Editors' ChoiceIMMUNITY

Imaging the Beating Heart

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Science Translational Medicine  06 Mar 2013:
Vol. 5, Issue 175, pp. 175ec41
DOI: 10.1126/scitranslmed.3006041

Immune cells invade the ischemic heart tissue after a myocardial infarction (MI). This inflammatory response can be detrimental and can extend infarct size, but little is known about how the immune system reacts after a heart attack. Jung and colleagues used intravital fluorescence microscopy to better understand immune cell traffic after MI in mice.

Using a miniature endoscope inserted through the ribs, the authors were able to image this aspect of cardiac physiology in anesthetized animals. Jung et al. investigated the kinetics of immune cell trafficking into infarcted heart tissue after inducing MI in these animals via arterial ligation. In contrast to traditional histology, which has suggested that neutrophils are the dominant cell type recruited during ischemia, fluorescence microscopy revealed a rapid and robust infiltration of a monocyte population that expresses the chemokine receptor CX3CR1. These cells were evident within 5 min after MI, migrating to the heart first from the circulating blood, but then from a splenic reservoir. This implies that both local and systemic signals may be important in this recruitment.

The response to MI is probably a complex process involving some immune mechanisms that are protective, but others that may be maladaptive, leading to arrhythmia or heart failure. Advanced in vivo imaging such as that described by Jung et al. is critical for the characterization of the operative immune pathways after MI, but this technology can also be applied to other forms of heart disease. Because mouse models also allow for the manipulation of these mechanisms, the technical challenges to miniaturize this imaging system will reap great dividends. Additional studies will undoubtedly focus on distinguishing good healing from bad healing after MI, allowing the identification of novel therapeutic strategies for heart disease.

K. Jung et al., Endoscopic time-lapse imaging of immune cells in infarcted mouse hearts. Circ. Res., published online 7 February 2013 (10.1161/CIRCRESAHA.111.300484). [Abstract]

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