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  • Author or Editor: Lisa A. Beluche x
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Objective—To evaluate the effects of orally administered phenylbutazone on proteoglycan synthesis and chondrocyte inhibition by IL-1β in articular cartilage explants of horses.

Animals—11 healthy 1- to 2-year-old horses.

Procedure—Horses were randomly assigned to the control (n = 5) or treated group (4.4 mg of phenylbutazone/ kg of body weight, PO, q 12 h; n = 6). Articular cartilage specimens were collected before treatment was initiated (day 0), after 14 days of treatment, and 2 weeks after cessation of treatment (day 30). Proteoglycan synthesis and stromelysin concentration in cartilage extracts were assessed after 72 hours of culture in medium alone or with recombinant human interleukin-1β (IL-1β; 0.1 ng/ml).

Results—On day 0, proteoglycan synthesis was significantly less in cartilage explants cultured in IL-1β, compared with medium alone. Mean proteoglycan synthesis in explants collected on days 14 and 30 was significantly less in treated horses, compared with controls. However, incubation of explants from treated horses with IL-1β did not result in a further decrease in proteoglycan synthesis. Significant differences in stromelysin concentration were not detected between or within groups.

Conclusions and Clinical Relevance—Oral administration of phenylbutazone for 14 days significantly decreased proteoglycan synthesis in articular culture explants from healthy horses to a degree similar to that induced by in vitro exposure to IL-1β. Phenylbutazone should be used judiciously in athletic horses with osteoarthritis, because chronic administration may suppress proteoglycan synthesis and potentiate cartilage damage. (Am J Vet Res 2001; 62:1916–1921)

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in American Journal of Veterinary Research



To determine whether enrofloxacin has detrimental, dose-dependent effects on equine articular cartilage in vitro.


Cartilage explants were developed from 6 healthy horses between 0 and 96 months old.


Patellar cartilage explants were incubated in 5 concentrations of enrofloxacin (2 μg/ml, 10 μg/ml, 1,000 μg/ml, 10,000 μg/ml, and 50,000 μg/ml) for 72 hours. Proteoglycan synthesis (Na35SO4 incorporation for 24 hours), proteoglycan degradation (Na35SO4 release for 72 hours), endogenous proteoglycan content (dimethylmethlene blue assay), and total protein content were determined. Cartilage explants were evaluated by use of histomorphologic and histomorphometric techniques (toluidine blue stain) for cytologic and matrix characteristics. Quantitative data were analyzed with a one-way ANOVA to compare results among various enrofloxacin concentration groups and the control group. A general linear model was used to determine whether age had an effect.


Proteoglycan synthesis was excellent in control specimens and in specimens incubated in low concentrations of enrofloxacin (2 μg/ml and 10 μg/ml). High concentrations of enrofloxacin (> 1,000 μg/ml) effectively eliminated proteoglycan synthesis regardless of horse age. Proteoglycan degradation at low concentrations (2 μg/ml and 10 μg/ml) was not different than control. High concentrations of enrofloxacin (> 1,000 μg/ml) caused significant degradation. Different concentrations of enrofloxacin did not affect endogenous proteoglycan. High concentrations of enrofloxacin were associated with a significant increase in number of pyknotic nuclei.


Concentrations of enrofloxacin that might be achieved following systemic administration did not suppress chondrocyte metabolism in vitro. High concentrations of enrofloxacin (> 1,000 μg/ml) were toxic to chondrocytes. (Am J Vet Res 1999;60:577–582)

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in American Journal of Veterinary Research


Objective—To isolate and characterize bone marrow–derived equine mesenchymal stem cells (MSCs) for possible future therapeutic applications in horses.

Sample Population—Equine MSCs were isolated from bone marrow aspirates obtained from the sternum of 30 donor horses.

Procedures—Cells were cultured in medium (alpha-minimum essential medium) with a fetal calf serum content of 20%. Equine MSC features were analyzed to determine selfrenewing and differentiation capacity. For potential therapeutic applications, the migratory potential of equine MSCs was determined. An adenoviral vector was used to determine the transduction rate of equine MSCs.

Results—Equine MSCs can be culture-expanded. Equine MSCs undergo cryopreservation in liquid nitrogen without altering morphologic characteristics. Furthermore, equine MSCs maintain their ability to proliferate and differentiate after thawing. Immunocytochemically, the expression of the stem cell marker CD90 can be detected on equine MSCs. The multilineage differentiation potential of equine MSCs was revealed by their ability to undergo adipogenic, osteogenic, and chondrogenic differentiation.

Conclusions and Clinical Relevance—Our data indicate that bone marrow–derived stromal cells of horses can be characterized as MSCs. Equine MSCs have a high transduction rate and migratory potential and adapt to scaffold material in culture. As an autologous cell population, equine MSCs can be regarded as a promising cell population for tissue engineering in lesions of the musculoskeletal system in horses.

Full access
in American Journal of Veterinary Research