SUMMARY Resolution in skin wound healing is coordinated by intercellular communication processes that include extracellular vesicles (EVs) containing biologically active protein and nucleic acid. While EV biogenesis has been studied in vitro, systematic approaches to identify their in vivo relevance are limited. Having established that the expression of TBC/RabGAPs controls EV biogenesis and ‘re-programs’ EV content to uncouple the pro-reparative activities of EVs in inflammation, we propose to use a genetic approach to target the secretory machinery implicated in EV biogenesis (i.e. Rabs 5, 11, and 27A) to determine how these targets of TBC/RabGAPs regulate the payload of EVs. We will determine how EVs, and changes in EVs, impact the resolution of inflammation, and gain insight into the role of EVs in wound healing. In Aim 1, we will use vesicle flow cytometry to define EV subsets, followed by adoptive transfer of EVs to determine their capacity to activate specific immune cell populations in diabetic and immunodeficient knockout mouse models that mediate cutaneous wound closure. Aim 2 will study specific Rabs to determine how these Rabs impact EV biogenesis and content. In addition, using the EVs formed in the altered Rab environment, we will establish the mechanism of action and effect of these EVs on the kinetics of resolution of specific immune responses. Together, these studies will establish the relevance of EVs as potential therapeutics and address the over-arching goal of systematically creating therapeutic EVs that are specifically optimized for specific phases of skin repair.

Narrative The proposed studies focus on small extracellular vesicles secreted by cells to regulate immune cells to accelerate the resolution of inflammation and promote skin repair. We hypothesize that a mechanistic understanding of how small extracellular vesicles are formed, and how their content and secretion is regulated, is critical for the optimization of therapeutic extracellular vesicles that can be deployed in each of the very different phases of wound repair.