Figure 10.

High-power micrographs demonstrating the existence of the vascular orifices (arrows), probably from Thebesian veins or venous channels, on the endocardial surface of 3-day-old (A, B), 1-week-old (C, D), and 2-week-old (E, F) transmural post-MI scars that connect the subendocardial vascular network associated with surviving cardiac myocytes to the LV cavity. The representative micrographs are stained either with hematoxylin and eosin (A) or immunofluorescence (B–F). In all micrographs, asterisks denote the profiles of the vascular structures, including venous microvessels and sinusoids, whereas arrowheads expose the vascular channels linking endocardial orifices to subendocardial vessels. In immunofluorescence micrographs B, C, D, and F, the viable cardiac myocytes (red color) are visualized using double immunostaining with antibodies against either cardiac actin (B, D, and F) or cardiac MHC β-isoform (C) and laminin (green color). In immunofluorescence micrograph E, the viable cardiac myocytes (green color) are visualized using immunostaining with an anticardiac MHC β-isoform antibody, whereas vascular structures (red color) are revealed with the GS-IB₄ lectin staining. In all immunofluorescence micrographs, nuclei are counterstained with DAPI (blue color). Note, in micrographs A, B, and C, besides the subendocardial region, the surviving cardiac myocytes are also seen intramurally, extending deeper along the venous vascular structures, most likely Thebesian veins and venous sinusoids, which are directly linked to LV cavity. Scale bars are 200 µm (A), 50 µm (C), and 20 µm (B, D, E, and F). Abbreviations: MI, myocardial infarction; MHC, myosin heavy chain; LV, left ventricular; GS-IB₄, Griffonia Simplicifolia isolectin IB₄; DAPI, 4′,6-diamidino-2-phenylindole.