Regulated Release of Small Extracellular Vesicles Directs Neutrophil Recruitment in Cutaneous Wound Healing

Normal cutaneous wound healing is a multicellular process that involves the release of small extracellular vesicles (sEVs) that coordinate intercellular communication by delivery of sEV payloads to recipient cells. We have recently shown how the proreparative activity of inflammatory cell sEVs, especially macrophage and neutrophil-derived sEVs, in the wound bed is dysregulated in impaired wound healing. In this study, we show that loss of Rab27A, a small GTPase that has a regulatory function in sEV secretion, reduces the release of neutrophil and macrophage-derived sEVs. Proteomic profiling of sEVs identified Rab27A-dependent protein payloads relevant in neutrophil activation, such as CD44, leukotriene A4 hydrolase, complement C5, and neutrophilic granule protein. We defined the activity of sEVs derived from Rab27A-knockout donors by demonstrating a delayed neutrophil recruitment in the initial injury response. The dysfunction of Rab27-knockout sEVs was linked to an increase in the release of CCL4, consistent with the sustained inflammation observed in vivo and reduced neutrophil migration in vitro. Together, these findings show how a specific regulator of sEV biogenesis can direct protein payloads and activities that mediate neutrophil trafficking in wound healing.