Fig. 4. Foam cell formation in the early chronic phase of hemorrhagic MI is accompanied by highly localized deposition of ceroid lipopigment in iron-rich MI zones.

Panels show the histological and confocal microscopy evaluations of the 8-week-old hemorrhagic MI. Serial paraffin sections of the infarcted subendocardial myocardium at 8 weeks post-MI were stained with elastin-modified Masson’s trichrome stain (EMT), H&E, and Prussian Blue (PB). Dotted line boxes/rectangles (images in the second row) are shown as zoomed-in regions (images in the third row). Consistent with Fig. 2, note the extensive co-localization of fat (foam cells) with persistent iron deposits. Evidence of ceroid was determined based on autofluorescence in sections stained with PB by confocal microscopy and is shown in panel PB-1 at an excitation wavelength of 405 nm and emission wavelength of 428–496 nm. Panel PB-2 represents a differential interference contrast (DIC) for PB-1. Panel PB-3 shows an overlay of PB-1 autofluorescence and DIC (PB-2). Note the extensive co-localization of ceroid with iron deposits and foam cells. Scale bar equals 100 and 50 µm (zoomed-in images). The number of samples per timepoint/animal group used is depicted in Supplementary Fig. 1.