Abstract: Genome editing technologies have significant potential to treat a variety of devastating human diseases and disorders. However, there are a number of challenges that genome editing therapies must overcome to reach their full promise. Specifically, there are many possible adverse consequences that are unique to genome editing tools, such as genome integrity, immune responses, and loss of therapeutic efficacy due to cell turnover, for which there are currently are no optimal systems for rigorous assessment. Moreover, these consequences are unique to human physiology, genome sequence, and immune systems, and therefore typical animal models are not completely informative. To address this unmet need, we have assembled a team of collaborative investigators that have developed advanced genome editing strategies and methods for engineering human microphysiological tissue systems that recapitulate human physiology and function, with an emphasis on skeletal and cardiac muscle. We will combine these technologies in this proposal to systemically evaluate tissue physiology, genomic alterations, tissue regeneration, and immune response in response to various genome editing strategies and delivery methods. Specifically, this will include comprehensive and unbiased mapping of unintended modifications to human genome sequences, including at on-target and off-target sites. We will also determine the role of resident tissue stem cells, cell turnover, and tissue injury and regeneration in the stability of genome editing. Finally, we can incorporate immune cells into these microphysiological tissues to understand the consequences of immunity to bacteria-derived genome editing components. Collectively, this proposal will develop a platform to systematically address the most significant challenges to realizing the transformative potential of genome editing therapies in human tissues.