3D-Printed β-TCP Scaffold as a Bone-Mimicking Environment for an Engineered Model of Osteosarcoma: In Vitro Properties and Transcriptomic Insights

In the face of advancements in osteosarcoma research, existing preclinical models - including in vitro (i.e., two- and three-dimensional cell cultures, organoids) and in vivo approaches (i.e., xenografts, animal models) - are often characterised by low translatability, limiting their predictive power for clinical outcomes. This study investigated the potential use of a 3D-printed β-tricalcium phosphate (β-TCP) scaffold as a bone-mimicking environment in an advanced in vitro osteosarcoma preclinical model. The compatibility of the scaffold with osteosarcoma cell spheroids, endothelial cells, and primary bone marrow-derived mesenchymal stem cells (pBMSCs) was evaluated along with its physicochemical characteristics. Transcriptomic analysis of pBMSCs on the scaffolds revealed gene expression profiles indicating pronounced extracellular matrix organisation and minor osteogenic activity. The model effectively replicated significant aspects of the tumour microenvironment in a tri-culture system, with dynamic perfusion enhancing metabolic activity. The developed scaffold-based model was employed in the doxorubicin cytotoxicity test. The physiological significance of the tri-culture was demonstrated by its distinct doxorubicin accumulation, in contrast to spheroid monocultures. Despite the limitations of the proposed approach regarding efficient vascularisation of the model, this study highlights the potential of 3D-printed β-TCP scaffolds in tumour modelling to support physiologically relevant preclinical models.