Videoradiographic analysis of the range of motion in unilateral experimental knee joint arthritis in rats

Pressure sensing mat as an objective and sensitive tool for the evaluation of lameness in rabbits

In orthopaedic research, the analysis of the gait pattern is an often-used evaluation method. It allows an assessment of changes in motion sequence and pain level during postoperative follow up periods. Visual assessments are highly subjective and dependent on the circumstances. Particular challenge in rabbits is their hopping gait pattern. The aim of the present study was to establish a more objective and sensitive lameness evaluation using a pressure sensing mat. Twelve NZW rabbits were implemented in the study. They got an artificial anterior cruciate ligament transection of the right knee in connection with an experimental study, which investigated PTOA treatment. Rabbits were examined by a visual lameness score. Additionally, load of the hindlimbs was measured by the use of a pressure sensing mat and a video was recorded. Peak pressure and time force integral, defined as cumulated integral of all sensors associated to a hind paw, were evaluated. Preoperative data were collected on three independent days. As postoperative measurement time points, week 1 and week 12 after surgery were chosen. The subjective visual scoring was compared to the objective data of the pressure sensing mat. Following the visual score, lameness in week one was mild to moderate. In week twelve, rabbits were evaluated as lame free bar one. Contrary, following the values of the sensor mat, lameness in week one appeared to be more pronounced and almost all rabbits still showed low-grade lameness in week twelve. Consequently, the pressure sensing mat is more sensitive than the visual score and captures the grade of lameness much more accurately. For specific orthopaedic issues, where subtle differences in lameness are important to detect, the used system is a good supplementary evaluation method.

Effects of Immobilization and Swimming on the Progression of Osteoarthritis in Mice

Osteoarthritis (OA) is a chronic joint disease characterized by the degeneration of articular cartilage and thickening and sclerosis of the subchondral bone. Mechanical factors play significant roles in the development and progression of OA, but it is still controversial whether exercise or rest is a more effective treatment for OA patients. In this study, we compared the effects of swimming and immobilization at different stages of OA in mice. Four weeks (the middle stage of OA) or eight weeks (the late stage of OA) after DMM (destabilization of the medial meniscus) surgery, the mice were subjected to four-week immobilization or swimming. Ink blot analysis and a beam walking test were performed to measure the gait and balance ability. Histological analysis was performed to determine the trabecular bone area, the thickness of subchondral bone, the thickness of the cartilage, the OARSI score, and the expression of MMP13 (matrix metalloproteinases) and IL-6 (interleukin). The results showed that at the middle stage of OA, both immobilization and swimming slowed down the progression of OA. Immobilization relieved OA to a certain extent by decreasing the production of regulatory factors to attenuate the degeneration of cartilage, which partly relieved the effects of DMM on gait, mainly in the hindlimb. Swimming mainly attenuated the thickening and rescued the area of subchondral bone.

Small laboratory animal models of anterior cruciate ligament reconstruction

Anterior cruciate ligament (ACL) injuries are common knee ligament injuries. While generally successful, ACL reconstruction that uses a tendon graft to stabilize the knee is still associated with a notable percentage of failures and long-term morbidities. Preclinical research that uses small laboratory species (i.e., mice, rats, and rabbits) to model ACL reconstruction are important to evaluate factors that can impact graft incorporation or posttraumatic osteoarthritis after ACL reconstruction. Small animal ACL reconstruction models are also used for proof-of-concept studies for the development of emerging biological strategies aimed at improving ACL reconstruction healing. The objective of this review is to provide an overview on the use of common small animal laboratory species to model ACL reconstruction. The review includes a discussion on comparative knee anatomy, technical considerations including types of tendon grafts employed amongst the small laboratory species (i.e., mice, rats, and rabbits), and common laboratory evaluative methods used to study healing and outcomes after ACL reconstruction in small laboratory animals. The review will also highlight common research questions addressed with small animal models of ACL reconstruction.

Comparative anatomy and morphology of the knee in translational models for articular cartilage disorders. Part II: Small animals

BACKGROUND

Small animal models are critical to model the complex disease mechanisms affecting a functional joint leading to articular cartilage disorders. They are advantageous for several reasons and significantly contributed to the understanding of the mechanisms of cartilage diseases among which osteoarthritis.

METHODS

Literature search in Pubmed.

RESULTS AND DISCUSSION

This narrative review summarizes the most relevant anatomical structural and functional characteristics of the knee (stifle) joints of the major small animal species, including mice, rats, guinea pigs, and rabbits compared with humans. Specific characteristics of each species, including kinematical gait parameters are provided and compared with the human situation. When placed in a proper context respecting their challenges and limitations, small animal models are important and appropriate models for articular cartilage disorders.

Use of the Contralateral Knee as a Control in the Destabilization of Medial Meniscus Osteoarthritis Rat Model

Destabilization of the medial meniscus (DMM) induces osteoarthritis (OA) in a rat model, but using the contralateral limb as control is unknown. We examined DMM and obesity in an OA rat model using contralateral limbs as control. Femoral condyles and tibial plateaus were evaluated. No differences were found between knees across diet groups (P=.61) or between surgery scores in diet groups (both P>.49). Thus, contralateral limbs may be a control for short-term (≤4 weeks) studies.

Factors affecting the reliability of behavioral assessments for rodent osteoarthritis models

The translational value of osteoarthritis (OA) models is often debated because numerous studies have shown that animal models frequently fail to predict the efficacy of therapies in humans. In part, this failing may be due to the paucity of preclinical studies that include behavioral assessments in their metrics. Behavioral assessments of animal OA models can provide valuable data on the pain and disability associated with disease-sequelae of significant clinical relevance. Clinical definitions of efficacy for OA therapeutics often center on their palliative effects. Thus, the widespread inclusion of behaviors indicative of pain and disability in preclinical animal studies may contribute to greater success identifying clinically relevant interventions. Unfortunately, studies that include behavioral assays still frequently encounter pitfalls in assay selection, protocol consistency, and data/methods transparency. Targeted selection of behavioral assays, with consideration of the array of clinical OA phenotypes and the limitations of individual behavioral assays, is necessary to identify clinically relevant outcomes in OA animal models appropriately. Furthermore, to facilitate accurate comparisons across research groups and studies, it is necessary to improve the transparency of methods. Finally, establishing agreed-upon and clear definitions of behavioral data will reduce the convolution of data both within and between studies. Improvement in these areas is critical to the continued benefit of preclinical animal studies as translationally relevant data in OA research. As such, this review highlights the current state of behavioral analyses in preclinical OA models.

Total Knee Arthroplasty with a Ti6Al4V/PEEK Prosthesis on an Osteoarthritis Rat Model: Behavioral and Neurophysiological Analysis

Arthroplasty is a surgical procedure to restore the function of the joint of patient suffering from knee osteoarthritis. However, postoperative functional deficits are reported even after a rehabilitation program. In order to determine the origin of functional deficits of patient suffering from knee osteoarthritis and total knee arthroplasty, we developed a rodent model including a chemically-induced-osteoarthritis and designed a knee prosthesis (Ti6Al4V/PEEK) biomechanically and anatomically adapted to rat knee joint. Dynamic Weight-Bearing, gait kinematics, H-reflex from vastus medialis muscle and activities from metabosensitive III and IV afferent fibers in femoral nerve were assessed at 1 and 3 months post-surgery. Results indicate that knee osteoarthritis altered considerably the responses of afferent fibers to their known activators (i.e., lactic acid and potassium chloride) and consequently their ability to modulate the spinal sensorimotor loop, although, paradoxically, motor deficits seemed relatively light. On the contrary, results indicate that, after the total knee arthroplasty, the afferent responses and the sensorimotor function were slightly altered but that motor deficits were more severe. We conclude that neural changes attested by the recovery of the metabosensitive afferent activity and the sensorimotor loop were induced when a total knee replacement was performed and that these changes may disrupt or delay the locomotor recovery.

Effects of treadmill running and limb immobilization on knee cartilage degeneration and locomotor joint kinematics in rats following knee meniscal transection

OBJECTIVE

This study examined the effects of reduced and elevated weight bearing on post-traumatic osteoarthritis (PTOA) development, locomotor joint kinematics, and degree of voluntary activity in rats following medial meniscal transection (MMT).

DESIGN

Twenty-one adult rats were subjected to MMT surgery of the left hindlimb and then assigned to one of three groups: (1) regular (i.e., no intervention), (2) hindlimb immobilization, or (3) treadmill running. Sham surgery was performed in four additional rats. Voluntary wheel run time/distance was measured, and 3D hindlimb kinematics were quantified during treadmill locomotion using biplanar radiography. Rats were euthanized 8 weeks after MMT or sham surgery, and the microstructure of the tibial cartilage and subchondral bone was quantified using contrast enhanced micro-CT.

RESULTS

All three MMT groups showed signs of PTOA (full-thickness lesions and/or increased cartilage volume) compared to the sham group, however the regular and treadmill-running groups had greater osteophyte formation than the immobilization group. For the immobilization group, increased volume was only observed in the anterior region of the cartilage. The treadmill-running group demonstrated a greater knee varus angle at mid-stance than the sham group, while the immobilization group demonstrated greater reduction in voluntary running than all the other groups at 2 weeks post-surgery.

CONCLUSIONS

Elevated weight-bearing via treadmill running at a slow/moderate speed did not accelerate PTOA in MMT rats when compared to regular weight-bearing. Reduced weight-bearing via immobilization may attenuate overall PTOA but still resulted in regional cartilage degeneration. Overall, there were minimal differences in hindlimb kinematics and voluntary running between MMT and sham rats.

Neuron-specific inactivation of Wt1 alters locomotion in mice and changes interneuron composition in the spinal cord

Locomotion is coordinated by neuronal circuits of the spinal cord. Recently, dI6 neurons were shown to participate in the control of locomotion. A subpopulation of dI6 neurons expresses the Wilms tumor suppressor gene Wt1. However, the function of Wt1 in these cells is not understood. Here, we aimed to identify behavioral changes and cellular alterations in the spinal cord associated with Wt1 deletion. Locomotion analyses of mice with neuron-specific Wt1 deletion revealed a slower walk with a decreased stride frequency and an increased stride length. These mice showed changes in their fore-/hindlimb coordination, which were accompanied by a loss of contralateral projections in the spinal cord. Neonates with Wt1 deletion displayed an increase in uncoordinated hindlimb movements and their motor neuron output was arrhythmic with a decreased frequency. The population size of dI6, V0, and V2a neurons in the developing spinal cord of conditional Wt1 mutants was significantly altered. These results show that the development of particular dI6 neurons depends on Wt1 expression and that loss of Wt1 is associated with alterations in locomotion.

Bone replaces articular cartilage in the rat knee joint after prolonged immobilization

BACKGROUND

Lost joint range of motion (ROM) is common in chronic osteoarthritis, alters regional weight-bearing across the articular surfaces, and contributes to loss of cartilage and bone alterations. Limited data exist on the regional effects on joints subjected to chronic losses of ROM.

OBJECTIVE

To characterize the regional replacement by bone as part of articular cartilage degeneration after prolonged immobilization.

METHODS

Eleven rat knees were rigidly-immobilized in flexion for 32weeks with contralateral and sham-operated (n=6) knees as controls. Sagittal medial tibial epiphysis histological sections assessed the anterior (non-weight-bearing), middle and posterior (both weight-bearing) regions. We quantified the distribution of collagen I, collagen II, cartilage thickness, glycosaminoglycan (GAG) staining, Mankin scoring, and subchondral bone plate cross-sectional area. Using immunohistochemistry (IHC), we visualized blood vessels, osteoblasts, and mesenchymal stem cells (MSCs).

RESULTS

Immobilized cartilage had increased collagen I content in the anterior tibial region with picrosirius red staining (immobilized=61±20%; contralateral=43±12%, p=0.033; sham=20±10%, p=0.028) and collagen I IHC (immobilized=40±10%; contralateral=11±4%, p=0.003; sham=5±3%, p=0.043). Articular cartilage was thinner anteriorly (18±30μm) in immobilized knees versus contralateral (124±40μm, p<0.001) and sham (125±43μm, p=0.043). GAG staining covered 2±4% of the anterior articular area in immobilized knees versus 28±12% contralaterally (p=0.003) and 26±7% in sham (p=0.043). Mankin scores in immobilized knees were 4.7±1.7 versus 0.2±0.4 and 0±0 for contralateral and sham (p=0.003, p=0.042), respectively. The trabecular bone plate area of anterior and posterior regions showed relative loss of cross-sectional area in immobilized knees compared to controls (immobilized/contralateral area ratios of 0.67 and 0.46 respectively, both p=0.003), while the area in the middle region was preserved. Movat's pentachrome stain and CD31 staining showed chondral vascular ingrowth from subchondral bone. Osteocalcin and CD90 MSC staining were decreased in immobilized knees versus contralateral (p=0.003, p=0.036 respectively).

CONCLUSIONS

Bony replacement characterizes articular cartilage degeneration of knees immobilized for 32weeks in the anterior, non-weight bearing region of the tibia. Replacement of cartilage by bone may have been mediated by chondral vascularization, suggesting irreversible changes. These findings stress the importance of weight-bearing and joint motion to maintain cartilage structure.

Gait analysis methods for rodent models of arthritic disorders: reviews and recommendations

Gait analysis is a useful tool to understand behavioral changes in preclinical arthritis models. While observational scoring and spatiotemporal gait parameters are the most widely performed gait analyses in rodents, commercially available systems can now provide quantitative assessments of spatiotemporal patterns. However, inconsistencies remain between testing platforms, and laboratories often select different gait pattern descriptors to report in the literature. Rodent gait can also be described through kinetic and kinematic analyses, but systems to analyze rodent kinetics and kinematics are typically custom made and often require sensitive, custom equipment. While the use of rodent gait analysis rapidly expands, it is important to remember that, while rodent gait analysis is a relatively modern behavioral assay, the study of quadrupedal gait is not new. Nearly all gait parameters are correlated, and a collection of gait parameters is needed to understand a compensatory gait pattern used by the animal. As such, a change in a single gait parameter is unlikely to tell the full biomechanical story; and to effectively use gait analysis, one must consider how multiple different parameters contribute to an altered gait pattern. The goal of this article is to review rodent gait analysis techniques and provide recommendations on how to use these technologies in rodent arthritis models, including discussions on the strengths and limitations of observational scoring, spatiotemporal, kinetic, and kinematic measures. Recognizing rodent gait analysis is an evolving tool, we also provide technical recommendations we hope will improve the utility of these analyses in the future.

Long-Lasting Activation of the Transcription Factor CREB in Sensory Neurons by Interleukin-1β During Antigen-Induced Arthritis in Rats: A Mechanism of Persistent Arthritis Pain?

OBJECTIVE

In spite of successful treatment of immune-mediated arthritis, many patients still experience pain. We undertook this study to investigate whether antigen-induced arthritis (AIA) in rats triggers neuronal changes in sensory neurons that outlast the inflammatory process.

METHODS

We induced unilateral AIA in the knee joint and assessed in sensory neurons the expression of CREB, a transcription factor that regulates genes involved in neuronal plasticity. We tested whether neutralization of the effects of tumor necrosis factor (TNF) by etanercept or infliximab or neutralization of the effects of interleukin-1β (IL-1β) by anakinra influences the up-regulation of phospho-CREB, and we studied the up-regulation of phospho-CREB by IL-1β and TNF in cultured dorsal root ganglion (DRG) neurons.

RESULTS

Unilateral AIA caused bilateral up-regulation of phospho-CREB in lumbar DRG neurons. While inflammation and pain subsided within 21 days, the up-regulation of phospho-CREB still persisted on day 42. At this time point mechanical hyperalgesia at the knee reappeared in the absence of swelling. TNF neutralization during AIA significantly reduced pain-related behavior but did not prevent phospho-CREB up-regulation. In contrast, anakinra, which only reduced thermal hyperalgesia, prevented phospho-CREB up-regulation, suggesting a role of IL-1β in this process. In cultured DRG neurons the application of IL-1β significantly enhanced phospho-CREB.

CONCLUSION

Immune-mediated arthritis causes neuroplastic changes in sensory neurons that outlast the inflammatory phase. Such changes may facilitate the persistence or recurrence of pain after remission of arthritis. IL-1β is an important trigger in this process, although its neutralization barely reduced mechanical hyperalgesia during inflammation.

Gait analysis methods for rodent models of osteoarthritis

Patients with osteoarthritis (OA) primarily seek treatment due to pain and disability, yet the primary endpoints for rodent OA models tend to be histological measures of joint destruction. The discrepancy between clinical and preclinical evaluations is problematic, given that radiographic evidence of OA in humans does not always correlate to the severity of patient-reported symptoms. Recent advances in behavioral analyses have provided new methods to evaluate disease sequelae in rodents. Of particular relevance to rodent OA models are methods to assess rodent gait. While obvious differences exist between quadrupedal and bipedal gait sequences, the gait abnormalities seen in humans and in rodent OA models reflect similar compensatory behaviors that protect an injured limb from loading. The purpose of this review is to describe these compensations and current methods used to assess rodent gait characteristics, while detailing important considerations for the selection of gait analysis methods in rodent OA models.

Coxofemoral joint kinematics using video fluoroscopic images of treadmill-walking cats: development of a technique to assess osteoarthritis-associated disability

The objectives of this pilot study were to develop a video fluoroscopy kinematics method for the assessment of the coxofemoral joint in cats with and without osteoarthritis (OA)-associated disability. Two non-OA cats and four cats affected by coxofemoral OA were evaluated by video fluoroscopy. Video fluoroscopic images of the coxofemoral joints were captured at 120 frames/s using a customized C-arm X-ray system while cats walked freely on a treadmill at 0.4 m/s. The angle patterns over time of the coxofemoral joints were extracted using a graphic user interface following four steps: (i) correction for image distortion; (ii) image denoising and contrast enhancement; (iii) frame-to-frame anatomical marker identification; and (iv) statistical gait analysis. Reliability analysis was performed. The cats with OA presented greater intra-subject stride and gait cycle variability. Three cats with OA presented a left-right asymmetry in the range of movement of the coxofemoral joint angle in the sagittal plane (two with no overlap of the 95% confidence interval, and one with only a slight overlap) consistent with their painful OA joint, and a longer gait cycle duration. Reliability analysis revealed an absolute variation in the coxofemoral joint angle of 2º-6º, indicating that the two-dimensional video fluoroscopy technique provided reliable data. Improvement of this method is recommended: variability would likely be reduced if a larger field of view could be recorded, allowing the identification and tracking of each femoral axis, rather than the trochanter landmarks. The range of movement of the coxofemoral joint has the potential to be an objective marker of OA-associated disability.

The role of vibrissal sensing in forelimb position control during travelling locomotion in the rat (Rattus norvegicus, Rodentia)

In the stem lineage of therians, a comprehensive reorganization of limb and body mechanics took place to provide dynamic stability for rapid locomotion in a highly structured environment. At what was probably the same time, mammals developed an active sense of touch in the form of movable mystacial vibrissae. The rhythmic movements of the limbs and vibrissae are controlled by central pattern-generating networks which might interact with each other in sensorimotor control. To test this possible interaction, we studied covariation between the two by investigating speed-dependent adjustments in temporal and spatial parameters of forelimb and vibrissal kinematics in the rat. Furthermore, the possible role of carpal vibrissae in connecting the two oscillating systems was explored. We compared locomotion on continuous and discontinuous substrates in the presence and absence of the mystacial or/and carpal vibrissae across a speed range of 0.2-0.5m/s and found that a close coupling of the kinematics of the two oscillating systems appears to be precluded by their differential dependence on the animal's speed. Speed-related changes in forelimb kinematics mainly occur in temporal parameters, whereas vibrissae change their spatial excursion. However, whisking frequency is always high enough that at least one whisk cycle falls into the swing phase of the limb, which is the maximum critical period for sensing the substrate on which the forepaw will be placed. The influence of tactile cues on forelimb positional control is more subtle than expected. Tactile cues appear to affect the degree of parameter variation but not average parameters or the failure rate of limbs during walking on a perforated treadmill. The carpal vibrissae appear to play a role in sensing the animal's speed by measuring the duration of the stance phase. The absence of this cue significantly reduces speed-related variation in stride frequency and vibrissal protraction.

Enhanced neurogenesis in the hippocampal dentate gyrus during antigen-induced arthritis in adult rat--a crucial role of immunization

Neurogenesis in the subgranular zone of the mammalian hippocampal dentate gyrus contributes significantly to brain neuroplasticity. There is evidence that inflammation of the central nervous system inhibits neurogenesis but peripheral inflammation such as antigen-induced arthritis may rather enhance neurogenesis. Manifest arthritis is associated with symptoms such as pain and altered locomotion indicating that peripheral inflammation is associated with changes of both the immune system and the nervous system. This raises the intriguing question whether immune or neuronal factors or both actually drive changes of neurogenesis. Here we explored hippocampal neurogenesis in the rat during chronic antigen-induced arthritis in the knee joint. We analyzed neurogenesis in control rats, and in rats which were immunized for the antigen producing arthritis but which did not show arthritis and neurological symptoms, and in rats in which antigen injection into the knee produced manifest local inflammation and symptoms such as pain at the inflamed knee and altered locomotor behavior. Neurogenesis was assessed by quantifying bromodeoxyuridine-positive cells in sections of the complete hippocampal dentate gyrus. Compared to control animals, rats with antigen-induced arthritis presenting manifest local inflammation, hyperalgesia at the inflamed knee and significantly altered locomotion exhibited a significant increase of bromodeoxyuridine-positive cells. However, a similar increase in the number of such cells was found in rats which were only immunized against the antigen, but in which no local inflammatory response was induced and which thereby neither showed hyperalgesia nor alterations of locomotion. Thus we conclude that in peripheral immune-mediated arthritis the activation of the immune system in the process of immunization is the causal factor driving enhanced neurogenesis, and neither the local enhancement of inflammation nor the activation of the nervous system leading to neurological symptoms such as pain and altered locomotion. It seems noteworthy to further explore the clinical importance of this neuroimmune interaction.

Animal models of osteoarthritis: challenges of model selection and analysis

Osteoarthritis (OA) is the most common musculoskeletal disease, affecting millions of individuals worldwide. New treatment approaches require an understanding of the pathophysiology of OA and its biomechanical, inflammatory, genetic, and environmental risk factors. The purpose of animal models of OA is to reproduce the pattern and progression of degenerative damage in a controlled fashion, so that opportunities to monitor and modulate symptoms and disease progression can be identified and new therapies developed. This review discusses the features, strengths, and weaknesses of the common animal models of OA; considerations to be taken when choosing a method for experimental induction of joint degeneration; and the challenges of measuring of OA progression and symptoms in these models.