Pharmacological alternatives to oxytetracycline as potential treatment of flexural limb deformities in foals

Flexural limb deformities are a widespread condition in foals. Oxytetracycline (OTC) is a common conservative treatment option due to its relaxing effect on the muscle-tendon unit. However, the antimicrobial properties of OTC and its potential adverse side effects warrant the investigation of alternatives. For the current study, a panel of substances with potentially similar mechanisms of action to treat fl exural deformities but without antimicrobial properties was selected. The aims of this thesis were to assess the infl uence of these substances in vitro (1) on the viability and proliferation of juvenile tendon and ligament myofi broblasts, and (2) on collagen gel contraction by myofi broblasts in vitro. Myofi broblasts from superfi cial digital fl exor tendons (SDFT) and accessory ligaments of the deep digital fl exor tendons (ALDDFTs) of foals were cultured, imaged by phase-contrast microscopy and characterized by immunochemistry. The myofi broblasts were incubated with OTC, the MMP-inhibitors incyclinide, ilomastat, aprotinin and pentoxifylline, the lathyrogenic agent β-aminopropionitrile fumarate (BAPN) and Dulbecco’s modifi ed Eagle medium (DMEM) as a control. In a fi rst step, the viability and proliferation capacities of the myofi broblasts were assessed through colorimetric cell viability (MTS) and crystal violet assays. In a second step, the cultured myofi broblasts were seeded into collagen gels containing OTC, the previously mentioned alternative substances, or controls. The gel surface areas were measured from photographs at regular intervals for up to 96 hours after release. Contraction differences between gels incubated with the different substances were statistically evaluated.