Ordered Assembly of the Adhesive and Electrochemical Connections within Newly Formed Intercalated Disks in Primary Cultures of Adult Rat Cardiomyocytes

Figure 3

Ultrastructural analysis of new cardiomyocyte cell-cell contacts at 5-days post plating. At this timepoint, cell contacts form and develop rapidly, allowing the observation of both nascent (a, b, d) and more mature (c, e, f, g) contact sites. (a) Remodeling cardiomyocytes extend fingerlike projections (arrowheads) that interact with neighboring cells to form adhesive contacts (arrows) thereby electromechanically linking the two cells. (b, d) Higher magnifications of an adhesive domain indicated in (a) shows insertion of actin filaments into nascent adherens junctions (AJs) (arrows in (b)). Note the nascent (white arrowheads in (d)) and more mature (black arrowhead in (d)) desmosomal contacts in close proximity to the maturing AJ. (c) A mature adhesive domain again demonstrates desmosomal contacts (arrowheads) near a newly formed adherens junction (arrow). (e)–(g) More mature adhesive contacts demonstrate adherens junctions (arrows in (e)) at the insertion of the terminal actin filaments of newly formed myofibrils, along with closely associated desmosomal contacts (arrowhead in (f)) and gap junctions (arrowhead in (g)). Scale bars are 500 nm (a)–(f) and 100 nm (g).