Journal Article

ProSense; AngioSense; arthritis; in vivo imaging

OBJECTIVE: To test a novel self-activating viridin (SAV) prodrug that slowly releases wortmannin, a potent phosphoinositide 3-kinase inhibitor, in a model of antibody-mediated inflammatory arthritis.

METHODS: The SAV prodrug was administered to K/BxN mice or to C57BL/6 (B6) mice that had been injected with K/BxN serum. Ankle thickness was measured, and histologic changes were scored after a 10-day disease course (serum-transfer arthritis). Protease activity was measured by a near-infrared imaging approach using a cleavable cathepsin-selective probe. Further near-infrared imaging techniques were used to analyze early changes in vascular permeability after serum injection, as well as neutrophil-endothelial cell interactions. Neutrophil functions were assessed using an oxidative burst assay as well as a degranulation assay.

RESULTS: SAV prevented ankle swelling in mice with serum-transfer arthritis in a dose-dependent manner. It also markedly reduced the extent of other features of arthritis, such as protease activity and histology scores for inflammation and joint erosion. Moreover, SAV was an effective therapeutic agent. The underlying mechanisms for the antiinflammatory activity were manifold. Endothelial permeability after serum injection was reduced, as was firm neutrophil attachment to endothelial cells. Endothelial cell activation by tumor necrosis factor alpha was impeded by SAV, as measured by the expression of vascular cell adhesion molecule. Crucial neutrophil functions, such as generation of reactive oxygen species and degranulation of protease-laden vesicles, were decreased by SAV administration.

CONCLUSION: A novel SAV prodrug proved strongly antiinflammatory in a murine model of antibody-induced inflammatory arthritis. Its activity could be attributed, at least in part, to the inhibition of neutrophil and endothelial cell functions.

Journal Article

Animals; Anti-Bacterial Agents; Bioware; Colony Count, Microbial; Mice; Mice, Inbred BALB C; Polymers; Prostheses and Implants; Rifampin; Silicone Elastomers; Staphylococcus aureus; Vancomycin; Xen29

OBJECTIVES Curing biomaterial-associated infection (BAI) frequently includes antibiotic treatment, implant removal and re-implantation. However, revision implants are at a greater risk of infection as they may attract bacteria from their infected surroundings. Polymer brush-coatings attract low numbers of bacteria, but the virtue of polymer brush-coatings in vivo has seldom been investigated. Here, we determine the possible benefits of polymer brush-coated versus pristine silicone rubber in revision surgery, using a murine model. METHODS BAI was induced in 26 mice by subcutaneous implantation of silicone rubber discs with a biofilm of Staphylococcus aureus Xen29. During the development of BAI, half of the mice received rifampicin/vancomycin treatment. After 5 days, the infected discs were removed from all mice, and either a polymer brush-coated or pristine silicone rubber disc was re-implanted. Revision discs were explanted after 5 days, and the number of cfu cultured from the discs and the surrounding tissue was determined. RESULTS None of the polymer brush-coated discs after antibiotic treatment appeared colonized by staphylococci, whereas 83% of the pristine silicone rubber discs were re-infected. Polymer brush-coated discs also showed reduced colonization rates in the absence of antibiotic treatment when compared with pristine silicone rubber discs. Tissue surrounding the discs was culture-positive in all cases. CONCLUSIONS Polymer brush-coatings are less prone to re-infection than pristine silicone rubber when used in revision surgery, i.e. when implanted in a subcutaneous pocket infected by a staphylococcal BAI. Antibiotic pre-treatment during the development of BAI hardly had any effect in preventing the colonization of pristine silicone rubber.

Journal Article

Animals; Anti-Bacterial Agents; Biofilms; Bioware; Drug Resistance, Bacterial; Mice; Mutation; Rifampin; Staphylococcus aureus; Xen29

OBJECTIVES To investigate in vivo fitness of rifampicin-resistant Staphylococcus aureus mutants in a mouse biofilm model using bioluminescence imaging. MATERIALS AND METHODS S. aureus was engineered with a luciferase operon to emit bioluminescence that can be detected in vivo using an IVIS imaging system. Two rifampicin-resistant strains of S. aureus that were previously isolated from animals undergoing rifampicin treatment, S464P (resistant to low concentrations of rifampicin) and H481Y (resistant to high concentrations of rifampicin), were characterized and then compared with their parental strain for in vivo fitness to form biofilm infections in the absence of rifampicin. RESULTS The mutant S464P showed better adaptation to in vivo growth than either the parental strain or H481Y without selective pressure. Six days after implanting pre-colonized catheters, bioluminescent signals were seen from 100% of the catheters coated by the mutant S464P. In comparison, only 83% and 61% of the catheters coated by the parental strain and H481Y, respectively, maintained a signal in vivo. Rifampicin treatment of S464P biofilms in vivo resulted in a slight decline, but earlier rebound in bioluminescence from these catheters compared with the parental signal, whereas rifampicin had no affect on bioluminescence in mice infected with mutant H481Y. CONCLUSIONS The mutant with low-level rifampicin resistance appears to be better adapted to in vivo growth than the mutant that has high-level rifampicin resistance. Moreover, the former mutant may actually have a slight competitive advantage over the rifampicin-susceptible strain (parental), raising awareness for the occurrence of such strains in clinical environments.

Journal Article

OsteoSense, Maestro, Animals; Bone Density Conservation Agents/administration & dosage/*pharmacokinetics; Bone and Bones/*metabolism; Calcium/metabolism; Chelating Agents; Decalcification Technique; Diphosphonates/administration & dosage/*pharmacokinetics; Durapatite/metabolism; Edetic Acid; Female; Femur/metabolism; Fibula/metabolism; Fluorescent Dyes/diagnostic use; Fluorometry; Humerus/metabolism; Injections, Intravenous; Mandible/metabolism; Models, Animal; Radius/metabolism; Rats; Rats, Nude; Spectrophotometry, Atomic; Tibia/metabolism; Tissue Distribution; Ulna/metabolism

OBJECTIVES: Bisphosphonates commonly used to treat osteoporosis, Paget's disease, multiple myeloma, hypercalcemia of malignancy and osteolytic lesions of cancer metastasis have been associated with bisphosphonate-associated jaw osteonecrosis (BJON). The underlying pathogenesis of BJON is unclear, but disproportionate bisphosphonate concentration in the jaw has been proposed as one potential etiological factor. This study tested the hypothesis that skeletal biodistribution of intravenous bisphosphonate is anatomic site-dependent in a rat model system. MATERIALS AND METHODS: Fluorescently labeled pamidronate was injected intravenously in athymic rats of equal weights followed by in vivo whole body fluorimetry, ex vivo optical imaging of oral, axial, and appendicular bones and ethylenediaminetetraacetic acid bone decalcification to assess hydroxyapatite-bound bisphosphonate. RESULTS: Bisphosphonate uptake and bisphosphonate released per unit calcium were similar in oral and appendicular bones but lower than those in axial bones. Hydroxyapatite-bound bisphosphonate liberated by sequential acid decalcification was the highest in oral, relative to axial and appendicular bones (P < 0.05). CONCLUSIONS: This study demonstrates regional differences in uptake and release of bisphosphonate from oral, axial, and appendicular bones of immune deficient rats.

Journal Article

Ovarian cancer; Molecular imaging; Intraoperative imaging; Fluorescence imaging

OBJECTIVES: Cytoreductive surgery is a cornerstone of therapy in metastatic ovarian cancer. While conventional white light (WL) inspection detects many obvious tumor foci, careful histologic comparison has shown considerable miss rates for smaller foci. The goal of this study was to compare tumor detection using WL versus near infrared (NIR) imaging with a protease activatable probe, as well as to evaluate the ability to quantify NIR fluorescence using a novel quantitative optical imaging system.

METHODS: A murine model for peritoneal carcinomatosis was generated and metastatic foci were imaged using WL and NIR imaging following the i.v. administration of the protease activatable probe ProSense750. The presence of tumor was confirmed by histology. Additionally, the ability to account for variations in fluorescence signal intensity due to changes in distance between the catheter and target lesion during laparoscopic procedures was evaluated.

RESULTS: NIR imaging with a ProSense750 significantly improved upon the target-to-background ratios (TBRs) of tumor foci in comparison to WL imaging (minimum improvement was approximately 3.5 fold). Based on 52 histologically validated samples, the sensitivity for WL imaging was 69%, while the sensitivity for NIR imaging was 100%. The effects of intraoperative distance changes upon fluorescence intensity were corrected in realtime, resulting in a decrease from 89% to 5% in signal variance during fluorescence laparoscopy.

CONCLUSIONS: With its molecular specificity, low background autofluorescence, high TBRs, and quantitative signal, optical imaging with NIR protease activatable probes greatly improves upon the intraoperative detection of ovarian cancer metastases.