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)
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
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
(rs = 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
(rs = –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)
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,
Objective—To investigate interglobular domain (IGD)
cleavage of aggrecan in dogs with naturally developing
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
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
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)
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
Animals—12 clinically normal dogs (6 Greyhounds
and 6 Labrador Retrievers) with no history of hind
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
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
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)
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.