Three-Dimensional Architecture of Cardiomyocytes and Connective Tissue in Human Heart Revealed by Scanning Electron Microscopy
Scanning electron microscopy is a useful modality to directly observe the 3-dimensional structures of cells at high resolution. Scanning electron microscopy enables visualization of the surface features of cardiomyocytes after removal of the surrounding connective tissue1 and the connective tissue skeleton after removal of the nonfibrous elements.2 In addition, backscattered electron emission with heavy metal staining3 helps to provide high-quality images of the intracellular architecture of the cardiomyocyte.
In this study, we present the 3-dimensional structure of the human left ventricular myocardium from subjects without apparent cardiac abnormalities at the time of autopsy. Backscattered electron emission provides a high-contrast picture of the subsarcolemmal sarcomeres and intercalated discs as seen in longitudinally arranged cardiomyocytes (Figure 1A). The cardiomyocytes are seen to be branched and connected with the adjacent cells via intercalated discs. At higher magnification, in the sarcomeres, the A bands can be identified as broad bright zones, the I bands are seen as dark zones, and the Z bands are demonstrated as indistinct thin lines in the middle of I bands (Figure 1B).
After the removal of the nonfibrous elements, interstitial connective tissue surrounding the cardiomyocytes and small vessels can be clearly observed (Figure 2A). The perimysium, located around the bundle of cardiomyocytes, and the endomysium tether surrounding the individual cardiomyocytes are clearly demonstrated4 (Figure 2B and 2C). At high magnification, collagen fibers are identified as forming a complex network and providing the strength sufficient to support the 3-dimensional structure comprising cardiac muscle fibers and neighboring vascular tissues (Figure 2D).
- © 2010 American Heart Association, Inc.