Dorso-ventral osteophytes of interphalangeal joints correlate with cartilage damage and synovial inflammation in hand osteoarthritis: a histological/radiographical study

Objective

To detect dorsally located osteophytes (OP) on lateral x-ray views and to correlate their presence with the extent of structural joint damage, determined by histologic grading (cartilage damage and synovial inflammation) and radiographic scoring in hand osteoarthritis (HOA).

Methods

Distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints were obtained from post mortem specimens (n = 40). Multiplanar plain x-rays were taken (dorso/palmar (dp) and lateral views). Radiographic OA was determined by the Kellgren and Lawrence classification. Joint samples were prepared for histological analysis and cartilage damage was graded according to the Mankin scoring system. Inflammatory changes of the synovial membrane were scored using the general synovitis score (GSS). Spearman’s correlation was applied to examine the relationship between histological and radiographical changes. Differences between groups were determined by Mann-Whitney test.

Results

Bony proliferations that were only detectable on lateral views but reminiscent of OPs on dp images were termed dorso-ventral osteophytes (dvOPs). All joints displaying dvOPs were classified as OA and the presence of dvOPs in DIP and PIP joints correlated with the extent of histological and radiographic joint damage, as well as with patient age. Joint damage in osteoarthritic DIP and PIP joints without any dvOPs was less severe compared to joints with dvOPs. Synovial inflammation was mainly present in joints displaying dvOPs and correlated with joint damage.

Conclusion

dvOPs are associated with increasing structural alterations in DIP and PIP joints and can be seen as markers of advanced joint damage. Detecting dvOPs can facilitate the diagnosis process and improve damage estimation in HOA.

Hand X-ray examination in two planes is not required for radiographic assessment of hand osteoarthritis

AIMS

Radiographic imaging is essential in the diagnosis of hand osteoarthritis (HOA); however, it is unknown whether a multiplanar examination would add essential information to dorso-palmar (dp) views alone. This study evaluated whether an additional radiographic view would aid clinicians in the diagnostic process of HOA.

METHODS

The dp radiographs of both hands from 159 HOA patients were assessed according to the scores described by Kellgren and Lawrence (K/L). In oblique view images, structures similar to classic ostophytes (OPs) were found, namely bony proliferations on the dorsal and/or ventral margins of joints, and were documented as dorsal/ventral OPs (dvOPs). Function and pain were assessed by applying standardised read-out systems. Logistic regression analysis and Mann-Whitney tests were implemented.

RESULTS

The presence of dvOPs was associated with the degree of joint damage; however, dp views were sufficient to estimate radiographic changes. Only a few joints showed dvOPs as the only structural alteration; nevertheless, in almost all cases, classical radiographic OA changes were found in dp views of other joints of the same or the contralateral hand. The presence of dvOPs did not affect joint function or pain according to established scores, but was associated with radiographic progression in distal interphalangeal joints.

CONCLUSION

This is the first study to confirm that additional radiographic planes, oblique/lateral views, are not necessary in the diagnostic process in HOA in daily clinical practice. Nevertheless, the presence of dvOPs reflect more severe joint damage and is associated with radiographic progression in HOA; hence, oblique/lateral views could be a useful tool for academic purposes.

Etanercept in patients with inflammatory hand osteoarthritis (EHOA): a multicentre, randomised, double-blind, placebo-controlled trial

Objective

Hand osteoarthritis is a prevalent disease with limited treatment options. Since joint inflammation is often present, we investigated tumour necrosis factor (TNF) as treatment target in patients with proven joint inflammation in a proof-of-concept study.

Methods

This 1-year, double-blind, randomised, multicentre trial (NTR1192) enrolled patients with symptomatic erosive inflammatory hand osteoarthritis. Patients flaring after non-steroidal anti-inflammatory drug washout were randomised to etanercept (24 weeks 50 mg/week, thereafter 25  mg/week) or placebo. The primary outcome was Visual Analogue Scale (VAS) pain at 24 weeks. Secondary outcomes included clinical and imaging outcomes (radiographs scored using Ghent University Scoring System (GUSS, n=54) and MRIs (n=20)).

Results

Of 90 patients randomised to etanercept (n=45) or placebo (n=45), respectively, 12 and 10 discontinued prematurely. More patients on placebo discontinued due to inefficacy (6 vs 3), but fewer due to adverse effects (1 vs 6). The mean between-group difference (MD) in VAS pain was not statistically significantly different (−5.7 (95% CI −15.9 to 4.5), p=0.27 at 24 weeks; − 8.5 (95% CI −18.6 to 1.6), p=0.10 at 1  year; favouring etanercept). In prespecified per-protocol analyses of completers with pain and inflammation at baseline (n=61), MD was −11.8 (95% CI −23.0 to −0.5) (p=0.04) at 1  year. Etanercept-treated joints showed more radiographic remodelling (delta GUSS: MD 2.9 (95% CI 0.5 to 5.4), p=0.02) and less MRI bone marrow lesions (MD −0.22 (95% CI −0.35 to −0.09), p = 0.001); this was more pronounced in joints with baseline inflammation.

Conclusion

Anti-TNF did not relieve pain effectively after 24 weeks in erosive osteoarthritis. Small subgroup analyses showed a signal for effects on subchondral bone in actively inflamed joints, but future studies to confirm this are warranted.

Pharmacologic treatment of hand-, knee- and hip-osteoarthritis

Osteoarthritis (OA) is a joint disease of high prevalence and affects > 90 % of the population, depending on several risk factors. Symptomatic OA is less frequent, but requires an individually tailored therapeutic regimen consisting of non-pharmacological and pharmacological treatment modalities. Pharmacologic therapy, however, is mainly limited to analgetic and anti-inflammatory agents; structure modifying remedies do not exist. The therapeutic approach to hand-, knee- and hip-OA is basically similar and differs only at some minor points. Generally, topical agents or paracetamol are recommended as first-line agents. If unsuccessful oral non-steroidal anti-inflammatory drugs (NSAIDs) or COX-2-selctive inhibitors should be introduced. Tramadol is an option in the case patients will not respond satisfactorily to NSAIDs. Glucosamine and chondroitine sulphate are no longer recommended in knee and hip OA, but chondroitine might be efficient in treating hand OA. Oral NSAIDs should be prescribed with caution due to potential side effects. Opioids are not recommended as their benefits are outweighed by an increased risk for serious adverse events.

Histopathological correlation supports the use of x-rays in the diagnosis of hand osteoarthritis

OBJECTIVE

To correlate histopathological and radiographic features of distal and proximal interphalangeal (DIP and PIP) joints in order to test whether the use of an x-ray examination would be beneficial to the classification/diagnosis process of hand osteoarthritis (OA).

METHODS

DIP and PIP joints were obtained from post mortem specimens (n=40). Plain x-rays of the DIP and PIP joints were taken and radiographic OA was determined by the Kellgren and Lawrence classification. Individual radiographic features were scored according to the method described by Altman. Joint samples were prepared for histological analysis; cartilage damage was graded according to the Mankin scoring system. Spearman's correlation was applied to examine the relationship between histological and radiographical changes. Differences between groups (bony swelling vs no bony swelling) were determined by Student t test.

RESULTS

A highly significant correlation was found between histological (Mankin score) and radiographic (Kellgren/Lawrence score) changes in the investigated DIP (r(s)=0.87, p<0.0001) and PIP (r(s)=0.79, p<0.0001) joints. A subgroup of patients (37.5% for DIP and 18.8% for PIP joints) showed advanced radiographic changes (Kellgren/Lawrence score ≥2) in joints without clinical bony swelling. Histologically, the mean Mankin scores accounted for 11±1.66 for DIP and 9.67±2.4 for PIP joints.

CONCLUSION

On the basis of histopathological changes of DIP and PIP joints, this investigation demonstrates the validity of x-ray examinations and supports the use of plain radiography in the diagnosis of hand OA and in the classification of hand OA in clinical trials.

Interleukin-1 is essential for systemic inflammatory bone loss

OBJECTIVES

Chronic inflammation is a major risk factor for systemic bone loss leading to osteoporotic fracture and substantial morbidity and mortality. Inflammatory cytokines, particularly tumour necrosis factor (TNF) and interleukin-1 (IL1), are thought to play a key role in the pathogenesis of inflammation-induced bone loss, but their exact roles are yet to be determined.

METHODS

To determine whether TNF directly triggers bone loss or requires IL1, human TNFalpha mice (hTNFtg) were crossed with mice lacking IL1alpha and IL1beta (IL1(-/-)hTNFtg). Systemic bone architecture was evaluated using CT scanning, static and dynamic bone histomorphometry and serum markers of bone metabolism.

RESULTS

hTNFtg mice developed severe bone loss accompanied by a severe distortion of bone microarchitecture. Bone trabeculae were thinner and decreased in numbers, resulting in increased trabecular separation. Histomorphometric analyses revealed strongly increased bone resorption in hTNFtg mice compared with wild-type mice. In contrast, IL1(-/-)hTNFtg mice were fully protected from systemic bone loss despite still developing inflammation in their joints. Lack of IL1 completely reversed increased osteoclast formation and bone resorption in hTNFtg mice and the increased levels of RANKL in these mice. Structural parameters and osteoclast and osteoblast numbers were indistinguishable from wild-type mice.

CONCLUSIONS

These data indicate that IL1 is essential for TNF-mediated bone loss. Despite TNF-mediated inflammatory arthritis, systemic bone is fully protected by the absence of IL1, which suggests that IL1 is an essential mediator of inflammatory osteopenia.

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.

Differentially regulated expression of growth differentiation factor 5 and bone morphogenetic protein 7 in articular cartilage and synovium in murine chronic arthritis: potential importance for cartilage breakdown and synovial hypertrophy

OBJECTIVE

To examine whether the endogenous expression of growth differentiation factor 5 (GDF-5) and bone morphogenetic protein 7 (BMP-7) is altered in the cartilage and synovium of human tumor necrosis factor alpha (TNFalpha)-transgenic (hTNFtg) mice with chronic arthritis, and to investigate the response of hTNFtg chondrocytes as well as fibroblast-like synoviocytes (FLS) to these morphogens in vitro.

METHODS

Analyses were performed in hTNFtg mice with chronic destructive arthritis and in wild-type (WT) mice as controls. Expression of GDF-5 and BMP-7 in the articular cartilage and synovium was examined by real-time polymerase chain reaction and immunohistochemistry. Human TNFtg cartilage explants, chondrocytes, and FLS monolayer cultures were assessed for basal matrix biosynthesis as well as growth factor responsiveness, using (35)S-sulfate incorporation assays. In addition, the DNA content/cell proliferation rate was measured.

RESULTS

The expression of GDF-5 and BMP-7 was decreased in articular cartilage from hTNFtg mice, whereas expression of both morphogens was increased in arthritic synovium from hTNFtg mice, as compared with the levels in WT controls. Isotope incorporation revealed a marked reduction of matrix synthesis in hTNFtg cartilage as well as a decrease in responsiveness to GDF-5 and BMP-7. The DNA content did not change in arthritic cartilage as compared with WT cartilage. In hTNFtg FLS, growth factor stimulation increased the rate of cell proliferation and the production of extracellular matrix.

CONCLUSION

In this murine model of TNFalpha-mediated arthritis, the expression of GDF-5 and BMP-7 is regulated differentially in articular cartilage and synovium. In articular cartilage, the down-regulation of GDF-5 and BMP-7, which function to maintain matrix integrity, could potentially compromise tissue repair, whereas in synovium, the increased expression of GDF-5 and BMP-7 might contribute to synovial hypertrophy.

Age-dependent expression of VEGF isoforms and receptors in the rabbit anterior cruciate ligament

Vascular endothelial growth factor (VEGF) gene gives rise to several distinct isoforms of VEGF. Those isoforms differ in biochemical and biological properties, and it has been reported that their expression patterns are tissue and age specific as well. We investigated the expression levels of VEGF isoforms (VEGF121, VEGF165, VEGF183, VEGF189) and its receptors (VEGFR-1, flt-1 and VEGFR-2, flk-1/KDR) in the anterior cruciate ligament (ACL) of 2- to 3-week-, 2-month-, and 18-month-old New Zealand White rabbits using Sybr green Real-Time RT-PCR. VEGF isoforms and both receptors were expressed in the ACL at all investigated ages. VEGF121 was found to be the most abundant isoform at the ages under investigation, followed by VEGF165, VEGF189 and VEGF183. All isoforms showed decreased expression levels with age, however the larger membrane bound isoforms, VEGF183 and VEGF189, showed the most striking age-associated decrease in expression level. VEGFR-1 expression levels increased with age, while the expression level of VEGFR-2 expression was highest at 2-3 weeks and was significantly lower at 2 and 18 months of age. Distinct age-associated differences in the expression level of VEGF isoforms as well as their receptors suggest differential physiological functions during development, maturation and ageing of the ACL.

Impairment of chondrocyte biosynthetic activity by exposure to 3-tesla high-field magnetic resonance imaging is temporary

The influence of magnetic resonance imaging (MRI) devices at high field strengths on living tissues is unknown. We investigated the effects of a 3-tesla electromagnetic field (EMF) on the biosynthetic activity of bovine articular cartilage. Bovine articular cartilage was obtained from juvenile and adult animals. Whole joints or cartilage explants were subjected to a pulsed 3-tesla EMF; controls were left unexposed. Synthesis of sulfated glycosaminoglycans (sGAGs) was measured by using [³⁵S]sulfate incorporation; mRNA encoding the cartilage markers aggrecan and type II collagen, as well as IL-1β, were analyzed by RT–PCR. Furthermore, effects of the 3-tesla EMF were determined over the course of time directly after exposure (day 0) and at days 3 and 6. In addition, the influence of a 1.5-tesla EMF on cartilage sGAG synthesis was evaluated. Chondrocyte cell death was assessed by staining with Annexin V and TdT-mediated dUTP nick end labelling (TUNEL). Exposure to the EMF resulted in a significant decrease in cartilage macromolecule synthesis. Gene expression of both aggrecan and IL-1β, but not of collagen type II, was reduced in comparison with controls. Staining with Annexin V and TUNEL revealed no evidence of cell death. Interestingly, chondrocytes regained their biosynthetic activity within 3 days after exposure, as shown by proteoglycan synthesis rate and mRNA expression levels. Cartilage samples exposed to a 1.5-tesla EMF remained unaffected. Although MRI devices with a field strength of more than 1.5 T provide a better signal-to-noise ratio and thereby higher spatial resolution, their high field strength impairs the biosynthetic activity of articular chondrocytes in vitro. Although this decrease in biosynthetic activity seems to be transient, articular cartilage exposed to high-energy EMF may become vulnerable to damage.

Toll-like receptors and chondrocytes: The lipopolysaccharide-induced decrease in cartilage matrix synthesis is dependent on the presence of toll-like receptor 4 and antagonized by bone morphogenetic protein 7

OBJECTIVE

To assess the presence of Toll-like receptors (TLRs) 1-9 in human articular cartilage, and to investigate the effects of lipopolysaccharide (LPS)-induced activation of TLR-4 on biosynthetic activity and matrix production by human articular chondrocytes.

METHODS

TLRs 1-9 were assessed in human articular cartilage by reverse transcription-polymerase chain reaction (RT-PCR); TLR-4 was also analyzed by Western blotting and immunohistochemistry. Articular chondrocytes were isolated from human donors and from wild-type or TLR-4(-/-) mice. Chondrocyte monolayer cultures were incubated with interleukin-1beta (IL-1beta) and LPS in the absence or presence of bone morphogenetic protein 7 (BMP-7) and IL-1 receptor antagonist (IL-1Ra). Neosynthesis of sulfated glycosaminoglycans (sGAG) was measured by (35)S-sulfate incorporation. Endogenous gene expression of cartilage markers as well as IL-1beta was examined using RT-PCR. The involvement of p38 kinase or p44/42 kinase (ERK-1/2) in LPS-mediated TLR-4 signaling was investigated by immunoblotting, RT-PCR, and sGAG synthesis.

RESULTS

TLRs 1-9 were found on the messenger RNA (mRNA) level in human articular chondrocytes. The presence of TLR-4 was also observed on the protein level. In murine and human articular chondrocytes, but not in chondrocytes derived from TLR-4(-/-) mice, stimulation with LPS resulted in a decrease in total proteoglycan synthesis. IL-1beta mRNA expression was increased by TLR-4 activation, whereas expression of aggrecan and type II collagen was significantly decreased. The presence of BMP-7 and IL-1Ra antagonized the anti-anabolic effects of LPS. Blocking of p38, but not ERK-1/2, resulted in inhibition of both LPS-mediated IL-1beta gene expression and the negative effects of LPS on matrix biosynthesis.

CONCLUSION

These data demonstrate the presence of TLRs in human articular cartilage. The suppressive effects of LPS on cartilage biosynthetic activity are dependent on the presence of TLR-4, are governed, at least in part, by an up-regulation of IL-1beta, and are mediated by p38 kinase. These in vitro data indicate an anti-anabolic effect of TLR-4 in articular chondrocytes that may hamper cartilage repair in various joint diseases.

Effect of pulsed electromagnetic fields on proteoglycan biosynthesis of articular cartilage is age dependent

OBJECTIVE

To investigate the effects of a pulsed electromagnetic field (EMF) on articular cartilage matrix biosynthesis with regard to age and cartilage damage using a matrix depleted cartilage explant model.

METHODS

Cartilage explants were obtained from metacarpophalangeal joints of calves and adult cows. After depletion of the extracellular matrix by trypsin digestion, samples were maintained in serum-free basal medium with and without the addition of interleukin 1beta (IL1beta). Half the samples were subjected to an EMF for 24 minutes daily; the other half were left untreated. Undigested and untreated explants served as negative controls. After 7 days, biosynthesis of matrix macromolecules was assessed by [35S]sulphate incorporation and values were normalised to hydroxyproline content.

RESULTS

The EMF increased matrix macromolecule synthesis in undigested, untreated explants (p<0.009). In matrix depleted samples the EMF had no stimulatory effect on proteoglycan biosynthesis. IL1beta significantly decreased the de novo synthesis of matrix macromolecules (p<0.00004) in young and adult samples, but an EMF partly counteracted this inhibitory effect in cartilage samples from young, but not old animals.

CONCLUSION

EMF promoted matrix macromolecule biosynthesis in intact tissue explants but had no stimulatory effect on damaged articular cartilage. The supressive effects of IL1beta were partially counteracted by EMF exposure, exclusively in cartilage derived from young animals. An EMF has age dependent chondroprotective but not structure modifying properties when cartilage integrity is compromised.

Activation of p38 MAPK is a key step in tumor necrosis factor-mediated inflammatory bone destruction

OBJECTIVE

To investigate whether activation of p38 MAPK is a crucial signaling factor in inflammatory bone destruction mediated by tumor necrosis factor (TNF). Mice overexpressing TNF were treated with 2 different inhibitors of p38 MAPK, and the effect of this treatment on joint inflammation and structural damage was assessed.

METHODS

Human TNF-transgenic mice received systemic treatment with 2 different p38 MAPK inhibitors (RO4399247 and AVE8677). Treatment was started at the time of symptom onset and lasted for 6 weeks. Mice were assessed for clinical signs of arthritis, bone erosion, and cartilage damage. In addition, the effect of these inhibitors on osteoclast generation in vitro and in vivo was assessed.

RESULTS

Both p38 MAPK inhibitors significantly reduced clinical signs of TNF-mediated arthritis. This was attributable to reducing synovial inflammation by 50% without affecting the cellular composition of the infiltrate. Synovial expression of interleukin-1 and RANKL was reduced upon p38 MAPK blockade, and activation of the molecular target MAPK-activated protein kinase 2 (MAPKAP-2) was also inhibited. Proteoglycan loss of articular cartilage was reduced by 50%, although p38 MAPK inhibition did not change matrix molecule synthesis by cultivated chondrocytes. Importantly, bone loss was almost completely prevented by p38 MAPK inhibition. The numbers of synovial osteoclasts and precursors were dramatically reduced, and both p38 MAPK inhibitors also inhibited in vitro osteoclastogenesis at micromolar concentrations and blocked activation of MAPKAP-2 as well as differentiation markers in cultured osteoclast precursors.

CONCLUSION

These results suggest the major importance of p38 MAPK for TNF-mediated inflammatory bone destruction in arthritis and suggest that inhibition of p38 MAPK might be an important tool for reducing structural damage in rheumatoid arthritis.

Stimulatory effects of distinct members of the bone morphogenetic protein family on ligament fibroblasts

OBJECTIVE

To investigate effects of cartilage derived morphogenetic protein-1 and -2 (CDMP-1, CDMP-2), bone morphogenetic protein (BMP)-7 and BMP-6 on metabolism of ligament fibroblasts and their osteogenic or chondrogenic differentiation potential.

METHODS

Ligament fibroblasts were obtained from 3 month old calves, plated as monolayers or micromass cultures, and incubated with or without CDMP-1, CDMP-2, BMP-7, and BMP-6. Expression of the indicated growth factors was assessed by RT-PCR and western immunoblotting. The presence of their respective type I and II receptors, and lineage related markers, was investigated in stimulated and unstimulated cells by RT-PCR and northern blotting. Biosynthesis of matrix proteoglycans was assessed by [(35)S]sulphate incorporation in monolayers. Alcian blue and toluidine blue staining was done in micromass cultures.

RESULTS

CDMP-1, CDMP-2, BMP-7, and BMP-6 were detected on mRNA and on the protein level. Type I and II receptors were endogenously expressed in unstimulated ligament fibroblasts. The growth factors significantly stimulated total proteoglycan synthesis as assessed by [(35)S]sulphate incorporation. Toluidine blue staining showed cartilage-specific metachromasia in the growth factor treated micromass cultures. Transcription analysis of stimulated ligament fibroblasts demonstrated coexpression of chondrocyte markers but no up regulation of osteogenic markers.

CONCLUSION

CDMP-1, CDMP-2, BMP-7, and BMP-6 and their receptors were expressed in ligament tissue. These growth factors induced matrix synthesis in fibroblasts derived from bovine ligament. The preferential expression of cartilage markers in vitro suggests that CDMP-1, CDMP-2, BMP-7, and BMP-6 have the potential to induce differentiation towards a chondrogenic phenotype in ligament fibroblasts. Thus, fibroblasts from ligaments may serve as a source for chondrogenesis and tissue repair.

Chondrocyte number and proteoglycan synthesis in the aging and osteoarthritic human articular cartilage

OBJECTIVE

To correlate the number of chondrocytes in healthy and osteoarthritic human articular cartilage with age, and to evaluate the influence of donor age on total proteoglycan synthesis.

METHODS

Chondrocytes were isolated from human articular cartilage derived from hip joints with and without osteoarthritic lesions. The cell number was normalised to cartilage sample wet weight. In addition, the influence of age on chondrocyte numbers was assessed histomorphometrically. Chondrocytes were grown as monolayer cultures for seven days in a chemically defined serum-free basal medium. Total proteoglycan synthesis was measured by [(35)S]sulphate incorporation into newly synthesised macromolecules.

RESULTS

Chondrocyte numbers in healthy cartilage decreased significantly with advancing age (r = -0.69, p<0.0001). In contrast to healthy specimens, chondrocyte numbers were decreased in osteoarthritic cartilage irrespective of and unrelated to age, and differed markedly, by an average of 38%, from the cell numbers found in healthy individuals (p<0.0001). Regarding synthesis of matrix macromolecules, no dependence on patients' age, either in healthy or in osteoarthritic specimens, could be observed.

CONCLUSIONS

Under the experimental conditions employed, chondrocytes from healthy and osteoarthritic joints synthesised comparable amounts of cartilage macromolecules, independent of age or underlying osteoarthritic disease. Thus the decrease in chondrocyte number in aging and osteoarthritic joints could be a crucial factor in limiting tissue replenishment.

Is pro-matrix metalloproteinase-3 a marker for posttraumatic cartilage degradation?

OBJECTIVE

Since the development of posttraumatic osteoarthritis (OA) is a relatively slow process, estimation of OA risk would be of value with regard to chondroprotective measures and medication. In this study we investigated the significance of pro-matrixmetalloproteinase-3 (proMMP-3) for this purpose.

DESIGN

Synovial fluid (SF) and serum samples were collected from 259 patients of our trauma clinic at the time of arthroscopy. The extent of cartilage damage was assessed according to the Outerbridge-score. ProMMP-3 levels in SF and serum were determined by enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody. Additionally we determined SF and serum levels of total MMP-3 and COMP levels as well as TIMP-1 and -2 concentrations in 40 randomly selected patients by ELISA.

RESULTS

Serum proMMP-3 levels of the total cohort were markedly increased compared to healthy controls (P<0.007). The comparison of serum and SF lavage proMMP-3 concentrations showed a significant correlation (r(s)=0.41, P<0.0001), however, only 26% of the investigated samples were increased above normal ranges. The grade of cartilage damage did not correlate with enzyme concentration neither in patients' serum nor in SF samples. ProMMP-3 SF concentration was increased early after trauma. Furthermore, proMMP-3 correlated significantly with total MMP-3 serum and SF levels as well as COMP SF levels.

CONCLUSIONS

The measurement of proMMP-3 in serum or SF did not reflect the present cartilage damage and thus appears to have only minor potential for clinical use, but it should be considered for longitudinal studies, since it may reflect a risk for cartilage degradation in a subset of patients.

Expression of bone morphogenetic protein 6 in healthy and osteoarthritic human articular chondrocytes and stimulation of matrix synthesis in vitro

OBJECTIVE

To elucidate the role of bone morphogenetic protein 6 (BMP-6) in human articular cartilage, we investigated whether BMP-6 is expressed in adult human articular chondrocytes and analyzed the potential stimulatory effects of BMP-6 on these cells. In addition, we investigated whether osteoarthritic (OA) and normal cartilage chondrocytes behave differently.

METHODS

Endogenous expression of the BMP-6 gene was examined by reverse transcription-polymerase chain reaction. BMP-6 protein was detected by Western immunoblotting. Chondrocytes were grown as monolayer cultures for 7 days in a chemically defined serum-free medium, in the absence or presence of recombinant BMP-6. Proteoglycan (PG) synthesis was measured by (35)S-sulfate incorporation into newly synthesized macromolecules. Cell proliferation was assessed by (3)H-thymidine incorporation.

RESULTS

BMP-6 was expressed in both healthy and OA chondrocytes at the messenger RNA and protein levels. Total PG synthesis was significantly increased after BMP-6 stimulation of healthy (mean +/- SEM 191 +/- 11%; P < 0.001) and OA (150 +/- 25%; P < 0.03) chondrocyte cultures. A direct comparison between healthy and OA samples revealed no significant difference. The proliferation rates of normal and OA chondrocytes were not affected by BMP-6 treatment.

CONCLUSION

BMP-6 is endogenously expressed in chondrocytes obtained from OA and normal adult human articular cartilage. Furthermore, BMP-6 has the potential to stimulate total PG synthesis in human articular chondrocytes derived from normal as well as OA joints. We conclude that the presence of BMP-6 in adult human articular cartilage indicates a functional role for this growth factor in the maintenance of joint integrity.

BMP-6-induced osteogenic differentiation of mesenchymal cell lines is not modulated by sex steroids and resveratrol

Bone morphogenetic protein-6 (BMP-6) is a potent inducer of osteogenic differentiation and its expression is stimulated by 17beta-estradiol. The existence of a regulatory loop between sex steroids and BMP-6 is therefore reasonable to hypothesize. Here we determined whether the sex steroids 17beta-estradiol and dihydrotestosterone, and the phytoestrogen resveratrol can modulate BMP-6-induced alkaline phosphatase activity and osteocalcin expression. Mesenchymal cells of murine (osteoblastic MC3T3-E1 cells, preadipogenic ST2 cells, prechondrogenic ATDC5 cell) and human origin (osteosarcoma SaOS and HOS cells, primary bone marrow stromal cells) were cultured in the presence of recombinant BMP-6 under serum-free conditions. BMP-6 dose-, and time-dependently increased alkaline phosphatase activity in murine cell lines, but not in human cells. Osteocalcin expression was also increased upon stimulation with BMP-6. The presence of 17beta-estradiol, dihydrotestosterone, and resveratrol had no effect on BMP-6-induced alkaline phosphatase activity and osteocalcin expression. These data suggest that osteogenic differentiation in response to BMP-6 occurs independent of steroid hormones and resveratrol in mesenchymal cells that express basal receptor levels.

Tc-99m-labeled human polyclonal immunoglobulin G (HIG) scintigraphy in Sjögren's syndrome

OBJECTIVE

To evaluate the usefulness of Tc-99m-HIG scintigraphy in patients with Sjögren's syndrome.

METHODS

Twelve consecutive patients with verified secondary Sjögren's syndrome were included in this prospective study. The control group consisted of seven patients with Lupus erythematosus; none of them showed clinical signs of Sjögren's syndrome. Planar and SPECT images of the head were performed six hours after i.v. administration of Tc-99m HIG.

RESULTS

Eleven out of twelve patients with secondary Sjögren's syndrome showed a positive result, while one was false negative. Tracer accumulation in patients with positive scintigraphy varied. All patients of the control group were negative.

CONCLUSION

Our data in a limited number of patients suggest that Tc-99m HIG scintigraphy could be a modality with high sensitivity and specificity for the diagnosis of Sjögren's syndrome and can provide objective information on the severity of the disease.

Cartilage-derived morphogenetic protein-1 and -2 are endogenously expressed in healthy and osteoarthritic human articular chondrocytes and stimulate matrix synthesis

OBJECTIVE

We investigated whether chondrocytes derived from osteoarthritic cartilage may lose their responsiveness to cartilage-derived morphogenetic protein-1, -2 (CDMP-1, -2) and osteogenic protein-1 (OP-1) compared with healthy cells, thus leading to an impaired maintenance of matrix integrity.

DESIGN

Chondrocytes were isolated from articular cartilage from patients with and without osteoarthritic lesions. Cells were grown as monolayer cultures for 7 days in a chemically defined serum-free basal medium (BM) in the presence of recombinant CDMP-1, -2, and OP-1. Glycosaminoglycan synthesis was measured by [35S]Sulfate incorporation into newly synthesized macromolecules. Cell proliferation was investigated by [3H]Thymidine incorporation. The endogenous gene expression of CDMPs/OP-1 and their respective type I and type II receptors was examined using RT-PCR. The presence of CDMP proteins in tissue and cultured cells was detected by Western immunoblots.

RESULTS

mRNAs coding for CDMPs and their respective receptors are endogenously expressed not only in healthy, but also in osteoarthritic cartilage. CDMP proteins are present in both normal and osteoarthritic articular cartilage and cultured chondrocytes. CDMP-1, CDMP-2 and OP-1 markedly increased glycosaminoglycan synthesis in both healthy (P< 0.01) and osteoarthritic (P< 0.05) human articular chondrocytes. A comparison of the glycosaminoglycan biosynthetic activity between healthy and osteoarthritic samples revealed no detectable difference, neither in stimulated nor in unstimulated cultures. [(3)H]Thymidine incorporation showed that CDMPs/OP-1 did not affect cell proliferation in vitro.

CONCLUSION

CDMPs and OP-1 exert their anabolic effects on both healthy and osteoarthritic chondrocytes indicating no loss in responsiveness to these growth factors in OA. The endogenous expression of CDMPs/OP-1 and their receptors suggest an important role in cartilage homeostasis.

[The effect of Condrosulf (sodium chondroitin sulfate) on proteoglycan synthesis by human osteoarthritic an bovine juvenile articular cartilage chondrocytes--an in vitro study]

BACKGROUND

Sodiumchondroitinsulfate, Condrosulf, is used in osteoarthritis therapy and belongs to the group of symptomatic slow-acting drugs for osteoarthritis. The aim of this study was to investigate the effects of Condrosulf on total proteoglycan synthesis and cell proliferation in human osteoarthritis and healthy juvenile bovine chondrocytes in vitro.

METHODS

Chondrocytes were grown as monolayers and stimulated for 7 (human cartilage), or 4, 8 and 12 days (bovine cartilage) with different concentrations of Condrosulf (100 micrograms/ml, 500 micrograms/ml, 1000 micrograms/ml, 2500 micrograms/ml and 5000 micrograms/ml). Proteoglycan synthesis was measured by [35S]Sulfate incorporation. The cell proliferation rate was determined using a [3H]Thymidin assay. The expression of the cartilage markers aggrecan and collagen type II was assessed by Northern blot analysis.

RESULTS

We show that the incubation with Condrosulf did not affect proteoglycan synthesis neither in osteoarthritis, nor in healthy chondrocytes under the present culture conditions. Cell proliferation rate was also not increased by Condrosulf stimulation. The results of the Northern blot assays demonstrated a dose-dependent down regulation of aggrecan expression on mRNA level.

CONCLUSIONS

These data indicate a lack of direct anabolic effects of Condrosulf on the biosynthetic activity of cultured articular chondrocytes. The well known ease of clinical symptoms, such as pain or swelling under Condrosulf medication may be interpreted by an interaction with pro-inflammatory cytokines.

Effects of cartilage-derived morphogenetic proteins and osteogenic protein-1 on osteochondrogenic differentiation of periosteum-derived cells

Localization studies and genetic evidence have implicated cartilage-derived morphogenetic proteins-1, -2 (CDMP-1 and CDMP-2), and osteogenic protein-1 (OP-1) in the osteochondrogenic differentiation of mesenchymal progenitor cells during embryonic development and in postnatal life. Based on their expression pattern and the evidence that periosteum contains mesenchymal cells in the cambium layer that can undergo bone and cartilage formation, we hypothesized that CDMPs and OP-1 may be involved in long bone development and fracture healing. To test this hypothesis, periosteum-derived cells from young calves were cultured as monolayers under serum-free conditions with and without the addition of recombinant CDMP-1, CDMP-2 and OP-1. Phenotypic analysis indicate that periosteum-derived cell populations prepared, expanded, and cultured under the conditions described below, constitutively express messenger RNAs for the bone markers osteocalcin, osteopontin and collagen type I, and the chondrogenic markers collagen type II and aggrecan as determined by RT-PCR. Moreover, histologic examinations showed positive staining for alcian blue and alkaline phosphatase (AP). Treatment of periosteum-derived cells with CDMPs and OP-1 resulted in a dose-dependent increase of cell proliferation; CDMP-2 was less active in this regard. Furthermore, all growth factors enhanced osteogenic differentiation as assessed by a time- and dose-dependent stimulation of AP activity and OP-1 increased messenger RNA expression for osteocalcin and collagen type I. We further examined the effects of CDMPs and OP-1 on chondrogenic differentiation of periosteum-derived cells. Both CDMPs and OP-1 stimulated (35)S-sulfate incorporation into newly synthesized macromolecules with OP-1 having a more pronounced stimulatory effect when compared with CDMP-1 and CDMP-2. Our results indicate that distinct members of the BMP-family increase the mitotic and metabolic activity of periosteum-derived cells. The enhancement of both the chondrogenic and osteogenic differentiation suggests that these growth factors might contribute to the local regulation of bone formation and fracture repair.