Immunopathological mechanisms in dogs with rupture of the cranial cruciate ligament

Infrared Spectroscopy of Synovial Fluid Shows Accuracy as an Early Biomarker in an Equine Model of Traumatic Osteoarthritis

Osteoarthritis is a leading cause of lameness and joint disease in horses. A simple, economical, and accurate diagnostic test is required for routine screening for OA. This study aimed to evaluate infrared (IR)-based synovial fluid biomarker profiling to detect early changes associated with a traumatically induced model of equine carpal osteoarthritis (OA). Unilateral carpal OA was induced arthroscopically in 9 of 17 healthy thoroughbred fillies; the remainder served as Sham-operated controls. The median age of both groups was 2 years. Synovial fluid (SF) was obtained before surgical induction of OA (Day 0) and weekly until Day 63. IR absorbance spectra were acquired from dried SF films. Following spectral pre-processing, predictive models using random forests were used to differentiate OA, Sham, and Control samples. The accuracy for distinguishing between OA and any other joint group was 80%. The classification accuracy by sampling day was 87%. For paired classification tasks, the accuracies by joint were 75% for OA vs. OA Control and 70% for OA vs. Sham. The accuracy for separating horses by group (OA vs. Sham) was 68%. In conclusion, SF IR spectroscopy accurately discriminates traumatically induced OA joints from controls.

Endocannabinoid System Receptors at the Hip and Stifle Joints of Middle-Aged Dogs: A Novel Target for the Therapeutic Use of Cannabis sativa Extract in Canine Arthropathies

The endocannabinoid system (ECS) has emerged as a potential therapeutic target in veterinary medicine due to its involvement in a wide range of physiological processes including pain, inflammation, immune function, and neurological function. Modulation of the ECS receptors has been shown to have anti-inflammatory, analgesic, and immunomodulatory effects in various animal models of disease, including dogs with osteoarthritis. The goal of this study was to identify and compare the cellular expression and distribution of cannabinoid receptor type 1 (CB1R) and type 2 (CB2R) and the cannabinoid-related G protein-coupled receptor 55 (GPR55) on the synovial cells of hip and stifle joints of seven dogs of different breeds without overt signs of osteoarthritis (OA). The synovial membranes of seven hips and seven stifle joints were harvested post mortem. The expression of the CB1R, CB2R, and GPR55 present in the synovial tissues was investigated using qualitative and quantitative immunofluorescence and Western blot (Wb) analysis. Synoviocytes of the stifle and hip joints expressed CB1R, CB2R, and GPR55 immunoreactivity (IR); no significant differences were observed for each different joint. Cannabinoid receptor 2- and GPR55-IR were also expressed by macrophages, neutrophils, and vascular cells. The ECS receptors were widely expressed by the synovial elements of dogs without overt signs of OA. It suggests that the ECS could be a target for the therapeutic use of Cannabis sativa extract in canine arthropathies.

The Single Intra-Articular Injection of Platelet-Rich Plasma vs. Non-Steroidal Anti-Inflammatory Drugs as Treatment Options for Canine Cruciate Ligament Rupture and Patellar Luxation

Cranial cruciate ligament rupture (CCLR) and patellar luxation (PL) are common pathologies affecting canines. Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used as a non-surgical treatment plan in these cases. Clinical usage of platelet-rich plasma (PRP) is an emerging area of interest in veterinary medicine. There is a lack of studies comparing those two different treatment methods in veterinary medicine. The main purpose of this study was to evaluate and compare the use of oral NSAIDs and single intra-articular injection of PRP on treatment outcomes in cases of canine CCLR and PL. Dogs diagnosed with CCRL (n = 12) and PL (n = 10) were subgrouped by the severity of pathologies and administered treatment: half of the CCRL and PL groups were orally administered NSAIDs and supplements for 14 days, and the other half received a single intra-articular PRP injection into affected stifle joint. We measured serum TNF-α levels and clinical outcomes (lameness scores, painfulness to manipulations, goniometry of stifle joint in flexion and extension, and muscle strength) before treatment, at day 14 and day 28 of treatment. The results of TNF-α concentration indicates a significant difference between groups of differently treated partial CCLR groups on d14 (p = 0.006). Results of group CCLR-P1 on d14 were decreased, while results of group CCLR-P2 on d14 were increased. When comparing TNF-α concentration between all CCLR cases treated with NSAIDs and treated with PRP, there was a significant difference between those groups on d14 (p = 0.001). The results of TNF-α concentration indicates a significant difference between groups of differently treated PL-III on d28 (p = 0.036). Results of group PL-III1 indicate growth of TNF-α concentration, while at the same d28, results of group PL-III2 indicate decreased levels of cytokine, comparing results between the subgroups at the same time point and within subgroups from baseline. Results indicate a significant difference in muscle strength between group CCLR-P1 and group CCLR-P2 on d28 (p = 0.007), indicating an increment in muscle strength in group CCLR-P1 up to d14 and its reduction up to d28, and muscle strength of group CCLR-P2 increasing up to d28. When comparing the muscle strength between all CCLR cases treated with NSAIDs and treated with PRP, there was a significant difference between those groups on d28 (p = 0.007). In conclusion, a single intra-articular injection of PRP has a superior effect on management of inflammatory processes, has better clinical outcomes, and longer duration of action than oral NSAIDs, in the treatment of canine CCRL or PL.

Clinical effectiveness and safety of intraarticular administration of a 117m Tin radiocolloid (Synovetin OATM ) for treatment of early and intermediate grade osteoarthritis of the elbow in a dose finding study conducted in 44 dogs

Osteoarthritis of the elbow joint secondary to elbow dysplasia is common in dogs. Intraarticular radionuclide injection is thought to suppress both synovitis and inflammatory pain mediators in the joint which are not directly addressed by current treatments. This dose-finding investigation was a longitudinal, prospective, experimental parallel group, post-test study with repeated measures. Forty-four dogs, with low to intermediate-grade osteoarthritis, received a single injection into their most clinically affected elbow joint and were randomized into three treatment cohorts; 37 MBq, 64.75 MBq, or 92.5 MBq (normalized to the body surface area of a 22 kg dog) of 117m Sn radiocolloid. Dogs were assessed monthly by owners, using the canine Brief Pain Inventory (cBPI), and at 1, 3, 6, 9, and 12 months intervals by investigators. Positive responses to treatment were observed by both owners and clinicians in all dose groups with the medium dose group having the highest and most durable response rate based on cBPI scores. The results of this study support the use of 117m Sn radiocolloid as a primary treatment of osteoarthritis in low to intermediate-grade osteoarthritis of the canine elbow.

Etiopathogenesis of Canine Cruciate Ligament Disease: A Scoping Review

The spontaneous rupture of the cranial cruciate ligament in dogs remains a pathoetiologic puzzle. Despite much progress in research over the past years, the systemic and local mechanisms leading to ligament degeneration and structural failure remain largely obscure. This scoping review focuses on pathogenesis and aims at summarizing and interpreting today's knowledge on causes of canine cruciate ligament rupture, i.e., the multifactorial mechanisms leading to degenerative stifle joint disease with collagen matrix degeneration and structural failures. Thus, the initial view of traumatic ligament rupture, fostered by "wear and tear", has clearly been replaced by a new concept of systemic processes linked to progressive degenerative joint disease and ligament failure; thus, the term "cranial cruciate ligament disease" has been coined and is generally accepted. In addition, cruciate ligament rupture in people shares some similarities with the lesion in dogs; therefore, the review also includes comparative studies. The methods used were based on the PRISMA-ScR model (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews).

The Role of Tibial Plateau Angle in Canine Cruciate Ligament Rupture-A Review of the Literature

Cranial cruciate ligament disease is a common pathological condition in dogs that is often presented in daily clinical practice. Different risk factors for the development of this condition include breed, sex, age, bodyweight and neuter status, as well as different biological and biomechanical mechanisms. In the literature, special attention has been paid to the role of the tibial plateau angle in damage to the cranial cruciate ligament. Although the disease was first described at the beginning of last century, and since then different surgical methods have been developed to treat it, its aetiology remains unclear. In this review, contemporary literature data related to the role of tibial plateau angle in canine cranial cruciate ligament rupture are presented.

Detection of vector-borne pathogens in owned dogs with cranial cruciate ligament rupture living in the Mediterranean area

Background

Cranial cruciate ligament rupture (CCLR) results from a multifactorial degenerative process that leads to rupture of the ligament. Vector-borne pathogens (VBP) in dogs can induce joint disease but their role in CCLR has not been previously investigated. The aim of the present work is to evaluate the prevalence of VBP in dogs with CCLR.

Methods

This was a prospective study that included 46 dogs presented for CCLR surgical treatment and 16 control dogs euthanized for diseases unrelated to the joints. Specimens collected included blood, synovial fluid, and synovial membrane biopsy. Pathogen testing consisted of serology for Leishmania infantum (quantitative ELISA), Ehrlichia canis/ewingii, Borrelia burgdorferi, Anaplasma phagocytophilum/platys, and Dirofilaria immitis (4DX IDEXX test), and PCR for L. infantum, Ehrlichia/Anaplasma spp., Bartonella spp., piroplasms (Babesia spp. and Theileria spp.), and filariae (D. immitis, Dirofilaria repens, Acanthocheilonema dracunculoides, Acanthocheilonema reconditum, and Cercopithifilaria spp.) on both EDTA-whole blood (EB) and synovial fluid (SF) samples. SF cytology and histopathological evaluation of synovial membrane were also performed.

Results

The prevalence of VBP was 19.6% in the CCLR group and 18.8% in the control group, with no statistical difference among them. The presence of synovitis was not more frequent in CCLR dogs (45.6%) than in control dogs (43.7%). Lymphoplasmacytic infiltration was the most common inflammatory pattern detected in the joints of both groups of dogs.

Conclusions

This study failed to demonstrate a role of canine VBP in CCLR or the presence or different pattern of joint inflammation in pathogen-positive dogs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05205-x.

Immunoexpression of Relaxin and Its Receptors in Stifle Joints of Dogs with Cranial Cruciate Ligament Disease

Simple Summary

Spontaneous cranial cruciate ligament rupture is one of the most frequently encountered joint diseases in dogs, often leading to disabling chronic progressive osteoarthritis. The cause of the progressive intra-articular collagen matrix degradation, leading to tear and mechanical failure, is unknown. A variety of contributing factors has been found, however, an initiating mediator triggering the collagen degrading cascade remains to be identified. Our finding of strong relaxin- and relaxin receptor expression on intra-articular target tissues, such as on ligament fibrocytes and synovial membranes, renders relaxin a candidate for pathogenetic involvement, for collagen lysis, and progressive ligament fiber disruption. If confirmed, this opens the way for medical treatment of the disease in its early stages. In addition, further proof of relaxin involvement in canine osteoarthritis and ligament rupture would constitute a useful spontaneous animal model for human disease.

Abstract

The etiology of spontaneous cranial cruciate ligament rupture in dogs is unknown despite being one of the most impacting orthopedic diseases in dogs. Numerous studies have contributed to the understanding of a multifactorial pathogenesis, this, however, without identifying a pivotal link to explain progressive collagen degeneration and osteoarthritic changes. In human medicine, recent reports have identified relaxin as a triggering factor in ligament ruptures in knee and metacarpal joints. We thus hypothesized that relaxin might also play a role in canine cruciate ligament rupture. Relaxin’s primarily known property is connective tissue remodeling through collagenolysis. We therefore investigated relaxin and its cognate receptors LGR7/LGR8 in 18 dogs with cranial cruciate ligament disease (CCLD) and compared them to a group of dogs with normal stifle joints. Applying immunohistochemistry (IHC), double immunofluorescence (dIF), and western blot analysis (WB), we found strong and significantly increased expression of both relaxin and its receptors in ruptured cruciate ligaments, and in synovial membranes. Pattern of immuno-staining on dIF strongly suggests relaxin binding to primed receptors and activation of signaling properties, which in turn may have affected collagen matrix metabolism. Thus, in canine cranial cruciate ligament disease, relaxin/receptor signaling may be a primary trigger for collagen fiber degradation and collagen lysis, eventually followed by ligament rupture.

Relationship of mRNA Expression of Selected Genes in Peripheral Blood and Synovial Fluid in Cranial Cruciate Ligament Deficient Stifles of Dogs

Simple Summary

The cranial cruciate ligament rupture is characterized by chronic inflammation, osteoarthritis of the stifle joint, and extracellular matrix degeneration of the ligament itself in dogs. Early pre-clinical cranial cruciate ligament alteration cannot be detected by clinical examination or standard radiography. Therefore, we assessed the possible relationship of inflammatory markers in peripheral blood and synovial fluid of affected stifle joints in comparison to a control. We also evaluated components of the extracellular matrix of ruptured ligaments and finally compared the tibial plateau angle and the anatomical-mechanical angle between groups. Some of the assessed inflammatory markers were significantly increased in both the peripheral blood and synovial fluid compared with the control, as were collagens. The tibial plateau angle was not significantly different; however, the anatomical-mechanical angle significantly increased in the ruptured ligaments. Our results suggest a possible positive relationship between inflammatory markers of blood and synovial fluid in cranial cruciate ligament deficient stifles compared to the control. These findings may support both local and systemic inflammation process at the same time during osteoarthritis progression. Based on this, it would be interesting to investigate the predictive osteoarthritis pathway of inflammatory cytokines, matrix metalloproteinases, and their effect on the extracellular matrix components of the cranial cruciate ligament in future studies.

Abstract

The cranial cruciate ligament rupture (CrCLR) is characterized by chronic inflammation and osteoarthritis (OA) of the stifle joint and extracellular matrix (ECM) degeneration of the ligament itself in dogs. Generally, OA may arise from chronic low-grade systemic inflammation. We assessed the possible relationship of inflammatory markers in the peripheral blood (PB) and synovial fluid (SF) of affected stifle joints in comparison to a control. Moreover, no study has shown the possible association between PB and SF levels of inflammatory markers in CrCLR stifles of dogs in veterinary medicine yet. We also evaluated components of ECM of CrCLR and finally compared the tibial plateau angle (TPA) and the anatomical-mechanical angle (AMA) between groups. Samples from PB and SF were examined for mRNA expression of interleukins, TNF-α and INF-γ. ECM components—collagen 1A1 and 3A1 and elastin—were examined for mRNA expression from SF. The level of relative expression for IL-1β, IL-8 and IFN-γ was significantly increased in both PB and SF in CrCLR stifles as compared with the control. Collagens were also significantly increased in CrCLR stifles. TPA was not significantly different; however, the AMA angle significantly increased in the CrCLR group. Our results suggest a possible relationship between PB and SF levels of inflammatory markers in CrCLR stifles of dogs.

Safety and Clinical Response Following a Repeat Intraarticular Injection of Tin-117m (117mSn) Colloid in Dogs with Elbow Osteoarthritis

Objective

To determine if a repeat intraarticular (IA) injection of a tin-117m colloid radiosynoviorthesis (RSO) agent can be safely given in the same joint 12 months after an initial injection for treatment of canine elbow osteoarthritis (OA), and to evaluate the pain reduction effect of the repeat injection.

Methods and Materials

Nine client owned dogs with grade 1 or 2 elbow OA were given an IA injection of tin-117m colloid in both elbows, one of which had been treated ≤12 months earlier with the same RSO device. Treatment safety was evaluated by joint fluid analysis at baseline (BL) and at 180 days after treatment, and by urinalysis, CBC, and serum chemistry analysis of diagnostic samples obtained at BL and 180 days. Radiographs, computed tomography, and MRI scans were obtained at BL and 180 days to determine if disease progression differed in elbows given one versus two injections. Clinical response to treatment was assessed subjectively by dog owner responses to the Canine Brief Pain Inventory (CBPI) survey at BL, 90 and 180 days, and objectively by investigator-conducted force plate (FP) analysis of dogs at BL, 90, and 180 days.

Results

All post-treatment urinalysis, CBC and clinical chemistry results were within normal ranges. Joint fluid analysis showed a significant (P=0.0411) reduction in the percentage of monocytes at 180 days, consistent with the tin-117m colloid mode of action of apoptosis of pro-inflammatory macrophages at the injection site. There was no significant difference in OA progression in elbows given one or two injections. The treatment success rate was 55.5% (5/9) on day 90 as determined either by CBPI responses or FP analysis, and 66.6% (6/9) on day 180 as determined by FP analysis.

Conclusion

The tin-117m colloid can be safely given as a repeat injection 12 months after an initial injection, and can potentially provide a durable therapeutic response in dogs with elbow OA.

Cranial Cruciate Ligament Rupture in Dogs: Review on Biomechanics, Etiopathogenetic Factors and Rehabilitation

Cranial cruciate ligament (CrCL) rupture is one of the most common orthopaedic conditions in veterinary medicine. CrCL plays a fundamental role in the stability and biomechanics of the femoral-tibio-patellar joint, and its incorrect functionality severely impacts on the quality of life of patients. In dogs, the structural weakening of this joint due to the progressive degeneration of the ligament is the most accredited etiopathogenetic hypothesis in relation to the dog signalment (breed, sex and age) and the stifle joint conformation. In humans, this injury is often traumatic and generally occurs during sporting activities. CrCL rupture can be managed conservatively or surgically, and decisions regarding treatment are due to numerous factors: the patient’s age and health, the degree of stifle instability, and cost. Physiotherapy protocols play an important role in rehabilitation, with similar goals in humans and dogs: pain management, physiological articular range of motion recovery, periarticular and core muscle strengthening, and proprioceptive deficit correction. Physiotherapy, even if often neglected in veterinary medicine, is mandatory for the recovery of the correct functionality of the injured limb and for the return to normal daily and sporting activities.

Treatment of cranial cruciate ligament injuries in dogs using a combination of tibial tuberosity advancement procedure and autologous mesenchymal stem cells/multipotent mesenchymal stromal cells - A pilot study

In the present pilot study, we evaluated different supplemental therapies using autologous multipotent mesenchymal stromal cells (MMSCs) for the treatment of cranial cruciate ligament defects in dogs. We used tibial tuberosity advancement (TTA) and augmented it by supportive therapy with MMSCs in three patient groups. In the first patient group, the dogs were injected with MMSCs directly into the treated stifle one month after surgery. In the second group, MMSCs were delivered in a silk fibroin scaffold which was placed in the osteotomy gap during surgery. In the third group, MMSCs were first mixed with bone tissue and blood from the patient and delivered into the osteotomy gap during surgery. In the control group, patients underwent the TTA procedure but did not receive MMSC treatment. In the group of patients who received cells in the silk fibroin scaffold during surgery, the osteotomy gap did not heal, presumably due to the low absorption of silk fibroin. Patients who received MMSCs mixed with bone tissue and blood during surgery into the osteotomy gap recovered clinically faster and had better healing of the osteotomy gap than dogs from the other two treated groups and from the control group, as assessed by clinical examination and quantification of radiographs. In conclusion, dogs that received stem cells directly into the osteotomy gap (Group 3) recovered faster compared to dogs from Groups 1 (MMSCs injected into the joint one month after surgery), 2 (cells implanted into the osteotomy gap in a silk fibroin scaffold), and the control group that did not receive additional MMSCs treatment.

Analysis of copy number variation in dogs implicates genomic structural variation in the development of anterior cruciate ligament rupture

Anterior cruciate ligament (ACL) rupture is an important condition of the human knee. Second ruptures are common and societal costs are substantial. Canine cranial cruciate ligament (CCL) rupture closely models the human disease. CCL rupture is common in the Labrador Retriever (5.79% prevalence), ~100-fold more prevalent than in humans. Labrador Retriever CCL rupture is a polygenic complex disease, based on genome-wide association study (GWAS) of single nucleotide polymorphism (SNP) markers. Dissection of genetic variation in complex traits can be enhanced by studying structural variation, including copy number variants (CNVs). Dogs are an ideal model for CNV research because of reduced genetic variability within breeds and extensive phenotypic diversity across breeds. We studied the genetic etiology of CCL rupture by association analysis of CNV regions (CNVRs) using 110 case and 164 control Labrador Retrievers. CNVs were called from SNPs using three different programs (PennCNV, CNVPartition, and QuantiSNP). After quality control, CNV calls were combined to create CNVRs using ParseCNV and an association analysis was performed. We found no strong effect CNVRs but found 46 small effect (max(T) permutation P<0.05) CCL rupture associated CNVRs in 22 autosomes; 25 were deletions and 21 were duplications. Of the 46 CCL rupture associated CNVRs, we identified 39 unique regions. Thirty four were identified by a single calling algorithm, 3 were identified by two calling algorithms, and 2 were identified by all three algorithms. For 42 of the associated CNVRs, frequency in the population was <10% while 4 occurred at a frequency in the population ranging from 10–25%. Average CNVR length was 198,872bp and CNVRs covered 0.11 to 0.15% of the genome. All CNVRs were associated with case status. CNVRs did not overlap previous canine CCL rupture risk loci identified by GWAS. Associated CNVRs contained 152 annotated genes; 12 CNVRs did not have genes mapped to CanFam3.1. Using pathway analysis, a cluster of 19 homeobox domain transcript regulator genes was associated with CCL rupture (P = 6.6E-13). This gene cluster influences cranial-caudal body pattern formation during embryonic limb development. Clustered genes were found in 3 CNVRs on chromosome 14 (HoxA), 28 (NKX6-2), and 36 (HoxD). When analysis was limited to deletion CNVRs, the association was strengthened (P = 8.7E-16). This study suggests a component of the polygenic risk of CCL rupture in Labrador Retrievers is associated with small effect CNVs and may include aspects of stifle morphology regulated by homeobox domain transcript regulator genes.

Epidemiology of Cranial Cruciate Ligament Rupture and Patellar Luxation in Dogs from the Province of Buenos Aires, Argentina

OBJECTIVE

 The aim of this study was to investigate the prevalence of cranial cruciate ligament rupture and patellar luxation and the associated risk factors in dogs.

MATERIALS AND METHODS

 A total of 13,072 clinical records of dogs were reviewed from School Hospital (Faculty of Veterinary Sciences, National University of La Plata). Data of age, breed, sex, body weight, patellar luxation and cranial cruciate ligament rupture condition were registered. Chi-squared and Fisher's exact tests were used to compare the prevalence of cranial cruciate ligament rupture and patellar luxation with the variables and then univariable logistic regression was used to evaluate the risk of having cranial cruciate ligament rupture and patellar luxation. Multivariable logistic regression was used including all variables to assess the odds of having patellar luxation and cranial cruciate ligament rupture.

RESULTS

 Of 13,072 patients treated, 72 and 51 had cranial cruciate ligament rupture and patellar luxation respectively. Sex was not a major risk factor for either condition. Adult (odds ratio [OR] = 8.2) and senior (OR = 4.3) patients had increased risk of having cranial cruciate ligament rupture, while for patellar luxation age was not a risk factor. Groups 2, 3 and 8 were more likely to have cranial cruciate ligament rupture (OR = 5.5, OR = 9.1 and OR = 2.6), and group 11 had lower risk of having patellar luxation (OR = 0.08). Maxi (OR = 2.4) and giant (OR = 6.0) breeds had higher risk of having cranial cruciate ligament rupture, and medium and maxi breeds had higher risk of patellar luxation (OR = 0.05 and OR = 0.3). Multivariate OR test confirmed that age (adult), body size (giant and maxi) and breed group (Group 3) were significantly associated with having cranial cruciate ligament rupture, and age was associated with having patellar luxation.

CLINICAL SIGNIFICANCE

 This is the first epidemiological study of cranial cruciate ligament rupture and patellar luxation in dogs from School Hospital (Faculty of Veterinary Sciences, National University of La Plata). Giant and large adult dogs from the Molossoid and Terrier breeds were more likely to have cranial cruciate ligament rupture, while mixed and large dog breeds showed the lowest risk of having patellar luxation.

Synovial fluid lubricin increases in spontaneous canine cruciate ligament rupture

Lubricin is an important boundary lubricant and chondroprotective glycoprotein in synovial fluid. Both increased and decreased synovial fluid lubricin concentrations have been reported in experimental post-traumatic osteoarthritis (PTOA) animal models and in naturally occurring joint injuries in humans and animals, with no consensus about how lubricin is altered in different species or injury types. Increased synovial fluid lubricin has been observed following intra-articular fracture in humans and horses and in human late-stage osteoarthritis; however, it is unknown how synovial lubricin is affected by knee-destabilizing injuries in large animals. Spontaneous rupture of cranial cruciate ligament (RCCL), the anterior cruciate ligament equivalent in quadrupeds, is a common injury in dogs often accompanied by OA. Here, clinical records, radiographs, and synovial fluid samples from 30 dogs that sustained RCCL and 9 clinically healthy dogs were analyzed. Synovial fluid lubricin concentrations were nearly 16-fold greater in RCCL joints as compared to control joints, while IL-2, IL-6, IL-8, and TNF-α concentrations did not differ between groups. Synovial fluid lubricin concentrations were correlated with the presence of radiographic OA and were elevated in three animals sustaining RCCL injury prior to the radiographic manifestation of OA, indicating that lubricin may be a potential biomarker for early joint injury.

The Immune Cell Landscape in Different Anatomical Structures of Knee in Osteoarthritis: A Gene Expression-Based Study

Background

Immunological mechanisms play a vital role in the pathogenesis of knee osteoarthritis (KOA). Moreover, the immune phenotype is a relevant prognostic factor in various immune-related diseases. In this study, we used CIBERSORT for deconvolution of global gene expression data to define the immune cell landscape of different structures of knee in osteoarthritis. Methods and Findings. By applying CIBERSORT, we assessed the relative proportions of immune cells in 76 samples of knee cartilage, 146 samples of knee synovial tissue, 40 samples of meniscus, and 50 samples of knee subchondral bone. Enumeration and activation status of 22 immune cell subtypes were provided by the obtained immune cell profiles. In synovial tissues, the differences in proportions of plasma cells, M1 macrophages, M2 macrophages, activated dendritic cells, resting mast cells, and eosinophils between normal tissues and osteoarthritic tissues were statistically significant (P < 0.05). The area under the curve was relatively large in resting mast cells, dendritic cells, and M2 macrophages in receiver operating characteristic analyses. In subchondral bones, the differences in proportions of resting master cells and neutrophils between normal tissues and osteoarthritic tissues were statistically significant (P < 0.05). In subchondral bones, the proportions of immune cells, from the principle component analyses, displayed distinct group-bias clustering. Resting mast cells and T cell CD8 were the major component of first component. Moreover, we revealed the potential interaction between immune cells. There was almost no infiltration of immune cells in the meniscus and cartilage of the knee joint.

Conclusions

The immune cell composition in KOA differed substantially from that of healthy joint tissue, while it also differed in different anatomical structures of the knee. Meanwhile, activated mast cells were mainly associated with high immune cell infiltration in OA. Furthermore, we speculate M2 macrophages in synovium and mast cells in subchondral bone may play an important role in the pathogenesis of OA.

Proinflammatory polarization of stifle synovial macrophages in dogs with cruciate ligament rupture

OBJECTIVE

To determine polarization of synovial macrophages during development of cruciate ligament rupture (CR) and determine whether differences in synovial macrophage polarization in CR, osteoarthritis (OA), and healthy joints exist.

STUDY DESIGN

Prospective case-controlled study.

ANIMALS

Client-owned dogs with unstable stifles with CR (n = 22), paired stable contralateral stifles with partial CR (pCR; n = 7), joints with OA not related to CR (n = 6), and clinically normal (Normal; n = 7) joints.

METHODS

Synovial fluid samples were collected. Smears were made for differential cytology counts and estimated total nucleated cell counts. Cytospin preparations were made, and immunocytochemical staining was performed with the pan-macrophage marker CD68, M1 macrophage markers inducible nitric oxide synthase (iNOS) and chemokine (C-C motif) receptor 7 (CCR7), and M2 macrophage markers arginase 1 and CD163. Positively stained cells were counted.

RESULTS

Numbers of lymphocytes were increased in the CR group compared with the OA and Normal groups (P < .05). Numbers of CD68⁺ , CCR7⁺ , and iNOS⁺ cells in the CR and OA groups were increased compared with the Normal group (P < .05). Globally, the ratio of positively stained M1 polarized CD68⁺ cells to M2 polarized CD68⁺ cells was highest for the OA group (2.49), followed by the pCR (2.1), CR (1.63), and Normal (0.7) groups.

CONCLUSION

Polarization of synovial macrophages toward an M1 proinflammatory phenotype is an early event in the development of canine CR.

CLINICAL SIGNIFICANCE

M1 polarization in pCR stifles provides evidence of a possible role for macrophages in progressive development of cruciate ligament fiber damage. Lymphocytes may play a role in the synovitis found in CR joints. Our findings provide evidence that these cells are therapeutic targets.

Intraarticular injection of a Tin-117 m radiosynoviorthesis agent in normal canine elbows causes no adverse effects

This longitudinal prospective exploratory study used serial measurements in five dogs to evaluate safety and retention of a tin-117 m (^117m Sn) colloid after intra-articular injection in normal elbow joints. Each dog was deemed healthy based on physical examination, laboratory results, and radiographic evaluation of both elbows. While anesthetized, each received an MRI of both elbows, followed by fluorine-18 fluorodeoxyglucose positron emission tomography scans of both elbow joints and associated lymph nodes. Joint fluid (0.5-1.0 mL) was withdrawn aseptically from the left elbow joint, followed by intra-articular injection of ^117m Sn colloid (92.5 MBq; 1-1.5 ml). Post-injection assessments included blood counts, serum chemistry panels, urinalyses, radiographs, joint fluid analyses, MRI/positron emission tomography scans, scintigraphy, and biodistribution scans. On day 45-47, each dog was euthanized and a complete postmortem examination was performed. Tissue samples were submitted for histopathology and radioisotope retention studies. Left elbow joints were decalcified and sectioned for future autoradiography. Scintigraphy, 1 day after injection, indicated slight radioisotope escape from the joint to regional lymph nodes. Serial blood, urine, feces, and organ counts indicated >99.1% of the ^117m Sn activity was retained in the joint for 45-47 days. Radiation output levels were below patient release levels the day following injection. Maximum standard uptake value for the injected joint decreased. Joint fluid cytology was unchanged. No dog exhibited lameness during the study. Absence of joint damage and lack of systemic effects after injection of the ^117m Sn colloid in normal canine elbow joints indicate that this agent may be safely used for radiosynoviorthesis in dogs with osteoarthritis.

Inflammatory pattern of the infrapatellar fat pad in dogs with canine cruciate ligament disease

BACKGROUND

Despite the importance of inflammation during the pathogenesis of cranial cruciate ligament disease (CCLD) in dogs and despite the latest knowledge suggesting a significant role of adipose tissue in osteoarthritis, the infrapatellar fat pad (IFP) was up to now mostly disregarded in veterinary investigations. In the present study, the inflammatory activity of the IFP, the main adipose structure within the stifle joint, was thoroughly investigated to evaluate its potential impact in the pathogenesis of this common disease of our canine companions. Samples of IFP, subcutaneous adipose tissue (ScAT) of the thigh and synovial fluid in both diseased (n = 36) and healthy control (n = 23) dogs were tested for their immune cell composition but also for interleukins (IL-1β, IL-6, IL-8, IL-10), degradative enzymes (MMP-1, MMP-3, MMP-13, TIMP-2, iNOS) and adipokines (leptin and adiponectin). Characterization of the immune cell composition was ascertained by fluorescence activated cell sorting. Gene expression and protein release of the inflammatory markers was determined by real RT-qPCR and ELISA.

RESULTS

IFPs of dogs with CCLD had a significantly increased immune cell count with T cells (CD3) as the most abundant immune cells. T cells and macrophages (CD14) were significantly increased compared to healthy controls or corresponding ScAT. In addition, IFPs of dogs with CCLD demonstrated a significant increase on gene as well as protein level of multiple inflammatory indicators (IL-1β, IL-6, MMP-1, MMP-13) compared to the other tissues. TNFα was only increased on gene expression. Adipokine analysis showed higher secretion of adiponectin and lower leptin secretion in IFP from dogs with CCLD than from controls. In the synovial fluid from dogs with CCLD concentrations of IL-1β, MMP-1, MMP-13 as well as leptin were significantly increased compared to the synovial fluid from healthy control dogs.

CONCLUSIONS

The present study indicates that the IFP is a potential contributory factor in the pathogenesis of CCLD, due to its inflammatory phenotype and the proximity within the stifle joint. To determine the extent of this possible inter-relationship, further studies need to be undertaken.

Innovative, intra-articular, prosthetic technique for cranial cruciate ligament reconstruction in dogs: a cadaveric study

The purpose of this study was to describe and assess the feasibility of a new intra-articular approach in the treatment of cranial cruciate ligament deficiency in dogs using an artificial ligament and a new bone-anchor system. Twelve canine cadavers weighting 26 to 45 kg were used in this ex-vivo study. Special tibial and femoral screws, two helicoils, and a high resistance artificial fiber compose the implant. Surgery was performed using the cranio-lateral approach to the stifle joint. Helicoil and tibial screw, connected to the fiber, were inserted in the center of the tibial insertion area of the cranial cruciate ligament. The fiber was passed over-the-top, tensioned, and fixed to the femoral screw, previously inserted with the helicoil in the distal part of the femur. Surgery was completed in all the cases. Occasional problems found during the insertion of the helicoils and screws were resolved with simple procedures. Post-operative clinical assessment showed negative cranial drawer test, negative cranial tibial thrust, and normal range of motion. Radiographic evaluation showed an appropriate positioning of both tibial and femoral implants in all the cases. The results of the first surgical appraisal of this new technique are encouraging, although further studies are necessary to demonstrate the in vivo efficacy of this procedure.

Prior joint disease is associated with increased risk of periarticular histiocytic sarcoma in dogs

Periarticular histiocytic sarcoma (PAHS) is the most common synovial tumour in dogs and is characterized by aggressive local disease with a high rate of distant metastasis. Previously, an association between PAHS and prior joint disease has been demonstrated in the Bernese Mountain Dog breed and suggested in the Rottweiler. We hypothesized that this association would be present in other breeds and investigated this via a retrospective, case-controlled analysis. Cases were dogs diagnosed with PAHS of the stifle or elbow. Controls were age, breed and sex-matched dogs without a diagnosis of histiocytic sarcoma. Diagnosis of prior joint disease was determined based on review of medical records and direct veterinarian and owner communications. Data were evaluated using logistic regression, 2-sampled t tests, and chi-squared analysis. Our study population consisted of 28 cases and 46 controls, including Flat-Coated, Golden and Labrador Retrievers, Rottweilers, English Bulldogs, Shih Tzus, Australian Shepherds, Staffordshire Terriers and mixed breed dogs. Dogs with PAHS were more likely to have prior joint disease in the tumour-affected joint compared with the control population (odds ratio [OR] = 13.42, P < .0001, 95% confidence interval [CI] = 4.33-48.63). A total of 88.2% of dogs with stifle PAHS had prior joint disease in their tumour-affected joint, most commonly cranial cruciate ligament rupture. This study confirms that the previously noted association between prior joint disease and PAHS in Bernese Mountain Dogs also applies to other breeds. Additional studies are needed to further investigate for a causal relationship.

ERK2 and JNK1 contribute to TNF-α-induced IL-8 expression in synovial fibroblasts

Tumor necrosis factor α (TNF-α) induces the expression and secretion of interleukin 8 (IL-8), which contributes to synovitis in rheumatoid arthritis (RA). To elucidate the mechanism of the onset of RA, we used synovial fibroblasts without autoimmune inflammatory diseases and investigated MAPK signaling pathways in TNF-α-induced IL-8 expression. Synovial fibroblasts isolated from healthy dogs were characterized by flow cytometry, which were positive for the fibroblast markers CD29, CD44, and CD90 but negative for the hematopoietic cell markers CD14, CD34, CD45, and HLA-DR. TNF-α stimulated the secretion and mRNA expression of IL-8 in a time- and dose-dependent manner. ERK and JNK inhibitors attenuated TNF-α-induced IL-8 expression and secretion. TNF-α induced the phosphorylation of ERK1/2 and JNK1/2. TNF-α-induced IL-8 expression was attenuated both in ERK2- and JNK1-knockdown cells. TNF-α-induced ERK1/2 or JNK1/2 was observed in ERK2- or JNK1-knockdown cells, respectively, showing that there is no crosstalk between ERK2 and JNK1 pathways. These observations indicate that the individual activation of ERK2 and JNK1 pathways contributes to TNF-α-induced IL-8 expression in synovial fibroblasts, which appears to be involved in the progress in RA.

Differentiation potential of synoviocytes derived from joints with cranial cruciate ligament rupture and medial patella luxation in dogs

The objective of this study was to assess the differentiation capability of synoviocytes derived from dogs with inflammatory joint conditions. Cranial cruciate ligament ruptured (CCLr) (n=12) and medial patella luxated (MPL) (n=10) knee joints of the dogs were used to collect the synovial membrane (SM). Synoviocytes were enzymatically released from the SM and analyzed by flow cytometry for specific cellular markers (CD44 and CD90) of mesenchymal stem cells (MSCs), while doing histopathology from another part of SM sections. Under specific culture conditions, synoviocytes were forced to differentiate into chondrogenesis, adipogenesis, osteogenesis and osteoclastogenesis to investigate the multipotency. Upon treatments phenotypes of cell cultures were analyzed by histopathology and by semi-quantitative reverse transcriptase polymerase chain reaction for the expression of each differentiation marker genes. Although flow cytometry showing similar MSCs populations in CCLr and MPL synovium, synovial cells derived from CCLr showed higher multipotency compared to MPL-derived samples. Further, synovial changes such as vascularity, mononuclear cell infiltration and cellular hypertrophy were more pronounced in CCLr-derived synovial tissue than in MPL. Taken together, these findings suggested that the differentiation capability of SM-derived multipotent stem cells varies with inflammatory severity occurring in different joint conditions.

Evaluation of surface blood flow in intact and ruptured canine cruciate ligaments using laser Doppler flowmetry

OBJECTIVE

To evaluate the usefulness of laser Doppler flowmetry (LDF) to measure surface blood flow in canine cruciate ligaments, compare measurements in different sites of intact and partially ruptured canine cranial cruciate ligaments (CrCL) and intact caudal cruciate ligaments (CaCL), and investigate any association between surface blood flow in partially ruptured CrCL and synovitis or duration of clinical signs.

STUDY DESIGN

Case-controlled clinical study.

ANIMALS

Sixteen dogs with partially ruptured CrCL and five dogs with intact CrCL.

METHODS

Blood cell flux (BCF) readings during three measurement cycles using LDF at two sites in each ligament (mid-substance and the distal portion of the CrCL, and mid-substance and the proximal portion of the CaCL) were recorded. Synovial changes were graded grossly and histologically using the Osteoarthritis Research Society International histopathology scoring system.

RESULTS

The within-run coefficients of variation (CV) for a single BCF measurement cycle were 12.2% and 12.7% in the ruptured and intact CrCL groups, respectively. The between-run CV for three measurement cycles was 20.8% and 14.8%, respectively. The intraclass correlation coefficient (ICC, absolute agreement) was 0.66 for a single measurement cycle and 0.86 for the average of three cycles. No difference in average BCF readings was found between any two sites in either group, but BCF readings in both CrCL sites were significantly higher in the ruptured CrCL group than the intact CrCL group. No associations between BCF and synovial grades or duration of lameness were identified.

CONCLUSIONS

Laser Doppler flowmetry can be used to assess surface blood flow in intact and partially ruptured canine cruciate ligaments with acceptable precision. Using this method, surface blood flow appears greater in partially ruptured canine CrCL than intact CrCL. Further studies are required to determine if this is a sequela of trauma or synovitis.

Evaluating oxidative stress, serological- and haematological status of dogs suffering from osteoarthritis, after supplementing their diet with fish or corn oil

Background

Oxidative stress plays an important role in the pathogenesis of disease, and the antioxidant physiological effect of omega-3 from fish oil may lead to improvement of canine spontaneous osteoarthritis (OA).

Methods

In this prospective randomized, controlled, double-blinded study, we assessed haematological and biochemical parameters in dogs with OA following supplementation with either a concentrated omega-3 deep sea fish oil product or corn oil. Blood samples from 77 client-owned dogs diagnosed as having OA were taken before (baseline) and 16 weeks after having orally ingested 0.2 ml/Kg bodyweight/day of deep sea fish oil or corn oil. Circulating malondialdehyde (MDA), glutathione (GSH), non-transferrin bound iron (NTBI), free carnitine (Free-Car), 8-hydroxy-2-deoxyguanosine (8-OH-dG), and serum fatty acids, haemograms and serum biochemistry were evaluated. Differences within and between groups from baseline to end, were analysed using repeated samples T-test or Wilcoxon rank test and independent samples T-test or a Mann-Whitney test.

Results

Supplementation with fish oil resulted in a significant reduction from day 0 to day 112 in MDA (from 3.41 ± 1.34 to 2.43 ± 0.92 μmol/L; P < 0.001) and an elevation in Free-Car (from 18.18 ± 9.78 to 21.19 ± 9.58 μmol/L; P = 0.004) concentrations, whereas dogs receiving corn oil presented a reduction in MDA (from 3.41 ± 1.34 to 2.41 ± 1.01 μmol/L; P = 0.001) and NTBI (from −1.25 ± 2.17 to −2.31 ± 1.64 μmol/L; P = 0.002). Both groups showed increased (albeit not significantly) GSH and 8-OH-dG blood values. Dogs supplemented with fish oil had a significant reduction in the proportions of monocytes (from 3.84 ± 2.50 to 1.77 ± 1.92 %; P = 0.030) and basophils (from 1.47 ± 1.22 to 0.62 ± 0.62 %; P = 0.012), whereas a significant reduction in platelets counts (from 316.13 ± 93.83 to 288.41 ± 101.68 × 10⁹/L; P = 0.029), and an elevation in glucose (from 5.18 ± 0.37 to 5.32 ± 0.47 mmol/L; P = 0.041) and cholesterol (from 7.13 ± 1.62 to 7.73 ± 2.03 mmol/L; P = 0.011) measurements were observed in dogs receiving corn oil.

Conclusions

In canine OA, supplementation with deep sea fish oil improved diverse markers of oxidative status in the dogs studied. As corn oil also contributed to the reduction in certain oxidative markers, albeit to a lesser degree, there was no clear difference between the two oil groups. No clinical, haematological or biochemical evidence of side effects emerged related to supplementation of either oil. Although a shift in blood fatty acid values was apparent due to the type of nutraceutical product given to the dogs, corn oil seems not to be a good placebo.

Radiographic risk factors for contralateral rupture in dogs with unilateral cranial cruciate ligament rupture

Background

Complete cranial cruciate ligament rupture (CR) is a common cause of pelvic limb lameness in dogs. Dogs with unilateral CR often develop contralateral CR over time. Although radiographic signs of contralateral stifle joint osteoarthritis (OA) influence risk of subsequent contralateral CR, this risk has not been studied in detail.

Methodology/Principal Findings

We conducted a retrospective longitudinal cohort study of client-owned dogs with unilateral CR to determine how severity of radiographic stifle synovial effusion and osteophytosis influence risk of contralateral CR over time. Detailed survival analysis was performed for a cohort of 85 dogs after case filtering of an initial sample population of 513 dogs. This population was stratified based on radiographic severity of synovial effusion (graded on a scale of 0, 1, and 2) and severity of osteophytosis (graded on a scale of 0, 1, 2, and 3) of both index and contralateral stifle joints using a reproducible scoring method. Severity of osteophytosis in the index and contralateral stifles was significantly correlated. Rupture of the contralateral cranial cruciate ligament was significantly influenced by radiographic OA in both the index and contralateral stifles at diagnosis. Odds ratio for development of contralateral CR in dogs with severe contralateral radiographic stifle effusion was 13.4 at one year after diagnosis and 11.4 at two years. Odds ratio for development of contralateral CR in dogs with severe contralateral osteophytosis was 9.9 at one year after diagnosis. These odds ratios were associated with decreased time to contralateral CR. Breed, age, body weight, gender, and tibial plateau angle did not significantly influence time to contralateral CR.

Conclusion

Subsequent contralateral CR is significantly influenced by severity of radiographic stifle effusion and osteophytosis in the contralateral stifle, suggesting that synovitis and arthritic joint degeneration are significant factors in the disease mechanism underlying the arthropathy.

Genetic basis of cranial cruciate ligament rupture (CCLR) in dogs

Cranial Cruciate Ligament rupture (CCLR) is one of the most common forms of lameness in dogs and is analogous to rupture of the anterior cruciate ligament in humans, for which it can serve as a model. As there is a strong breed-related predisposition to CCLR in dogs, a study was undertaken to consider putative genetic components in susceptible dog breeds. A candidate gene, single nucleotide polymorphism (SNP) genotyping approach using MALDI-TOF mass spectrometry (Sequenom Ltd) was designed to investigate several CCLR-susceptible dog breeds and identify CCLR-associated genes/gene regions that may confer susceptibility or resistance. A meta-analysis was performed using the breed case/control candidate gene data to identify SNP associations that were common to the whole cohort of susceptible dogs. We identified SNPs in key genes involved in ligament strength, stability and extracellular matrix formation (COL5A1, COL5A2, COL1A1, COL3A1, COL11A1, COL24A1, FBN1, LOX, LTBP2) which were significantly associated with CCLR susceptibility across the dog breeds used in this study. These SNPs could have an involvement in CCLR due to a detrimental effect on ligament structure and strength. This is the first published candidate gene study that has revealed significant genetic associations with canine CCLR.

Arthroscopic assessment of stifle synovitis in dogs with cranial cruciate ligament rupture

Cranial cruciate ligament rupture (CR) is a degenerative condition in dogs that typically has a non-contact mechanism. Subsequent contralateral rupture often develops in dogs with unilateral CR. Synovitis severity is an important factor that promotes ligament degradation. Consequently, we wished to evaluate the utility of arthroscopy for assessment of stifle synovitis in dogs with CR. Herein, we report results of a prospective study of 27 dogs with unilateral CR and bilateral radiographic osteoarthritis. Arthroscopic images and synovial biopsies from the lateral and medial joint pouches were obtained bilaterally and graded for synovial hypertrophy, vascularity, and synovitis. Synovial tartrate-resistant acid phosphatase-positive (TRAP+) macrophages, CD3(+) T lymphocytes, Factor VIII+ blood vessels, and synovial intima thickness were quantified histologically and related to arthroscopic observations. Risk of subsequent contralateral CR was examined using survival analysis. We found that arthroscopic scores were increased in the index stifle, compared with the contralateral stifle (p<0.05). Numbers of CD3+ T lymphocytes (SR = 0.50, p<0.05) and TRAP+ cells in joint pouches (SR = 0.59, p<0.01) were correlated between joint pairs. Arthroscopic grading of vascularity and synovitis was correlated with number density of Factor VIII+ vessels (SR>0.34, p<0.05). Arthroscopic grading of villus hypertrophy correlated with numbers of CD3(+) T lymphocytes (SR = 0.34, p<0.05). Synovial intima thickness was correlated with arthroscopic hypertrophy, vascularity, and synovitis (SR>0.31, p<0.05). Strong intra-observer and moderate inter-observer agreement for arthroscopic scoring was found. Dog age and arthroscopic vascularity significantly influenced risk of contralateral CR over time. We conclude that arthroscopic grading of synovitis is a precise tool that correlates with histologic synovitis. Arthroscopy is useful for assessment of stifle synovitis in client-owned dogs, and could be used in longitudinal clinical trials to monitor synovial responses to disease-modifying therapy.

Hyaluronic acid concentrations in synovial fluid of dogs with different stages of osteoarthritis

To compare hyaluronic acid (HA) concentrations measured in synovial fluid (SF) of joints with different stages of canine secondary osteoarthritis (OA), clinical-orthopedic, radiographic, macroscopic intra-operative and SF findings of 49 joints were assessed. The sum of single findings was correlated to HA concentrations measured by a commercially available ELISA. Joints were categorized into three OA-groups: non-osteoarthritic, mildly osteoarthritic, and severely osteoarthritic. A significant negative correlation was found between severity of OA and HA concentrations (r=-0.696; P<0.001). Median values of HA concentrations decreased with increasing severity of the disease. Statistically significant differences in HA concentrations were observed between the OA-groups (P<0.001). Due to overlapping values between groups, it was concluded that synovial HA concentrations may only indicate a trend of osteoarthritic disease activity, but is not suitable for staging the disease.

Anterior cruciate ligament rupture in gouty arthritis

A 34-year-old male presented with right knee instability without any trauma. He had been diagnosed with right knee gouty arthritis 2 years prior. An arthroscopic examination revealed abundant calcific material deposited around the knee joint, including in the ACL tissue, and that the ACL was torn at the femoral attachment site. Treatment involved a synovectomy to remove calcific material, followed by an ACL reconstruction. Histology evaluation revealed gouty arthritis with the presence of tophi in the synovium, soft tissue, and ACL tissue. The case presented here indicates the possibility of pathologic rupture of the ACL associated with gouty tophus infiltration of that ligament. Level of evidence IV.

Minimally invasive synovium harvest for potential use in meniscal tissue engineering

Tissue engineering is being investigated as a means for treating avascular meniscal injury or total meniscal loss in human and veterinary patients. The purpose of this study was to determine if an arthroscopic tissue shaver can be used to collect viable synoviocytes for in vitro culture during therapeutic stifle arthroscopy, with the long term goal of producing autologous meniscal fibrocartilage for meniscal tissue engineering. Synovium was harvested arthroscopically from 13 dogs with naturally occurring cranial cruciate ligament deficiency and obtained from 5 dogs with patellar luxation via arthrotomy. Cells harvested via arthroscopy and arthrotomy were treated with a chondrogenic growth factor protocol and analyzed for meniscal-like matrix constituents including collagens type I, II, and glycosaminoglycans. Arthrotomy and Arthroscopic origin cells formed contracted tissues containing collagen I, II and small amounts of GAG. These surgical methods provide clinically relevant access to synoviocytes for potential use in meniscal tissue engineering.

Nitric oxide induces cell death in canine cruciate ligament cells by activation of tyrosine kinase and reactive oxygen species

Background

There is increasing evidence suggesting that development of progressive canine cranial cruciate ligament (CCL) rupture involves a gradual degeneration of the CCL itself, initiated by a combination of factors, ranging from mechanical to biochemical. To date, knowledge is lacking to what extent cruciate disease results from abnormal biomechanics on a normal ligament or contrary how far preliminary alterations of the ligament due to biochemical factors provoke abnormal biomechanics. This study is focused on nitric oxide (NO), one of the potential biochemical factors. The NO-donor sodium nitroprusside (SNP) has been used to study NO-dependent cell death in canine cranial and caudal cruciate ligament cells and to characterize signaling mechanisms during NO-stimulation.

Results

Sodium nitroprusside increased apoptotic cell death dose- and time-dependently in cruciate ligamentocytes. Cells from the CCL were more susceptible to apoptosis than CaCL cells. Caspase-3 processing in response to SNP was not detected. Testing major upstream and signal transducing pathways, NO-induced cruciate ligament cell death seemed to be mediated on different levels. Specific inhibition of tyrosine kinase significantly decreased SNP-induced cell death. Mitogen activated protein kinase ERK1 and 2 are activated upon NO and provide anti-apoptotic signals whereas p38 kinase and protein kinase C are not involved. Moreover, data showed that the inhibition reactive oxygen species (ROS) significantly reduced the level of cruciate ligament cell death.

Conclusions

Our data support the hypothesis that canine cruciate ligamentocytes, independently from their origin (CCL or CaCL) follow crucial signaling pathways involved in NO-induced cell death. However, the difference on susceptibility upon NO-mediated apoptosis seems to be dependent on other pathways than on these tested in the present study. In both, CCL and CaCL, the activation of the tyrosine kinase and the generation of ROS reveal important signaling pathways. In perspective, new efforts to prevent the development and progression of cruciate disease may include strategies aimed at reducing ROS.

Contralateral cruciate survival in dogs with unilateral non-contact cranial cruciate ligament rupture

BACKGROUND

Non-contact cranial cruciate ligament rupture (CrCLR) is an important cause of lameness in client-owned dogs and typically occurs without obvious injury. There is a high incidence of bilateral rupture at presentation or subsequent contralateral rupture in affected dogs. Although stifle synovitis increases risk of contralateral CrCLR, relatively little is known about risk factors for subsequent contralateral rupture, or whether therapeutic intervention may modify this risk.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a longitudinal study examining survival of the contralateral CrCL in client-owned dogs with unilateral CrCLR in a large baseline control population (n = 380), and a group of dogs that received disease-modifying therapy with arthroscopic lavage, intra-articular hyaluronic acid and oral doxycycline (n = 16), and were followed for one year. Follow-up in treated dogs included analysis of mobility, radiographic evaluation of stifle effusion and arthritis, and quantification of biomarkers of synovial inflammation. We found that median survival of the contralateral CrCL was 947 days. Increasing tibial plateau angle decreased contralateral ligament survival, whereas increasing age at diagnosis increased survival. Contralateral ligament survival was reduced in neutered dogs. Our disease-modifying therapy did not significantly influence contralateral ligament survival. Correlative analysis of clinical and biomarker variables with development of subsequent contralateral rupture revealed few significant results. However, increased expression of T lymphocyte-associated genes in the index unstable stifle at diagnosis was significantly related to development of subsequent non-contact contralateral CrCLR.

CONCLUSION

Subsequent contralateral CrCLR is common in client-owned dogs, with a median ligament survival time of 947 days. In this naturally occurring model of non-contact cruciate ligament rupture, cranial tibial translation is preceded by development of synovial inflammation. However, treatment with arthroscopic lavage, intra-articular hyaluronic acid and oral doxycycline does not significantly influence contralateral CrCL survival.

Radiographic quantitative assessment of caudal proximal tibial angulation in 100 dogs with cranial cruciate ligament rupture

OBJECTIVE

To evaluate inter- and intraobserver variability in the measurement of distal tibial axis/proximal tibial axis angle (DPA) from lateral radiographs of canine tibia in dogs with cranial cruciate ligament rupture (CCLR).

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Dogs (n=100) with cranial cruciate ligament rupture.

METHODS

Medical records of dogs diagnosed with CCLR were reviewed. In addition to signalment and TPA measurements, measured DPA (mDPA) was calculated for each lateral view of the tibia in each animal, twice, by 3 blinded observers. Subjective scoring of DPA (sDPA) was also recorded, twice, by 3 additional blinded observers from lateral views of the proximal half of the tibia in each dog. Inter- and intraobserver variability was measured by intraclass correlation coefficient (ICC) for each measurement. Correlation between mDPA and sDPA was also determined.

RESULTS

Median tibial plateau angle (TPA) of the subject population was 27.9° (range 18.8-41.3°; IQR: 25.5-30.75°). Mean ± SD mDPA was 6.50 ± 2.81° (confidence intervals [CI]: 5.94-7.06°; range 0-13.33°). There was no correlation between age and weight of dogs and the mDPA (P=.58 and .12). There was a moderate correlation between mDPA and TPA (r(2)=0.49, P<.0001). There was a moderate correlation between sDPA and mDPA (r(2)=0.27, P<.0001). Good inter- and intraobserver agreement was found in the measurement of mDPA.

CONCLUSION

mDPA is a reproducible measurement of caudal angulation of proximal tibia. Furthermore, mDPA of dogs with cranial cruciate ligament disease in this report are in concordance with previous reports.

Lymphocyte populations in joint tissues from dogs with inflammatory stifle arthritis and associated degenerative cranial cruciate ligament rupture

OBJECTIVE

To evaluate lymphocyte populations in stifle synovium and synovial fluid of dogs with degenerative cranial cruciate ligament rupture (CCLR).

STUDY DESIGN

Prospective clinical study.

ANIMALS

Dogs (n=25) with stifle arthritis and CCLR, 7 dogs with arthritis associated with cartilage degeneration (osteoarthritis [OA]), and 12 healthy Beagle dogs with intact CCL.

METHODS

Arthritis was graded radiographically in CCLR dogs. After collection of joint tissues, mononuclear cells were isolated and subsequently analyzed using flow cytometry for expression of CD3, CD4, CD8, and CD21.

RESULTS

The proportions of CD4(+) T helper lymphocytes, CD8(+) cytotoxic T lymphocytes, and CD3(+) CD4(-) CD8(-) T lymphocytes were increased in synovium from dogs with CCLR compared with synovium from healthy Beagle dogs (P<.05). The proportion of CD3(+) CD4(-) CD8(-) T lymphocytes in synovial fluid was increased in dogs with CCLR compared with dogs with OA (P<.05). In dogs with CCLR, the proportion of CD3(+) CD4(-) CD8(-) T lymphocytes in synovial fluid was inversely correlated with radiographic arthritis (S(R) =-0.68, P<.005).

CONCLUSION

Lymphocytic inflammation of stifle synovium and synovial fluid is an important feature of the CCLR arthropathy. Lymphocyte populations include T lymphocytes expressing CD4 and CD8, and CD3(+) CD4(-) CD8(-) T lymphocytes. Presence of CD3(+) CD4(-) CD8(-) T lymphocytes was associated with development of stifle synovitis. Further work is needed to fully identify the phenotype of these cells.

Synovitis in dogs with stable stifle joints and incipient cranial cruciate ligament rupture: a cross-sectional study

OBJECTIVE

To evaluate stifle joints of dogs for synovitis, before development of joint instability and cranial cruciate ligament rupture (CrCLR).

STUDY DESIGN

Cross-sectional study.

ANIMALS

Dogs (n = 16) with CrCLR and stable contralateral stifles; 10 control dogs with intact CrCL.

METHODS

Arthritis and tibial translation were graded radiographically. Synovitis severity and cruciate pathology were assessed arthroscopically. Presence of inflammatory cells in synovial membrane biopsies was scored histologically. CrCLR stifle pairs and control stifles were compared.

RESULTS

Radiographic evidence of arthritis, cranial tibial translation, and arthroscopic synovitis were increased in unstable stifles, when compared with stable contralateral stifles in CrCLR dogs (P < .05). Arthroscopic synovitis in both joints of CrCLR dogs was increased compared with controls, was correlated with radiographic arthritis (S(R) = 0.71, P < .05), and was present in all stable contralateral stifles. Arthroscopically, 75% of stable stifle joints had CrCL fiber disruption, which correlated with severity of synovitis (S(R) = 0.56, P < .05). Histologic evidence of synovitis was identified in all CrCLR dogs, but was only significantly correlated with arthroscopic observations in stable stifles (r(2) = 0.57, P < .005).

CONCLUSION

Synovitis is an early feature of the CrCLR arthropathy in dogs before development of joint instability clinically. Severity of synovitis is correlated with radiographic arthritis in joints with minimal to no clinically detectable CrCL damage.

Evaluation of in vitro growth factor treatments on fibrochondrogenesis by synovial membrane cells from osteoarthritic and nonosteoarthritic joints of dogs

OBJECTIVE

To determine the in vitro effects of selected growth factors on fibrochondrogenesis by synovial membrane cells from nonosteoarthritic (normal) and osteoarthritic joints of dogs.

ANIMALS

5 dogs with secondary osteoarthritis of shoulder or stifle joints and 6 dogs with normal joints.

PROCEDURES

Synovial membrane cells were harvested from normal and osteoarthritic joints and cultured in monolayer with or without (control) basic fibroblast growth factor, transforming growth factor-β1, and insulin-like growth factor-1. In the cultured cells, fibrochondrogenesis was measured by use of a real-time reverse transcriptase PCR assay to determine relative expressions of collagen I, collagen II, and aggrecan genes and of 3 genes involved in embryonic chondrogenesis: Sry-type homeobox protein-9 (SOX-9), frizzled-motif associated with bone development (Frzb), and regulator of G-protein signaling-10 (RGS-10). Tissue collagen content was measured via a hydroxyproline assay, and sulfated glycosaminoglycan content was measured via a 1,9-dimethylmethylene blue assay. Cellularity was determined via a double-stranded DNA assay. Immunohistochemical analysis for collagens I and II was also performed.

RESULTS

In vitro collagen synthesis was enhanced by growth factor stimulation. Although osteoarthritic-joint synoviocytes could undergo a fibrocartilage-like phenotypic shift, their production of collagenous extracellular matrix was less than that of normal-joint synoviocytes. Gene expressions of SOX-9 and RGS-10 were highest in the osteoarthritic-joint cells; Frzb expression was highest in growth factor treated cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Autogenous synovium may be a viable cell source for meniscal tissue engineering. Gene expressions of SOX-9 and RGS-10 may be potential future targets for in vitro enhancement of chondrogenesis.

Multivariate analysis of morphometric characteristics to evaluate risk factors for cranial cruciate ligament deficiency in Labrador retrievers

OBJECTIVES

To determine the combination of conformation characteristics of the pelvic limbs of Labrador Retrievers that best discriminates between limb at risk to develop cranial cruciate ligament (CCL) disease and limbs at low risk using radiographs, computerized tomography (CT) images, and dual-energy X-ray absorptiometry (DEXA).

STUDY DESIGN

Cross-sectional clinical study.

ANIMALS

Twelve clinically normal and 9 unilaterally CCL-deficient Labrador Retrievers.

METHODS

The pelvic limbs of normal dogs were considered as non-predisposed to CCL disease and the contralateral limbs of CCL-deficient dogs as predisposed. Conformation variables, obtained from femur and tibial radiographs, pelvic limb CT images and DEXA studies, of predisposed pelvic limbs were compared with the conformation variables from pelvic limbs of the low-risk group. An ROC curve analysis was used to assess the discriminating properties of conformation variables for several combinations.

RESULTS

We determined that a combination of tibial plateau angle (TPA) and femoral anteversion angle (FAA) measured on radiographs was optimal for discriminating predisposed and non-predisposed limbs for CCL disease in Labrador Retrievers.

CONCLUSIONS

Assessing predisposition to CCL disease with a combination of conformational measurements is better than using univariate parameters. In the future, TPA and FAA may be used to screen dogs suspected of being susceptible to CCL disease.

Cranial cruciate ligament disease in dogs: biology versus biomechanics

The stifle joint of dogs is an organ comprised of multiple tissue types that must work in concert to maintain joint health and function. Cruciate disease in dogs is caused by a spectrum of causal and risk factors that result in a final common pathway of abnormal biomechanics and abnormal biology causing osteoarthritis, or organ failure, of the stifle and the clinical signs of lameness, pain, and limb dysfunction. It is vital to understand the components of the biologic and biomechanical pathologies to improve our understanding of cruciate disease in dogs so that we can improve preventative, diagnostic, and therapeutic strategies for our canine patients.

Prevalence of lymphoplasmacytic synovitis in dogs with naturally occurring cranial cruciate ligament rupture

OBJECTIVE

To determine the prevalence of lymphoplasmacytic synovitis (LPS) in dogs with naturally occurring cranial cruciate ligament (CCL) rupture and compare clinical, radiographic, cytologic, and histologic findings in dogs with and without LPS.

DESIGN

Cross-sectional study.

ANIMALS

110 dogs with naturally occurring CCL rupture.

PROCEDURES

Histologic examination of synovial biopsy specimens obtained at the time of surgical treatment was used to identify dogs with LPS. Clinical, radiographic, cytologic, and histologic findings were compared between dogs with and without LPS.

RESULTS

56 (51%) dogs had histologic evidence of LPS. There were no significant differences in age, body weight, duration of lameness, severity of lameness, severity of radiographic signs of degenerative joint disease, extent of CCL rupture (partial vs complete), or gross appearance of the medial meniscus between dogs with and without LPS. Mean tibial plateau angle was significantly lower in dogs with LPS than in dogs without LPS, and dogs with LPS were significantly more likely to have neutrophils in their synovial fluid. Lymphocytes were seen in synovial fluid from a single dog with LPS.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that LPS was common in dogs with naturally occurring CCL rupture. However, only minor clinical, radiographic, cytologic, and histologic differences were identified between dogs with and without LPS.