Development of a Composite Tissue Engineered Alveolar Bone−Mucosal Model Using Conventional and 3D Printed Scaffolding Techniques

Advances in tissue engineering have allowed the construction of various tissues of the oral and maxillofacial region for clinical and in vitro modelling proposes. Additive manufacturing, also known as three−dimensional printing (3DP) is an innovative technique that offers an entirely new method of fabricating geometrically precise 3D structures, allowing the opportunity to progress composite tissue engineering to the point where complex anatomical relationships can be accurately replicated. The aim of this study was to develop and characterise a novel 3D composite human alveolar bone−mucosal model (ABMM) based on conventional and 3D printed bone scaffolds.
Two types of bone scaffold were used: firstly, a conventional hydroxyapatite/tricalcium phosphate (HA/TCP) scaffold fabricated using an aqueous gel-casting method, and secondly, a 3D printed β−tricalcium phosphate (β−TCP) scaffold prepared using an extrusion−based Rapid Prototyping plotting system. In order to construct a composite bone−mucosal model, alveolar bone-derived osteoblasts were seeded into the respective scaffolds (both conventional and printed) and the resultant bone constructs were then attached to a tissue engineered, collagen−based oral mucosa. Histological, immunohistochemical, and ultrastructural features of the mucosal part as well as, the histology, genes expression, and proteins secretion of the composite models were examined to validate the ABMM as a representative analogue of combined oral hard and soft tissues.
The mucosal component demonstrated a mature epithelium undergoing terminal differentiation similar to that of native oral mucosa, as confirmed using cytokeratin immunohistochemistry. Histological evaluation of ABMM confirmed an anatomically representative tri-layer consisting of distinct epithelial, connective tissue, and bone layers. Interrogation of osteogenic and epithelial−related gene expression within the models confirmed an osteogenic expression profile in the tri−layered model that was not observed in epithelial−stromal bilayers. Collectively, these data suggest that the developed composite model displayed characteristics similar to those of normal tissue counterparts. This novel tri−layered model, therefore, may offer great scope as a more advanced, and anatomically representative tool for a number of in vitro applications.