Telocytes (TCs) are a special type of interstitial cell with characteristic
cellular processes that are described in many organs.
The current study aimed to investigate TCs in seminal
vesicles of the Soay ram responding to melatonin treatment
during the nonbreeding season by conventional immunohistochemical
stains, and to detect the ultrastructural and
morphometrical changes of TCs. TCs in the control group
showed a broad range of staining affinity and also reacted
positively to CD117/c-kit, CD34, desmin, S-100 protein, and
progesterone and estrogen receptors alpha, while after melatonin
treatment a strong reaction against these 6 antibodies
was recorded. Electron microscopically, TCs in the control
group were characterized by a small cell body with distinct
long cytoplasmic extensions called telopodes (Tps). Tps had
alternation of the thin segment (podomers) and dilated segments
(podoms), in which the latter accommodate mitochondria,
rough endoplasmic reticulum and caveolae. TCs
and their Tps were interconnected by homo- and heterocellular
junctions and form a wide network to communicate between
different cell types. Tps showed close contact with
immune cells, progenitor stem cells, smooth muscle cells and other interstitial cells. Melatonin caused a significant increase
in the number of TCs, length of Tps, and number and
diameter of secretory vesicles. Also, the melatonin-treated
group showed exaggerated secretory activity in the form of
a massive release of secretory vesicles from Tps. Moreover,
Tps showed an increase in their contact with blood and lymphatic
capillaries, nerve endings and Schwann cells. In addition,
the shedding of secretory structures (exosomes, ectosomes,
and multivesicular bodies) was greater from Tps,
which were involved in paracrine signaling in the melatonintreated
group. The length and ramifications of Tps together
with the intercellular junctions and the releasing of shed vesicles
or exosomes assumed an essential role of TCs in intercellular
signaling and coordination. On the basis of their distribution
and morphology, we investigated whether the different
locations of TCs could be associated with different
roles.