Programming Niche Accessibility and In Vitro Stemness with Intercellular DNA Reactions.

Stem cells generally exist in low abundance and tend to lose stemness in the absence of self-renewal signals. While extracellular-matrix-mimicking techniques have been developed to support stem cell proliferation, the lack of niche cells in these synthetic systems often hampers continuous stem cell expansion and maintenance of pluripotency, which are indispensable for regenerative medicine. Here, an intercellular DNA-reaction-programmed ESPN (expansion of stem cells with pairing niches) strategy is developed for 3D culture of mammary stem cells (MaSCs). Boolean logic operations are implemented to confer DNA-programmed mechanical signaling and genetically engineered morphogen signaling by niche cells, resulting in sustained expansion of MaSCs in vitro. The creation of stem cell niches improves the proliferation of pluripotent cells by four times during one-week culture. This method thus provides a novel approach for logical regulation of stemness and proliferation of stem cells for biomedicine.