Telocytes in the interstitium of human exocrine pancreas: ultrastructural evidence.

Objectives: Pancreatic interstitial cells are located among acini, ducts, nerves, and blood vessels. They are essential for pancreas development, physiology, and for oncogenic microenvironment. We identified cells with characteristic ultrastructural features of telocytes in pancreatic interstitium. Telocytes were initially described as interstitial Cajal-like cells, but it gradually became clear that they were a distinct novel cell type not directly related to canonical interstitial Cajal cells.

Methods: Serial ultrathin sections of human pancreatic tissue were studied by transmission electron microscopy. Computer analysis software was used to obtain 2-dimensional compositions from serial micrographs and to perform morphometry.

Results: Pancreatic telocytes appear as small-body cells with prolongations called telopodes. The ultrastructural features of telopodes are the following: (a) number: 1 to 3; (b) length: tens of micrometers; (c) moniliform aspect: with podoms (thicker portions) and podomers (thin segments, with a mean width of 60 nm, undetectable by light microscopy); (d) dichotomous branching forming a network; (e) establish homocellular and heterocellular junctions; (f) release of microvesicles/multivesicular bodies. Telopodes pass close to blood vessels, nerves, and pancreatic acinar cells and ducts.

Conclusions: Telocytes are present as distinct interstitial cells in the exocrine pancreatic stroma. They act as important players in intercellular signaling via stromal synapses and shed vesicle transfer.