Exercise for Cardiovascular Disease Prevention and Treatment From Molecular to Clinical, Part 1

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two basic types of mast cells. The first type is associated with loose connective tissue

of the adventitia of blood vessels (the so-called perivascular mast cells). The second

type is localized predominantly in the mucosa (mucosal mast cells), especially in the

respiratory and digestive systems [ 77 ]. Over the last decades, many scientists have

defined another resident population of mast cells: the cardiac mast cells. An increased

number of cardiac mast cells have been reported in different chronic or acute diseases

of the cardiovascular system, such as dilated cardiomyopathy, hypertension, chronic

cardiac volume overload, and myocardial infarction [ 78 ]. It is assumed that cardiac

mast cells probably participate in myocardial dysfunction and myocardial remodel-

ing, but the precise mechanisms are presently unknown.

Mast cells are easily identifiable in histological tissue sections (Fig. 8.7). They

are ovoid with a single spherical nucleus and many cytoplasmic granules. These

granules stain intensely and metachromatically (a characteristic change in the color

of the applied dye) in the presence of basic dyes, such as toluidine blue or thionine.

At the ultrastructural level, the cytoplasmic granules of mast cells are diverse. Some

are electron-dense, and others form scrolls or crystals [ 79 ]. In recent decades,

monoclonal antibodies have been commonly used for immunohistochemical identi-

fication of mast cells in tissue sections. Anti-tryptase antibodies represent the “gold

standard” for identifying mast cells in human tissues. Tryptase, a trypsin-like serine

protease, is specific for mast cells. Other markers enriched in human cardiac mast

cells include IgE receptor, CD117 (c-kit), p24 antigen, Pgp-1 homing receptor

(CD44), and ICAM-1 antigen (CD54). However, these can also be expressed by

Fig. 8.7 A human heart visualized by light microscopy. Ovoid-shaped mast cells (arrows, anti-
CD117 antibody, brown color) are observed between adipocytes in the epicardium.
Diaminobenzidine was used as a chromogen (Orig. Magn. 400×)

8 The Non-cardiomyocyte Cells of the Heart. Their Possible Roles...