Long-term periarticular bone adaptation in a feline knee injury model for post-traumatic experimental osteoarthritis

Knee Joint Osteoarthritis in Overweight Cats: The Clinical and Radiographic Findings

Despite a high prevalence of osteoarthritis (OA) reported in the domesticated cat population, studies on feline knee joint OA are scarcer. Knee joint OA is a painful, age-related, chronic degenerative joint disease that significantly affects cats' activity and quality of life. In dogs and humans, one may consider overweight as a risk factor for the development and progression of knee joint OA; therefore, this study aims to assess the severity of knee joint OA in the body-weight-related groups of cats concerning clinical symptoms and radiographic signs. The study was conducted on sixty-four (n = 64) cats with confirmed OA. The demographic data on sex, neutering, age, and breed were collected. Then, the body condition score (BCS) was assessed, and each cat was allocated to the underweight, normal-weight, or overweight group. Within clinical symptoms, joint pain, joint swelling, joint deformities, lameness, reluctance to move, and apathy were graded. Based on the radiographic signs, minor OA, mild OA, moderate OA, and severe OA were scored. Prevalence and co-occurrence of the studied variables were then assessed. Joint pain was elicited in 20-31% of the OA-affected joints, joint deformities in 21-30%, and lameness in 20-54%, with no differences between weight-related groups. Severe OA was detected in 10-16% of the OA-affected joints, with no differences between weight-related groups. Severe OA in feline knee joints appears with similar frequency in overweight, underweight, and normal-weight cats. However, the general prevalence of clinical symptoms and radiographic signs is different in overweight cats.

Patellofemoral joint loading and early osteoarthritis after ACL reconstruction

Patellofemoral joint (PFJ) osteoarthritis is common following anterior cruciate ligament reconstruction (ACLR) and may be linked with altered joint loading. However, little is known about the cross-sectional and longitudinal relationship between PFJ loading and osteoarthritis post-ACLR. This study tested if altered PFJ loading is associated with prevalent and worsening early PFJ osteoarthritis post-ACLR. Forty-six participants (mean ± 1 SD age 26 ± 5 years) approximately 1-year post-ACLR underwent magnetic resonance imaging (MRI) and biomechanical assessment of their reconstructed knee. Trunk and lower-limb kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward hop. These data were input into a musculoskeletal model to calculate the PFJ contact force. Follow-up MRI was completed on 32 participants at 5-years post-ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ loading and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion at 1-year post-ACLR) and worsening PFJ osteoarthritis (i.e., incident/progressive PFJ cartilage lesion between 1- and 5-years post-ACLR). A lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1-year post-ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI]: 1.02-1.85) and a higher risk of worsening PFJ osteoarthritis between 1- and 5-years post-ACLR (n = 9 [28.1%]; risk ratio: 1.55, 95% CI: 1.13-2.11). Young adults post-ACLR who exhibited lower PFJ loading during hopping were more likely to have early PFJ osteoarthritis at 1-year and worsening PFJ osteoarthritis between 1- and 5-years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of lower PFJ loading post-ACLR.

Mice Lacking Wnt9a or Wnt4 Are Prone to Develop Spontaneous Osteoarthritis With Age and Display Alteration in Either the Trabecular or Cortical Bone Compartment

Osteoarthritis (OA) is a common degenerative disease of the joint, with a complex multifactorial not yet fully understood etiology. Over the past years, the Wnt signaling pathway has been implicated in osteoarthritis. In a recent genomewide association study (GWAS), the chromosomal location on chromosome 1, linked to the Wnt3a-Wnt9a gene locus, was identified as the most significant locus associated with a thumb osteoarthritis endophenotype. Previously, it was shown that WNT9a is involved in maintaining synovial cell identity in the elbow joint during embryogenesis. Here, we report that the conditional loss of Wnt9a in the Prx1-Cre expressing limb mesenchyme or Prg4-CreER expressing cells predispositions the mice to develop spontaneous OA-like changes with age. In addition, the trabecular bone volume is altered in these mice. Similarly, mice with a conditional loss of Wnt4 in the limb mesenchyme are also more prone to develop spontaneously OA-like joint alterations with age. These mice display additional alterations in their cortical bone. The combined loss of Wnt9a and Wnt4 increased the likelihood of the mice developing osteoarthritis-like changes and enhanced disease severity in the affected mice. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The cat as a small dog?-Comparison of trabecular and cortical bone microarchitecture of radius and ulna in cats and small dogs using microcomputed tomography

The forearms of dogs and cats do not only differ anatomically from each other, but there are also differences in prevalence of radius and ulna fractures between the two species. The prevalence of antebrachial fractures is 18.0% in dogs and 2.0–8.0% in cats. Many studies focus solely on the trabecular and cortical bone structure of dogs and the characteristics of the cat are often disregarded.

The aim of this study was to evaluate the trabecular structure parameters [bone volume fraction per total volume (BV/TV), bone surface per total volume (BS/BV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), connectivity density (Conn. D), degree of anisotropy (DA)] and the diaphyseal cortical bone density (Mean Density) of the antebrachium in cats and small dogs to visualise their differences.

For this purpose, a total of 32 forearms of cats (n = 8) and small dogs (n = 8) were evaluated using microcomputed tomography and the findings were compared.

The results of the study showed that cats had higher values for BV/TV, Tb.Th, Tb.Sp, DA and Mean Density and lower values for BS/BV, Tb.N and Conn.D at radius and ulna compared to dogs.

According to the results of this study, the higher bone volume fraction (BV/TV), thicker trabeculae (Tb.Th), increased anisotropy (DA) and significantly higher diaphyseal cortical density (Mean Density) could contribute to the lower fracture risk of the antebrachium in cats compared to small dogs.

Quantitative measures of bone shape, cartilage morphometry and joint alignment are associated with disease in an ACLT and MMx rat model of osteoarthritis

Multi-scale, subject-specific quantitative methods to characterize and monitor osteoarthritis in animal models and therapeutic treatments could help reveal causal relationships in disease development and distinguish treatment strategies. In this work, we demonstrate a reproducible and sensitive quantitative image analysis to characterize bone, cartilage and joint measures describing a rat model of post-traumatic osteoarthritis. Eleven 3-month-old male Wistar rats underwent medial anterior cruciate ligament (ACL) transection and medial meniscectomy on the right knee to destabilise the right tibiofemoral joint. They were sacrificed 6 weeks post-surgery and a silicon-based micro-bead contrast agent was injected in the joint space, before scanning with micro-computed tomography (microCT). Subsequently, 3D quantitative morphometric analysis (QMA), previously developed for rabbit joints, was performed. This included cartilage, subchondral cortical and epiphyseal bone measures, as well as novel tibiofemoral joint metrics. Semi-quantitative evaluation was performed on matching two-dimensional (2D) histology and microCT images. Reproducibility of the QMA was tested on eleven age-matched additional joints. The results indicate the QMA method is accurate and reproducible and that microCT-derived cartilage measurements are valid for the analysis of rat joints. The pathologic changes caused by transection of the ACL and medial meniscectomy were reflected in measurements of bone shape, cartilage morphology, and joint alignment. Furthermore, we were able to identify model-specific predictive parameters based on morphometric parameters measured with the QMA.

Comparative microcomputed tomographic structural analysis of the trabecular and cortical bone architecture of radius and ulna in toy dog breeds

Radius and ulna fractures can be detected in dogs with an incidence of 18.0% and occur more frequently in toy breeds with increased complication rates. The reasons for the predisposition and the increased complication rate of antebrachial fractures in toy breeds are not yet fully understood. The aim of this study was to research the associated mechanisms by investigating the trabecular structure parameters (BV/TV (%), Tb.N (mm^-1), Tb.Th (mm), Tb.Sp (mm), Conn. D (mm^-3), DA) and the cortical bone density (Mean Density (mg HA/ccm)) for toy breeds and small dogs of other breeds using microcomputed tomography and to identify the differences between both groups. A total of 70 forearms, originating from toy breeds (n = 36) and small dogs of other breeds (n = 34) were evaluated by microcomputed tomography. The results of this study showed a lower bone volume fraction (BV/TV), more (Tb.N) but thinner trabeculae (Tb.Th) with greater separation (Tb.Sp) and decreased diaphyseal cortical density (Mean Density) in toy breed dogs. This could thus contribute to the increased risk of antebrachial fractures in toy breeds. Within the group of toy breeds inhomogeneous results were observed, whereby the values of the Chihuahuas deviated. This breed had significantly thinner trabeculae (Tb.Th) with a greater trabecular separation (Tb.Sp), lower bone volume fraction (BV/TV) and significantly lower diaphyseal cortical density (Mean Density). These parameters could therefore indicate an increased antebrachial fracture and complication risk, especially in Chihuahuas.

Structural Consequences of a Partial Anterior Cruciate Ligament Injury on Remaining Joint Integrity: Evidence for Ligament and Bone Changes Over Time in an Ovine Model

BACKGROUND

Severe injury to the knee joint often results in accelerated posttraumatic osteoarthritis (PTOA). In an ovine knee injury model, altered kinematics and degradation of the cartilage have been observed at 20 and 40 weeks after partial anterior cruciate ligament (ACL) transection (p-ACL Tx) surgery. However, changes to the integrity of the remaining intact intra-articular ligaments (posterolateral [PL] band and posterior cruciate ligament [PCL]) as well as the subchondral bone after anteromedial (AM) band Tx remain to be characterized.

PURPOSE

(1) To investigate histological alterations to the remaining intact intra-articular ligaments, the synovium, and the infrapatellar fat pad (IPFP) and (2) to quantify subchondral bone changes at the contact surfaces of the proximal tibia at 20 and 40 weeks after AM band Tx.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Mature female Suffolk cross sheep were allocated into 3 groups: nonoperative controls (n = 6), 20 weeks after partial ACL transection (p-ACL Tx; n = 5), and 40 weeks after p-ACL Tx (n = 6). Ligament, synovium, and IPFP sections were stained and graded. Tibial subchondral bone microarchitecture was assessed using high-resolution peripheral quantitative computed tomography.

RESULTS

p-ACL Tx of the AM band led to significant change in histological scores of the PL band and the PCL at 20 weeks after p-ACL Tx (P = .031 and P = .033, respectively) and 40 weeks after p-ACL Tx (P = .011 and P = .029) as compared with nonoperative controls. Alterations in inflammatory cells and collagen fiber orientation contributed to the greatest extent of the combined histological score in the PL band and PCL. p-ACL Tx did not lead to chronic activation of the synovium or IPFP. Trabecular bone mineral density was strongly inversely correlated with combined gross morphological damage in the top and middle layers of the subchondral bone in the lateral tibial plateau for animals at 40 weeks after p-ACL Tx.

CONCLUSION

p-ACL Tx influences the integrity (biology and structure) of remaining intact intra-articular ligaments and bone microarchitecture in a partial knee injury ovine model.

CLINICAL RELEVANCE

p-ACL Tx leads to alterations in structural integrity of the remaining intact ligaments and degenerative changes in the trabecular bone mineral density, which may be detrimental to the injured athlete's knee joint in the long term.

Topographic modeling of early human osteoarthritis in sheep

Articular cartilage damage occurring during early osteoarthritis (OA) is a key event marking the development of the disease. Here, we modeled early human OA by gathering detailed spatiotemporal data from surgically induced knee OA development in sheep. We identified a specific topographical pattern of osteochondral changes instructed by a defined meniscal injury, showing that both cartilage and subchondral bone degeneration are initiated from the region adjacent to the damage. Alterations of the subarticular spongiosa arising locally and progressing globally disturbed the correlations of cartilage with subchondral bone seen at homeostasis and were indicative of disease progression. We validated our quantitative findings against human OA, showing a similar pattern of early OA correlating with regions of meniscal loss and an analogous late critical disturbance within the entire osteochondral unit. This translational model system can be used to elucidate mechanisms of OA development and provides a roadmap for investigating regenerative therapies.

Direct Validation of Model-Predicted Muscle Forces in the Cat Hindlimb During Locomotion

Various methods are available for simulating the movement patterns of musculoskeletal systems and determining individual muscle forces, but the results obtained from these methods have not been rigorously validated against experiment. The aim of this study was to compare model predictions of muscle force derived for a cat hindlimb during locomotion against direct measurements of muscle force obtained in vivo. The cat hindlimb was represented as a 5-segment, 13-degrees-of-freedom (DOF), articulated linkage actuated by 25 Hill-type muscle-tendon units (MTUs). Individual muscle forces were determined by combining gait data with two widely used computational methods-static optimization and computed muscle control (CMC)-available in opensim, an open-source musculoskeletal modeling and simulation environment. The forces developed by the soleus, medial gastrocnemius (MG), and tibialis anterior muscles during free locomotion were measured using buckle transducers attached to the tendons. Muscle electromyographic activity and MTU length changes were also measured and compared against the corresponding data predicted by the model. Model-predicted muscle forces, activation levels, and MTU length changes were consistent with the corresponding quantities obtained from experiment. The calculated values of muscle force obtained from static optimization agreed more closely with experiment than those derived from CMC.

Towards secondary prevention of early knee osteoarthritis

Osteoarthritis (OA) of the knee is the most common arthritic disease, yet a convincing drug treatment is not available. The current narrative review focuses on integration of scientific evidence and professional experience to illustrate which management approaches can be taken for prototypical individual patient profiles with early knee OA. Animal models suggest that: (1) OA can progress even in the presence of fully recovered movement kinetics, kinematics and muscle activation patterns; (2) muscle weakness is an independent risk factor for the onset and possibly the rate of progression of knee OA; (3) onset and progression of OA are not related to body weight but appear to depend on the percentage of body fat. From studies in the human model, one could postulate that risk factors associated with progression of knee OA include genetic traits, preceding traumatic events, obesity, intensity of pain at baseline, static and dynamic joint malalignment and reduced muscle strength. Taken this into account, an individual can be identified as early knee OA at high risk for disease progression. A holistic patient-tailored management including education, supportive medication, weight loss, exercise therapy (aerobic, strengthening and neuromuscular) and behavioural approaches to improve self-management of early knee OA is discussed in individual prototypic patients. Secondary prevention of early knee OA provides a window of opportunity to slow down or even reverse the disease process. Yet, as the sheer number of patients early in the OA disease process is probably large, a more structured approach is needed to provide appropriate care depending on the patient's individual risk profile.

Subchondral Trabecular Rod Loss and Plate Thickening in the Development of Osteoarthritis

Developing effective treatment for osteoarthritis (OA), a prevalent and disabling disease, has remained a challenge, primarily because of limited understanding of its pathogenesis and late diagnosis. In the subchondral bone, rapid bone loss after traumatic injuries and bone sclerosis at the advanced stage of OA are well-recognized hallmarks of the disease. Recent studies have further demonstrated the crucial contribution of subchondral bone in the development of OA. However, the microstructural basis of these bone changes has not been examined thoroughly, and the paradox of how abnormal resorption can eventually lead to bone sclerosis remains unanswered. By applying a novel microstructural analysis technique, individual trabecula segmentation (ITS), to micro-computed tomography (μCT) images of human OA knees, we have identified a drastic loss of rod-like trabeculae and thickening of plate-like trabeculae that persisted in all regions of the tibial plateau, underneath both severely damaged and still intact cartilage. The simultaneous reduction in trabecular rods and thickening of trabecular plates provide important insights to the dynamic and paradoxical subchondral bone changes observed in OA. Furthermore, using an established guinea pig model of spontaneous OA, we discovered similar trabecular rod loss and plate thickening that preceded cartilage degradation. Thus, our study suggests that rod-and-plate microstructural changes in the subchondral trabecular bone may play an important role in the development of OA and that advanced microstructural analysis techniques such as ITS are necessary in detecting these early but subtle changes. With emerging high-resolution skeletal imaging modalities such as the high-resolution peripheral quantitative computed tomography (HR-pQCT), trabecular rod loss identified by ITS could potentially be used as a marker in assessing the progression of OA in future longitudinal studies or clinical diagnosis. © 2017 American Society for Bone and Mineral Research.

Effects of treadmill running with different intensity on rat subchondral bone

Subchondral bone (SB) is recognized as a key factor in normal joint protection, not only does it provide a shock absorbing and supportive function for the cartilage, but it may also be important for cartilage metabolism. Mechanical loading is considered to be a critical regulator of skeletal homeostasis, including bone and cartilage. It is suggested that both cartilage and bone may respond to mechanical loading in an intensity-dependent manner. In this report, we have discovered that the subchondral plate became thicker with higher bone mineral density (BMD) and lower porosity, while trabecular bone became more plate-like and denser with higher BMD in high-intensity running (HIR) group. Further, HIR led to highly remodeled, less mineralized, and stiffer subchondral plate and trabecular bone. On the contrary, low-intensity running and moderate-intensity running failed to result in considerable changes in microstructure, composition and hardness. Our findings suggested that running affects SB in an intensity-dependent manner. In addition, HIR may induce change in organization and composition of SB, and consequently alter its mechanical properties. HIR-induced "brittle and stiff" SB may adversely affect the overlying articular cartilage.

A study of acute and chronic tissue changes in surgical and traumatically-induced experimental models of knee joint injury using magnetic resonance imaging and micro-computed tomography

OBJECTIVE

The objective of this study was to monitor the progression of joint damage in two animal models of knee joint trauma using two non-invasive, clinically available imaging modalities.

METHODS

A 3-T clinical magnet and micro-computed tomography (μCT) was used to document changes immediately following injury (acute) and post-injury (chronic) at time points of 4, 8, or 12 weeks. Joint damage was recorded at dissection and compared to the chronic magnetic resonance imaging (MRI) record. Fifteen Flemish Giant rabbits were subjected to a single tibiofemoral compressive impact (ACLF), and 18 underwent a combination of anterior cruciate ligament (ACL) and meniscal transection (mACLT).

RESULTS

All ACLF animals experienced ACL rupture, and 13 also experienced acute meniscal damage. All ACLF and mACLT animals showed meniscal and articular cartilage damages at dissection. Meniscal damage was documented as early as 4 weeks and worsened in 87% of the ACLF animals and 71% of the mACLT animals. Acute cartilage damage also developed further and increased in occurrence with time in both models. A progressive decrease in bone quantity and quality was documented in both models. The MRI data closely aligned with dissection notes suggesting this clinical tool may be a non-invasive method for documenting joint damage in lapine models of knee joint trauma.

CONCLUSIONS

The study investigates the acute to chronic progression of meniscal and cartilage damage at various time points, and chronic changes to the underlying bone in two models of posttraumatic osteoarthritis (PTOA), and highlights the dependency of the model on the location, type, and progression of damage over time.

Do cats with a cranial cruciate ligament injury and osteoarthritis demonstrate a different gait pattern and behaviour compared to sound cats?

Background

Osteoarthritis (OA) is a common cause of chronic pain and dysfunction in older cats. The majority of cats with OA do not show signs of overt lameness, yet cats with orthopaedic disease are known to redistribute their body weight from the affected limb. OA can cause changes in the cat’s behaviour, which is often misinterpreted as signs of aging. The aim of the present study was to investigate if cats with a previous cranial cruciate ligament (CCL) injury perform differently on the pressure mat and exhibit different behaviour compared to sound cats according to the owner´s subjective assessment. Ten cats with a previous CCL injury were assessed with a pressure mat system and their owners were asked to complete an assessment questionnaire. The results were compared to those of 15 sound cats, matched to have the same weight and body condition score.

Results

The front/hind limb index for peak vertical force (PVF) was significantly higher for CCL cats, and there was a decreased PVF and vertical impulse (VI) on the affected hindlimb compared to the unaffected one. The results indicate that cats with a previous CCL injury put less weight, on the affected hindlimb but for a longer time. There was a significantly higher owner assessment questionnaire score for the group of cats with CCL injury compared to sound cats.

Conclusions

Cats with a previous CCL injury have a different gait pattern compared to sound cats and a different behaviour according to owner subjective assessment. It is of great importance that further studies are performed to investigate the long term effects of CCL injury as a cause of pain and physical dysfunction, and its role in the development of OA in cats. Improved assessment tools for chronic pain caused by OA in cats are needed, both to facilitate diagnosis and to evaluate pain-relieving treatment.

Tibial plateau levelling osteotomy in eleven cats with cranial cruciate ligament rupture

OBJECTIVE

To report the surgical procedure, intra- and postoperative complications, and short-term follow-up of tibial plateau levelling osteotomy (TPLO) in feline patients with cranial cruciate ligament (CrCL) rupture using a 2.0 or 2.4 mm Synthes^® TPLO plate.

STUDY DESIGN

Prospective study.

MATERIAL AND METHODS

Eleven cats with a CrCL rupture were included in the study. Inspection of intra-articular structures was carried out via arthroscopy or arthrotomy. Each patient was re-examined one and 10 days after surgery. Orthopaedic examination and follow-up radiographs were obtained four to 12 weeks postoperatively.

RESULTS

Two meniscopathies and one partial CrCL rupture were detected. Minor intra-operative complications occurred in five cats (suboptimal positioning of the plate [n = 3], proximal fibular fracture [n = 1], a visible osteotomy gap [n = 1]). Postoperatively, minor complications were detected in three cats (mild patellar desmitis [n = 2], superficial wound infection [n = 1]). No additional surgical reintervention, graded as major complication, was necessary. Four to eight weeks postoperatively, all cats showed no to mild intermittent lameness. Complete bone union was apparent within four to 12 weeks. Owners reported a high level of comfort and mobility during the last follow-up.

CONCLUSION

The preliminary results of this study support the use of TPLO in cats, but larger case numbers are needed to evaluate its practicability, as well as long-term outcome (>1 year), especially evaluating the development and the clinical relevance of osteoarthritis.

Contribution of mechanical unloading to trabecular bone loss following non-invasive knee injury in mice

Development of osteoarthritis commonly involves degeneration of epiphyseal trabecular bone. In previous studies, we observed 30-44% loss of epiphyseal trabecular bone (BV/TV) from the distal femur within 1 week following non-invasive knee injury in mice. Mechanical unloading (disuse) may contribute to this bone loss; however, it is unclear to what extent the injured limb is unloaded following injury, and whether disuse can fully account for the observed magnitude of bone loss. In this study, we investigated the contribution of mechanical unloading to trabecular bone changes observed following non-invasive knee injury in mice (female C57BL/6N). We investigated changes in gait during treadmill walking, and changes in voluntary activity level using Open Field analysis at 4, 14, 28, and 42 days post-injury. We also quantified epiphyseal trabecular bone using μCT and weighed lower-limb muscles to quantify atrophy following knee injury in both ground control and hindlimb unloaded (HLU) mice. Gait analysis revealed a slightly altered stride pattern in the injured limb, with a decreased stance phase and increased swing phase. However, Open Field analysis revealed no differences in voluntary movement between injured and sham mice at any time point. Both knee injury and HLU resulted in comparable magnitudes of trabecular bone loss; however, HLU resulted in considerably more muscle loss than knee injury, suggesting another mechanism contributing to bone loss following injury. Altogether, these data suggest that mechanical unloading likely contributes to trabecular bone loss following non-invasive knee injury, but the magnitude of this bone loss cannot be fully explained by disuse. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1680-1687, 2016.

Assessment of cortical and trabecular bone changes in two models of post-traumatic osteoarthritis

Subchondral bone is thought to play a significant role in the initiation and progression of the post-traumatic osteoarthritis. The goal of this study was to document changes in tibial and femoral subchondral bone that occur as a result of two lapine models of anterior cruciate ligament injury, a modified ACL transection model and a closed-joint traumatic compressive impact model. Twelve weeks post-injury bones were scanned via micro-computed tomography. The subchondral bone of injured limbs from both models showed decreases in bone volume and bone mineral density. Surgical transection animals showed significant bone changes primarily in the medial hemijoint of femurs and tibias, while significant changes were noted in both the medial and lateral hemijoints of both bones for traumatic impact animals. It is believed that subchondral bone changes in the medial hemijoint were likely caused by compromised soft tissue structures seen in both models. Subchondral bone changes in the lateral hemijoint of traumatic impact animals are thought to be due to transmission of the compressive impact force through the joint. The joint-wide bone changes shown in the traumatic impact model were similar to clinical findings from studies investigating the progression of osteoarthritis in humans.

Non-invasive mouse models of post-traumatic osteoarthritis

Animal models of osteoarthritis (OA) are essential tools for investigating the development of the disease on a more rapid timeline than human OA. Mice are particularly useful due to the plethora of genetically modified or inbred mouse strains available. The majority of available mouse models of OA use a joint injury or other acute insult to initiate joint degeneration, representing post-traumatic osteoarthritis (PTOA). However, no consensus exists on which injury methods are most translatable to human OA. Currently, surgical injury methods are most commonly used for studies of OA in mice; however, these methods may have confounding effects due to the surgical/invasive injury procedure itself, rather than the targeted joint injury. Non-invasive injury methods avoid this complication by mechanically inducing a joint injury externally, without breaking the skin or disrupting the joint. In this regard, non-invasive injury models may be crucial for investigating early adaptive processes initiated at the time of injury, and may be more representative of human OA in which injury is induced mechanically. A small number of non-invasive mouse models of PTOA have been described within the last few years, including intra-articular fracture of tibial subchondral bone, cyclic tibial compression loading of articular cartilage, and anterior cruciate ligament (ACL) rupture via tibial compression overload. This review describes the methods used to induce joint injury in each of these non-invasive models, and presents the findings of studies utilizing these models. Altogether, these non-invasive mouse models represent a unique and important spectrum of animal models for studying different aspects of PTOA.

Alterations in subchondral bone plate, trabecular bone and articular cartilage properties of rabbit femoral condyles at 4 weeks after anterior cruciate ligament transection

OBJECTIVE

To quantify early osteoarthritic-like changes in the structure and volume of subchondral bone plate and trabecular bone and properties of articular cartilage in a rabbit model of osteoarthritis (OA) induced by anterior cruciate ligament transection (ACLT).

METHODS

Left knee joints from eight skeletally mature New Zealand white rabbits underwent ACLT surgery, while the contralateral (CTRL) right knee joints were left unoperated. Femoral condyles were harvested 4 weeks after ACLT. Micro-computed tomography imaging was applied to evaluate the structural properties of subchondral bone plate and trabecular bone. Additionally, biomechanical properties, structure and composition of articular cartilage were assessed.

RESULTS

As a result of ACLT, significant thinning of the subchondral bone plate (P < 0.05) was accompanied by significantly reduced trabecular bone volume fraction and trabecular thickness in the medial femoral condyle compartment (P < 0.05), while no changes were observed in the lateral compartment. In both lateral and medial femoral condyles, the equilibrium modulus and superficial zone proteoglycan (PG) content were significantly lower in ACLT than CTRL joint cartilage (P < 0.05). Significant alterations in the collagen orientation angle extended substantially deeper into cartilage from the ACLT joints in the lateral femoral condyle relative to the medial condyle compartment (P < 0.05).

CONCLUSIONS

In this model of early OA, significant changes in volume and microstructure of subchondral bone plate and trabecular bone were detected only in the femoral medial condyle, while alterations in articular cartilage properties were more severe in the lateral compartment. The former finding may be associated with reduced joint loading in the medial compartment due to ACLT, while the latter finding reflects early osteoarthritic changes in the lateral compartment.

Effect of alendronate on post-traumatic osteoarthritis induced by anterior cruciate ligament rupture in mice

Introduction

Previous studies in animal models of osteoarthritis suggest that alendronate (ALN) has antiresorptive and chondroprotective effects, and can reduce osteophyte formation. However, these studies used non-physiologic injury methods, and did not investigate early time points during which bone is rapidly remodeled prior to cartilage degeneration. The current study utilized a non-invasive model of knee injury in mice to investigate the effect of ALN treatment on subchondral bone changes, articular cartilage degeneration, and osteophyte formation following injury.

Methods

Non-invasive knee injury via tibial compression overload or sham injury was performed on a total of 90 mice. Mice were treated with twice weekly subcutaneous injections of low-dose ALN (40 μg/kg/dose), high-dose ALN (1,000 μg/kg/dose), or vehicle, starting immediately after injury until sacrifice at 7, 14 or 56 days. Trabecular bone of the femoral epiphysis, subchondral cortical bone, and osteophyte volume were quantified using micro-computed tomography (μCT). Whole-joint histology was performed at all time points to analyze articular cartilage and joint degeneration. Blood was collected at sacrifice, and serum was analyzed for biomarkers of bone formation and resorption.

Results

μCT analysis revealed significant loss of trabecular bone from the femoral epiphysis 7 and 14 days post-injury, which was effectively prevented by high-dose ALN treatment. High-dose ALN treatment was also able to reduce subchondral bone thickening 56 days post-injury, and was able to partially preserve articular cartilage 14 days post-injury. However, ALN treatment was not able to reduce osteophyte formation at 56 days post-injury, nor was it able to prevent articular cartilage and joint degeneration at this time point. Analysis of serum biomarkers revealed an increase in bone resorption at 7 and 14 days post-injury, with no change in bone formation at any time points.

Conclusions

High-dose ALN treatment was able to prevent early trabecular bone loss and cartilage degeneration following non-invasive knee injury, but was not able to mitigate long-term joint degeneration. These data contribute to understanding the effect of bisphosphonates on the development of osteoarthritis, and may support the use of anti-resorptive drugs to prevent joint degeneration following injury, although further investigation is warranted.

The 2014 ABJS Nicolas Andry Award: The puzzle of the thumb: mobility, stability, and demands in opposition

BACKGROUND

The paradoxical demands of stability and mobility reflect the purpose and function of the human thumb. Its functional importance is underscored when a thumb is congenitally absent, injured, or afflicted with degenerative arthritis. Prevailing literature and teaching implicate the unique shape of the thumb carpometacarpal (CMC) joint, as well as its ligament support, applied forces, and repetitive motion, as culprits causing osteoarthritis (OA). Sex, ethnicity, and occupation may predispose individuals to OA.

QUESTIONS/PURPOSES

What evidence links ligament structure, forces, and motion to progressive CMC disease? Specifically: (1) Do unique attributes of the bony and ligamentous anatomy contribute to OA? (2) Can discrete joint load patterns be established that contribute to OA? And (3) can thumb motion that characterizes OA be measured at the fine and gross level?

METHODS

We addressed the morphology, load, and movement of the human thumb, emphasizing the CMC joint in normal and arthritic states. We present comparative anatomy, gross dissections, microscopic analysis, multimodal imaging, and live-subject kinematic studies to support or challenge the current understanding of the thumb CMC joint and its predisposition to disease.

RESULTS

The current evidence suggests structural differences and loading characteristics predispose the thumb CMC to joint degeneration, especially related to volar or central wear. The patterns of degeneration, however, are not consistently identified, suggesting influences beyond inherent anatomy, repetitive load, and abnormal motion.

CONCLUSIONS

Additional studies to define patterns of normal use and wear will provide data to better characterize CMC OA and opportunities for tailored treatment, including prevention, delay of progression, and joint arthroplasty.

Subchondral bone in osteoarthritis: insight into risk factors and microstructural changes

Osteoarthritis (OA) is a major cause of disability in the adult population. As a progressive degenerative joint disorder, OA is characterized by cartilage damage, changes in the subchondral bone, osteophyte formation, muscle weakness, and inflammation of the synovium tissue and tendon. Although OA has long been viewed as a primary disorder of articular cartilage, subchondral bone is attracting increasing attention. It is commonly reported to play a vital role in the pathogenesis of OA. Subchondral bone sclerosis, together with progressive cartilage degradation, is widely considered as a hallmark of OA. Despite the increase in bone volume fraction, subchondral bone is hypomineralized, due to abnormal bone remodeling. Some histopathological changes in the subchondral bone have also been detected, including microdamage, bone marrow edema-like lesions and bone cysts. This review summarizes basic features of the osteochondral junction, which comprises subchondral bone and articular cartilage. Importantly, we discuss risk factors influencing subchondral bone integrity. We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA. A hypothetical model for the pathogenesis of OA is proposed.

Inhibited osteoclastic bone resorption through alendronate treatment in rats reduces severe osteoarthritis progression

Osteoarthritis (OA) is a non-rheumatoid joint disease characterized by progressive degeneration of extra-cellular cartilage matrix (ECM), enhanced subchondral bone remodeling, osteophyte formation and synovial thickening. Alendronate (ALN) is a potent inhibitor of osteoclastic bone resorption and results in reduced bone remodeling. This study investigated the effects of pre-emptive use of ALN on OA related osteoclastic subchondral bone resorption in an in vivo rat model for severe OA. Using multi-modality imaging we measured effects of ALN treatment within cartilage and synovium. Severe osteoarthritis was induced in left rat knees using papain injections in combination with a moderate running protocol. Twenty rats were treated with subcutaneous ALN injections and compared to twenty untreated controls. Animals were longitudinally monitored for 12weeks with in vivo μCT to measure subchondral bone changes and SPECT/CT to determine synovial macrophage activation using a folate-based radiotracer. Articular cartilage was analyzed at 6 and 12weeks with ex vivo contrast enhanced μCT and histology to measure sulfated-glycosaminoglycan (sGAG) content and cartilage thickness. ALN treatment successfully inhibited subchondral bone remodeling. As a result we found less subchondral plate porosity and reduced osteophytosis. ALN treatment did not reduce subchondral sclerosis. However, after the OA induction phase, ALN treatment protected cartilage ECM from degradation and reduced synovial macrophage activation. Surprisingly, ALN treatment also improved sGAG content of tibia cartilage in healthy joints. Our data was consistent with the hypothesis that osteoclastic bone resorption might play an important role in OA and may be a driving force for progression of the disease. However, our study suggest that this effect might not solely be effects on osteoclastic activity, since ALN treatment also influenced macrophage functioning. Additionally, ALN treatment and physical activity exercised a positive effect in healthy control joints, which increased cartilage sGAG content. More research on this topic might lead to novel insights as to improve cartilage quality.

Advances and challenges in gene-based approaches for osteoarthritis

Osteoarthritis (OA), a paramount cause of physical disability for which there is no definitive cure, is mainly characterized by the gradual loss of the articular cartilage. Current nonsurgical and reconstructive surgical therapies have not met success in reversing the OA phenotype so far. Gene transfer approaches allow for a long-term and site-specific presence of a therapeutic agent to re-equilibrate the metabolic balance in OA cartilage and may consequently be suited to treat this slow and irreversible disorder. The distinct stages of OA need to be respected in individual gene therapy strategies. In this context, molecular therapy appears to be most effective for early OA. A critical step forward has been made by directly transferring candidate sequences into human articular chondrocytes embedded within their native extracellular matrix via recombinant adeno-associated viral vectors. Although extensive studies in vitro attest to a growing interest in this approach, data from animal models of OA are sparse. A phase I dose-escalating trial was recently performed in patients with advanced knee OA to examine the safety and activity of chondrocytes modified to produce the transforming growth factor β1 via intra-articular injection, showing a dose-dependent trend toward efficacy. Proof-of-concept studies in patients prior to undergoing total knee replacement may be privileged in the future to identify the best mode of translating this approach to clinical application, followed by randomized controlled trials.

Does moderate or severe nonspecific knee injury affect radiographic osteoarthritis incidence and progression?

Background

Knee injuries can lead to radiographic osteoarthritis (ROA). Injuries may be “specific” (SI) including ligament or meniscal tears or patellar trauma, or “nonspecific” (NSI). Our objective is to understand the effect of knee NSI on ROA incidence and progression.

Methods

163 people (sample-weighted for population representativeness) aged 40+ with history of knee pain had radiographs assessed on Kellgren Lawrence (KL) grade (0/1 collapsed) at baseline and follow-up (median 3.2 years apart). Progression was an increase in KL score. SIs and NSIs were labeled “severe” (walking aid for ≥1 week) or “moderate”. One model treated SI and NSI as dichotomous (yes/no), and another as trichotomous (none/moderate/severe). Models were adjusted for age, sex, BMI, KL grade and follow-up time.

Results

SI/NSI history was none, moderate (7.8/24.4%) or severe (11.0/10.8%). Duration at baseline since SI/NSI ranged from <1 year to several decades (SI/NSI mean 4.6/6.5 years). SI was significantly associated with ROA incidence and progression (odds ratio (OR) = 2.90; 95% CI = 1.04, 8.09), but NSI showed no significant effect (OR = 1.36; 95% CI = 0.61, 3.02). In the trichotomous model, severe SI was significant (OR = 4.35, 95% CI = 1.26, 15.02), while moderate SI was not (OR = 1.51, 95% CI = 0.33, 6.84). NSI showed no effect: moderate OR = 1.51, 95% CI = 0.61, 3.74; severe OR = 0.90, 95% CI = 0.24, 3.40. This study had 80% power to detect an NSI OR of 2.9.

Conclusion

We find no evidence that history of NSI affects knee ROA incidence and progression in a population with knee pain, adjusting for SI, age, sex, BMI, KL grade and follow-up time.

A modified Maquet technique for management of cranial cruciate avulsion in a cat

This case report describes the management of cranial cruciate ligament avulsion from the femur of a four-year-old Norwegian Forest cat that presented with a history of lameness which had not improved with conservative treatment. During medial arthrotomy, avulsion of the cranial cruciate ligament from the caudomedial aspect of the lateral femoral condyle was suspected and the torn portion resected. A modified Maquet technique was performed on the left tibia resulting in a rapid improvement in lameness postoperatively. Histopathology of the resected cranial cruciate ligament confirmed avulsion. To the authors' knowledge this is the first reported use of this technique in the cat, and the first of stifle instability due to cranial cruciate ligament avulsion from the femur in the cat.

Trapezium trabecular morphology in carpometacarpal arthritis

PURPOSE

In thumb carpometacarpal osteoarthritis, current evidence suggests that degenerative, bony remodeling primarily occurs within the trapezium. Nevertheless, the pathomechanics involved and the most common sites of wear remain controversial. Quantifying structural bone morphology characteristics with high-resolution computed tomography CT (micro-CT) infer regions of load transmission. Using micro-CT, we investigated whether predominant trabecular patterns exist in arthritic versus normal trapeziums.

METHODS

We performed micro-CT analysis on 13 normal cadaveric trapeziums and 16 Eaton stage III to IV trapeziums. We computationally divided each specimen into 4 quadrants: volar-ulnar, volar-radial, dorsal-radial, and dorsal-ulnar. Measurements of trabecular bone morphologic parameters included bone volume ratio, connectivity, trabecular number, and trabecular thickness. Using analysis of variance with post hoc Bonferroni/Dunn correction, we compared osteoarthritic and normal specimen quadrant measurements.

RESULTS

No significant difference existed in bone volume fraction between the osteoarthritic and normal specimens. Osteoarthritic trapeziums, however, demonstrated significantly higher trabecular number and connectivity than nonosteoarthritic trapeziums. Comparing the volar-ulnar quadrant of osteoarthritis and normal specimens collectively, this quadrant in both consistently possessed significantly higher bone volume fraction, trabecular number, and connectivity than the dorsal-radial and volar-radial quadrants.

CONCLUSIONS

The significantly greater trabecular bone volume, thickness, and connectivity in the volar-ulnar quadrant compared with the dorsal-radial and dorsal-ulnar quadrants provides evidence that the greatest compressive loads at the first carpometacarpal joint occur at the volar-ulnar quadrant of the trapezium, representing a consistently affected region of wear in both normal and arthritic states.

CLINICAL RELEVANCE

These findings suggest that trapezial trabecular morphology undergoes pathologic alteration. This provides indirect evidence that changes in load transmission occur with thumb carpometacarpal joint arthritis development.

Growth-related structural, biochemical, and mechanical properties of the functional bone-cartilage unit

Articular cartilage and subchondral bone act together, forming a unit as a weight-bearing loading-transmitting surface. A close interaction between both structures has been implicated during joint cartilage degeneration, but their coupling during normal growth and development is insufficiently understood. The purpose of the present study was to examine growth-related changes of cartilage mechanical properties and to relate these changes to alterations in cartilage biochemical composition and subchondral bone structure. Tibiae and femora of both hindlimbs from 7- and 13-week-old (each n = 12) female Sprague-Dawley rats were harvested. Samples were processed for structural, biochemical and mechanical analyses. Immunohistochemical staining and protein expression analyses of collagen II, collagen IX, COMP and matrilin-3, histomorphometry of cartilage thickness and COMP staining height were performed. Furthermore, mechanical testing of articular cartilage and micro-CT analysis of subchondral bone was conducted. Growth decreased cartilage thickness, paralleled by a functional condensation of the underlying subchondral bone due to enchondral ossification. Cartilage mechanical properties seem to be rather influenced by growth-related changes in the assembly of major ECM proteins such as collagen II, collagen IX and matrilin-3 than by growth-related alterations in its underlying subchondral bone structure. Importantly, the present study provides a first insight into the growth-related structural, biochemical and mechanical interaction of articular cartilage and subchondral bone. Finally, these data contribute to the general knowledge about the cooperation between the articular cartilage and subchondral bone.

Pathophysiology of peri-articular bone changes in osteoarthritis

Osteoarthritis (OA) is a disease that involves the entire joint, but its pathophysiology is not well described. Alterations in peri-articular bone are an integral part of the OA disease process and different aspects of bone changes have been described in different patient (sub)groups and animal models. In this review we will discuss the osteoarthritis pathophysiology from the perspective of periarticular bone changes, which can be considered at three hierarchical levels: the bone (or joint) shape, the subchondral bone architecture and its cellular and molecular phenotype. In this review we try to provide an overview of the current knowledge of peri-articular bone changes in OA and what it could possibly imply for the initiation of OA and its progression. This article is part of a Special Issue entitled "Osteoarthritis".

The effect of level and downhill running on cortical and trabecular bone in growing rats

Mechanical loading is essential for bone development and prevention of age-related bone diseases. Muscular contractions during physical activity and the generated strain magnitude are primary determinants for the osteogenic response. However, the adaptation capacity of bones, especially due to different muscle contraction types, is largely unknown. In the present study we examined the effect of different running modes characterized by different muscle contraction types and loading patterns on the morphological, structural, and mechanical properties of different sites in the femur of growing rats. Thirty-six female Sprague-Dawley rats were randomly assigned to a nonactive age-matched control (AMC), a level running (LEVEL), and a 20° decline downhill running (DOWN) group (n = 12 each). Running groups were trained on a treadmill for 30 min/day, 5 days/week for 6 weeks. After death, pQCT analysis of the meta- and diaphyses, micro-CT analysis of the epiphysis, and mechanical testing of the femur were performed. The Tb.BMD in the metaphysis was significantly (P < 0.05) increased in the DOWN compared to the AMC group, whereas level running had no effect on Tb.BMD. While Young's modulus was significantly different (P < 0.05) between the DOWN and LEVEL groups, no structural alterations were found in the diaphysis between the groups. Further, subchondral trabecular bone did not show exercise-induced changes caused by the different running modes but displayed a remarkably high intraepiphyseal variability. Downhill running seems to be a potent osteogenic stimulus in the femoral metaphysis.

Translational animal models using veterinary patients - An example of canine osteoarthritis (OA)

Background and purpose The use of laboratory animals in pain research has powerfully contributed to our detailed understanding of the physiological mechanisms of pain. Animal models also represent an essential tool to screen and select novel drug molecules with potentially analgesic properties. Despite of the inevitable input of laboratory animal trials, recent studies have shown that animal pain models have repeatedly failed to predict clinical analgesic efficacy and adverse side effects of potential drug molecules in human pain patients. This paper provides a review of the laboratory animal models of OA, which have been developed to test efficacy of novel analgesics. The paper also presents spontaneous OA in canine veterinary patients, and methods to observe chronic pain in nonverbal dogs. Methods PubMed data base was searched as a reference list to locate most relevant articles. A number of 118 articles including 4 reviews were located. Web pages of 4 establishments and 2 private organizations were also accessed. Results The clinical expression and pathogenesis of naturally occurring OA in dogs is considered an analogous disease that occurs in humans, including pain and lameness. OA may occur in any joint in dogs as well as in humans. Primary idiopathic OA in dogs is rare, but certain breeds may be predisposed to it. For the most part, canine OA is considered secondary to acquired or congenital musculoskeletal disorders. Concomitant factors, such as aging and obesity, likely accelerate progression. However, mechanical factors appear to predominate in the etiopathogenesis of canine spontaneous OA. Both subjective (validated questionnaire) and objective (gait analysis) tools are available to measure OA related pain in dogs. Information on the prevalence of canine OA is limited, but rough surveys suggest that 11 million dogs in the United States and 5 million in Europe could suffer from OA. Ethical considerations concerning the use of privately owned dogs can be resolved by a careful experimental design. Conclusion Canine spontaneous OA could serve as a translational animal model that would more closely mimick clinical OA related pain conditions in humans. Privately owned dogs would make a solution to fix the gap between animal pain models and clinical trials when testing potential analgesic drug molecules. Close interdisciplinary cooperation would guarantee that both scientific and ethical intentions would be achieved. Implications The predictability of translational pain research would improve by using privately owned dogs as chronic pain models when testing novel analgesics.

Dose range finding study for the efficacy of meloxicam administered prior to sodium urate-induced synovitis in cats

OBJECTIVE

To determine the lowest efficacious dose of oral meloxicam for relieving pain in cats with a sodium urate (SU)-induced acute inflammatory synovitis.

STUDY DESIGN

Randomized, blinded, controlled, and four-way crossover study.

ANIMALS

Eight surgically neutered cats (four males, four females) paired according to sex.

METHODS

Each pair of cats was treated with 0 (placebo), 0.025, 0.05, or 0.075 mg kg(-1) oral meloxicam once daily for 4 days prior to injection, into alternating stifles, of 1 mL of 20 mg mL(-1) SU crystals, beginning with the right stifle. Each cat received each of the four treatments, separated by at least 21 days. Analgesic efficacy was evaluated based on objective (e.g., pressure mat data total force, contact pressure, and contact area) and subjective (e.g., scores for Analgesia Scale [AS], Lameness Scale [LS], and Visual Analog Scale [VAS]) outcome measures for pain assessment. All outcome measures were recorded before and during 30 hours after SU injection. The pre-defined primary outcome measure was the area under the response-time curve (AUC(0-30) hours) of the total force of the injected limb. Data were analyzed by analysis of variance. A sequential test procedure was applied and the test sequence stopped in case of a nonsignificant result.

RESULTS

Meloxicam at doses of 0.05 and 0.075 mg kg(-1) day(-1) PO was significantly different from placebo for the pre-defined primary outcome measure (i.e., AUC(0-30) hours of total force). All tested meloxicam doses were lower than placebo for the subjective outcome measures (i.e., AUC(0-30) hours of AS, LS, and VAS).

CONCLUSIONS AND CLINICAL RELEVANCE

The lowest efficacious dose of meloxicam for relieving pain in cats with an SU-induced synovitis was 0.05 mg kg(-1) day(-1) PO according to the pre-defined primary outcome measure. However, lower doses may also be effective as seen in the subjective outcome measures.

Subchondral bone changes in three different canine models of osteoarthritis

OBJECTIVE

To test the hypothesis that changes in subchondral bone are significantly different among three canine models of osteoarthritis (OA).

DESIGN

In 21 purpose-bred mongrel dogs, OA was induced in one knee joint via either anterior cruciate ligament transection (ACLt; n = 5), medial femoral condylar groove creation (GR; n = 6), or medial meniscal release (MR; n = 5). Five dogs that had sham surgery (SH; n = 5) in one knee joint served as controls. Lameness scoring was performed every 4 weeks. Twelve weeks after surgery, the knee joints were examined by histology and histomorphometry.

RESULTS

Articular cartilage pathology as determined by Mankin scores was significantly severe in all three OA models compared to SH controls in the medial tibia (P < 0.001 to P = 0.026). ACLt had significantly thinner subchondral plate thickness (Sp.Th) in both the medial and lateral tibias while MR had significantly thicker Sp.Th in the medial tibia compared to SH controls (P < 0.001 to P = 0.011). Trabecular bone volume (BV/TV) and trabecular bone thickness (Tb.Th) for ACLt were significantly less than SH controls in the tibias (P < 0.001 to P = 0.011). Tibial Sp.Th, BV/TV, and Tb.Th were all moderately to strongly correlated with lameness scores obtained throughout the study period (r = -0.436 to r = -0.738, P < 0.001 to P = 0.047) while Mankin scores showed moderate to strong correlations with Sp.Th in each OA model (r = 0.465 to r = 0.816, P < 0.001 to P = 0.033).

CONCLUSIONS

Changes in Sp.Th are associated with articular cartilage damage while tibial Sp.Th and BV/TV and Tb.Th appear to be all influenced by joint loading alterations.

Inhibition of osteoclasts prevents cartilage loss and pain in a rat model of degenerative joint disease

OBJECTIVE

To investigate the relationship between efficacy of a bisphosphonate, pain and extent of joint damage in the monosodium iodoacetate (MIA) model of painful degenerative joint disease.

METHODS

Zoledronate treatment was initiated prior to and at various times following model induction, including late time points representing advanced disease. Radiographic and histological structural parameters were correlated with pain as measured by weight bearing.

RESULTS

Intraarticular (IA) MIA resulted in a progressive loss of bone mineral density (BMD) and chondrocytes, thinning of cartilage, loss of proteoglycan, resorption of calcified cartilage and subchondral bone, as well as pain. This was completely prevented by pre-emptive chronic zoledronate treatment with joint sections being histologically indistinguishable from saline-injected controls. When initiation of treatment was delayed efficacy was reduced. In animals with advanced joint degeneration, treatment partially restored BMD and had a significant, but limited, effect on pain. We confirmed these radiographic and behavioral findings in the medial meniscal tear model. To understand the mechanism-of-action of zoledronate we investigated an early time point 4 days post-model induction when chondrocytes were histologically viable, with minor loss of proteoglycan and generalized synovitis. Osteoclast-mediated resorption of the calcified cartilage was observed and was prevented by two doses of zoledronate.

CONCLUSION

Subchondral bone remodeling plays an important role in nociception and the pathobiology of the MIA model with osteoclasts being implicated in both bone and cartilage resorption. Inhibition of osteoclastic activity when initiated early leads to improved efficacy.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the dog

The dog is a common model for study of osteoarthritis (OA). Subjective histologic scoring systems have often served as the reference standard for presence and severity of OA. However, these scoring systems have perceived shortcomings. The system developed for this report attempts to address these shortcomings by providing a standardized methodology for global assessment of the joint, versatility and the potential for relative weighting of pathology, allowing for comparison among time points, studies, and centers, and critical analysis of the system's reliability. The proposed system for assessment of canine tissues appears to provide an effective method for global assessment of articular pathology in OA. The system is versatile, comprehensive, and reliable and appears to have advantages over conventional scoring systems.

Development of an in vitro model of feline cartilage degradation

Osteoarthritis is the most common arthropathy of mammalian species including cats. Cartilage degradation is central to the disorder and here we present, for the first time, an in vitro model of feline cartilage degradation which will be useful for further studies in this target species. Feline articular cartilage explant cultures were maintained for 28 days and in the presence of oncostatin M with and without interleukin (IL)-17, tumour necrosis factor (TNF), IL-1alpha, or IL-1beta. Media samples and digested cartilage explants were analysed for glycosaminoglycan (GAG) and collagen content. The combination of IL-1beta and OSM, both at 20 ng/ml, was able to promote GAG release to the greatest extent at 14 days. At 28 days, all groups showed relatively high release of GAG. At 14 days, only IL-1beta and OSM in combination were associated with a statistically significant increase in collagen release over and above control tissue. IL-1beta dose-response studies showed that an IL-1beta dose of 10 ng/ml promotes a statistically significant increase in GAG breakdown when used with OSM, and higher doses of IL-1beta did not result in significantly greater response. The model demonstrated both GAG and collagen degradation and will be of use for further understanding of feline cartilage metabolism and for screening of potential structure-modifying agents to be used in cats.

Comparison of differential biomarkers of osteoarthritis with and without posttraumatic injury in the Hartley guinea pig model

The objective was to compare biomarkers of articular cartilage metabolism in synovial fluid from Hartley guinea pig knees, with and without anterior cruciate ligament transection (ACLT), to establish whether detectable differences in biomarker levels exist between primary and secondary osteoarthritis (OA). Synovial fluid lavages and knees were obtained from 3-month (control group) and 12-month (primary OA group) animals. Another group of animals (posttraumatic OA group) underwent unilateral ACLT at 3 months, and samples were obtained 9 months postsurgery. Synovial fluid concentrations of stromal cell-derived-factor (SDF-1), collagen fragments (C2C), proteoglycan (GAG), lubricin, matrix metalloproteinase-13 (MMP-13), and Interleukin-1 (IL-1beta) were evaluated. Cartilage damage was assessed via histology. The highest concentrations of C2C and SDF-1 in synovial fluid were found in the posttraumatic OA group, moderate concentrations were found in the primary OA group, and low concentrations in the control group. GAG release in synovial fluid was similar to C2C and SDF-1. The lubricin concentrations were significantly lower in ACLT joints than either the control or 12-month primary OA groups, but not between the control and primary OA groups. Higher levels of MMP-13 and IL-1beta were detected in the joints of the posttraumatic OA group as compared to the control or primary OA groups. Histology revealed greatest OA damage in the posttraumatic OA group, followed by moderate and minimal damage in primary OA and control groups, respectively. This study indicates that the biomarkers and progression of OA may differ in the Hartley guinea pig models with and without posttraumatic OA.

Similarities and discrepancies in subchondral bone structure in two differently induced canine models of osteoarthritis

In osteoarthritis (OA), cartilage degradation is accompanied by subchondral bone changes. The pathogenesis and physiology of bone changes in OA are still unclear. The changes in subchondral bone architecture and cartilage damage were compared in differently induced experimental models of OA. Experimental OA was induced bilaterally by anterior cruciate ligament transection (ACLT) or by cartilage trauma (Groove model); bilateral sham surgery served as control. Lysylpyridinoline (LP, bone resorption) and C-telopeptide of type II collagen (CTX-II, cartilage breakdown) were measured over time. At 20 weeks after surgery, the subchondral cortical plate and trabecular bone of the tibia were analyzed by micro-computed tomography (microCT) and cartilage degeneration was analyzed histologically and biochemically. In both models, cartilage degeneration and cortical subchondral plate thinning were present. CTX-II levels were elevated over time in both models. Subchondral trabecular bone changes were observed only in the ACLT model, not in the Groove model. Correspondingly, LP levels were elevated over time in the ACLT model and not in the Groove model. Interestingly, the trabecular bone changes in the ACLT model were extended to the metaphyseal area. The early decrease in plate thickness, present in both models, as was cartilage damage, suggests that plate thinning is a phenomenon that is intrinsic to the process of OA independent of the cause/induction of OA. On the other hand, trabecular changes in subchondral and metaphyseal bone are not part of a common pathway of OA development and may be induced biomechanically in the destabilized and less loaded ACLT joint.

In early OA, thinning of the subchondral plate is directly related to cartilage damage: results from a canine ACLT-meniscectomy model

OBJECTIVE

The pathogenesis of osteoarthritis (OA) includes cartilage degeneration, synovial inflammation, and bone changes. Slowly, the sequence and inter-relationship of these features is becoming clearer. Early models of OA suggest thinning of the subchondral plate in addition to trabecular bone changes. In the present study subchondral bone changes were studied in the canine anterior cruciate ligament transection (ACLT)-meniscectomy model. This model is characterized by intra-joint variability with respect to cartilage damage (predominantly medial) and loading (lateral unloading due to a shifted axis).

METHODS

In 13 Labrador dogs, OA was induced by transection of the anterior cruciate ligament and removal of the medial meniscus. Twelve weeks later, cartilage integrity was evaluated histologically using the modified Mankin score (0-11), and proteoglycan content was determined by Alcian Blue assay. Bone architecture of the tibia was quantified by micro-CT.

RESULTS

Cartilage damage was severe in the medial compartment (Mankin score +3.5, glycosaminoglycan (GAG) content -28%) and mild in the lateral compartment (Mankin score +1.6, GAG content -15%). Thinning and porosity of the subchondral plate were only present on the medial side (-21%, +87%, respectively). Interestingly, changes in trabecular bone structure did almost not occur in the medial compartment (volume fraction -7%) but were clear in the lateral compartment (-20%).

CONCLUSION

Thinning of the subchondral plate is a localized phenomenon related to cartilage degeneration while trabecular bone changes are related to mechanical (un)loading. The different mechanisms responsible for bone changes in OA should be taken in account when designing and interpreting studies interfering with bone turnover in the treatment of OA.

A pilot study: sodium urate synovitis as an acute model of inflammatory response using objective and subjective criteria to evaluate arthritic pain in cats

Sodium urate (SU) synovitis was evaluated as a model for feline arthritic pain using a placebo- and positive-controlled (meloxicam) randomized blinded controlled single crossover design. Monosodium urate crystals [20 mg (1 mL) rod-shaped] were injected into alternate stifles of trained anesthetized cats (n = 3) with a 28 day washout. During the first trial phase, two cats received meloxicam (0.1 mg/kg, PO), a nonsteroidal anti-inflammatory drug (NSAID), for three days before and on the day of SU injection; the third cat received placebo. Treatments and stifles were switched for the second trial. Total force, contact pressure and area of the fore and hind limbs were measured using a pressure mat one day and 0.5 h before, and 2, 4, 6, 8, 10, 24, and 30 h post-SU injection. Skin temperature, joint circumference, analgesia, lameness, and visual analogue scale (VAS) pain scores, were measured at the same times. Comparisons were made for each time and for areas under the curve (AUC) using original and change from baseline; P < 0.05 was significant. Significant differences in force mat data and subjective data were found for the hind limb data (total force and total contact pressure at 6, 10, and 30 h; analgesia and VAS for pain at 4 h; lameness at 10, 24, and 30 h) and for AUC(0)-->(24h) and AUC(0)-->(30 h) (total force, total contact pressure, and mean lameness score) and for differences from BL AUC(0)-->(10h) (total contact area) and AUC(0)-->(24h) (total contact area and mean lameness score) and AUC(0)-->(30 h) (total force, total contact area, and mean lameness). No cats required rescue analgesia. Injection of 1 mL of monosodium urate into the stifle of a cat causes moderate transitory pain and was suitable for assessing analgesic efficacy of an NSAID with a pressure mat and subjective criteria.

In vivo imaging of cartilage degeneration using microCT-arthrography

OBJECTIVE

In vivo imaging of cartilage degeneration in small animal models is nowadays practically impossible. In the present study, we investigated the use of micro-computed tomography (microCT) in combination with a negatively charged ionic iodine dimer (ioxaglate) for in vivo assessment of cartilage degeneration in a small animal model.

METHODS

Cartilage degeneration was induced in the right knee of rats by injection of mono-iodoacetate (MIA). We imaged the rat knees with ioxaglate enhanced microCT-arthrography at 4, 16 and 44 days after MIA injection. Subsequently, microCT-arthrographic findings were evaluated and compared with quantitative histology of the patellar cartilage.

RESULTS

In vivo microCT-arthrography clearly detected cartilage degeneration in the rat knee-joints, in which the ioxaglate diffused into the degenerated cartilage layer. Higher microCT-attenuation values and smaller total volumes of the cartilage layer were detected at longer time periods after MIA injection, which is quantitatively confirmed by histology.

CONCLUSION

In vivo microCT-arthrography is a valuable tool for detection of minor cartilage alterations and distinguishes different stages of cartilage degeneration in a small animal model. Since microCT, at the same time, also visualizes osteophyte formation and changes in the underlying subchondral bone structures, the technique will be very useful for longitudinal overall assessment of the development of (osteo)arthritis and to study interventions in small animal models.

Cartilage damage pattern in relation to subchondral plate thickness in a collagenase-induced model of osteoarthritis

OBJECTIVE

To see how initial differences in subchondral bone phenotype influence the development of cartilage damage and changes in subchondral bone architecture in an osteoarthritis (OA)-induced mouse model.

METHOD

Intra-articular collagenase injections (right knee joint) and saline controls (left knee joint) were applied in the knees of two mouse strains known to have either a low or a high bone mass phenotype: the low bone mass C57Bl/6 mice with a thin subchondral bone plate and high bone mass C3H/HeJ mice with a thick subchondral bone plate. The ages of the mice were 16 and 30 weeks, with n=8 per group. The collagenase injection induced an osteoarthritic phenotype that was evaluated 4 weeks later in the tibia using histological analyses and micro-computed tomography (micro-CT).

RESULTS

Both strains developed cartilage damage in the collagenase-injected right knee joints to a comparable extent, however, the spatial distribution of cartilage damage differed significantly: C57Bl/6 mice had most damage at the postero-lateral side, whereas in C3H/HeJ mice the postero-medial region was the most affected. Spontaneous cartilage damage was found in the saline-injected left control knees of C57Bl/6 mice, but in C3H/HeJ mice spontaneous cartilage damage was virtually absent. In both strains the subchondral bone plate of collagenase-injected joints became thinner, independent of the site of cartilage damage. TRAP-positive osteoclasts were observed underneath the subchondral bone plate, in line with the observed decreased thickness. No link was found between subchondral bone plate thickness and cartilage damage in the collagenase-injected joints. The subchondral trabecular architecture only changed in the high bone mass C3H/HeJ mice, with thinning of trabeculae and increased trabecular spacing.

CONCLUSION

Thinning of the subchondral bone plate was found as a common observation 4 weeks after OA had been induced in two strains of mice having either a high or low bone phenotype, but no relation was found with the amount of cartilage damage. In addition, this study shows that different strains of mice can react differently to instability-induced OA with respect to the spatial arrangement of cartilage damage and changes in subchondral trabecular structure.

A role for subchondral bone changes in the process of osteoarthritis; a micro-CT study of two canine models

BACKGROUND

This study evaluates changes in peri-articular bone in two canine models for osteoarthritis: the groove model and the anterior cruciate ligament transection (ACLT) model.

METHODS

Evaluation was performed at 10 and 20 weeks post-surgery and in addition a 3-weeks time point was studied for the groove model. Cartilage was analysed, and architecture of the subchondral plate and trabecular bone of epiphyses was quantified using micro-CT.

RESULTS

At 10 and 20 weeks cartilage histology and biochemistry demonstrated characteristic features of osteoarthritis in both models (very mild changes at 3 weeks). The groove model presented osteophytes only at 20 weeks, whereas the ACLT model showed osteophytes already at 10 weeks. Trabecular bone changes in the groove model were small and not consistent. This contrasts the ACLT model in which bone volume fraction was clearly reduced at 10 and 20 weeks (15-20%). However, changes in metaphyseal bone indicate unloading in the ACLT model, not in the groove model. For both models the subchondral plate thickness was strongly reduced (25-40%) and plate porosity was strongly increased (25-85%) at all time points studied.

CONCLUSION

These findings show differential regulation of subchondral trabecular bone in the groove and ACLT model, with mild changes in the groove model and more severe changes in the ACLT model. In the ACLT model, part of these changes may be explained by unloading of the treated leg. In contrast, subchondral plate thinning and increased porosity were very consistent in both models, independent of loading conditions, indicating that this thinning is an early response in the osteoarthritis process.

Microstructural adaptation in trapezial bone due to subluxation of the thumb

Although the thumb saddle is one of the most common sites of degenerative osteoarthritis in the hand, little is known about the altered microstructure in osteoarthritic trapezial bones. External forces resulting from subluxation of the carpometacarpal joint of the thumb (CMC I) should provoke microstructural changes in the trapezium. The purpose of this study was to compare the regional differences of the microstructure between osteoarthritic and healthy trapezial bones. Fifteen trapezia harvested from female patients with radiologically and clinically diagnosed saddle joint osteoarthritis (OA) were compared with 15 unaffected controls. Microstructural parameters, such as bone volume ratio (BV/TV), three-dimensional connectivity (Conn.D), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were studied using a microcomputed tomography (microCT) system. While the trapezial height in OA was 22% less, the sclerotic subchondral bone layer thickness was 50% higher in OA compared with the control group (p < 0.001). In the OA group there was a 42% higher bone volume ratio (p <or= 0.001), an 18% increase in Tb.Th (p = 0.006), and a 10% greater Tb.N (p = 0.034) compared with the control group. Although in both groups BV/TV was significantly lower in the radial region, the radial column showed the highest relative increase in bone volume and structure compared with the control group (+67% BV/TV, +20% Tb.Th, +23% Tb.N). The reinforcement of the bony microstructure in CMC I OA, especially at the radial side, is a sign for bone adaptation reacting to radially shifted joint forces. This has to be considered during the development of new prosthetic alternatives.