Abstract
The existence of telocytes (TCs) has not yet been established in the pancreases of aquatic reptiles. Here, we report TCs in the exocrine pancreas of Pelodiscus sinensis using transmission electron microscope (TEM), immunohistochemistry (IHC), and immunofluorescence (IF) techniques. TCs surrounded the acini and ducts of the connective tissue of the exocrine pancreas and between lobules and gland cells. The cells were located preferably close to the blood vessels, interlobular ducts, and nerve fibers. Ultrastructurally, TCs exhibited small and large bodies with thick and thin portions, podoms, and podomers, and prolongations that form dichotomous branching with hetero-cellular and homo-cellular junctions. The podom (thick) portions showed caveolae, mitochondria, rough endoplasmic reticulum, and vesicles. The nucleus carries heterochromatin and is irregular in shape. The shape of TCs depends on the number of telopodes (Tps) bearing long, short, spindle, triangular, and “beads on a string” shapes with twisted, tortuous prolongations and ramifications. Shed extracellular vesicles and exosomes were found frequently released from projections and Tps within connective tissue in the vicinity of the acini and collagen fibers. IHC and IF results showed CD34+, α-SMA+, and vimentin+, long and triangle-shaped TCs, consistent with the TEM findings. The presence of shaded vesicles from TCs might implicate their possible role in immune surveillance, tissue regeneration as well as regulatory functions in the reptilian pancreas.
Highlights
Telocytes (TCs) are interstitial cells of mesenchymal origin, first reported by Popescu and Faussone-Pellegrini in 2005
The pancreatic tissue consists of glandular lobules composed of acinus, islets, and connective tissue separating these lobules
It is difficult to distinguish between telocytes and endothelial cells in IHC and IF, transmission electron microscope (TEM) is good for their identification
Summary
Telocytes (TCs) are interstitial cells of mesenchymal origin, first reported by Popescu and Faussone-Pellegrini in 2005. They were named interstitial Cajal-like cells (ICLCs) and interstitial cells of cajal (ICCs) based on their morphology, ultrastructural features, immunophenotype, and site of existence. ICLCs were renamed TCs [1,2,3,4] These are moniliform and long structured cells, that sometimes form convoluted trajectories. These features are different between TCs and other stromal cells such as fibroblast-like cells or fibrocytes [2,5]. TCs frequently establish homo-junctions (telopodes to telopodes), as well as hetero-junctions with other structures of neighboring cells (nerve fibers, collagen fibers), to perform numerous functions and to form three-dimensional (3D) networks [1,6,7,8,9,10]
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