A transmission electron microscopy investigation suggests that telocytes, skeletal muscles, myoblasts, and stem cells in common carp (Cyprinus carpio) respond to salinity challenges

Abstract

Background: Telocytes are modified interstitial cells that communicate with other types of cells, including stem cells. Stemness properties render them more susceptible to environmental conditions. The current morphological investigation examined the reactions of telocytes to salt stress in relation to stem cells and myoblasts. The common carp are subjected to salinity levels of 0.2, 6, and 10 ppt. The gill samples were preserved and prepared for TEM.

Results: The present study observed that telocytes undergo morphological change and exhibit enhanced secretory activities in response to changes in salinity. TEM can identify typical telocytes. This research gives evidence for the communication of telocytes with stem cells, myoblasts, and skeletal muscles. Telocytes surround stem cells. Telopodes made planar contact with the cell membrane of the stem cell. Telocytes and their telopodes surrounded the skeletal myoblast. These findings show that telocytes may act as nurse cells for skeletal stem cells and myoblasts, which undergo fibrillogenesis. Not only telocytes undergo morphological alternations, but also skeletal muscles become hypertrophied, which receive telocyte secretory vesicles in intercellular compartments.

Conclusion: In conclusion, the activation of telocytes is what causes stress adaptation. They might act as important players in intercellular communication between cells. It is also possible that reciprocal interaction occurs between telocytes and other cells to adapt to changing environmental conditions.

Keywords: Cyprinus carpio; Myoblasts; Salinity; Skeletal muscles; Stem cells; Telocytes.

Fig. 1

Telocytes relation with skeletal myoblast. Colored ultra-thin sections in gill arches treated samples with a 6 ppt level of salinity. A-D: Telocytes surrounded the myoblast which contained ill-organized myofibrils (My). Telopodes were connected to nerve fibers and formed multipoint contact with skeletal muscles. Note nerve fiber (arrow), secretory vesicles (V), and multivesicular body (arrowhead). Telocytes established contact with different types of stromal, epithelial, stem cells (green color), and skeletal muscles. Large number of secretory vesicles were excreted close to the muscular fibers in samples treated with a 6 ppt concentration of salinity

Fig. 2

Telocytes relation with stem cells. Colored ultra-thin sections in gill arches treated samples with 10 ppt (A, B) level of salinity A, B: several telocytes surrounding stem cells (S), which are characterized by a high nuclear-cytoplasmic ratio and contain mitochondria (m). Telopodes established a planar contact with stem cells (dashed line). Telopodes formed an extensive network (double arrowheads). They secreted vesicles (V) and a multivesicular body (arrowhead). Several telopodes interdigitate with the stem cells (arrows). note secretory vesicles attached to stem cells (double arrow). Some telopodes were thickened (asterisk)

Fig. 3

Figure 2 original transmission electron microscopy beside the figure’s representative drawing

Fig. 4

Figure 1’s original transmission electron microscopy beside the figure’s representative drawing

Fig. 5

Skeletal muscle fibers undergo hypertrophy in response to salinity. Colored ultra-thin sections in gill arches control (A) and treated samples with 6 ppt (A-C),10 ppt (D, E) level of salinity. A, B: in control samples, telopode (T) adjacent to skeletal muscle fiber which received telocytes secretory vesicles. Note the secretory vesicles (arrows) located in intracellular compartments (C) in the muscle cell. Note extracellular secretory vesicles (V). C, D, E: In 6ppt treated samples, telocytes (blue color) formed a network between muscle cells (red colored). Telocytes established multi-point contact (double arrows) with skeletal muscle fiber (m). Telopode formed a direct contact with the nerve fiber (n). Note epithelium (ep). F, G: In 10 ppt treated samples, telocytes established direct contact (double arrowheads) with skeletal muscle fibers which increased in diameter (m). Note telopodes organized an extensive network and acquired a corrugated appearance (arrows). Note blood vessels (bv) and secretory vesicles (V)

Fig. 6

Figure 5’s original transmission electron microscopy beside the figure’s representative drawing

Fig. 7

An illustration shows the relations of telocytes with skeletal muscles, myoblasts, and stem cells and the effect of salinity on telocytes and skeletal muscles. Telocytes have telopodes which consisted of podoms and podomeres. Note multivesicular body (MV), the secretory vesicles (V) were phagocytosed in intracellular compartments (c). Telocytes formed multiple-point contact with skeletal muscle, planer contact was formed between telocytes and stem cells. Note interdigitated cytoplasmic projections or cytonemes of telocytes projected to stem cells. In high salinity levels, telocytes increased the secretory activities, telopodes acquired a corrugated appearance and skeletal muscles undergo hypertrophy