Establishment of self-organization system in rapidly formed multicellular heterospheroids.

Multicellular heterospheroids including two or more cell types have some tissue/organ properties and can be used in cell-to-cell interaction studies. However, the spheroid formation is difficult to control because the adhesion efficacy is different in each cell type. To solve this, we applied a rapid cell-to-cell adhesion method, avidin-biotin (AB) binding, to spheroid formation. Introduction of avidin or biotin molecules to the cell surfaces of Mile Sven 1 (MS1) cells promoted formation of spheroid in minutes. This method allowed the construction of heterospheroids having homogenous distributions of different cell types. Interestingly, cells showed self-organization and MS1 cells formed networks with Hep G2 cells. NIH3T3 cells also remodeled when mixed with Hep G2 cells. In contrast, a combination of MS1 and NIH3T3 cells failed to show pattern formation, indicating that self-organization was based on the composition of cell types. Actin polymerization not cell proliferation was the dominant factor in remodeling of heterospheroids in the first 24 h. We also demonstrated the self-organization of spheroids comprising three different cell types. The new technology to assemble cells is important not only to study cell-to-cell interaction but also to make three-dimensional complicated tissues.