Extracellular matrix regulation of cell spheroid invasion in a 3D bioprinted solid tumor-on-a-chip.

ABSTRACT

Tumor organoids and tumors-on-chips can be built by placing patient-derived cells within an extracellular matrix (ECM) for personalized medicine. The ECM influences the tumor response, and understanding the ECM-tumor relationship is important before translating tumor-on-chips into clinics. In this work, we tuned the physical and structural characteristics of ECM in a bioprinted soft-tissue sarcoma microtissue. We formed 3D spheroids at a controlled size and encapsulated them into our gelatin methacryloyl (GelMA)-based bioink to make perfusable hydrogel-based microfluidic chips. We then demonstrated the scalability and customization flexibility of our hydrogel-based chip via engineering tools. A multiscale physical and structural data analysis suggested a relationship between cell invasion response and bioink characteristics. Tumor cell invasive behavior and focal adhesion properties were observed in response to varying polymer network densities of the GelMA-based bioink. Immunostaining assays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) helped assess the bioactivity of the microtissue and measure the cell invasion. The RT-qPCR results showed higher expressions of HIF-1α, CD44, and MMP2 genes in a lower polymer density, highlighting the correlation between bioink structural porosity, ECM stiffness, and tumor spheroid response. In conclusion, this work is the first step in modeling STS tumor invasiveness in hydrogel-based microfluidic chips, and our tunable bioink may help reduce the variability of current tumor-on-chips. STATEMENT OF SIGNIFICANCE: We optimized an engineering protocol for making tumor spheroids at a controlled size, embedding spheroids into a gelatin-based matrix, and constructing a perfusable microfluidic device. A higher tumor invasion was observed in a low-stiffness matrix than a high-stiffness matrix. The physical characterizations revealed how the stiffness is controlled by the density of polymer chain networks and porosity. The biological assays revealed how the structural properties of the gelatin matrix and hypoxia in tumor progression impact cell invasion. The cell spheroids' responses underscore the importance of replicating physical and structural properties to mimic tumor response. This work can contribute to personalized medicine by making more effective, tailored cancer models.