Project Summary/Abstract Proper wound healing is critical following surgery and injury, while compromised healing is a factor in diseases such as diabetes, obesity, tobacco abuse, and malnutrition. As well, tissue restoration after healing is limited, such that most repair leads to scar formation and loss of function. With millions affected and billions in associated care costs yearly, impaired wound healing, chronic wounds and fibrosis-related diseases represent a critical health burden. Data reveals that the presence of reactive oxygen species (ROS), byproducts of aerobic metabolism containing oxygen that are highly reactive, are critical to wound healing outcomes. ROS are also necessary for cell signaling and play a role in host defense and injury signaling. But the current evidence is contradictory, suggesting both positive (required for repair and immune recruitment) and negative (promoting cell damage) roles for ROS. Furthermore, it is not clear whether wound healing and regeneration are separable processes. Our preliminary data suggests that there are different wound-specific and regenerative-specific ROS signaling pathways and demonstrates the usefulness of planarians to parse the roles of ROS in tissue repair. While all multicellular organisms possess wound responses and repair mechanisms, the signaling that promotes healing and regeneration versus scarring remains a mystery. This proposal’s long term goal is to understand how ROS signaling may be manipulated to regulate both wound healing and tissue repair, identifying new targets for treatment and refining current therapies for better patient outcomes. This proposal’s objective is to identify differences in ROS levels and signaling that switch injury-induced ROS responses from control of wound healing to tissue repair. We have two hypotheses: 1) that distinct ROS-initiated signaling pathways regulate wound healing versus tissue repair, and 2) that the level and timing of ROS present at the wound site determines whether wound healing or regrowth occurs. These will be tested with two specific aims: AIM 1) to identify wound-only versus regenerative-specific expression of ROS-mediated genes, detecting any epistatic interactions; and AIM 2) to test the effects of different ROS levels on regeneration (proliferation and tissue growth) and wound healing (actin-mediated reepithelization). In alignment with the AREA mechanism, this work is designed to be completed mainly by undergraduate students—in order to foster future independence and train them in common techniques (such as microsurgery, cloning, in situ hybridization, immunohistochemistry, and RNA interference). These studies will advance our understanding of impaired wound healing and fibrosis, and uncover fundamental principles of how ROS is utilized during repair.