Pharmaceutical companies rely on various non-human model systems to test the efficacy and toxicity of drug candidates in development. However, these systems may not be predictive of drug behavior in humans. To better predict drug behavior in human trials, a synthetic model that more closely mimics ''in vivo'' drug response is desirable. Better ''in vitro'' predictions of drug toxicity and efficacy may lead to safer, more effective therapies.

One promising model under development is the introduction of genetic circuits to populations of cells to produce organoids. These synthetic systems are compositionally similar to organs and respond to external stimuli in a comparable manner. The formation and maintenance of these structures requires coordinated behavior between individual cells based on their local context. As a means to coordinating behavior, the 2013 MIT iGEM team is developing an exosome mediated cell-cell communication system for use in mammalian cells.

Our exosome communication system employs two complementary signaling strategies. We are engineering sender and receiver cell circuits for testing signals including miRNA, recombinases, DNA-binding proteins, RNA-binding proteins, and proteases. We are particularly excited about the possibility of multiplexed communication using an exosomally delivered Cas9-CRISPR system.

We believe this method can be employed as a generalizable platform for intercellular communication. In concert with other synthetic biology modules, this work may be used in the future for creating mammalian systems that perform distributed computing, undergo multistep differentiation, or form complex microstructures.