Ex Vivo Pathomechanics of the Canine Pond-Nuki Model

Background

Transection of the canine cranial cruciate ligament (CCL) is a well-established osteoarthritis (OA) model. The effect of CCL loss on contact pressure and joint alignment has not been quantified for stifle loading in standing. The purposes of the study were to measure femorotibial contact areas and stresses and joint alignment following transection of the CCL in an ex vivo model. We hypothesized that transection of the CCL would lead to abnormal kinematics, as well as alterations in contact mechanics of the femorotibial joint.

Methodology/Principal Findings

Eight canine hindlimbs were tested in a servo-hydraulic materials testing machine using a custom made femoral jig. Contact area and pressure measurements, and femorotibial rotations and translations were measured in the normal and the CCL–deficient stifle in both standing and deep flexion angles.We found that at standing angle, transection of the CCL caused cranial translation and internal rotation of the tibia with a concurrent caudal shift of the contact area, an increase in peak pressure and a decrease in contact area. These changes were not noted in deep flexion. At standing, loss of CCL caused a redistribution of the joint pressure, with the caudal region of the compartment being overloaded and the rest of the joint being underloaded.

Conclusion

In the Pond-Nuki model alterations in joint alignment are correlated with shifting of the contact points to infrequently loaded areas of the tibial plateau. The results of this study suggest that this cadaveric Pond-Nuki model simulates the biomechanical changes previously reported in the in-vivo Pond-Nuki model.     

Efficacy test of Polycan, a beta-glucan originated from Aureobasidium pullulans SM-2001, on anterior cruciate ligament transection and partial medial meniscectomy-induced-osteoarthritis rats

The object of this study was to assess the efficacy of Polycan from Aureobasidium pullulans SM-2001, which is composed mostly of beta-1,3-1,6-glucan, on osteoarthritis (OA)-induced by anterior cruciate ligament transection and partial medial meniscectomy (ACLT&PMM). Three different dosages of Polycan (85, 42.5, and 21.25 mg/kg) were orally administered once a day for 84 days to male rats a week after ACLT&PMM surgery. Changes in the circumference and maximum extension angle of each knee, and in cartilage histopathology were assessed using Mankin scores 12 weeks after Polycan administration. In addition, cartilage proliferation was evaluated using bromodeoxyuridine (BrdU). As the result of ACLT&PMM, classic OA was induced with increases in maximum extension angles, edematous knees changes, and capsule thickness, as well as decreases in chondrocyte proliferation, cartilages degenerative changes, and loss of articular cartilage. However, these changes (except for capsule thickness) were markedly inhibited in all Polycan- and diclofenac sodium-treated groups compared with OA control. Although diclofenac sodium did not influence BrdU uptake, BrdU-immunoreactive cells were increased with all dosages of Polycan, which means that Polycan treatment induced proliferation of chondrocytes in the surface articular cartilage of the tibia and femur. The results obtained in this study suggest that 84 days of continuous oral treatment of three different dosages of Polycan led to lesser degrees of articular stiffness and histological cartilage damage compared with OA controls 91 days after OA inducement, suggesting that the optimal Polycan dosage to treat OA is 42.5 mg/kg based on the present study.     

Three-Dimensional Quantitative Morphometric Analysis (QMA) for In Situ Joint and Tissue Assessment of Osteoarthritis in a Preclinical Rabbit Disease Model

This work utilises advances in multi-tissue imaging, and incorporates new metrics which define in situ joint changes and individual tissue changes in osteoarthritis (OA). The aims are to (1) demonstrate a protocol for processing intact animal joints for microCT to visualise relevant joint, bone and cartilage structures for understanding OA in a preclinical rabbit model, and (2) introduce a comprehensive three-dimensional (3D) quantitative morphometric analysis (QMA), including an assessment of reproducibility. Sixteen rabbit joints with and without transection of the anterior cruciate ligament were scanned with microCT and contrast agents, and processed for histology. Semi-quantitative evaluation was performed on matching two-dimensional (2D) histology and microCT images. Subsequently, 3D QMA was performed; including measures of cartilage, subchondral cortical and epiphyseal bone, and novel tibio-femoral joint metrics. Reproducibility of the QMA was tested on seven additional joints. A significant correlation was observed in cartilage thickness from matching histology-microCT pairs. The lateral compartment of operated joints had larger joint space width, thicker femoral cartilage and reduced bone volume, while osteophytes could be detected quantitatively. Measures between the in situ tibia and femur indicated an altered loading scenario. High measurement reproducibility was observed for all new parameters; with ICC ranging from 0.754 to 0.998. In conclusion, this study provides a novel 3D QMA to quantify macro and micro tissue measures in the joint of a rabbit OA model. New metrics were established consisting of: an angle to quantitatively measure osteophytes (σ), an angle to indicate erosion between the lateral and medial femoral condyles (ρ), a vector defining altered angulation (λ, α, β, γ) and a twist angle (τ) measuring instability and tissue degeneration between the femur and tibia, a length measure of joint space width (JSW), and a slope and intercept (m, Χ) of joint contact to demonstrate altered loading with disease progression, as well as traditional bone and cartilage and histo-morphometry measures. We demonstrate correlation of microCT and histology, sensitive discrimination of OA change and robust reproducibility.     

A comparison of the influence of global functional loads vs. local contact anatomy on articular cartilage thickness at the knee

Cartilage contact geometry, along with joint loading, can play an important role in determining local articular cartilage tissue stress. Thus individual variations in cartilage thickness can be associated with both individual variations in joint loading associated with activities of daily living as well as individual differences in the anatomy of the contacting surfaces of the joint. The purpose of this study was to isolate the relationship between cartilage thickness predicted by individual variations in contact surface geometry based on the radii of the femur and tibia vs. cartilage thickness predicted by individual variations in joint loading. Knee magnetic resonance (MR) images and the peak knee adduction moments during walking were obtained from 11 young healthy male subjects (age 30.5+/-5.1 years). The cartilage thicknesses and surface radii of the femoral and tibial cartilage were measured in the weight-bearing regions of the medial and lateral compartments of three-dimensional models from the MR images. The ratio of contact pressure between the medial and lateral compartments was calculated from the radii of tibiofemoral contact surface geometries. The results showed that the medial to lateral pressure ratios were not correlated with the medial to lateral cartilage thickness ratios. However, in general, pressure was higher in the lateral than medial compartments and cartilage was thicker in the lateral than medial compartments. The peak knee adduction moment showed a significant positive linear correlation with medial to lateral thickness ratio in both femur (R(2)=0.43,P<0.01) and tibia (R(2)=0.32,P<0.01). The results of this study suggest that the dynamics of walking is an important factor to describe individual differences in cartilage thickness for normal subjects.     

Early and stable upregulation of collagen type II,collagen type I and YKL40 expression levels in cartilage during early experimental osteoarthritis occurs independent of joint location and histological grading

While morphologic and biochemical aspects of degenerative joint disease (osteoarthritis [OA]) have been elucidated by numerous studies, the molecular mechanisms underlying the progressive loss of articular cartilage during OA development remain largely unknown. The main focus of the present study was to gain more insight into molecular changes during the very early stages of mechanically induced cartilage degeneration and to relate molecular alterations to histological changes at distinct localizations of the joint. Studies on human articular cartilage are hampered by the difficulty of obtaining normal tissue and early-stage OA tissue, and they allow no progressive follow-up. An experimental OA model in dogs with a slow natural history of OA (Pond–Nuki model) was therefore chosen. Anterior cruciate ligament transection (ACLT) was performed on 24 skeletally mature dogs to induce joint instability resulting in OA. Samples were taken from different joint areas after 6, 12, 24 and 48 weeks, and gene expression levels of common cartilage molecules were quantified in relation to the histological grading (modified Mankin score) of adjacent tissue. Histological changes reflected early progressive degenerative OA. Soon after ACLT, chondrocytes responded to the altered mechanical conditions by significant and stable elevation of collagen type II, collagen type I and YKL40 expression, which persisted throughout the study. In contrast to the mild to moderate histological alterations, these molecular changes were not progressive and were independent of the joint localization (tibia, femur, lateral, medial) and the extent of matrix degeneration. MMP13 remained unaltered until 24 weeks, and aggrecan and tenascinC remained unaltered until 48 weeks after ACLT. These findings indicate that elevated collagen type II, collagen type I and YKL40 mRNA expression levels are early and sensitive measures of ACLT-induced joint instability independent of a certain grade of morphological cartilage degeneration. A second phase of molecular changes in OA may begin around 48 weeks after ACLT with altered expression of further genes, such as MMP13, aggrecan and tenascin. Molecular changes observed in the present study suggest that dog cartilage responds to degenerative conditions by regulating the same genes in a similar direction as that observed for chondrocytes in late human OA.     

In vivo whole body and appendicular bone mineral density in rats: a dual energy X-ray absorptiometry study

Bone mineral density (BMD) of the whole body and hind limb of young adult rats, with and without a sham-operated stifle joint was studied, using dual energy x-ray absorptiometry (DEXA) at three time points. Data from the whole body scan were used for analyses of BMD, bone mineral content (BMC), fat, lean, body weight (BW), percentage of BMC (%BMC), percentage of fat (%fat), and percentage of lean (%lean), none of which were significantly different between the groups at any time point. Significant (P < 0.05) differences in BMD, BMC, %BMC, BW, fat, %fat, and %lean were apparent at the second and third scans, compared with the initial scan, within both groups. Changes in whole body BMD, BMC, and %BMC as well as BW were highly correlated with time in both groups. In the hind limb scans, regions of interest (ROIs) were created to obtain values of BMD and BMC from the whole femur, whole tibia including the fibula, distal portion of the femur, and proximal portion of the tibia. Significant differences were not found between the groups for any ROIs. However, significant BMD and BMC increases were evident in all ROIs at the second and third scans, compared with the initial scan. Similar to those in the whole body scan, BMD and BMC obtained from ROIs were highly correlated with time. The positioning technique for the whole body and appendicular scans was analyzed by calculating percentage of the coefficient of variation (%CV) at the beginning of the study. The %CV was low and acceptable in ROIs for the hind limb and for all parameters of the whole body scan, except fat. The results suggest that in vivo DEXA scanning of the rat whole body and appendicular skeleton is highly reproducible and useful to study the whole skeleton, as well as a region of a long bone of the rat. Values for the sham-operated rats were not significantly different from those for the untreated controls, which suggests that soft tissue damage around the stifle joint did not alter BMD in the subchondral bone of the distal portion of the femur and proximal portion of the tibia.     

Early and stable upregulation of collagen type II, collagen type I and YKL40 expression levels in cartilage during early experimental osteoarthritis occurs independent of joint location and histological grading

While morphologic and biochemical aspects of degenerative joint disease (osteoarthritis [OA]) have been elucidated by numerous studies, the molecular mechanisms underlying the progressive loss of articular cartilage during OA development remain largely unknown. The main focus of the present study was to gain more insight into molecular changes during the very early stages of mechanically induced cartilage degeneration and to relate molecular alterations to histological changes at distinct localizations of the joint. Studies on human articular cartilage are hampered by the difficulty of obtaining normal tissue and early-stage OA tissue, and they allow no progressive follow-up. An experimental OA model in dogs with a slow natural history of OA (Pond-Nuki model) was therefore chosen. Anterior cruciate ligament transection (ACLT) was performed on 24 skeletally mature dogs to induce joint instability resulting in OA. Samples were taken from different joint areas after 6, 12, 24 and 48 weeks, and gene expression levels of common cartilage molecules were quantified in relation to the histological grading (modified Mankin score) of adjacent tissue. Histological changes reflected early progressive degenerative OA. Soon after ACLT, chondrocytes responded to the altered mechanical conditions by significant and stable elevation of collagen type II, collagen type I and YKL40 expression, which persisted throughout the study. In contrast to the mild to moderate histological alterations, these molecular changes were not progressive and were independent of the joint localization (tibia, femur, lateral, medial) and the extent of matrix degeneration. MMP13 remained unaltered until 24 weeks, and aggrecan and tenascinC remained unaltered until 48 weeks after ACLT. These findings indicate that elevated collagen type II, collagen type I and YKL40 mRNA expression levels are early and sensitive measures of ACLT-induced joint instability independent of a certain grade of morphological cartilage degeneration. A second phase of molecular changes in OA may begin around 48 weeks after ACLT with altered expression of further genes, such as MMP13, aggrecan and tenascin. Molecular changes observed in the present study suggest that dog cartilage responds to degenerative conditions by regulating the same genes in a similar direction as that observed for chondrocytes in late human OA.     

Early regional adaptation of periarticular bone mineral density after anterior cruciate ligament injury.

The present study measured early-stage adaptation of bone mineral (BMD) in the periarticular cancellous bone of the canine knee (stifle) joint after anterior cruciate ligament (ACL) transection (ACLX). Regional changes in BMD in the tibia and femur were analyzed by using quantitative computed tomography (qCT) at 3 wk and 12 wk after unilateral ACLX to determine whether there were focal points for BMD changes and whether these changes occurred early after the induced knee injury. BMD decreased rapidly after ACLX, and the more pronounced response was in the femur. In the 3-wk group, there were decreases in BMD in the tibia and the femur, and these changes were significant in the posterior-medial region of the femur, which showed a decrease of BMD in the ACLX limb (-0.048 +/- 0.011 g/cm(3)). In the 12-wk group, all regions in the tibia and femur exhibited significant decreases in BMD, and the average decrease was greatest in the posterior-medial region of the femur (-0.142 +/- 0.021 g/cm(3)). The regions of pronounced periarticular cancellous BMD adaptation corresponded to observed focal cartilage defects. Early decreases in BMD in the injured knee may be related to altered loading and kinematics in the knee and may be an important link in the pathogenesis of posttraumatic osteoarthritis.     

Unstable Stifles without Clinical or Radiographic Osteoarthritis in Young Goats: An Experimental Study

Thirteen young, castrated male goats had instability of one stifle (knee joint) created by surgical transection of the cranial cruciate ligament, but did not develop any signs of osteoarthritis (OA) in treated joints when confined in limited space for 8 months. At the end of the experiment, the instability in the stifles had not improved, the joints were normal at radiographic examination, there were no signs of inflammation in the synovial membrane or joint capsule, and fibrosis in these tissues was not evident. The articular cartilage was normal both visually and histologically. This may indicate that the young age of the goats and the restricted physical activity on soft floor had prevented the expected development of OA in the experimantally operated joints. Synovial fluid volumes and proteoglycan concentration were measured in the treated and control joints in 6 of the goats. There seemed to be increased quantity of the proteoglycan aggrecan in the synovial fluid from the treated joints compared to the contralateral joints throughout the course of this study. It was concluded that the turnover of aggrecan in the articular cartilage of the treated joints may have been increased.     

In vivo tibiofemoral cartilage deformation during the stance phase of gait

The knowledge of articular cartilage contact biomechanics in the knee joint is important for understanding the joint function and cartilage pathology. However, the in vivo tibiofemoral articular cartilage contact biomechanics during gait remains unknown. The objective of this study was to determine the in vivo tibiofemoral cartilage contact biomechanics during the stance phase of treadmill gait. Eight healthy knees were magnetic resonance (MR) scanned and imaged with a dual fluoroscopic system during gait on a treadmill. The tibia, femur and associated cartilage were constructed from the MR images and combined with the dual fluoroscopic images to determine in vivo cartilage contact deformation during the stance phase of gait. Throughout the stance phase of gait, the magnitude of peak compartmental contact deformation ranged between 7% and 23% of the resting cartilage thickness and occurred at regions with thicker cartilage. Its excursions in the anteroposterior direction were greater in the medial tibiofemoral compartment as compared to those in the lateral compartment. The contact areas throughout the stance phase were greater in the medial compartment than in the lateral compartment. The information on in vivo tibiofemoral cartilage contact biomechanics during gait could be used to provide physiological boundaries for in vitro testing of cartilage. Also, the data on location and magnitude of deformation among non-diseased knees during gait could identify where loading and later injury might occur in diseased knees.     

Osteochondromatosis in a Rhesus macaque (Macaca mulatta)

A 5-y-old, male, rhesus macaque (Macaca mulatta) presented with a prominent mass slightly anteriomedial to the right stifle. On exam, multiple radiopaque masses were identified protruding from the mid- and distal femur. Lateral and anteroposterior radiographs of the right stifle region revealed multiple exophytic masses arising from the femur, with mild bony reaction of the proximal tibia. Histologic examination of biopsy tissue revealed woven and lamellar bone with granulation tissue and skeletal muscle. Because the macaque was exhibiting no lameness or signs of pain, we decided to monitor the progression of the masses. Minimal change was noted during the time prior to study termination at 6.5 y of age. Necropsy revealed that the bony masses were cartilage-capped lesions arising near the growth plate of the distal femur and midshaft of the femur and tibia. Histologic examination revealed chondro-osseous exophytic growths that blended imperceptibly with the cortex and spongiosa of the femur, consistent with a final diagnosis of multiple osteochondromas.     

Development and validation of a multi-body model of the canine stifle joint

Multi-body musculoskeletal models that can be used concurrently to predict joint contact pressures and muscle forces would be extremely valuable in studying the mechanics of joint injury. The purpose of this study was to develop an anatomically correct canine stifle joint model and validate it against experimental data. A cadaver pelvic limb from one adult dog was used in this study. The femoral head was subjected to axial motion in a mechanical tester. Kinematic and force data were used to validate the computational model. The maximum RMS error between the predicted and measured kinematics during the complete testing cycle was 11.9 mm translational motion between the tibia and the femur and 4.3° rotation between patella and femur. This model is the first step in the development of a musculoskeletal model of the hind limb with anatomically correct joints to study cartilage loading under dynamic conditions.     

A finite element model of the human knee joint for the study of tibio-femoral contact

As a step towards developing a finite element model of the knee that can be used to study how the variables associated with a meniscal replacement affect tibio-femoral contact, the goals of this study were 1) to develop a geometrically accurate three-dimensional solid model of the knee joint with special attention given to the menisci and articular cartilage, 2) to determine to what extent bony deformations affect contact behavior, and 3) to determine whether constraining rotations other than flexion/extension affects the contact behavior of the joint during compressive loading. The model included both the cortical and trabecular bone of the femur and tibia, articular cartilage of the femoral condyles and tibial plateau, both the medial and lateral menisci with their horn attachments, the transverse ligament, the anterior cruciate ligament, and the medial collateral ligament. The solid models for the menisci and articular cartilage were created from surface scans provided by a noncontacting, laser-based, three-dimensional coordinate digitizing system with an root mean squared error (RMSE) of less than 8 microns. Solid models of both the tibia and femur were created from CT images, except for the most proximal surface of the tibia and most distal surface of the femur which were created with the three-dimensional coordinate digitizing system. The constitutive relation of the menisci treated the tissue as transversely isotropic and linearly elastic. Under the application of an 800 N compressive load at 0 degrees of flexion, six contact variables in each compartment (ie., medial and lateral) were computed including maximum pressure, mean pressure, contact area, total contact force, and coordinates of the center of pressure. Convergence of the finite element solution was studied using three mesh sizes ranging from an average element size of 5 mm by 5 mm to 1 mm by 1 mm. The solution was considered converged for an average element size of 2 mm by 2 mm. Using this mesh size, finite element solutions for rigid versus deformable bones indicated that none of the contact variables changed by more than 2% when the femur and tibia were treated as rigid. However, differences in contact variables as large as 19% occurred when rotations other than flexion/extension were constrained. The largest difference was in the maximum pressure. Among the principal conclusions of the study are that accurate finite element solutions of tibio-femoral contact behavior can be obtained by treating the bones as rigid. However, unrealistic constraints on rotations other than flexion/extension can result in relatively large errors in contact variables.     

Lectin-binding in normal and osteoarthrotic articular cartilage from STR/1N-mouse knee joints

Fluorescein-isothiocyanate (FITC) labeled lectins were used to study the distribution pattern of specific binding-sites in histological sections of normal and osteoarthrotic articular cartilage from the mouse knee joint. Male inbred mice of the STR/1N-strain develop spontaneous arthrotic articular cartilage lesions on the medial condyle of tibia and femur. The varus-deformity of the knee joint leads to a recurrent medial patellar luxation with osteoarthrotic defects on the medial part of the facies patellaris femoris. It was demonstrated that the lectin staining pattern of osteoarthrotic articular cartilage, especially on the facies patellaris femoris, was different from that of normal articular cartilage. The differences in lectin staining corresponded to those observed between normal and fibrillated articular cartilage from human patellae. The normal articular cartilage of the mouse knee joint possessed lectin binding-sites for Concanavalin A (ConA) and wheat germ agglutinin (WGA), but not for Ulex europaeus agglutinin (UEA), soy bean agglutinin (SBA) and peanut agglutinin (PNA). In addition to the completely changed distribution pattern of ConA and WGA in osteoarthrotic cartilage, SBA, PNA and UEA developed distinct staining patterns particular to the fibrillated areas of arthrotic cartilage. The increased lectin-binding to arthrotic articular cartilage may be due to unmasking of sugars in the course of bondage breakdown in fibrillated cartilage or the production of pathological glycoproteins. It is evident that lectins can demonstrate minute differences between normal and arthrotic cartilage and it is concluded, therefore, that lectins are sensitive and specific tools for the study of degenerative joint diseases.     

Intra-articular injection of micronized dehydrated human amnion/chorion membrane attenuates osteoarthritis development

Introduction

Micronized dehydrated human amnion/chorion membrane (μ-dHACM) is derived from donated human placentae and has anti-inflammatory, low immunogenic and anti-fibrotic properties. The objective of this study was to quantitatively assess the efficacy of μ-dHACM as a disease modifying intervention in a rat model of osteoarthritis (OA). It was hypothesized that intra-articular injection of μ-dHACM would attenuate OA progression.

Methods

Lewis rats underwent medial meniscal transection (MMT) surgery to induce OA. Twenty four hours post-surgery, μ-dHACM or saline was injected intra-articularly into the rat joint. Naïve rats also received μ-dHACM injections. Microstructural changes in the tibial articular cartilage were assessed using equilibrium partitioning of an ionic contrast agent (EPIC-μCT) at 21 days post-surgery. The joint was also evaluated histologically and synovial fluid was analyzed for inflammatory markers at 3 and 21 days post-surgery.

Results

There was no measured baseline effect of μ-dHACM on cartilage in naïve animals. Histological staining of treated joints showed presence of μ-dHACM in the synovium along with local hypercellularity at 3 and 21 days post-surgery. In MMT animals, development of cartilage lesions at 21 days was prevented and number of partial erosions was significantly reduced by treatment with μ-dHACM. EPIC-μCT analysis quantitatively showed that μ-dHACM reduced proteoglycan loss in MMT animals.

Conclusions

μ-dHACM is rapidly sequestered in the synovial membrane following intra-articular injection and attenuates cartilage degradation in a rat OA model. These data suggest that intra-articular delivery of μ-dHACM may have a therapeutic effect on OA development.     

Forced mobilization accelerates pathogenesis: characterization of a preclinical surgical model of osteoarthritis

Preclinical osteoarthritis (OA) models are often employed in studies investigating disease-modifying OA drugs (DMOADs). In this study we present a comprehensive, longitudinal evaluation of OA pathogenesis in a rat model of OA, including histologic and biochemical analyses of articular cartilage degradation and assessment of subchondral bone sclerosis. Male Sprague-Dawley rats underwent joint destabilization surgery by anterior cruciate ligament transection and partial medial meniscectomy. The contralateral joint was evaluated as a secondary treatment, and sham surgery was performed in a separate group of animals (controls). Furthermore, the effects of walking on a rotating cylinder (to force mobilization of the joint) on OA pathogenesis were assessed. Destabilization-induced OA was investigated at several time points up to 20 weeks after surgery using Osteoarthritis Research Society International histopathology scores, in vivo micro-computed tomography (CT) volumetric bone mineral density analysis, and biochemical analysis of type II collagen breakdown using the CTX II biomarker. Expression of hypertrophic chondrocyte markers was also assessed in articular cartilage. Cartilage degradation, subchondral changes, and subchondral bone loss were observed as early as 2 weeks after surgery, with considerable correlation to that seen in human OA. We found excellent correlation between histologic changes and micro-CT analysis of underlying bone, which reflected properties of human OA, and identified additional molecular changes that enhance our understanding of OA pathogenesis. Interestingly, forced mobilization exercise accelerated OA progression. Minor OA activity was also observed in the contralateral joint, including proteoglycan loss. Finally, we observed increased chondrocyte hypertrophy during pathogenesis. We conclude that forced mobilization accelerates OA damage in the destabilized joint. This surgical model of OA with forced mobilization is suitable for longitudinal preclinical studies, and it is well adapted for investigation of both early and late stages of OA. The time course of OA progression can be modulated through the use of forced mobilization.     

Therapeutic effects of bone marrow mesenchymal stem cells-derived exosomes on osteoarthritis

Mesenchymal stem cells (MSCs) have shown chondroprotective effects in clinical models of osteoarthritis (OA). However, effects of MSC-derived exosomes on OA remain unclear. The study aimed to investigate the therapeutic potential of exosomes from human bone marrow MSCs (BM-MSCs) in alleviating OA. The anterior cruciate ligament transection (ACLT) and destabilization of the medial meniscus (DMM) surgery were performed on the knee joints of a rat OA model, followed by intra-articular injection of BM-MSCs or their exosomes. In addition, BM-MSC-derived exosomes were administrated to primary human chondrocytes to observe the functional and molecular alterations. Both of BM-MSCs and BM-MSC-derived exosomes alleviated cartilage destruction and subchondral bone remodelling in OA rat model. Administration of BM-MSCs and exosomes could reduce joint damage and restore the trabecular bone volume fraction, trabecular number and connectivity density of OA rats. In addition, in vitro assays showed that BM-MSCs-exosomes could maintain the chondrocyte phenotype by increasing collagen type II synthesis and inhibiting IL-1β–induced senescence and apoptosis. Furthermore, exosomal lncRNA MEG-3 also reduced the senescence and apoptosis of chondrocytes induced by IL-1β, indicating that lncRNA MEG-3 might partially account the anti-OA effects of BM-MSC exosomes. The exosomes from BM-MSCs exerted beneficial therapeutic effects on OA by reducing the senescence and apoptosis of chondrocytes, suggesting that MSC-derived exosomes might provide a candidate therapy for OA treatment.     

Protein modification by deamidation indicates variations in joint extracellular matrix turnover

As extracellular proteins age, they undergo and accumulate nonenzymatic post-translational modifications that cannot be repaired. We hypothesized that these could be used to systemically monitor loss of extracellular matrix due to chronic arthritic diseases such as osteoarthritis (OA). To test this, we predicted sites of deamidation in cartilage oligomeric matrix protein (COMP) and confirmed, by mass spectroscopy, the presence of deamidated (Asp(64)) and native (Asn(64)) COMP epitopes (mean 0.95% deamidated COMP (D-COMP) relative to native COMP) in cartilage. An Asp(64), D-COMP-specific ELISA was developed using a newly created monoclonal antibody 6-1A12. In a joint replacement study, serum D-COMP (p = 0.017), but not total COMP (p = 0.5), declined significantly after replacement demonstrating a joint tissue source for D-COMP. In analyses of 450 participants from the Johnston County Osteoarthritis Project controlled for age, gender, and race, D-COMP was associated with radiographic hip (p < 0.0001) but not knee (p = 0.95) OA severity. In contrast, total COMP was associated with radiographic knee (p < 0.0001) but not hip (p = 0.47) OA severity. D-COMP was higher in soluble proteins extracted from hip cartilage proximal to OA lesions compared with remote from lesions (p = 0.007) or lesional and remote OA knee (p < 0.01) cartilage. Total COMP in cartilage did not vary by joint site or proximity to the lesion. This study demonstrates the presence of D-COMP in articular cartilage and the systemic circulation, and to our knowledge, it is the first biomarker to show specificity for a particular joint site. We believe that enrichment of deamidated epitope in hip OA cartilage indicates a lesser repair response of hip OA compared with knee OA cartilage.