Introduction: The Kiss1/Kisspeptin/Kiss1r system is essential for puberty onset and reproductive system development, especially in the hypothalamus. Nevertheless, Kiss1 is expressed in other organs. Additionally, serum kisspeptin has been associated with puberty. However, studies on the developmental changes in serum kisspeptin levels and its main source are limited. Therefore, the aim of this study was to evaluate the developmental changes of serum kisspeptin and identify its main source.
Methods: ELISA was used to analyze serum kisspeptin levels at the onset, and mid-way of each different stage (days 4, 8, 14, 23, and 27, and during vaginal opening).Tissues (known to express Kiss1) from several organs were recovered at the same time points. The expression of Kiss1 mRNA in these tissues were compared with the pattern of serum kisspeptin levels. In addition, ovariectomy (OVX) was performed on day 14, half of the ovariectomized rats were treated with estradiol (E2), and changes in serum kisspeptin levels in OVX or OVX + E2 rats evaluated. To identify the main source of serum kisspeptin, the changes in hypothalamic Kiss1 expression were evaluated and compared to that of serum kisspeptin.
Results: Serum kisspeptin levels increased with increasing developmental stages till the pre-pubertal stage. Several organs expressed Kiss1 mRNA, with the expression pattern in ovaries being similar to that of serum kisspeptin levels. After OVX, serum kisspeptin levels decreased with or without E2 treatment. These changes were different from anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC) Kiss1 mRNA expression changes.
Conclusions: Ovarian Kiss1 may be main source of serum kisspeptin, which may double as a downstream marker of ovarian reproductive function development.
19 Sep 2019 - 21 Sep 2019