Immunolocalization of cathepsin B in equine dyschondroplastic articular cartilage

A polyclonal antiserum raised in sheep against human cathepsin B was tested for specificity and cross-reactivity with the horse homologue by SDS-PAGE and Western blotting, prior to being used for immunolocalization of the enzyme in equine articular cartilage. In Western blots, the antiserum recognized the 30 kDa single chain and 25 kDa heavy chain of the mature enzyme in purified bovine cathepsin B, and corresponding bands at 32 and 27 kDa in equine chondrocyte and fibroblast lysates. This antiserum was then used to compare the expression and distribution of cathepsin B in normal and dyschondroplastic cartilage of young horses. In normal articular cartilage (n = 6 animals), significant amounts of enzyme were detected only in hypertrophic chondrocytes in the deep zone. The enzyme was intracellular, located in the lysosomal granules. No extracellular matrix staining was observed. Levels of cathepsin B were increased slightly above normal in the deep zone in age-matched dyschondroplastic cartilage (n = 5 animals). The most striking finding, however, was the abundance of the enzyme in chondrocyte clonal clusters associated with the lesions. Cathepsin B levels were low in chondrocytes isolated from normal cartilage (n = 6), but increased progressively during serial subculture, reaching a maximum at passage 5-6. In contrast, primary cultures of dyschondroplastic chondrocytes (n = 3) expressed abundant cathepsin B.

Matrix metalloproteinase activity in equine synovial fluid: influence of age, osteoarthritis, and osteochondrosis

OBJECTIVE

To investigate the influence of age, osteoarthritis (OA), and osteochondrosis (OC) on the matrix metalloproteinase (MMP) activity in the synovial fluid (SF) of equine joints.

METHODS

SF was collected from normal and osteoarthritic metacarpophalangeal joints (normal: 14 adult, 28 juvenile; OA: 22 adult). And from normal and osteochondrotic tarsocrural joints (5 months: 11 normal, 8 OC; 11 months: 7 normal, 6 OC). Subsequently, overall MMP activity was measured.

RESULTS

The level of active MMPs was almost twofold higher in SF from juvenile horses (age up to 11 months) than in SF from mature animals (4-30 years; p < 0.001). In juvenile horses MMP activity was higher in 5 month old foals than in 11 month old foals (p < 0.01). In adult horses MMP activity was independent of age. In OA joints the activity was nearly twice as high as in normal joints (p < 0.001). In OC joints MMP activity was not significantly different from normal, age matched, control joints.

CONCLUSIONS

MMP activity in SF from normal adult joints is not related to age. In juvenile joints MMP activity is significantly higher than activity in joints from adult animals. It is hypothesised that the gradual decrease in MMP activity with increasing age reflects the declining metabolic activity resulting from ceasing growth and the accompanying decrease in cartilage remodelling. The increased MMP activity in osteoarthritis joints most likely reflects matrix destruction. In osteochondrosis MMP mediated matrix degradation appears not to be different from normal joints.

Studies on growth cartilage in the horse and their application to aetiopathogenesis of dyschondroplasia (osteochondrosis)

The importance of osteochondrosis (dyschondroplasia) to the horse industry has been well documented since it was first recorded 50 years ago. The condition is known to be multifactorial in origin, arising from focal failure of endochondral ossification at predilection sites in articular/epiphyseal growth cartilage, but specific information on its aetiopathogenesis is sparse. This paper reviews the current knowledge of growth cartilage metabolism and the process of normal endochondral ossification in the horse. It highlights the localization of various protein products of chondrocytes and the differences in the zones of articular cartilage. In the early focal lesions (referred to as dyschondroplasia) there are alterations in the chondrocytes, extracellular matrix and some of the local protein products. The most obvious feature is an alteration in matrix metabolism which may be responsible for triggering a range of other factors leading to the development of a retained core of cartilage and a primary lesion of dyschondroplasia. Based on available evidence, a preliminary hypothesis for pathogenesis is presented. This suggests that there are a number of factors capable of initiating the condition. One of these involves high circulating insulin levels from high energy feeding which may affect chondrocyte maturation leading to altered matrix metabolism and faulty mineralization resulting in the formation of cartilage cores which characterize the condition. Further research to test this hypothesis is needed before there can be a rational basis for prophylaxis.

Investigation of osteochondrosis in grazing beef cattle

Severe lameness attributed to osteochondrosis is described in an extensively managed Brahman herd grazing on improved native pasture. Clinical signs were observed in five animals, three of which were necropsied. The most prominent lesions were in the elbow and stifle joints. There were multiple fissuring and ulceration of thickened articular cartilage with numerous osteochondral bodies present in the joint spaces. All affected animals were entire males sharing a common ancestral sire. Inheritance and gender were suspected to be contributing factors in the development of the disease.

Enthesopathy of the radial tuberosity in two thoroughbred racehorses

Two cases of enthesopathy of the radial tuberosity in Thoroughbred racehorses are described. Soft X-ray pictures revealed separated bony fragments at the anterior aspect of the radial tuberosity, resembling the lesions of Osgood-Schlatter disease in children. Osgood-Schlatter lesions result from detachment of a portion of the apophysis of the tibial tuberosity. However, in the affected horses, the detached bony fragments consisted of cortical bone tissue composed of trabeculae with osteons similar to lamellar bone, the main component of the radial tuberosity. Tendon fibrils were inserted into the anterior parts of the detached fragments, and scar tissue filled the gap between the posterior part of the fragments and the radial tuberosity. The bone fragments may have originated from an avulsion fracture at the site of attachment of the tendinous portion of the biceps brachii muscle to the bone tissue of the radial tuberosity, a site at which high-tensile force is repeatedly exerted by muscle contraction.

Diagnostic imaging of osteochondrosis

This article includes imaging of the glenohumeral (shoulder), elbow, stifle, and tarsal joints. The imaging modalities discussed are survey radiography, contrast arthrography, linear tomography, ultrasound, computed tomography, scintigraphy and magnetic resonance. Survey radiography is the first choice imaging modality for diagnosing osteochondrosis dissecans in dogs. In cases where survey radiography fail to demonstrate a lesion other modalities such as scintigraphy, linear tomography, computed tomography, and magnetic resonance may be helpful. Survey radiography, contrast arthrography, computed tomography, and magnetic resonance may also provide additional information contributing to early diagnosis and treatment.

Diagnostic and surgical arthroscopy in osteochondrosis lesions

In the dog, as in man and the horse, arthroscopy has an important role in treatment of joint disease. In the shoulder, elbow, and stifle joints, surgical arthroscopy can and should replace the classical surgical methods of treating osteochondrosis lesions. In elbow and tarsocrural joint disorders, the diagnostic potentials of arthroscopy are evident. With the established techniques, not only can the lesions be diagnosed with accuracy, but they can also be treated within the same procedure, making arthroscopy the treatment of choice to deal with osteochondrosis lesions. Without a doubt, arthroscopy will play an important role in the understanding of the etiopathology of different joint diseases, especially within the elbow joint, where so many questions remain unresolved. The advantages of arthroscopy in the diagnosis and treatment of osteochondrosis have also encouraged other veterinary surgeons to adopt the technique. In the developmental stage of arthroscopy in the dog, a frequently expressed comment was that arthrotomy was as valuable and as easy (or easier) to perform as arthroscopy. Now that the advantages of arthroscopy have been demonstrated, the skepticism has changed into enthusiasm. The same evolution is noted with arthroscopy in both man and the horse.

Nutrition and osteochondrosis

Developmental orthopedic disease is a group of musculoskeletal disorders that occur in growing animals (most commonly fast growing, large breed dogs). Osteochondritis dissecans and canine hip dysplasia are the overwhelming majority of the diagnoses in those musculoskeletal problems with a possible nutritional-related etiology. Nutritional management alone will not completely control osteochondrosis or any of the developmental bone diseases. However, osteochondrosis and other developmental orthopedic diseases can be influenced during growth by feeding technique and nutrient profile. Dietary deficiencies are of minimal concern in this age of commercial foods specifically prepared for young, growing dogs. The potential for harm is in overnutrition from excess consumption and over supplementation.

The pathophysiology of osteochondrosis

Osteochondrosis is a disorder of epiphyseal cartilage about which there is considerable confusion in the literature. We believe that this is due to the fact that osteochondrosis has been studied in the chronic stage when the lesions are morphologically complicated and the initial causative insult is impossible to determine. The etiology of osteochondrosis appears to be multifactorial, with trauma, hereditary factors and rapid growth, nutritional factors, and ischemia all having a role in its pathogenesis. Although predilection sites are variable among species, the morphology of the early lesions is strikingly similar, strongly suggesting that the pathogenesis of osteochondrosis is the same, regardless of the species affected. Based on recent studies in pigs and horses, and supported by observations in dogs and cattle, we believe that local ischemia secondary to defects in cartilage canal blood supply is a key factor in the initiation of lesions of osteochondrosis and explains many of the features of this disease. Local ischemia to the epiphyseal cartilage of the articular-epiphyseal cartilage complex leads to the formation of highly vulnerable zones of necrotic epiphyseal cartilage which later cause a delay in endochondral ossification, with extension of necrotic cartilage into the subchondral bone. Trauma, whether major or minor, to the overlying articular cartilage leads to cartilage cleft formation, clinical signs of pain and lameness, and other chronic sequelae. Studies aimed at further elucidating the pathogenesis of osteochondrosis should attempt to determine the cause of the vascular defect and whether or not it may be modified by experimental manipulations.

Arthroscopic removal of palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarso-phalangeal joints of standardbred trotters--outcome and possible genetic background to POF

A clinical material of 133 Standardbred horses with palmar/plantar osteochondral fragments (POF) in the metacarpo- and metatarsophalangeal joints were studied. All horses had their fragments removed with arthroscopic surgery. 102 of the horses were 3 years old or younger when surgery was performed. Anatomical localisations of the fragments were in agreement with earlier reports. There was no statistical significant difference in month of birth in the POF--group compared to the total population. Eighty % of the horses that had raced before surgery came back to racing. The racing performance relative to their contemporaries remained the same after the POF operation. 65% of the horses that had not raced before surgery raced after the operation. The breeding index BLUP (Best Linear Unbiased Prediction) was used to evaluate if the POF-horses differed genetically in racing ability from the total population. The average BLUP value of the POF group was 103.4 (+/- 0.65), while the mean BLUP value of the total population was 98.9. This difference was highly significant and indicated that these POF horses belonged to a selected group. A homogeneity test of allele frequencies in blood type systems was performed to evaluate if any genetic difference was persistent between POF horses compared to the total population. The statistical analysis of gene frequencies for alleles in blood type systems indicated a genetic discrimination in blood type systems D and Tf.

Osteochondrosis of the femur

Osteochondrosis can occur in the stifle joint(s) of young, rapidly growing large breeds of dogs. Although not as common as osteochondrosis of the shoulder, elbow, and hock joints, the osteochondral defect in the femoral condyle(s) and stifle joint fragment can cause a clinically apparent lameness. Radiography is beneficial in identifying the lesion(s), and surgical therapy is useful in restoring limb function.

Osteochondrosis of the canine tibiotarsal joint

This article reviews previous literature and current conclusions regarding osteochondrosis dissecans in the canine tarsus since it was first reported only 20 years ago. Breed, signalment, and clinical characteristics can greatly aid the clinician in suspicion of this condition. Specific radiographic techniques for confirmation of osteochondrosis are discussed. Treatment options, expectations, and specific surgical approaches are reviewed.

Historical perspectives of osteochondrosis

A famous historian, Toynbee, wrote that history was based on challenge and response. Certainly the development of our understanding of osteochondrosis dissecans in the dog fits this description. From the first indications of the disease to our present understanding took about 60 years. The times were right, for during this period improvements in anesthesiology, radiology, and surgery, along with the demands of clients coupled with the presence of skilled trained investigators and sharp practitioners, brought about a continually increasing mass of information about a new disease entity. It is proper for us to give credit to those gifted individuals who patiently worked to unravel each bit of information. Our current challenge is that much more remains to be done.

Clinical and radiographic findings, treatment, and outcome in cattle with osteochondrosis: 29 cases (1986-1996)

OBJECTIVE

To summarize the radiographic and clinical findings, treatment, and outcome in cattle with osteochondrosis diagnosed radiographically.

DESIGN

Retrospective case series.

SAMPLE POPULATION

29 cattle with radiographic evidence of osteochondrosis.

PROCEDURES

Medical records were reviewed, and owners or referring veterinarians were contacted for outcome assessment. Data were analyzed for potential interactions between osteochondrosis classification (osteochondritis dessicans vs subchondral cyst-like lesions), clinical and radiographic findings, treatment, and outcome, using Fisher's exact test and descriptive statistics.

RESULTS

Osteochondrosis was associated with young, male, purebred cattle, clinical evidence of lameness, and radiographic evidence of concurrent degenerative joint disease. Osteochondritis dissecans and subchondral cyst-like lesions had similar clinical findings and outcomes but varied significantly in their radiographic distribution among joints. Osteochondrosis often manifests clinically as a unilateral condition, but bilateral lesions were often found (88%) when limbs were radiographically examined. Cattle managed conservatively tended to be culled (within 6 months of diagnosis because of lameness) more often than those managed surgically, despite the lack of treatment bias.

CLINICAL IMPLICATIONS

Osteochondrosis in cattle is often associated with lameness or degenerative joint disease. Conservative management does not result in a favorable clinical prognosis for long-term, lameness-free survival, and more studies need to be completed to evaluate the efficacy of surgical treatment of osteochondrosis in cattle.

Avulsion of the tibial tuberosity in a litter of greyhound puppies

Avulsion of the tibial tuberosity was diagnosed in six of seven greyhound littermates aged five and a half months. The puppies showed hindlimb lameness of varying severity. Radiological assessment of affected stifle joints revealed partial or complete avulsion of the tibial tuberosities. In four puppies the lesions were bilateral. Euthanasia of the two most severely affected puppies was performed; the changes observed on histopathological examination of their cranioproximal tibiae suggested that the underlying lesion was that of osteochondrosis. A hereditary predisposition in greyhounds to osteochondrosis of the physis between the apophysis and the cranioproximal tibial diaphysis is postulated.

Superficial and deep defects in dyschondroplastic and degenerated pig articular cartilage

Normal and pathological (osteochondrotic and osteoarthrotic) pig articular cartilages from medial humeral and femoral condyles were studied by scanning electron microscopy. The pathological cartilages showed primitive osteochondrotic lesions with progressive aspects according to the severity of the pathology (flaking, fibrillation and cracks) and other superficial changes (micro-undulation, micro-fissurations, clefts) that appeared to be a consequence of the action of intense mechanical stresses such as shearing forces, compressive deformation, friction of the articular surfaces. The observation of deep lesions such as cracks and fractures at or near the interface between cartilage and calcified zone, frequently observed both at medial condyle and at intercondylar crista of the humerus, often evolving in cartilagineous flaps, were related to excessive tangential and shear forces induced by an abnormal articular topography resulting in joint instability. This pathological joint dynamic could be also worsened by an anomalous leg conformation (cross-legs) and/or by an increased occurrence of environmental micro- and macrotrauma (impact loading). Also in this case, the frequency and severity of the lesions can be increased if the deep layer is affected by osteo-chondrotic lesions. The results stress the pathogenetic importance of mechanical load in initiating and worsening the articular lesions in pigs; they also suggest that the resulting alterations can be influenced by a pre-existing different maturity or pathological condition of the cartilage.

Biochemical, histochemical, and immunohistochemical characterization of distal tibial osteochondrosis in horses

OBJECTIVE

To compare the biochemical, histochemical, and immunohistochemical profiles of articular cartilage from horses with naturally acquired distal tibial osteochondrosis (OC) with cartilage from a similar location in clinically normal horses.

ANIMALS

9 affected horses (group 1, 16 OC lesions) and 4 control horses (group 2, 8 normal osteochondral specimens).

PROCEDURE

OC specimens were collected during arthroscopic removal of the fragment, and control specimens were collected by aseptic osteotomy. Uronic acid, total protein, total glycosaminoglycan (GAG), chondroitin sulfate (CS), and keratan sulfate (KS) contents were determined. Histomorphologic, histochemical, and immunohistochemical examinations were performed on specimens after snap freezing at -80 C and cryosectioning. Monoclonal antibodies (MAB) 3B3 and 5D4 were applied for location of epitopes of CS and KS, respectively.

RESULTS

OC lesions had significantly lower quantity of uronic acid, total GAG, and CS, compared with normal cartilage. OC cartilage had significantly less intense staining with toluidine blue, along with irregular cellularity and tidemark characteristics, compared with normal cartilage. Monoclonal antibodies 3B3 and 5D4 stained OC cartilage, whereas MAB 5D4 did not stain control cartilage. Additionally, MAB 3B3 and 5D4 stained the fibrous tissue that was found firmly attached to the OC lesion located between the parent distal portion of the tibia and OC fragment.

CONCLUSION

OC cartilage lesions of the distal intermediate ridge of the tibia in horses are biochemically, histochemically, and immunohistochemically distinct from normal cartilage from the same location. Results may reflect the inability of the chondrocyte of the developing joint to alter matrix components that would allow proper maturation and differentiation into bone.

The significance of routine radiographic findings with respect to subsequent racing performance and longevity in standardbred trotters

A retrospective cohort study was made of the racing performance of trotters which had been subjected routinely to radiography before they started training and racing. Sixty-one per cent (148) of the 243 horses, foaled in 3 consecutive years, had one or more abnormal findings categorised into 5 relevant groups based on radiography, of which osteochondrosis (OCD) was the most specific diagnosis. Parameters used to reflect racing performance were: proportion of horses starting in races, number of starts per year, earnings per year, earnings per start and racing longevity. No significant association between the presence or type of radiological abnormalities and the subsequent performance and longevity could be found. Horses with multiple lesions, however, had a tendency to lower earnings and poorer survival than horses with single lesions.