Assessment of the effects of age and joint disease on hydroxyproline and glycosaminoglycan concentrations in synovial fluid from the metacarpophalangeal joint of horses

Unveiling Charge-Pair Salt-Bridge Interaction Between GAGs and Collagen Protein in Cartilage: Atomic Evidence from DNP-Enhanced ssNMR at Natural Isotopic Abundance

The interactions between glycosaminoglycans (GAGs) and proteins are essential in numerous biochemical processes that involve ion-pair interactions. However, there is no evidence of direct and specific interactions between GAGs and collagen proteins in native cartilage. The resolution of solid-state NMR (ssNMR) can offer such information but the detection of GAG interactions in cartilage is limited by the sensitivity of the experiments when 13C and 15N isotopes are at natural abundance. In this communication, this limitation is overcome by taking advantage of dynamic nuclear polarization (DNP)-enhanced magic-angle spinning (MAS) experiments to obtain two-dimensional (2D) 15N-13C and 13C-13C correlations on native samples at natural abundance. These experiments unveiled inter-residue correlations in the aliphatic regions of the collagen protein previously unobserved. Additionally, our findings provide direct evidence of charge-pair salt-bridge interactions between negatively charged GAGs and positively charged arginine (Arg) residues of collagen protein. We also identified potential hydrogen bonding interactions between hydroxyproline (Hyp) and GAGs, offering atomic insights into the biochemical interactions within the extracellular matrix of native cartilage. Our approach may provide a new avenue for the structural characterization of other native systems.

Extracellular vesicles in synovial fluid from juvenile horses: No age-related changes in the quantitative profile

Extracellular vesicle (EV) concentration, characteristics and function in equine synovial fluid (SF) during normal growth and development has not previously been studied. Isolation of EVs was performed in SF from three healthy foals and two adult horses by differential ultracentrifugation (10,000g and 200,000g); EVs were purified by sucrose density gradient floatation and analysed by high-resolution flow cytometry (FCM), buoyant density and western blotting. Additionally, repeated biomarker analysis of sulphated glycosaminoglycans (GAG), matrix metalloproteinase (MMP), C-terminal crosslinked telopeptide type II collagen (CTX-II), collagenase cleaved neopeptide type II collagen (C2C) was performed in SF from 10 foals and six adult horses. In contrast with the quantitative EV profile, the biomarker profile in SF from juvenile joints was substantially different from that in SF from adult animals. However, there were qualitative differences in the high-resolution FCM scatter plots. Future in-depth functional analyses may reveal differences between juvenile and mature EVs in SF.

Changes in Synovial Fluid Biomarkers after Experimental Equine Osteoarthritis

Introduction

The study aimed to clarify the changes in the concentration of inflammatory mediators, proteases, and cartilage degradation biomarkers in the synovial fluid of joints in an equine osteoarthritis model.

Material and Methods

Osteoarthritis was induced in eight Mongolian horses by a sterile intra-articular injection of amphotericin B, which was injected into the left carpal joint in a dose of 2 mL (25 mg/mL). The control group comprised five horses which were injected with an equal dose of sterile physiological saline into the left carpal joint. Synovial fluid was obtained at baseline and every week after injection. Test methods were based on ELISA.

Results

In the course of the osteoarthritis, the concentration of biomarkers in joint synovial fluid showed an increasing trend. IL-1, IL-6, MMP-9, MMP-13, ADAMTS-5, CS846, GAG, HA, CTX-II, and COMP concentrations sharply increased before the onset of significant symptoms of lameness, whereas TNF-α, MMP-2, and MMP-3 concentrations rose sharply after the occurrence of such symptoms.

Conclusion

The results obtained confirm that the concentrations of IL-1, IL-6, MMP-9, MMP-13, ADAMTS-5, CS846, GAG, HA, CTX-II and COMP increase substantially in equine osteoarthritis, which provides a theoretical basis for the rapid diagnosis of the disease.

Viability and Tissue Quality of Cartilage Flaps From Patients With Femoroacetabular Hip Impingement: A Matched-Control Comparison

Background:

Chondrolabral damage is commonly observed in patients with cam-type femoroacetabular impingement (FAI). Chondral flap reattachment has recently been proposed as a possible preservation technique.

Purpose/Hypothesis:

The purpose of this study was to determine the viability and tissue quality of chondral flaps from patients with FAI at the time of arthroscopy. It was hypothesized that chondral flaps from patients with cam lesions of the hip would exhibit less viability and greater tissue degeneration than would those of a matched control group.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

Patients with cam-type FAI who were treated with hip arthroscopy between 2014 and 2016 were asked to participate in this study. The cartilage lesions were localized and classified intraoperatively according to Beck classification. A chondral flap (study group) and a cartilage sample (control group) were obtained from each patient for histologic evaluation. Cellular viability and tissue quality were examined and compared in both groups. Cellular viability was determined with live/dead staining, and tissue quality was evaluated using safranin O/fast green, hematoxylin and eosin (H&E) staining, and immunohistochemistry for collagen II. Osteoarthritis Research Society International (OARSI) grading was used for quality assessment, and Image J software was used to calculate the percentage of tissue viability and Col II stain.

Results:

A total of 10 male patients with a mean age of 38.4 years (range, 30-55 years) were enrolled. All chondral flaps were classified as Beck grade 4. The mean cellular viability of the chondral flaps was reduced (54.6% ± 25.6%), and they were found to be degenerated (OARSI grade, 4 ± 1.27). Control samples also had reduced viability (38.8% ± 30.3%) and were degenerative (OARSI grade, 3.5 ± 1.38). There was no statistically significant intergroup difference for viability (P = .203) or OARSI grade (P = .645), nor was there an intragroup correlation between viability and OARSI grade (P > .05). A significant negative correlation (r = −0.9, P = .035) was found between OARSI grade and collagen II percentage scale in 5 selected samples.

Conclusion:

Despite appearing normal macroscopically, the chondral flaps from patients with cam-type FAI displayed loss of viability and tissue degeneration. In addition, control samples obtained away from the injury area also displayed cartilage damage and degeneration. Careful consideration should be taken when attempting to reattach the chondral flap.

Measurement of glycosaminoglycans in canine synovial fluid and its correlation with the cause of secondary osteoarthritis, age and body weight

Glycosaminoglycans are natural components of healthy joint cartilage and they also appear in healthy synovial fluid. An increased amount of glycosaminoglycans in synovial fluid is believed to be a marker of secondary osteoarthritis, regardless of its primary cause. The aim of our study was to define the relationship between glycosaminoglycans in the synovial fluid and joint disorders, age, and body weight. The samples of synovial fluid were obtained from dogs suffering from secondary secondary osteoarthritis (n = 35) and from control dogs (n = 18); control dogs had normal body weight. The results were compared among joints of dogs with secondary osteoarthritis divided into groups according to the criteria mentioned above and control dogs. Glycosaminoglycan concentrations in synovial fluid were measured using dimethylmethylene blue assay. The lowest mean value of glycosaminoglycans in synovial fluid was measured in the control group. Significantly higher glycosaminoglycan content (P < 0.05) was found in synovial fluid isolated from obese dogs compared to control dogs. Furthermore, we observed an age-related trend, in which the highest mean values were reached either in old dogs or pups. Despite the absence of significant differences in glycosaminoglycan values among dogs suffering from various types of secondary secondary osteoarthritis, the highest mean values were measured in fragmented coronoid processus group. Our data suggest that abnormally increased body weight has an impact on glycosaminoglycan concentration in synovial fluid which may imply faster degradation and turnover of joint cartilage. Such observation has not yet been published in veterinary medicine.

Associations of horse age, joint type, and osteochondral injury with serum and synovial fluid concentrations of type II collagen biomarkers in Thoroughbreds

OBJECTIVE

To determine the effects of horse age, osteochondral injury, and joint type on a synthesis biomarker and 3 degradative biomarkers of type II collagen in Thoroughbreds.

ANIMALS

Healthy rested adult (3- to 12-year-old) Thoroughbreds (n = 19), yearling (1- to 2-year-old) Thoroughbreds (40), and Thoroughbred racehorses (2 to 7 years old) undergoing arthroscopic surgery for removal of osteochondral fragments that resulted from training or racing (41).

PROCEDURES

Samples of blood and metacarpophalangeal, metatarsophalangeal, or carpal joint synovial fluid (SF) were collected from all horses. Commercially available assays were used to analyze SF and serum concentrations of type II collagen biomarkers of synthesis (carboxy propeptide of type II collagen [CPII]) and degradation (cross-linked C-telopeptide fragments of type II collagen [CTX II], neoepitope generated by collagenase cleavage of type I and II collagen [C1,2C], and neoepitope generated by collagenase cleavage of type II collagen [C2C]).

RESULTS

Osteochondral injury affected concentrations of CPII, CTX II, C1,2C, and C2C in SF, serum, or both, compared with concentrations in healthy adult horses. Compared with adult horses, yearling horses had increased SF or serum concentrations of degradative biomarkers (CTX II, C1,2C, and C2C). Concentrations were higher in carpal than metacarpophalangeal or metatarsophalangeal joints for all biomarkers in osteochondral-injured horses. Variable differences in SF concentrations between joint types were detected in healthy adult and yearling horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Horse age, osteochondral injury, and joint type all significantly affected type II collagen biomarker concentrations in SF and serum of Thoroughbreds.

Influence of repeated arthrocentesis and exercise on synovial fluid concentrations of nitric oxide, prostaglandin E2 and glycosaminoglycans in healthy equine joints

REASONS FOR PERFORMING STUDY

The importance of osteoarthritis (OA) in the horse and the difficulty in its early diagnosis have led to a search for potential biomarkers of joint disease. If the levels of such markers are to be interpreted accurately, clinicians and researchers need to know whether they are influenced by environmental factors and/or interventions such as exercise and repeated arthrocentesis.

OBJECTIVE

To investigate the influence of repeated arthrocentesis and exercise on nitric oxide (NO), prostaglandin E2 (PGE2) and glycosaminoglycan (GAG) concentrations in synovial fluid (SF) from normal equine joints.

METHODS

SF was collected from the left metacarpophalangeal (MCP), radiocarpal and tarsocrural joints of 16 horses. Half of the horses were exercised and arthrocentesis was repeated 14, 14.5, 17 and 24 days after the start of the exercise programme, in both exercised and control horses. Nitric oxide was determined in SF from the MCP joint only and PGE2 and GAG concentrations were determined in SF from all joints.

RESULTS

Repeated arthrocentesis caused an increase in NO concentration in the MCP joint on Day 145, in PGE2 concentrations in the radiocarpal and tarsocrural joints on Day 145 and the release of GAGs into SF of the MCP and radiocarpal joints on Day 17. Exercise resulted in an increase in PGE2 levels in all joints but did not influence the other parameters measured.

POTENTIAL RELEVANCE

Repeated arthrocentesis is a potential confounding factor for the use of synovial NO, PGE2 and GAG concentrations as markers of joint disease. Based on this study, such a confounding effect can be avoided if one week or more separates arthrocentesis procedures. Moderate exercise causes a transient rise in PGE2 in SF.

Arthrogenic lameness of the fetlock: synovial fluid markers of inflammation and cartilage turnover in relation to clinical joint pain

REASONS FOR PERFORMING THE STUDY

Joint pain is one of the most common causes of lameness in the horse but its pathogenesis is poorly understood.

OBJECTIVES

To investigate which synovial fluid markers may be related to the presence of clinically detectable joint pain in the horse.

METHODS

Concentrations of structural (CPII, C2C, GAG) and inflammatory markers (PGE2, LTB4, CysLTs, bradykinin and substance P) were measured in fetlock joint fluid from 22 horses in which lameness was localised to the fetlock region by perineural anaesthesia. Levels of these markers were then compared in horses that responded (n = 15) to those that did not (n = 7) to subsequent intra-articular anaesthesia (IAA).

RESULTS

Of all markers analysed, only substance P levels were significantly higher (P = 0.0358) in synovial fluid of horses that showed a positive response to IAA compared to those with a negative response to IAA. Notably, while PGE2 levels were found to be elevated in all 22 lame horses compared to sound controls (P = 0.0025), they were not related to the response to IAA.

CONCLUSIONS

While levels of PGE2 are elevated in synovial fluid of lame horses that respond to perineural anaesthesia, only substance P is related to joint pain as detected by the response to intra-articular anaesthesia.

POTENTIAL RELEVANCE

Substance P is associated with clinically detectable joint pain in the horse. Elevated levels of PGE2 in fetlock-lame horses, regardless of their response to IAA, indicate that either this mediator does not reflect intra-articular pain or that IAA might have limitations in differentiating between intra- and peri-articular sources of pain. Either way, a negative response to IAA may not exclude intra-articular pathology.

Identification of infrared absorption spectral characteristics of synovial fluid of horses with osteochondrosis of the tarsocrural joint

OBJECTIVE

To determine the feasibility of the use of Fourier-transform infrared (FTIR) spectroscopy within the midinfrared range to differentiate synovial fluid samples of joints with osteochondrosis from those of control samples.

ANIMALS

33 horses with osteochondrosis of the tarsocrural joint and 31 horses free of tarsocrural joint disease.

PROCEDURES

FTIR spectroscopy of synovial fluid was used. Sixty-four synovial fluid samples from the tarsocrural joint were collected. Of these, 33 samples were from horses with radiographic evidence of osteochondrosis of the tarsocrural joint and 31 from control joints. Disease-associated features within infrared spectra of synovial fluid were statistically selected for spectral classification, and the variables identified were used in a classification model. Linear discriminant analysis and leave-one-out cross-validation were used to develop a classifier to identify joints with osteochondrosis.

RESULTS

12 significant subregions were identified that met the selection criteria. The stepwise discriminant procedure resulted in the final selection of 6 optimal regions that most contributed to the discriminatory power of the classification algorithm. Infrared spectra derived from synovial fluid of joints with osteochondrosis were differentiated from the control samples with accuracy of 77% (81% specificity and 73% sensitivity).

CONCLUSIONS AND CLINICAL RELEVANCE

The disease-associated characteristics of infrared spectra of synovial fluid from joints with osteochondrosis may be exploited via appropriate feature selection and classification algorithms to differentiate joints with osteochondrosis from those of control joints. Further study with larger sample size including age-, breed-, and sex-matched control horses would further validate the clinical value of infrared spectroscopy for the diagnosis of osteochondrosis in horses.

Effect of exercise on serum concentration of cartilage oligomeric matrix protein in Thoroughbreds

OBJECTIVE

To evaluate changes in serum cartilage oligomeric matrix protein (COMP) concentrations in response to exercise in horses.

ANIMALS

15 horses in experiment 1 and 27 horses in experiment 2.

PROCEDURES

In experiment 1, 15 Thoroughbreds free of orthopedic disease underwent a standardized exercise protocol. Running velocity and heart rate (HR) were recorded, and blood samples were collected immediately before (baseline) and 1, 5, and 24 hours after a single episode of exercise. In experiment 2, 27 horses underwent 9 stages of a training program in which each stage consisted of 4 to 8 consecutive daily workouts followed by a rest day. Blood samples were collected immediately before the first and final daily workouts in each stage. Serum COMP concentrations were measured via inhibition ELISA with a monoclonal antibody (14G4) against equine COMP.

RESULTS

In experiment 1, mean serum COMP concentration was significantly higher than baseline 1 and 5 hours after exercise and returned to baseline concentrations 24 hours after exercise. Mean serum baseline COMP concentration increased as the velocity of running at maximum HR and at an HR of 200 beats/min increased, being significantly higher during the third and fourth exercise tests than during the first. In experiment 2, mean baseline COMP concentration at the final workout of each stage was significantly higher than that at the first workout, beginning with stage 3.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum COMP concentrations changed significantly in response to exercise. Exercise may enhance movement of COMP into the circulation as well as change the basal turnover rate of COMP.

Cartilage-derived biomarkers and lipid mediators of inflammation in horses with osteochondritis dissecans of the distal intermediate ridge of the tibia

OBJECTIVE

To assess whether reported alterations in metabolism of cartilage matrix in young (0 to 24 months old) horses with osteochondritis dissecans (OCD) may also be found in older (24 to 48 months old) horses with clinical signs of OCD and to investigate the role of eicosanoids in initiating these clinical signs.

SAMPLE POPULATION

Synovial fluid was collected from 38 tarsocrural joints of 24 warmblood horses with (22 joints of 16 horses) or without (16 joints of 8 horses) clinical signs and a radiographic diagnosis of OCD of the distal intermediate ridge of the tibia.

PROCEDURES

Turnover of type II collagen was investigated by use of specific immunoassays for synthesis (carboxypropeptide of type II collagen [CPII]) and degradation (collagenase-cleaved fragments of type II collagen [C2C]) products. Furthermore, glycosaminoglycan (GAG), leukotriene (LT) B(4), cysteinyl LTs, and prostaglandin (PG) E(2) concentrations were determined, and concentrations in joints with OCD were compared with those in joints without OCD.

RESULTS

Concentrations of CPII, C2C, and GAG did not differ significantly between affected and nonaffected joints. Fluid from joints with OCD had significantly higher LTB(4) and PGE(2) concentrations than did fluids from nonaffected joints.

CONCLUSIONS AND CLINICAL RELEVANCE

Altered collagen or proteoglycan turnover was not detected in 24- to 48-month-old horses at the time they developed clinical signs of OCD of the distal intermediate ridge of the tibia. However, increased concentrations of LTB(4) and PGE(2) in fluid of joints with OCD implicate these mediators in the initiation of clinical signs of OCD.

Characterization of experimentally induced post-traumatic osteoarthritis in the medial femorotibial joint of horses

OBJECTIVE

To study osteoarthritis in the equine medial femorotibial (MFT) joint after a single traumatic injury.

ANIMALS

10 mature horses.

PROCEDURE

In vitro explant cultures were used to determine injury threshold for stifle joint cartilage. Contusive impacts were applied to the medial femoral condyle (MFC), and horses were followed for 84 (n = 5) and 180 days (5). Synovial fluid samples were collected every 14 days for determination of sulphated glycosaminoglycan (sGAG) concentrations. Radiographic and lameness evaluations were performed. Gross and histologic descriptions, and immunohistochemistry, cartilage sGAG content determination, and cartilage aggregate modulus determination were performed at the MFC impact site (MFCi), MFC nonimpact site (MFCn), and medial tibial plateau (MTP).

RESULTS

Synovial fluid sGAG concentration decreased significantly on days 14, 28, 42, and 56 in all horses. Macroscopic and microscopic articular lesions developed within all MFT joints. No radiographic abnormalities were observed. Mild lameness was evident in several horses. No significant differences were found between short-term and longterm cohorts of horses with respect to histologic scores and TUNEL results. On immunohistochemistry, MFCi was positive for COL2-(3/4)C(short). International Cartilage Repair Society scores differed significantly between short-term and long-term cohorts of horses. In all horses, sGAG concentrations were significantly decreased at the MFCi, compared with the MFCn.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of contusive impacts on the MFC of horses results in cartilage lesions that are similar to those described clinically, supporting trauma as a contributing factor in the natural pathogenesis of osteoarthritis.