Non-invasive mapping of systemic neutrophil dynamics upon cardiovascular injury.

Neutrophils play a complex role during onset of tissue injury and subsequent resolution and healing. To assess neutrophil dynamics upon cardiovascular injury, here we develop a non-invasive, background-free approach for specific mapping of neutrophil dynamics by whole-body magnetic resonance imaging using targeted multimodal fluorine-loaded nanotracers engineered with binding peptides specifically directed against murine or human neutrophils. Intravenous tracer application before injury allowed non-invasive three-dimensional visualization of neutrophils within their different hematopoietic niches over the entire body and subsequent monitoring of their egress into affected tissues. Stimulated murine and human neutrophils exhibited enhanced labeling due to upregulation of their target receptors, which could be exploited as an in vivo readout for their activation state in both sterile and nonsterile cardiovascular inflammation. This non-invasive approach will allow us to identify hidden origins of bacterial or sterile inflammation in patients and also to unravel cardiovascular disease states on the verge of severe aggravation due to enhanced neutrophil infiltration or activation.