Citation

Mixed multicellular spheroids containing two or more cell types can be used as tissue models. We previously showed that mixed spheroids containing NIH3T3 mouse fibroblasts and MIN6 mouse pancreatic cells showed core-shell-type distribution, with NIH3T3 cells being located in the core region surrounded by MIN6 cells. In the present study, we investigated mechanisms underlying the determination and regulation of cellular distribution in these spheroids. Time-lapse microscopy showed that randomly mixed NIH3T3 and MIN6 cells separated from each other and showed core-shell-type distribution. Treatment of these cells with cellular migration inhibitors suggested that the core-shell-type distribution was regulated by focal adhesion kinase (FAK) signal in NIH3T3 cells. Microwells coated with collagen I, an FAK ligand, were prepared to regulate cellular distribution by inducing an exogenous FAK signal from outside the spheroids. NIH3T3/MIN6 spheroids formed in the collagen I-coated microwells showed random cellular distribution, suggesting that FAK signal-dependent migration of NIH3T3 cells toward the core region mediated the core-shell-type distribution. These results indicate that cellular distribution in NIH3T3/MIN6 spheroids can be regulated by altering FAK-mediated directional migration of NIH3T3 cells by using collagen I-coated microwells.