Abstract
Alongside the well-known central modulatory role, the Kisspeptin system, comprising Kiss1, its cleavage products (Kisspeptins), and Kisspeptin receptor (Kiss1R), was found to regulate gonadal functions in vertebrates; however, its functional role in the male gamete and its localization during maturation have been poorly understood. The present study analyzed Kisspeptin system in dog testis and spermatozoa recovered from different segments of the epididymis, with focus on Kiss1R on sperm surface alongside the maturation during epididymal transit, demonstrated by modification in sperm kinetic, morphology, and protamination. The proteins Kiss1 and Kiss1R were detected in dog testis. The receptor Kiss1R only was detected in total protein extracts from epididymis spermatozoa, whereas dot blot revealed Kiss1 immunoreactivity in the epidydimal fluid. An increase of the Kiss1R protein on sperm surface along the length of the epididymis, with spermatozoa in the tail showing plasma membrane integrity and Kiss1R protein (p < 0.05 vs. epididymis head and body) was observed by flow cytometry and further confirmed by epifluorescence microscopy and Western blot carried on sperm membrane preparations. In parallel, during the transit in the epididymis spermatozoa significantly modified their ability to move and the pattern of motility; a progressive increase in protaminization also occurred. In conclusion, Kisspeptin system was detected in dog testis and spermatozoa. Kiss1R trafficking toward plasma membrane along the length of the epididymis and Kiss1 in epididymal fluid suggested a new functional role of the Kisspeptin system in sperm maturation and storage.
Highlights
Several studies demonstrated the crucial role of Kisspeptins and their receptor Kiss1R in the regulation of the reproductive axis by stimulating hypothalamic gonadotrophinreleasing hormone (GnRH) release [1,2,3,4,5]
The Kisspeptin system is an evolutionarily conserved signaling system notably involved in the central control of reproduction, and expressed at periphery within gonads, gametes, and reproductive tracts in both sexes [20,21,22,23,24,25,26]
We preliminarily analyzed the presence of Kiss1 and Kiss1R in the dog testis and we evaluated the system in parallel to the functional maturation of sperm attributes and storage along the transit in the epididymis
Summary
Several studies demonstrated the crucial role of Kisspeptins and their receptor Kiss1R in the regulation of the reproductive axis by stimulating hypothalamic gonadotrophinreleasing hormone (GnRH) release [1,2,3,4,5]. The precursor Kiss is cleaved into shorter peptides (Kisspeptin (Kp)-54, Kp-13, Kp-14 and Kp-10)), all sharing the C-terminal end and all capable to activate Kiss1R [8,9]. Today, it is well-established that the Kisspeptin system plays a pivotal key role in several aspects of reproduction by the direct regulation of GnRH and by driving the onset of puberty, sex steroid feedback mechanisms [5,10,11], and regulating seasonal reproduction in domestic animals [12,13,14,15], Syrian hamster [16], amphibians [17,18], and some fish [19]. The present study aimed to verify the presence of Kisspeptin system in dog testis and spermatozoa recovered from different segments of the epididymis (head, body, and tail), in parallel with the evaluation of sperm quality parameters. The contribution of every single tract to the configuration of the Kisspeptin system in male mature gametes in the dog as a mammal model is provided
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
