Telocytes in human isolated atrial amyloidosis: ultrastructural remodelling.
Bottom Line: EM showed that amyloid deposits, composed of characteristic 10-nm-thick filaments were strictly extra-cellular.Although, under light microscope some amyloid deposits seemed to be located within the cardiomyocyte cytoplasm, EM showed that these deposits are actually located in interstitial recesses.Moreover, EM revealed that telopodes, the long and slender processes of telocytes, usually surround the amyloid deposits limiting their spreading into the interstitium.
Affiliation: 'Victor Babeş' National Institute of Pathology, Bucharest, Romania. email@example.comShow MeSH
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Mentions: The amyloid fibrillar deposits were located in the interstitial areas, in close contact with either atrial cardiomyocytes or small blood vessels in some cases. EM showed that all these deposits had the same characteristic feature: about 8–12 nm thick, randomly arranged, non-branching filaments (Figs 3–12). The amyloid fibrils were in close contact with the peripheral lamina of atrial working cardiomyocytes (Fig. 3). They occurred exclusively in the extracellular space. The fibrils were concentrated in small sarcolemmal recesses (Fig. 4). When these invaginations were deeper, they could have been transversely sectioned, giving the false impression of intracellular inclusions (Fig. 5). These invaginations were sometimes placed near the intercellular junctions (Fig. 6). Inside these pockets, the amyloid fibrils displayed a random distribution. As a rule, all these invaginations, either in longitudinal or in cross section, were always bordered by the myocyte plasma membrane associated with caveolae and external lamina (Fig. 7). On the interstitial side, the peri-myocyte fibrillar deposits seemed to have a special association with the slender processes of telocytes, the telopodes, which have the tendency to wrap the fibrils (Fig. 8). This kind of fibril wrapping was either between telopodes and cardiomyocytes, or vessels (Fig. 9), or by a telopode only (Fig. 10). When the telopodes surrounded a mass of fibrils, the amyloid filaments were gathered as small bunches (Fig. 11). Some telopodes involved in this process displayed a honeycomb aspect with bunches of fibrils in their small meshes (Fig. 12).
Affiliation: 'Victor Babeş' National Institute of Pathology, Bucharest, Romania. firstname.lastname@example.org