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The aim of this study was to investigate the clinical value of serum measurement of C-telopeptide of type II collagen (CTX-II). In correlation with late stages of osteoarthritis (OA) evaluated with histological assessment, the evolution of serum CTX-II concentration was followed during a 20-week longitudinal study in rabbit anterior cruciate ligament transection (ACLT) OA model in adult and growing animals.
Methods
OA was induced in five adult and nine growing rabbits. Four adult and four young rabbits were unoperated. Serum sampling was made at week 0, 1, 2, 3, 4, 6, 8, 10, 12, 14, 16 and 20 after the surgery in all rabbits. Animals were euthanized 20 weeks after the surgery. Serum CTX-II levels were analyzed with a recently available enzyme-linked immunosorbent assay (ELISA) kit, the protocol of which has been modified to increase the sensitivity of the test.
Results
Significant differences for the CTX-II levels at W3, W6, W8, W10, W12, W14, W16 and W20 were observed between the adult ACLT and the control groups. A negative correlation between CTX-II levels and cartilage thickness of the medial compartment of the knee at W8, W10, W12 and a positive correlation between the CTX-II levels and the histomorphological score of the medial compartment of the knee at W3, W6, W8, W10, W12 were noted in adult animals. In young animals, operated or not, we observed high CTX-II levels at the beginning of the study, which decreased until the end.
Conclusion
Our results suggest the interest of the serum CTX-II monitoring for the OA progression and the relevance of the multiple time point analysis of this biomarker. Moreover, they address the question of the importance of correctly choosing the age of the animals used in the pre-clinical studies of OA.
Osteoarthritis (OA) is a disease characterized by a progressive destruction of articular cartilage and by pathological changes in the subchondral bone and synovial membrane
. A major concern in clinical trials in human studies is the improvement and development of diagnostic tools and a more sensitive monitoring of the disease progression
In OA, the destruction of the articular cartilage will result in the loss of its two major components, proteoglycans and type II collagen, making them markers of choice in the evaluation of cartilage metabolism
Cross sectional evaluation of biochemical markers of bone, cartilage, and synovial tissue metabolism in patients with knee osteoarthritis: relations with disease activity and joint damage.
5-yr longitudinal study of type IIA collagen synthesis and total type II collagen degradation in patients with knee osteoarthritis–association with disease progression.
. Although the standard references for quantifying the development of OA are the macroscopic and microscopic analysis, some studies have focused on the quantification of biomarkers in several animal models
The utility of measuring C-terminal telopeptides of collagen type II (CTX-II) in serum and synovial fluid samples for estimation of articular cartilage status in experimental models of destructive joint diseases.
Elevation of a collagenase generated type II collagen neoepitope and proteoglycan epitopes in synovial fluid following induction of joint instability in the dog.
The chemical biomarkers C2C, Coll2-1, and Coll2-1NO2 provide complementary information on type II collagen catabolism in healthy and osteoarthritic mice.
. One main advantage in experimental animal studies is that the time of the trauma remains known, but the exact onset of molecular events of early OA following trauma is still incompletely understood. As biological fluid (synovial fluid, urine or serum) can be obtained before and after the joint injury, biomarkers can be measured in order to precise early molecular events of OA. In an OA rodent model, cartilage matrix breakdown was demonstrated during the early stages of OA progression and a positive correlation between urinary CTX-II levels and histological scores was described
. The results of that study also assessed age-related changes in cartilage turnover in rats and showed a stabilization of cartilage around 5–7 months old.
Only, two studies have been published on biomarkers of OA in adult rabbits. Felice et al.
showed a rapid rise in the degradation of cyanogen bromide cleavage peptide 9.7 (CB 9.7) in synovial fluid with the Hulth–Telhag model. Lindhorst et al.
assessed synovial fluid Col2CTx levels, another marker of type II collagen (which measures the same epitope than CTX-II but with different antibodies) in a menisectomy rabbit model. Their results showed that this marker could be useful in the evaluation of early pathological changes of OA.
The transection of the anterior cruciate ligament (ACLT) in rabbits leads to rapid development of OA. This animal model has been well characterized at both macroscopic and microscopic levels
The utility of measuring C-terminal telopeptides of collagen type II (CTX-II) in serum and synovial fluid samples for estimation of articular cartilage status in experimental models of destructive joint diseases.
Effects of intra-articular administration of glucosamine and a peptidyl-glucosamine derivative in a rabbit model of experimental osteoarthritis: a pilot study.
, they found strong association between microscopic severity scores and CTX-II levels in synovial fluid but not in serum. To our knowledge, no data are available regarding the use of this kit in rabbit sera and about cartilage turnover in young and adult animals. In contrast with urine or synovial fluid, serum sampling do not require animal anesthesia and represents a method less invasive to obtain biological fluid.
The aim of this study was to investigate the clinical value of serum measurement of CTX-II. The evolution of CTX-II concentration was followed during a 20-week longitudinal study in rabbit ACLT OA model in both adult and growing animals and correlated with histological assessment at the end of the experiment where OA process was always at an advanced stage.
Material and methods
Experimental animal model
Twenty-seven healthy male New Zealand White rabbits were used in the study. Twelve rabbits were skeletally mature (10-month-old) and weighing 5.27±0.25 kg; 15 were growing (2-month-old) weighing 2.03±0.15 kgkg (mean±SD). After 15 days of acclimation, experimental OA was surgically induced by ACLT in the left knee: the operated groups were composed of eight adult rabbits and ten young rabbits. Five young and four adult rabbits were unoperated and formed the control groups. The large disparity in group size was due to the mortality of some animals (no biological test was done but the clinical features suggested pasterellosis signs) at their arrival and it is also more difficult to find adult animals than young animals. Animals were housed during the same period at the Institut Claude-Bourgelat, Lyon. They were kept in individual cages (80 cm×80 cm×60 cm, webbed flooring). All experiments were conducted in full compliance with Ecole Nationale Vétérinaire de Lyon Ethical Committee Guidelines (protocol agreement no. 0634).
Surgical procedure
Analgesia was provided with morphine (Aguettant, Lyon, France) before (3 mg/kg) and after surgery (2 mg/kg). Fentanyl patch (25 μg/h, Durogesic®, Janssen-Cilag, Issy-les-Moulineaux, France) was placed on the interscapular space for 3 days following surgery. Trimethoprim 4% (v/w) and Sulfadiazine 20% (v/w) (20 mg/kg, Borgal®, Intervet, Whitby, Canada,) were administered preoperatively and twice a day for 4 days post-operatively. Operated rabbits were firstly anesthezied by an intramuscular injection of ketamine (35 mg/kg, Imalgène 1000®, Merial, Lyon, France) and xylazine (2 mg/kg, Rompun® 2% (v/w), Bayer HealthCare, Gaillard, France). Anesthesia for the surgical procedure was then maintained with a mixture of isoflurane in oxygen. A lateral parapatellar arthrotomy was performed under sterile conditions. The patella was dislocated medially and the knee placed in full flexion. The ACL was visualized and sectioned with a no.12 blade. The joint was irrigated with sterile saline and closed. The contralateral knee was left intact. Rabbits were allowed free activity in their cages. The animals were closely monitored for infections and other complications by a veterinarian. Body weights were measured twice a month. The unoperated and operated anesthesied rabbits were euthanized 20 weeks post-surgery by intracardiac injection of sodium pentobarbital euthanasia solution (Dolethal®, Vétoquinol, Lure, France). Although it is known in this model that advanced disease (ulceration of cartilage) is already present 12 weeks after the surgery in the majority of adult animals, we chose a longer study time because the progression of the disease in young animals is not precisely known and we were interested to follow CTX-II evolution before and after the ulceration development in both age groups of animals.
Blood sampling
5 mL of blood samples were collected serially from the central ear artery of each rabbit at 0, 1, 2, 3, 4 6, 8, 10, 12, 14, 16 and 20 weeks post-surgery. Blood samples were centrifuged at 3000 RPM for 12 min and sera stored in 250 μL aliquots at −80° until CTX-II assay were performed.
CTX-II assay
Serum level of CTX-II was measured over time with the commercially available Serum Pre-clinical Cartilaps enzyme-linked Immunosorbent assay (ELISA) (Nordic Bioscience, Herlev, Denmark) according to the manufacturer’s instructions with some modifications for the rabbit adult samples. Briefly, the sandwich ELISA employs monoclonal antibody F4601 specific for the EKGPDP amino acid sequence derived from the CTX-II. Since the kit lacks sensitivity, we changed serum and buffer volumes in each well for adult rabbits during the primary incubation: 50 μL of buffer were added to 100 μL of sample instead of 100 μL of buffer with 25 μL of sample. We also modified some of the incubation times: primary and secondary incubations were extended to 90 min. Incubation time with chromogenic substrate solution was extended to 30 min. We analyzed five identical serum samples three times in a same kit and with five different kits to evaluate the intra- and inter-assay variations.
Cartilage macroscopic assessment
The articular cartilage of the femur and the tibia were graded blindly according to the following criteria: normal appearance, fibrillation, fissuration, ulceration (illustrated in Fig. 1). After the application of diluted India ink, we graded the lesions according to their size
: Grade 0: normal in appearance and does not retain India ink; Grade 1: 0 mm<fibrillation≤4 mm; Grade 2: 4 mm<fibrillation≤8 mm; Grade 3: 8 mm≤fibrillation; Grade 4: 0 mm<fissuration≤4 mm; Grade 5: 4 mm<fissuration≤8 mm; Grade 6: 8 mm≤fissuration; Grade 7: 0 mm<ulceration≤2 mm; Grade 8: 2 mm<ulceration≤5 mm; Grade 9: 5 mm<ulceration. The lesions were documented digitally using a Panasonic DMC-LZ5 camera. The results are presented using medial (both medial femur and tibia) and lateral knee scores (both lateral femur and tibia) and by the total knee score (mean of both medial and lateral knee scores).
Fig. 1Macroscopic articular cartilage, stained with India ink, representative of different kinds of macroscopic lesions. A: Normal cartilage, no uptake of India ink; B: fibrillation in lateral femoral condyle (minimal uptake of India ink, with surface irregularities) and fissuration (evident dark patches of ink uptake) in medial femoral condyle; C: fissuration in lateral femoral condyle and ulceration (area demonstrating visible bone) in medial femoral condyle; D: ulceration in both femoral condyles.
The distal part of the femur and the proximal part of the tibia were first fixed in 10% (v/v) buffered formalin solution for 24 h. Each femoral condyle and tibial plateau were cut in 3 mm-thickness sagittal sections through the weight-bearing surface with a low speed Isomet saw (Buehler, Illinois, USA) and 15 HC diamond blade (10.2×0.3 mm). The fixation was then completed with three different successive baths for 1 week of 80% ethanol. Dehydratation and embedding were made according to previously described histological procedure
. Undecalcified sections (8 μm-thickness) of the femoral condyles and tibial plateaus were cut with a Polycut E microtome (Leica Microsystem, Wetzlar, Germany) starting from medial part of each knee compartment (lateral and medial femoral condyle, and medial and lateral tibial plateau). Two non-consecutive sections were evaluated per knee compartment. Although more non-consecutive sections are generally recommended to have a better picture of the joint, we needed the remaining bone samples for performing microradiography. Sections were stained by the Safranine O-light green and Goldner trichrome stainings.
Histological assessment was made with a scoring system adapted from Mankin and Colombo score systems on Safranin O-light green staining
Biochemical and metabolic abnormalities in articular cartilage from osteo-arthritic human hips. II. Correlation of morphology with biochemical and metabolic data.
A new model of osteoarthritis in rabbits. I. Development of knee joint pathology following lateral meniscectomy and section of the fibular collateral and sesamoid ligaments.
. Four parameters were evaluated: degree of staining, cartilage structure, chondrocytes density and clone formation (Fig. 2).
Fig. 2Representative histological sections stained with Safranin O-light green and illustrating cartilage lesions. A: Normal articular cartilage with intact surface of a lateral tibia, Magnification 12,5×; B: Loss of cartilage matrix
and fibrillation in a medial femur, Magnification 50×; C: Clusters of cells in a fibrillation with loss of Safranine O-light green staining lesion in a medial femur, Magnification 200×; D: Erosion of cartilage matrix to subchondral bone in a medial femur, Magnification 25×; E: Junction between both ulceration and cartilage zones medial femur, Magnification 50×.
Cartilage thickness was expressed in micrometers and measured at a 12.5× magnification for each compartment. It was measured with Goldner trichrome staining at the site where the worst lesions are normally found for each articular surface. Cartilage surface was delimited manually. Software calculated cartilage thickness by dividing area by the length of the delimited cartilage. When whole analysis area was ulcerated, none delimitation was done and cartilage thickness was 0 μm. When analysis area presented both cartilage and ulcerated zones, the cartilage thickness of the cartilage zone was first calculated. Then a mean between the cartilage thickness of the two zones was calculated according to the length proportion of each other. Only one analysis was performed for a given sample. However, five different analysis separated each other of 1 week, with 16 different samples was performed and the variation coefficient for the cartilage thickness was calculated.
Each histological result represents the mean of score or cartilage thickness of two non-consecutive histological sections obtained by articular compartment. These results are presented using the medial (both medial femur and tibia) and lateral (both lateral femur and tibia) knee compartment scores or the total knee score (mean of both medial and lateral knee scores) for both histomorphological assessment and cartilage thickness measurements.
Statistical analyses
All analyses were planned to be performed at 5% significance level. For the macroscopic and histological assessment, comparisons between animal groups were made with nonparametric Mann–Whitney test for unpaired observations. The evolution of CTX-II and weight over time between groups was assessed using a two-way repeated measures analysis of variance. Associations between histology data and CTX-II levels were made with Spearman’s rank correlation coefficient. Analyses were performed with a statistical package software (StatView, SAS Institute, Version 5.0).
Results
Validation of the kit modifications
Figure 3 shows standard curves derived from both normal and modified protocols. A shift of the modified curve to the left was observed, resulting to a dynamic range of the curve between 10–200 pg/mL instead of 30–400 pg/mL. The precision of the assay was 3.2% and 6.3% for intra- and inter-assay variations respectively.
Fig. 3Standard curves in the normal and modified protocols for the measurement of CTX-II.
According to the clinical examination some rabbits were taken out of the study: three rabbits from the adult operated group were withdrawn due to the integrity of their articulation (oedema, suspicion of septic arthritis), one rabbit from the young operated group and one rabbit from the young unoperated group for bad general health reasons.
Weight loss occurred in the adult operated animals while the unoperated group showed stable weight during the study. Weight evolution showed a significant difference between the ACLT adult rabbits and the control group during the study (P<0,001). With regard to the young rabbits, no significant difference in the weight was observed over time between ACLT and control groups (P=0,637). Their weight increased with age, but did not reach the initial body weight of the adult rabbits (P=0.02). Table I shows the weight progression over time.
Table IIWeight evolution for each rabbit group taken every 4 weeks (N=5 for the operated adult group; N=4 for the unoperated adult group; N=9 for the operated young group; N=4 for the unoperated young group). Values are expressed as means, with the 95% confidence intervals
At the time of sacrifice, gross evaluation showed more severe changes in operated group, in comparison to the unoperated rabbits (total knee score: P=0.014 for the adult group and P=0.02 for the young group). No difference was found between the adult and young rabbits in the control group. Otherwise, the macroscopic analysis revealed more severe changes in the adult operated group, compared to the young operated animals (total knee score: P=0.003). Table II summarizes the macroscopic results.
Table IIIIMacroscopic score for each rabbit group presented for the lateral, medial and total knee (N=5 for the operated adult group; N=4 for the unoperated adult group; N=9 for the operated young group; N=4 for the unoperated young group). Values are expressed as means, with the 95% confidence intervals
Microscopic analysis showed higher score in the operated group, in comparison to the unoperated in both age groups (mean with 95% confidence intervals): 12.28 (9.28–15.28) for the adult operated group and 1.75 (0.48–3.03) for the unoperated adult group (P=0,014) (Fig. 4); 7.53 (5.93–9.13) for the operated young group and 1.72 (−0.23–3.67) for the unoperated young group (P=0,006) (data not shown). No difference was found between adult and young rabbits in the control group (P=0,89). Otherwise, the microscopic evaluation revealed significant higher score for the adult operated rabbits, compared to the young operated rabbits (P=0.03).
Fig. 4Histomorphological score of ACLT and unoperated adult rabbits for the medial (A), lateral (B) and total (C) knee compartments. Box plots show the median, first and third quartiles and the smallest and largest observations. N=5 for the operated group and N=4 for the unoperated group.
Despite the small size of the animal groups, the mean cartilage thickness for the total knee of operated adult rabbits was significantly lower than control adult rabbits (respectively, 281.51 (125.00–427.30) μm and 436.84 (339.30–534.34) μm, P=0.050, Fig. 5) whereas the mean cartilage thickness of operated young rabbits was higher than the control young rabbits (respectively, 505.00 (462.40–547.81) μm and 409.06 (324.42–493.69) μm, P=0.45). No difference was found between adult and young rabbits in the control groups by contrast to operated groups (P=0.003).
Fig. 5Cartilage thickness of ACLT and unoperated adult rabbits for the medial (A), lateral (B) and total (C) knee compartments. Box plots show the median, first and third quartiles and the smallest and largest observations. N=5 for the operated group and N=4 for the unoperated group.
Longitudinal analysis of CTX-II levels and correlation with histological assessment
As we observed some differences of the CTX-II level evolution between adult and young rabbits, results will therefore be presented separately (Fig. 6).
Fig. 6Evolution of serum CTX-II levels in adult (A: N=5 for the operated group and N=4 for the unoperated group) and young rabbits (B N=9 for the operated group and N=4 for the unoperated group). Data are shown as mean and bars represent 95% confidence intervals.
A slight decrease of CTX-II levels was observed with the unoperated adult rabbits from the beginning of the study until week 6 (W6) post operation, followed by a mild increase until W12, then a second decrease and stabilization of CTX-II level during the last month of the study [Fig. 6(A)]. The CTX-II evolution showed two distinct elevations with ACLT rabbits, one during the three first weeks after the surgery, followed by a decrease until the W4 and a second peak at the W12. From the peak of the W12, a decrease was observed until the end of the study. Statistical analysis showed that CTX-II levels can differentiate operated from unoperated animals.
We observed a positive correlation between the CTX-II levels at W3 (r′=0.78, P=0.03), W6 (r′=0.78, P=0.03), W8 (r′=0.76, P=0.03), W10 (r′=0.63, P=0.03) and W12, and the histomorphological score of the medial compartment [Fig. 7(A)]. Our results showed negative correlation between the CTX-II levels at W8 (r′=−0.82, P=0.02), W10 (r′=−0.70, P=0.048) and W12 and the cartilage thickness of the medial compartment [Fig. 7(B)]. Non-significant correlation was found between CTX-II levels at W20 and histological analysis of the medial compartment of the knee [Figs. 7(C) and 7(D)].
Fig. 7Correlations between CTX-II levels at the twelfth (upper graphs) and twentieth (bottom graphs) weeks and histomorphological score (A or C) cartilage thickness (B or D) in the medial compartment of the knee. N=9.
With young rabbits, CTX-II levels were quite high (224±118 pg/mL, Fig. 6(B)) at the beginning of the study and decreased over time until the end of the experiment. Time (associated to the animal growth) affected CTX-II levels (P<0,001), but not the chirurgical act. The CTX-II levels decreased with growth, but did not reach the initial basal level of the adult rabbits group (P=0.03).
No correlation between the macroscopic or the microscopic analyses and the CTX-II level evolution was found at any time point in the young rabbits group.
Discussion
In the present study we investigated the articular cartilage degradation with the measurement of serum CTX-II levels in a 5-month longitudinal study with an ACLT surgical model. To our knowledge, this study presents the first results from a longitudinal evaluation of CTX-II marker with an OA rabbit model. Macroscopic and microscopic analyses showed typical OA lesions in all the operated rabbit knees.
The first CTX-II peak appeared during the first three weeks following the surgery. That joint response seems to be associated with post-operative inflammation in the joints due to the chirurgical act which can influence cartilage collagen turnover. The fact that the CTX-II levels decreased in the operated rabbits after the initial rise and before the second one confirms this hypothesis. Other studies reported the same early collagen type-II degradation in operated and sham-operated knee joints in rabbits using immunohistochemistry
. In their study, they observed that increased CTX-II levels were accompanied by the release of aggrecan fragments and MMPs.
From the sixth week on, we observed a second rise of CTX-II continuing up to a peak at W12 for the majority of animals (peak at the fourteenth week for one animal), followed by a progressive decrease until the end of the study. Those results suggest that enhanced degradation seems to occur 6 weeks after the surgery in the progression of the OA disease, followed by a moderate degradation in later stages due to a reduction in cartilage volume. CTX-II peak might be associated with the presence of an ulcer lesion with a high cartilage destruction activity. It was shown that light OA lesions were present 4 weeks after the surgery while around 40% and 60% of the animals presented cartilage ulcer lesions in the load bearing area at W8 and the W12 respectively after the surgery
The following fall in the CTX-II level suggests that there was no more cartilage in the load bearing area during the late stage of the OA progression and thus less production of marker in the joint. In a 5-year longitudinal study in humans, Sharif et al. reported a progressive CTX-II rise during the two first years followed by a decrease during the three following years with patients classified in a OA progressive sub-group
5-yr longitudinal study of type IIA collagen synthesis and total type II collagen degradation in patients with knee osteoarthritis–association with disease progression.
. The evolution of the CTX-II concentration that we found with the operated adult rabbits demonstrates the relevance of a multiple time point analysis. From the longitudinal analysis of the CTX-II level, information on the cartilage activity and the stages of OA lesions could be obtained.
In order to evaluate the OA predictive value of CTX-II, we performed correlations between CTX-II levels at all time points and microscopic assessments at the end of the study. We showed a negative correlation between CTX-II levels at W8, W10 and W12 and cartilage thickness of medial compartment of the knee. Moreover, a positive correlation between CTX-II levels at W3, W6, W8, W10 and W12 and histomorphological score of the medial compartment of the knee was observed. These results are in accordance with others, which showed predominant lesions in the medial knee compartment with this animal model
. They suggest that serum CTX-II has predictive value for the disease severity and cartilage loss in the ACLT rabbit model during the OA process. Even if the rise at the third week appears to be associated to the surgery, it seems to be predictive of late disease stage, as evidenced by the correlation between the CTX-II levels at this time and the histomorphological score. In this context, early CTX-II analysis could be interesting for evaluating the late cartilage damage following the joint trauma. The lack of association between CTX-II levels at W16 and W20 and histological assessment may be due to low levels of CTX-II at those times, which were close to concentrations measured in control animals. This suggests that CTX-II levels, at terminal stages of OA, must be interpreted with caution and exemplified the interest to make measurements of the marker at several time points.
In young operated rabbits as well as in unoperated animals, our results showed high CTX-II levels (around 20-fold comparatively to adults), decreasing all along the study until the end. Those high levels of CTX-II seem to be representative of the growth plate activity, which decreases with the animal growth. This activity seems to influence the cartilage turnover until 11–12 months of age in rabbits. Other animal studies found that cartilage turnover is influenced by the growth in young rats until 5–7 months of age
. In humans, high concentrations were also seen in children, adolescent and young adults (aged of 20–25 years old) and stable levels were detected in adults between 30 and 50 years old
Cartilage turnover assessed with a newly developed assay measuring collagen type II degradation products: influence of age, sex, menopause, hormone replacement therapy, and body mass index.
Improvement of reduced serum cartilage oligomeric matrix protein levels in systemic juvenile idiopathic arthritis patients treated with the anti-interleukin-6 receptor monoclonal antibody tocilizumab.
Results of OA lesions that were found in the young operated rabbits indicate a progression of the disease slower than that observed in adult rabbits, young animal having a higher compensation capacity of the cartilage
. Indeed, only two of the nine young operated rabbits presented two small ulcers in one of these articular compartments 20 weeks after the ACLT surgery by comparison with the operated adult rabbits, where at least one cartilage ulcer with average size in one of its compartments joints was always observed. Vignon et al.
showed that six rabbits on 10, weighing around 4.4 kg, presented cartilage ulcer 12 weeks after ACLT surgery.
Differences in the macroscopic/microscopic results and the evolution of CTX-II during time between the operated young and adult rabbits question the use of young animals in OA studies. The articular cartilage of the knee of the New Zealand rabbits reaches structural maturity at the time of their sexual maturity (3–4 months) but the growth plates are still opened and active at that time
The structural architecture of adult mammalian articular cartilage evolves by a synchronized process of tissue resorption and neoformation during postnatal development.
A longitudinal study of the growth of the New Zealand white rabbit: cumulative and biweekly incremental growth rates for body length, body weight, femoral length, and tibial length.
. Our results suggest thus that the maturity of the articular cartilage is not the only factor which affects the progression of the OA lesions.
In conclusion, our results demonstrate the interest of the serum determination of CTX-II for the monitoring of the OA progression. Other studies with a greater number of animals and multipoint histological assessment will bring additional information on the predictive value of this marker. Finally, our findings address the question of the importance of carefully choosing adults animals used in the pre-clinical studies of OA.
Author contributions
ME. Duclos: conception and design, analysis and interpretation of the data, drafting of the article, collection and assembly of data.
O. Roualdes: conception and design, collection and assembly of data.
R. Cararo: conception and design.
JC. Rousseau: analysis and interpretation of the data.
T. Roger: final approval of the version to be submitted.
DJ. Hartmann: final approval of the version to be submitted.
Conflict of interest
All the authors have no conflict of interest related to this work.
Acknowledgment
The authors wish to thank the Institut Claude-Bourgelat, Lyon, France, for the animal care.
Cross sectional evaluation of biochemical markers of bone, cartilage, and synovial tissue metabolism in patients with knee osteoarthritis: relations with disease activity and joint damage.
5-yr longitudinal study of type IIA collagen synthesis and total type II collagen degradation in patients with knee osteoarthritis–association with disease progression.
The utility of measuring C-terminal telopeptides of collagen type II (CTX-II) in serum and synovial fluid samples for estimation of articular cartilage status in experimental models of destructive joint diseases.
Elevation of a collagenase generated type II collagen neoepitope and proteoglycan epitopes in synovial fluid following induction of joint instability in the dog.
The chemical biomarkers C2C, Coll2-1, and Coll2-1NO2 provide complementary information on type II collagen catabolism in healthy and osteoarthritic mice.
Effects of intra-articular administration of glucosamine and a peptidyl-glucosamine derivative in a rabbit model of experimental osteoarthritis: a pilot study.
Biochemical and metabolic abnormalities in articular cartilage from osteo-arthritic human hips. II. Correlation of morphology with biochemical and metabolic data.
A new model of osteoarthritis in rabbits. I. Development of knee joint pathology following lateral meniscectomy and section of the fibular collateral and sesamoid ligaments.
Cartilage turnover assessed with a newly developed assay measuring collagen type II degradation products: influence of age, sex, menopause, hormone replacement therapy, and body mass index.
Improvement of reduced serum cartilage oligomeric matrix protein levels in systemic juvenile idiopathic arthritis patients treated with the anti-interleukin-6 receptor monoclonal antibody tocilizumab.
The structural architecture of adult mammalian articular cartilage evolves by a synchronized process of tissue resorption and neoformation during postnatal development.
A longitudinal study of the growth of the New Zealand white rabbit: cumulative and biweekly incremental growth rates for body length, body weight, femoral length, and tibial length.
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