Introduction Ciprofloxacin, a commonly prescribed fluoroquinolone antibiotic, has been shown to have a deleterious effect on the tendon extracellular matrix. The aims of this study were to determine the effects of short term exposure of ciprofloxacin on 1) tenocyte metabolism, 2) glycosaminoglycan content, and 3) mRNA expression levels of extracellular proteoglycans, and to correlate these changes with the production of newly synthesised proteoglycans in explant cultures of equine tendon.
Methods Normal superficial digital flexor tendon from 6 yr old Thoroughbred horses were incubated for 4 days in DMEM alone (control), or DMEM containing up to 300 µg/ml ciprofloxacin (CPX). The effect of CPX on the metabolism of tenocytes was determined by lactate production and Alamar blue assay and glycosaminoglycan content was determined by a dimethylene blue assay. Levels of gene expression of aggrecan, versican, decorin, biglycan and fibromodulin were determined by quantitative PCR. The production of newly synthesised proteoglycans was determined by 35S-sulfate incorporation at the end of the treatment period.
Results Higher levels of CPX (≥100 µg/ml) reduced tenocyte metabolism by 30–40% as measured by lactate production and Alamar blue assay. There was no change in glycosaminoglycan content nor mRNA expression levels of aggrecan, versican, decorin, biglycan or fibromodiulin in CPX-treated tendon explants compared with control. However, CPX suppressed the synthesis of both 35S-labelled large and small proteoglycans in a dose dependent manner.
Discussion The suppression of newly synthesised proteoglycans in tendon explants treated with CPX suggests that these changes are driven by changes in metabolism rather than expression of its associated genes.
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