Metastatic progression of ovarian cancer through the peritoneal fluidic microenvironment is mediated predominantly by tumor cell clusters known as spheroids. Such spheroids also comprise the cells extracellular matrix (ECM). Spheroids with lumen, often seen in malignant ascites, are associated with a basement membrane (BM)-like coat. Herein, we combine microfluidics with high-speed time-lapse videography and imaging analysis to investigate the consequences of lumen formation and the BM coat on the architecture and integrity of ovarian cancer spheroids providing architectural robustness to the transitory ovarian cancer metastatic niche within constrained flow spaces. Upon transit through spatially constrained environments, lumen-less moruloid spheroids deform followed by an incomplete and temporally extended ([~]4.8 s) recovery. The transit causes intercellular rearrangement during entry and shows susceptibility to cellular disintegration. On the other hand, lumen-containing blastuloid spheroids exhibit minimal intra-spheroidal rearrangements. They exhibit a lower tendency for disintegration and quickly ([~]1.5 s) recover their morphology upon exit. Significantly, removing the blastuloid BM through collagenase treatment reverts the mechanical behaviors of these spheroids to those typifying their moruloid counterparts. Simulations using an experimentally calibrated Cellular Potts model predict the requirement of higher intercellular adhesion for blastuloid behavior, which we confirm through increased E-cadherin expression in blastuloid spheroids. Surprisingly, E-cadherin expression is dependent on the BM coat, elucidating the latters role in enhancing cell-cell adhesion. Our results show how spheroidal matrix engenders lumen formation and higher intercellular adhesion, in turn providing architectural robustness of the transitory ovarian cancer metastatic niche within constrained flow spaces.
Significance StatementInvestigating the mechanical and biophysical properties of disseminated ovarian cancer spheroids is instrumental to our understanding of their metastatic progression. We take a microfluidics-based approach to investigate the biophysical contributions of a key spheroidal constituent: basement membrane-like extracellular matrix, which is typical to hollow blastuloid spheroids, distinguishing them from the solid moruloid spheroids. We observe using high-speed videography, imaging analysis and multiscale computational modeling that the basement membrane renders blastuloid spheroids less deformable and resistant to disintegration than moruloid spheroids. We trace this function to jamming of cells between the blastuloid lumen and basement membrane, and high intercellular adhesion.
