTA as anticoagulant. The results were expressed in ng/ml relative to standards included in test kit.

Statistical analysis: The collected data were organized and statistically analyzed using SPSS version 18. Range, mean, standard deviation and Student's t test for comparison between two means were calculated for quantitative data. ANOVA test used to compare between more than two groups. Pearson's correlation co-efficient (r) tested the association between two variables.

3. Results

Fifty patients with primary knee OA complained of knee pain and were compared to 25 apparently healthy controls. All patients and controls were female. Their age ranged from

48-78 years with mean ± SD (60.60 ± 9.38) for patients, 4874 years (59.93 ± 8.49) for the control group. Pain grading ranged from 2 to 16 with mean ± SD (9.28 ± 2.64). There was no significant difference between patients and controls in age and BMI (Table 1). Both groups of patients and controls were obese as the mean BMI was 29.62 ± 2.01 and 30.39 ± 1.74 (respectively).

In patients, plasma OPN was 159.65 ± 28.56 ng/ml and was higher in synovial fluid 222.23 ± 41.42 ng/ml. In controls, plasma OPN was 90.45 ± 23.63 ng/ml. OPN in synovial fluid was higher with respect to paired plasma. There was a significant difference between patients and controls as regards the plasma OPN levels (t = 8.534, P < 0.001) as shown in Table 1.

Radiographic data revealed different percentages for K-L scores in knee OA. About 10% of patients were grade G1, 56% G2, 27% G3 (Fig. 1) and 7% G4.

As regards MRI findings, the tibiofemoral compartment was more frequently and more severely involved in OA of knee joint than the patellofemoral compartment and medial tibiofemoral joint was most commonly involved. The most common findings were cartilage damage, marginal osteo-phytes, subchondral bone cyst and bone marrow edema. Cartilage loss of medial tibiofemoral compartment was in about 80% of patients and about 5% had damage of lateral tibiofemoral cartilage. Marginal osteophytes were present in about 74% of patients and subchondral cyst was found in about 52% (Fig. 2A). Bone marrow edema was in about 44% of patients. Subchondral sclerosis was in 32%, synovial effusion in 24% while mensical abnormalities were in about 12% (Fig. 2B) and Baker's cyst was in 16% (Fig. 2C). Ligamentous abnormalities were in about 4% of patients.

Plasma and synovial fluid OPN levels were significantly different with severity of K-L score for knee OA (F = 19.05 for plasma and F = 24.47 for synovial OPN, p < 0.001). Furthermore, OPN levels were significantly different with some MRI features as cartilage loss (t = 9.46 for plasma, t = 5.22 for synovial, p < 0.001), subchondral cyst (t = 23.96, p < 0.001, t = 6.89, p < 0.002), marginal osteophytes (t = 12.80, t = 7.58, P < 0.001) and for synovial effusion (t = 9.51, t = 16.62, p < 0.001). On the other hand, no statistical significant difference in OPN was found for the presence of subchondral sclerosis or meniscal or ligamentous abnormalities.

OPN level in plasma significantly correlated with synovial OPN (r = 0.806, P < 0.001) (Fig. 3). Also, OPN level in both

Figure 1 Anteroposterior radiograph with K-L grade 3 in Rt. Knee in a patient with knee osteoarthritis.

plasma and synovial fluid was significantly correlated with severity of knee pain (r = 0.878, r = 0.795, p < 0.001) (Figs. 4 and 5). No significant correlation was found between plasma or synovial OPN and either age or BMI of the patients (r = 0.119 and r = 0.029 for plasma, r = 0.091 and r = 0.185 for synovial OPN, p > 0.05).

4. Discussion

Osteopontin has been implicated in biological activities, including regulation of mineral crystal formation and growth [6,7]. It also has a regulator role in inflammation as a chemotactic factor and costimulator of T cells [8].

It has been shown that OPN was identified in synovial fluid [20] of patients with rheumatoid arthritis (RA) and in plasma and synovial fluid with knee OA [4]. However, the relationship between OPN levels and disease severity has rarely been specifically determined in patients with knee OA.

OPN was highly detected by immunohistochemistry predominantly in RA synovial lining cells. ELISA also showed a marked increase of OPN levels in synovial fluid of patients with RA and with OA compared to the control plasma OPN levels. The enhanced local production of OPN in rheumatoid joints may be involved in the pathogenesis of RA [21]. In addition, the levels of OPN correlated significantly with

Table 1 Comparison between knee OA patients and controls plasma and synovial fluid (SF). as regards age, body mass index (BMI) and osteopontin (OPN) in

Range Knee OA patients Controls t p-value

(Mean ± SD)

Age (years) 48-78 48-74 0.261 0.795

(60.64 ± 9.38) (59.93 ± 8.49)

BMI (kg/m2) 26.8-34.1 27.3-33 -1.327 0.189

(29.62 ± 2.01) (30.39 ± 1.74)

Plasma OPN 93.6-200.3 49.2-140.3 8.534 <0.001*

(ng/ml) (159.65 ± 28.56) (90.45 ± 23.63)

SF OPN 120-290 -

(ng/ml) (222.23 ± 41.42)

* Significantly different.

Figure 2 MRI of the left knee in a patient with knee osteoarthritis. (A) T1W coronal section shows marginal osteophytes (black plus) and subchondral cyst (white arrow), (B) White arrow in sagittal weighted dual spin shows degenerated oblique tear of the posterior horn of the medial meniscus, (C) Mild synovial effusion and small Baker's cyst.

Figure 3 Correlation between plasma and synovial osteopontin (OPN) level in patients with knee osteoarthritis.

Figure 4 Correlation between plasma osteopontin (OPN) and severity of knee pain in patients with knee osteoarthritis.

interleukin-17 and the frequency of T-helper 17 (Th17) cells in the synovial fluid of RA patients that revealed a critical role of OPN in Th17 differentiation in rheumatoid synovitis [22].

This study showed a marked increase of OPN levels in both plasma and synovial fluid of patients with knee OA compared to control levels. Our findings suggest enhanced local and systemic production of OPN in primary knee OA. The possible mechanism that could explain why OPN levels in synovial fluid were elevated is the release of OPN in extracellular matrix or by increased production. This theory copes with the identification of OPN as an extracellular glycoprotein and as a potential inflammatory cytokine [4]. The elevated values of plasma OPN in OA patients could reflect its release from injured joints.

As OPN levels in plasma and synovial fluid were significantly correlated with severity of knee pain and radiologic progression of the disease either by Kellegren-Lawrence score or MRI findings, measurements of plasma and/or synovial levels of OPN could possibly serve as a biochemical parameter for determining disease severity. It might be also a predictive of prognosis with respect to the progression of the osteoarthritic disease process. Additional studies may provide further information regarding the value of OPN as a potential marker to monitor the course of OA.

These findings are supported by Honsawek et al. [23] and Mohammed et al. [24] studies who had suggested that OPN in plasma and synovial fluid was related to progressive joint damage in knee OA using the Kellgren-Lawrence criteria.

r=0.795

p<0.001

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im an ai

Synoviai fluid Osteopontin (ng^ml)

Figure 5 Correlation between synovial fluid osteopontin (OPN) and severity of knee pain in patients with knee osteoarthritis.

Another study [25] found higher OPN levels in synovial fluid and articular cartilage in fifty patients compared to ten healthy controls. It was associated with progressive joint damage by using K-L criteria and concluded that OPN was likely to be a useful biomarker for determining disease severity and progression in knee OA. In contrast to the previous studies, our study depended on not only K-L criteria but also on pain severity and MRI findings to assess disease severity.

In this study, some patients complained of knee pain and had multiple abnormalities of MRI despite lack of radiographic OA (5 patients, 10% were K-L = 1) which indicates an early stage of Knee OA. It reflects the higher sensitivity of MRI for early detection of knee OA. It seems that majority of MRI findings in tibiofemoral compartment of knee joint and K-L scores were well correlated. This finding is supported by Joshi et al. study [26] who found that increasing K-L scores were associated with more frequent and more severe defects of cartilage, bone marrow edema, osteophytes, subchondral cysts and sclerosis in tibiofemoral compartments besides joint effusion and presence of meniscal tears. They concluded that those findings reinforce the evolving concept that knee OA is a whole organ disease and MRI imaging is capable of showing the bone and soft tissue evidence of knee OA at an early stage. Further study by Schiphof et al. [15] recorded that definition of tibiofemoral OA by MRI is more sensitive in detecting structural knee OA.

It is noticed from our study that older age group had more abnormalities of all types of MRI lesions. Otherwise, cartilage loss and marginal osteophytes were the commonest MRI findings and subchondral bone cyst and bone marrow edema were common in about half of patients. In an interesting study, Guermazi et al. [27] stated that changes which were indicative of OA were commonly present in the knees of most people aged fifty and above who have no radiographic evidence of tibiofemoral OA. Osteophytes, cartilage damage and bone marrow edema were common in either painful or painless knees that represented an early stage OA. Another study [28] found that bone marrow lesions (BMLs) detected by MRI were highly prevalent in elderly Asian population (N = 358). BMLs were significantly correlated with knee pain severity. On the same point, Hunter et al. [29] found that BMLs were

unlikely to resolve and often got larger overtime. Enlarging BMLs were strongly associated with more cartilage loss. Some studies detected a role of OPN in knee OA following rupture of cruciate ligaments. Yamaga et al. [30] found after a month of anterior cruciate ligament rupture both OPN full length and N-terminal fragment (N-half) levels in SF of patients were positively correlated with severity of joint pain. They suggested that OPN full and N-half had distinct functions in articular cartilage homeostasis and in human joint pain. Another study in vitro, thrombin-cleaved OPN levels in SF were elevated four weeks after posterior cruciate ligament transection in rabbit model. The OPN peaking was at 24 weeks after surgery (p < 0.00001). They concluded that thrombin cleaved OPN in SF provided a useful marker of OA disease severity and progression [31].

It should be pointed out that a limitation of this study is the effect of joint sites other than the knee need to be taken into account. However, this limitation decreased as patients mainly complained of knee pain. Furthermore, the female predominance of patients with OA may lead to a potential bias in comparing the levels of OPN because controlled data obtained from a large sample size are currently not available.

In summary, patients with primary knee OA have elevated levels of plasma OPN compared to healthy controls. We performed this study with the goal of relating plasma and synovial fluid OPN levels to the progression of knee OA. Plasma OPN was significantly correlated with synovial OPN and both were correlated to severity of knee pain and magnitude of OA radiographic and MRI progression.

In conclusion osteopontin measurement may serve as a biochemical marker of disease severity of primary knee OA in female Egyptian patients. It also could be predictive to the progression of knee OA. Further longitudinal investigations are warranted to elucidate the influence of OPN on disease outcome.

Conflict of interest

No conflict of interest to declare. References

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