Programmed assembly of 3-dimensional microtissues with defined cellular connectivity.

Multicellular organs comprise differentiated cell types with discrete yet interdependent functions. The cells' spatial arrangements and interconnectivities, both critical elements of higher-order function, derive from complex developmental programs in vivo and are often difficult or impossible to emulate in vitro. Here, we report the bottom-up synthesis of microtissues composed of multiple cell types with programmed connectivity. We functionalized cells with short oligonucleotides to impart specific adhesive properties. Hybridization of complementary DNA sequences enabled the assembly of multicellular structures with defined cell-cell contacts. We demonstrated that the kinetic parameters of the assembly process depend on DNA sequence complexity, density, and total cell concentration. Thus, cell assembly can be highly controlled, enabling the design of microtissues with defined cell composition and stoichiometry. We used this strategy to construct a paracrine signaling network in isolated 3-dimensional microtissues.