Direct effect of kisspeptin on steroidogenesis, proliferation and apoptosis in Tan sheep ovarian granulosa cells

Kisspeptin, encoded by <i>Kiss1</i> gene, regulates reproduction via the hypothalamic-pituitary-gonadal axis. While kisspeptin treatment promotes follicular development in Tan sheep, its direct action on ovarian granulosa cells remains unclear. For this, we first detected the expression of <i>Kiss1</i> and its receptor <i>Kiss1r</i> in primary ovarian granulosa cells of Tan sheep. Second, the effect of kisspeptin on steroid hormone secretion, proliferation and apoptosis of ovarian granulosa cells was investigated. Third, the signaling pathway of kisspeptin regulating steroid hormone secretion was revealed by western bolting in ovarian granulosa cells. The results showed that the <i>Kiss1</i> and <i>Kiss1r</i> genes were present in ovarian granulosa cells of Tan-sheep, and 500 nM dose of kisspeptin significantly stimulated steroids hormone secretion (<i>P</i> < 0.05), and up-regulated <i>StAR</i>, <i>HSD17B</i>2, <i>CPY19A</i>1, <i>FSHR</i>, <i>LHR</i>, <i>ERβ</i>, <i>PGR</i> and p-ERK1/2 proteins expression (<i>P</i> < 0.05). Moreover, this treatment significantly promoted cell proliferation and increased the proportion of cells in S phase (<i>P</i> < 0.05), and significantly suppressed granulosa cell apoptosis (<i>P</i> < 0.05). Additionally, the stimulatory effects of kisspeptin on estradiol and progesterone secretion were blocked by inhibitors of the Mitogen-activated Protein Kinase (MAPK) signaling pathway (including PKA inhibitor, PLC inhibitor, PKC inhibitor, and Ca²⁺inhibitor). Western blot analysis confirmed that kisspeptin regulates steroid hormone secretion primarily through the MAPK-ERK signaling pathway. Our results demonstrate that kisspeptin can directly act on ovarian granulosa cells to promote steroidogenesis, proliferation, and inhibit apoptosis, providing a foundational basis for developing novel kisspeptin-mediated techniques to regulate reproduction in Tan sheep.