Objective—To determine the effects of exercise at an early age on tissues in the metacarpophalangeal joints of horses.
Animals—Twelve 18-month-old horses.
Procedures—All horses were pasture reared, but 6 horses had additional exercise starting at 3 weeks of age until 18 months of age. At that time, computed tomography, articular cartilage metabolism evaluation, and histologic assessments of synovial membrane, articular cartilage, and subchondral bone were performed.
Results—Exercised horses had fewer gross lesions, less articular cartilage matrix staining in the dorsal aspect of the condyle, greater bone fraction in the dorsolateral aspect of the condyle, and higher bone formation rate, compared with nonexercised horses.
Conclusions and Clinical Relevance—Exercise at a young age may be protective to joints, although more research is needed to characterize changes in articular cartilage matrix. Results suggested that exercise can be safely imposed at an early age.
Objective—To determine effects of interleukin (IL)-1β and glucocorticoids on total glycosaminoglycan (GAG) loss and aggrecanase-mediated matrix degradation in equine cartilage.
Sample Population—Cartilage from 24 equine cadavers free of sepsis and musculoskeletal disease.
Procedures—Effects of IL-1β, IL-1β with glucocorticoids (dexamethasone and triamcinolone, 10−6 and 10−7M), and glucocorticoids alone on degradation of equine articular and nasal cartilage explants were assessed by measuring GAG release in media and GAG content in cartilage. Aggrecanase-mediated cleavage within the interglobular domain at Glu373-Ala374 was evaluated via western blot analysis and ELISAs. Steady-state mRNA concentrations of matrix metalloproteinase (MMP)-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4, and ADAMTS5 were assessed by use of real-time reverse transcriptase PCR assay (cartilage explants) and northern blot analysis (cell culture).
Results—IL-1β increased GAG release and aggrecanase activity (11-fold). The MMP-3, MMP-13, and ADAMTS4 mRNA were upregulated with IL-1β, whereas ADAMTS5 mRNA was increased (13-fold), but significantly less than ADAMTS4 mRNA (27-fold), suggesting a role for both ADAMTS4 and ADAMTS5 in degradation of cytokine-stimulated cartilage. Despite downregulation of MMP-3 and MMP-13 mRNA, glucocorticoids did not alter GAG degradation. A further increase in aggrecanase activity was detected with ELISAs and western blot analysis, whereas ADAMTS4 mRNA was downregulated and ADAMTS5 mRNA was maintained or upregulated.
Conclusions and Clinical Relevance—MMP-3, MMP-13, and ADAMTS4 were regulated differently than ADAMTS5. Glucocorticoids increased aggrecanase activity despite down-regulation of ADAMTS4 mRNA, suggesting a major role of ADAMTS5. Effects of glucocorticoids on aggrecanase activity have important implications in terms of treatment.
Objective—To determine whether triamcinolone acetonide diffuses from the distal interphalangeal joint (DIPJ) to the navicular bursa, diffusion is direct or systemic, and addition of sodium hyaluronan has an effect on diffusion in horses.
Animals—11 adult horses without forelimb lameness.
Procedures—1 randomly chosen forelimb DIPJ of each horse received an injection of 10 mg of triamcinolone acetonide plus 20 mg of sodium hyaluronan (group 1), and the contralateral forelimb DIPJ received an injection of 10 mg of triamcinolone acetonide plus 2 mL of lactated Ringer's solution (group 2). Synovial fluid samples were taken from both forelimb navicular bursae and 1 hind limb navicular bursa (systemic control group) at 6 hours. Triamcinolone acetonide concentrations in synovial fluid were quantified by use of high-performance liquid chromatography plus tandem mass spectrometry. Data were logarithmically transformed, and contrast analysis was performed on the 3 groups.
Results—Triamcinolone acetonide was detected in navicular bursal samples in all groups. Groups 1 and 2 had significantly greater concentrations of triamcinolone acetonide than the systemic control group. There was no significant difference between groups 1 and 2.
Conclusions and Clinical Relevance—Triamcinolone acetonide diffused directly from the DIPJ into the navicular bursa in clinically normal horses, and diffusion was not affected by addition of hyaluronan. Injection into the DIPJ with triamcinolone acetonide or a triamcinolone acetonide–hyaluronan combination can potentially be used for treatment of navicular syndrome, but further studies are needed to determine whether triamcinolone acetonide diffuses similarly in horses with navicular syndrome.
Objective—To develop a scoring system for histopathologic changes in the synovium of tarsocrural joints (TCJs) of horses with osteochondritis dissecans (OCD) and to test for association between histopathologic changes and joint effusion or lameness.
Animals—93 horses with OCD of the intermediate ridge of the tibia of 1 or both TCJs (134 joints) and 38 control horses without disease of TCJs (38 joints).
Procedures—For OCD-affected horses, pretreatment lameness, TCJ effusion, and results of pelvic limb flexion test were scored. Synovial biopsy specimens were obtained from TCJs of OCD-affected horses during arthroscopy, and similar postmortem tissue specimens were obtained from control horses through a small arthrotomy. Histologic signs of synovitis in 172 biopsy specimens were scored by 2 pathologists (A and B) by use of 2 criteria: synoviocyte proliferation and cellular infiltration.
Results—Analysis of scoring revealed good to very good intraobserver agreement within pathologist A (weighted kappa [WK], 0.76 to 0.81), and moderate to good agreement within pathologist B (WK, 0.56 to 0.63). Interobserver agreement for synoviocyte proliferation (WK, 0.34 to 0.52) and cellular infiltration (WK, 0.38 to 0.48) scores was fair to moderate. Joint effusion and synoviocyte proliferation were significantly associated, as were joint effusion and cellular infiltration. There was no association between histopathologic changes and the other clinical signs evaluated.
Conclusions and Clinical Relevance—The scoring system was helpful for evaluating synovial inflammation caused by OCD of the intermediate ridge of the tibia in horses. Histopathologic signs of synovial inflammation were associated with effusion but not with lameness.
Objective—To quantify bone mineral density (BMD) in the medial coronoid process (MCP) of dogs with and without fragmented medial coronoid processes (FMCPs) by use of dualenergy x-ray absorptiometry.
Sample Population—50 osteochondral samples from 31 dogs that underwent subtotal coronoid ostectomy for unilateral or bilateral FMCP and 10 control osteochondral samples of the MCP collected from forelimbs of 5 cadaveric Greyhounds.
Procedures—Each sample was mounted in proximodistal and mediolateral orientations for BMD determinations via dual-energy x-ray absorptiometry, and area-of-interest data (0.03-cm2 increments) were obtained. Values of BMD were compared between left and right limb control samples, between control and FMCP samples, and between axial and abaxial regions of the control or FMCP samples.
Results—The BMD in control and FMCP samples in both proximodistal and mediolateral orientations differed significantly. Mean BMD throughout the MCP was decreased in FMCP samples, compared with control sample findings. In both control and FMCP samples, BMD of the abaxial half of the MCP was 50% higher than that of the axial portion.
Conclusions and Clinical Relevance—The similar pattern of BMD in osteochondral samples of the MCP in dogs with and without FMCP indicated that the MCP was eccentrically loaded during weight bearing. Topographic variation in BMD in the MCP, and hence tolerance to compressive loading, suggested that the abaxial portion of the MCP in dogs was more resistant to compressive load than was the axial edge. This difference may predispose the coronoid process to microcrack formation and fragmentation at that juxtaposition.
Objective—To investigate the effects of exercise and osteochondral injury on concentrations of carboxy-terminal telopeptide fragments of type II collagen (CTX-II) in synovial fluid (SF) and serum of Thoroughbred racehorses and to compare findings with radiographic and arthroscopic scores of joint injury severity.
Animals—78 Thoroughbreds with (n = 38) and without (40) osteochondral injury.
Procedures—Serum and metacarpophalangeal or carpal joint SF samples were collected from noninjured horses before and at the end of 5 to 6 months of race training (pre- and postexercise samples, respectively) and from horses with osteochondral injury (1 joint assessed/horse). Synovial fluid and serum CTX-II concentrations were determined by use of an ELISA. Radiographic and arthroscopic scores of joint injury severity were determined for the injured horses.
Results—The CTX-II concentrations in SF and SF:serum CTX-II ratio were significantly higher for horses with joint injuries, compared with pre- and postexercise findings in noninjured horses. Serum CTX-II concentrations in postexercise and injured-horse samples were significantly lower than values in pre-exercise samples. On the basis of serum and SF CTX-II concentrations and SF:serum CTX-II ratio, 64% to 93% of serum and SF samples were correctly classified into their appropriate group (pre-exercise, postexercise, or injured-joint samples). In horses with joint injuries, arthroscopic scores were positively correlated with radiographic scores, but neither score correlated with SF or serum CTX-II concentration.
Conclusions and Clinical Relevance—Results suggested that serum and SF CTX-II concentrations and SF:serum CTX-II ratio may be used to detect cartilage degradation in horses with joint injury.
Objective—To investigate effects of exercise on hyaline cartilage (HC), calcified cartilage (CC), and subchondral bone (SCB) thickness patterns of equine tarsi.
Sample Population—30 tarsi from cadavers of horses with known exercise history.
Procedures—Tarsi were assigned to 3 groups according to known exercise history as follows: pasture exercise only (PE tarsi), low-intensity general-purpose riding exercise (LE tarsi), and high-intensity elite competition riding exercise (EE tarsi). Osteochondral tissue from distal tarsal joints underwent histologic preparation. Hyaline cartilage, CC, and SCB thickness were measured at standard sites at medial, midline, and lateral locations across joints with a histomorphometric technique.
Results—HC, CC, and SCB thickness were significantly greater at all sites in EE tarsi, compared with PE tarsi; this was also true when LE tarsi were compared with PE tarsi. At specific sites, HC, CC, and SCB were significantly thicker in EE tarsi, compared with LE tarsi. Along the articular surface of the proximal aspect of the third metatarsal bone, SCB was thickest in EE tarsi and thinnest in LE tarsi; increases were greatest at sites previously reported to undergo peak strains and osteochondral damage.
Conclusions and Clinical Relevance—Increased exercise was associated with increased HC, CC, and SCB thickness in mature horses. At sites that undergo high compressive strains, with a reported predisposition to osteoarthritic change, there was increased CC and SCB thickness. These results may provide insight into the interaction between adaptive response to exercise and pathological change.
Objective—To determine whether the effects of a high–molecular-weight sodium hyaluronate alone or in combination with triamcinolone acetonide can mitigate chondrocyte glyocosaminoglycan (GAG) catabolism caused by interleukin (IL)-1 administration.
Sample Population—Chondrocytes collected from metacarpophalangeal joints of 10 horses euthanized for reasons unrelated to joint disease.
Procedures—Chondrocyte pellets were treated with medium (negative control), medium containing IL-1 only (positive control), or medium containing IL-1 with hyaluronic acid only (0.5 or 2.0 mg/mL), triamcinolone acetonide only (0.06 or 0.6 mg/mL), or hyaluronic acid (0.5 or 2.0 mg/mL) and triamcinolone acetonide (0.06 or 0.6 mg/mL) in combination. Chondrocyte pellets were assayed for newly synthesized GAG, total GAG content, total DNA content, and mRNA for collagen type II, aggrecan, and cyclooxygenase (COX)-2.
Results—High-concentration hyaluronic acid increased GAG synthesis, whereas high-concentration triamcinolone acetonide decreased loss of GAG into the medium. High concentrations of hyaluronic acid and triamcinolone acetonide increased total GAG content. There was no change in DNA content with either treatment. Triamcinolone acetonide reduced COX-2 mRNA as well as aggrecan and collagen type II expression. Treatment with hyaluronic acid had no effect on mRNA for COX-2, aggrecan, or collagen type II.
Conclusions and Clinical Relevance—Results indicated that high concentrations of hyaluronic acid or triamcinolone acetonide alone or in combination mitigated effects of IL-1 administration on GAG catabolism of equine chondrocytes.
Objective—To use quantitative ultrasonography to evaluate the association between the speed of sound (SOS) at 9 sites in the third metacarpal bone (MCIII) of racing Thoroughbreds with workload accumulation and the effect that MCIII failure has on this association.
Animals—Sixty-two 2- and 3-year-old Thoroughbreds in racing condition.
Procedures—Cumulative work index (CWI) was used to calculate total workload (CWItotal) and also 3 independent CWIs for the various gaits (ie, trot [CWItrot], gallop [CWIgallop], and race [CWIrace]) used during training and racing. Speed of sound was monitored in horses during the 2007 racing season and compared with the CWIs via regression analysis. Sex, age, limb, and MCIII failure were included as covariates in the model.
Results—SOS was significantly associated with CWItotal at 8 sites and with independent CWIs of the various gaits at all 9 sites. Progression of SOS in MCIIIs with workload differed significantly in horses with clinical signs of metacarpal bone failure, compared with results for horses with clinically normal MCIIIs, in 1 site by use of CWItotal and in 5 sites by use of the independent CWIs for the various gaits.
Conclusions and Clinical Relevance—These results indicated that SOS in the MCIII of racing Thoroughbreds followed a constant pattern of progression as workload accumulated. With the development of more precise quantitative ultrasonography devices, SOS corrected for amount of activity may be used to identify horses at risk of bone failure.
Objective—To investigate effects of osteochondral injury on high-mobility group box chromosomal protein 1 (HMGB-1) concentrations in synovial fluid (SF) from Thoroughbreds and to compare these results with radiographic and arthroscopic scores of severity of joint injury.
Animals—40 clinically normal rested Thoroughbreds (group 1) and 45 Thoroughbreds with osteochondral injury as a result of racing.
Procedures—SF was obtained from the metacarpophalangeal (MCP) joints, metatarsophalangeal (MTP) joints, middle carpal joints, and radiocarpal joints. For group 2, radiographic and arthroscopic scores were determined. Concentrations of SF HMGB-1 were determined by use of an ELISA.
Results—SF HMGB-1 concentrations in osteochondral-injured MCP-MTP joints were significantly higher than in normal MCP-MTP joints. Similarly, SF HMGB-1 concentrations in osteochondral-injured carpal joints were significantly higher than in normal carpal joints. Radiographic and arthroscopic scores were not correlated with SF HMGB-1 concentrations. Synovial fluid HMGB-1 concentrations ≥ 11 ng/mL for MCP-MTP joints and ≥ 9 ng/mL for carpal joints discriminated osteochondral-injured joints from normal joints. Horses with HMGB-1 concentrations ≥ 11 ng/mL for MCP-MTP joints were twice as likely to have an osteochondral injury, and horses with HMGB-1 concentrations ≥ 9 ng/mL for carpal joints were 4 times as likely to have an osteochondral injury.
Conclusions and Clinical Relevance—Osteochondral injury was associated with a significant increase in SF HMGB-1 concentrations in MCP-MTP and carpal joints, compared with results for clinically normal Thoroughbreds. Analysis of SF HMGB-1 concentrations may be useful for evaluation of joint injury in horses.