Platelet mitochondrial transfer via extracellular vesicles modulates neutrophil phenotype and function

Platelet activation causes the release of extracellular vesicles, of which a small proportion contain respiratory competent mitochondria. Mitochondria are integral for energy production and in the regulation of apoptotic pathways, however the existence of extracellular mitochondria highlights a potential new role in intercellular communication. Indeed, mitochondrial transfer has gained significant research interest in recent years, highlighting mechanisms through which cellular function and metabolism may be augmented. To characterise changes in neutrophil function and phenotype that occur because of interactions with mitochondria-positive or mitochondria-negative platelet extracellular vesicles. Platelet extracellular vesicle subpopulations were separated based on mitochondrial content using cell sorting and subsequently incubated with isolated neutrophils. Alterations in surface receptor repertoire were analysed by flow cytometry, and functional characterisation performed by immunofluorescence, flow cytometry and Seahorse XF metabolic flux assays. In this work we demonstrate that platelet extracellular vesicles containing mitochondria interact with and are internalised by neutrophils, subsequently increasing their metabolic capacity. These interactions promote changes in neutrophil receptor repertoire, indicative of enhanced neutrophil activation, adhesion and migration pathways. The internalisation of platelet mitochondria renders neutrophils unable to subsequently engulf bacteria, demonstrating reduced phagocytic capacity, but enhances the formation of neutrophil extracellular traps, both alone and in the presence of additional stimuli. Our findings show that platelet mitochondria released in extracellular vesicles can be transferred into neutrophils, altering their metabolic function and activity. This research highlights an important role for platelet mitochondria as intercellular communicators and modulators of inflammatory and immune responses.