Gartner used the approach to create a tiny sphere in which two onion-like layers of cells encase one another. The innermost cells secrete a protein growth factor that the outer layer of cells needs to survive. This intercellular signaling depends on the close proximity of the cells to one another due to their DNA “glue.” The team calls the structure a “microtissue”—simpler than most of the tissues the body builds but a useful model for studying specific cell-to-cell interactions in the lab. The contact-dependent exchange of survival factors in their system mimics signaling that spurs the growth of tumors and immune cells, according to their paper, published March 24, 2009, in the Proceedings of the National Academy of Sciences.

This first microtissue demonstrates that Bertozzi and Gartner's technique works. The method should be readily accessible to researchers in other labs who want to design their own microtissues, and because the DNA “glue” on the surface of each cellular building block “really has nothing to do with the individual cell type,” the possibilities for directing different assemblies are virtually limitless, Gartner says.

Gartner, now a faculty member at the University of California, San Francisco, is experimenting with building larger microtissues that include more cell types, and encoding more structural information into the cells so researchers can direct their orientation and construct asymmetric assemblies, such as the layers of cells in the skin. “We're trying to see how much further we can push the basic idea,” he says.

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