The kisspeptin effects on the thymic regulatory cell compositions (Th17, Treg, iNKT) <i>in vitro</i>

The peptide hormone kisspeptin, produced by neurons of the hypothalamus anterior zone, is a key regulator of the gonadostat formation and reproductive function, and has immunoregulatory activity. During pregnancy, kisspeptin is produced by the placenta, presents in the peripheral blood and affects on immune cells that express specific receptors for the hormone, including thymus cells. However, the kisspeptin effects on thymopoiesis during pregnancy have not been studied. The purpose of the work was to study the kisspeptin effect on the thymic regulatory cell composition in vitro. Thymocytes were cultured for 72 hours with kisspeptin at a concentration (9.6 pM) characterizing its maximum level in the peripheral blood during pregnancy, in the presence of CD3/CD28-activating particles and further assessed the regulatory cell composition and Ki-67 and Bcl-2 expression by flow cytometry. The percentage of T regulatory lymphocytes (Treg) was assessed as the percentage of CD4+CD25+FoxP3+ cells; T helper cells producing interleukin17 (Th17), as a percentage of CD4+IL-17A+RORγt+ cells; invariant T lymphocytes with natural killer functions(iNKT), as a percentage of CD3hiVa24Ja18+ cells in thymocyte culture. Dexamethasone (10-6M) was added to induce apoptosis. The effect of kisspeptin-primed thymic plasmacytoid dendritic cells (pDCs) on the regulatory cell composition (Th17, Treg, iNKT) in thymocyte culture was assessed. Thymic pDCs isolated by immunomagnetic separation were cultured for 24 hours with kisspeptin, and then intact autologous thymocytes were added in a ratio of 1:10 and cultured for another 72 hours. The thymocyte incubation of with kisspeptin did not affect the Tregs, iNKT and Th17 percentage in vitro, as well as the expression of Ki-67 and Bcl-2 in these cells. Under dexamethasone influence, the Bcl-2+Th17 percentage in thymocyte cultures with kisspeptin was increased. The Th17 percentage was increased in cultures of kisspeptin-primed pDCs with thymocytes, while the Treg and iNKT number did not change. It can be concluded that kisspeptin has regulatory effects on the Th17 percentage in thymocyte culture in vitro, mediating its effects by influencing thymic pDCs. And kisspeptin acted directly on thymocytes, increases the resistance of thymic Th17 to dexamethasone-induced apoptosis. The obtained results expand our understanding of the hormonal regulation of regulatory cell balance during pregnancy.