<p>A) A photograph depicting the fibrin sealant-based implant in a heart excised one year after implantation (left panel), a low magnification image of a Masson's trichrome stained heart section (center panel), and a low magnification image from an adjacent serial section showing Prussian blue iron stain (right panel) of SPIO-labeled cells within the implant. The right atrium (RA), right ventricle (RV), and aorta are depicted along with an outline of the implant (dotted line). Scale bars equal 500 µm. B) Higher magnification brightfield images from the boxed region in A) showing an unprocessed serial section demonstrating iron (brown) can be detected in the cells of the implant and the same Masson's trichrome and Prussian blue stained sections from A). Scale bars equal 50 µm. C) The same section as the left panel from B) immunostained for the presence of macrophages (MAC387 in green), DNA (DAPI in blue), and striated muscle (ACTN in red) (left panel). Adjacent serial sections were immunostained for cardiac troponin T (cTnT in red), DNA (DAPI in blue), and striated muscle (ACTN in green) (middle panel). The right panel shows an image of ACTN, cTnT, and DAPI staining in the right ventricle. Scale bars equal 50 µm. D) Serial sections from a different heart stained for Masson's trichrome (left panel), Prussian blue with pararosaniline (middle panel), and immuno-fluorescence from secondary antibodies detecting binding of cTnT and ACTN antibodies in addition to DAPI staining of DNA. Iron is abundant in implanted cells, but is not apparent in the epicardium or myocardium of the right ventricle. The location of SPIO-labeled cells corresponds to the location of ACTN positive (red), cTnT negative (green) cells. Scale bars equal 50 µm.</p
