Dickkopf-1 (Dkk-1) in plasma and synovial fluid is inversely correlated with radiographic severity of knee osteoarthritis patients

<p>Abstract</p> <p>Background</p> <p>Osteoarthritis (OA) is a common degenerative joint disease causing pain, stiffness, reduced motion, swelling, crepitus, and disability. Dickkopf-1 (Dkk-1) is a critical mediator of osteoblastogenesis and regulates the joint remodeling. The aim of this study was to examine plasma and synovial fluid Dkk-1 levels of patients with primary knee OA and to investigate their relationship with disease severity.</p> <p>Methods</p> <p>Thirty-five patients aged 55-83 years with knee OA and 15 healthy individuals were recruited into this study. Disease severity was determined using weight-bearing anteroposterior radiographs of the affected knee. The radiological grading of OA in the knee was performed according to the Kellgren-Lawrence grading system. Dkk-1 levels in both plasma and synovial fluid were evaluated using enzyme-linked immunosorbent assay.</p> <p>Results</p> <p>The average concentration of circulating Dkk-1 in the knee OA patients was remarkably lower than that of healthy controls (396.0 ± 258.8, 95%CI 307.1-484.9 vs 2348.8 ± 2051.5, 95%CI 1164.3-3533.3 pg/ml, p < 0.0001). Dkk-1 levels in synovial fluid were significantly lower than in paired plasma samples (58.6 ± 31.8, 95%CI 47.7-69.6 vs 396.0 ± 258.8, 95%CI 307.1-484.9 pg/ml, p < 0.001). Furthermore, both plasma and synovial fluid Dkk-1 levels were inversely correlated with radiographic severity (r = -0.78, p < 0.001 and r = -0.42, p = 0.01, respectively). Plasma Dkk-1 levels were also significantly correlated with synovial fluid Dkk-1 levels (r = 0.72, p < 0.001).</p> <p>Conclusions</p> <p>Dkk-1 levels in plasma and synovial fluid are inversely related to the severity of joint damage in knee OA. Dkk-1 could serve as a biochemical marker for determining disease severity and might play a potential role in the pathogenesis of the degenerative process of OA.</p

Bone cement formulations tested in this project by mixing the poly(methyl methacrylate/methacrylate) powder with different amounts of chitosan or chitosan oligosaccharide.

Bone cement formulations tested in this project by mixing the poly(methyl methacrylate/methacrylate) powder with different amounts of chitosan or chitosan oligosaccharide.</p

Fig 6 -

Zone of inhibition (ZOI) of S. aureus (A) and MRSA (B) of the supernatant obtained from different bone cement specimens that incubated in PBS for 7 days. Control represents bone cement specimens made solely from Copal® G+V. Ch 1%, Ch 5%, and Ch 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan, respectively. ChO 1%, ChO 5%, and ChO 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan oligosaccharides, respectively. Data are expressed as mean ± SEM (n = 6). One-way ANOVA with Dunnett’s multiple comparisons test was performed.</p

Relative cell viability (%) of Saos-2 cells after treatment with extracts from various bone cement samples for 24 h.

Control represents bone cement specimens made solely from Copal® G+V. Ch 1%, Ch 5%, and Ch 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan, respectively. ChO 1%, ChO 5%, and ChO 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan oligosaccharides, respectively. PBS-treated group was considered 100% cell viability. Data are expressed as mean ± SEM (n = 36–41).</p

Fig 1 -

Freshly prepare (A-G) and drug eluted (H-N) bone cements images obtained from a stereomicroscope with 6.7x magnification. Bone cement made solely from Copal® G+V (Control, A and H); Copal® G+V mixed with 1% (Ch 1%: B and I), 5% (Ch 5%: C and J), and 10% (Ch 10%: D and K) w/w chitosan; Copal® G+V mixed with 1% (ChO 1%: E and L), 5% (ChO 5%: F and M), and 10% (ChO 10%: G and N) w/w chitosan oligosaccharides. Scale bar represents 2 mm.</p

Fig 5 -

Cumulative release of gentamicin from bone cement prepared with chitosan (A) and chitosan oligosaccharides (B). Control represents bone cement specimens made solely from Copal® G+V. Ch 1%, Ch 5%, and Ch 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan, respectively. ChO 1%, ChO 5%, and ChO 10% are specimens made of Copal® G+V mixed with 1%, 5% and 10% w/w chitosan oligosaccharides, respectively. Data are expressed as mean ± SEM (n = 3). Two-way ANOVA with Dunnett’s multiple comparisons test was performed. *ppp<0.001.</p

Representative photos of an agar disk diffusion method.

Zone of inhibition (ZOI) of MRSA was measured. Control represents supernatant obtained from bone cement specimens made solely from Copal® G+V (A, D). Ch 10% are supernatant obtained from specimens made of Copal® G+V mixed with 10% w/w chitosan (B, E). ChO 10% are supernatant obtained from specimens made of Copal® G+V mixed with 10% w/w chitosan oligosaccharides (C, F). (TIF)</p

Fig 2 -

SEM micrographs represent bone cement samples obtained after freshly prepared (A-C) and after submerged in PBS for 7 days (D-F). Bone cement made solely from Copal® G+V (Control: A, D); Copal® G+V mixed with 10%w/w chitosan (Ch 10%: B, E); Copal® G+V mixed with 10%w/w chitosan oligosaccharides (ChO 10%: C, F). Scale bar represents 100 μm.</p

Representative photos of an agar disk diffusion method.

Zone of inhibition (ZOI) of S. aureus was measured. Control represents supernatant obtained from bone cement specimens made solely from Copal® G+V (A, D). Ch 10% are supernatant obtained from specimens made of Copal® G+V mixed with 10% w/w chitosan (B, E). ChO 10% are supernatant obtained from specimens made of Copal® G+V mixed with 10% w/w chitosan oligosaccharides (C, F). (TIF)</p

The minimal data set underlying the results.

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