Assessment of cell infiltration in myocardial infarction: A dose-dependent study using micrometer-sized iron oxide particles

Myocardial infarction (MI) is a leading cause of death and disabilities. Inflammatory cells play a vital role in the process of postinfarction remodeling and repair. Inflammatory cell infiltration into the infarct site can be monitored using T 2*-weighted MRI following an intravenous administration of iron oxide particles. In this study, various doses of micrometer-sized iron oxide particles (1.1-14.5 μg Fe/g body weight) were injected into the mouse blood stream before a surgical induction of MI. Cardiac MRIs were performed at 3, 7, 14, and 21 days postinfarction to monitor the signal attenuation at the infarct site. A dose-dependent phenomenon of signal attenuation was observed at the infarct site, with a higher dose leading to a darker signal. The study suggests an optimal temporal window for monitoring iron oxide particles-labeled inflammatory cell infiltration to the infarct site using MRI. The dose-dependent signal attenuation also indicates an optimal iron oxide dose of approximately 9.1-14.5 μg Fe/g body weight. A lower dose cannot differentiate the signal attenuation, whereas a higher dose would cause significant artifacts. This iron oxide-enhanced MRI technique can potentially be used to monitor cell migration and infiltration at the pathological site or to confirm any cellular response following some specific treatment strategies.