Telocytes in trachea and lungs

Abstract

We show the existence of a novel type of interstitial cell-telocytes (TC) in mouse trachea and lungs. We used cell cultures, vital stainings, as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and immunohistochemistry (IHC). Phase contrast microscopy on cultured cells showed cells with unequivocally characteristic morphology of typical TC (cells with telopodes-Tp). SEM revealed typical TC with two to three Tp-very long and branched cell prolongations. Tp consist of an alternation of thin segments (podomers) and thick segments (podoms). The latter accommodate mitochondria (as shown by Janus Green and MitoTracker), rough endoplasmic reticulum and caveolae. TEM showed characteristic podomers and podoms as well as close relationships with nerve endings and blood capillaries. IHC revealed positive expression of TC for c-kit, vimentin and CD34. In conclusion, this study shows the presence in trachea and lungs of a peculiar type of cells, which fulfils the criteria for TC.

Fig 1

Phase-contrast microscopy; TC in primary culture; mouse lung. A typical telocyte is depicted with three long and slender Tp. Tp characteristically present the alternation of thick segments—podoms (black arrows)—and thin segments-podomers (white arrows).

Fig 2

Phase-contrast microscopy; living TC in primary culture; vital staining with methylene blue; mouse lung. A typical TC with a pyramidal cell body and three long Tp. The alternation of podoms and podomers is characteristic for the Tp. Original magnification: 200×

Fig 3

Mouse lung; TC in culture; Giemsa staining. A typical TC with a pyramidal cell body and with three long Tp. The alternation of podoms and podomers is striking for the Tp. Dichotomic branching of Tp is obvious. Original magnification: 200×

Fig 4

Vital staining with Janus Green B; primary cell culture; mouse lung. A typical TC with two branched Tp. The vital staining shows accumulation of mitochondria within TC cell body and as well as the level of podoms. A long Tp, belonging to another TC is shown in the upper part of the figure, overpassing the cell body of the other TC.

Fig 5

Primary cell culture; mouse lung. Phase-contrast microscopy shows canonical TC with branched Tp. The uneven caliber (alternation of podoms—arrows—and podomers) of the Tp is observed. Original magnification: 100×

Fig 6

Fluorescence microscopy; MitoTracker Green staining; mouse lung; primary cell culture. The mitochondria of the same living cell from Figure 5 are revealed and mainly within cell body and podoms (arrows). Original magnification: 100×

Fig 7

Scanning electron microscopy of the lamina propria of mouse trachea. The tracheal epithelium was removed. The complex interstitial cell ‘landscape’ is obvious. Note a fibroblast with short prolongations and a dilated cell body. At least two silhouettes suggestive for highly branched TC are detectable. Scale bar: 10 μm.

Fig 8

(A) Mouse trachea; transmission electron microscopy of smooth muscle layer. Note, four muscle cells longitudinally cut and in between two fragments (one long, one short) of a Tp. It is to be mentioned the presence of thick myosin filaments in smooth muscle cells. DB: dense bodies; mito: mitochondria. (B) Higher magnification of a fragment from (A). Note, a smooth muscle cell with thick myosin filaments and basal lamina (bl); a fragment of a telopode, a podom containing element of ER. cav: caveolae; bl: basal lamina.

Fig 9

(A) Mouse lung; transmission electron microscopy; interstitial space of a intralobular bronchiole. Note the presence of Tp in close contacts with obliquely sectioned nerve endings. (B) Bonchoalveolar junction. Three fragments of a Tp are visible among local cellular population.

Fig 10

(A) Immunohistochemical reaction for c-kit and vimentin in lung tissue. Long TC silhouette is seen positive near small vein lumen. (B) Positive reaction for CD34 of TC between airway epithelium and blood vessel endothelium.