Cartilage Collagen Degradation Research Articles

Evaluation of enzymatic proteoglycan loss and collagen degradation in human articular cartilage using ultrashort echo time-based biomarkers: A feasibility study.

The objective of the current study was to investigate the feasibility of quantitative 3D ultrashort echo time (UTE)-based biomarkers in detecting proteoglycan (PG) loss and collagen degradation in human cartilage. A total of 104 cartilage samples were harvested for a trypsin digestion study (n = 44), and a sequential trypsin and collagenase digestion study (n = 60), respectively. Forty-four cartilage samples were randomly divided into a trypsin digestion group (tryp group) and a control group (phosphate-buffered saline [PBS] group) (n = 22 for each group) for the trypsin digestion experiment. The remaining 60 cartilage samples were divided equally into four groups (n = 15 for each group) for sequential trypsin and collagenase digestion, including PBS + Tris (incubated in PBS, then Tris buffer solution), PBS + 30 U col (incubated in PBS, then 30 U/ml collagenase [30 U col] with Tris buffer solution), tryp + 30 U col (incubated in trypsin solution, then 30 U/ml collagenase with Tris buffer solution), and tryp + Tris (incubated in trypsin solution, then Tris buffer solution). The 3D UTE-based MRI biomarkers included T1 , multiecho T2 *, adiabatic T1ρ (AdiabT1ρ ), magnetization transfer ratio (MTR), and modeling of macromolecular proton fraction (MMF). For each cartilage sample, UTE-based biomarkers (T1 , T2 *, AdiabT1ρ , MTR, and MMF) and sample weight were evaluated before and after treatment. PG and hydroxyproline assays were performed. Differences between groups and correlations were assessed. All the evaluated biomarkers were able to differentiate between healthy and degenerated cartilage in the trypsin digestion experiment, but only T1 and AdiabT1ρ were significantly correlated with the PG concentration in the digestion solution (p=0.004 and p= 0.0001, respectively). In the sequential digestion experiment, no significant differences were found for T1 and AdiabT1ρ values between the PBS + Tris and PBS + 30 U col groups (p=0.627 and p= 0.877, respectively), but T1 and AdiabT1ρ values increased significantly in the tryp + Tris (p=0.031 and p= 0.024, respectively) and tryp + 30 U col groups (both p<0.0001). Significant decreases in MMF and MTR were found in the tryp + 30 U col group compared with the PBS + Tris group (p=0.002 and p= 0.001, respectively). It was concluded that AdiabT1ρ and T1 have the potential for detecting PG loss, while MMF and MTR are promising for the detection of collagen degradation in articular cartilage, which could facilitate earlier, noninvasive diagnosis of osteoarthritis.

A novel serological pharmacodynamic biomarker assessing type II collagen degradation in osteoarthritis patients

Purpose: A major hallmark of osteoarthritis (OA) is the altered cartilage metabolism and turnover. During cartilage erosion, type II collagen is cleaved by matrix metalloproteinases (MMPs) generating new protein fragments, called neo-epitopes. These fragments are released into the circulation and may reflect disease activity, and potentially be utilized for drug development as pharmacodynamic markers. Currently, there is a lack of type II collagen biomarkers reflecting pharmacologic responses to therapeutic interventions in OA. A novel immunoassay detecting a neo-epitope fragment of type II collagen (T2CM), cleaved by MMP-1 and MMP-13, has recently been developed. The assay is shown to be technically robust and highly specific for the T2CM neo-epitope. Studies have indicated that MMP-13 plays a critical role in type II collagen degradation in articular cartilage in OA and hence, T2CM may serve as a potential pharmacodynamic biomarker candidate in OA. The aim of this study was to evaluate the pharmacodynamic property of T2CM in OA patients treated with oral salmon calcitonin compared to placebo. Methods: T2CM levels were assessed in serum samples in a subset of the SMC study, a randomized, double-blind, multi-center, placebo-controlled study where knee OA patients (n=50) received 0.8 mg oral salmon calcitonin treatment twice daily for 24 months and compared to placebo (n=57). Serum samples were collected at baseline and after 1, 6, 12, and 24 months of treatment. Study samples were collected after informed consent and approved by local ethical committee in compliance with the Helsinki declaration of 1997. The statistical analysis included two-way ANOVA with Sidak’s post hoc test for difference between multiple comparisons of T2CM levels between the OA patients receiving salmon calcitonin treatment and placebo. Data were adjusted for differences in body mass index (BMI), sex, and age. Results: The mean age of OA patients treated with oral salmon calcitonin was 63.9 years (±SD 6.9) and 34% were female, and mean age of the placebo group was 63.1 years (±SD 6.1) and 45% female. The mean BMI of the treatment group and placebo was 30.2 (SD±5.1) and 27.9 (SD±3.3), respectively. T2CM levels were significantly decreased in OA patients receiving salmon calcitonin compared to the placebo group after 1, 6, and 24 months of treatment (p=0.0285; mean -61.49 ±SD 9.10 vs -33.19 ±SD 8.50, p=0.084; mean -66.35 ±SD 8.90 vs -41.46 ±SD 8.31, p=0.0035; mean -61.73 ±SD 9.49 vs -22.19 ±SD 8.76) (Fig.1). Conclusions: The novel T2CM assay measured significantly decreased levels of T2CM in OA patients treated with salmon calcitonin compared to placebo. This suggests that T2CM may have potential as a pharmacodynamic biomarker for type II collagen degradation. Currently, no disease-modifying drugs exist in OA. A validated pharmacodynamic biomarker for type II collagen degradation could promote the development of new disease-modifying OA drugs targeting cartilage repair or degradation.

Periostin interaction with discoidin domain receptor-1 (DDR1) promotes cartilage degeneration.

Osteoarthritis (OA) is characterized by progressive loss of articular cartilage accompanied by the new bone formation and, often, a synovial proliferation that culminates in pain, loss of joint function, and disability. However, the cellular and molecular mechanisms of OA progression and the relative contributions of cartilage, bone, and synovium remain unclear. We recently found that the extracellular matrix (ECM) protein periostin (Postn, or osteoblast-specific factor, OSF-2) is expressed at high levels in human OA cartilage. Multiple groups have also reported elevated expression of Postn in several rodent models of OA. We have previously reported that in vitro Postn promotes collagen and proteoglycan degradation in human chondrocytes through AKT/β-catenin signaling and downstream activation of MMP-13 and ADAMTS4 expression. Here we show that Postn induces collagen and proteoglycan degradation in cartilage by signaling through discoidin domain receptor-1 (DDR1), a receptor tyrosine kinase. The genetic deficiency or pharmacological inhibition of DDR1 in mouse chondrocytes blocks Postn-induced MMP-13 expression. These data show that Postn is signaling though DDR1 is mechanistically involved in OA pathophysiology. Specific inhibitors of DDR1 may provide therapeutic opportunities to treat OA.

Recent advances in understanding the regulation of metalloproteinases.

Metalloproteinases remain important players in arthritic disease, in part because members of this large enzymatic family, namely matrix metalloproteinase-1 (MMP-1) and MMP-13, are responsible for the irreversible degradation of articular cartilage collagen. Although direct inhibition of MMPs fell out of vogue with the initial clinical disappointment of the first generation of compounds, interest in other mechanisms that control these important enzymes has always been maintained. Since these enzymes are critically important for tissue homeostasis, their expression and activity are tightly regulated at many levels, not just by direct inhibition by their endogenous inhibitors the tissue inhibitors of metalloproteinases (TIMPs). Focussing on MMP-13, we discuss recent work that highlights new discoveries in the transcriptional regulation of this enzyme, from defined promoter functional analysis to how more global technologies can provide insight into the enzyme’s regulation, especially by epigenetic mechanisms, including non-coding RNAs. In terms of protein regulation, we highlight recent findings into enzymatic cascades involved in MMP-13 regulation and activation. Importantly, we highlight a series of recent studies that describe how MMP-13 activity, and in fact that of other metalloproteinases, is in part controlled by receptor-mediated endocytosis. Together, these new discoveries provide a plethora of novel regulatory mechanisms, besides direct inhibition, which with renewed vigour could provide further therapeutic opportunities for regulating the activity of this class of important enzymes.

The Changes in Matrix Metalloproteinases and Collagens Expression of Rat Articular Cartilage after Continuous Mandibular Advancement: Immunohistochemical Study

Condylar growth modification is induced by mandibular advancement though the changes in Temporomandibular Joint (TMJ) after mandibular advancement could be permanently stable are not yet proved. Therefore, our purpose is to investigate the effects of mandibular advancement on the rat TMJ by changing in Matrix Metalloproteinases (MMPs) and Collagens (COLs) expression immunohistochemically (IHC) after retention treatment. In this study, 54 male Sprague-Dawley rats were divided to control group (n=24) and experimental group (n=30) for three months subgroups period. Only experimental sub-groups were subjected to a full-time orthodontic inclined methyl methacrylate bite plate cemented to the incisors to advance the mandible for one month and continued as a half-day-wearer (retention period) till the end of the 2nd month and stayed without appliance during whole 3rd month (post retention period). Then, the assessment of gross-morphological changes of skull and the examination of the articular cartilage for each sub-group histologically in addition to IHC examination for MMP-1, MMP 8 and MMP 13 and COL-I, II and III were done. The gross morphological changes were clear in experimental group as downward forward mandibular advancement in addition to a high significant decreased in the base mandibular length. There was also an abundant cellular proliferation at the condylar cartilage with a significant condylar ossification and higher osteoblastic activity in the experimental group obviously at retention period. Moreover, a significant increase in MMP-13 expression in both differentiation and hypertrophic layers of an experimental group during active and retention periods with reduction in the expression of COL-II in the experimental group was observed with no significant changes in other markers. These upregulation of MMP-13 in associated with significant reduction in expression of COL-II plays a significant role in cartilage collagen degradation and treatment stability, which is confirmed through the post-retention period due to endochondral ossification pattern improvement.

Inhibition of Shedding of Low-Density Lipoprotein Receptor-Related Protein 1 Reverses Cartilage Matrix Degradation in Osteoarthritis.

ObjectiveThe aggrecanase ADAMTS‐5 and the collagenase matrix metalloproteinase 13 (MMP‐13) are constitutively secreted by chondrocytes in normal cartilage, but rapidly endocytosed via the cell surface endocytic receptor low‐density lipoprotein receptor–related protein 1 (LRP‐1) and subsequently degraded. This endocytic system is impaired in osteoarthritic (OA) cartilage due to increased ectodomain shedding of LRP‐1. The aim of this study was to identify the LRP‐1 sheddase(s) in human cartilage and to test whether inhibition of LRP‐1 shedding prevents cartilage degradation in OA.MethodsCell‐associated LRP‐1 and soluble LRP‐1 (sLRP‐1) released from human cartilage explants and chondrocytes were measured by Western blot analysis. LRP‐1 sheddases were identified by proteinase inhibitor profiling and gene silencing with small interfering RNAs. Specific monoclonal antibodies were used to selectively inhibit the sheddases. Degradation of aggrecan and collagen in human OA cartilage was measured by Western blot analysis using an antibody against an aggrecan neoepitope and a hydroxyproline assay, respectively.ResultsShedding of LRP‐1 was increased in OA cartilage compared with normal tissue. Shed sLRP‐1 bound to ADAMTS‐5 and MMP‐13 and prevented their endocytosis without interfering with their proteolytic activities. Two membrane‐bound metalloproteinases, ADAM‐17 and MMP‐14, were identified as the LRP‐1 sheddases in cartilage. Inhibition of their activities restored the endocytic capacity of chondrocytes and reduced degradation of aggrecan and collagen in OA cartilage.ConclusionShedding of LRP‐1 is a key link to OA progression. Local inhibition of LRP‐1 sheddase activities of ADAM‐17 and MMP‐14 is a unique way to reverse matrix degradation in OA cartilage and could be effective as a therapeutic approach.

Repeated exposure to high-frequency low-amplitude vibration induces degeneration of murine intervertebral discs and knee joints.

High-frequency, low-amplitude whole-body vibration (WBV) is being used to treat a range of musculoskeletal disorders; however, there is surprisingly limited knowledge regarding its effect(s) on joint tissues. This study was undertaken to examine the effects of repeated exposure to WBV on bone and joint tissues in an in vivo mouse model. Ten-week-old male mice were exposed to vertical sinusoidal vibration under conditions that mimic those used clinically in humans (30 minutes per day, 5 days per week, at 45 Hz with peak acceleration at 0.3g). Following WBV, skeletal tissues were examined by micro-computed tomography, histologic analysis, and immunohistochemistry, and gene expression was quantified using real-time polymerase chain reaction. Following 4 weeks of WBV, intervertebral discs showed histologic hallmarks of degeneration in the annulus fibrosus, disruption of collagen organization, and increased cell death. Greater Mmp3 expression in the intervertebral disc, accompanied by enhanced collagen and aggrecan degradation, was found in mice exposed to WBV as compared to controls. Examination of the knee joints after 4 weeks of WBV revealed meniscal tears and focal damage to the articular cartilage, changes resembling osteoarthritis. Moreover, mice exposed to WBV also demonstrated greater Mmp13 gene expression and enhanced matrix metalloproteinase-mediated collagen and aggrecan degradation in articular cartilage as compared to controls. No changes in trabecular bone microarchitecture or density were detected in the proximal tibia. Our experiments reveal significant negative effects of WBV on joint tissues in a mouse model. These findings suggest the need for future studies of the effects of WBV on joint health in humans.

Identification of novel, exosite-binding matrix metalloproteinase-13 inhibitor scaffolds

Matrix metalloproteinase-13 (MMP-13) has been implicated as the protease responsible for collagen degradation in cartilage during osteoarthritis (OA). Compounds that inhibit the metalloproteinase at the Zn binding site typically lack specificity among MMP family members. Analogs of the low-micromolar lead MMP-13 inhibitor 4, discovered through high-throughput screening, were synthesized to investigate structure-activity relationships in this inhibitor series. Systematic modifications of 4 led to the discovery of MMP-13 inhibitors 20 and 24 which are more selective than 4 against other MMPs. Compound 20 is also approximately fivefold more potent as an MMP-13 inhibitor than the original HTS-derived lead compound 4.

Inhibition of activity of collagen degradation in cartilage of patients with osteoarthrosis byactivation of glycolysis

Aim. To study the effect of glycolysis activators deferrioxamine (DFO), CoCl2, V(SO4)2 and mimosine on collagen cleavage activity by collagenase in osteoarthritic (OA) articular cartilage explants. Materials and methods. 32 OA articular cartilages obtained after arthroplasty were examined in the study. Cartilages were cultured in the presence of 10-50μM DFO, CoCl2, V(SO4)2 or mimosine. Collagen cleavage activity was measured by ELISA. Inhibition of protein or DNA synthesis in the presence of [3H]-labeled proline or thymidine, respectively, was used for evaluation of examined agent toxicity. Results. Glycolysis activators DFO, CoCl2, V(SO4)2 or mimosine were capable of inhibiting type II collagen cleavage activity in OA articular cartilage explants. The examined agents have shown no toxic effect in the concentrations used. Conclusion. Glycolysis activation in articular chondrocytes may offer a means of inhibiting articular cartilage destruction in OA patients.

4′-Chlorodiazepam — Agonist of peripheral benzodiazepine receptors as a protecting factor in IL-1 induced deregulation of collagen biosynthesis in cultured human chondrocytes

Degenerative joint diseases are related to the excessive degradation of collagen and proteoglycans in cartilage. One of the potent inflammatory mediators of cartilage metabolism is interleukin-1 (IL-1) that has been implicated in the pathogenesis of degenerative joint diseases. Peripheral benzodiazepine receptor ligands have anti-inflammatory activity in rheumatoid arthritis. The present study shows that 4′-chlorodiazepam (Ro-54864), an agonist of peripheral benzodiazepine receptors, counteract inhibition of collagen and DNA biosynthesis, induced by IL-1. Pk-1195, an antagonist of peripheral benzodiazepine receptors did not restore inhibitory effects of IL-1. The mechanism of collagen biosynthesis and cell division regulation involves insulin-like growth factor-I receptor signaling. We found that IL-1 inhibited expression of IGF-IR, while Ro-54864 stimulated the expression of this receptor. Increase in the expression of this receptor was accompanied by increase in mTOR expression and AKT phosphorylation while it had no effect on Ras–Raf–mitogen activated protein kinase (MAPK) pathway. Although IL-1 caused activation of apoptosis in chondrocytes, an addition of Ro-54864 to the cells inhibited the process as detected by annexin V cell staining followed by flow cytometry. The mechanism of this process may be related to protective effect of signal induced by IGF-I receptor. The data suggest that the mechanism of the protective effects of Ro-54864 on IL-1-induced effects in chondrocytes undergoes through mTOR and AKT signaling. It suggest that peripheral benzodiazepine receptor agonist may be considered as a potential pharmacotherapeutical agents in the treatment of inflammatory diseases.

Uncoupling of Collagen II Metabolism in Newly Diagnosed, Untreated Rheumatoid Arthritis Is Linked to Inflammation and Antibodies Against Cyclic Citrullinated Peptides

To investigate the relationship between markers of collagen II synthesis and degradation with disease activity measures, autoantibodies, and radiographic outcomes in a 4-year protocol on patients with early rheumatoid arthritis (RA) who are naïve to disease-modifying antirheumatic drugs. One hundred sixty patients with newly diagnosed, untreated RA entered the Cyclosporine, Methotrexate, Steroid in RA (CIMESTRA) trial. Disease activity and radiograph status were measured at baseline and 4 years. The N-terminal propeptide of collagen IIA (PIIANP) and the cross-linked C-telopeptide of collagen II (CTX-II) were quantified at baseline by ELISA. PIIANP was also assayed at 2 and 4 years. Anticyclic citrullinated peptide (anti-CCP) was recorded at baseline. An uncoupling index for cartilage collagen metabolism was calculated from PIIANP and CTX-II measurements. PIIANP was low at diagnosis and 4 years on (p < 0.001), irrespective of treatment and disease activity. PIIANP was lowest in anti-CCP positive patients (p = 0.006), and there was a negative correlation between PIIANP and anti-CCP titers (rho = -0.25, p 0.002). CTX-II was increased (p < 0.001) and correlated positively with disease activity and radiographic progression, but not with anti-CCP (p = 0.93). The uncoupling index was not superior to CTX-II in predicting radiographic changes. These results suggest that cartilage collagen formation and degradation are unbalanced when RA is diagnosed. The different associations of collagen II anabolism (PIIANP) and collagen II degradation (CTX-II) with anti-CCP, synovitis, and radiographic progression indicate that at this early stage of RA, cartilage collagen degradation is mainly driven by synovitis, while anti-CCP antibodies may interfere with cartilage regeneration by inhibiting collagen IIA formation. Trial registration j.nr NCT00209859.

Protein geranylgeranylation controls collagenase expression in osteoarthritic cartilage

Statins possess anti-inflammatory properties. This study was undertaken to characterize the mechanism of action of statin drugs on collagenase expression in primary human osteoarthritic cartilage tissue. Human articular chondrocytes and cartilage explants from osteoarthritic donors were exposed to simvastatin in the presence or absence of interleukin-1 beta (IL-1beta). Collagenase expression was determined by quantifying levels of matrix metalloproteinase 13 (MMP-13) and MMP-1 mRNA and MMP-13 protein. The mechanism of statin action was tested by addition of farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) or by using inhibitors of farnesyl transferase (FT) and geranylgeranyl transferase (GGT-1). Treatment of osteoarthritic chondrocytes with simvastatin decreased mRNA levels of MMP-13 and MMP-1 whether under basal conditions or during stimulation with IL-1beta. MMP-13 protein secreted into the culture media was also decreased. Genes involved in cartilage synthesis (type II collagen and aggrecan) were not down-regulated by simvastatin. Exogenous addition of GGPP completely reversed the statin-mediated decrease in MMP-13 mRNA and protein levels whereas FPP partially reversed the statin-mediated effect. An inhibitor of GGT-1 mimicked the simvastatin-mediated reduction in MMP-13 expression by chondrocytes. Finally, consistent with impacts on MMP-13 and MMP-1 expression, simvastatin as well as the GGT-1 inhibitor both blocked type II collagen degradation in primary human articular cartilage explants. These results suggest that statins modulate chondrocyte metabolism by reducing prenylation of key signaling molecules that control the expression of collagen-degrading enzymes. Our results strongly support the hypothesis that protein prenyltransferases including geranylgeranyl transferase regulate chondrocyte collagenase expression in osteoarthritis.

Prostaglandin E2 role in inhibition of joint cartilage collagen destruction in patients with osteoarthritis

Система комплексной поддержки и сопровождения научного журнала Elpub позволяет запустить двуязычный сайт журнала со встроенной системой электронной редакции в соответствии с лучшими издательскими практиками, а так же предусматривает техническую и методическую поддержку со стороны специалистов НЭИКОН.

The Helix-II epitope: a cautionary tale from a cartilage biomarker based on an invalid collagen sequence

An apparent database error in the sequence underlying the Helix-II cartilage biomarker immunoassay was investigated at the protein level. Tandem mass spectrometry established the peptide sequence ERGETGPP*GPA in human type II collagen, not ERGETGPP*GTS used to generate the antibody for the Helix-II assay. Recent reports in which the Helix-II assay was applied to urine or serum as a marker of cartilage collagen degradation need to be re-evaluated since the epitope does not occur in cartilage type II collagen. Based on collagen sequences and Helix-II epitope properties, type III collagen is one of several candidate sources of the cross-reacting signal in body fluids, but not type II collagen. The findings highlight the need for more stringent scrutiny of the origins and validation of molecular markers in body fluid assays in general.

The response to oestrogen deprivation of the cartilage collagen degradation marker, CTX-II, is unique compared with other markers of collagen turnover

IntroductionThe urinary level of the type II collagen degradation marker CTX-II is increased in postmenopausal women and in ovariectomised rats, suggesting that oestrogen deprivation induces cartilage breakdown. Here we investigate whether this response to oestrogen is also true for other type II collagen turnover markers known to be affected in osteoarthritis, and whether it relates to its presence in specific areas of cartilage tissue.MethodsThe type II collagen degradation markers CTX-II and Helix-II were measured in the body fluids of premenopausal and postmenopausal women and in those of ovariectomised rats receiving oestrogen or not. Levels of PIIANP, a marker of type II collagen synthesis, were also measured in rats. Rat knee cartilage was analysed for immunoreactivity of CTX-II and PIIANP and for type II collagen expression.ResultsAs expected, urinary levels of CTX-II are significantly increased in postmenopausal women and also in oestrogen-deprived rats, although only transiently. However, in neither case were these elevations paralleled by a significant increase of Helix-II levels and PIIANP levels did not change at any time. CTX-II immunoreactivity and collagen expression were detected in different cartilage areas. The upper zone is the area where CTX-II immunoreactivity and collagen expression best reflected the differences in urinary levels of CTX-II measured in response to oestrogen. However, correlations between urinary levels of CTX-II and tissue immunostainings in individual rats were not statistically significant.ConclusionsWe found only a small effect of oestrogen deprivation on cartilage. It was detected by CTX-II, but not by other type II collagen turnover markers typically affected in osteoarthritis.

A novel paradigm for dendritic cells as effectors of cartilage destruction

Dendritic cells (DCs) are enriched in RA synovium and have been implicated in the pathogenesis of RA primarily through their ability to present autoantigen and activate T cells. However, whether DCs play an effector role in cartilage destruction is unknown. The aim of this study was to investigate whether DCs can induce collagen release from cartilage and the mechanism involved. Human monocyte-derived DCs (mDCs) were activated with CD40 ligand (CD40L) to mimic DC-T-cell interaction, and supernatants were incubated with cartilage explants. Hydroxyproline was assessed as a measure of collagen release and collagenolytic activity was measured by a bioassay using tritiated collagen. TNF-alpha in DC supernatants was measured by specific ELISA. Supernatants from CD40L-activated mDCs, but not unstimulated mDCs, strongly induced the destruction of cartilage collagen. mDC supernatants did not contain collagenases but did induce collagenolytic activity in cartilage explants. Neutralization of TNF-alpha in mDC supernatants completely abolished collagenolysis. This study shows that mDCs, upon CD40-ligation, induce cartilage collagen degradation through an indirect mechanism via the production of TNF-alpha. Our data suggest a potential important role for mDC-derived TNF-alpha in RA, which is in line with the previously reported observations that DCs are a major source of TNF-alpha in early autoimmune lesions and that anti-TNF-alpha therapeutics effectively suppress joint damage in RA patients. We propose that DCs can act as effectors in cartilage destruction, adding a new aspect to the functional role of DCs in RA pathogenesis.

Evidence to suggest that cathepsin K degrades articular cartilage in naturally occurring equine osteoarthritis

The mechanisms leading to degeneration of articular cartilage in osteoarthritis (OA) are complex and not yet fully understood. Cathepsin K (CK) is a cysteine protease which can also cleave the triple helix of type II collagen. This exposes a neoepitope that can now be identified by specific antibodies. The aim of this study was to obtain evidence suggesting a role for CK in naturally occurring equine OA in both lesional and peri-lesional regions. Articular cartilages (n=12 horses; 5 healthy, 7 OA) were harvested from animals postmortem. A gross macroscopic examination, histologic (Safranin O-Fast Green and Picrosirius red staining) and immunohistochemical evaluation were performed. Samples were divided into normal appearing cartilage, peri-lesional and lesional cartilage. Cartilage degradation in the samples was graded histologically and immunohistochemically. CK and possible CK cleavage were detected immunohistochemically with specific anti-protein and anti-neoepitope antibodies, respectively. A comparison of CK neoepitope (C2K) production with the collagenase-generated neoepitope produced by matrix metalloproteinases (MMP)-1, 8 and 13 (C2C) was also assessed immunohistochemically. CK and CK cleavage were significantly more abundant in OA cartilage (both peri-lesional and lesional) when compared to remote cartilage within the sample joint or cartilage from healthy joints. The immunohistochemical pattern observed for CK degradation (C2K) was similar to that of collagenase degradation (C2C). Macroscopic cartilage changes and histologic findings were significantly correlated with immunohistochemistry results. The data generated suggests that CK may be involved in cartilage collagen degradation in naturally occurring osteoarthritis.

Novel Contrast Mechanisms at High Field 1

This article reviews the technical principles of novel contrast mechanisms for musculoskeletal imaging. Ultrashort echo-time imaging allows the visualization of fast T2 relaxing tissue components that are not directly detectable by standard magnetic resonance imaging. This offers several new applications, especially in musculoskeletal imaging, to visualize these tissue components directly. Magnetization transfer techniques, which have been successfully applied to assess demyelinization processes in white brain matter, for example, can be used to detect the integrity of the collagen network of cartilage, and they may help for the detection of early cartilage degradations. Finally, diffusion-weighted imaging represents a further technique to detect bone marrow pathologies or indicate collagen degradation and water content in cartilage. The technical details and implementation techniques of these dedicated imaging modalities are demonstrated and reviewed in this article, and some clinical examples are presented.

The type II collagen fragments Helix-II and CTX-II reveal different enzymatic pathways of human cartilage collagen degradation

Cartilage degradation in osteoarthritis (OA) generates the type II collagen fragments, Helix-II and CTX-II that can be used as clinical biological markers. Helix-II and C-telopeptide of type II collagen (CTX-II) levels are associated independently with progression of OA suggesting that they may be generated through different collagenolytic pathways. In this study we analyzed the release of Helix-II and CTX-II from human cartilage collagen by the proteinases reported to play a role in cartilage degradation. In vitro, human articular cartilage extract was incubated with activated human recombinant cathepsins (Cats) and matrix-metalloproteases (MMPs). Next, we analyzed the spontaneous release of Helix-II and CTX-II from cartilage sections of patients with knee OA who were immediately deep frozen after joint replacement to preserve endogenous enzyme activity until assay. Cartilage sections were then incubated for up to 84 h in the presence or absence of E-64 and GM6001, inhibitors of cysteine proteases and MMPs, respectively. In vitro, Cats K, L and S generated large amount of Helix-II, but not CTX-II. Cat B generated CTX-II fragment, but destroyed Helix-II immunoreactivity. Cat D was unable to digest intact cartilage. MMPs-1, -3, -7, -9, and -13 efficiently released CTX-II, but only small amount of Helix-II. Neither CTX-II nor Helix-II alone was able to reflect accurately the collagenolytic activity of Cats and MMPs as reflected by the release of hydroxyproline. In OA cartilage explants, E-64 blunted the release of Helix-II whereas the release of CTX-II could be completely abrogated by GM6001 and only partly by E-64. These in vitro and ex vivo experiments of human cartilage suggest that Helix-II and CTX-II could be released in part by different enzymatic pathways. Helix-II and CTX-II alone reflect only partially overall cartilage collagen degradation. These findings may explain why these two biological markers could provide complementary information on disease progression in OA.

Assoziation zwischen dem histopathologischen Synovialitis-Typ II und einem erhöhten Pyridinolin-Gehalt im Synovialgewebe bei rheumatoider Arthritis

To investigate the association between immunohistopathological and morphological features of synovitis in rheumatoid arthritis and the amounts of collagen degradation products pyridinoline and deoxypyridinoline in the synovial tissue and in body fluids in order to discover potential markers of erosive disease. Histopathological analysis of synovial tissue samples from 22 patients with RA was performed according to the histopathologic scoring system of RA synovitis by P. Stiehl. Accordingly, the samples were (a) classified into type I synovitis, type II synovitis, or undifferentiated synovitis and were (b) characterized for local features of disease activity, including basic activity and actual activity. The contents of pyridinoline and deoxypyridinoline were measured in the synovial tissue, the synovial fluid, serum and urine by HPLC analysis. The amounts of pyridinoline in synovial tissue samples characterized by type II synovitis were 1.7-fold and 2.7-fold higher compared with those with type I synovitis and undifferentiated synovitis, respectively. In contrast, the content of deoxypyridinoline was not different between the histopathologic types of synovitis. At the same time, increased amounts of pyridinoline, but not deoxypyridinoline, were detected in synovial tissue samples with basic activity or actual activity grade II compared with synovial tissue samples with basic activity or actual activity grade I. The concentrations of both collagen degradation products in the synovial fluid, serum and urine did not differ between patients when they were analyzed either for histopathologic types of synovitis or local disease activity. The amount of cartilage collagen degradation product pyridinoline in synovial tissue is positively correlated with the histopathological grading of local disease activity. Furthermore, the increased amounts of pyridinoline in synovial tissue samples with type II synovitis suggest a more erosive course of RA in patients with this type of synovitis.