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Myocardial interstitial Cajal-like cells (ICLC) and their nanostructural relationships with intercalated discs: shed vesicles as intermediates.

Mandache E, Popescu LM, Gherghiceanu M - J. Cell. Mol. Med. (2007 Sep-Oct)

Bottom Line: Typically, ICLC have several very long, moniliform, cytoplasmic processes which establish closed contacts with nerve fibres, as well as each other.In the last case, electron-dense repetitive nanostructures ('pillars') (35-40 nm high and 100-150 nm wide, similar to adhesion molecules) fasten the ICLC to the myocytes.All these features suggest a juxtacrine and/or paracrine intercellular mutual modulation of ICLC and cardiomyocytes in the microenvironment of ID, possibly monitoring the cardiac functions, particularly the electrical activity.

View Article: PubMed Central - PubMed

Affiliation: Victor Babeçs National Institute of Pathology, Bucharest, Romania.

ABSTRACT
Intercalated discs (ID) are complex junctional units that connect cardiac myocytes mechanically and electrochemically. However, there is limited information concerning the cardiomyocyte interaction with interstitial non-muscle cells. Our previous studies showed that myocardial interstitial Cajal-like cells (ICLC) are located in between cardiomyocytes, blood capillaries and nerve fibres. Typically, ICLC have several very long, moniliform, cytoplasmic processes which establish closed contacts with nerve fibres, as well as each other. We report here ultrastructural evidence concerning the relationships of ICLC processes with ID. The ICLC cytoplasmic prolongations (tens micrometers length) preferentially pass by or stop nearby the ID. Transmission electron microscopy emphasized three distinct connecting features between the tips of ICLC extensions and myocytes at the 'mouth' of ID: free or budding shed vesicles, exocytotic multi-vesicular bodies and direct contacts. In the last case, electron-dense repetitive nanostructures ('pillars') (35-40 nm high and 100-150 nm wide, similar to adhesion molecules) fasten the ICLC to the myocytes. All these features suggest a juxtacrine and/or paracrine intercellular mutual modulation of ICLC and cardiomyocytes in the microenvironment of ID, possibly monitoring the cardiac functions, particularly the electrical activity.

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Related in: MedlinePlus

A segmented ICLC extension shedding a vesicle (arrow) toward the intercalated disc (ID). The white-bordered inset shows two electron-dense particles with about a 50 nm diameter: one of them in a pocket of the ICLC process (arrow) and next to the plasma membrane of the myocyte (M2), the second in the cytoplasm of the myocyte (arrow-head). Another shed vesicle (arrow) can be seen in the black-bordered inset. Note the electron-dense nanostructures (double arrows) that connect the ICLC and the myocyte (M2). The distance in between the two plasma membranes at the level of attachments structures is about 35–40 nm, similar to adhesion complexes. Scale bar for insets = 0.1 μm.
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fig07: A segmented ICLC extension shedding a vesicle (arrow) toward the intercalated disc (ID). The white-bordered inset shows two electron-dense particles with about a 50 nm diameter: one of them in a pocket of the ICLC process (arrow) and next to the plasma membrane of the myocyte (M2), the second in the cytoplasm of the myocyte (arrow-head). Another shed vesicle (arrow) can be seen in the black-bordered inset. Note the electron-dense nanostructures (double arrows) that connect the ICLC and the myocyte (M2). The distance in between the two plasma membranes at the level of attachments structures is about 35–40 nm, similar to adhesion complexes. Scale bar for insets = 0.1 μm.

Mentions: We have not seen any direct contact between ICLC tips and the external limit of the ID, but the distance in between was ranging between 80 and 500 nm (272 ‘B1 32 nm) which suggests some kind of paracrine signalling. Endorsing this hypothesis we have also observed shed vesicles (118 ‘B1 16 nm average diameter, min = 98 nm, max = 177 nm) between ICLC fingers and cardiomyocytes, next to the ID (Figs. 5–7). Some of these vesicles bud from the ICLC cytoplasmic processes (Fig. 5) and budding could be the mechanism of their formations. We have also observed round, dense granules (∼50 nm diameter) placed either in contact with the ICLC plasma membrane, in the basal lamina thickness or in the cortical cytoplasm of the myocardocytes in the proximity of ID (Figs. 3 and 7).


Myocardial interstitial Cajal-like cells (ICLC) and their nanostructural relationships with intercalated discs: shed vesicles as intermediates.

Mandache E, Popescu LM, Gherghiceanu M - J. Cell. Mol. Med. (2007 Sep-Oct)

A segmented ICLC extension shedding a vesicle (arrow) toward the intercalated disc (ID). The white-bordered inset shows two electron-dense particles with about a 50 nm diameter: one of them in a pocket of the ICLC process (arrow) and next to the plasma membrane of the myocyte (M2), the second in the cytoplasm of the myocyte (arrow-head). Another shed vesicle (arrow) can be seen in the black-bordered inset. Note the electron-dense nanostructures (double arrows) that connect the ICLC and the myocyte (M2). The distance in between the two plasma membranes at the level of attachments structures is about 35–40 nm, similar to adhesion complexes. Scale bar for insets = 0.1 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4401282&req=5

fig07: A segmented ICLC extension shedding a vesicle (arrow) toward the intercalated disc (ID). The white-bordered inset shows two electron-dense particles with about a 50 nm diameter: one of them in a pocket of the ICLC process (arrow) and next to the plasma membrane of the myocyte (M2), the second in the cytoplasm of the myocyte (arrow-head). Another shed vesicle (arrow) can be seen in the black-bordered inset. Note the electron-dense nanostructures (double arrows) that connect the ICLC and the myocyte (M2). The distance in between the two plasma membranes at the level of attachments structures is about 35–40 nm, similar to adhesion complexes. Scale bar for insets = 0.1 μm.
Mentions: We have not seen any direct contact between ICLC tips and the external limit of the ID, but the distance in between was ranging between 80 and 500 nm (272 ‘B1 32 nm) which suggests some kind of paracrine signalling. Endorsing this hypothesis we have also observed shed vesicles (118 ‘B1 16 nm average diameter, min = 98 nm, max = 177 nm) between ICLC fingers and cardiomyocytes, next to the ID (Figs. 5–7). Some of these vesicles bud from the ICLC cytoplasmic processes (Fig. 5) and budding could be the mechanism of their formations. We have also observed round, dense granules (∼50 nm diameter) placed either in contact with the ICLC plasma membrane, in the basal lamina thickness or in the cortical cytoplasm of the myocardocytes in the proximity of ID (Figs. 3 and 7).

Bottom Line: Typically, ICLC have several very long, moniliform, cytoplasmic processes which establish closed contacts with nerve fibres, as well as each other.In the last case, electron-dense repetitive nanostructures ('pillars') (35-40 nm high and 100-150 nm wide, similar to adhesion molecules) fasten the ICLC to the myocytes.All these features suggest a juxtacrine and/or paracrine intercellular mutual modulation of ICLC and cardiomyocytes in the microenvironment of ID, possibly monitoring the cardiac functions, particularly the electrical activity.

View Article: PubMed Central - PubMed

Affiliation: Victor Babeçs National Institute of Pathology, Bucharest, Romania.

ABSTRACT
Intercalated discs (ID) are complex junctional units that connect cardiac myocytes mechanically and electrochemically. However, there is limited information concerning the cardiomyocyte interaction with interstitial non-muscle cells. Our previous studies showed that myocardial interstitial Cajal-like cells (ICLC) are located in between cardiomyocytes, blood capillaries and nerve fibres. Typically, ICLC have several very long, moniliform, cytoplasmic processes which establish closed contacts with nerve fibres, as well as each other. We report here ultrastructural evidence concerning the relationships of ICLC processes with ID. The ICLC cytoplasmic prolongations (tens micrometers length) preferentially pass by or stop nearby the ID. Transmission electron microscopy emphasized three distinct connecting features between the tips of ICLC extensions and myocytes at the 'mouth' of ID: free or budding shed vesicles, exocytotic multi-vesicular bodies and direct contacts. In the last case, electron-dense repetitive nanostructures ('pillars') (35-40 nm high and 100-150 nm wide, similar to adhesion molecules) fasten the ICLC to the myocytes. All these features suggest a juxtacrine and/or paracrine intercellular mutual modulation of ICLC and cardiomyocytes in the microenvironment of ID, possibly monitoring the cardiac functions, particularly the electrical activity.

Show MeSH
Related in: MedlinePlus