No abstract

AbstarctInfections after bone reconstructive surgery are a real therapeutic and economic issue for the modern health care system. As the pathogen (most often Staphylococcus aureus) is able to develop a biofilm inside the bone, local delivery of antibiotics is of interest since high drug concentrations would be delivered directly at the target place. In this context, this study evaluated a porous hydroxyapatite implant as biocompatible bone substitute and vancomycin-delivery system to prevent post-operative infections. A simple method of impregnation with optimised conditions insured a high antibiotic loading (up to 2.3 ± 0.3 mg/m), with a complete in vitro release obtained within 1-5 days. Additionally, the bacteriostatic and bactericidal effects of vancomycin were retained after loading on hydroxyapatite, as demonstrated after challenge with a Staphylococcus aureus strain. Regarding the biocompatibility, a wound healing assay of pre-osteoblastic MC3T3-E1 cells exposed to various concentrations of vancomycin revealed a dose-dependent reduction in cell migration for antibiotic concentrations higher than 1 mg/mL. Meanwhile, cells were able to proliferate normally on vancomycin-loaded scaffolds, although cell initial adhesion was seriously impaired for scaffolds loaded with 2.3 mg/m Loaded scaffolds could be stored up to three months at room temperature without any degradation of the antibiotic. Together, these results demonstrate the efficacy of these hydroxyapatite bone substitutes for local delivery of vancomycin in the context of bone infection.

Maedi-visna virus (MVV) causes encephalitis, pneumonia and arthritis in sheep.In vitro, MVV infection and replication lead to strong cytopathic effects characterized by syncytia formation and subsequent cellular lysis. It was demonstrated previously that MVV infection in vitro induces cell death of sheep choroid plexus cells (SCPC) by a mechanism that can be associated with apoptotic cell death. Here, the relative implication of several caspases during acute infection with MVV is investigated by employing diverse in vitro and in situ strategies. It was demonstrated using specific pairs of caspase substrates and inhibitors that, during in vitro infection of SCPC by MVV, the two major pathways of caspase activation (i.e. intrinsic and extrinsic pathways) were stimulated : significant caspase-9 and -8 activities, as well as caspase-3 activity, were detected. To study the role of caspases during MVV infection in vitro, specific, cell-permeable, caspase inhibitors were used. First, these results showed that both z-DEVD-FMK (a potent inhibitor of caspase-3-like activities) and z-VAD-FMK (a broad spectrum caspase inhibitor) inhibit caspase-9, -8 and -3 activities. Second, both irreversible caspase inhibitors, z-DEVD-FMK and z-VAD-FMK, delayed MVV-induced cellular lysis as well as virus growth. Third, during SCPC in vitro infection by MVV, cells were positively stained with FITC-VAD-FMK, a probe that specifically stains cells containing active caspases. In conclusion, these data suggest that MVV infection in vitro induces SCPC cell death by a mechanism that is strongly dependent on active caspases.

No abstract