Background

Due to their tailored porous texture, breathability and flexibility, carbon cloths (CCs) are good scaffolds for biomedical application. However, biocompatibility of CCs depends on their physic-chemical properties. Calcium phosphate ceramics (CaP) are well known for their use in orthopaedic field. So, carbon cloth-reinforced CaP composites are promising bioceramic materials for bone regeneration.

Purpose of the study: The efficacy of a new oestrogeneration biomaterial should be demonstrated by in vivo grafts in animal models. Critical filling of bone defects in the rat could be useful as a model before beginning studies in large animals such as the sheep, goat or dog. Creation of a critical defect in the rat femur has been described, but not standardized, leading to difficult comparison between series. In this work, we wanted to establish a detailed standardisable surgical protocol for the creation of a 6 mm femur defect in the rat.

Material and methods: We compared three anaesthesia protocols using 18 mal Wistar rats aged 21 weeks. We developed a surgical procedure enabling study of the advantages of the different commonly used surgical devices either in research or clinic to achieve osteosynthesis and a 6 mm bone defect. We also compared two types of fixation plates (and screws) available on the marker: a 1.2 mm thick titanium plate used for hand surgery and a 1.5 mm steel plate (veterinary medicine). Our postoperative clinical and radiographic follow-up was designed to validate our operative protocol and evaluate osteoregeneration.

Results: We demonstrated first that the use of multimodal anaesthesia radically improved the clinical outcome in the animals. We then demonstrated that the 1.2 mm titanium plates recommended in other studies were too fragile in our model and that the steel 1.5 mm veterinary plates were more adapted. We finally demonstrated the superiority of surgical devises to create a defect and for osteosynthesis. We described a postoperative protocol offering satisfactory evaluation, clinically and radiographically.

Discussion: This work is the first describing this protocol in detail. Improvements in feasibility and cost will make a readily exploitable model for other laboratories. The follow-up on this work should be aimed at improving the quality and pertinence of the analysis methods for the assessment of bone regeneration.

Conclusion: We propose a mode for the critical defect in rat femur bone as a reliable model for the study of osteogenic capacities of new biomaterials.

Purpose of the study: The current approach for improving the performance of compact bone substitutes is to seed them with selected mesenchymatous stem cells amplified and differentiated to the osteoblastic line in vitro. We hypothesized that the preservation of all these elements in the bone marrow would be most effective for bone tissue formation.

Material and methods: Subcutaneous and intramuscular implantation in C57BL/6 mice. We developed a new approach for bone tissue engineering based on an extemporaneous incorporation of total bone marrow into an injectable bone substitute (IBS2). IBS2 is a new polymerizable hydrogel associated with beads of calcium phosphate (BCP) which can be used to implant total bone marrow. A subcutaneous and intramuscular implantation model in mice was tested to analyze the feasibility of this type of graft. Total bone marrow cells from C57BL/6 male mice were seeded in IBS (10 million cells per 100 microliters). This implant was injected subcutaneously (dorsal position) and intramuscularly (left hind foot) in C57BL/6 female mice. TRAP activity was measured under optical microscopy on paraffin embedded HES stained slices at 4 and 8 weeks.

Results and discussion: Incorporation of total bone marrow cells in injectable IBS2 produced implants which were rich in mesenchymatous cells, vessels, osteo-clasts, collagen fibers, and osteoid tissue. This demonstrated the great potential of this new approach. In addition, this method is simple and can be performed in the operative room without ex vivo culture. Comparison of this model of extemporaneous cell therapy with a graft of meschymatous cells amplified ex vivo is currently under way.