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Abstract

Objective—To assess different components of the extracellular matrix with regard to their thermal properties, composition, and turnover in ruptured cranial cruciate ligaments (CCLs) of dogs, compared with components of intact CCLs from a breed predisposed to CCL failure.

Sample Population—Ruptured CCLs obtained from 8 dogs of breeds predisposed to ruptured CCLs and intact CCLs from 12 cadaveric Labrador Retrievers.

Procedure—Ruptured and intact CCLs were analyzed for water content; collagen content and collagen cross-links were evaluated via hydroxyproline and amino-acid analyses, respectively. Glycosaminoglycan (GAG) content was analyzed via dimethylmethylene blue and uronic acid assays. Matrix metalloproteinases (MMPs)-2 and -9 and the tissue inhibitors of metalloproteinases (TIMPs)-1 and -2 were detected via gelatin SDS-PAGE zymography and reverse gelatin zymography. Thermal analysis of ligaments was performed by use of differential scanning calorimetry.

Results—Ruptured CCLs had significantly higher lamounts of immature cross-links, total and sulfated GAGs, and water content, compared with that of the intact ligaments. Compared with intact CCLs, concentration of pro–MMP-2 was significantly higher in ruptured CCLs; the maximum temperature of collagen denaturation was significantly lower in the ruptured CCLs.

Conclusions and Clinical Relevance—The extracellular matrix of ruptured CCLs had an increased matrix turnover indicated by increased collagen and GAG synthesis, compared with that of intact CCLs. Although the extracellular matrix changes may have occurred before ligament rupture, it is possible that these observed changes may be part of a reparative process after rupture. (Am J Vet Res 2004;65:1136–1141)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate the biomechanical behavior of the lumbosacral disk under compressive load in dogs, using pressure profilometry, and to investigate the relationship between pressure profile features and background and disease variables.

Sample Population—23 lumbosacral disks and adjacent vertebrae harvested from medium and large breed dogs.

Procedure—A 1.3-mm unidirectional needle-mounted pressure transducer was inserted into the disk in a ventral-to-dorsal manner while the disk was loaded in compression by a materials testing machine. Withdrawal of the transducer resulted in a pressure profile for cranial and lateral stress. Pressure profiles were analyzed, and relationships to age and gross evidence of degeneration were investigated.

Results—There was a moderate positive correlation between age and degree of nuclear degeneration (r s = 0.420, P = 0.046), but no relationship between age and mean nuclear pressure was detected. Mean nuclear pressure correlated negatively with severity of degenerative changes in the nucleus pulposus. Receiver operator characteristic curves to evaluate mean nuclear pressure as a diagnostic test for nuclear degeneration revealed a sensitivity and specificity of 82 and 83%, respectively. In addition, age was moderately correlated with the magnitude of stress peaks (r s = –0.571, P = 0.004). Stress peaks were not related to the severity of nuclear degeneration.

Conclusions and Clinical Relevance—Determination of the mean nuclear pressure by disk profilometry provides information on the severity of lumbosacral disk degeneration with a high degree of sensitivity and specificity. The magnitude of single stress peaks within the dorsal annulus fibrosus is correlated with age and may not necessarily reflect advancing degeneration. (Am J Vet Res 2001;62:1734–1739)

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in American Journal of Veterinary Research

Osteoarthritis is a condition characterized by the destruction of articular cartilage, resulting in pain and dysfunction of the affected joint. Over time, articular cartilage degenerates with fibrillation, fissures, ulceration, and eventual full-thickness loss of the joint surface. Outgrowths of bone at the margin of the affected joints appear in later life, which cause joint pain and stiffness. It is now recognized that osteoarthritis is probably the result of a group of overlapping distinct diseases, which may have different etiologies but similar biological, morphologic, and clinical outcomes. Additionally, it should be appreciated that the disease processes can involve the entire joint,

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate interglobular domain (IGD) cleavage of aggrecan in dogs with naturally developing osteoarthritis (OA).

Sample Population—Samples of synovial fluid (SF) obtained from 3 cubital (elbow) joints and 3 stifle joints of 4 clinically normal dogs, 24 elbow joints of 12 dogs with early-stage OA, 8 stifle joints of 5 dogs with early-stage OA, and 10 stifle joints of 9 dogs with latestage OA.

Procedure—Fractions of SF were assayed for total glycosaminoglycan (GAG) content and also subjected to western blot analysis by use of monoclonal antibodies against neoepitopes generated by cleavage of the IGD of the aggrecan protein core by matrix metalloproteinase (MMP; BC-14) and aggrecanase (BC-3).

Results—Total GAG content of SF from joints of clinically normal dogs did not differ from that of dogs with early-stage OA. The GAG content of SF from joints of dogs with late-stage OA was significantly lower, compared with GAG content for other SF samples. Aggrecanase-generated fragments were detected in SF from all groups but not in all samples. Matrix metalloproteinase– generated fragments were not detected in any SF samples. In early-stage OA, high-molecularweight aggrecanase-generated aggrecan catabolites were evident.

Conclusions and Clinical Relevance—GAG content of SF obtained from dogs with late-stage OA is significantly decreased, suggesting proteoglycan depletion of cartilage. Aggrecanases, but not MMPs, are the major proteolytic enzymes responsible for IGD cleavage of aggrecan in canine joints. Analyses of SF samples to detect aggrecanase-generated catabolites may provide an early biomarker for discriminating early- and latestage OA in dogs. (Am J Vet Res 2005;66:1679–1685)

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in American Journal of Veterinary Research

Abstract

Objective—To quantify angular excursions; net joint moments; and powers across the stifle, tarsal, and metatarsophalangeal (MTP) joints in Labrador Retrievers and Greyhounds and investigate differences in joint mechanics between these 2 breeds of dogs.

Animals—12 clinically normal dogs (6 Greyhounds and 6 Labrador Retrievers) with no history of hind limb lameness.

Procedure—Small retroreflective markers were applied to the skin over the pelvic limb joints, and a 4- camera kinematic system captured data at 200 Hz in tandem with force platform data while the dogs trotted on a runway. Breed-specific morphometric data were combined with kinematic and force data in an inverse-dynamics solution for stance-phase net joint moments and powers at the stifle, tarsal, and MTP joints.

Results—There were gross differences in kinematic patterns between Greyhounds and Labradors. At the stifle and tarsal joints, moment and power patterns were similar in shape, but amplitudes were larger for the Greyhounds. The MTP joint was a net absorber of energy, and this was greater in the Greyhounds. Greyhounds had a positive phase across the stifle, tarsal, and MTP joints at the end of stance for an active push-off, whereas for the Labrador Retrievers, the only positive phase was across the tarsus, and this was small, compared with values for the Greyhounds.

Conclusions and Clinical Relevance—Gross differences in pelvic limb mechanics are evident between Greyhounds and Labrador Retrievers. Joint kinetics in specific dogs should be compared against breed-specific patterns. (Am J Vet Res 2005;66:1563–1571)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To assess 2 methods of RNA purification by use of different quality metrics and identify the most useful metric for quality assessment of RNA extracted from articular cartilage from dogs with osteoarthritis.

Sample Population—40 articular cartilage specimens from the femoral heads of 3 clinically normal dogs and 37 dogs with osteoarthritis.

Procedures—RNA was extracted from articular cartilage by 2 purification methods. Quality metrics of each sample were determined and recorded by use of a UV spectrophotometer (Spec I; to determine the 260 to 280 nm absorbance ratio [A260:A280 ratio]), a second UV spectrophotometer (Spec II; to determine A260:A280 and A260:A230 absorbance ratios), and a microfluidic capillary electrophoresis analyzer (to determine the ribosomal peak ratio [RR], degradation factor [DF], and RNA integrity number [RIN]). The RNA was extracted from affected (osteoarthritic) articular cartilage and assessed with the same quality metrics. Metric results were compared with visual analysis of the electropherogram to determine the most useful RNA quality metric.

Results—No differences in methods of RNA purification were determined by use of quality metrics. The RNA extracted from unaffected (normal) cartilage was of higher quality than that extracted from affected (osteoarthritic) cartilage, as determined by the RIN and Spec II A260:A230 ratio. The RIN and RR were the most sensitive metrics for determining RNA quality, whereas the DF was most specific. A significant proportion (32%) of RNA extracted from osteoarthritic articular cartilage specimens was determined as being of low quality.

Conclusions and Clinical Relevance—No single metric provided a completely sensitive and specific assessment of the quality of RNA recovered from articular cartilage.

Full access
in American Journal of Veterinary Research