Direct implantation of VX-2 carcinoma: a new rabbit bone model using a three-dimensional matrix as a carrier for the tumor cells.

BACKGROUND: Animal bone models are inevitable for musculoskeletal research. The induction of a local bone tumor is complex and time consuming. In this study a new model is presented using a direct implantation of tumor cells into the bone without a preliminary passaging of the cells. METHODS: A three-dimensional matrix consisting of alginate spheroids and carrying the VX-2 tumor suspension was used for implantation into the bone of 6 female New Zealand white rabbits. X-ray imaging, CT and MRI scans as well as a histological examination were carried out. RESULTS: All rabbits developed local bone tumor in the metaphysis of the femoral leg. Bone tumor was identifiable on average 6.2 weeks after implantation. Fluoroscopy, CT and MRI scans showed a cortical reaction but no destruction of the compact bone together with a mean tumor size of 14 mm. Histological examination revealed a tumor infiltration with an activation of osteoclasts and an osteoclastic resorption. CONCLUSION: The direct implantation of a VX-2 tumor suspension into the rabbit bone using alginate spheroids is an effective and reproducible way to successfully induce bone tumor. This new animal model allows further examination of surgical and minimal invasive therapy in musculoskeletal research.

Radiofrequency ablation in experimental bone metastases using a controlled and navigated ablation device.

BACKGROUND: Radiofrequency ablation is a minimal invasive therapy in the treatment of bone metastases. In this study we present a new ablation system enabling an ablation in multiple directions and with an adaptable size and shape. MATERIAL AND METHODS: VX-2 tumor was used for the induction of experimental bone metastases in the femur of six New Zealand white rabbits. X-ray imaging as well as CT and MRI scans before and after treatment was carried out. After detecting bone tumor, radiofrequency ablation was performed. The ablation instrument contained a 10 g bipolar, articulated extendable electrode and a proprietary generator with an impedance controlled algorithm. All bones and the soft tissue were examined histologically. RESULTS: All animals developed local bone tumor. Mean duration until first osteolytic lesions on CT-scans was 48±14 days. The mean lesion area was 26 mm(2). No systemic tumor spread was seen. 6 radiofrequency procedures were carried out with a mean application time of 6 min±2:30 and an average temperature in the region of effect of 55 °C±4. MRI imaging demonstrated an ablation zone of 23±6 mm around the electrode. Histopathology showed an extensive heat necrosis with no remaining tumor cells in the ablation area. CONCLUSION: Radiofrequency ablation is a quickly developing treatment option on the field of minimal invasive bone tumor therapy. The electrode enables an ablation adapted to size and shape of the metastases. Further clinical studies are necessary to test and enhance this radiofrequency system.

[Induction of bone tissue on different matrices: an in vitro and a in vivo pilot study in the SCID mouse]. / Induktion von Knochengewebe auf unterschiedlichen Matrizes: Eine In-vitro- und In-vivo-Pilotstudie in der SCID Maus.

AIM: Three resorbable biomaterials were evaluated regarding proliferation and osteogenic differentiation of human bone marrow stromal cells (BMSC) in vitro. In a second step, the new biomaterial, calcium-deficient hydroxyapatite (CDHA), was tested in a pilot in vivo study by subcutaneous implantation in the severe combined immunodeficiency (SCID) mouse. METHODS: CDHA, beta-tricalcium phosphate (beta-TCP), and demineralized bone matrix (DBM) were seeded with human BMSC and cultured in osteogenic supplements for 3 weeks. In the pilot in vivo study, CDHA was seeded with BMSC and kept in osteogenic media for 2 weeks (group A) before subcutaneous implantation in 8 SCID mice for 3 and 8 weeks. In addition, CDHA seeded with BMSC without prior osteogenic induction (group B) and empty ceramics were implanted in each mouse. RESULTS: Total protein content and the values for specific alkaline phosphatase (ALP) increased significantly in vitro on all matrices, but no significant difference between the groups was noted. In the pilot in vivo study all ceramics were well penetrated by cells. After 8 weeks 2 of 4 samples in group B and 1 of 4 samples in group A revealed cells resembling hypertrophic chondrocytes. Specific ALP was higher in the group B (p = 0.012, Z = - 2.5) compared to empty ceramics. There were no significant differences between groups A and B. Differences between group A and the empty control did not become significant (p = 0.069, Z = - 1.8). CONCLUSION: All three matrices promoted BMSC proliferation and differentiation to osteogenic cells in vitro. Human BMSC on CDHA showed signs of osteogenic differentiation after subcutaneous implantation into SCID mice.