Quantifying invasive potential in cell spheroids via shear-induced erosion and tomographic shape reconstruction

Three-dimensional cellular spheroids represent a powerful in vitro model for recapitulating the physiological and mechanical complexity of in vivo specimens. In this study, we investigate the effect of controlled shear stress on NIH/3T3 fibroblast spheroids by using a custom rheo-optical parallel-plate apparatus. By adjusting the confinement level and the viscosity of the suspending medium, we modulate the flow-induced mechanical loading and monitor spheroid response over time through high-resolution time-lapse imaging. A robust image analysis pipeline enables isolation of rotational effects and quantification of morphological parameters. Our results reveal a shear-induced erosion mechanism, characterized by progressive cell detachment from the spheroid periphery without significant deformation. Importantly, erosion severity correlates with the extent of internal necrosis, underscoring a direct link between structural integrity and proliferative viability. Comparison with independent assays (i.e., mechanical compression and chemotaxis) confirms that necrotic content serves as a key modulator of both stiffness and invasive behavior. These findings provide new insights into the mechano-biological fragility of necrotic spheroids and establish a framework for future investigations of metastatic dissemination. Additionally, the spheroid response is reconstructed by means of tomographic reconstruction from multi-angle projections, enabling full three-dimensional visualization of spheroid morphology without any prior volume constraints or oversimplified geometric assumptions.