An Ovine Model of in Vivo Bioreactor-based Bone Generation.

The generation of vascularized mineralized tissues of complex geometry without the use of extrinsic growth factors or exogenous cells requires a large animal model to recapitulate the challenges seen in the clinic. The proposed versatile ovine model can be utilized to investigate the use of a customized bioreactor to generate mineralized tissue, matching the size and shape of a defect prior to transfer to and integration within another site. The protocol results in bioreactors that can be harvested for investigation of the effects of different biomaterials for the generation of bone or to generate tissues appropriate for repair of bony defects; this protocol focuses on reconstruction of the mandible but could be modified for orthopaedic applications. The bioreactor packing material can be altered, allowing for the study of various commercially available or novel graft materials. The surgical procedure requires approximately 1.5 hours to implant 4 bioreactors adjacent to rib periosteum After 9 weeks, the harvest of the bioreactor tissue takes approximately one hour. If creating a craniofacial defect, an additional 2 hours should be taken for mandibular defect creation and 2 to 3 hours for the reconstruction. Sheep that have undergone reconstruction are typically euthanized after 12 weeks to allow for evaluation of transferred tissues. In this protocol, we discuss the necessary steps to ensure the reproducibility and analytical techniques to assess bone regeneration such as microcomputed tomography, mechanical analysis, and histology.