Immunohistochemical verification of kisspeptins and their receptor in human fetal organs during prenatal development

Kisspeptins (KPs) and their receptor (KISS1R) play an important role in many physiological processes in the body, such as sexual maturation, reproductive system functioning, placentation, insulin secretion, and vasoconstriction. The highest level of kisspeptins and their receptor is observed in the organs of hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes, both in the form of mRNA and peptide. Kisspeptins are found in various body tissues: spinal cord (Dun et al., 2003), pancreas (Song et al., 2014), esophagus (Kostakis et al., 2013), adrenal glands and secretory system organs (Wahab et al., 2015), and in malignancies (Lee and Welch, 1997). However, the localization and the role of kisspeptins and their receptor in organs during fetal development have not yet been studied. At the same time, ample published data regarding the localization of kisspeptins and their receptors in human organs and tissues are discrepant, which requires the development of a standard staining technique. The modified technique presented in this paper made it possible to identify and evaluate the expression of kisspeptins and their receptor in human fetal organs at different stages of development. Kisspeptins and their receptors were found in all organs and tissues examined by us, but the degree of reaction was different. The highest level was observed in the hypothalamus material in the 28–32-week period, and the lowest amount of the protein was detected in the uterine material at all stages. Maximum level of KISS1R was detected in the pituitary material in the 36–40-week period. A correlation between gestational age and the level of kisspeptins in the ovaries, uterus, and adrenal glands was found: a significant increase in the amount of protein was detected. A significant increase in the amount of the kisspeptin receptor in pituitary, ovary, and uterus material was shown.