Engineering Bone-Mimetic Microspheres to Recapitulate the Tumor Microenvironment for In Vitro Osteosarcoma Modeling

Background: Osteosarcoma (OS) is an aggressive bone tumor. The lack of physiologically relevant three-dimensional models that recapitulate the native tumor microenvironment hampers drug development and mechanistic studies. The study aimed to develop bone-mimetic microspheres for the construction of an OS model. Materials and Methods: We employed droplet microfluidics to fabricate bone-mimetic microspheres (named MSHA) from a composite of gelatin methacryloyl, polyethylene glycol diacrylate, and nano-hydroxyapatite (nHA). MNNG/HOS cells were cultured on MSHA microspheres and subsequently evaluated for their bioactivity and capabilities of stemness, migration, and invasion. Results: The microfluidic platform enabled efficient and scalable production of highly uniform MSHA microspheres with controlled sizes. MNNG/HOS cells cultured on MSHA maintained high viability and spontaneously formed compact tumor spheroids after 7 days. Compared with two-dimensional cultures, cells cultured on these microsphere-based platforms exhibited enhanced migration and invasion capacities, along with increased expression of relevant biomarkers. RNA sequencing further revealed the activation of cancer-related pathways. Notably, the incorporation of nHA into microspheres amplified these malignant phenotypes, potentially through the activation of ECM–receptor interaction and calcium signaling pathways. Conclusions: The microfluidics-fabricated MSHA microspheres, as biomimetic three-dimensional culture scaffolds, offer a promising platform for applications in mechanistic studies of osteosarcoma progression and drug screening.