European Journal of Histochemistry 2011; volume 55:e14 KISS1 and KISS1R expression in the human and rat carotid body and superior cervical ganglion A. Porzionato,1 G. Fenu,2 M. Rucinski,3 V. Macchi,1 A. Montella,2 L.K. Malendowicz,3 R. De Caro1 1Section of Anatomy, Department of Human Anatomy and Physiology, University of Padova, Italy; 2Department of Biomedical Sciences, University of Sassari, Sassari, Italy; 3Department of Histology and Embryology, Poznan University of Medical Sciences, Poznan, Poland Abstract KISS1 and its receptor, KISS1R, have both been found to be expressed in central nervous system, but few data are present in the litera- ture about their distribution in peripheral nerv- ous structures. Thus, the aim of the present study was to investigate, through immunohisto- chemistry, the expression and distribution of KISS1 and KISS1R in the rat and human carotid bodies and superior cervical ganglia, also with particular reference to the different cellular populations. Materials consisted of carotid bod- ies and superior cervical ganglia were obtained at autopsy from 10 adult subjects and sampled from 10 adult Sprague-Dawley rats. Immunohistochemistry revealed diffuse expres- sion of KISS1 and KISS1R in type I cells of both human and rat carotid bodies, whereas type II cells were negative. In both human and rat superior cervical ganglia positive anti-KISS1 and -KISS1R immunostainings were also selec- tively found in ganglion cells, satellite cells being negative. Endothelial cells also showed moderate immunostaining for both KISS1 and KISS1R. The expression of both kisspeptins and kisspeptin receptors in glomic type I cells and sympathetic ganglion cells supports a modulato- ry role of KISS1 on peripheral chemoreception and sympathetic function. Moreover, local changes in blood flow have been considered to be involved in carotid body chemoreceptor dis- charge and kisspeptins and kisspeptin receptors have also been found in the endothelial cells. As a consequence, a possible role of kisspeptins in the regulation of carotid body blood flow and, indirectly, in chemoreceptor discharge may also be hypothesized. Introduction The KISS1 gene was originally identified through a differential expression approach showing up regulation of its expression in tumor cells which had lost their potential to metastize.1-3 It encodes for a 145 amino acid precursor, which can be cleaved into a 54 amino acid protein, originally called metastin, or shorter 14, 13 and 10 amino acid peptides, which share a common C-terminal amidation site. With the term of kisspeptins are collec- tively named all the peptides cleaved from the precursor hormone. The larger protein shows some variability among species whereas the C- terminal 10 amino acid sequence is well con- served.1,4-6 The kisspeptin receptor, now called KISS1R in humans and Kiss1r in rodents,7 was initial- ly discovered in rats in 1999 as an orphan G protein-coupled membrane receptor named GPR54,8 in 2001 kisspeptins being identified as its natural ligands.4-6,9 Its gene shares mod- est homology with the gene coding for the galanin receptor 2, although kisspeptins do not bind the above galanin receptor.8 Kisspeptins play a crucial role in the control of puberty onset and reproductive function. Apart from central nervous system, KISS1 and KISS1R have both been found to be widely expressed in many other tissues such as the pituitary, gonads, placenta, pancreas, liver, intestines and vessels.1,5,6,10,11 As it concerns the peripheral nervous system, both KISS1 and KISS1R have recently been found to be expressed in rat dorsal root ganglion.12 To the best of our knowledge, there are no data regarding expression of kisspeptin and kisspeptin receptor in the carotid body and sympathetic ganglia. The carotid body is the main peripheral arte- rial chemoreceptor, inducing increases in ven- tilatory volume and frequency in response to hypoxia, hypercapnia, or reduction of blood pH. It is organized in lobules of cells belonging to two different populations: type I cells, with roundish shape and higher dimensions, and type II cells, with fusiform shape and located at the edges of the clusters. Type I cells represent the real chemoreceptor elements. In response to the various stimuli they release many differ- ent neurotransmitters and neuromodulators,13- 17 which mainly act on the glosso-pharyngeal afferent fibers arising from the petrosal gan- glion. However, substances released from type I cells may also act on other components of the carotid body, such as type I cells themselves (through autocrine and paracrin mecha- nisms), type II cells, vessels, and connective cells. Type II cells show astrocytic markers and play a supportive role, but it has recently been observed that if exposed to prolonged hypoxia Correspondence: Prof. Raffaele De Caro, Section of Anatomy, Department of Human Anatomy and Physiology, University of Padua, Via A. Gabelli 65, 35121 Padova, Italy. Tel. +39.049.8272327 - Fax: +39.049.8272328. E-mail: rdecaro@unipd.it Key words: Kisspeptin, GPR54, carotid body, supe- rior cervical ganglion. Conflict of interest: the authors report no con- flicts of interest. Acknowledgement: the authors are grateful to Mrs. Gloria Sarasin and Anna Rambaldo for their skillful technical assistance. Received for publication: 23 January 2011. Accepted for publication: 22 March 2011. This work is licensed under a Creative Commons Attribution 3.0 License (by-nc 3.0). ©Copyright A. Porzionato et al., 2011 Licensee PAGEPress, Italy European Journal of Histochemistry 2011; 55:e14 doi:10.4081/ejh.2011.e14 they may also behave as stem cells precursor for type I cells.18 The carotid body also shows parasympathetic and sympathetic innervation, the latter mainly from the superior cervical ganglion. The aim of the present study was therefore to investigate, through immunohistochemistry and real-time RT-PCR, the expression and dis- tribution of KISS1 and KISS1R in the rat and human carotid body and superior cervical gan- glia, also with particular reference to the dif- ferent cellular populations. Materials and Methods Tissue sampling and preparation Materials consisted of carotid bodies and superior cervical ganglia obtained at autopsy from 10 adult subjects [6 males, 4 females; mean age 46 years, standard deviation (SD)±3.6], clinically negative for chronic pul- monary or cardiovascular diseases, and sam- pled from 10 adult Sprague-Dawley rats. Autopsies were performed between 24 and 30 h after death. Sampling from rats was performed soon after sacrifice. Right carotid bifurcations and superior cervical ganglia from humans and rats were fixed in Bouin solution and embed- ded in paraffin wax. [page 78] [European Journal of Histochemistry 2011; 55:e14]