Concurrent versus delayed exposure to corticosteroids in equine articular tissues cultured with local anesthetic.

Objective: To determine the effect of concurrent versus delayed treatment with corticosteroid on equine articular tissues also treated with local anesthetic in vitro in the presence of inflammatory mediators.

Study Design: Controlled laboratory study.

Animals: Five geldings, one mare (aged 3-18 years).

Methods: From each horse, 24 synovial and 12 osteochondral explants were cultured in a 12-well plate (2 wells/group, 2 synovial and 1 osteochondral explant/well, total 216 explants in the study). Explants were stimulated in culture medium with 10 μg/ml recombinant equine interleukin-1β and 10 μg/ml tumor necrosis factor-α for 48 hours, then randomly assigned to six treatments: unstimulated control, stimulated control, triamcinolone acetonide (TA, 10  M), mepivacaine hydrochloride (MH, 4.4 mg/ml), MH + TA (concurrent) and MH + TA (delayed). The delayed group was treated with MH and, 6 days later, treated with TA. Every 3 days for 9 days total, medium levels of lactate dehydrogenase (LDH), prostaglandin E (PGE ), matrix metalloproteinase 13 (MMP-13) and glycosaminoglycan (GAG) were quantified via ELISA. Data were analyzed with mixed-effects models with Tukey's multiple comparisons.

Results: Stimulation increased medium PGE and MMP-13 and had no effect on LDH or GAG. Treatment with MH increased LDH and decreased PGE and MMP-13. Treatment with TA decreased PGE and MMP-13.

Conclusion: There were no differences in cytotoxicity, inflammation or matrix degradation for delayed or concurrent MH and TA treatment groups up to 9 days in culture.

Clinical Significance: The lack of an effect of concurrent versus delayed treatment might indicate that concurrent therapy is acceptable.