Botulinum neurotoxin type A does not exert concentration-dependent effects on equine articular cartilage in vitro

OBJECTIVE To determine whether Botulinum neurotoxin type A (BoNT-A) ameliorates the effects of interleukin 1 (IL-1) on equine articular cartilage, or exerts negative effects on normal equine articular cartilage homeostasis in vitro. SAMPLE Articular cartilage explants from 6 healthy femoropatellar joints of 3 adult horses. METHODS Explants were allocated to the IL-1 challenged or unchallenged group, then exposed to 1 of 6 concentrations of BoNT-A (0, 1, 10, 50, 100, or 500 pg/mL) for 96 hours. To assess BoNT-A's effects on inflammation, prostaglandin E2 2 (PGE2) 2 ) was measured in media via ELISA. Matrix degradation was determined as the percentage of sulfated glycos-- aminoglycans (sGAG) released from explants via dimethylmethylene blue assay. Aggrecan synthesis was estimated using CS846 ELISA and collagen type II degradation was estimated using C2C ELISA on media. Chondrocyte apop-- tosis was assessed via in-situ TUNEL assay. Generalized linear mixed models were fitted to determine treatment effects using alpha = 0.05. RESULTS The challenge with IL-1 resulted in increased concentrations of PGE2 2 and CS846 in media and increased release of sGAG from explants. BoNT-A did not significantly impact PGE2 2 or CS846 concentration in media, percentage of sGAG released, or chondrocyte apoptosis in IL-1 challenged or unchallenged cartilage explants. The concentration of C2C in media was below the quantifiable limit of the ELISA in all samples. CLINICAL RELEVANCE BoNT-A did not show chondroprotective effects or have negative effects on cartilage homeostasis in vitro at the concentrations tested. While chondroprotective effects were not observed, BoNT-A may be safe for intraarticular use. In vivo testing is warranted before clinical use.