Blood Prefabrication Subcutaneous Small Animal Model for the Evaluation of Bone Substitute Materials

Because of the size of bone substitute material particles, large animal bone defect models are usually required for the assessment of these materials. However, these models have several disadvantages including high cost, complicated operation procedures, ethical issues, and difficulties in sample analysis. In addition, for mimicking the bone environment, conventional subcutaneous models require the addition of osteogenic factors and stem cells, resulting in an expensive model with a complex experimental procedure. To avoid these issues, in this study, we proposed a convenient and effective blood prefabrication subcutaneous small animal model that could be applied to assess bone substitute materials. Our results demonstrated that blood prefabrication could be an economical, convenient, and useful "adhesive" for handling bone substitute particles. This process provided porcine hydroxyapatite (PHA) with a microenvironment enriched with mesenchymal stem cells and growth factors. Using this strategy, a bonelike structure could form in a rat subcutaneous pocket. Furthermore, the optimized subcutaneous model was used to evaluate the PHA's osteoinductivity, producing results similar to those of the calvarial bone defect in terms of osteogenesis, osteoclastogenesis, and blood vessel formation. These results collectively imply that the blood prefabrication subcutaneous small animal model is convenient and effective for the assessment of osteoinductivity of bone substitute materials.